Posted on by Fraser Cain

Integral Uses the Earth to Search for Cosmic Radiation

Artist’s impression of Integral observing Earth. Image credit: ESA Click to enlarge
Cosmic space is filled with continuous, diffuse high-energy radiation. To find out how this energy is produced, the scientists behind ESA’s Integral gamma-ray observatory have tried an unusual method: observing Earth from space.

During a four-phase observation campaign started on 24 January this year, continued until 9 February, Integral has been looking at Earth. Needing complex control operations from the ground, the satellite has been kept in a fixed orientation in space, while waiting for Earth to drift through its field of view.

Unusually, the main objective of these observations is not Earth itself, but what can be seen in the background when Earth moves in front of the satellite. This is the origin of the diffuse high-energy radiation known as the ‘cosmic X-ray background’.

Until now with Integral, this was never studied simultaneously with such a broad band of energy coverage since the 1970s, and certainly not with such advanced instruments.

Astronomers believe that the ‘cosmic X-ray background’ is produced by numerous supermassive and accreting black holes, distributed throughout deep space. These powerful monsters attract matter, which is then hugely accelerated and so emit high energy in the form of gamma- and X-rays.

X-ray observatories such as ESA’s XMM-Newton and NASA’s Chandra have been able to identify and directly count a large number of individual sources ? likely black holes ? that already account for more than 80 percent of the measured cosmic diffuse X-ray background.

However, very little is known about the origin of the highest energy band of this cosmic radiation, above the range of these two satellites. This is spread out in the form of high-energy X- and gamma-rays, within the reach of Integral.

It is believed that most of the gamma-ray background emission is produced by individual supermassive black holes too, but scientists need to couple this emission with clearly identified sources to make a definitive statement. In fact, other sources such as far-away galaxies or close weak sources could be also be responsible.

Identifying the individual sources in the gamma-ray range that make up the diffuse cosmic background is much more difficult than counting the individual X-ray sources. In fact, the powerful gamma-rays cannot be focused with lenses or mirrors, because they simply pass straight through.

So to produce a gamma-ray image of a source, Integral uses a ‘mask’ technique – an indirect imaging method that consists of detecting the shadow of a mask placed on top of the telescope, as projected by a gamma-ray source.

During the observations, the scientists used Earth’s disk as an ‘extra mask’. Earth naturally blocks, or shades, the highest energy flux from millions of distant black holes.

Their combined flux can be accurately measured in an indirect way, that is by measuring the amplitude and the energy spectrum of the energy drop when Earth passes through Integral’s field of view. Once this is known, scientists can eventually try to connect the radiation to individual sources.

All the observations were very successful, as all the gamma-ray and X-ray instruments on board Integral (IBIS, SPI and JEM-X) recorded clear and unambiguous signals in line with expectations.

The Integral scientists are already proceeding with the analysis of the data. The aim is to ultimately understand the origin of the highest energy background radiation and, possibly, provide new clues on the history of growth of super-massive black holes since the early epochs of the Universe.

Original Source: ESA Portal

Posted on by Fraser Cain

What’s Up This Week – February 13 – February 19, 2006

Lunar halo. Image credit: Steve Mandel. Click to enlarge.
Monday, February 13 – Tonight is Full Moon. During the month of February the upper northern hemisphere is often heavy with snow. Native Indian tribes of the north and east called February’s Full Moon the Full Snow Moon. Some tribes also referred to this Moon as the Full Hunger Moon as artic weather conditions often made hunting and food gathering very unproductive.

Tonight let’s have a look at a pair of single stars that make up Gemini (the Twins): Castor and Pollux.

In Greek mythology, Castor and Pollux were fathered by the Greek god Zeus (Jupiter) who took the form of a swan and came upon a beautiful mortal woman. Pollux later grew up to become a skilled boxer and Castor, a master horseman. The two brothers were inseparable. It is said that they rescued the beautiful Helen from Troy, traveled with Jason and the Argonauts, and ultimately found themselves in a mortal battle with another pair of twin brothers over a beautiful woman. Pollux was so grief stricken at Castor’s death that he cried out to Zeus and offered up his own immortality in exchange for Castor’s life. Zeus took pity on the twins and placed them in the sky. You can see them tonight with your own eyes joined seemingly eternally together in Gemini.

As you observe this pair note that although Castor is almost half a magnitude fainter than Pollux, Bayer gave that star the title “Alpha Geminorum.” Which one do you think appears brighter? There’s more about both stars to come.

Tuesday, February 14 – Happy Valentine’s Day! Today is the birth date of Fritz Zwicky. Born in 1898, Zwicky was the first astronomer to identify supernovae as a separate class of objects. His insights also proposed the possibility of neutron stars. Among his many achievements, Zwicky catalogued galaxy clusters and designed jet engines. He also suggested the redshift displayed in the spectra of distant galaxies could be caused by something other than universal expansion.

Tonight’s lunar feature for telescopes and binoculars is crater Langrenus. Named for the Belgian engineer and mathematician Michel Florent van Langren, crater Langrenus is easily found along the terminator slightly south of central. At this time its 132 km expanse will appear shallow and display a luminous central peak.

Since you have your scope out, why not turn it towards one of the brightest double stars in the night sky – Alpha Geminorum. It’s true. One of the twins is a twin! Separated by a little more than 3 arc seconds, this true binary pair of 2nd magnitude stars make Castor a splendid study – even in the smallest scopes.

Wednesday, February 15 – Born on this day in 1564 was the man who “fathered” modern astronomy – Galileo Galilei. Almost 4 centuries ago, Galileo became the first scientist to use a telescope for astronomical purposes and his first study was the Moon. His words, “Most beautiful and admirable is it to see the Moon’s luminous form… At nearly thirty diameters – some 900 times greater in region – anyone can perceive that the Moon is not covered with a smooth and uniform surface but in fact reveals great mountainous shelves, deep cavities, and gorges just like those of the Earth,” still echo true today.

Tonight the tiny crater named for Galileo will be visible on the surface, but seeing it – even in a telescope – will be a challenge. Look to the fully illuminated western edge. Almost central and caught on the edge of Oceanus Procellarum, you will see a small, bright ring. This is crater Reiner. You will find Galileo just a short hop to the northwest as a tiny, washed out feature. What a shame the cartographers did not pick a more vivid feature to honor the great Galileo!

Galileo is noted for making many wondrous discoveries, but did you know that he may have been the first astronomer to see the Trapezium in M42? Galileo included three of the four stars in a sketch based on what is probably a low power (27x) view of the Great Nebula. Tonight celebrate that unheralded discovery by using the lowest possible magnification and the smallest telescope you can find to get the “Galileo-eye view” of the Trapezium.

Thursday, February 16 – Today celebrates the birth of Francois Arago. Born in 1786, Arago was an early and enthusiastic supporter of the wave theory of light. His scientific achievements were many – including the 1811 invention of the polariscope. Arago was also a practiced astronomer and wrote 4 volumes entitled Astronomie Populaire in the mid-1800s. Arago’s polariscope revealed that light could be organized in such a way as to cause photons to have a similar electromagnetic orientation. Polarized light viewed through his polariscope could come close to disappearing when the instrument was rotated. Many amateur astronomers use polarizing filters to reduce the amount of glare from the Moon, but did you know that even starlight can be polarized?

In celebration of Arago’s birth, why not go out and have a look at one such star – Merope in the Pleiades. As you observe Merope keep in mind that its light doesn’t begin polarized. In passing through the Merope Nebula, it becomes filtered. Try using a polarized filter and compare the view without.

On this day in 1948, Gerard Kuiper was celebrating the discovery of Miranda – one of Uranus’ moons. At magnitude 16, few of us will ever see Kuiper’s discovery for ourselves. With Uranus now close to the Sun (near Lambda Aquarii), even it will be hard to see!

Friday, February 17 – For SkyWatchers this morning, many of you will have the opportunity to watch the Moon occult bright Spica – Alpha Virginis. Be sure to check with IOTA for times and locales.

Early evening means dark skies, so let’s take the opportunity to revisit two of the three Messier open clusters in Auriga and compare them with the similar, but fainter, NGC 1893.

NGC 1893 is similar to M36 in size, but four times fainter. On a good night, a small telescope can resolve more than a dozen faint stars in this 13,000 light-year distant open cluster. To find it, look around 3 degrees southwest of M38 and west of M36. The three clusters form an even triangle in the sky. In large binoculars or a rich-field telescope, the trio can be seen together as nebulous mists sprinkled with faint stars. Remember this cluster is also four times more distant than the Messier objects it shares Auriga with. It is estimated to be 10 million years old and it’s still in the process of giving birth to new stars. Reflection nebula IC 410 is also part of the NGC 1893. See if you can spot it!

Saturday, February 18 – On this day in 1930, a young man named Clyde Tombaugh was very busy with some photographic plates taken with the Lowell Observatory’s 13″ telescope. His reward? The discovery of Pluto!

Clyde discovered Pluto on a set of plates centered on the star Delta Geminorum – Wasat – a star lying very near the path the Sun takes across the sky. While we can’t see Pluto tonight, we can study this fine 3.5 magnitude star and its disparate companion.

Once you’ve studied Wasat, you may notice Saturn gracing the early evening sky. As you observe Saturn’s magnificent ring system and four or five brightest moons, give some thought to distance and size. If our solar system was measured in units based on the Saturn-Sun distance – rather than Earth-Sun, Pluto would be 3.4 AUs from Sol. At 2274 kilometers in diameter, Pluto is less than half the size of Saturn’s largest satellite – Titan!

For deep sky, have a look at the rich open cluster NGC 2129. Located about a fingerwidth west of M35, at low power it may appear in the same field as Propus – 1 Geminorum. A rich-field scope or binoculars will frame M35 and NGC 2129 together.

Sunday, February 19 – Today is the birthday of Nicolas Copernicus. Born in 1473, Copernicus envisioned the modern solar system model which explained the retrograde motion of the outer planets. Considering this was well over 530 years ago, and in a rather unenlightened time, his revolutionary thinking is astounding. If you are up later, you can see the mighty crater named for Copernicus on the lunar surface almost central and west of the terminator.

But, before the Moon rises tonight, let’s turn our telescopes towards Saturn – one solar system body whose motion through the heavens exemplifies much of what Copernicus hoped his concept could explain! Among the “seven classical planets,” Saturn moves the slowest, taking almost two and a half years to move the thirty degrees related to each of the twelve “stations” planets pass through as they circle the ecliptic. Because of its slow pace, Saturn is often associated with “Chronos,” or Father Time, who wields his scythe and harvests a 30 year-long generation of humankind. Right now, Saturn is stationed in Cancer the Crab – one of the twelve “zodiacal,” or “animal signs” of the ecliptic. The Crab is joined with eleven other animals – preceded by neighboring Gemini, “the twin men,” and followed by Leo, “the solitary Lion.” By putting the Sun in the center of all this – rather than the Earth – Copernicus freed human thinking from the more ancient Ptolemaic system and allowed the solar Lion to stand at the center of things instead.

So, have another look at Saturn. Enjoy its low-contrast southern equatorial belt, subtly mottled blue polar region, and fine system of four easily seen satellites each moving much more rapidly around Saturn than the planet itself does around the Sun. Then think “Wow, that Copernicus guy would really have enjoyed seeing this!”

May all your journeys be at light speed… ~Tammy Plotner. Contibuting writer: Jeff Barbour @ astro.geekjoy.com

Posted on by Fraser Cain

Astrophoto: M-82 by Russell Croman

M-82 by Russell Croman
About two hundred million years ago, the latest encounter between M-82 and its nearby companion M-81 occurred in relative proximity to our planet- both are only about 11 million light year’s distant which is a mere stone’s away compared to the vastness of the universe. To any eyes that could have been a witness, the meeting would have seemed to happen in extreme slow motion because it took several million years from start to finish.

Nonetheless, M-82 was hugely altered, its outer arms stripped off, its star clouds excited into producing stars and exploding others at a rate so dizzying that matter was ejected and continues pouring in spectacular particle wind driven jets. These have a red, flame-like appearance and are estimated to be ten thousand light-years long. As a result, astronomers refer to M-82 as a starburst galaxy. Its exposed core is also a powerful source of x-rays – evidencing its runaway star activity.

This striking picture was taken by Russ Croman on February 3, 2005, from his Dimension Point Observatory in Mayhill, New Mexico and required almost five hours of combinded exposure. Russ’s instruments are quite sophisticated, for example, this image was made with his remote controlled twenty inch, f/8 RCOS Ritchey-Chr?tien telescope and an eleven mega-pixel SBIG astronomical camera.

Do you have photos you’d like to share? Post them to the Universe Today astrophotography forum or email them, and we might feature one in Universe Today.

Written by R. Jay GaBany

Posted on by Fraser Cain

Podcast: There Goes New Horizons

Artist illustration of New Horizons with Pluto and Charon. Image credit: NASA/JPL. Click to enlarge.
Listen to the interview: There Goes New Horizons (4.5 MB)

Or subscribe to the Podcast: universetoday.com/audio.xml

What’s a Podcast?

Fraser: Congratulations on the launch of New Horizons. That’s got to be a big relief.

Alan Stern: Yeah, it’s wonderful to have a spacecraft on the way.

Fraser: So you’ve got 9 years ahead until you reach Pluto. Can you describe the path the spacecraft’s going to take, and what you might be seeing along the way?

Stern: Sure I can. First, it’s easy to remember, we’ve got 9 years on the way to the 9th planet. Our trajectory takes us first to Jupiter for a gravity assist. And we will have closest approach to Jupiter on the 28th of February next year, 2007. Following that, we have a long coast out to Pluto. About 8 years worth. And then we begin the encounter in the early months of 2015.

Fraser: Now as I understand, you’re going to just be going right past Pluto, get some photos on the way, but you’re definitely not going to be able to stick around.

Stern: Well, we have a long encounter. It’s about 150 days of observations of the system on the way in. And then we’ll make some observations on the way out as well. We have 7 scientific instruments, so it’ll be a pretty intensive course of observations. I think it would be selling it short if I characterized it as taking a few pictures of Pluto.

Fraser: And you’re going to be able to do a close flyby of its moon as well?

Stern: Well, you know Pluto has 3 moons. We’re flying through the Pluto system with very specific targeting because there are specific events that we want to make happen. Like we want to make the Sun rise and set so we can study Pluto’s atmosphere; and make the Earth rise and set for similar reasons – for both Pluto and Charon. And so, as we go through the system, all of our closest approach distances are set by those constraints. But we have very good telescopic cameras, and they’ll be studying Pluto, its 3 known moons, and any other moons that we find between now and 2015.

Fraser: And I think that one of the exciting parts for a lot of people is just to see it in photographs up close, because right now, all you get to see are some blurry pixels from Hubble. But just getting some pretty pictures isn’t everything. What’s some of the science that you’ll be pulling from this mission?

Stern: Well, quite a bit. First, this is the first exploration of a fully new type of object – these so-called ice dwarf planets. And so our objectives are very broad. To map Pluto and all the Pluto objects in the system. To map the surface composition as well, so that for every pixel we have a spectrum to determine what things are made of. And to assay the structure and the composition of Pluto’s atmosphere. Those are our 3 main objectives. We’ve got about a dozen others. But unlike a mission like Cassini or Mars Reconnaissance Orbiter, where we’re going back to a target we have visited in the past several times, this time it’s a real first time exploration, so our objectives more have to do with the data sets that we want to collect, and the specific answers we’re answering. We expect to be surprised when going to a new type of object; it’s always been the history in this type of planetary exploration.

Fraser: Well, I guess that’s the thing. Each mission tends to come up with some surprises. Obviously you don’t know what things are going to surprise you, but do you have some hunches on some stuff that you might be finding out?

Stern: We’re very interested to know the structure of Pluto’s atmosphere; what its dominant constituent is. We think we know from the ground, but we’re not sure. We have a hypothesis that Pluto’s surface will be young because the atmosphere is rapidly escaping. It’s removed the ancient terrains by escaping into space. There may be some evidence that Pluto is internally active, so we’ll be looking for evidence of that. For example, in the form of geysers or volcanoes; recent tectonic features, or flows. Similarly on Pluto’s largest moon, Charon, we’re going to be looking for ancient terrains; we’re going to be looking to count craters that tell us the history of the ancient Kuiper belt. And we’re going to be looking to see if we find ammonium hydrates, which have been detected at unfortunately tantalizingly low signal to noise by ground-based observers. But it would say a lot about small worlds.

Fraser: I heard recently that Pluto’s colder than people were expecting. That Charon is actually warmer. Will you be able to do some followup on this?

Stern: I’ll say a word or two about that, because I saw that reported in the press. It’s an incorrect story, in fact, exactly that result was obtained in the 1990s by two groups, published both in Science and the Astronomical Journal. So, I think the press release was flawed. Those results had been obtained about 12 years before.

Fraser: Not new… okay.

Stern: It’s correct, Pluto’s colder than Charon. It’s not colder than expected, because we’ve expected since the early 1990s. Pluto’s exactly the temperature that was found.

Fraser: Right, well I guess the hypothesis though, is that Charon is the result of a large object slamming into Pluto and turning it into a moon, sort of like our own Moon was created.

Stern: That’s right, but it has nothing to do with the surface temperature.

Fraser: Once the spacecraft gets past Pluto, and heads out, where do you want to go next?

Stern: Well, our secondary objective of the mission, and to a lot of scientists, it’s the primary objective of the mission is to see Kuiper Belt objects; the building blocks out of which Pluto and Charon were made. And so, our plan is to go onto one or two, or possibly even more Kuiper belt objects in the years following the Pluto encounter as we move further outward in the trans neptunian region.

Fraser: And I guess that’ll tell you how Pluto might be similar or different to those objects.

Stern: Right, exactly, we want to look and understand the composition of these bodies, learn their histories, and see whether they have atmospheres, the nature of small satellites around them. Count craters on their surfaces to compare to the bombardment of Pluto, and understand the accretion of these bodies.

Fraser: And if you had more time for a longer mission, or more advanced technology that you could put into the spacecraft, more powerful propulsion, what were some stuff you wished you could have added onto the mission if you had more budget?

Stern: I don’t really have any thoughts about the propulsion, and other fantasy land things. We built the mission when we could, and of course in the future decades or centuries, you could always do it, but it was time to do a Pluto mission. You have to build it with the best technology available. If spaceflight’s typically about the very real world engineering problems, were you have constraints of budget, time, mass you can send, things like that. But if we could suspend all belief, and remove those, it would have been very much to our liking to have flown a longer wave infrared spectrometer, so we could look for things like oxides of sulphur on the surface of Pluto and other bodies that we fly by. Perhaps a magnetometer as well.

Posted on by Fraser Cain

The Moon has Alps Too

The lunar Alps border the moon’s Sea of Rains. Image credit: NASA
It’s only a matter of time. One day, winter Olympics will be held on the moon.

The moon’s dust-covered slopes are good places to ski. There’s plenty of powder, moguls and, best of all, low-gravity. With only 1/6th g holding them down, skiers and snowboarders can do tricks they only dreamed of doing on Earth. How about an octuple-twisting quadruple backflip? Don’t worry. Crashes happen in slow-motion, so it won’t hurt so much to wipe out.

And there’s a perfect spot for the Olympic Village: the crater Plato. Most people don’t know it, but Plato of ancient Greece was not only a philosopher, but also an Olympic champion. Twice he won the pankration competition?a grueling mix of boxing and wrestling. A crater named after Plato sounds like a good place for Olympic athletes to stay. The site is flat-bottomed, filled with raw materials for building stadia and habitats, and like Torino, Italy, the site of this year’s games, Plato is near the Alps.

That is, the lunar Alps.

The lunar Alps are a range of mountains on the moon named after the Alps of Europe. They are similar to their Earthly counterparts in height, breath and spectacle. Since the modern Olympics began in 1896, most of the winter games have been held in the Alps. Why should the moon be different?

You can see the lunar Alps using a small backyard telescope. This week is an excellent time to try: Step outside at sundown and look up at the moon. The Olympic Village, crater Plato, is a conspicuous dark oval on the northern shore of Mare Imbrium, the “Sea of Rains.” Your unaided eye is sufficient to see it.

Next, train your telescope on Plato. The Alps begin there. They stretch around the rim of the Sea of Rains from Plato through the spectacular Alpine Valley to towering Mont Blanc. Amateur astronomer Alan Friedman of Buffalo, New York, used a 10-inch telescope to take this picture of the scene.***image4:left***

Although the two Alps look much alike, they formed in different ways:

The Alps of Earth grew over a period of millions of years. Powered by plate tectonics, sections of Earth’s crust pushed together, squeezing the land to produce jagged mountains. The range stretches from France through Italy all the way to Albania; the tallest peak is Mont Blanc, 15,700 ft or 4800 m high.

The Alps of the moon were formed in an instant some 4 billion years ago when a huge asteroid struck. The collision blasted out the Sea of Rains, which, contrary to its name, is a big crater, not a big sea. The Alps are “splash” from the impact.

In those early days, lunar Alps were probably as jagged and rough as the Alps of Earth. But in eons that followed, meteoroids relentlessly pounded the moon, smashing rocks into dust and blunting the sharp edges of mountain peaks. Today’s lunar Alps are a bit shorter (the moon’s Mont Blanc is only 11,800 ft or 3600 m high) and a lot smoother than their terrestrial counterparts?perfect for Olympics.

In the weeks ahead, Science@NASA will publish a series of stories exploring the physics of low-gravity Olympics. Is an octuple-twisting quadruple backflip really possible? Should snowboarders be allowed to pilot lunar landers? How is a bobsled like a spaceship? Stay tuned for the answers to these questions and others?with exclusive video from Olympic athletes.

Let the Games begin!

Original Source: NASA News Release

Posted on by Fraser Cain

Channels and Pits on Mars

Perspective view of Phlegethon Catena. Image credit: ESA Click to enlarge
This image, taken by the High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express spacecraft, show pits and tectonic ‘grabens’ in the Phlegethon Catena region of Mars.

The HRSC obtained this image during orbit 1217 with a ground resolution of approximately 11.9 metres per pixel. The scene shows the region of Phlegethon Catena, centred at approximately 33.9? South and 253.1? East.

Located south-east of the Alba Patera volcano, Phlegethon Catena is a region exhibiting a high density of tectonic grabens, which are blocks of terrain that have dropped relative to their surroundings as a result of a geological extension of the crust.

In the colour image, this swarm of grabens trends roughly north-east to south-west, with individual widths ranging from approximately one half to ten kilometres.

The series of closely spaced depressions that exhibit a similar orientation to the grabens is described by the term ‘catena’.

These depressions are rimless, circular to elliptical and range from roughly 0.3 to 2.3 kilometres across.

The grabens may have formed as the result of stresses associated with the formation of Alba Patera, which rises three to four kilometres above the surrounding plains, or the Tharsis rise to the south, which reaches up to ten kilometres high.

It is unclear what process is responsible for the chain of depressions.

One possibility is the collapse of the surface due to the removal of subsurface materials, while other suggestions include that tension cracks may have formed in the subsurface and caused subsequent collapse.

The colour scenes have been derived from the three HRSC-colour channels and the nadir channel. The perspective views have been calculated from the digital terrain model derived from the stereo channels.

The 3D anaglyph image was calculated from the nadir and one stereo channel. Image resolution has been decreased for use on the internet.

Original Source: ESA Mars Express

Posted on by Fraser Cain

Podcast: There Goes New Horizons

Take a look through any book on our Solar System, and you’ll see beautiful photographs of every planet – except one. Eight of our nine planets have been visited up close by a spacecraft, and we’ve got the breathtaking photos to prove it. Pluto’s the last holdout, revealing just a few fuzzy pixels in even the most powerful ground and space-based telescopes. But with the launch of New Horizons in January, bound to arrive at Pluto in 9 years, we’re one step closer to completing our planetary collection – and answering some big scientific questions about the nature of objects in the Kuiper Belt. Alan Stern is the Executive Director of the Space Science and Engineering Division, at the Southwest Research Institute. He’s New Horizon’s Principal Investigator.
Continue reading “Podcast: There Goes New Horizons”

Posted on by Fraser Cain

A Closer Look at Telesto

A false colour view of the Trojan moon Telesto. Image credit: NASA/JPL/SSI Click to enlarge
These views show surface features and color variation on the Trojan moon Telesto. The smooth surface of this moon suggests that, like Pandora, it is covered with a mantle of fine, dust-sized icy material.

The monochrome image was taken in visible light (see PIA07696). To create the false-color view, ultraviolet, green and infrared images were combined into a single black and white picture that isolates and maps regional color differences. This “color map” was then superposed over a clear-filter image. The origin of the color differences is not yet understood, but may be caused by subtle differences in the surface composition or the sizes of grains making up the icy soil.

Tiny Telesto is a mere 24 kilometers (15 miles) wide.

All images were acquired with the Cassini spacecraft narrow-angle camera on Dec. 25, 2005 at a distance of approximately 20,000 kilometers (12,000 miles) from Telesto and at a Sun-Telesto-spacecraft, or phase, angle of 58 degrees. Image scale is 118 meters (387 feet) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, 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, D.C. 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, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Mega Solar Systems Discovered

An illustration comparing the size of a gargantuan star and its dusty disk with our solar system. Image credit: NASA/JPL Click to enlarge
NASA’s Spitzer Space Telescope has identified two huge “hypergiant” stars circled by monstrous disks of what might be planet-forming dust. The findings surprised astronomers because stars as big as these were thought to be inhospitable to planets.

“These extremely massive stars are tremendously hot and bright and have very strong winds, making the job of building planets difficult,” said Joel Kastner of the Rochester Institute of Technology in New York. “Our data suggest that the planet-forming process may be hardier than previously believed, occurring around even the most massive stars that nature produces.”

Kastner is first author of a paper describing the research in the Feb. 10 issue of Astrophysical Journal Letters.

Dusty disks around stars are thought to be signposts for present or future planetary systems. Our own sun is orbited by a thin disk of planetary debris, called the Kuiper Belt, which includes dust, comets and larger bodies similar to Pluto.

Last year, astronomers using Spitzer reported finding a dust disk around a miniature star, or brown dwarf, with only eight one-thousandths the mass of the sun ( http://www.spitzer.caltech.edu/Media/happenings/20051129/). Disks have also been spotted before around stars five times more massive than the sun.

The new Spitzer results expand the range of stars that sport disks to include the “extra large.” The infrared telescope detected enormous amounts of dust around two positively plump stars, R 66 and R 126, located in the Milky Way’s nearest neighbor galaxy, the Large Magellanic Cloud. Called hypergiants, these blazing hot stars are aging descendents of the most massive class of stars, referred to as “O” stars. They are 30 and 70 times the mass of the sun, respectively. If a hypergiant were located at the sun’s position in our solar system, all the inner planets, including Earth, would fit comfortably within its circumference.

Astronomers estimate that the stars’ disks are also bloated, spreading all the way out to an orbit about 60 times more distant than Pluto’s around the sun. The disks are probably loaded with about ten times as much mass as is contained in the Kuiper Belt. Kastner and his colleagues say these dusty structures might represent the first or last steps of the planet-forming process. If the latter, then the disks can be thought of as enlarged versions of our Kuiper Belt.

“These disks may be well-populated with comets and other larger bodies called planetesimals,” said Kastner. “They might be thought of as Kuiper Belts on steroids.”

Spitzer detected the disks during a survey of 60 bright stars thought to be wrapped in spherical cocoons of dust. According to Kastner, R 66 and R 126 “stuck out like sore thumbs” because their light signatures, or spectra, indicated the presence of flattened disks. He and his team believe these disks whirl around the hypergiant stars, but they say it is possible the giant disks orbit unseen, slightly smaller companion stars.

A close inspection of the dust making up the disks revealed the presence of sand-like planetary building blocks called silicates. In addition, the disk around R 66 showed signs of dust clumping in the form of silicate crystals and larger dust grains. Such clumping can be a significant step in the construction of planets.

Stars as massive as R 66 and R 126 don’t live very long. They burn through all of their nuclear fuel in only a few million years, and go out with a bang, in fiery explosions called supernovae. Their short life spans don’t leave much time for planets, or life, to evolve. Any planets that might crop up would probably be destroyed when the stars blast apart.

“We do not know if planets like those in our solar system are able to form in the highly energetic, dynamic environment of these massive stars, but if they could, their existence would be a short and exciting one,” said Charles Beichman, an astronomer at NASA’s Jet Propulsion Laboratory and the California Institute of Technology, both in Pasadena.

Other authors of this work include Catherine L. Buchanan of the Rochester Institute of Technology, and B. Sargent and W. J. Forrest of the University of Rochester, N.Y.

The Jet Propulsion Laboratory manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech. JPL is a division of Caltech. Spitzer’s infrared spectrograph, which made the new observations, was built by Cornell University, Ithaca, N.Y. Its development was led by Jim Houck of Cornell.

An artist concept of a hypergiant and its disk, plus additional graphics and information, are available at http://www.spitzer.caltech.edu/spitzer.

Original Source: NASA News Release

Posted on by Fraser Cain

Hubble View of a Pinwheel-Shaped Galaxy

Spiral galaxy NGC 1309. Image credit: Hubble Click to enlarge
Looking like a child’s pinwheel ready to be set a spinning by a gentle breeze, this dramatic spiral galaxy is one of the latest viewed by NASA’s Hubble Space Telescope. Stunning details of the face-on spiral galaxy, cataloged as NGC 1309, are captured in this color image.

Recent observations of the galaxy taken in visible and infrared light come together in a colorful depiction of many of the galaxy’s features. Bright blue areas of star formation pepper the spiral arms, while ruddy dust lanes follow the spiral structure into a yellowish central nucleus of older-population stars. The image is complemented by myriad far-off background galaxies.

However, this galaxy image is more than just a pretty picture. It is helping astronomers to more accurately measure the expansion rate of the universe. NGC 1309 was home to supernova SN 2002fk, whose light reached Earth in September 2002. This supernova event, known as a Type Ia, resulted from a white dwarf star accreting matter from its companion in a binary star system. When the white dwarf collected enough mass and was no longer able to support itself, the star detonated, becoming the brightest object in the galaxy for several weeks.

Nearby Type Ia supernovae like SN 2002fk in NGC 1309 are used by astronomers to calibrate distance measures in the universe. By comparing nearby Type Ia supernovae to more distant ones, they can determine not only that the universe is expanding, but that this expansion is accelerating. However, this method only works if the distance to the host galaxies is known extremely well.

That’s where the Hubble Telescope comes into play. Since NGC 1309 is relatively close to us, the high resolution of Hubble’s Advanced Camera for Surveys can help accurately determine the distance to the galaxy by looking at the light output of a particular type of variable star called a Cepheid variable. Cepheids are well studied in our own galaxy, and vary regularly in brightness at a rate that is directly related to their total intrinsic brightness. By comparing their variation rate with how bright they appear, astronomers can deduce their distance. In this way, the Cepheids in NGC 1309 allow astronomers to accurately measure the distance to NGC 1309, and thus to SN 2002fk. The expansion of the universe was discovered by Edwin Hubble, the Hubble Space Telescope’s namesake, nearly a century ago, but the accelerating expansion is a recent discovery which has interesting consequences for cosmological models.

These Hubble images were taken in August and September 2005. NGC 1309 resides 100 million light-years (30 Megaparsecs) from Earth. It is one of about 200 galaxies that make up the Eridanus group of galaxies.

Original Source: Hubble News Release