Posted on by Nancy Atkinson

Would Life Form Differently Around Cool Stars?

This artist's conception shows a young, hypothetical planet around a cool star. Credit: JPL

[/caption]
“Life as we know it” seems to be the common caveat in our search for other living things in the Universe. But there’s also the possibility of life “as we don’t know it.” A new study from NASA’s Spitzer Space Telescope hints that planets around stars cooler than our sun might possess a different mix of potentially life-forming, or “prebiotic,” chemicals. While life on Earth is thought to have arisen from a hot soup of different chemicals, would the same life-generating mix come together around other stars with different temperatures? (And should we call it ‘The Gazpacho Effect?’) “Prebiotic chemistry may unfold differently on planets around cool stars,” said Ilaria Pascucci, lead author of the new study.

Pascussi and her team used Spitzer to examine the planet-forming disks around 17 cool and 44 sun-like stars. The stars are all about one to three million years old, an age when planets are thought to be forming. The astronomers specifically looked for ratios of hydrogen cyanide to a baseline molecule, acetylene. Using Spitzer’s infrared spectrograph, an instrument that breaks light apart to reveal the signatures of chemicals, the researchers looked for a prebiotic chemical, called hydrogen cyanide, in the planet-forming material swirling around the stars. Hydrogen cyanide is a component of adenine, which is a basic element of DNA. DNA can be found in every living organism on Earth.

The researchers detected hydrogen cyanide molecules in disks circling 30 percent of the yellow stars like our sun — but found none around cooler and smaller stars, such as the reddish-colored “M-dwarfs” and “brown dwarfs” common throughout the universe.

Cool Stars May Have Different Prebiotic Chemical Mix
Cool Stars May Have Different Prebiotic Chemical Mix

The team did detect their baseline molecule, acetylene, around the cool stars, demonstrating that the experiment worked. This is the first time that any kind of molecule has been spotted in the disks around cool stars.

“Perhaps ultraviolet light, which is much stronger around the sun-like stars, may drive a higher production of the hydrogen cyanide,” said Pascucci.

Young stars are born inside cocoons of dust and gas, which eventually flatten to disks. Dust and gas in the disks provide the raw material from which planets form. Scientists think the molecules making up the primordial ooze of life on Earth might have formed in such a disk. Prebiotic molecules, such as adenine, are thought to have rained down to our young planet via meteorites that crashed on the surface.

“It is plausible that life on Earth was kick-started by a rich supply of molecules delivered from space,” said Pascucci.

The findings have implications for planets that have recently been discovered around M-dwarf stars. Some of these planets are thought to be large versions of Earth, the so-called super Earths, but so far none of them are believed to orbit in the habitable zone, where water would be liquid. If such a planet is discovered, could it sustain life?

Astronomers aren’t sure. M-dwarfs have extreme magnetic outbursts that could be disruptive to developing life. But, with the new Spitzer results, they have another piece of data to consider: these planets might be deficient in hydrogen cyanide, a molecule thought to have eventually become a part of us.

Said Douglas Hudgins, the Spitzer program scientist at NASA Headquarters, Washington, “Although scientists have long been aware that the tumultuous nature of many cool stars might present a significant challenge for the development of life, this result begs an even more fundamental question: Do cool star systems even contain the necessary ingredients for the formation of life? If the answer is no then questions about life around cool stars become moot.”

Or, could life form differently around cooler stars from anything we know?

Source: JPL

Posted on by Anne Minard

New Image Reveals M33 is Bigger Than Thought (and it’s Headed Our Way)

The Triangulum Galaxy. Image credit: NASA/JPL-Caltech/University of Arizona

[/caption]

 

 

 

 

 

 

 

 

 

 

NASA’s Spitzer Space Telescope has captured this new image of M33, also known as the Triangulum Galaxy, and released it as part of the “Around the World in 80 Telescopes” event for the International Year of Astronomy.

Besides the pretty colors, the new image reveals something else about M33: it’s more than meets the eye.

M33 is located about 2.9 million light-years away in the constellation Triangulum. It is a member of what’s known as our Local Group of galaxies. Along with our own Milky Way and Andromeda, the group of about 50 galaxies travels together in the universe, bound to one another by gravity. In fact, M33 is one of the few galaxies that is moving toward the Milky Way despite the fact that space is expanding, causing most galaxies in the universe to grow farther and farther apart. 

The new image reveals M33 to be surprising large – bigger than its visible-light appearance would suggest. With its ability to detect cold, dark dust, Spitzer can see emission from cooler material well beyond the visible range of M33’s disk. Exactly how this cold material moved outward from the galaxy is still a mystery, but winds from giant stars or supernovas may be responsible. 

The image is a three-color composite showing infrared observations from two of Spitzer instruments. Stars appear as glistening blue gems (several of which are actually foreground stars in our own galaxy), while dust rich in organic molecules glows green. The diffuse orange-red glowing areas indicate star-forming regions, while small red flecks outside the spiral disk of M33 are probably distant background galaxies. 

As for the technical details, the blue parts of the image represents combined 3.6- and 4.5-micron light, and green shows light of 8 microns, both captured by Spitzer’s infrared array camera. Red is 24-micron light detected by Spitzer’s multiband imaging photometer.

Source: NASA’s Spitzer site

Posted on by Nancy Atkinson

The Two Shall Become One (Galaxy, that is)

This image of a pair of colliding galaxies called NGC 6240 shows them in a rare, short-lived phase of their evolution just before they merge into a single, larger galaxy. Image credit: NASA/JPL-Caltech/STScI-ESA

[/caption]
An imminent collision of biblical proportions has been captured by the Hubble and Spitzer Space Telescopes. The image here offers a rare view of a collision about to happen between the cores of two merging galaxies, each powered by a black hole with millions of times the mass of the sun. Already this union is considered to be one galaxy: NGC 6240, located 400-million light years away in the constellation Ophiuchus. Millions of years ago, each core was the dense center of its own galaxy before the two galaxies collided and ripped each other apart. Now, these cores are approaching each other at tremendous speeds and preparing for the final cataclysmic collision. They will crash into each other in a just a few million years.

“One of the most exciting things about the image is that this object is unique,” said Stephanie Bush of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass., lead author of a new paper describing the observation in an upcoming issue of the Astrophysical Journal. “Merging is a quick process, especially when you get to the train wreck that is happening. There just aren’t many galactic mergers at this stage in the nearby universe.”

Download and extra-large version of this image here.

It combines visible light from NASA’s Hubble Space Telescope and infrared light from Spitzer. It catches the two galaxies during a rare, short-lived phase of their evolution, when both cores of the interacting galaxies are still visible but closing in on each other fast.

NGC 6240 is already putting out huge amounts of infrared light, an indication that a burst of star formation is underway. The extra infrared radiation is common in interacting galaxies; as the two galaxies interact, dust and gas swept up by the collision form a burst of new stars that give off infrared light. Such galaxies are called luminous infrared galaxies. Spitzer’s infrared array camera can image the extra heat from newly formed stars, even though their visible light is obscured by thick dust clouds around them.

The blob-like shape of the galaxy is due to the sustained violence of the collision. Streams of millions of stars are being ripped off the galaxy, forming wispy “tidal tails” that lead off NGC 6240 in several directions. But things are about to get even more violent as the main event approaches and the two galactic cores meld into one.

In the center of NGC 6240, the two black holes in the cores will whip up a frenzy of radiation as they careen towards one another head-on, likely transforming the galaxy into a monster known as an ultra-luminous infrared galaxy, thousands of times as bright in infrared as our Milky Way.

Another fascinating aspect of this rare object is that no two galactic mergers are the same. “Not only are there few objects at this stage, but each object is unique because it came from different progenitor galaxies,” said Bush. “These observations give us another layer of information about this galaxy, and galactic mergers in general.”

Infrared light taken by Spitzer’s infrared array camera at 3.6 and 8.8 microns (red) shows cold dust and radiation from star formation; visible light from Hubble (green and blue) shows hot gas and stars.

Source: JPL

Posted on by Anne Minard

Stars at Milky Way Core ‘Exhale’ Carbon, Oxygen

Carbon exists only in a fine-tuned universe( 'Cat's Eye' Planetary Nebula)
Cat's Eye Nebula. Researchers have found carbon and oxygen in dusty planetary nebulae surrounding stars at the center of the Milky Way. Credit: NASA/JPL-Caltech/J. Hora (Harvard-Smithsonian CfA

[/caption]

Carbon and oxygen have been spotted in the dust around stars in the center of the Milky Way galaxy, suggesting that the stars have undergone recent disruptions of some kind — and hinting how stars can send heavy elements — like oxygen, carbon, and iron — out across the universe, paving the way for life.

Scientists have long expected to find carbon-rich stars in our galaxy because we know that significant quantities of carbon must be created in many such stars. But carbon had not previously shown up in the clouds of gas around these stars, said Matthew Bobrowsky, an astrophysicist at the University of Maryland and a co-author of a new study reporting the discovery.

“Based on our findings, this is because medium-sized stars rich in carbon sometimes keep that carbon hidden until very near the end of their stellar lives, releasing it only with their final ‘exhalations’,” explained Bobrowsky.

The new results appear in the February issue of the journal Astronomy and Astrophysics.

Bobrowsky and his team, led by J. V. Perea-Calderón at the European Space Astronomy Centre in Madrid, Spain, used the Spitzer Space Telescope to view each star and its surrounding clouds of dust and particles, called a planetary nebulae. The researchers measured the light emitted by the stars and the surrounding dust and were able to identify carbon compounds based on the wavelengths of light emitted by the stars. Looking in an area at the center of the Milky Way called the “Galactic Bulge,” the team observed 26 stars and their planetary nebulae and found 21 with carbon “signatures.”

But the scientists did not just find carbon around these stars; they also found oxygen in these 21 dust clouds, revealing a surprising mixture of ingredients for space dust. They report in their paper that this is likely due to a thermal pulse where a wave of high-pressure gas mixes layers of elements like carbon and oxygen and spews them out into the surrounding cloud.

The finding of carbon and oxygen in the dust clouds surrounding stars suggests a recent change of chemistry in this population of stars, according to the authors.

“Stars in the center of the Milky Way are old and ‘metal-rich’ with a high abundance of heavy elements,” Bobrowsky said. “They are different in chemical composition than those found in the disc, farther out from the center.”

Studying the chemistry of the stars helps scientists learn how the matter that makes up our earth and other planets in our galaxy left its stellar birthplaces long ago. 

As a star burns hotter and hotter, the hydrogen gas that originally made up almost all of its mass is converted, through nuclear fusion, first to helium, and then to progressively heavier elements. The hottest region in the core fuses together the heaviest elements. And these can reach the surface of the star only when its life is almost over.

“The Big Bang produced only hydrogen and helium,” Bobrowsky said. “Heavier elements like carbon and oxygen only come from getting ‘cooked up’ in stars. Nuclear reactions in stars created the heavier elements found in ‘life as we know it’.”

In the last 50,000 years of their 10 billion-year lives, sun-sized stars expel carbon atoms along with hydrogen and helium to form a surrounding cloud of gas that soon disperses into space, perhaps to eventually become the stuff of new stars, solar systems, or perhaps even life on some earth-like planet. Much larger stars expel their heavier matter in massive explosions called supernovae.

“All the heavy elements [which astronomers call ‘metals,’ and include all elements heavier than hydrogen and helium] on Earth were created by nuclear fusion reactions in previous generations of stars,” said Bobrowsky. “Those earlier stars expelled those elements into space and then our solar system formed out of that gas containing all the heavy elements that we now find in Earth and in life on Earth.”

LEAD IMAGE CAPTION: Cat’s Eye Nebula. Researchers have found carbon and oxygen in dusty planetary nebulae surrounding stars at the center of the Milky Way. Credit: NASA/JPL-Caltech/J. Hora (Harvard-Smithsonian CfA)

Source: Astronomy & Astrophysics and Spitzer, via AAS

Posted on by Nancy Atkinson

Hubble, Spitzer Collaborate for Stunning Panorama of Galactic Center

Galactic center in unprecedented detail.Credit for Hubble image: NASA, ESA, and Q.D. Wang (University of Massachusetts, Amherst)

[/caption]

Two of the biggest space telescopes have combined forces to create a HUGE panorama of the center of the Milky Way galaxy. This sweeping, composite color panorama is the sharpest infrared picture ever made of the Galactic core. Revealed in the image are a new population of massive stars and new details of complex structures in the hot gas and dust swirling around, created by solar winds and supernova explosions. The image shows an area about 300 light-years across. Click here for options in seeing this image in small, medium or super-sized extra large resolution! Click here for a stunning movie showing the location and more detail of this image in visible light. Astronomers at the American Astronomical Society meeting pointed out the actual galactic center is in the large white region near the lower right side of the image. If you need something to keep you occupied for awhile, try counting the number of stars in this image!

More about this image…

This image provides insight into how massive stars form and influence their environment in the often violent nuclear regions of other galaxies. This view combines the sharp imaging of the Hubble Space Telescope’s Near Infrared Camera and Multi-Object Spectrometer (NICMOS) with color imagery from a previous Spitzer Space Telescope survey done with its Infrared Astronomy Camera (IRAC). The Galactic core is obscured in visible light by intervening dust clouds, but infrared light penetrates the dust. The spatial resolution of NICMOS corresponds to 0.025 light-years at the distance of the galactic core of 26,000 light-years. Hubble reveals details in objects as small as 20 times the size of our own solar system. The NICMOS images were taken between February 22 and June 5, 2008.

Source: HubbleSite

Posted on by Ian O'Neill

Powerful Rivers of Gas Imaged Around Star-Forming Swan Nebula

An infrared view of M17 (the Swan Nebula), a turbulent star-making cloud. (NASA/JPL-Caltech/Univ. of Wisc.)

[/caption]

The turbulent and dynamic Swan Nebula (M17) has been imaged by NASA’s Spitzer Space Telescope, producing the clearest view yet of the star-forming region. Within the twisted cloud of gas and dust, violent stellar winds constantly blast the medium, generating flows around stars, creating vast bow shocks. A few massive stars in the centre of M17 are the main source of the relentless stellar “rivers” of gas, immersing smaller stars in the the flow, acting like stationary rocks on a riverbed…

This new observing campaign by Spitzer (an infrared telescope that has been in Earth orbit since 2003, and is expected to be operational until 2009), has imaged the M17 nebula with unprecedented clarity. Although it is a known fact that stellar winds inside star-forming regions generate dynamic features such as bow shocks, you cannot put a price on actually seeing these structures in an infrared image (pictured top). From analysis of these Spitzer results, Matt Povich of the University of Wisconsin has published a paper describing these new findings in the December 10th issue of the Astrophysical Journal.

“The stars are like rocks in a rushing river,” said Povich when describing the scene. “Powerful winds from the most massive stars at the center of the cloud produce a large flow of expanding gas. This gas then piles up with dust in front of winds from other massive stars that are pushing back against the flow.”

The Swan Nebula can be found in the constellation of Sagittarius, some 6000 light years away. It is a very active star-forming cloud where powerful stellar winds are eroding away the dust, clearing the region. Driving this mechanism are a group of massive stars exceeding 40 times the mass, and 100,000–1 million times the brightness, of the Sun. The stellar winds bullying smaller stars and blowing away the clouds of dust in the middle of the nebula have flow velocities exceeding 7.2 million km/hr (4.5 million mi/hr). To put this in perspective, the fast solar wind (the fastest component of our Sun’s two-component solar wind) reaches a maximum velocity of 2.8 million km/hr (1.7 million mi/hr); the stellar winds inside the Swan are 2.5 times more powerful.

So what’s the result of this powerful stellar wind engine in M17? A very obvious cavity is created inside the nebula, a process thought to spark the birth of new stars. This stellar nursery is fuelled by the compression of the edge of the cavity, producing bow shocks around anything that is relatively stationary (i.e. other stars). The direction of the bow shocks provide information about the direction of the stellar winds.

Povich studies another star forming region called RCW 49 in addition to M17, picking out the glowing gases generated inside the shock fronts maintained by the flow of stellar flows. Spitzer turns out to be the perfect tool to peer deep into nebulae, picking out the infrared emissions from bow shocks, mapping them.

“The gas being lit up in these star-forming regions looks very wispy and fragile, but looks can be deceiving,” co-author Robert Benjamin added. “These bow shocks serve as a reminder that stars aren’t born in quiet nurseries but in violent regions buffeted by winds more powerful than anything we see on Earth.”

Further observation campaigns like this one will ultimately help astronomers understand how stellar systems, like our Solar System, form out of the violence of stellar birth.

Source: NASA, Physorg.com

Posted on by Nancy Atkinson

An Inside Look at Comet Holmes

The astronomy world buzzed in the Fall of 2007 when Comet Holmes – a normally humdrum, run-of-the-mill comet — unexpectedly flared and erupted. Its coma of gas and dust expanded away from the comet, extending to a volume larger than the Sun. Professional and amateur astronomers around the world turned their telescopes toward the spectacular event. Everyone wanted to know why the comet had suddenly exploded. The Hubble Space Telescope observed the comet, but provided few clues. And now, observations taken of the comet after the explosion by NASA’s Spitzer Space Telescope deepen the mystery, showing oddly behaving streamers in the shell of dust surrounding the nucleus of the comet. The data also offer a rare look at the material liberated from within the nucleus. “The data we got from Spitzer do not look like anything we typically see when looking at comets,” said Bill Reach of NASA’s Spitzer Science Center at Caltech.

Every six years, comet 17P/Holmes speeds away from Jupiter and heads inward toward the sun, traveling the same route typically without incident. However, twice in the last 116 years, in November 1892 and October 2007, comet Holmes exploded as it approached the asteroid belt, and brightened a millionfold overnight.

In an attempt to understand these odd occurrences, astronomers pointed NASA’s Spitzer Space Telescope at the comet in November 2007 and March 2008. By using Spitzer’s infrared spectrograph instrument, Reach and his colleagues were able to gain valuable insights into the composition of Holmes’ solid interior. Like a prism spreading visible-light into a rainbow, the spectrograph breaks up infrared light from the comet into its component parts, revealing the fingerprints of various chemicals.

The Spitzer Space Telescope. Credit: NASA
The Spitzer Space Telescope. Credit: NASA

In November of 2007, Reach noticed a lot of fine silicate dust, or crystallized grains smaller than sand, like crushed gems. He noted that this particular observation revealed materials similar to those seen around other comets where grains have been treated violently, including NASA’s Deep Impact mission, which smashed a projectile into comet Tempel 1; NASA’s Stardust mission, which swept particles from comet Wild 2 into a collector at 13,000 miles per hour (21,000 kilometers per hour), and the outburst of comet Hale-Bopp in 1995.

“Comet dust is very sensitive, meaning that the grains are very easily destroyed, said Reach. “We think the fine silicates are produced in these violent events by the destruction of larger particles originating inside the comet nucleus.”

When Spitzer observed the same portion of the comet again in March 2008, the fine-grained silicate dust was gone and only larger particles were present. “The March observation tells us that there is a very small window for studying composition of comet dust after a violent event like comet Holmes’ outburst,” said Reach.

Comet Holmes not only has unusual dusty components, it also does not look like a typical comet. According to Jeremie Vaubaillon, a colleague of Reach’s at Caltech, pictures snapped from the ground shortly after the outburst revealed streamers in the shell of dust surrounding the comet. Scientists suspect they were produced after the explosion by fragments escaping the comet’s nucleus.

In November 2007, the streamers pointed away from the sun, which seemed natural because scientists believed that radiation from the sun was pushing these fragments straight back. However, when Spitzer imaged the same streamers in March 2008, they were surprised to find them still pointing in the same direction as five months before, even though the comet had moved and sunlight was arriving from a different location. “We have never seen anything like this in a comet before. The extended shape still needs to be fully understood,” said Vaubaillon.

He notes that the shell surrounding the comet also acts peculiarly. The shape of the shell did not change as expected from November 2007 to March 2008. Vaubaillon said this is because the dust grains seen in March 2008 are relatively large, approximately one millimeter in size, and thus harder to move.

“If the shell was comprised of smaller dust grains, it would have changed as the orientation of the sun changes with time,” said Vaubaillon. “This Spitzer image is very unique. No other telescope has seen comet Holmes in this much detail, five months after the explosion.”

“Like people, all comets are a little different. We’ve been studying comets for hundreds of years — 116 years in the case of comet Holmes — but still do not really understand them,” said Reach. “However, with the Spitzer observations and data from other telescopes, we are getting closer.”

Source: Spitzer Press Release

Posted on by Nancy Atkinson

Star Blasting Water From Its Surroundings

A jet of gas firing out of a very young star can be seen ramming into a wall of material in this infrared Spitzer image. Image credit: NASA/JPL-Caltech/Harvard-Smithsonian CfA

[/caption]

The Spitzer Space Telescope has spied water in a cloud of gas and dust around a nascent star. That’s interesting in itself, but even more remarkable, the water is being blasted apart by the young star’s laser-like jets. Spitzer’s spectrometer was used to get a better look at these jets and analyze the jet’s molecules. To the astronomers’ surprise, Spitzer picked up the signature of rapidly spinning fragments of water molecules, called hydroxyl, or OH. “This is a truly unique observation that will provide important information about the chemistry occurring in planet-forming regions, and may give us insights into the chemical reactions that made water and even life possible in our own solar system,” said Achim Tappe, of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass.

A young star forms out of a thick, rotating cloud of gas and dust. Like the two ends of a spinning top, powerful jets of gas emerge from the top and bottom of the dusty cloud. As the cloud shrinks more and more under its own gravity, its star eventually ignites and the remaining dust and gas flatten into a pancake-like disk, from which planets will later form. By the time the star ignites and stops accumulating material from its cloud, the jets will have died out.

Tappe and his colleagues used Spitzer’s infrared eyes to cut through the dust surrounding the star, called HH 211-mm, to analyze the jets. The astronomers were surprised to see water molecules in the data. But the results showed the hydroxyl molecules have absorbed so much energy (through a process called excitation) that they are rotating around with energies equivalent to 28,000 Kelvin (27,700 degrees Celsius). This far exceeds normal expectations for gas streaming out of a stellar jet. Water, which is abbreviated H2O, is made up of two hydrogen atoms and one oxygen; hydroxyl, or OH, contains one oxygen and one hydrogen atom.

The results reveal that the jet is ramming its head into a wall of material, vaporizing ice right off the dust grains it normally coats. The jet is hitting the material so fast and hard that a shock wave is also being produced.

“The shock from colliding atoms and molecules generates ultraviolet radiation, which will break up water molecules, leaving extremely hot hydroxyl molecules,” said Tappe.

Tappe said this same process of ice being vaporized off dust occurs in our own solar system, when the sun vaporizes ice in approaching comets. In addition, the water that now coats our world is thought to have come from icy comets that vaporized as they rained down on a young Earth. This discovery provides a better understanding of how water — an essential ingredient for life as we know it — is processed in emerging solar systems.

Source: JPL

Posted on by Nancy Atkinson

Spitzer Takes Family Portrait of Stars Amid Another “Celestal Geode”

Generations of stars amid a gas cavity. Credit: NASA/JPL-Caltech/Harvard-Smithsonian CfA

[/caption]

A new image from NASA’s Spitzer Space Telescope reveals generations of stars amid a cavity carved from a colorful cosmic cloud. The striking infrared picture shows a region, called W5, which is similar to N44F, or the “Celestial Geode” that was discussed in a Universe Today article last week. The gas cavity, which looks similar to a geode-like cavity found in some rocks, is carved by the stellar wind and intense ultraviolet radiation from hot stars. W5 is studded with stars of various ages, and provides new evidence that massive stars – through their brute winds and radiation – can trigger the birth of new stars.

The image was unveiled today at the Griffith Observatory in Los Angeles as part of Spitzer’s five-year anniversary celebration. Spitzer launched on August 25, 2003, from Cape Canaveral Air Force Station, Fla. A high-resolution version of the image is available here. It shows a family history full of life and death. But are the deaths of some stars responsible for the birth of new stars?

“Triggered star formation continues to be very hard to prove,” said Xavier Koenig of the Harvard Smithsonian Center for Astrophysics in Cambridge, Mass. “But our preliminary analysis shows that the phenomenon can explain the multiple generations of stars seen in the W5 region.”

The most massive stars in the universe form out of thick clouds of gas and dust. The stars are so massive, ranging from 15 to about 60 times the mass of the Sun, that some of their material slides off in the form of winds. The scorching-hot stars also blaze with intense radiation. Over time, both the wind and radiation blast away surrounding cloud material, carving out expanding cavities.

Astronomers have long suspected that the carving of these cavities causes gas to compress into successive generations of new stars. As the cavities grow, it is believed that more and more stars arise along the cavities’ expanding rims. The result is a radial “family tree” of stars, with the oldest in the middle of the cavity and younger and younger stars farther out.

The astronomer who last week explained the N44F image, Dr. You-Hua Chu from the University of Illinois, said along the walls of the cavity there are dust pillars sticking out and young stars are being formed at the tips of these pillars. Similar features are seen in the new Spitzer image of W5, where younger stars (seen as pink or white in the image) are embedded in the elephant-trunk-like pillars as well, and also beyond the cavity rim. The most massive stars (seen as blue dots) are at the center of two hollow cavities.

With Spitzer’s infrared vision, Koenig and his colleagues peered through the dusty regions of W5 to get a better look at the stars’ various stages of evolution and test the triggered star formation theory. The results from their studies show that stars within the W5 cavities are older than stars at the rims, and even older than stars farther out past the rim. This ladder-like separation of ages provides some of the best evidence yet that massive stars do, in fact, give rise to younger generations.

“Our first look at this region suggests we are looking at one or two generations of stars that were triggered by the massive stars,” said co-author Lori Allen of the Harvard-Smithsonian Center for Astrophysics. “We plan to follow up with even more detailed measurements of the stars’ ages to see if there is a distinct time gap between the stars just inside and outside the rim.”

Another version of the image, taken with Spitzer's Infrared Array Camera.
Another version of the image, taken with Spitzer's Infrared Array Camera.

Millions of years from now, the massive stars in W5 will die in tremendous explosions. When they do, they will destroy some of the young nearby stars – the same stars they might have triggered into being.

W5 spans an area of sky equivalent to four full moons and is about 6,500 light-years away in the constellation Cassiopeia. The Spitzer picture was taken over a period of 24 hours. The color red shows heated dust that pervades the region’s cavities. Green highlights the dense clouds, and white knotty areas are where the youngest of stars are forming. The blue dots are older stars in the region, as well as other stars in the background and foreground.

A paper on the findings will appear in the December 1, 2008, issue of the Astrophysical Journal.

Source: Harvard Smithsonian Center for Astrophysics

Posted on by Nancy Atkinson

No Life Possible at Edges of the Pinwheel Galaxy

The bright red spots at the edge of the Pinwheel Galaxy means bad news for life. Image credit: NASA/JPL-Caltech/STScI

[/caption]
Another beautiful image from the Spitzer Space Telescope; in this case, it’s Messier 101, more commonly known as the Pinwheel Galaxy. But the pretty red highlights at the edges of the galaxy are bad news for anyone looking for evidence of life. “If you were going look for life in Messier 101, you would not want to look at its edges,” said Karl Gordon of the Space Telescope Science Institute. “The organics can’t survive in these regions, most likely because of high amounts of harsh radiation.” The red color highlights a zone where organic molecules called polycyclic aromatic hydrocarbons (PAHs), which are present throughout most of the galaxy, suddenly disappear.

PAHs are dusty, carbon-containing molecules found in star nurseries. They’re also found on Earth in barbeque pits, exhaust pipes and anywhere combustion reactions take place. Scientists believe this space dust has the potential to be converted into the stuff of life.

The Pinwheel galaxy is located about 27 million light-years away in the constellation Ursa Major. It has one of the highest known gradients of metals (elements heavier than helium) of all nearby galaxies in our universe. In other words, its concentrations of metals are highest at its center, and decline rapidly with distance from the center. This is because stars, which produce metals, are squeezed more tightly into the galaxy’s central quarters.

Gordon’s team also wanted to learn more about the gradient of the PAHs. Using Spitzer’s Infrared Array Camera and the Infrared Spectograph to carefully analyze the spectra of the PAHs, astronomers can more precisely identify the PAH features, and even deduce information about their chemistry and temperature. The astronomers found that, like the metals, the polycyclic aromatic hydrocarbons decrease in concentration toward the outer portion of the galaxy. But, unlike the metals, these organic molecules quickly drop off and are no longer detected at the very outer rim.

“There’s a threshold at the rim of this galaxy, where the organic material is getting destroyed,” said Gordon.

The findings also provide a better understanding of the conditions under which the very first stars and galaxies arose. In the early universe, there were not a lot of metals or PAHs around. The outskirt of the Pinwheel galaxy therefore serves as a close-up example of what the environment might look like in a distant galaxy.

In this image, infrared light with a wavelength of 3.6 microns is colored blue; 8-micron light is green; and 24-micron light is red. All three of Spitzer instruments were used in the study: the infrared array camera, the multiband imaging photometer and the infrared spectrograph.

Original News Source: JPL