In preparation for the arrival of Juno, the ESO's released stunning IR images of Jupiter, taken by the VLT. Credit: ESO
Launching back in 2011, NASA’s Juno mission has spent the past five years traversing the gulf that lies between Earth and Jupiter. When it arrives (in just a few days time!), it will be the second long-term mission to the gas giant in history. And in the process, it will obtain information about its composition, weather patterns, magnetic and gravitational fields, and history of formation.
With just days to go before this historic rendezvous takes place, the European Southern Observatory is taking the opportunity to release some spectacular infrared images of Jupiter. Taken with the Very Large Telescope (VLT), these images are part of a campaign to create high-resolutions maps of the planet, and provide a preview of the work that Juno will be doing in the coming months.
Using the VTL Imager and Spectrometer for mid-Infrared (VISIR) instrument, the ESO team – led by Dr. Leigh Fletcher of the University of Leicester – hopes that their efforts to map the planet will improve our understanding of Jupiter’s atmosphere. Naturally, with the upcoming arrival of Juno, some may wonder if these efforts are necessary.
Using images obtained by the Very Large Telescope, an ESO team managed to obtain detailed IR images of Jupiter’s atmosphere. Credit: ESO/G. Hüdepohl
After all, ground-based telescopes like the VLT are forced to contend with limitations that space-based probes are not. These include interference from our constantly-shifting atmosphere, not to mention the distances between Earth and the object in question. But in truth, the Juno mission and ground-based campaigns like these are often highly complimentary.
For one, in the past few months, while Juno was nearing in on its destination, Jupiter’s atmosphere has undergone some significant shifts. Mapping these is important to Juno‘s upcoming arrival, at which point it will be attempting to peer beneath Jupiter’s thick clouds to discern what is going on beneath. In short, the more we know about Jupiter’s shifting atmosphere, the easier it will be to interpret the Juno data.
As Dr. Fletcher described the significance of his team’s efforts:
“These maps will help set the scene for what Juno will witness in the coming months. Observations at different wavelengths across the infrared spectrum allow us to piece together a three-dimensional picture of how energy and material are transported upwards through the atmosphere.”
Like all ground-based efforts, the ESO campaign – which has involved the use of several telescopes based in Hawaii and Chile, as well as contributions from amateur astronomers around the world – faced some serious challenges (like the aforementioned interference). However, the team used a technique known as “lucky imaging” to take the breathtaking snapshots of Jupiter’s turbulent atmosphere.
This view compares a lucky imaging view of Jupiter from VISIR (left) at infrared wavelengths with a very sharp amateur image in visible light from about the same time (right). Credit: ESO/L.N. Fletcher/Damian Peach
What this comes down to is taking many sequences of images with very short exposures, thus producing thousands of individual frames. The lucky frames, those where the image are least affected by the atmosphere’s turbulence, are then selected while the rest discarded. These selected frames are aligned and combined to produce final pictures, like the one shown above.
In addition to providing information that would be of use to the Juno mission, the ESO’s campaign has value that extends beyond the space-based mission. As Glenn Orton, the leader of ESO’s ground-based campaign, explained, observations like these are valuable because they help to advance our understanding of planets as a whole, and provide opportunities for astronomers from all over the world to collaborate.
“The combined efforts of an international team of amateur and professional astronomers have provided us with an incredibly rich dataset over the past eight months,” he said. “Together with the new results from Juno, the VISIR dataset in particular will allow researchers to characterize Jupiter’s global thermal structure, cloud cover and distribution of gaseous species.”
The Juno probe will be arriving at Jupiter this coming Monday, July 4th. Once there, it will spend the next two years orbiting the gas giant, sending information back to Earth that will help to advance our understanding of not only Jupiter, but the history of the Solar System as well.
In 2010, a small, bright white storm emerged on Saturn’s northern hemisphere. This storm grew until it wrapped around the planet in curly cloud structures, creating a colossal atmospheric disturbance that endured into the early part of 2012, becoming the largest storm seen on the planet since 1990. Being in orbit around the ringed planet, the Cassini spacecraft had a front row seat to watch the disturbance unfold, allowing planetary scientists an unprecedented look at this monster storm. While the storm was visible even to amateur astronomers on Earth, much of its activity took place beyond the reach of visible-light cameras and telescopes, astronomers say. Not only did huge “beacons” of hot air chase each other around the planet, but infrared observations show a giant oval vortex is still persisting as a side effect from the storm.
“It’s the first time we’ve seen anything like it on any planet in the Solar System,” said Leigh Fletcher from the University of Oxford, UK, lead author of a paper describing the unprecedented storm. “It’s extremely unusual, as we can only see the vortex at infrared wavelengths – we can’t tell that it is there simply by looking at the cloud cover.”
Fletcher and her team also used ground-based observations with the Very Large Telescope of the European Southern Observatory in Chile, and NASA’s Infrared Telescope Facility at the summit of Mauna Kea in Hawaii.
As the visible storm erupted in the roiling cloud deck of Saturn’s troposphere, waves of energy rippled hundreds of kilometers upwards, depositing their energy as the two vast ‘beacons’ of hot air in the stratosphere.
Data from Cassini’s composite infrared spectrometer (CIRS) instrument revealed the storm’s powerful discharge sent the temperature in Saturn’s stratosphere soaring 65 degrees C (150 degrees Fahrenheit, 83 kelvins) above normal.
Researchers described in a complimentary paper that will be published in the Nov. 20 issue of the Astrophysical Journal this as a “belch” of energy, as they observed a huge increase in the amount of ethylene gas in Saturn’s atmosphere, the origin of which is a mystery. Ethylene, an odorless, colorless gas, isn’t typically observed on Saturn. On Earth, it is created by natural and man-made sources.
Researchers are still is exploring the origin of the ethylene, but they have ruled out a large reservoir deep in the atmosphere.
“We’ve really never been able to see ethylene on Saturn before, so this was a complete surprise,” said Goddard’s Michael Flasar, the CIRS team lead.
The beacons were expected to cool down and dissipate, but by late April 2011 – by which time bright cloud material had encircled the entire planet – the hot spots had merged to create an enormous vortex that for a brief period exceeded even the size of Jupiter’s famous Great Red Spot.
The forceful storm generated unprecedented spikes in temperature and increased amounts of ethylene. In these two sets of measurements taken by Cassini’s composite infrared spectrometer, yellow represents the highest temperatures. Each strip maps a single molecule (top: methane, bottom: ethylene), with temperature measurements taken in the northern hemisphere, all the way around the planet. Image credit: NASA/JPL-Caltech/GSFC
Although comparisons to Jupiter’s Red Spot have been made to this storm, Saturn’s storm was much higher in the atmosphere while Jupiter’s vortex is embedded deep down in the turbulent ‘weather zone’, Fletcher said.
Also, Jupiter’s famous vortex has raged for at least 300 years. But after traversing the planet once every 120 days since May 2011, Saturn’s large beacon is cooling and shrinking. Scientists expect it to fade away completely by the end of 2013.
The question now remains as to whether Saturn’s storm-generating energy has been sapped or if there will be a repeat performance, the team said.
The outburst already caught observers by surprise by arriving during the planet’s northern hemisphere spring, years ahead of the predictably stormy summer season.
“The beauty is that Cassini will be operating until the Saturn system reaches its summer solstice in 2017, so if there is another global event like this, we’ll be there to see it,” says ESA’s Cassini project scientist Nicolas Altobelli.
Artist's impression of the European Extremely Large Telescope. Credit: ESO
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The world’s largest optical/infrared telescope has been given the initial go-ahead to be built. Called the European Extremely Large Telescope (E-ELT) this long-proposed new ground-based telescope will have a 40-meter main mirror and observe the universe in visible and infrared light, making direct images of exoplanets, perhaps find Earth-sized and even Earth-like worlds, and study the first galaxies that formed after the Big Bang.
“This is an excellent outcome and a great day for ESO. We can now move forward on schedule with this giant project,” said the ESO Director General, Tim de Zeeuw.
At a meeting in Garching, France this week, the ESO (European Southern Observatory) Council approved the E-ELT program, with 6 out of 10 countries giving firm approval and four gave “ad referendum” approval, meaning that they needed an official green light from their governments. With that approval, officials are hopeful the E-ELT could start operations by the early 2020’s.
The new super-large eye on the sky will be built at Cerro Armazones in northern Chile, close to ESO’s Paranal Observatory.
The cost is expected to be $1.35 billion USD (1.083-billion-euro)
“World-leading projects of this kind inspire us all and are hugely effective in bringing young people into careers in science and technology,” said David Southwood, president of the Royal Astronomical Society.
This type of telescope has been on the priority list for astronomy by scientists around the world.
The E-ELT will gather 100 million times more light than the human eye, eight million times more than Galileo’s telescope which saw the four biggest moons of Jupiter four centuries ago, and 26 times more than a single VLT telescope.
“The E-ELT will tackle the biggest scientific challenges of our time, and aim for a number of notable firsts, including tracking down Earth-like planets around other stars in the ‘habitable zones’ where life could exist — one of the Holy Grails of modern observational astronomy,” the ESO said.
ESO said that early contracts for the project have already been placed. Shortly before the Council meeting, a contract was signed to begin a detailed design study for the very challenging M4 adaptive mirror of the telescope. This is one of the longest lead-time items in the whole E-ELT program, and an early start was essential.
Detailed design work for the route of the road to the summit of Cerro Armazones, where the E-ELT will be sited, is also in progress and some of the civil works are expected to begin this year. These include preparation of the access road to the summit of Cerro Armazones as well as the leveling of the summit itself.
The side of the SOFIA aircraft shows it's joint roots, a collaboration between NASA and German Scientists. Credit: Nick Howes
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One of the most remarkable observatories in the world does its work not on a mountaintop, not in space, but 45,000 feet high on a Boeing 747. Nick Howes took a look around this unique airliner as it made its first landing in Europe.
SOFIA (Stratospheric Observatory for Infrared Astronomy) came from an idea first mooted in the mid-1980s. Imagine, said scientists, using a Boeing 747 to carry a large telescope into the stratosphere where absorption of infrared light by atmospheric water molecules is dramatically reduced, even in comparison with the highest ground-based observatories. By 1996 that idea had taken a step closer to reality when the SOFIA project was formally agreed between NASA (who fund 80 percent of the cost of the 330 million dollar mission, an amount comparable to a single modest space mission) and the German Aerospace Centre (DLR, who fund the other 20 percent). Research and development began in earnest using a highly modified Boeing 747SP named the ‘Clipper Lindburgh’ after the famous American pilot, and where the ‘SP’ stands for ‘Special Performance’.
Maiden test flights were flown in 2007, with SOFIA operating out of NASA’s Dryden Flight Research Center at Edwards Airforce Base in the Rogers Dry Lake in California – a nice, dry location that helps with the instrumentation and aircraft operationally.
This scale model shows the telescope position and how the aircraft design works around it. Credit: Nick Howes.
As the plane paid a visit to the European Space Agency’s astronaut training centre in Cologne, Germany, I was given a rare opportunity to look around this magnificent aircraft as part of a European Space ‘Tweetup’ (a Twitter meeting). What was immediately noticeable was the plane’s shorter length to the ones you usually fly on, which enables the aircraft to stay in the air for longer, a crucial aspect for its most important passenger, the 2.7-metre SOFIA telescope. Its Hubble Space Telescope-sized primary mirror is aluminium coated and bounces light to a 0.4-metre secondary, all in an open cage framework that literally pokes out of the side of the aircraft.
As we have seen, the rationale for placing a multi-tonne telescope on an aircraft is that by doing so it is possible to escape most of the absorption effects of our atmosphere. Observations in infrared are largely impossible for ground-based instruments at or near sea-level and only partially possibly even on high mountaintops. Water vapour in our troposphere (the lower layer of the atmosphere) absorbs so much of the infrared light that traditionally the only way to beat this was to send up a spacecraft. SOFIA can fill a niche by doing nearly the same job but at far less risk and with a far longer life-span. The aircraft has sophisticated infrared monitoring cameras to check its own output,and water vapour monitoring to measure what little absorption is occurring.
The Sofia Telescope resides behind the multi tonne frame and control mechanism. Credit: Nick Howes.
The 2.7-metre mirror (although actually only 2.5-metres is really used in practice,) uses a glass ceramic composite that is highly thermally tolerant, which is vital given the harsh conditions that the aircraft puts the isolated telescope through. If one imagines the difficulty amateur astronomers have some nights with telescope stability in blustery conditions, spare a thought for SOFIA, whose huge f/19.9 Cassegrain reflecting telescope has to deal with an open door to the
800 kilometres per hour (500 miles per hour) winds .Nominally some operations will occur at 39,000 feet (approximately 11,880 metres) rather than the possible ceiling of 45,000 feet (13,700 metres), because while the higher altitude provides slightly better conditions in terms of lack of absorption (still above 99 percent of the water vapour that causes most of the problems), the extra fuel needed means that observation times are reduced significantly, making the 39,000
feet altitude operationally better in some instances to collect more data. The aircraft uses a cleverly designed air intake system to funnel and channel the airflow and turbulence away from the open telescope window, and speaking to the pilots and scientists, they all agreed that there was no effect caused by any output from the aircraft engines as well.
Staying cool
The cameras and electronics on all infrared observatories have to be maintained at very low temperatures to avoid thermal noise from them spilling into the image, but SOFIA has an ace up its sleeve. Unlike a space mission (with the exception of the servicing missions to the Hubble Space Telescope that each cost $1.5 billion including the price of launching a space shuttle), SOFIA has the advantage of being able to replace or repair instruments or replenish its coolant, allowing an estimated life-span of at least 20 years, far longer than any space-based infrared mission that runs out of coolant after a few years.
Meanwhile the telescope and its cradle are a feat of engineering. The telescope is pretty much fixed in azimuth, with only a three-degree play to compensate for the aircraft, but it doesn’t need to move in that direction as the aircraft, piloted by some of NASA’s finest, performs that duty for it. It can work between a 20–60 degree altitude range during science operations. It’s all been engineered to tolerances that make the jaw drop. The bearing sphere, for example, is polished to an accuracy of less than ten microns, and the laser gyros provide angular increments of 0.0008 arcseconds. Isolated from the main aircraft by a series of pressurised rubber bumpers, which are altitude compensated, the telescope is almost completely free from the main bulk of the 747, which houses the computers and racks that not only operate the telescope but provide the base station for any observational scientists flying with the plane.
PI in the Sky
The science principle investigators get to sit in relative comfort close to the telescope. Credit: Nick Howes.
The Principle Investigator station is located around the mid-point of the aircraft, several metres from the telescope but enclosed within the plane (exposed to the air at 45,000 feet, the crew and scientists would otherwise be instantly killed). Here, for ten or more hours at a time, scientists can gather data once the door opens and the telescope is pointing at the target of choice, with the pilots following a precise flight path to maintain both the instrument pointing accuracy and also to best avoid the possibility of turbulence. Whilst ground-based telescopes can respond quickly to events such as a new supernova, SOFIA is more regimented in its science operations and, with proposal cycles over six months to a year, one has to plan quite accurately how best to observe an object.
Forecasting the future
Science operations started in 2010 with FORCAST (Faint Object Infrared Camera for Sofia Telescope) and continued into 2011 with the GREAT (German Receiver for Astronomy at Teraherz Frequencies) instrument. FORCAST is a mid/far infrared instrument working with two cameras between at five and forty microns (in tandem they can work between 10–25 microns) with a 3.2 arcminute field-of-view. It saw first light on Jupiter and the galaxy Messier 82, but will be working on imaging the galactic centre, star formation in spiral and active galaxies and also looking at molecular clouds, one of its primary science goals enabling scientists to accurately determine dust temperatures and more detail on the morphology of star forming regions down to less than three-arcsecond resolution (depending on the wavelength the instrument works at). Alongside this, FORCAST is also able to perform grism (i.e. a grating prism) spectroscopy, to get more detailed information on the composition of objects under view. There is no adaptive optics system, but it doesn’t need one for the types of operations it’s doing.
FORCAST and GREAT are just two of the ‘basic’ science operation instruments, which also include Echelle spectrographs, far infrared spectrometers and high resolution wideband cameras, but already the science team are working on new instruments for the next phase of operations. Instrumentation switch over, whilst complex, is relatively quick (comparable to the time it takes to switch instruments on larger ground observatories), and can be achieved in readiness for observations, which the plane aims to do up to 160 times per year. And whilst there were no firm plans to build a sister ship for SOFIA, there have been discussions among scientists to put a larger telescope on an Airbus A380.
A model of the telescope shows its unique control and movement mechanism as well as the optical tube assembly. Credit: Nick Howes.
Sky Outreach
With a planned science ambassador programme involving teachers flying on the aircraft to do research, SOFIA’s public profile is going to grow. The science output and possibilities from instruments that are constantly evolving, serviceable and improvable every time it lands is immeasurable in comparison to space missions. Journalists had only recently been afforded the opportunity to visit this remarkable aircraft, and it was a privilege and honour to be one of the first people to see it up close. To that end I wish to thank ESA and NASA for the invitation and chance to see something so unique.
The 'Tornado Nebula.' Credit: NASA / JPL-Caltech / J. Bally (University of Colorado)
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The Spitzer Space Telescope’s Infrared Array Camera (IRAC) is a cool camera, no matter what temperature in which it operates! For 1,000 days now, the camera has been continuously taking images of the Universe – from its most distant regions to our local solar neighborhood. The IRAC is now operating in a “warm” version of its mission, as after more than five-and-a-half years of probing the cool cosmos, in 2009 it ran out of liquid helium coolant that kept its infrared instruments chilled.
“IRAC continues to be an amazing camera, still producing important discoveries and spectacular new images of the infrared universe,” said principal investigator Giovanni Fazio of the Harvard-Smithsonian Center for Astrophysics.
To commemorate 1,000 days of infrared wonders, the program is releasing a gallery of the 10 best IRAC images, featuring images from both the cold and warm portions of its mission. Above is #1: The IRAC has uncovered some mysterious objects like this so-called “tornado” nebula. Because the camera is sensitive to light emitted from shocked molecular hydrogen (seen here in green), astronomers think that this strange beast is the result of an outflowing jet of material from a young star that has generated shock waves in surrounding gas and dust.
See more below:
The Orion Nebula, as seen by Spitzer's IRAC. Credit: NASA / JPL-Caltech / Univ. of Toledo
#2. A ‘warm’ look at the famous nebula in Orion, located about 1,340 light-years from Earth, is actively making new stars today. Although the optical nebula is dominated by the light from four massive, hot young stars, IRAC reveals many other young stars still embedded in their dusty womb. It also finds a long filament of star-forming activity containing thousands of young protostars. Some of these stars may host still-forming planets.
The Helix Nebula. Credit: NASA / JPL-Caltech / J. Hora (CfA) & W. Latter (NASA/Herschel)
#3. After a long life of hydrogen-burning nuclear fusion, stars move into later life states whose details depend on their masses. This IRAC image of the Helix Nebula barely spots the star itself at the center, but clearly shows how the aging star has ejected material into space around it, creating a “planetary nebula.” The Helix Nebula is located 650 light-years away in the constellation Aquarius.
The Trifid Nebula. Credit: NASA / JPL-Caltech
#4. Located 5,400 light-years away in the constellation Sagittarius, the Trifid Nebula appears as a big maze of gas and dust. Here, Spitzer’s IRAC was observing how the processes of stellar evolution affects the surrounding environment. The Trifid Nebula hosts stars at all stages of life, and with images like this, scientists can observe how stars mature.
The 'Mountains of Creation' in the W5 region near Perseus. Credit: NASA / JPL-Caltech / CfA
#5. Within galaxies like the Milky Way, giant clouds of gas and dust coalesce under the influence of gravity until new stars are born. IRAC can both measure the warm dust and peer deeply into it to study the processes at work. In this giant cloud several stellar nurseries can be seen, some still within the tips of the dusty region that has been called the “Mountains of Creation, 7,000 light-years away from Earth.
DR22, in the constellation Cygnus the Swan. Credit: NASA / JPL-Caltech
#6. After blowing away its natal material, the young star cluster seen here emits winds and harsh ultraviolet light that sculpt the remnant cloud into fantastic shapes. Astronomers are not sure when that activity suppresses future star formation by disruption, and when it facilitates star formation through compression. The cluster, known as DR22, is in the constellation Cygnus the Swan.
Spitzer's composite of the entire Milky Way Galaxy. Credit: NASA / JPL-Caltech / E. Churchwell (Univ. of Wisconsin)
#7. IRAC has systematically imaged the entire Milky Way disk, assembling a composite photograph containing billions of pixels with infrared emission from everything in this relatively narrow plane. The image here shows five end-to-end strips spanning the center of our galaxy. This image covers only one-third of the whole galactic plane. Astronomers unveiled a 55-meter version of the image at the AAS meeting in June of 2008, and you can see the entire image on the GLIMPSE (Galactic Legacy Infrared Mid-Plane Survey Extraordinaire) Image Viewer, which provides a great way to view and browse this image.
The Whirlpool Galaxy and its companion. Credit: NASA / JPL-Caltech / R. Kennicutt (Univ. of Arizona)
#8. Collisions play an important role in galaxy evolution. These two galaxies – the Whirlpool and its companion – are relatively nearby at a distance of just 23 million light-years from Earth. IRAC sees the main galaxy as very red due to warm dust – a sign of active star formation that probably was triggered by the collision.
The Sombrero Galaxy. Credit: NASA / JPL-Caltech / R. Kennicutt (Univ. of Arizona)
#9. Star formation helps shape a galaxy’s structure through shock waves, stellar winds, and ultraviolet radiation. In this image of the nearby Sombrero Galaxy, IRAC clearly sees a dramatic disk of warm dust (red) caused by star formation around the central bulge (blue). The Sombrero is located 28 million light-years away in the constellation Virgo.
A field of galaxies, seen by Spitzer's IRAC. Credit: NASA / JPL-Caltech / SWIRE Team
#10. And coming in at #10 is this lovely image showing many points of light. They aren’t stars but entire galaxies. A few, like the mini-tadpole at upper right, are only hundreds of millions of light-years away so their shapes can be discerned. The most distant galaxies are too far away and appear as dots. Their light is seen as it was over ten billion years ago, when the universe was young.
Will we see more from Spitzer? Certainly. NASA’s Senior Review Panel has recommended extending the Spitzer warm mission through 2015.
Centaurus A in Far-infrared and X-rays. Credit: Far-infrared: ESA/Herschel/PACS/SPIRE/C.D. Wilson, MacMaster University, Canada; X-ray: ESA/XMM-Newton/EPIC
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The mysterious galaxy Centaurus A is a great place to study the extreme processes that occur near super-massive black holes, scientists say, and this beautiful new image from the combined forces of the Herschel Space Observatory and the XMM-Newton x-ray satellite reveals energetic processes going on deep in the galaxy’s core. This beautiful image tells a tale of past violence that occurred here.
The twisted disc of dust near the galaxy’s heart shows strong evidence that Centaurus A underwent a cosmic collision with another galaxy in the distant past. The colliding galaxy was ripped apart to form the warped disc, and the formation of young stars heats the dust to cause the infrared glow.
This multi-wavelength view of Centaurus A shows two massive jets of material streaming from a immense black hole in the center. When observed by radio telescopes, the jets stretch for up to a million light years, though the Herschel and XMM-Newton results focus on the inner regions.
At a distance of around 12 million light years from Earth, Centaurus A is the closest large elliptical galaxy to our own Milky Way.
“Centaurus A is the closest example of a galaxy to us with massive jets from its central black hole,” said Christine Wilson of McMaster University, Canada, who is leading the study of Centaurus A with Herschel. “Observations with Herschel, XMM-Newton and telescopes at many other wavelengths allow us to study their effects on the galaxy and its surroundings.”
This is a mosaic of the images covering the entire sky as observed by the Wide-field Infrared Survey Explorer (WISE), part of its All-Sky Data Release. Image Credit: NASA/JPL-Caltech/UCLA
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Love all the great things you can see in infrared? Then zoom on into the big view of the entire sky from the Wide-field Infrared Survey Explorer (WISE) mission. WISE has collected more than 15 trillion bytes of data with 2.7 million images of the sky at infrared light. It’s captured everything from nearby asteroids to distant galaxies, finding “Y-dwarfs,” a Trojan asteroid sharing Earth’s orbit, and stars and galaxies that had never been seen before, as well as showing astronomers that there are significantly fewer mid-size asteroids than previously thought.
Today NASA released a new atlas and catalog of the entire sky in infrared, and now even more discoveries are expected since anyone can have access to the whole sky as seen by the spacecraft.
“With the release of the all-sky catalog and atlas, WISE joins the pantheon of great sky surveys that have led to many remarkable discoveries about the universe,” said Roc Cutri, who leads the WISE data processing and archiving effort at the Infrared and Processing Analysis Center at the California Institute of Technology in Pasadena. “It will be exciting and rewarding to see the innovative ways the science and educational communities will use WISE in their studies now that they have the data at their fingertips.”
Thanks to John Williams at Starry Critters, you can now zoom into WISE’s entire map of the infrared sky. John notes some interesting things in the image: “The bright swath across the center is the Milky Way Galaxy; our home galaxy. The view is toward the center of the galaxy with the spiral arms stretching to the edges. Some artifacts were left in such as bright red spots off the plane of the galaxy. These are Saturn, Jupiter and Mars.”
Artist's impression of a brown-dwarf object (left foreground) orbiting a distant white dwarf --the collapsed-core remnant of a dying star.
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Astronomers have located a planet-like star that’s barely warmer than a balmy summer day on Earth… it’s literally the coldest object ever directly imaged outside of our solar system!
WD 0806-661 B is a brown “Y dwarf” star that’s a member of a binary pair. Its companion is a much hotter white dwarf, the remains of a Sun-like star that has shed its outer layers. The pair is located about 63 light-years away, which is pretty close to us as stars go. The stars were identified by a team led by Penn State Associate Professor of Astronomy and Astrophysics Kevin Luhman using images from NASA’s Spitzer Space Telescope. Two infrared images taken in 2004 and 2009 were overlaid on top of each other and show the stars moving in tandem, indicating a shared orbit.
These two infrared images were taken by the Spitzer Space Telescope in 2004 and 2009. They show a faint object moving through space together with a white dwarf. Credit: Kevin Luhman, Penn State University, October 2011. (Click to play.)
Of course, locating the stars wasn’t quite as easy as that. To find this stellar duo Luhman and his team searched through over six hundred images of stars located near our solar system taken years apart, looking for any shifting position as a pair.
The use of infrared imaging allowed the team to locate a dim brown dwarf star like WD 0806-661 B, which emits little visible light but shines brightly in infrared. (Even though brown dwarfs are extremely cool for stars they are still much warmer than the surrounding space. And, for the record, brown dwarfs are not actually brown.) Measurements estimate the temperature of WD 0806-661 B to be in the range of about 80 to 130 degrees Fahrenheit (26 to 54 degrees C, or 300 – 345 K)… literally body temperature!
“Essentially, what we have found is a very small star with an atmospheric temperature about cool as the Earth’s.”
– Kevin Luhman, Associate Professor of Astronomy and Astrophysics, Penn State
Six to nine times the mass of Jupiter, WD 0806-661 B is more like a planet than a star. It never accumulated enough mass to ignite thermonuclear reactions and thus more resembles a gas giant like Jupiter or Saturn. But its origins are most likely star-like, as its distance from its white dwarf companion – about 2,500 astronomical units – indicates that it developed on its own rather than forming from the other star’s disc.
There is a small chance, though, that it did form as a planet and gradually migrated out to its current distance. More research will help determine whether this may have been the case.
Brown dwarfs, first discovered in 1995, are valuable research targets because they are the next best thing to studying cool atmospheres on planets outside our solar system. Scientists keep trying to locate new record-holders for the coldest brown dwarfs, and with the discovery of WD 0806-661 B Luhman’s team has done just that!
A paper covering the team’s findings will be published in The Astrophysical Journal. Other authors of the paper include Ivo Labbé, Andrew J. Monson and Eric Persson of the Observatories of the Carnegie Institution for Science, Pasadena, Calif.; Didier Saumon of the Los Alamos National Laboratory, New Mexico; Mark S. Marley of the NASA Ames Research Center, Moffett Field, Calif.; and John J. Bochanski also of The Pennsylvania State University.
Artist concept of how a galaxy might accrete mass from rapid, narrow streams of cold gas. These filaments provide the galaxy with continuous flows of raw material to feed its star-forming at a rather leisurely pace. Credit: ESA–AOES Medialab
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Was the universe a kinder, gentler place in the past that we have thought? The Herschel space observatory has looked back across time with its infrared eyes and has seen that galaxy collisions played only a minor role in triggering star births in the past, even though today the birth of stars always seem to be generated by galaxies crashing into each other. So what was the fuel for star formation in the past?
Simple. Gas.
The more gas a galaxy contained, the more stars were born.
Scientists say this finding overturns a long-held assumption and paints a nobler picture of how galaxies evolve.
Astronomers have known that the rate of star formation peaked in the early Universe, about 10 billion years ago. Back then, some galaxies were forming stars ten or even a hundred times more vigorously than is happening in our Galaxy today.
In the nearby, present-day Universe, such high birth rates are very rare and always seem to be triggered by galaxies colliding with each other. So, astronomers had assumed that this was true throughout history.
GOODS-North is a patch of sky in the northern hemisphere that covers an area of about a third the size of the Full Moon. Credit: ESA/GOODS-Herschel consortium/David Elbaz
But Herschel’s observations of two patches of sky show a different story.
Looking at these regions of the sky, each about a third of the size of the full Moon, Herschel has seen more than a thousand galaxies at a variety of distances from the Earth, spanning 80% of the age of the cosmos.
In analyzing the Herschel data, David Elbaz, from CEA Saclay in France, and his team found that even though some galaxies in the past were creating stars at incredible rates, galaxy collisions played only a minor role in triggering star births. The astronomers were able to compare the amount of infrared light released at different wavelengths by these galaxies, the team has shown that the star birth rate depends on the quantity of gas they contain, not whether they are colliding.
They say these observations are unique because Herschel can study a wide range of infrared light and reveal a more complete picture of star birth than ever seen before.
“It’s only in those galaxies that do not already have a lot of gas that collisions are needed to provide the gas and trigger high rates of star formation,” said Elbaz.
Today’s galaxies have used up most of their gaseous raw material after forming stars for more than 10 billion years, so they do rely on collisions to jump-start star formation, but in the past galaxies grew slowly and gently from the gas that they attracted from their surroundings.
For many exoplanet systems that have been discovered by the radial velocity method, astronomers have found excess emission in the infrared portion of the spectrum. This has generally been interpreted as remnants of a disk or collection of objects similar to our own Kupier belt, a ring of icy bodies beyond the orbit of Pluto. But as Kepler and other exoplanet finding missions rake in the candidates though transits of the parent star, astronomers began noticing something unusual: None of the exoplanet systems discovered through this method were known to have debris disks. Was this an odd selection effect, perhaps induced by the fact that transiting planets often orbit close to their parent stars, making them more likely to pass along the line of sight which could in turn, betray different formation scenarios? Or were astronomers simply not looking hard enough? A recent paper by astronomers at the Astrophysikalisches Institut in Germany attempts to answer that question.
In order to do so, the team compared the (at the time) 93 known transiting exoplanets to stars for which archival data was available through infrared missions such has IRAS, ISO, AKARI, and WISE. The team then searched the data looking for a previously unrecognized bump in the emission in the infrared. Many of the stars they searched were faint, due to distance, so most of the IR telescopes did not have images with sufficient depth to draw much in the way of conclusions. Between IRAS, ISO, Spitzer, and AKARI, the team was only able to examine three stars, and all of those came from Spitzer observations.
The most plentiful return came from the WISE telescope which had 53 entries that overlapped with known transiting systems, one of which was excluded due to image defects. From these 52 candidates, the team found four that may have contained excess emission. To follow up, the team added observations from other observatories that lied in the near infrared (the 2MASS survey) and the visual portion of the spectrum. This allowed them to build a more complete picture of the brightness of the stars at various wavelengths which would make the excess stand out even more. While all four systems deviated from an ideal blackbody in the portion of the spectrum expected for a debris disk, only two of them, TrES-2, and XO-5, did so in a manner that did so in a statistically significant manner.
While this study shows that debris disks are possible around transiting stars, it was only able to confirm their presence in two stars out of 52, or just under 4% of their sample. But how does that compare to systems discovered by other methods? One of the studies cited in the paper used a similar method of comparing archival data from IR observatories to known exoplanet system discovered by other methods in 2009. In this study, the team found debris disks around 10 of the 150 planet-bearing stars, which is roughly 7%. Due to the low return rate on both of these studies, the inherent uncertainty puts these two figures within a plausible range of one another, but certainly, more studies will be in order in the future. They will help astronomers determine just what difference exists, if any, as well as giving more insight into how planetary system form and evolve.
