Loneliest Young Star Seen by Spitzer and WISE

NASA - Spitzer Space Telescope logo / NASA - WISE Mission patch.

July 27, 2016

Image above: An unusual celestial object called CX330 was first detected as a source of X-ray light in 2009. It has been launching “jets” of material into the gas and dust around it. Image Credits: NASA/JPL-Caltech.

Alone on the cosmic road, far from any known celestial object, a young, independent star is going through a tremendous growth spurt.

The unusual object, called CX330, was first detected as a source of X-ray light in 2009 by NASA's Chandra X-Ray Observatory while it was surveying the bulge in the central region of the Milky Way. Further observations indicated that this object was emitting optical light as well. With only these clues, scientists had no idea what this object was.

But when Chris Britt, postdoctoral researcher at Texas Tech University in Lubbock, and colleagues were examining infrared images of the same area taken with NASA's Wide-field Infrared Survey Explorer (WISE), they realized this object has a lot of warm dust around it, which must have been heated by an outburst.

Comparing WISE data from 2010 with Spitzer Space Telescope data from 2007, researchers determined that CX330 is likely a young star that had been outbursting for several years. In fact, in that three-year period its brightness had increased by a few hundred times.

Astronomers looked at data about the object from a variety of other observatories, including the ground-based SOAR, Magellan, and Gemini telescopes. They also used the large telescope surveys VVV and the OGLE-IV to measure the intensity of light emitted from CX330. By combining all of these different perspectives on the object, a clearer picture emerged.

"We tried various interpretations for it, and the only one that makes sense is that this rapidly growing young star is forming in the middle of nowhere," said Britt, lead author of a study on CX330 recently published in the Monthly Notices of the Royal Astronomical Society.

Spitzer Space Telescope. Image Credit: NASA

The lone star's behavior has similarities to FU Orionis, a young outbursting star that had an initial three-month outburst in 1936-7. But CX330 is more compact, hotter and likely more massive than the FU Orionis-like objects known. The more isolated star launches faster "jets," or outflows of material that slam into the gas and dust around it.

"The disk has probably heated to the point where the gas in the disk has become ionized, leading to a rapid increase in how fast the material falls onto the star," said Thomas Maccarone, study co-author and associate professor at Texas Tech.

Most puzzling to astronomers, FU Orionis and the rare objects like it -- there are only about 10 of them -- are located in star-forming regions. Young stars usually form and feed from their surrounding gas and dust-rich regions in star-forming clouds. By contrast, the region of star formation closest to CX330 is over a thousand light-years away.

"CX330 is both more intense and more isolated than any of these young outbursting objects that we've ever seen," said Joel Green, study co-author and researcher at the Space Telescope Science Institute in Baltimore. "This could be the tip of the iceberg -- these objects may be everywhere."

In fact, it is possible that all stars go through this dramatic stage of development in their youth, but that the outbursts are too short in cosmological time for humans to observe many of them.

How did CX330 become so isolated? One idea is that it may have been born in a star-forming region, but was ejected into its present lonely pocket of the galaxy. But this is unlikely, astronomers say. Because CX330 is in a youthful phase of its development -- likely less than 1 million years old -- and is still eating its surrounding disk, it must have formed near its present location in the sky.

"If it had migrated from a star-forming region, it couldn't get there in its lifetime without stripping its disk away entirely," Britt said.

Wide-field Infrared Survey Explorer (WISE). Image Credit: NASA

CX330 may also help scientists study the way stars form under different circumstances. One scenario is that stars form through turbulence. In this "hierarchical" model, a critical density of gas in a cloud causes the cloud to gravitationally collapse into a star. A different model, called "competitive accretion," suggests that stars begin as low-mass cores that fight over the mass of material left in the cloud. CX330 more naturally fits into the first scenario, as the turbulent circumstances would theoretically allow for a lone star to form.

It is still possible that other intermediate- to low-mass stars are in the immediate vicinity of CX330, but have not been detected yet.

When CX330 was last viewed in August 2015, it was still outbursting. Astronomers plan to continue studying the object, including with future telescopes that could view it in other wavelengths of light.

Outbursts from a young star change the chemistry of the star's disk, from which planets may eventually form. If the phenomenon is common, that means that planets, including our own, may carry the chemical signatures of an ancient disk of gas and dust scarred by stellar outbursts.

But as CX330 is continuing to devour its disk with increasing voracity, astronomers do not expect that planets are forming in its system.

"If it's truly a massive star, its lifetime is short and violent, and I wouldn't recommend being a planet around it," Green said. "You could experience some pretty intense heat for a few centuries."

For more information on WISE, visit: http://www.nasa.gov/wise

For more information on Spitzer, visit: http://www.nasa.gov/spitzer

Images (mentioned), Text, Credits: NASA/Tony Greicius/JPL/Elizabeth Landau.

Greetings, Orbiter.ch

Jupiter’s Great Red Spot Likely a Massive Heat Source

NASA patch.

July 27, 2016

New NASA-funded research suggests that Jupiter’s Great Red Spot may be the mysterious heat source behind Jupiter’s surprisingly high upper atmospheric temperatures.

Here on Earth, sunlight heats the atmosphere at altitudes well above the surface—for example, at 250 miles above our planet where the International Space Station orbits. Scientists have been stumped as to why temperatures in Jupiter’s upper atmosphere are comparable to those found at Earth, yet Jupiter is more than five times the distance from the sun. They wanted to know: if the sun isn’t the heat source, then what is?

Researchers from Boston University’s Center for Space Physics set out to solve the mystery by mapping temperatures well above Jupiter’s cloud tops using observations from Earth. They analyzed data from the SpeX spectrometer at NASA’s Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii, a 3-meter infrared telescope operated for NASA by the University of Hawaii. By observing non-visible infrared light hundreds of miles above the gas giant, scientists found temperatures to be much higher in certain latitudes and longitudes in Jupiter’s southern hemisphere, where the spot is located.

Image above: Artist’s concept of the heating mechanism from Jupiter’s Great Red Spot. Image Credits: Art by Karen Teramura, UH IfA with James O’Donoghue and Luke Moore.

“We could see almost immediately that our maximum temperatures at high altitudes were above the Great Red Spot far below—a weird coincidence or a major clue?” said Boston University’s James O’Donoghue, lead author of the study.

The study, in the July 27 issue of the journal Nature, concludes that the storm in the Great Red Spot produces two kinds of turbulent energy waves that collide and heat the upper atmosphere. Gravity waves are much like how a guitar string moves when plucked, while acoustic waves are compressions of the air (sound waves). Heating in the upper atmosphere 500 miles (800 kilometers) above the Great Red Spot is thought to be caused by a combination of these two wave types “crashing,” like ocean waves on a beach.

“The extremely high temperatures observed above the storm appear to be the ‘smoking gun’ of this energy transfer,” said O’Donoghue. “This tells us that planet-wide heating is a plausible explanation for the ‘energy crisis,’ a problem in which upper-atmospheric temperatures are measured hundreds of degrees hotter than can be explained by sunlight alone.”

This effect has been observed over the Andes Mountains here on Earth and may also be happening elsewhere in the outer solar system, though it has not been directly observed. Scientists believe this phenomenon also occurs on giant exoplanets orbiting other stars.
The Great Red Spot (GRS) has delighted and mystified since its discovery in the 17th Century. With its swirl of reddish hues, it’s 2-3 times as wide as Earth and is seen by many as a “perpetual hurricane,” with winds peaking at about 400 miles an hour.

NASA's Juno spacecraft, which recently arrived at Jupiter, will have several opportunities during its 20-month mission to observe the Great Red Spot and the turbulent region surrounding it. Juno will peer hundreds of miles downward into the atmosphere with its microwave radiometer, which passively senses heat coming from within the planet. This capability will enable Juno to reveal the deep structure of the Great Red Spot, along with other prominent Jovian features, such as the colorful cloud bands.

Links:

Boston University’s Center for Space Physics: http://www.bu.edu/csp/

Solar System: https://www.nasa.gov/topics/solarsystem/index.html

Image (mentioned), Text, Credits: NASA/Tricia Talbert.

Greetings, Orbiter.ch

White Dwarf Lashes Red Dwarf with Mystery Ray

ESO - European Southern Observatory logo / ESA - Hubble Space Telescope logo.

27 July 2016

Artist’s impression of the exotic binary star system AR Scorpii

Astronomers using ESO’s Very Large Telescope, along with other telescopes on the ground and in space, have discovered a new type of exotic binary star. In the system AR Scorpii a rapidly spinning white dwarf star powers electrons up to almost the speed of light. These high energy particles release blasts of radiation that lash the companion red dwarf star, and cause the entire system to pulse dramatically every 1.97 minutes with radiation ranging from the ultraviolet to radio. The research will be published in the journal Nature on 28 July 2016.

In May 2015, a group of amateur astronomers from Germany, Belgium and the UK came across a star system that was exhibiting behaviour unlike anything they had ever encountered. Follow-up observations led by the University of Warwick and using a multitude of telescopes on the ground and in space [1], have now revealed the true nature of this previously misidentified system.

The star system AR Scorpii, or AR Sco for short, lies in the constellation of Scorpius, 380 light-years from Earth. It comprises a rapidly spinning white dwarf [2], the size of Earth but containing 200 000 times more mass, and a cool red dwarf companion one third the mass of the Sun [3], orbiting one another every 3.6 hours in a cosmic dance as regular as clockwork.

AR Scorpii in the constellation of Scorpius

In a unique twist, this binary star system is exhibiting some brutal behaviour. Highly magnetic and spinning rapidly, AR Sco’s white dwarf accelerates electrons up to almost the speed of light. As these high energy particles whip through space, they release radiation in a lighthouse-like beam which lashes across the face of the cool red dwarf star, causing the entire system to brighten and fade dramatically every 1.97 minutes. These powerful pulses include radiation at radio frequencies, which has never been detected before from a white dwarf system.

Lead researcher Tom Marsh of the University of Warwick’s Astrophysics Group commented: “AR Scorpii was discovered over 40 years ago, but its true nature was not suspected until we started observing it in 2015. We realised we were seeing something extraordinary within minutes of starting the observations.”

The observed properties of AR Sco are unique. They are also mysterious. The radiation across a broad range of frequencies is indicative of emission from electrons accelerated in magnetic fields, which can be explained by AR Sco’s spinning white dwarf. The source of the electrons themselves, however, is a major mystery — it is not clear whether it is associated with the white dwarf itself, or its cooler companion.

Wide-field view of the sky around the exotic binary star system AR Scorpii

AR Scorpii was first observed in the early 1970s and regular fluctuations in brightness every 3.6 hours led it to be incorrectly classified as a lone variable star [4]. The true source of AR Scorpii’s varying luminosity was revealed thanks to the combined efforts of amateur and professional astronomers. Similar pulsing behaviour has been observed before, but from neutron stars — some of the densest celestial objects known in the Universe  — rather than white dwarfs.

Artist’s impression video of the exotic binary star system AR Scorpii

Boris Gänsicke, co-author of the new study, also at the University of Warwick, concludes: "We've known pulsing neutron stars for nearly fifty years, and some theories predicted white dwarfs could show similar behaviour. It's very exciting that we have discovered such a system, and it has been a fantastic example of amateur astronomers and academics working together."

Zooming in on the exotic binary star AR Scorpii

Notes:

[1] The observations underlying this research were carried out on: ESO’s Very Large Telescope (VLT) located at Cerro Paranal, Chile; the William Herschel and Isaac Newton Telescopes of the Isaac Newton Group of telescopes sited on the Spanish island of La Palma in the Canaries; the Australia Telescope Compact Array at the Paul Wild Observatory, Narrabri, Australia; the NASA/ESA Hubble Space Telescope; and NASA's Swift satellite.

[2]  White dwarfs form late in the life cycles of stars with masses up to about eight times that of our Sun. After hydrogen fusion in a star’s core is exhausted, the internal changes are reflected in a dramatic expansion into a red giant, followed by a contraction accompanied by the star’s outer layers being blown off in great clouds of dust and gas. Left behind is a white dwarf, Earth-sized but 200 000 times more dense. A single spoonful of the matter making up a white dwarf would weigh about as much as an elephant here on Earth.

[3] This red dwarf is an M type star. M type stars are the most common class in the Harvard classification system, which uses single letters to group stars according their spectral characteristics. The famously awkward to remember sequence of classes runs: OBAFGKM, and is often remembered using the mnemonic Oh Be A Fine Girl/Guy, Kiss Me.

[4] A variable star is one whose brightness fluctuates as seen from Earth. The fluctuations may be due to the intrinsic properties of the star itself changing. For instance some stars noticeably expand and contract. It could also be due to another object regularly eclipsing the star. AR Scorpii was mistaken for a single variable star as the orbiting of two stars also results in regular fluctuations in observed brightness.

More information:

This research was presented in a paper entitled “A radio pulsing white dwarf binary star”, by T. Marsh et al., to appear in the journal Nature on 28 July 2016.

The team is composed of  T.R. Marsh (University of Warwick, Coventry, UK), B.T. Gänsicke (University of Warwick, Coventry, UK),  S. Hümmerich (Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne e.V., Germany; American Association of Variable Star Observers (AAVSO), USA) , F.-J. Hambsch (Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne e.V., Germany; American Association of Variable Star Observers (AAVSO), USA; Vereniging Voor Sterrenkunde (VVS), Belgium), K. Bernhard (Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne e.V., Germany; American Association of Variable Star Observers (AAVSO),USA), C.Lloyd (University of Sussex, UK), E. Breedt (University of Warwick, Coventry, UK), E.R. Stanway (University of Warwick, Coventry, UK), D.T. Steeghs (University of Warwick, Coventry, UK), S.G. Parsons (Universidad de Valparaiso, Chile), O. Toloza (University of Warwick, Coventry, UK), M.R. Schreiber (Universidad de Valparaiso, Chile), P.G. Jonker (Netherlands Institute for Space Research, The Netherlands; Radboud University Nijmegen, The Netherlands), J. van Roestel (Radboud University Nijmegen, The Netherlands), T. Kupfer (California Institute of Technology, USA), A.F. Pala (University of Warwick, Coventry, UK) , V.S. Dhillon (University of Sheffield, UK; Instituto de Astrofisica de Canarias, Spain; Universidad de La Laguna, Spain), L.K. Hardy (University of Warwick, Coventry, UK; University of Sheffield, UK), S.P. Littlefair (University of Sheffield, UK), A. Aungwerojwit (Naresuan University, Thailand),  S. Arjyotha (Chiang Rai Rajabhat University, Thailand), D. Koester (University of Kiel, Germany),  J.J. Bochinski (The Open University, UK), C.A. Haswell (The Open University, UK), P. Frank (Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne e.V., Germany) and P.J. Wheatley (University of Warwick, Coventry, UK).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links:

ESO’s Very Large Telescope (VLT): http://www.eso.org/paranal/

NASA/ESA Hubble Space Telescope: https://www.spacetelescope.org/

Australia Telescope Compact Array: https://www.narrabri.atnf.csiro.au/

NASA's Swift satellite: http://swift.gsfc.nasa.gov/

Isaac Newton Group of telescopes: http://www.ing.iac.es/

Research paper: http://www.eso.org/public/archives/releases/sciencepapers/eso1627/eso1627a.pdf

Photos of the VLT: http://www.eso.org/public/images/archive/category/paranal/

Images of Hubble: http://www.spacetelescope.org/images/archive/category/spacecraft/

Link to science paper: http://www.spacetelescope.org/static/archives/releases/science_papers/heic1616/heic1616a.pdf

Images, Text, Credits: ESO/M. Garlick/University of Warwick/IAU and Sky & Telescope/Digitized Sky Survey 2. Acknowledgement: Davide De Martin/ESA/Hubble/Mathias Jäger/Department of Physics, University of Warwick/Tom Marsh/Boris Gänsicke/Videos: ESO/L. Calçada/University of Warwick/Digitized Sky Survey 2/N, Risinger (skysurvey.org).

Best regards, Orbiter.ch

The Case of the Missing Ceres Craters

NASA - Dawn Mission patch.

July 26, 2016

Ceres Missing Large Craters

Ceres is covered in countless small, young craters, but none are larger than 175 miles (280 kilometers) in diameter. To scientists, this is a huge mystery, given that the dwarf planet must have been hit by numerous large asteroids during its 4.5 billion-year lifetime. Where did all the large craters go?

A new study in the journal Nature Communications explores this puzzle of Ceres' missing large craters, using data from NASA's Dawn spacecraft, which has been orbiting Ceres since March 2015.


"We concluded that a significant population of large craters on Ceres has been obliterated beyond recognition over geological time scales, which is likely the result of Ceres' peculiar composition and internal evolution," said lead investigator Simone Marchi, a senior research scientist at the Southwest Research Institute in Boulder, Colorado.

Marchi and colleagues modeled collisions of other bodies with Ceres since the dwarf planet formed, and predicted the number of large craters that should have been present on its surface. These models predicted Ceres should have up to 10 to 15 craters larger than 250 miles (400 kilometers) in diameter, and at least 40 craters larger than 60 miles (100 kilometers) wide. However, Dawn has shown that Ceres has only 16 craters larger than 60 miles, and none larger than 175 miles (280 kilometers) across.

One idea about Ceres' origins holds that it formed farther out in the solar system, perhaps in the vicinity of Neptune, but migrated in to its present location. However, scientists determined that even if Ceres migrated into the main asteroid belt relatively late in solar system history, it should still have a significant number of large craters.

"Whatever the process or processes were, this obliteration of large craters must have occurred over several hundred millions of years," Marchi said.

Dawn's images of Ceres reveal that the dwarf planet has at least three large-scale depressions called "planitiae" that are up to 500 miles (800 kilometers) wide. These planitiae have craters in them that formed in more recent times, but the larger depressions could be left over from bigger impacts. One of them, called Vendimia Planitia, is a sprawling area just north of Kerwan crater, Ceres' largest well-defined impact basin. Vendimia Planitia must have formed much earlier than Kerwan.

One reason for the lack of large craters could be related the interior structure of Ceres. There is evidence from Dawn that the upper layers of Ceres contain ice. Because ice is less dense than rock, the topography could "relax," or smooth out, more quickly if ice or another lower-density material, such as salt, dominates the subsurface composition. Recent analysis of the center of Ceres' Occator Crater suggests that the salts found there could be remnants of a frozen ocean under the surface, and that liquid water could have been present in Ceres' interior.

Past hydrothermal activity, which may have influenced the salts rising to the surface at Occator, could also have something to do with the erasure of craters. If Ceres had widespread cryovolcanic activity in the past -- the eruption of volatiles such as water -- these cryogenic materials also could have flowed across the surface, possibly burying pre-existing large craters. Smaller impacts would have then created new craters on the resurfaced area.

Artist's view of Dawn spacecraft. Image Credits: NASA/JPL-Caltech

"Somehow Ceres has healed its largest impact scars and renewed old, cratered surfaces," Marchi said.

Ceres differs from Dawn's previous destination, protoplanet Vesta, in terms of cratering. Although Vesta is only half the size of Ceres, it has a well-preserved 300-mile- (500-kilometer) -wide crater called Rheasilvia, where an impacting asteroid knocked out a huge chunk of the body. This and other large craters suggest that Vesta has not had processes at work to smooth its surface, perhaps because it is thought to have much less ice. Dawn visited Vesta for 14 months from 2011 to 2012.

"The ability to compare these two very different worlds in the asteroid belt -- Vesta and Ceres -- is one of the great strengths of the Dawn mission," Marchi said.

Dawn's mission is managed by JPL for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team. For a complete list of mission participants, visit:

http://dawn.jpl.nasa.gov/mission

More information about Dawn is available at the following sites:

http://dawn.jpl.nasa.gov

http://www.nasa.gov/dawn

Image (mentioned), Video (mentioned), Text, Credits: NASA/Tony Greicius/JPL/Elizabeth Landau.

Best regards, Orbiter.ch

SolarImpulse - Completing a dream: the first Round-the-World solar flight in history

SolarImpulse - Around The World patch.

 July 26, 2016

We have now just watched our shared dream unveil, becoming a reality. It’s with great emotion that I write this last blog to report on the Round-the-World solar flights. Emotions, tears, relief, exhilaration is what we are all feeling right now after completing the first Round-the-World solar flight in history.

Bertrand Piccard made one last smooth landing, kissing the warm tarmac with his solar airplane after a 48 hour and 37 minute flight in Al Bateen Executive Airport, Abu Dhabi. He took off from Cairo, Egypt at 11:28PM UTC, 7:28PM EDT on July 23rd / 1:28AM CEST on July 24th and landed in Abu Dhabi at 12:05AM UTC, 2:05AM CEST on July 26th / 8:05PM EDT on July 25th. The solar airplane has now successfully made it full circle around the world, proving that clean technologies can really achieve the impossible.

The Mission Control Center in Monaco exploded with relief (and perhaps a little grief), as if the 13 years of weight on everyone’s shoulders had just evaporated.

This flight represents the most incredible wrap-up of this adventure. With André Borschberg joining his engineers one last time at the Mission Control Center in Monaco for the first half of the flight and Bertrand Piccard piloting the revolutionary solar airplane to the finish line.Inflight discussions were rich with passion and depth. Bertrand exchanged ideas with the dedicated UN Secretary General Ban Ki-moon, the passionate Christiana Figueres (former Executive Secretary of UNFCCC), the adventurer David de Rothschild, the newly appointed Patricia Espinosa (current Executive Secretary of UNFCCC), the Swiss President Johann Schneider-Ammann, famous R&B artist Akon, and the charming actress Marion Cotillard - sharing this achievement with them.

Completing a 13-year exploit is perhaps the biggest challenge we now face. But as always, there are new adventures to come. And for the Solar Impulse team, there definitely will be a new dream seeking to be achieved.

Solar Impulse Airplane - Bertrand Piccard's landing in Abu Dhabi

And you might be asking what’s next? Surely dreams only grow with time. Now that both pilots have made it through this journey, surely there is more to come. Find out what’s next for Bertrand Piccard and André Borschberg.

For more information about SolarImpulse Around The World, visit: http://www.solarimpulse.com/

Images, Video, Text, Credit: SolarImpulse.

Greetings, Orbiter.ch

Bent Rings

NASA - Cassini International logo.

July 25, 2016

Saturn's A and F rings appear bizarrely warped where they intersect the planet's limb, whose atmosphere acts here like a very big lens.

In its upper regions, Saturn’s atmosphere absorbs some of the light reflected by the rings as it passes through. But absorption is not the only thing that happens to that light. As it passes from space to the atmosphere and back out into space towards Cassini’s cameras, its path is refracted, or bent. The result is that the ring's image appears warped.

This view looks toward the sunlit side of the rings from about 18 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 9, 2016.

The view was acquired at a distance of approximately 1.1 million miles (1.8 million kilometers) from the rings and at a Sun-rings-spacecraft, or phase, angle of 112 degrees. Image scale is 7 miles (11 kilometers) per pixel.

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini. The Cassini imaging team homepage is at http://ciclops.org and ESA's website: http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens

Image Credit: NASA/JPL-Caltech/Space Science Institute/Tony Greicius.

Best regards, Orbiter.ch

Astronomers Discover Dizzying Spin of the Milky Way Galaxy’s “Halo”

NASA logo.

July 25, 2016

Astronomers at the University of Michigan’s College of Literature, Science, and the Arts (LSA) discovered for the first time that the hot gas in the halo of the Milky Way galaxy is spinning in the same direction and at comparable speed as the galaxy's disk, which contains our stars, planets, gas, and dust. This new knowledge sheds light on how individual atoms have assembled into stars, planets, and galaxies like our own, and what the future holds for these galaxies.

Image above: Our Milky Way galaxy and its small companions are surrounded by a giant halo of million-degree gas (seen in blue in this artists' rendition) that is only visible to X-ray telescopes in space. University of Michigan astronomers discovered that this massive hot halo spins in the same direction as the Milky Way disk and at a comparable speed. Image Credits: NASA/CXC/M.Weiss/Ohio State/A Gupta et al.

“This flies in the face of expectations,” says Edmund Hodges-Kluck, assistant research scientist. “People just assumed that the disk of the Milky Way spins while this enormous reservoir of hot gas is stationary – but that is wrong. This hot gas reservoir is rotating as well, just not quite as fast as the disk.”

The new NASA-funded research using the archival data obtained by XMM-Newton, a European Space Agency telescope, was recently published in the Astrophysical Journal. The study focuses on our galaxy’s hot gaseous halo, which is several times larger than the Milky Way disk and composed of ionized plasma.

Because motion produces a shift in the wavelength of light, the U-M researchers measured such shifts around the sky using lines of very hot oxygen. What they found was groundbreaking: The line shifts measured by the researchers show that the galaxy’s  halo spins in the same direction as the disk of the Milky Way and at a similar speed—about 400,000 mph for the halo versus 540,000 mph for the disk.

“The rotation of the hot halo is an incredible clue to how the Milky Way formed,” said Hodges Kluck. “It tells us that this hot atmosphere is the original source of a lot of the matter in the disk.”

Scientists have long puzzled over why almost all galaxies, including the Milky Way, seem to lack most of the matter that they otherwise would expect to find. Astronomers believe that about 80% of the matter in the universe is the mysterious “dark matter” that, so far, can only be detected by its gravitational pull. But even most of the remaining 20% of “normal” matter is missing from galaxy disks. More recently, some of the “missing” matter has been discovered in the halo. The U-M researchers say that learning about the direction and speed of the spinning halo can help us learn both how the material got there in the first place, and the rate at which we expect the matter to settle into the galaxy.

“Now that we know about the rotation, theorists will begin to use this to learn how our Milky Way galaxy formed – and its eventual destiny,” says Joel Bregman, a U-M LSA professor of astronomy.

“We can use this discovery to learn so much more – the rotation of this hot halo will be a big topic of future X-ray spectrographs,” Bregman says.

Related links:

Astrophysical Journal article: http://iopscience.iop.org/article/10.3847/0004-637X/822/1/21/meta

ESA's XMM-Newton: http://www.esa.int/Our_Activities/Space_Science/XMM-Newton_overview

For more information, please visit: http://heasarc.gsfc.nasa.gov/docs/xmm/xmmgof.html

Image (mentioned), Text, Credits: NASA/By Felicia Chou/Ashley Morrow.

Greetings, Orbiter.ch