Newly discovered exoplanet may be best candidate in search for signs of life

The newly discovered super-Earth LHS 1140b orbits in the habitable zone around a faint red dwarf star named LHS 1140, in the constellation of Cetus (The Sea Monster). Red dwarfs are much smaller and cooler than the Sun and, although LHS 1140b is ten times closer to its star than the Earth is to the Sun, it only receives about half as much sunlight from its star as the Earth and lies in the middle of the habitable zone. The orbit is seen almost edge-on from Earth and as the exoplanet passes in front of the star once per orbit it blocks a little of its light every 25 days.

This artist's impression shows the exoplanet LHS 1140b, which orbits a red dwarf star 40 light-years from Earth 
and may be the new holder of the title 'best place to look for signs of life beyond the Solar System'
[Credit: ESO/spaceengine.org]

"This is the most exciting exoplanet I've seen in the past decade," said lead author Jason Dittmann of the Harvard-Smithsonian Center for Astrophysics (Cambridge, USA). "We could hardly hope for a better target to perform one of the biggest quests in science—searching for evidence of life beyond Earth."

"The present conditions of the red dwarf are particularly favourable—LHS 1140 spins more slowly and emits less high-energy radiation than other similar low-mass stars," explains team member Nicola Astudillo-Defru from Geneva Observatory, Switzerland.

For life as we know it to exist, a planet must have liquid surface water and retain an atmosphere. When red dwarf stars are young, they are known to emit radiation that can be damaging for the atmospheres of the planets that orbit them. In this case, the planet's large size means that a magma ocean could have existed on its surface for millions of years. This seething ocean of lava could feed steam into the atmosphere long after the star has calmed to its current, steady glow, replenishing the planet with water.

Using ESO's HARPS instrument at La Silla, and other telescopes around the world, an international team of astronomers 
discovered this super-Earth orbiting in the habitable zone around the faint star LHS 1140. This world is a little larger 
and much more massive than the Earth and has likely retained most of its atmosphere
 [Credit: M. Weiss/CfA]

The discovery was initially made with the MEarth facility, which detected the first telltale, characteristic dips in light as the exoplanet passed in front of the star. ESO's HARPS instrument, the High Accuracy Radial velocity Planet Searcher, then made crucial follow-up observations which confirmed the presence of the super-Earth. HARPS also helped pin down the orbital period and allowed the exoplanet's mass and density to be deduced.

The astronomers estimate the age of the planet to be at least five billion years. They also deduced that it has a diameter 1.4 times larger than the Earth—almost 18 000 kilometres. But with a mass around seven times greater than the Earth, and hence a much higher density, it implies that the exoplanet is probably made of rock with a dense iron core.

This super-Earth may be the best candidate yet for future observations to study and characterise its atmosphere, if one exists. Two of the European members of the team, Xavier Delfosse and Xavier Bonfils both at the CNRS and IPAG in Grenoble, France, conclude: "The LHS 1140 system might prove to be an even more important target for the future characterisation of planets in the habitable zone than Proxima b or TRAPPIST-1. This has been a remarkable year for exoplanet discoveries!".

In particular, observations coming up soon with the NASA/ESA Hubble Space Telescope will be able to assess exactly how much high-energy radiation is showered upon LHS 1140b, so that its capacity to support life can be further constrained.

Further into the future—when new telescopes like ESO's Extremely Large Telescope are operating—it is likely that we will be able to make detailed observations of the atmospheres of exoplanets, and LHS 1140b is an exceptional candidate for such studies.

This research was presented in the journal Nature.

Source: ESO [April 19, 2017]

byUnknown

in Astrobiology, Astronomy, Universe

April 19, 2017

Newly discovered exoplanet may be best candidate in search for signs of life

The newly discovered super-Earth LHS 1140b orbits in the habitable zone around a faint red dwarf star named LHS 1140, in the constellation o...

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Supermassive black holes found in two tiny galaxies

Three years ago, a University of Utah-led team discovered that an ultra-compact dwarf galaxy contained a supermassive black hole, then the smallest known galaxy to harbor such a giant black hole. The findings suggested that the dwarfs were likely tiny leftovers of larger galaxies that were stripped of their outer layers after colliding into other, larger galaxies.

U astronomers and colleagues have found two ultra-compact dwarf galaxies, VUCD3 and M59cO, with supermassive 
black holes. The findings suggest that the dwarfs are likely tiny leftovers of larger galaxies that were stripped 
of their outer layers after colliding into other, larger galaxies M87 and M59, respectively 
[Credit: NASA/Space Telescope Science Institute]

Now, the same group of U astronomers and colleagues have found two more ultra-compact dwarf galaxies with supermassive black holes. Together, the three examples suggest that black holes lurk at the center of most of these objects, potentially doubling the number of supermassive black holes known in the universe. The black holes make up a high percentage of the compact galaxies' total mass, supporting the theory that the dwarfs are remnants of massive galaxies that were ripped apart by larger galaxies.

"We still don't fully understand how galaxies form and evolve over time. These objects can tell us how galaxies merge and collide," says Chris Ahn, doctoral candidate in the Department of Physics & Astronomy, and lead author of the international study that published in The Astrophysical Journal. "Maybe a fraction of the centers of all galaxies are actually these compact galaxies stripped of their outer parts."

Measuring galaxies

The authors measured two ultra-compact dwarf galaxies, named VUCD3 and M59cO, that lie far beyond the spiral arms of our Milky Way, orbiting massive galaxies in the Virgo galaxy cluster. They detected a supermassive black hole in both galaxies; VUCD3's black hole has a mass equivalent to 4.4 million suns, making up about 13 percent of the galaxy's total mass, and M59cO's black hole has a mass of 5.8 million suns, making up about 18 percent of its total mass.

By comparison, the monstrous black hole at the center of the Milky Way has a mass of 4 million suns, but makes up less than .01 percent of the galaxy's total mass.

"It's pretty amazing when you really think about it. These ultra-compact dwarfs are around 0.1 percent the size of the Milky Way, yet they host supermassive black holes that are bigger than the black hole at the center of our own galaxy," marvels Ahn.

To calculate the ultra-compact dwarf galaxies' mass, the astronomers measured the movement of the stars using the Gemini North telescope located on Mauna Kea volcano in Hawaii. The astronomers have to correct for the distortions caused by Earth's atmosphere. They shot a laser into the sky to make a fake little star, and moved a mirror around hundreds of times a second to undo the distortion. They then applied the technique to the ultra-compact dwarf galaxies, which are so small that the corrections are necessary to measure the motions inside the object. The technique, known as adaptive optics, brings the once blurry galaxy into focus.

They also analyzed images from the Hubble Space Telescope to measure the distribution of the stars in each galaxy, and created a computer simulation that best fit their observations.

They found that the motion of the stars at the center of the galaxies moved much faster than those on the outside, a classic signature of a black hole. VUCD3 and M59cO are the second and third ultra-compact dwarf galaxies found to contain a supermassive black hole, suggesting that all such dwarfs may harbor similarly massive light-sucking objects.

Ultra-compact dwarf galaxy mysteries

Astronomers discovered ultra-compact dwarf galaxies in the late 1990s. The objects are made up of hundreds of millions of stars densely packed together on an average of 100 light years across. Scientists took measurements to see what was happening inside the galaxies, and something didn't add up; the ultra-compact dwarf galaxies had more mass than their stars alone could account for. Senior author Anil Seth, assistant professor in the Department of Physics & Astronomy at the U, led the 2014 study that found the first ultra-compact dwarf galaxy with a supermassive black hole. The two U-led studies make a strong case that supermassive black holes at the center of the galaxies are responsible for the extra mass.

The astronomers measured the movement of the stars using the Gemini North telescope located on Mauna Kea volcano
 in Hawaii. They applied a technique known as adaptive optics to the ultra-compact dwarf galaxies to correct 
for distortions caused by the Earth's atmosphere [Credit: Gemini Observatory/AURA]

An alternate theory of the dwarfs is that they are just really massive star clusters -- groups of a hundred thousand stars born at the same time. The largest star cluster in the Milky Way is three million stars, and ultra-compact dwarf galaxies are 10 to 100 times bigger than that. "The question was, 'Is that because they form bigger star clusters with the same process? Or are they different in some way?' This work shows that they are different," Seth continues.

"It's obvious in retrospect, because the center of a regular galaxy looks almost exactly like these objects, but that wasn't what most people thought they were. I wasn't convinced that we were going to find a black hole when I took the observations," says Seth. "This is a cool example of scientific discovery and how quickly you can reorient our understanding of the universe."

Black holes and the formation of galaxies

Black holes are areas with such strong gravity that not even light can escape. They form when stars collapse, leaving behind a black hole with dense mass that exerts gravitational force on the objects around it. Supermassive black holes have a mass of more than 1 million suns, and are thought to be at the center of all big galaxies.

One explanation for the supermassive black hole inside the ultra-compact dwarf galaxies is that the galaxies were once made up of billions of stars. The authors believe that the dwarfs were "swallowed up" and ripped apart by the gravity of much larger galaxies. The ultra-compact dwarf black hole is the remnant of its formerly massive size. The findings change the way that astronomers can piece together how galaxies form and evolve over time.

"We know that galaxies merge and combine all the time -- that's how galaxies evolve. Our Milky Way is eating up galaxies as we speak," says Seth. "Our general picture of how galaxies form is that little galaxies merge to form big galaxies. But we have a really incomplete picture of that. The ultra-compact dwarf galaxies provide us a longer timeline to be able to look at what's happened in the past."

Source: University of Utah [April 17, 2017]

byUnknown

in Astronomy, Universe

April 17, 2017

Supermassive black holes found in two tiny galaxies

Three years ago, a University of Utah-led team discovered that an ultra-compact dwarf galaxy contained a supermassive black hole, then the s...

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Researchers provide new insight into dark matter halos

Research from the University of Pennsylvania could shed light on the distribution of one of the most mysterious substances in the universe.

An image of a simulated galaxy cluster showing evidence for a boundary, or "edge" 
[Credit: Surhud More, Benedikt Diemer and Andre Kravtsov, 
Astrophysical Journal 2015]

In the 1970s, scientists noticed something strange about the motion of galaxies. All the matter at the edge of spiral galaxies was rotating just as fast as material in the inner part of the galaxy. But according to the laws of gravity, objects on the outskirts should be moving slower.

The explanation: A form of matter called dark matter that does not directly interact with light.

Many scientists now believe that more than 80 percent of the matter of the universe is locked away in mysterious, as yet undetected, particles of dark matter, which affect everything from how objects move within a galaxy to how galaxies and galaxy clusters clump together in the first place.

This dark matter extends far beyond the reach of the furthest stars in the galaxy, forming what scientists call a dark matter halo. While stars within the galaxy all rotate in a neat, organized disk, these dark matter particles are like a swarm of bees, moving chaotically in random directions, which keeps them puffed up to balance the inward pull of gravity.

Bhuvnesh Jain, a physics professor in Penn's School of Arts & Sciences, and postdoc Eric Baxter are conducting research that could give new insights into the structure of these halos.

The researchers wanted to investigate whether these dark matter halos have an edge or boundary.

"People have generally imagined a pretty smooth transition from the matter bound to the galaxy to the matter between galaxies, which is also gravitationally attracted to the galaxies and clusters," Jain said. "But theoretically, using computer simulations a few years ago, researchers at the University of Chicago showed that for galaxy clusters a sharp boundary is expected, providing a distinct transition that we should be able to see through a careful analysis of the data."

Scientists believe that this region, or "edge" is due to the "splashback effect."

"You have this big dark matter halo sitting there," Baxter said, "and it's been accreting matter gravitationally over its entire history. As that matter gets pulled in, it gets faster and faster. When it finally falls into the halo, it turns around and starts to orbit. That turnaround is what people have started calling splashback, because stuff is splashing back in some sense."

As the matter "splashes back," it slows down. Because this effect is happening in many different directions, it leads to a buildup of matter right at the edge of the halo and a steep fall-off in the amount of matter right outside of that position. This is what the Penn researchers explored in the data.

A two-dimensional comparison of two models for the density profile of a halo. 
Both of these models come from fitting to data in SDSS. Models with a splashback 
feature (an "edge") fit the data better than models that don't have an edge.  
New measurements provide evidence that this "edge" exists
[Credit: University of Pennsylvania]

Using a galaxy survey called the Sloan Digital Sky Survey, or SDSS, Baxter and Jain looked at the distribution of galaxies around clusters. They formed a team of experts at the University of Chicago and other institutions around the world to examine thousands of galaxy clusters. Using statistical tools to do a joint analysis of several million galaxies around them, they found a drop at the edge of the cluster. Baxter and collaborator Chihway Chang at the University of Chicago led a paper reporting the findings, accepted for publication in the Astrophysical Journal.

In addition to seeing this edge when they looked at galaxy distribution, the researchers also saw evidence of it in the form of galaxy colors.

When a galaxy is full of gas and forming many big, hot stars, the heat causes it to appear blue when scientists takes images of it.

"But those big stars live very short lives," Baxter said. "They blow up. What you're left with are these smaller, older stars that live for long periods of time, and those are red."

When scientists look at galaxies within clusters, they appear red because they aren't forming stars.

"Previous studies have shown that there are interactions inside of the cluster that can cause galaxies to stop forming stars," Baxter said. "You could imagine for instance that a galaxy falls into a cluster, and the gas from the galaxy gets stripped off by gas within the cluster. After losing its gas, the galaxy will be unable to form many stars."

Because of this, scientists expect that galaxies that have spent more time orbiting through a cluster will appear red, while galaxies that are just starting to fall in will appear blue.

The researchers noticed a sudden shift in the colors of galaxies right at the boundary, providing them with more evidence that dark matter halos have an edge.

"It was really interesting and surprising to see this sharp change in colors," Jain said, "because the change of galaxy colors is a very slow and complex process."

The researchers are working on another paper using a deeper survey of over a hundred million galaxies called the Dark Energy Survey, or DES.

Both the SDSS and the DES make massive maps of the sky using a huge camera that Jain said isn't very fundamentally different from the cameras in smartphones but bigger and more precise and costing millions of dollars to build.

In the DES, when the camera opens, it takes an exposure of a couple minutes, and then moves to a different part of the sky. This process is repeated during the course of several years using different filters to allow scientists to get a survey in multiple colors.

The DES allows the researchers to do expanded measurements, pushing to higher distances.

Instead of measuring the distribution of galaxies, the researchers are using an astrophysical phenomenon called gravitational lensing to probe the dark matter halos. In gravitational lensing, light coming to an observer bends as matter exerts gravitational force on it.

The researchers can analyze images of the sky to see how clusters stretch images of the galaxies behind them.

"Light is going to bend if there's mass," Baxter said. "By measuring these deflections we can measure the mass directly which is cool because most of the mass is dark matter which we can't see so it's kind of a unique way to probe the dark matter."

In terms of fundamental understanding of the universe, Baxter said, dark matter is one of the biggest mysteries there is right now.

"You look in the sky, even with the biggest optical telescopes, and you see nothing beyond the light of the galaxies," Jain said. "There's just this dark matter."

The researchers hope that their research will contribute to a better understanding of the mysterious substance that makes up about 80 percent of matter in the universe. If they can mark the edge of a dark matter halo, it would allow them to test things like Einstein's theory of gravity and the nature of dark matter.

"It's just a new way of looking at clusters," Jain said. "Once you find the boundary you can study both the standard physics of how galaxies interact with the cluster and the possible unknown physics of what the nature of dark matter and gravity is."

Author: Ali Sundermier | Source: University of Pennsylvania [April 17, 2017]

byUnknown

in Astronomy, Astrophysics, Universe

April 17, 2017

Researchers provide new insight into dark matter halos

Research from the University of Pennsylvania could shed light on the distribution of one of the most mysterious substances in the universe. ...

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Hubble sees starbursts in Virgo

Although galaxy formation and evolution are still far from being fully understood, the conditions we see within certain galaxies -- such as so-called starburst galaxies -- can tell us a lot about how they have evolved over time. Starburst galaxies contain a region (or many regions) where stars are forming at such a breakneck rate that the galaxy is eating up its gas supply faster than it can be replenished!

NGC 4536 [Credit: ESA/Hubble & NASA]

NGC 4536 is such a galaxy, captured here in beautiful detail by the Hubble's Wide Field Camera 3 (WFC3). Located roughly 50 million light-years away in the constellation of Virgo (The Virgin), it is a hub of extreme star formation. There are several different factors that can lead to such an ideal environment in which stars can form at such a rapid rate. Crucially, there has to be a sufficiently massive supply of gas. This might be acquired in a number of ways -- for example by passing very close to another galaxy, in a full-blown galactic collision, or as a result of some event that forces lots of gas into a relatively small space.

Star formation leaves a few tell-tale fingerprints, so astronomers can tell where stars have been born. We know that starburst regions are rich in gas. Young stars in these extreme environments often live fast and die young, burning extremely hot and exhausting their gas supplies fairly quickly. These stars also emit huge amounts of intense ultraviolet light, which blasts the electrons off any atoms of hydrogen lurking nearby (a process called ionization), leaving behind often colorful clouds of ionized hydrogen (known in astronomer-speak as HII regions).

Source: NASA/Goddard Space Flight Center [April 14, 2017]

byUnknown

in Astronomy, Universe

April 14, 2017

Hubble sees starbursts in Virgo

Although galaxy formation and evolution are still far from being fully understood, the conditions we see within certain galaxies -- such as ...

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The lifetimes of massive star-forming regions

Astronomers can roughly estimate how long it takes for a new star to form: it is the time it takes for material in a gas cloud to collapse in free-fall, and is set by the mass, the size of the cloud, and gravity. Although an approximation, this scenario of quick, dynamic star formation is consistent with many observations, especially of sources where new material can flow into the cloud, perhaps along filaments, to sustain steady activity. But this simple picture might not apply in the largest systems with star clusters and high-mass stars. Rather than a quick collapse, the process there might be inhibited by pressure, turbulence, or other activities that slow it down.

An image of a region with both star-forming cores (seen in the red) and starless clumps (the dark regions). Astronomers 
have combined statistical studies of these infrared data with submillimeter images to estimate the typical age of a massive 
star forming clump as about one million years. The red data are from Herschel 70 micron images, the green and blue
 are from Spitzer IRAC images at 8 and 4.5 microns [Credit: Battersby et al.]

CfA astronomer Cara Battersby and two colleagues studied the formation, early evolution, and lifetimes of high-mass star-forming regions and their earliest evolutionary phases in dense, molecular regions. These clumps have densities of gas as high as ten million molecules per cubic centimeter (tens of thousands of times higher than typical in gas clouds); the dust associated with this gas blocks the external starlight, leaving the material very cold, only a few tens of degrees above absolute zero. The usual method for identifying these clumps is with submillimeter telescopes, which take images of the sky; automated algorithms can then process the images to identify and characterize cold clumps. The problem is that even a quiescent clump can contain subregions of activity that are not spotted with the relatively poor spatial resolutions of the submillimeter telescopes used to assemble catalogs of these regions.

Rather than rely on the submillimeter images of the entire clumps, the astronomers examined each of the multiple, individual pixels in each clump image and compared the results with data from infrared and far infrared. These infrared images sample hotter material, including that from small embedded sources that may have been overpowered in the larger image. The infrared signals the presence of star formation activity in the clump, and also characterizes the dust temperatures (which are slightly higher when such activity is present). The authors anchor their timeframe to sources called methanol masers, found in star forming regions, which last for about 35,000 years. These masers are seen in many of the dense clumps, and reasonable estimates of their properties constrain the ages of the clumps in which they are located. The statistics from all the submillimeter and infrared clumps then provides an estimate of the typical values of a clump lifetime. The astronomers find that clumps without any embedded stars last between about 0.2 and 1.7 million years, while those with stars last only about half that time. The times, in the star formation case, span a range from about 0.4 - 2.4 free-fall times, in good agreement with the models. The results also demonstrate that most high density gas is found in clumps lacking a high-mass star (however, there could be small, low-mass stars present).

The study is published in The Astrophysical Journal.

Source: Harvard-Smithsonian Center for Astrophysics [April 14, 2017]

byUnknown

in Astronomy, Astrophysics, Universe

April 14, 2017

The lifetimes of massive star-forming regions

Astronomers can roughly estimate how long it takes for a new star to form: it is the time it takes for material in a gas cloud to collapse i...

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NASA missions provide new insights into 'ocean worlds' in our solar system

Two veteran NASA missions are providing new details about icy, ocean-bearing moons of Jupiter and Saturn, further heightening the scientific interest of these and other "ocean worlds" in our solar system and beyond. The findings are presented in papers published Thursday by researchers with NASA's Cassini mission to Saturn and Hubble Space Telescope.

This illustration shows Cassini diving through the Enceladus plume in 2015. New ocean world discoveries from 
Cassini and Hubble will help inform future exploration and the broader search for life beyond Earth 
[Credit: NASA/JPL-Caltech]

In the papers, Cassini scientists announce that a form of chemical energy that life can feed on appears to exist on Saturn's moon Enceladus, and Hubble researchers report additional evidence of plumes erupting from Jupiter's moon Europa.

"This is the closest we've come, so far, to identifying a place with some of the ingredients needed for a habitable environment," said Thomas Zurbuchen, associate administrator for NASA's Science Mission Directorate at Headquarters in Washington. "These results demonstrate the interconnected nature of NASA's science missions that are getting us closer to answering whether we are indeed alone or not."

The paper from researchers with the Cassini mission, published in the journal Science, indicates hydrogen gas, which could potentially provide a chemical energy source for life, is pouring into the subsurface ocean of Enceladus from hydrothermal activity on the seafloor.

The presence of ample hydrogen in the moon's ocean means that microbes -- if any exist there -- could use it to obtain energy by combining the hydrogen with carbon dioxide dissolved in the water. This chemical reaction, known as "methanogenesis" because it produces methane as a byproduct, is at the root of the tree of life on Earth, and could even have been critical to the origin of life on our planet.

Life as we know it requires three primary ingredients: liquid water; a source of energy for metabolism; and the right chemical ingredients, primarily carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. With this finding, Cassini has shown that Enceladus -- a small, icy moon a billion miles farther from the sun than Earth -- has nearly all of these ingredients for habitability. Cassini has not yet shown phosphorus and sulfur are present in the ocean, but scientists suspect them to be, since the rocky core of Enceladus is thought to be chemically similar to meteorites that contain the two elements.

"Confirmation that the chemical energy for life exists within the ocean of a small moon of Saturn is an important milestone in our search for habitable worlds beyond Earth," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California.

The Cassini spacecraft detected the hydrogen in the plume of gas and icy material spraying from Enceladus during its last, and deepest, dive through the plume on Oct. 28, 2015. Cassini also sampled the plume's composition during flybys earlier in the mission. From these observations scientists have determined that nearly 98 percent of the gas in the plume is water, about 1 percent is hydrogen and the rest is a mixture of other molecules including carbon dioxide, methane and ammonia.

The measurement was made using Cassini's Ion and Neutral Mass Spectrometer (INMS) instrument, which sniffs gases to determine their composition. INMS was designed to sample the upper atmosphere of Saturn's moon Titan. After Cassini's surprising discovery of a towering plume of icy spray in 2005, emanating from hot cracks near the south pole, scientists turned its detectors toward the small moon.

This graphic illustrates how Cassini scientists think water interacts with rock at the bottom 
of the ocean of Saturn's icy moon Enceladus, producing hydrogen gas 
[Credit: NASA/JPL-Caltech]

Cassini wasn't designed to detect signs of life in the Enceladus plume -- indeed, scientists didn't know the plume existed until after the spacecraft arrived at Saturn.

"Although we can't detect life, we've found that there's a food source there for it. It would be like a candy store for microbes," said Hunter Waite, lead author of the Cassini study.

The new findings are an independent line of evidence that hydrothermal activity is taking place in the Enceladus ocean. Previous results, published in March 2015, suggested hot water is interacting with rock beneath the sea; the new findings support that conclusion and add that the rock appears to be reacting chemically to produce the hydrogen.

The paper detailing new Hubble Space Telescope findings, published in The Astrophysical Journal Letters, reports on observations of Europa from 2016 in which a probable plume of material was seen erupting from the moon's surface at the same location where Hubble saw evidence of a plume in 2014. These images bolster evidence that the Europa plumes could be a real phenomenon, flaring up intermittently in the same region on the moon's surface.

These composite images show a suspected plume of material erupting two years apart from the same location 
on Jupiter's icy moon Europa. Both plumes, photographed in UV light by Hubble, were seen in silhouette 
as the moon passed in front of Jupiter [Credit: NASA/ESA/STScI/USGS]

The newly imaged plume rises about 62 miles (100 kilometers) above Europa's surface, while the one observed in 2014 was estimated to be about 30 miles (50 kilometers) high. Both correspond to the location of an unusually warm region that contains features that appear to be cracks in the moon's icy crust, seen in the late 1990s by NASA's Galileo spacecraft. Researchers speculate that, like Enceladus, this could be evidence of water erupting from the moon's interior.

"The plumes on Enceladus are associated with hotter regions, so after Hubble imaged this new plume-like feature on Europa, we looked at that location on the Galileo thermal map. We discovered that Europa's plume candidate is sitting right on the thermal anomaly," said William Sparks of the Space Telescope Science Institute in Baltimore. Sparks led the Hubble plume studies in both 2014 and 2016.

The researchers say if the plumes and the warm spot are linked, it could mean water being vented from beneath the moon's icy crust is warming the surrounding surface. Another idea is that water ejected by the plume falls onto the surface as a fine mist, changing the structure of the surface grains and allowing them to retain heat longer than the surrounding landscape.

For both the 2014 and 2016 observations, the team used Hubble's Space Telescope Imaging Spectrograph (STIS) to spot the plumes in ultraviolet light. As Europa passes in front of Jupiter, any atmospheric features around the edge of the moon block some of Jupiter's light, allowing STIS to see the features in silhouette. Sparks and his team are continuing to use Hubble to monitor Europa for additional examples of plume candidates and hope to determine the frequency with which they appear.

The green oval highlights the plumes Hubble observed on Europa. The area also corresponds to a warm 
region on Europa's surface. The map is based on observations by the Galileo spacecraft 
[Credit: NASA/ESA/STScI/USGS]

NASA's future exploration of ocean worlds is enabled by Hubble's monitoring of Europa's putative plume activity and Cassini's long-term investigation of the Enceladus plume. In particular, both investigations are laying the groundwork for NASA's Europa Clipper mission, which is planned for launch in the 2020s.

"If there are plumes on Europa, as we now strongly suspect, with the Europa Clipper we will be ready for them," said Jim Green, Director of Planetary Science, at NASA Headquarters.

Hubble's identification of a site which appears to have persistent, intermittent plume activity provides a tempting target for the Europa mission to investigate with its powerful suite of science instruments. In addition, some of Sparks' co-authors on the Hubble Europa studies are preparing a powerful ultraviolet camera to fly on Europa Clipper that will make similar measurements to Hubble's, but from thousands of times closer. And several members of the Cassini INMS team are developing an exquisitely sensitive, next-generation version of their instrument for flight on Europa Clipper.

For more information on ocean worlds in our solar system and beyond, visit:

https://www.nasa.gov/specials/ocean-worlds

Source: NASA/Jet Propulsion Laboratory [April 13, 2017]

byUnknown

in Astrobiology, Astronomy, Space Exploration, Universe

April 13, 2017

NASA missions provide new insights into 'ocean worlds' in our solar system

Two veteran NASA missions are providing new details about icy, ocean-bearing moons of Jupiter and Saturn, further heightening the scientific...

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ALMA investigates 'DeeDee,' a distant, dim member of our solar system

Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have revealed extraordinary details about a recently discovered far-flung member of our solar system, the planetary body 2014 UZ224, more informally known as DeeDee.

Artist concept of the planetary body 2014 UZ224, more informally known as DeeDee. ALMA was able to observe the faint
 millimeter-wavelength "glow" emitted by the object, confirming it is roughly 635 kilometers across. At this size, DeeDee 
should have enough mass to be spherical, the criteria necessary for astronomers to consider it a dwarf planet, 
though it has yet to receive that official designation [Credit: Alexandra Angelich (NRAO/AUI/NSF)]

At about three times the current distance of Pluto from the Sun, DeeDee is the second most distant known trans-Neptunian object (TNO) with a confirmed orbit, surpassed only by the dwarf planet Eris. Astronomers estimate that there are tens-of-thousands of these icy bodies in the outer solar system beyond the orbit of Neptune.

The new ALMA data reveal, for the first time, that DeeDee is roughly 635 kilometers across, or about two-thirds the diameter of the dwarf planet Ceres, the largest member of our asteroid belt. At this size, DeeDee should have enough mass to be spherical, the criteria necessary for astronomers to consider it a dwarf planet, though it has yet to receive that official designation.

"Far beyond Pluto is a region surprisingly rich with planetary bodies. Some are quite small but others have sizes to rival Pluto, and could possibly be much larger," said David Gerdes, a scientist with the University of Michigan and lead author on a paper appearing in the Astrophysical Journal Letters. "Because these objects are so distant and dim, it's incredibly difficult to even detect them, let alone study them in any detail. ALMA, however, has unique capabilities that enabled us to learn exciting details about these distant worlds."

Currently, DeeDee is about 92 astronomical units (AU) from the Sun. An astronomical unit is the average distance from Earth to the Sun, or about 150 million kilometers. At this tremendous distance, it takes DeeDee more than 1,100 years to complete one orbit. Light from DeeDee takes nearly 13 hours to reach Earth.

ALMA image of the faint millimeter-wavelength "glow" from the planetary body 2014 UZ224, more informally known as
 DeeDee. At three times the distance of Pluto from the sun, DeeDee is the second most distant known TNO 
with a confirmed orbit in our solar system [Credit: ALMA (ESO/NAOJ/NRAO)]

Gerdes and his team announced the discovery of DeeDee in the fall of 2016. They found it using the 4-meter Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile as part of ongoing observations for the Dark Energy Survey, an optical survey of about 12 percent of the sky that seeks to understand the as-yet mysterious force that is accelerating the expansion of the universe.

The Dark Energy Survey produces vast troves of astronomical images, which give astronomers the opportunity to also search for distant solar system objects. The initial search, which includes nearly 15,000 images, identified more than 1.1 billion candidate objects. The vast majority of these turned out to be background stars and even more distant galaxies. A small fraction, however, were observed to move slowly across the sky over successive observations, the telltale sign of a TNO.

One such object was identified on 12 separate images. The astronomers informally dubbed it DeeDee, which is short for Distant Dwarf.

The optical data from the Blanco telescope enabled the astronomers to measure DeeDee's distance and orbital properties, but they were unable to determine its size or other physical characteristics. It was possible that DeeDee was a relatively small member of our solar system, yet reflective enough to be detected from Earth. Or, it could be uncommonly large and dark, reflecting only a tiny portion of the feeble sunlight that reaches it; both scenarios would produce identical optical data.

Orbits of objects in our solar system, showing the current location of the planetary body 'DeeDee' 
[Credit: Alexandra Angelich (NRAO/AUI/NSF)]

Since ALMA observes the cold, dark universe, it is able to detect the heat -- in the form of millimeter-wavelength light -- emitted naturally by cold objects in space. The heat signature from a distant solar system object would be directly proportional to its size.

"We calculated that this object would be incredibly cold, only about 30 degrees Kelvin, just a little above absolute zero," said Gerdes.

While the reflected visible light from DeeDee is only about as bright as a candle seen halfway the distance to the moon, ALMA was able to quickly home in on the planetary body's heat signature and measure its brightness in millimeter-wavelength light.

This allowed astronomers to determine that it reflects only about 13 percent of the sunlight that hits it. That is about the same reflectivity of the dry dirt found on a baseball infield.

By comparing these ALMA observations to the earlier optical data, the astronomers had the information necessary to calculate the object's size. "ALMA picked it up fairly easily," said Gerdes. "We were then able to resolve the ambiguity we had with the optical data alone."

Objects like DeeDee are cosmic leftovers from the formation of the solar system. Their orbits and physical properties reveal important details about the formation of planets, including Earth.

This discovery is also exciting because it shows that it is possible to detect very distant, slowly moving objects in our own solar system. The researchers note that these same techniques could be used to detect the hypothesized "Planet Nine" that may reside far beyond DeeDee and Eris.

"There are still new worlds to discover in our own cosmic backyard," concludes Gerdes. "The solar system is a rich and complicated place."

Source: National Radio Astronomy Observatory [April 13, 2017]

byUnknown

in Astronomy, Universe

April 13, 2017

ALMA investigates 'DeeDee,' a distant, dim member of our solar system

Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have revealed extraordinary details about a recently discovered f...

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Collisions generate gas in debris disks

Many young stars, as well as more middle-aged stars like our sun, have "debris disks" -- like the Oort Cloud in our own solar system -- that are believed to be remnants of the system's formation. Recently, radio observations have detected gas within a number of such discs, but it was not clear why the gas was there. There are two major hypotheses: either the gas is primordial gas from the original gas cloud that formed the star, or it originates from collisions between objects in the disk.

Artist's impression of gas generation from the collision between objects in a debris disk [Credit: RIKEN]

In search of a solution to this problem, a team from the RIKEN Star and Planet Formation Laboratory decided to look at emissions of carbon, which are important as they can provide clues to the origin of the gas. Normally, carbon will exist mostly in a molecular form, as carbon monoxide. Ultraviolet light from the central star will "dissociate" the atoms, creating free atomic carbon, but normally a chemical reaction -- mediated by hydrogen -- recombines the carbon into CO. However, if there is no hydrogen, then the reaction does not take place and the carbon remains in its atomic state.

Aya Higuchi, the first author of the paper, published in Astrophysical Journal Letters, was able to use the ten-meter Atacama Submillimeter Telescope Experiment (ASTE) in Chile to examine the atomic carbon line from two young star systems -- 49 Ceti and Beta Pictoris -- that are known to have debris disks. They then compared this from data on CO taken by the Atacama Large Millimeter/submillimeter Array (ALMA), an array of telescopes in the same facility. "We were surprised," she says, "to find atomic carbon in the disk, the first time this observation has been made at sub-millimeter wavelength. But more so, we were surprised at how much there was. It was about as common as the carbon monoxide."

The implication, at least for these two star systems, is that there is very little hydrogen to drive the carbon back into CO. Because hydrogen makes up most of the gas in protoplanetary clouds, this hints that the gas is not primordial, but rather is generated from some process taking place in the debris disk. Gas has been found in other debris disks, but is not found in all. Higuchi says, "If we can perform similar measurements on other young stars, it will help to clarify the origin of the gas in debris disk. Our data here suggests that the gas is secondary."

Looking to the future, she continues, "This work will also help to understand how a protoplanetary disk evolves into a debris disks by distinguishing the origin of the gas in the disks."

Source: RIKEN [April 13, 2017]

byUnknown

in Astronomy, Universe

April 13, 2017

Collisions generate gas in debris disks

Many young stars, as well as more middle-aged stars like our sun, have "debris disks" -- like the Oort Cloud in our own solar syst...

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Earth sized 'Tatooine' planets could be habitable

With two suns in its sky, Luke Skywalker's home planet Tatooine in "Star Wars" looks like a parched, sandy desert world. In real life, thanks to observatories such as NASA's Kepler space telescope, we know that two-star systems can indeed support planets, although planets discovered so far around double-star systems are large and gaseous. Scientists wondered: If an Earth-size planet were orbiting two suns, could it support life?

This artist's concept shows a hypothetical planet covered in water around the binary star system of Kepler-35A and B 
[Credit: NASA/JPL-Caltech]

It turns out, such a planet could be quite hospitable if located at the right distance from its two stars, and wouldn't necessarily even have deserts. In a particular range of distances from two sun-like host stars, a planet covered in water would remain habitable and retain its water for a long time, according to a new study in the journal Nature Communications.

"This means that double-star systems of the type studied here are excellent candidates to host habitable planets, despite the large variations in the amount of starlight hypothetical planets in such a system would receive," said Max Popp, associate research scholar at Princeton University in New Jersey, and the Max Planck Institute of Meteorology in Hamburg, Germany.

Popp and Siegfried Eggl, a Caltech postdoctoral scholar at NASA's Jet Propulsion Laboratory, Pasadena, California, created a model for a planet in the Kepler 35 system. In reality, the stellar pair Kepler 35A and B host a planet called Kepler 35b, a giant planet about eight times the size of Earth, with an orbit of 131.5 Earth days. For their study, researchers neglected the gravitational influence of this planet and added a hypothetical water-covered, Earth-size planet around the Kepler 35 AB stars. They examined how this planet's climate would behave as it orbited the host stars with periods between 341 and 380 days.

"Our research is motivated by the fact that searching for potentially habitable planets requires a lot of effort, so it is good to know in advance where to look," Eggl said. "We show that it's worth targeting double-star systems."

In exoplanet research, scientists speak of a region called the "habitable zone," the range of distances around a star where a terrestrial planet is most likely to have liquid water on its surface. In this case, because two stars are orbiting each other, the habitable zone depends on the distance from the center of mass that both stars are orbiting. To make things even more complicated, a planet around two stars would not travel in a circle; instead, its orbit would wobble through the gravitational interaction with the two stars.

Popp and Eggl found that on the far edge of the habitable zone in the Kepler 35 double-star system, the hypothetical water-covered planet would have a lot of variation in its surface temperatures. Because such a cold planet would have only a small amount of water vapor in its atmosphere, global average surface temperatures would swing up and down by as much as 3.6 degrees Fahrenheit (2 degrees Celsius) in the course of a year.

"This is analogous to how, on Earth, in arid climates like deserts, we experience huge temperature variations from day to night," Eggl said. "The amount of water in the air makes a big difference."

But, closer to the stars, near the inner edge of the habitable zone, the global average surface temperatures on the same planet stay almost constant. That is because more water vapor would be able to persist in the atmosphere of the hypothetical planet and act as a buffer to keep surface conditions comfortable.

As with single-star systems, a planet beyond the outer edge of the habitable zone of its two suns would eventually end up in a so-called "snowball" state, completely covered with ice. Closer than the inner edge of the habitable zone, an atmosphere would insulate the planet too much, creating a runaway greenhouse effect and turning the planet into a Venus-like world inhospitable to life as we know it.

Another feature of the study's climate model is that, compared to Earth, a water-covered planet around two stars would have less cloud coverage. That would mean clearer skies for viewing double sunsets on these exotic worlds.

Author: Elizabeth Landau | Source: NASA [April 12, 2017]

byUnknown

in Astrobiology, Astronomy, Universe

April 12, 2017

Earth sized 'Tatooine' planets could be habitable

With two suns in its sky, Luke Skywalker's home planet Tatooine in "Star Wars" looks like a parched, sandy desert world. In re...

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First 'image' of a dark matter web that connects galaxies

Researchers at the University of Waterloo have been able to capture the first composite image of a dark matter bridge that connects galaxies together.

Dark matter filaments bridge the space between galaxies in this false colour map. The locations of bright galaxies 
are shown by the white regions and the presence of a dark matter filament bridging the galaxies is shown in red 
[Credit: S. Epps & M. Hudson/University of Waterloo]

The composite image, which combines a number of individual images, confirms predictions that galaxies across the universe are tied together through a cosmic web connected by dark matter that has until now remained unobservable.

Dark matter, a mysterious substance that comprises around 25 per cent of the universe, doesn't shine, absorb or reflect light, which has traditionally made it largely undetectable, except through gravity.

"For decades, researchers have been predicting the existence of dark-matter filaments between galaxies that act like a web-like superstructure connecting galaxies together," said Mike Hudson, a professor of astronomy at the University of Waterloo. "This image moves us beyond predictions to something we can see and measure."

As part of their research, Hudson and co-author Seth Epps, a master's student at the University of Waterloo at the time, used a technique called weak gravitational lensing, an effect that causes the images of distant galaxies to warp slightly under the influence of an unseen mass such as a planet, a black hole, or in this case, dark matter. The effect was measured in images from a multi-year sky survey at the Canada-France-Hawaii Telescope.

They combined lensing images from more than 23,000 galaxy pairs located 4.5 billion light-years away to create a composite image or map that shows the presence of dark matter between the two galaxies. Results show the dark matter filament bridge is strongest between systems less than 40 million light years apart.

"By using this technique, we're not only able to see that these dark matter filaments in the universe exist, we're able to see the extent to which these filaments connect galaxies together," said Epps.

The scientists publish their work in a new paper in Monthly Notices of the Royal Astronomical Society.

Source: Royal Astronomical Society [April 12, 2017]

byUnknown

in Astronomy, Astrophysics, Universe

April 12, 2017

First 'image' of a dark matter web that connects galaxies

Researchers at the University of Waterloo have been able to capture the first composite image of a dark matter bridge that connects galaxies...

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Project brings Milky Way's ionized hydrogen into focus

Like a lot of pioneering science, the Wisconsin H-Alpha Mapper (WHAM) got its start as the shoestring project of a curious young researcher.

A survey image of ionized hydrogen gas in the Milky Way. The gas, shown in red, is recognized as a distinct feature of the 
galaxy — the Reynolds Layer — named after former UW–Madison astrophysicist Ron Reynolds, who discovered it 
[Credit: WHAM COLLABORATION, UW–MADISON, SPACE SCIENCE INSTITUTE & NATIONAL SCIENCE FOUNDATION

Sawing a hole in the ceiling of an office at the University of Wisconsin–Madison's Physical Sciences Laboratory in the late 1970s, astrophysicist Ron Reynolds pointed a specially built spectrometer skyward for the first time and discovered a previously unknown feature of the Milky Way.

Everywhere he looked with his novel telescope, Reynolds observed the faint red glow of ionized hydrogen gas. It was the first hard evidence that vast clouds of ionized hydrogen—hydrogen gas atoms stripped of electrons—permeate the space between the stars. "No one expected to see ionized hydrogen out in the middle of nowhere," he said in a 2004 interview. "It's all over the sky, but it is brightest in the plane of the galaxy."

Building on those first efforts to tease out a new and mostly hidden feature of our galaxy, Reynolds and his colleagues, including Matt Haffner, a senior scientist in UW–Madison's astronomy department, developed WHAM, a spectrometer capable of detecting the faint, diffuse light emanating from the space between the stars. The instrument, supported by the National Science Foundation and operated by the Space Science Institute in Boulder, Colorado, has been in almost continuous operation for the past 20 years. It was first atop Kitt Peak in Arizona and then relocated to Cerro Tololo in Chile, where it has been observing the Southern Hemisphere sky for about the past decade.

This past month, Haffner, who assumed direction of WHAM upon Reynolds' retirement in 2005, and his colleagues released the deepest, most comprehensive survey to date of the ionized hydrogen that permeates the Milky Way. Now known to astrophysicists as the "Reynolds Layer" after the UW–Madison scientist who discovered it, the feature mapped by WHAM shows a massive amount of ionized hydrogen—a structure 75,000 light years in diameter and 6,000 light years thick—that both envelops the plane of the galaxy and rotates in step with it.

Wisconsin H-Alpha Mapper (WHAM) at the Cerro Tololo Inter-American Observatory in Chile. WHAM has been an 
astronomical workhorse, mapping a key ingredient of the Milky Way’s interstellar soup of dust and gas for two decades 
— first atop Kitt Peak, Arizona, and for about the last decade in the Andes mountains [Credit: L.M. HAFFNER]

"It's kind of like a galactic atmosphere," says Haffner. "We're tracing the same kind of emission in the visible part of the spectrum that gives rise to bright nebulae. But over much of the galaxy, it's just very, very faint."

Ionized hydrogen is one ingredient in the soup of elements that make up what astronomers call the interstellar medium, the patchy mix of dust and gas that exists between the stars. The materials found there are part of the big story of galactic life and death, says Haffner, explaining that the clouds of materials found in interstellar space come from dead and dying stars and ultimately will be recycled into new stars and planets.

The composition and dynamics of the interstellar medium, he says, can reveal how a galaxy evolves over time.

"Our galaxy is middle-aged," Haffner says. Middle age for a galaxy means it is not going through the dramatic changes typically experienced by older or younger galaxies. "In that kind of steady state, how does everything work?"

A critical insight derived from WHAM is that some stars may be bigger actors than previously believed, exerting their influence at greater distances. Ionizing hydrogen or any other element requires energy, and stars are known to ionize atoms in their immediate neighborhoods.

One reason WHAM observes so much ionized hydrogen in the plane of the galaxy is that lots of hot stars reside there. What puzzled astrophysicists, Haffner says, is how clouds of ionized hydrogen can occur light years above the plane.

"For us to see this emission everywhere, the gas has to be actively ionized," he says. "What are the sources of energy that keep it going?"

Infrared image from NASA’s Spitzer Space Telescope shows hundreds of thousands of stars crowded 
into the swirling core of the Milky Way [Credit: NASA]

What Haffner and other scientists think is happening is that what are known as O-type stars—very large, bright and relatively short-lived stars ranging in size from 15 to 90 times the mass of the sun and born deep in the plane of the galaxy—are somehow able to ionize gas across the galaxy, far from the stellar nurseries in its plane. Evidence for this idea was supplied by WHAM data, which in 2003 toppled the notion that ionized hydrogen in the galaxy occurred only in what are known as Strömgren Spheres, nebulae in the immediate vicinity of O-type stars.

WHAM may one day provide enough data to unravel the mystery of how hydrogen in interstellar deserts can be ionized, far from the stars astronomers think are responsible. It continues its survey of the galaxy on every clear, moonless night, stepping and gathering data in 30-second exposures across wide quadrants of sky.

More recently, Haffner and his colleagues have been gathering data from the Magellanic Clouds, two smaller neighboring galaxies visible from the Southern Hemisphere. Having data from galaxies beyond the Milky Way, he says, may well provide insight into the puzzles of our own galaxy.

Author: Terry Devitt | Source: University of Wisconsin-Madison [April 11, 2017]

byUnknown

in Astronomy, Universe

April 11, 2017

Project brings Milky Way's ionized hydrogen into focus

Like a lot of pioneering science, the Wisconsin H-Alpha Mapper (WHAM) got its start as the shoestring project of a curious young researcher....

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'Cold' great spot discovered on Jupiter

A second Great Spot has been discovered on Jupiter by University of Leicester astronomers, rivalling the scale of the planet's famous Great Red Spot and created by the powerful energies exerted by the great planet's polar aurorae.

The Great Cold Spot was first discovered on Jupiter using observations taken of Jupiter’s auroral region by the CRIRES 
instrument on ESO’s Very Large Telescope. The images on the left show the bright arcs of Jupiter’s infrared aurora on two 
separate nights, the top left image on 17 October and three images taken 31 December 2012, as the planet slowly rotates. 
However, the Great Cold Spot cannot be seen clearly until these images are saturated so that the entire aurora becomes 
white, as shown on the right. Here, the planet glows as a result of the temperature of the upper atmosphere, and the 
distinct regions of cooling that reveal the Great Cold Spot can be seen [Credit: VLT/ESO]

Dubbed the 'Great Cold Spot', it has been observed as a localised dark spot, up to 24,000 km in longitude and 12,000 km in latitude, in the gas giant's thin high-altitude thermosphere, that is around 200K (Kelvin) cooler than the surrounding atmosphere, which can range in temperature between 700K (426ºC) and 1000K (726ºC).

Dr Tom Stallard, Associate Professor in Planetary Astronomy and lead author of the study, said: "This is the first time any weather feature in Jupiter's upper atmosphere has been observed away from the planet's bright aurorae.

"The Great Cold Spot is much more volatile than the slowly changing Great Red Spot, changing dramatically in shape and size over only a few days and weeks, but it has re-appeared for as long as we have data to search for it, for over 15 years. That suggests that it continually reforms itself, and as a result it might be as old as the aurorae that form it -- perhaps many thousands of years old."

This image shows how the Great Cold Spot changes dramatically in shape and size on different days. Each view comes from 
a different day, with the spot sometimes almost disappearing. Because the feature is dynamic, changing over both daily and 
yearly timescales, it is likely that this feature is a weather system that is in a constant state of change. But despite this 
variability, it is seen again fifteen years later, showing it must reform again and again [Credit: IRTF/NASA]

The Great Cold Spot is thought to be caused by the effects of the magnetic field of the planet, with the massive planet's spectacular polar aurorae driving energy into the atmosphere in the form of heat flowing around the planet.

This creates a region of cooling in the thermosphere, the boundary layer between the underlying atmosphere and the vacuum of space. Although we can't be sure what drives this weather feature, a sustained cooling is very likely to drive a vortex similar to the Great Red Spot.

The astronomers used the CRIRES instrument on the Very Large Telescope (VLT) to observe spectral emissions of H3+, an ion of hydrogen present in large amounts in Jupiter's atmosphere, which allowed the scientists to map the mean temperature and density of the planet's atmosphere. They then used images of H3+ emission from Jupiter's ionosphere taken by NASA's InfraRed Telescope Facility between 1995-2000 to compare.

Through combining images taken over a period of time, including over 13,000 images taken over more than 40 nights by the InfraRed Telescope Facility, the astronomers revealed the presence of the Great Cold Spot as an area of darkness amongst the hot environment of Jupiter's upper atmosphere.

Dr Stallard, who is funded by the Science and Technology Facilities Council, added: "What is surprising at Jupiter is that, unlike weather systems on Earth, the Great Cold Spot has been observed at the same place across 15 years. That makes it more comparable to weather systems in Jupiter's lower atmosphere, like the Great Red Spot.

"Observations and modelling of Earth's upper atmosphere have shown that, on the short term, there may be changes in the temperature and density of the upper atmosphere.

This is a map of the north hemisphere of Jupiter ionosphere, added up over 13,000 images, 
and more than 40 nights. In the top image, the aurora is clearly seen, but only once the
 aurora is saturated can the non-auroral emission be removed. This reveals that the Great 
Cold Spot can be seen as a continuously observed feature over the entire six years 
of the IRTF observing campaign – which started more than 15 years before 
the VLT observation [Credit: IRTF/NASA]

"The two main differences are firstly that Earth's aurora sees dramatic changes caused by activity from the Sun, whereas Jupiter's aurora are dominated by gases from the volcanic moon Io, which are relatively slow and steady, and secondly that the atmospheric flows generated by Earth's aurora can drive heat quickly across the whole planet, making the upper atmosphere ring like a bell, while Jupiter's fast spin traps this energy nearer the poles."

Dr Stallard added: "The detection of the Great Cold Spot was a real surprise to us, but there are indications that other features might also exist in Jupiter's upper atmosphere. Our next step will be to look for other features in the upper atmosphere, as well as investigating the Great Cold Spot itself in more detail.

"The Juno spacecraft is currently in orbit around Jupiter and the observations of Jupiter's aurora and upper atmosphere by the JIRAM instrument that have been released so far already provide a wealth of new information about the planet. When combined with our ongoing campaign of observations using telescopes on Earth, we hope to gain a much better understanding of this weather system in the next few years."

The results are published in Geophysical Research Letters.

Source: University of Leicester [April 11, 2017]

byUnknown

in Astronomy, Universe

April 11, 2017

'Cold' great spot discovered on Jupiter

A second Great Spot has been discovered on Jupiter by University of Leicester astronomers, rivalling the scale of the planet's famous Gr...

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Explosive material: The making of a supernova

In the most common type of supernova, the iron core of a massive star suddenly collapses in on itself and the outer layers are thrown out into space in a spectacular explosion. New research led by Weizmann Institute of Science researchers shows that the stars that become so-called core-collapse supernovae might already exhibit instability for several months before the big event, spewing material into space and creating a dense gas shell around themselves. They think that many massive stars, including the red super-giants that are the most common progenitors of these supernovae, may begin the process this way.

Pre-supernova stars may show signs of instability for months before the big explosion 
[Credit: Weizmann Institute of Science]

This insight into the conditions leading up to core collapse arose from a unique collaboration called the Palomar Transient Factory, a fully automated sky survey using the telescopes of the Palomar observatory in southern California. Astrophysicists halfway around the globe, in Israel, are on call for the telescope, which scans the California night sky for the sudden appearance of new astronomical "transients" that were not visible before -- which can indicate new supernovae. In October, 2013, Dr. Ofer Yaron, in the Weizmann Institute's Particle Physics and Astrophysics Department, got the message that a potential supernova had been sighted, and he immediately alerted Dr. Dan Perley who was observing that night with the Keck telescope in Hawaii, and NASA's Swift Satellite. At Keck, the researchers soon began to record the spectra of the event. Because they had started observing only three hours into the blast, the picture the team managed to assemble was the most detailed ever of the core collapse process. "We had x-rays, ultraviolet, four spectroscopic measurements from between six and ten hours post-explosion to work with," says Yaron.

In a study recently published in Nature Physics, Yaron, Weizmann Institute researchers Profs. Avishay Gal-Yam and Eran Ofek, and their teams, together with researchers from the California Institute of Technology and other institutes in the United States, Denmark, Sweden, Ireland, Israel and the UK, analyzed the unique dataset they had collected from the very first days of the supernova.

The time window was crucial: It enabled the team to detect material that had surrounded the star pre- explosion, as it heated up and became ionized and was eventually overtaken by the expanding cloud of stellar matter. Comparing the observed early spectra and light-curve data with existing models, accompanied by later radio observations, led the researchers to conclude that the explosion was preceded by a period of instability lasting for around a year. This instability caused material to be expelled from the surface layers of the star, forming the circumstellar shell of gas that was observed in the data. Because this was found to be a relatively standard type II supernova, the researchers believe that the instability they revealed may be a regular warm up act to the immanent explosion.

"We still don't really understand the process by which a star explodes as a supernova," says Yaron, "These findings are raising new questions, for example, about the final trigger that tips the star from merely unstable to explosive. With our globe-spanning collaboration that enables us to alert various telescopes to train their sights on the event, we are getting closer and closer to understanding what happens in that instant, how massive stars end their life and what leads up to the final explosion."

Source: Weizmann Institute of Science [April 10, 2017]

byUnknown

in Astronomy, Universe

April 10, 2017

Explosive material: The making of a supernova

In the most common type of supernova, the iron core of a massive star suddenly collapses in on itself and the outer layers are thrown out in...

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How life may have begun in space

What chemical processes in space could have created the building blocks of life is being researched by chemists at Ruhr-Universität Bochum (RUB) in Prof Dr Wolfram Sander's team. In their experiments, the scientists are simulating the conditions in space to understand in detail how certain chemical reactions occur.

How the building blocks of life came to Earth is an unsolved puzzle. Maybe comets had something to do with it 
[Credit: NASA/JPL-Caltech]

One theory says that the building blocks of life were not created on Earth. Cometary impacts may have brought amino acids, the basic units of proteins, to our planet. How such complex molecules could have formed in space is a question being investigated by Sander's team. The scientists are interested in processes in a condensed phase, i.e. in liquids, solids or on surfaces, into which there has been little research.

A precursor of amino acids

Besides hydrogen and oxygen, the icy core of comets usually also contains nitrogen and carbon -- all the elements needed for an amino acid. A possible precursor of amino acids in space could be the molecule hydroxylamine (NH2-OH), which consists of one nitrogen, one oxygen and three hydrogen atoms. However, it has not yet been possible to verify this in space.

RUB PhD student Yetsedaw Tsegaw investigated in an experiment whether the conditions in space would actually allow this molecule to form. He adjusted the conditions in the comet ice in the lab, brought ammonia (NH3) and oxygen (O2) together in this environment and treated the mixture with high-energy radiation, such as that found in space. He observed the reactions that occurred with a special form of infrared spectroscopy.

Hidden molecule

Tsegaw took the measurements as a guest researcher in the working group of Prof Dr Ralf Kaiser at "WM Keck Research Laboratory in Astrochemistry" in Hawaii. He then analysed the data at RUB. The result: hydroxylamine was actually created in the experiment. However, it was not visible at first sight. The bands of hydroxylamine were overlaid in the infrared spectrum by the bands of other molecules. Only when Tsegaw gradually warmed the sample and the interfering substances evaporated was he able to identify hydroxylamine.

In theory, the molecule could thus form in comet ice. The chemist presumes that people had not been searching for it using the right methods until now.

You can find more information in a detailed article in the science magazine Rubin at Ruhr-Universität Bochum.

Source: Ruhr-Universitaet-Bochum [April 10, 2017]

byUnknown

in Astrobiology, Astronomy, Origin of Life, Universe

April 10, 2017

How life may have begun in space

What chemical processes in space could have created the building blocks of life is being researched by chemists at Ruhr-Universität Bochum (...

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Hubble spots auroras on Uranus

This is a composite image of Uranus by Voyager 2 and two different observations made by Hubble -- one for the ring and one for the auroras.

This is a composite image of Uranus by Voyager 2 and two different observations made by Hubble -- one for the ring and 
one for the auroras. Astronomers tracked the interplanetary shocks caused by two powerful bursts of solar wind traveling 
from the sun to Uranus, then used Hubble to capture their effect on Uranus' auroras -- and found themselves observing the 
most intense auroras ever seen on the planet. By watching the auroras over time, they collected the first direct evidence that 
these powerful shimmering regions rotate with the planet. They also re-discovered Uranus' long-lost magnetic poles, which 
were lost shortly after their discovery by Voyager 2 in 1986 due to uncertainties in measurements and the featureless 
planet surface [Credit: ESA/Hubble & NASA, L. Lamy / Observatoire de Paris]

Ever since Voyager 2 beamed home spectacular images of the planets in the 1980s, planet-lovers have been hooked on auroras on other planets. Auroras are caused by streams of charged particles like electrons that come from various origins such as solar winds, the planetary ionosphere, and moon volcanism. They become caught in powerful magnetic fields and are channeled into the upper atmosphere, where their interactions with gas particles, such as oxygen or nitrogen, set off spectacular bursts of light.

The auroras on Jupiter and Saturn are well-studied, but not much is known about the auroras of the giant ice planet Uranus. In 2011, the NASA/ESA Hubble Space Telescope became the first Earth-based telescope to snap an image of the auroras on Uranus. In 2012 and 2014 a team led by an astronomer from Paris Observatory took a second look at the auroras using the ultraviolet capabilities of the Space Telescope Imaging Spectrograph (STIS) installed on Hubble.

They tracked the interplanetary shocks caused by two powerful bursts of solar wind traveling from the sun to Uranus, then used Hubble to capture their effect on Uranus' auroras -- and found themselves observing the most intense auroras ever seen on the planet. By watching the auroras over time, they collected the first direct evidence that these powerful shimmering regions rotate with the planet. They also re-discovered Uranus' long-lost magnetic poles, which were lost shortly after their discovery by Voyager 2 in 1986 due to uncertainties in measurements and the featureless planet surface.

Source: NASA/Goddard Space Flight Center [April 10, 2017]

byUnknown

in Astronomy, Universe

April 10, 2017

Hubble spots auroras on Uranus

This is a composite image of Uranus by Voyager 2 and two different observations made by Hubble -- one for the ring and one for the auroras. ...

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