Hubble Finds that "Blue Blobs" in Space Are Orphaned Clusters of Stars

Credit: NASA, ESA, and D. de Mello (Catholic University of America/GSFC)

Finding blue blobs in space sounds like an encounter with an alien out of a science fiction movie. But the Hubble Space Telescope's powerful vision has resolved strange objects nicknamed "blobs" and found them to be brilliant blue clusters of stars born in the swirls and eddies of a galactic smashup 200 million years ago.

The findings are being reported by Duilia de Mello of the Catholic University of America, Washington, D.C. and NASA's Goddard Space Flight Center, Greenbelt, Md. and her colleagues at the 211th meeting of the American Astronomical Society in Austin, Texas.

Such "blue blobs"-weighing tens of thousands of solar masses-have never been seen in detail before in such sparse locations, say researchers. They are more massive than most open clusters found inside galaxies but a fraction of the mass of globular star clusters that orbit a galaxy.

Because the orphan stars don't belong to any particular galaxy, the heavier elements produced in their fusion furnaces may easily be expelled back into intergalactic space. This may offer clues as to how the early universe was "polluted" with heavier elements early in its history, say researchers.

The mystery is that the "blue blobs" are found along a wispy bridge of gas strung among three colliding galaxies, M81, M82, and NGC 3077, residing approximately 12 million light-years from Earth. This is not the place astronomers expect to find star clusters: in the "abyssal plain" of intergalactic space. "We could not believe it, the stars were in the middle of nowhere," says de Mello.

The "blue blobs" are clumped together in a structure called Arp's Loop, along the tenuous gas bridge. The gas filaments were considered too thin to accumulate enough material to actually build these many stars, says de Mello. But Hubble reveals the "blue blobs" contain the equivalent of five Orion Nebulae.

After finding that these "blobs" were resolved into stars, the team used the Hubble image to measure an age for the clusters of less than 200 million years with many stars as young and even younger than 10 million years. Not coincidentally, 200 million years is the estimated age of the galactic collision that created the tidal gas streamers, pulled between the galaxies like taffy.

De Mello and her team propose that the star clusters in this diffuse structure might have formed from gas collisions and subsequent turbulence, which enhanced locally the density of the gas streams. Galaxy collisions were much more frequent in the early universe, so "blue blobs" should have been common. After the stars burned out or exploded, the heavier elements forged in their nuclear furnaces would have been ejected to enrich intergalactic space.

Radio observations with the Very Large Array of radio telescopes in Socorro, New Mexico, gave a detailed map of the intergalactic bridge that revealed knots of denser gas. Studies with the 3.5-meter WIYN telescope on Kitt Peak in Arizona mapped the optical light glow of hydrogen along the bridge. Observations with NASA's Galaxy Evolution Explorer (GALEX) ultraviolet space telescope revealed an ultraviolet glow at the knots, and that earned them the nickname "blue blobs." But GALEX did not have the resolution to see individual stars or clusters. Only Hubble's Advanced Camera for Surveys at last revealed the point sources of the ultraviolet radiation.

New Risk to Earth Found in Supernova Explosions

Eta Carinae is drawing closer to its ultimate explosive demise. When Eta Carinae explodes, it will be a spectacular fireworks display seen from Earth, perhaps rivaling the moon in brilliance. Its fate has been foreshadowed by the recent discovery of SN2006gy, a supernova in a nearby galaxy that was the brightest stellar explosion ever seen. This composite image shows optical light (blue) and X-ray light (orange and yellow).

Credit: NASA/CXC/GSFC/STScI

An explosive star within our galaxy is showing signs of an impending eruption, at least in a cosmic time frame, and has for quite some time. From 1838 to 1858, the star called Eta Carinae brightened to rival the light of Sirius, the brightest star in the sky, and then faded to a dim star. Since 1940 it has been brightening again, and scientists think Eta Carinae will detonate in 10,000 to 20,000 years.

Fortunately, Eta Carinae is far away, at least 7,500 light-years from Earth. If it explodes, most of its energy will be scattered or absorbed in the vast emptiness of space. It also happens to be tilted about 45 degrees from the line of sight to Earth, so any type of gamma-ray burst, a high-energy outburst expected with this star's eventual eruption, would miss the Earth. Cosmic rays would be diffused by magnetic fields, and most of the damaging light would not affect life on Earth.

In general, threats to life on Earth from supernovae are extremely small, for all except the nearest explosions — those 30 light-years away or closer.

But what if a supernova were 100 times brighter than usual? Would there be any risk to life on Earth then?

Astronomers found such a record-breaking supernova last year, SN 2006gy.

Brightest ever

SN 2006gy was the brightest supernova ever recorded until an even brighter one was discovered in November.

Astronomers now know the progenitor of SN 2006gy was remarkably similar to Eta Carinae. They warn a superluminous supernova might explode right in our own galaxy.

Brian Thomas at Washburn University has been studying the effects of astronomical explosions at the Goddard Space Flight Center. He decided to investigate what would happen to Earth's protective ozone layer if Eta Carinae explodes with the brilliance of SN 2006gy.

It turns out that even though SN 2006gy was one of the brightest supernovae ever recorded, it did not generate a large amount of X-rays. Thomas and his team found most of the light, including damaging X-rays and cosmic rays, would scatter into space before ever reaching Earth.

So would there be any damage to Earth from such a spectacular event? Though Thomas found X-rays and cosmic rays would cause little damage, he also looked at optical light, particularly short-wavelength blue light (400 nanometers), where the spectrum of SN 2006gy peaked. No one had ever considered the effects of this light before, either from supernovae or any other type of event.

"The visible light could be significant," Thomas says, "But this depends a little bit on your definition of significant."

Brighter than Venus

If Eta Carina were to explode like SN 2006gy, it would quickly become the brightest object in the sky other than the sun and the moon.

For those living where Eta Carina is always above the horizon (Antarctica, New Zealand and extreme southern regions of Australia and South America) the light would vastly outshine Venus, visible even during the day. The radiation would illuminate the evening sky with a bluish glow nearly strong enough to read by, and the effect would likely last for months — perhaps six or more.

The cumulative effects of long-duration exposure to blue-enhanced light would begin to interfere with life on Earth.

Those who study chronobiology, or the effects of biological timing, have found that low levels of blue light can strongly affect the endocrine systems of mammals by causing physiological and alerting responses. Blue-enhanced light is associated with reduced levels of melatonin production and affects circadian rhythms. For these reasons, it is sometimes prescribed to counteract seasonal affective disorder (SAD) or winter depression.

"This is not going to be an 'everything dies immediately' kind of event," Thomas said. "But with the risk factors associated with higher levels of this kind of light it's certainly something that could be important in the longer run."

New threshold

In a paper about to be published in the journal Astrobiology, Thomas explains that even short exposures to blue light can increase insomnia, reduce resistance to infection and is being studied as a possible risk of cancer.

Yet, in the case of Eta Carinae, the effect of these optical photons would be minimal. The scattering of photons by dust and gas is greatest at blue wavelengths (thus giving Earth its blue sky) and the sheer distance of Eta Carinae diminishes the optical intensity by about 20 percent.

But while damage from optical light is not a factor for Eta Carinae, the effects of this light should be considered to any risk assessment of supernovae. Based on his results, Thomas now estimates the biological threshold for supernovae to be about 100 light-years away. At that distance, life on Earth can expect some sort of supernova radiation about once every 20 million years.

By Laura Kinoshita
Special to LiveScience
http://www.space.com

White dwarf pulses like a pulsar

Provided by NASA's Goddard Space Flight Center

New observations from Suzaku, a joint Japanese Aerospace Exploration Agency (JAXA) and NASA X-ray observatory, have challenged scientists' conventional understanding of white dwarfs. Observers had believed white dwarfs were inert stellar corpses that slowly cool and fade away, but the new data tell a completely different story.

At least one white dwarf, known as AE Aquarii, emits pulses of high-energy (hard) X-rays as it whirls around on its axis. "We're seeing behavior like the pulsar in the Crab Nebula, but we're seeing it in a white dwarf," says Koji Mukai of NASA Goddard Space Flight Center in Greenbelt, Maryland. The Crab Nebula is the shattered remnant of a massive star that ended its life in a supernova explosion. "This is the first time such pulsar-like behavior has ever been observed in a white dwarf."

White dwarfs and pulsars represent distinct classes of compact objects that are born in the wake of stellar death. A white dwarf forms when a star similar in mass to the Sun runs out of nuclear fuel. As the outer layers puff off into space, the core gravitationally contracts into a sphere about the size of Earth, but with roughly the mass of the Sun. The white dwarf starts off scorching hot from the star's residual heat. But with nothing to sustain nuclear reactions, it slowly cools over billions of years, eventually fading to near invisibility as a black dwarf.

A pulsar is a type of neutron star, a collapsed core of an extremely massive star that exploded in a supernova. Whereas white dwarfs have incredibly high densities by earthly standards, neutron stars are even denser, cramming roughly 1.3 solar masses into a city-sized sphere. Pulsars give off radio and X-ray pulsations in lighthouse-like beams.
An artist depicts the Suzaku X-ray observatory in Earth's orbit. JAXA [View Larger Image]
The discovery team, led by Yukikatsu Terada of the Institute of Physical and Chemical Research (RIKEN) in Wako, Japan, was not expecting to find a white dwarf mimicking a pulsar. Instead, the astronomers were hoping to find out if white dwarfs could accelerate charged subatomic particles to near-light speed, meaning they could be responsible for many of the cosmic rays that zip through our galaxy and occasionally strike Earth.

Some white dwarfs, including AE Aquarii, spin very rapidly and have magnetic fields millions of times stronger than Earth's. These characteristics give them the energy to generate cosmic rays.

To find out if this is happening, Terada and his colleagues targeted AE Aquarii with Suzaku in October 2005 and October 2006. The white dwarf resides in a binary system with a normal companion star. Gas from the star spirals toward the white dwarf and heats up, giving off a glow of low-energy (soft) X-rays. But Suzaku also detected sharp pulses of hard X-rays. After analyzing the data, the team realized that the hard X-ray pulses match the white dwarf's spin period of once every 33 seconds.

The hard X-ray pulsations are very similar to those of the pulsar in the center of the Crab Nebula. In both objects, the pulses appear to be radiated like a lighthouse beam, and a rotating magnetic field is thought to be controlling the beam. Astronomers think that the extremely powerful magnetic fields are trapping charged particles and then flinging them outward at near-light speed. When the particles interact with the magnetic field, they radiate X-rays.

"AE Aquarii seems to be a white dwarf equivalent of a pulsar," says Terada. "Since pulsars are known to be sources of cosmic rays, this means that white dwarfs should be quiet but numerous particle accelerators, contributing many of the low-energy cosmic rays in our galaxy."

Launched in 2005, Suzaku is the fifth in a series of Japanese satellites devoted to studying celestial X-ray sources. Managed by JAXA, this mission is a collaborative effort between Japanese universities and institutions and Goddard.

www.astronony.com

Old Comets for a New Year

Giampaolo Salvato photographed Comet Tuttle on Dec. 30, 2007 as it appeared near the spiral galaxy M33. The image was taken from northern Italy with a backyard telescope and a digital camera.

Credit: Giampaolo Salvato (astrosurf.com/eyesinthesky)

As we kick off the year 2008, Comet Tuttle is putting on a nice show for backyard skywatchers. It had not been seen since 1994, but you'll have an excellent opportunity to pick it up with binoculars or small telescopes during the next two weeks.

Tuttle can even be glimpsed by sharp-eyed observers under pristine skies without any optical aids, for it is one of the brightest of the short-period comets, those that orbit the sun often enough to be seen again and again from Earth and identified as such.

And speaking of short-period comets, Comet Holmes continues to delight observers more than two months after its stupendous explosion to naked-eye visibility.

Discovery

As we all know, Halley's was the first comet-to be recognized as periodic, but it had been seen on many previous returns before Edmund Halley announced that fact in the year 1705. Similarly, although Encke's comet was discovered in 1786, it was observed on three more returns before Johann Franz Encke determined that it had an orbital period of 3.3-years.

The object that we today call Comet Tuttle had a similar history.

On Jan. 9, 1790, the renowned Parisian comet hunter Pierre Méchain discovered a fairly bright telescopic comet in the western evening sky. His friend and rival Charles Messier described it on the following night as resembling an unresolved star cluster or nebula without a nucleus. It was followed for just over three weeks; just not enough time for a sufficient number of observations to determine an accurate orbit.

Astronomers assumed that the object was traveling in a parabolic orbit and would never be seen again, and entered the literature simply as "Comet 1790 II." It wasn't to be seen again for nearly 70-years.

Tuttle's turn

Horace P. Tuttle, an assistant at Harvard College Observatory, discovered three comets by telescope during the year 1858. Tuttle found the first of them on Jan. 4 in the constellation Andromeda. Still approaching the perihelion point of its orbit (its least distance from the sun), the comet was favorably placed relative to the Earth, and this made possible a long series of positional measurements.

Comet Tuttle was brightest during February at about magnitude 7, meaning it was just below the threshold of naked eye visibility, though a relatively easy object to see with binoculars or a small telescope.

Tuttle himself was among the first to suggest that his object was identical with Comet 1790 II. A 13.7-year period was proposed by several astronomers, and it soon became clear that Comet Tuttle of 1858 had been missed at four intervening apparitions. At three of those returns (1803, 1817, and 1844) it was too close to the sun in the sky to be seen, while conversely, in 1830 it should have been an easy object in the morning sky but was somehow missed.

Comet Tuttle became the eighth comet to be recognized as a periodic object hence it is now designated as 8P/Tuttle.

The perihelion distance of 8P/Tuttle places it just outside of the Earth's orbit at 95.5 million miles (153.6 million kilometers). Also, around Dec. 22 of each year the Earth passes through the dusty trail left behind by the comet from its previous visits. This encounter gives rise to an annual display of meteors known as the Ursids, which appear to diverge from near the bright star Kochab in the bowl of the Little Dipper.

Because 8P/Tuttle was observed at each return following its 1858 rediscovery except in 1953, this time around will go down in the record books as its 12th observed apparition. And as it turns out, this apparition will be among its very best.

Where and when to look

Comet Tuttle

On New Year's Day, 8P/Tuttle passed closest to Earth; a distance of 23.5 million miles (37.8 million kilometers). Although it is now slowly moving away from the Earth, it will continue to slowly approach the sun, passing closest to it on Jan. 27. Comets are most visible when they near the sun, which lights up material that boils off the comet.

So, during these next two weeks, the comet will hold nearly steady in brightness at around magnitude 6. For those blessed with clear, dark skies far from significant light pollution, the comet might be even glimpsed with the unaided eye. But good binoculars or a small telescope will easily bring 8P/Tuttle into view if you know where to train them; it should appear as a small fuzzy star possibly sporting a faint, narrow tail.

The comet will be situated against the rather dim stars that compose the so-called "watery region" of the sky, passing through eastern Pisces (the fishes) into Cetus (the whale) during the night of Jan. 6-7. On that night, it will lie not far to the west from one of the brightest stars in Pisces: fourth magnitude, Al Rischa, located at the point where the two fish are tied. In fact, the name comes from the Arabic word for "cord."

For the next couple of weeks both Pisces and Cetus can be conveniently found well up in the southern sky between 6 to 8 p.m. local standard time.

Comet 8P/Tuttle will appear to skid south in its orbit against the background stars of these two constellations. After moving through Cetus, 8P/Tuttle will pass into the dim, shapeless constellation of Fornax (the furnace) on Jan. 16. It will continue to plunge south thereafter, gradually becoming unfavorably placed for viewers in the Northern Hemisphere, although those living south of the equator will be able to follow the now fading comet right on into February.

A reminder about Comet Holmes!

Comet Holmes

While the spotlight is now on Comet Tuttle, we should not forget about our old friend, Comet Holmes which continues to be dimly visible to the unaided eye as a diffuse, circular cloud, roughly twice the apparent diameter of the moon against the stars of the constellation Perseus.

This comet was no brighter than magnitude 17 in mid-October — that's about 25,000 times fainter than the faintest star that can normally be seen without any optical aid. But late on Oct. 23, the comet's brightness suddenly rocketed all the way up to magnitude 2.5, brightening nearly one million times in less than 24 hours!

In attempting to explain why Comet Holmes exploded, comet expert, John Bortle suggested that this comet's nucleus consists of low-density material that, over time developed into a large region with a very tenuous structure, like a honeycomb. At some point, the highly fragile bonds connecting the honeycomb of material reached a failing point and a sudden crushing collapse occurred, expelling a gigantic volume of dust into space, making this dim comet suddenly appear impressively bright.

Back in 1892, Comet Holmes suffered two major outbursts separated by about 75 days. This leads to the question as to whether this comet will undergo a similar "cosmic aftershock" in the wake of its recent late October explosion.

Bortle thinks it's a possibility, based on the theory that there may be a large amount of residual instability which might lead to a second major collapse of material on the comet nucleus. If what happens now parallels what happened in 1892, another possible explosive outburst may be imminent, so it might be wise to keep a close watch on Comet Holmes in the coming days ahead.

By Joe Rao
SPACE.com Skywatching Columnist

Hot Cyclones Churn at Both Ends of Saturn

This image shows newly discovered "hot spot" on Saturn's north pole and the mysterious hexagon that encircles the pole. The "hot spot" appears to be related to Saturn's dynamic weather systems, rather than to seasonal changes in the amount of sunlight at the pole. Credit:NASA/JPL/GSFC/Oxford University

Despite more than a decade of winter darkness, Saturn's north pole is home to an unexpected hot spot remarkably similar to one at the planet's sunny south pole. The source of its heat is a mystery. Now, the first detailed views of the gas giant's high latitudes from the Cassini spacecraft reveal a matched set of hot cyclonic vortices, one at each pole.

While scientists already knew about the hot spot at Saturn's south pole from previous observations by the W. M. Keck Observatory in Hawaii, the north pole vortex was a surprise. The researchers report their findings in the Jan. 4 issue of Science.

"We had speculated that the south pole hot spot was connected to the southern, sunlit conditions," said Glenn Orton, a senior research scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif., and co-investigator on Cassini's composite infrared spectrometer. "Since the north pole has been deprived of sunlight since the arrival of winter in 1995, we didn't expect to find a similar feature there."

The infrared data show that the shadowed north pole vortex shares much the same structure and temperature as the one at the sunny south pole. The cores of both show a depletion of phospine gas, an imbalance probably caused by air moving downward into the lowest part of Saturn's atmosphere, the troposphere. Both polar vortices appear to be long-lasting and intrinsic parts of Saturn and are not related to the amount of sunlight received by one pole or the other.

"The hot spots are the result of air moving polewards, being compressed and heated up as it descends over the poles into the depths of Saturn," said Leigh Fletcher, a planetary scientist from the University of Oxford, England, and the lead author of the Science paper. "The driving forces behind the motion, and indeed the global motion of Saturn's atmosphere, still need to be understood."

Though similar, the two polar regions differ in one striking way. At the north pole, the newly discovered vortex is framed by the distinctive, long-lived and still unexplained polar hexagon. This mysterious feature encompassing the entire north pole was first spotted in the 1980s by NASA's Voyager 1 and 2 spacecraft. Cassini's infrared cameras also detected the hexagon in deep atmospheric clouds early in 2007.

In their paper, Fletcher and his colleagues report that the bright, warm hexagon is much higher than previous studies had shown. "It extends right to the top of the troposphere," says Fletcher. "It is associated with downward motion in the troposphere, though the cause of the hexagonal structure requires further study."

Winter lasts about 15 years on Saturn. Researchers anticipate that when the seasons change in the coming years and Saturn's north pole is once again in sunlight, they will be able to see a swirling vortex with high eye walls and dark central clouds like the one now visible at the south pole. "But Saturn may surprise us again," says Fletcher.

"The fact that Neptune shows a similar south polar hot spot whets our appetite for the strange dynamics of the poles of the other gas giants," Fletcher says.

More information about Jupiter's poles will come from NASA's Juno mission, currently scheduled for launch in 2011 and arrival in 2016.

Running Rings Around the Galaxy

An artist concept showing the newly discovered streams of stars around our Milky Way galaxy.
NASA/JPL-Caltech/R. Hurt (SSC)

An astronomer at the Spitzer Science Center has discovered three giant stellar streams arcing high over the Milky Way. Remnants of cannibalized galaxies and star clusters, the streams are between 13,000 and 130,000 light-years distant from Earth and extend over much of the northern sky. The new results are being presented by Carl Grillmair at this week's meeting of the American Astronomical Society in Honolulu, Hawaii.

Two of the newly discovered streams are almost certainly the remains of ancient star clusters. Known to astronomers as globular clusters, these giant stellar cities contain between tens of thousands and millions of stars. Though only about 150 globular clusters orbit the Milky Way today, they may once have numbered in the thousands.

Over billions of years, the relentless gravitational stresses inflicted on them by our galaxy have slowly torn them apart, leaving behind long, thin streams of stars. Once crowded so closely together that they could sometimes actually collide, these stars are now separated by many light-years, trailing one another at half a million miles an hour through the dark and lonely reaches of the galactic halo.

Grillmair, an associate research scientist at Caltech's Spitzer Science Center, found the streams by analyzing data from the Sloan Digital Sky Survey. Conducted over several years at the Apache Point Observatory in New Mexico, this survey has yielded measurements for some 70 million stars spread over one quarter of the whole sky.

By comparing the colors and brightnesses of the stars to those in surviving globular clusters, Grillmair was able to isolate stars into groups of similar age and distance. As he examined how these groups are distributed across the sky, the giant stellar streams quickly became apparent.

The third stream discovered by Grillmair is spread over a much larger region of the sky, and is most likely the scattered remains of a dwarf galaxy. Such dwarf galaxies may contain up to 100 million stars, along with sometimes substantial amounts of mysterious "dark matter." While the Milky Way galaxy currently hosts a family of 20 or so known dwarf galaxies, scientists who study the growth of galaxies in the early universe have long been puzzled as to why we don't see hundreds of them.

The new dwarf galaxy stream is particularly interesting in that Grillmair may also have found the feebly struggling remains of the original galaxy.

The stripping and cannibalization of dwarf galaxies and star clusters can be quite episodic, resulting in streams with strong concentrations of stars separated by often substantial gaps, much like the typical distribution of cars on a highway. However, one of the stellar concentrations is many times stronger than the others, and Grillmair believes this may be the remnant of the galaxy that gave rise to the stream. "We'll need to bring out the big telescopes to examine these stars in detail and find out whether they're still gravitationally bound to one another," he says.

The new streams are among the largest features in the sky. The streams extend to the limits of the Sloan survey area, and Grillmair considers it quite likely that they wrap completely around the galaxy.

Grillmair is now planning follow-up observations of stars in these streams. While this discovery strengthens the notion that there may be thousands of such streams and that the outer reaches of our galaxy look more like a "ball of yarn," the real payoff may be in using these streams as very sensitive probes of galactic gravity.

By measuring the velocities of stars in the streams, astronomers can both map their orbits and determine how matter is distributed in our galaxy. "It's a bit like looking at aerial TV coverage of kayakers on a river," says Grillmair. "The location of the river immediately tells you where the bottom of the valley and the major rock outcroppings are, and the speed of the kayakers gives you some idea of how high and how steep the surrounding mountains must be."

The new discoveries bring to nine the number of known stellar streams around the galaxy. These streams are helping astronomers study our galaxy's underlying structure more accurately than ever before.

Overall, the streams appear to be consistent with a picture in which our galaxy is dominated by huge amounts of smoothly distributed dark matter. On the other hand, Grillmair and others have already found intriguing departures that may be showing up cracks in this model.

"This is a very exciting time for galactic archeology, and finding more of these ancient streams will really help us to piece together the structure of our galaxy and how it evolved over time."

Taken from a Caltech press release
May 30, 2007

Young Planet Orbits Sun-Like Star

This computer graphic shows the newly discovered young,
massive planet around the its host star TW Hydrae.
The planet orbits its active host star inside the inner hole of a dusty circumstellar disk.
Credit Johny Setiawan/MPIA

Astronomers say they have discovered the youngest planet to date circling a sun-like star, a find that will be a boon to the field of planet-formation theory.

The extrasolar planet is an estimated 8 million to 10 million years old, a mere toddler compared to Earth, which is 4.5 billion years old. Until now, the researchers say, no planet younger than 100 million years old has been detected circling a sun-like star.

"It means we're opening up a new field of trying to find planets around very young stars," said Alan Boss, a planet-formation theorist at the Carnegie Institution of Washington. "So it's the very first example, and we hope there will be a lot more." Boss was not involved in the discovery.

The newly found world is so infantile that it resides in the star's "protoplanetary disk," a ring of gas and dust circling the star. It has been catalogued as TW Hya b.

"This demonstrates that planets can form within 10 million years, before the disk has been dissipated by stellar winds and radiation," the researchers write in the Jan. 3 issue of the journal Nature.

Weighing in at nearly 10 Jupiter masses, the planet circles at a distance of .04 Astronomical Units (AU) from its host star, TW Hydrae, in the constellation Hydra. One AU is the average distance between the Earth and sun.

The gassy "hot Jupiter" takes 3.56 days to orbit its star. The host star is located 180 light-years away from Earth.

Planets are thought to form within disks of dust and gas around newly born stars. Catching a planet in its childhood can give astronomers lots of information about how planets materialize.

"The discovery shows that what we always call as 'protoplanetary' disks are indeed protoplanetary; they form planets," study researcher Johny Setiawan of the Max-Planck Institute for Astronomy in Germany told SPACE.com. "There are many 'protoplanetary' disks detected around young stars, but no planets so far have been detected within such young systems."

Around some young star systems, however, astronomers have found signs of planets by noting clear lanes of dust within the disks. In these cases, it's presumed that young planets are forming and have scooped up the dust, but the planets themselves have not been detected.

Setiawan and colleagues discovered their new world by measuring a wobble in the host star due to the gravitational tug from the orbiting planet. This so-called radial-velocity method is great at detecting extrasolar planets, but it also can produce false positives — suggesting a planet is there when in fact the data owe to some other object or phenomenon.

That's particularly true in young star systems. For one, nascent stars are incredibly active and their changing outer atmospheres can at the very least make for background noise. In addition, if the star rotates about its axis, that can be problematic.

"There are lots of other things going on in these young stars that could give you a false positive, where you think you're seeing a planet but you're actually seeing some other stellar activity," Boss said in a telephone interview.

Boss thinks the discoverers ruled out these non-planet signals. "They've done a good job of trying to address those worries," he said.

By Jeanna Bryner
Staff Writer
www.space.com

Asteroid may hit Mars Next Month

Will asteroid 2007 WD₅ crash into Mars January 30? Odds it'll happen are now 1 in 75.
Astronomy: Roen Kelly

A space rock dubbed 2007 WD₅ is taking aim on the Red Planet.

Francis Reddy

A small asteroid discovered November 20 may strike Mars next month.

Astronomers with NASA's Near Earth Object (NEO) Program at the Jet Propulsion Laboratory in Pasadena, California, calculate the odds of a January 30 collision at 1 in 75. While this is remote, it's less so than last week's estimated 1-in-350 chance.

NEO astronomer Steve Chesley, who's used to dealing with million-to-one odds, calls the event "extremely unusual," and, in something of a twist, NEO astronomers are rooting for an impact.

An armada of spacecraft orbiting the Red Planet — the European Space Agency's Mars Express and NASA's Mars Reconnaissance Orbiter and Mars Odyssey — would have ringside seats to view the strike and its after-effects. Even Earth-based telescopes could potentially observe the impact because Mars is near opposition and, therefore, unusually close.

Astronomers say asteroid 2007 WD5 is about 160 feet (50 meters) across. If it struck Mars, the energy would be similar to the 1908 Tunguska blast in Siberia, where a stony asteroid exploded above the taiga. The blast felled and scarred trees over 810 square miles (2,100 square km).

One difference: Tunguska was an air burst and left no crater, whereas 2007 WD5 likely would reach Mars' surface intact.

www.astronomy.com

Tyrrhenian Sea and Solstice Sky

Credit & Copyright: Danilo Pivato

Today the Solstice occurs at 0608 Universal Time, the Sun reaching its southernmost declination in planet Earth's sky. Of course, the December Solstice marks the beginning of winter in the northern hemisphere and summer in the south.

When viewed from northern latitudes, the Sun will make its lowest arc through the sky along the southern horizon.

So in the north, the Solstice day has the shortest length of time between sunrise and sunset and fewest hours of daylight.

This striking composite image follows the Sun's path through the December Solstice day of 2005 in a beautiful blue sky, looking down the Tyrrhenian Sea coast from Santa Severa toward Fiumicino, Italy. The view covers about 115 degrees in 43 separate, well-planned exposures from sunrise to sunset.

Earth's Protective Magnetic Field

On August 11, 2000, the Extreme Ultraviolet (EUV) instrument aboard the IMAGE spacecraft captured this view of Earth's magnetosphere from above the north pole.

Credit: NASA / IMAGE Science Team

New research shows that Earth's magnetic field could help protect astronauts while working on the Moon.

It has been 35 years since humans last walked on the Moon, but there has been much recent discussion about returning, either for exploration or to stage a mission to Mars. However, there are concerns about potential radiation danger for astronauts during long missions on the lunar surface.

A significant part of that danger results from solar storms, which can shoot particles from the Sun to Earth at nearly the speed of light and can heat oxygen in the Earth's ionosphere and send it in a hazardous stream toward the Moon.

Earth is largely protected by its magnetic field, or magnetosphere. Now, new University of Washington research shows that some parts of the Moon also are protected by the magnetosphere for 7 days during the 28-day orbit around Earth.

"We found that there were areas of the Moon that would be completely protected by the magnetosphere and other areas that are not protected at all," says Erika Harnett, a UW assistant research professor of Earth and space sciences.

Solar energetic particles, which are generated during solar storms, carry enough energy to disrupt communications on Earth or even kill satellites in Earth orbit. During those same storms, particles from Earth's ionosphere, primarily oxygen, also can become significantly energized. Though they are not as powerful as solar energetic particles, they still pose a significant threat to astronauts working on the moon, or even en route to Mars.

Using computers to model properties of the magnetosphere, Harnett found that while solar storms can increase the danger from ionosphere particles hitting the moon, they also trigger conditions in the magnetosphere that deflect many hazardous solar particles.

Particles with high enough energy can pass directly through a human without much damage, Harnett says, but particles packing slightly less oomph, though unfelt by a human, can lodge in a person. Typically it's not just one particle, but many, and the accompanying radiation can damage cells, she says.

In the longest missions of NASA's Apollo Program, astronauts spent just a few days on the Moon. The last mission, Apollo 17, was launched December 7, 1972, landed on the Moon on December 11 and arrived back on Earth on December 19.

"During Apollo, people were not on the Moon for very long so there wasn't the concern about the radiation hazard to humans as there is with longer missions," Harnett says.

Today there is much greater understanding of the danger posed by solar energetic particles, particularly because of the adverse effects they can have on satellite communications during periods of intense solar flare activity.

"The problem is that we can't predict when this activity is going to take place so we can't warn astronauts to take shelter, so they could be vulnerable when the Moon is outside the magnetosphere," Harnett says. "The particles travel near the speed of light, so when we see them generated on the Sun's surface they will arrive in a few minutes and there is little time to react."

The new research could help determine when it is safe for astronauts to work far from a lunar base, she says. But she adds that models used in the work suggest that energetic oxygen from Earth's ionosphere also poses a danger, even though it is less energetic than solar particles.

"It wouldn't kill someone instantly, but it definitely could increase the radiation exposure for an astronaut on the Moon," Harnett says.

However, she notes that the danger from energetic oxygen could be overstated because the models do not take into account the positive electrical charge on the daylight side of the Moon that likely would significantly slow the oxygen stream.

Provided by the University of Washington

Nebula NGC 2170

This enigmatic region in the constellation of Monoceros displays a wonderful mix of nebula types. The bluish areas are reflection nebulas, so-named because they reflect the light of nearby stars. The dust particle size in these areas preferentially reflects blue light, similar to cigarette and other kinds of smoke. The red areas are emission nebulas, and shine by a different mechanism. Ultraviolet light from nearby stars excites hydrogren and other gas atoms in the nebula, which then emit light of their own in specific colors. Finally, what looks a bit like black ink spilled across the image constitutes a dark nebula, and is only seen because of the light that it blocks. In other words, the dark nebula is seen in silhouette.

Cosmic Ornament of Gas and Dust

Image credit: NASA/JPL-Caltech /O.Krause/
(Stewart Observatoru)

Astronomers have at last found definitive evidence that the universe's first dust - the celestial stuff that seeded future generations of stars and planets - was forged in the explosions of massive stars.

The findings, made with NASA's Spitzer Space Telescope, are the most significant clue yet in the longstanding mystery of where the dust in our very young universe came from. Scientists had suspected that exploding stars, or supernovae, were the primary source, but nobody had been able to demonstrate that they can create copious amounts of dust - until now. Spitzer's sensitive infrared detectors have found 10,000 Earth masses worth of dust in the blown-out remains of the well-known supernova remnant Cassiopeia A.

"Now we can say unambiguously that dust - and lots of it - was formed in the ejecta of the Cassiopeia A explosion. This finding was possible because Cassiopeia A is in our own galaxy, where it is close enough to study in detail," said Jeonghee Rho of NASA's Spitzer Science Center at the California Institute of Technology in Pasadena. Rho is the lead author of a new report about the discovery appearing in the Jan. 20 issue of the Astrophysical Journal.

Space dust is everywhere in the cosmos, in our own neck of the universe and all the way back billions of light-years away in our infant universe. Developing stars need dust to cool down enough to collapse and ignite, while planets and living creatures consist of the powdery substance. In our nearby universe, dust is pumped out by dying stars like our sun. But back when the universe was young, sun-like stars hadn't been around long enough to die and leave dust.

That's where supernovae come in. These violent explosions occur when the most massive stars in the universe die. Because massive stars don't live very long, theorists reasoned that the very first exploding massive stars could be the suppliers of the unaccounted-for dust. These first stars, called Population III, are the only stars that formed without any dust.

Other objects in addition to supernovae might also contribute to the universe's first dust. Spitzer recently found evidence that highly energetic black holes, called quasars, could, together with supernovae, manufacture some dust in their winds (http://www.spitzer.caltech.edu/Media/releases/ssc2007-16/index.shtml) .

Rho and her colleagues analyzed the Cassopeia A supernova remnant, located about 11,000 light-years away. Though this remnant is not from the early universe, its proximity to us makes it easier to address the question of whether supernovae have the ability to synthesize significant amounts of dust. The astronomers analyzed the infrared light coming from Cassiopeia A using Spitzer's infrared spectrograph, which spreads light apart to reveal the signatures of different elements and molecules. "Because Spitzer is extremely sensitive to dust, we were able to make high-resolution maps of dust in the entire structure," said Rho.

The map reveals the quantity, location and composition of the supernova remnant's dust, which includes proto-silicates, silicon dioxide, iron oxide, pyroxene, carbon, aluminium oxide and other compounds. One of the first things the astronomers noticed was that the dust matches up perfectly with the gas, or ejecta, known to have been expelled in the explosion. This is the smoking gun indicating the dust was freshly made in the ejecta from the stellar blast. "Dust forms a few to several hundred days after these energetic explosions, when the temperature of gas in the ejecta cools down," said Takashi Kozasa, a co-author at the Hokkaido University in Japan.

The team was surprised to find freshly-made dust deeper inside the remnant as well. This cooler dust, mixed in with gas referred to as the unshocked ejecta, had never been seen before.

All the dust around the remnant, both warm and cold, adds up to about three percent of the mass of the sun, or 10,000 Earths. This is just enough to explain where a large fraction, but not all, of the universe's early dust came from. "Perhaps at least some of the unexplained portion is much colder dust, which could be observed with upcoming telescopes, such as Herschel," said Haley Gomez, a co-author at University of Wales, Cardiff. The Herschel Space Observatory, scheduled to launch in 2008, is a European Space Agency mission with significant NASA participation.

Rho also said that more studies of other supernovae from near to far are needed to put this issue to rest. She notes that the rate at which dust is destroyed - a factor in determining how much dust is needed to explain the dusty early universe - is still poorly understood.

The principal investigator of the research program, and a co-author of the paper, is Lawrence Rudnick of the University of Minnesota, Twin Cities. Other co-authors include W.T. Reach of the Spitzer Science Center; J. D. Smith of the Steward Observatory, Tucson, Ariz.; T. Delaney of the Massachusetts Institute of Technology, Cambridge; J.A. Ennis of the University of Minnesota; and A. Tappe of the Spitzer Science Center and the Harvard Smithsonian Center for Astrophysics, Cambridge, Mass.

Lifestyles of the Galaxies Next Door

Credit:NASA/JPL-Caltech/K. Gordon (Space Telescope Science Institute) and SINGS Team
High-Resolution (4200x3600) : JPEG (9.4 MB)

The "lifestyles" of 75 neighboring galaxies are illuminated in this poster from NASA's Spitzer Space Telescope. Scientists say this fresh perspective of our cosmic neighborhood provides valuable insights into growth process of galaxies at a glance.

Over the past four years, Spitzer snapped infrared portraits of some of our most fascinating galactic neighbors as part of the Spitzer Infrared Nearby Galaxy Survey (SINGS) Legacy project. By understanding the mechanisms that fuel and hinder star production in these nearby galaxies, SINGS astronomers hope to solve the mystery of where galaxies come from, and how they've developed throughout the universe's history.

"Once the SINGS observations were done, I began to wonder how to look at all of the galaxies and make sense of the big picture. The SINGS sample of 75 galaxies was just too many to display at once on a computer screen and still be able to appreciate the spatial details present in the images," said Dr. Karl Gordon, of the Space Science Telescope Institute, in Baltimore, Md., who is a member of the SINGS team.

Eventually, Gordon decided to create a poster with the 75 galaxies organized by shape -- using the classification system that astronomer Edwin Hubble created in 1925, soon after the physical nature of galaxies was discovered. The grouping system is called "Hubble's Tuning-Fork" because its overarching shape resembles a musical tuning-fork.

In this structure, elliptical galaxies sit on the left side of the poster, creating the tuning fork's handle. They are designated by the letter "E", and given a number from zero to seven. An "E0" galaxy looks round, while an E7 galaxy is very long and thin.

Spiral galaxies are located to the right side of the poster creating the fork's two prongs. The top prong is made up of regular spiral galaxies, and identified by the letter "S." Barred spiral galaxies make up the bottom prong, and are branded "SB." Meanwhile, letters -- "a", "b", and "c" -- indicate how tightly the spiral arms are wound. An "Sa" galaxy's arms are wound very tightly, while an "Sc" galaxy's spiral arms are very loosely wound.

"Irregular galaxies were not represented in Hubble's original diagram, so we organized them on the bottom-left side of the poster," says Gordon.

In this poster, blue colors reveal light from an older population of stars. Tints of green represent organic molecules called polycyclic aromatic hydrocarbons, while red lumps show clouds of warm dust and gas heated by radiation from newborn stars.

"One of the most striking things about putting these galaxies into the tuning-fork pattern is that you see right away, elliptical galaxies are bluer, which means that they are made up of primarily older stars. The spiral galaxies on the other hand have wisps of green and red, indicating the presence of warm dust and star formation," says Dr. Robert Kennicutt, of the Institute of Astronomy at the University of Cambridge, United Kingdom, and leader of the SINGS team.

According to Kennicutt, astronomers can infer that spiral galaxies on the right-hand side of the tuning fork are younger because most are rich in dust and actively forming stars. Stars form like raindrops in space, when dense cosmic clouds of dust and gas condense, and nuclear fusion is ignited.

He also notes that the elliptical galaxies on the left largely lack dust, indicating that they are not forming many new stars. The rich-blue color of elliptical galaxies also reveals the presence of a primarily older stellar population. In contrast to the spirals, the elliptical galaxies exhausted their gas and dust supplies billions of years ago.

"When I see this poster, I am just so amazed by Spitzer's sensitivity. This infrared view really gives you a sense of the 'lifestyles' of these nearby galaxies," says Kennicutt.

"You get a sense that galaxy classification is not a simple black and white process -- tints of red in galaxies like NGC 3265, show that not all ellipticals are void of dust and star formation, and extremely blue spiral galaxies like NGC 4826, show that some spirals do have a large population of old stars. Like people, galaxies are unique individuals."

The images in this poster are three-color composites where blue depicts the galaxies at a light wavelength of 3.6 microns, while 8.0 microns is green, and 24 microns is red.

Written by Linda Vu, Spitzer Science Center

Spitzer Studies Struggle of Galactic Teenagers

Credit: An artist concept of galaxies colliding
NASA/JPL-Caltech/T. Pyle (SSC)

Billions of years ago, small galaxies across the universe regularly collided -- forcing the gas, dust, stars, and black holes within them to unite. The clashing of galactic gases was so powerful it ignited star formation, while fusing central black holes developed an insatiable appetite for gas and dust.

With stellar nurseries and black holes hungry both for galactic gas, a struggle ensued.

Astronomers have long suspected that these merging structures would eventually grow into some of the most massive galaxies in our universe. Now, NASA's Spitzer Space Telescope has finally identified several of these transitional, or "teenage," galaxies for further study.

"We believe that the most massive galaxies formed through mergers of spiral galaxies like our own Milky Way. Such events were much more common a few billion years after the big bang," says Dr. Anna Sajina, of the Spitzer Science Center in Pasadena, Calif. "This is the epoch we need to look at in order to study the galactic collisions."

Space is like a time machine; the farther away an object is, the further back in time astronomers peer to capture a glimpse of it. Using Spitzer, Sajina looked back to a few billion years after the big bang and spotted galaxies that are nearing the end of the merging process. She notes that these galaxies share a very unique characteristic -- all have massive central black holes that are smothered in dust and producing radio jets.

"What we essentially see in these galaxies is a competition for limited resources. Two processes, star formation and black hole accretion are competing for gas," says Sajina. "At the beginning of the collision, most of the gas will go towards forming stars. Towards the end of the merger, black holes will consume more gas."

According to Sajina, this struggle for resources is relatively short-lived, lasting only ten to 100 million years. Eventually, much of the gas will be pushed out of the galaxy by the powerful winds of newborn stars, stars going supernovae (dying in a cataclysmic explosion), or radio jets shooting out of central supermassive black holes. The removal of gas will stunt the growth of black holes by "starving'' them, and quench star formation.

"The exact process of quenching the extreme star-formation and black hole growth following such merger events is still poorly understood. What we need is to discover sources in the brief transition period after the radio jets have been turned-on, but while the galaxy and its central black holes are still embedded in their dusty cocoon," says Sajina. "The presence of copious amounts of dust in conjunction with strong radio jets in these newly discovered galaxies, makes them prime candidates for being such transition objects."

With Spitzer's supersensitive infrared spectrometer instrument, Sajina's team was able to determine the distance of these galaxies, pinpoint the epoch they live in, and see that they are extremely dusty. After sifting through an astronomical archive called the Sptizer First Look Survey, Sajina also noticed that some of these galaxies also had radio jets.

"The discovery of these transitional objects provides a new avenue for studying the co-evolution [development] of black holes and their host galaxies," she adds.

Sajina's paper was published in the September 2007 issue of Astrophysical Journal. Drs. Lin Yan, Mark Lacy, and Minh Huynh, all of the Spitzer Science Center, were co-authors of the paper.

Two other teams also studied systems like these. A recent study from the Spitzer Space Telescope's Great Observatories Origins Deep Survey (GOODS) also found hundreds of black holes producing X-ray jets, hiding deep inside dusty galaxies billions of light-years away. Their paper was published in the November 10, 2007 issue of Astrophysical Journal.

Results consistent with the GOODS study were also obtained by Fabrizio Fiore of the Osservatorio Astronomico di Roma, Italy, and his team. Their results appear in the Jan. 1, 2008, issue of Astrophysical Journal.

Written by Linda Vu, Spitzer Science Center

"Death Star" Galaxy Black Hole Fires at Neighboring Galaxy

Credit: NASA, ESA, D. Evans (Harvard-Smithsonian Center for Astrophysics),
[X-ray: NASA/CXC/CfA/D.Evans et al.;
Optical/UV: NASA/STScI; Radio: NSF/VLA/CfA/D.Evans et al.,
STFC/JBO/MERLIN]

This composite image shows the jet from a black hole at the center of a galaxy striking the edge of another galaxy, the first time such an interaction has been found. In the image, data from several wavelengths have been combined. X-rays from Chandra (colored purple), optical and ultraviolet (UV) data from Hubble (red and orange), and radio emission from the Very Large Array (VLA) and MERLIN (blue) show how the jet from the main galaxy on the lower left is striking its companion galaxy to the upper right. The jet impacts the companion galaxy at its edge and is then disrupted and deflected, much like how a stream of water from a hose will splay out after hitting a wall at an angle.

Each wavelength shows a different aspect of this system, known as 3C321. The Chandra X-ray image provides evidence that each galaxy contains a rapidly growing supermassive black hole at its center. Hubble's optical light images (orange) show the glow from the stars in each galaxy. A bright spot in the VLA and MERLIN radio image shows where the jet has struck the side of the galaxy - about 20,000 light-years from the main galaxy - dissipating some of its energy. An even larger "hotspot" of radio emission detected by VLA (seen in an image with a much larger field-of-view) reveals that the jet terminates much farther away from the galaxy, at a distance of about 850,000 light-years away. The Hubble UV image shows large quantities of warm and hot gas in the vicinity of the galaxies, indicating the supermassive black holes in both galaxies have had a violent past. Faint emission from Chandra, Hubble and Spitzer, not shown in this image, indicate that the galaxies are orbiting in a clockwise direction, implying that the companion galaxy is swinging into the path of the jet.

Since the Chandra data shows that particle acceleration is still occurring in this hotspot, the jet must have struck the companion galaxy relatively recently, less than about a million years ago (i.e. less than the light travel time to the hotspot). This relatively short cosmic time frame makes this event a very rare phenomenon. This "death star galaxy" will produce large amounts of high-energy radiation, which may cause severe damage to the atmospheres of any planets in the companion galaxy that lie in the path of the jet. From the Earth we look down the barrel of jets from supermassive black holes, however these so-called "blazars" are at much safer distances of millions or billions of light-years.

XMM-Newton Unveils Hidden Cosmic Giant

Credits: ESA/ XMM/ EPIC/ SRON (N. Werner et al.)

X-ray image of the area around the cluster Abell 3128 taken with XMM Newton. The bright spot on the left is hot gas in the recently discovered distant cluster, the spot on the right is hot gas in the cluster Abell 3128.

Astronomers working with XMM-Newton have discovered a new cluster of galaxies, hidden behind a previously identified cluster of galaxies. The recently exposed cosmic giant is apparently just as bright as the first group, but is six times further away.

The discovery was made by an international team using ESA’s orbiting X-ray observatory. Being fooled by a cosmic giant is no laughing matter for an astronomer. For years, astronomers racked their brains over the relation between two regions equally bright and large in X-rays, located in the galaxy cluster known as Abell 3128. “That is the charm of science”, says Norbert Werner, PhD student at SRON Netherlands institute for Space Research. “You always find things that you did not expect.”
Galaxy clusters are the largest structures in the universe. They consist of tens to hundreds of massive galaxies, of which each in turn consists of hundreds of billions of stars. Gravity is the binding factor. The hot cluster gas, at temperatures of tens of millions of degrees Celsius, emits X-rays, which renders the cluster visible for space telescopes such as XMM-Newton. Detailed analyses of these X-rays tell astronomers more about the composition of the gas and accordingly, its origin.

Cosmic Web

Credits: Springel et al., Virgo Consortium

This is a model of the cosmic web.
Clusters of galaxies are expected to develop at the intersections of the web.

What was so intriguing about the two X-ray spots in cluster Abell 3128 was the fact that although they had the same size and brightness, the gas clouds seemed to have completely different compositions.

Werner says, “While one spot was clearly caused by a hot gas cloud rich in metals released by supernova explosions in the galaxies, the other spot seemed to contain a much lower amount of metals than any other cluster previously observed. What we observed completely contradicted the current theories about how large structures in the universe arise.”

The observations with XMM-Newton made the surprise complete. The gas cloud behind the puzzling X-ray spot was found to be 4.6 thousand million light years away, at least six times further than Abell 3128. “We were therefore looking at two completely different objects, which from our perspective were in exactly the same line of sight,” said Werner.

Foam bath

Credits: Werner et al.2007

Image of the area in visible light made by the 6.5-metre Magellan Telescope in Chile. Visible in the centre of this image is the light arc around the very massive galaxy in the centre of the newly found distant cluster. The light arc is caused by the gravity field of the galaxy that works as a lens magnifying an object that lies even much farther away, behind the cluster.

“The research into this large cluster of galaxies mainly centres on the question as to how the large structures of the universe have been formed’, explains project leader Jelle Kaastra. According to current belief, material is spread throughout the universe as a web of thread-like structures of rarefied hot gas - the cosmic web. Between these threads are cavities that are becoming increasingly large as the universe expands. “Compare it to bubbles in a bubble bath”, says the astronomer. The density of material is highest at the intersections in the web. Therefore that is where galaxy clusters develop.

Due to their enormous mass and gravitational attraction, the clusters have their own dynamics. Kaastra says, “They attract each other, collide and fly through each other; a whole host of things happen that we can study with X-ray telescopes such as the XMM-Newton.”

Notes for editors:

SRON Netherlands Institute for Space Research built the Reflection Grating Spectrometer (RGS), capable of analysing the X-rays in detail for ESA’s orbiting X-ray observatory, XMM-Newton. The satellite was launched in 1999 from French Guyana and still functions superbly. The operation of the satellite has recently been extended for five more years, until December 2012.

The results from the research of Norbert Werner and Jelle Kaastra were recently published in the scientific journal Astronomy & Astrophysics. The article ‘Complex X-ray morphology of Abell 3128: a distant cluster behind a disturbed cluster’ is by N. Werner, E. Churazov, A. Finoguenov, M. Markevitch, R. Burenin, J. Kaastra, and H. Böhringer.

Cassini Captures Best View Yet Of Saturn’s Ring Currents

Credit: (All Images)
NASA/Jet Propulsion Laboratory/
Johns Hopkins University Applied Physics Laboratory (NASA/JPL/JHUAPL)

Particle Population in Saturn's Magnetosphere

This is an artist’s concept of the Saturnian plasma sheet based on data from the Cassini Magnetospheric Imaging Instrument. It shows Saturn's embedded “ring current,” an invisible ring of energetic ions trapped in the planet’s magnetic field.

Saturn is at the center, with the red “donut” representing the distribution of dense neutral gas outside Saturn's icy rings. Beyond this region, energetic ions populate the plasma sheet to the dayside magnetopause filling the faintly sketched magnetic flux tubes to higher latitudes and contributing to the ring current. The plasma sheet thins gradually toward the nightside. The view is from above Saturn’s equatorial plane, which is represented by grid lines. The moon Titan’s location is shown for scale. The location of the bow shock is marked, as is the flow of the deflected solar wind in the magnetosheath.

Saturn's ‘Ring Current’

Like Earth, Saturn has an invisible ring of energetic ions trapped in its magnetic field. This feature is known as a “ring current.” This ring current has been imaged with a special, APL-designed camera on Cassini sensitive to energetic neutral atoms.

This is a false color map of the intensity of the energetic neutral atoms emitted from the ring current through a processed called charge exchange. In this process a trapped energetic ion steals and electron from cold gas atoms and becomes neutral and escapes the magnetic field.

The Cassini Magnetospheric Imaging Instrument’s ion and neutral camera records the intensity of the escaping particles, which provides a map of the ring current. In this image, the colors represent the intensity of the neutral emission, which is a reflection of the trapped ions. This “ring” is much farther from Saturn (roughly five times farther) then Saturn’s famous icy rings. Red in the image represents the higher intensity of the particles, while blue is less intense.

Saturn's ring current had not been mapped before on a global scale, only "snippets" or areas were mapped previously but not in this detail. This instrument allows scientists to produce movies that show how this ring changes over time. These movies reveal a dynamic system, which is usually not as uniform as depicted in this image. The ring current is doughnut shaped but in some instances appears as if someone took a bite out of it.

This image was obtained on March 19, 2007, at a latitude of about 54.5 degrees and radial distance of 1.5 million kilometers (920,000 miles). Saturn is at the center, and the dotted circles represent the orbits of the moons Rhea and Titan. The Z axis points parallel to Saturn’s spin axis, the X axis points roughly sunward in the sun–spin axis plane, and the Y axis completes the system, pointing roughly toward dusk. The ion and neutral camera’s field of view is marked by the white line and accounts for the cutoff of the image on the left. The image is an average of the activity over a (roughly) 3-hour period.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Magnetospheric Imaging Instrument was designed, built and is operated by an international team lead by the Johns Hopkins University Applied Physics Laboratory, Laurel, Md. 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 was designed, developed and assembled at JPL.

‘Ring Current’ Rotation

This series of Magnetospheric Imaging Instrument images shows the energetic neutral atom emission from Saturn's ring current. The sun is to lower left (X axis), and the orbits of the moons Titan, Rhea and Dione, and Saturn’s rings, are shown. The pronounced asymmetry (bright emission in the upper quadrant, located between midnight and dawn) rotates with the planet, and the bright spot rotates through 360 degrees over one Saturn rotation (about 10 hours and 40 minutes).

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Magnetospheric Imaging Instrument was designed, built and is operated by an international team lead by the Johns Hopkins University Applied Physics Laboratory, Laurel, Md. 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 was designed, developed and assembled at JPL.

Spiral Galaxy M74

Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)
ESA/Hubble Collaboration
Acknowledgment: R. Chandar (University of Toledo) and J. Miller
(University of Michigan)

Resembling festive lights on a holiday wreath, this NASA/ESA Hubble Space Telescope image of the nearby spiral galaxy M74 is an iconic reminder of the impending season. Bright knots of glowing gas light up the spiral arms, indicating a rich environment of star formation.

Messier 74, also called NGC 628, is a stunning example of a "grand-design" spiral galaxy that is viewed by Earth observers nearly face-on. Its perfectly symmetrical spiral arms emanate from the central nucleus and are dotted with clusters of young blue stars and glowing pink regions of ionized hydrogen (hydrogen atoms that have lost their electrons). These regions of star formation show an excess of light at ultraviolet wavelengths. Tracing along the spiral arms are winding dust lanes that also begin very near the galaxy's nucleus and follow along the length of the spiral arms.

M74 is located roughly 32 million light-years away in the direction of the constellation Pisces, the Fish. It is the dominant member of a small group of about half a dozen galaxies, the M74 galaxy group. In its entirety, it is estimated that M74 is home to about 100 billion stars, making it slightly smaller than our Milky Way.

The spiral galaxy was first discovered by the French astronomer, Pierre Méchain, in 1780. Weeks later it was added to Charles Messier's famous catalog of deep-sky objects.

This Hubble image of M74 is a composite of Advanced Camera for Surveys' data taken in 2003 and 2005. The filters used to create the color image isolate light from blue, visible, and infrared portions of the spectrum, as well as emission from ionized hydrogen (known as HII regions).

A small segment of this image used data from the Canada-France-Hawaii Telescope and the Gemini Observatory to fill in a region that Hubble did not image.

M51 - A Classic Beauty

Credit:
NASA/CXC/Wesleyan Univ./R.Kilgard et al &
NASA/JPL-Caltech &
NASA/ESA/S. Beckwith &
Hubble Heritage Team (STScI/AURA) &
NASA/JPL-Caltech/ Univ. of AZ/R. Kennicutt

M51, whose name comes from being the 51st entry in Charles Messier's catalog, is considered to be one of the classic examples of a spiral galaxy. At a distance of about 30 million light years from Earth, it is also one of the brightest spirals in the night sky. A composite image of M51, also known as the Whirlpool Galaxy, shows the majesty of its structure in a dramatic new way through several of NASA's orbiting observatories. X-ray data from NASA's Chandra X-ray Observatory reveals point-like sources (purple) that are black holes and neutron stars in binary star systems. Chandra also detects a diffuse glow of hot gas that permeates the space between the stars. Optical data from the Hubble Space Telescope (green) and infrared emission from the Spitzer Space Telescope (red) both highlight long lanes in the spiral arms that consist of stars and gas laced with dust. A view of M51 with the GALEX telescope shows hot, young stars that produce lots of ultraviolet energy (blue).

The textbook spiral structure is thought be the result of an interaction M51 is experiencing with its close galactic neighbor, NGC 5195, which is seen just above. Some simulations suggest M51's sharp spiral shape was partially caused when NGC 5195 passed through its main disk about 500 million years ago. This gravitational tug of war may also have triggered an increased level of star formation in M51. The companion galaxy's pull would be inducing extra starbirth by compressing gas, jump-starting the process by which stars form.

Hubble Finds that Extrasolar Planet Has a Hazy Sunset

Image Credit: NASA, ESA, and G. Bacon (STScI)
This is an artist's concept of HD 189733b and its parent star

A team of astronomers, led by Frederic Pont from the Geneva University Observatory in Switzerland, has detected for the first time strong evidence of hazes in the atmosphere of a planet orbiting a distant star. The new Hubble Space Telescope observations were made as the extrasolar planet, dubbed HD 189733b, passed in front of its parent star in an eclipse. As the light from the star briefly passes through the exoplanet's atmosphere, the gases in the atmosphere stamp their unique spectral fingerprints on the starlight.

Where the scientists had expected to see the fingerprints of sodium and potassium, there were none; implying that high-level hazes (with an altitude of nearly 2,000 miles) are responsible for blocking the light from these elements.