June 27, 2007, 6:03 AM CT

NASA's Swift Sees Double Supernova in Galaxy

In just the past six weeks, two supernovae have flared up in an obscure galaxy in the constellation Hercules. Never before have astronomers observed two of these powerful stellar explosions occurring in the same galaxy so close together in time.

The galaxy, known as MCG +05-43-16, is 380 million light-years from Earth. Until this year, astronomers had never sighted a supernova popping off in this stellar congregation. A supernova is an extremely energetic and life-ending explosion of a star.

Making the event even more unusual is the fact that the two supernovae belong to different types. Supernova 2007ck is a Type II event - which is triggered when the core of a massive star runs out of nuclear fuel and collapses gravitationally, producing a shock wave that blows the star to smithereens. Supernova 2007ck was first observed on May 19.

In contrast, Supernova 2007co is a Type Ia event, which occurs when a white dwarf star accretes so much material from a binary companion star that it blows up like a giant thermonuclear bomb. It was discovered on June 4, 2007. A white dwarf is the exposed core of a star after it has ejected its atmosphere; it's approximately the size of Earth but with the mass of our Sun.

"Most galaxies have a supernova every 25 to 100 years, so it's remarkable to have a galaxy with two supernovae discovered just 16 days apart," says Stefan Immler of NASA's Goddard Space Flight Center. In 2006 Immler used NASA's Swift satellite to image two supernovae in the elliptical galaxy NGC 1316, but both of those explosions were Type Ia events, and they were discovered six months apart......... Posted by: Sean      Read more         Source

June 20, 2007, 11:06 AM CT

Plant Life On Extrasolar Earthlike Planets

When we think of extrasolar Earth-like planets, the first tendency is to imagine weird creatures like Jar Jar Binks, Chewbacca, and, if those are not bizarre enough, maybe even the pointy-eared Vulcan, Spock, of Star Trek fame.

But scientists seeking clues to life on extrasolar planets are studying various biosignatures found in the light spectrum leaking out to Earth to speculate on something more basic and essential than the musical expertise of Droopy McCool. They are speculating on what kind of photosynthesis might occur on such planets and what the extrasolar plants might look like.

Paint it black

It could be the plants are black, says Robert Blankenship, Ph.D., Lucille P. Markey Distinguished Professor in Arts & Sciences at Washington University in St. Louis. But it all depends on what size and light intensity of star - or sun - the planet feeds off, and the extrasolar planet's atmospheric chemistry.

Plants on Earth are green because of chlorophyll, which harnesses the energy of the sun to make sugars for metabolism. But our plants aren't completely efficient - they waste a little bit of light.

"Ideally, what you want is a black molecule that absorbs all of the light," Blankenship said. "There could be another system developed on an extrasolar planet where plants are completely black if the spectrum of light that's available to organisms is different from the light available to organisms on Earth......... Posted by: Sean      Read more         Source

June 20, 2007, 10:17 AM CT

New Technique for Observing Faint Companions

Observing the image of a faint object that lies close to a star is a demanding task as the object is generally hidden in the glare of the star. Characterising this object, by taking spectra, is an even harder challenge. Still, thanks to ingenious researchers and a new ESO imaging spectrograph, this is now feasible, paving the way to an eldorado of a number of new thrilling discoveries.

These very high contrast observations are fundamental for directly imaging unknown extra-solar planets (i.e. planets orbiting a star other than the Sun), as well as low-mass stars and brown dwarfs, those failed stars that are too small to start burning hydrogen into helium.

Astronomer Niranjan Thatte and colleagues developed a new method for exactly this purpose. The basis of the concept is relatively simple: while the positions of most of the features linked to the host star and artefacts produced by the telescope and the instrument scale with the wavelength, the location of a faint companion does not. So if the image has an internal reflection of the star masquerading as a planet, this phantom planet will be in one location in the image when looking in red light, and another when looking in blue; a real planet will stay at the same place no matter what colour of light one examines. Therefore, with the combined detection of spectra and position, one can see what is scaling, subtract it, and be left with what is fixed, that is the target dim object. Such observations can be done with specific instruments, called 'integral field spectrographs', such as the SINFONI instrument on ESO's VLT. This technique, termed Spectral Deconvolution (SD), eventhough first proposed in 2002 for space-based applications, has never been applied to obtain spectra of a real object until now......... Posted by: Sean      Read more         Source

June 10, 2007, 9:20 PM CT

Gazing up at the Man in the Star?

Using a suite of four telescopes, astronomers have captured an image of Altair, one of the closest stars to our own and a fixture in the summer sky.

While astronomers have recently imaged a few of the enormous, dying, red-giant stars, this is the first time anyone has seen the surface of a relatively tiny hydrogen-burning star like our own sun.

"The galaxy is shaped by the effects of relatively rare but powerful hot, rapidly rotating stars," says John Monnier of the University of Michigan, the lead author on the study that will appear on Science Express on May 31, 2007. "These stars have more in common with Altair than our own sun and understanding Altair will allow us to better understand how these influential stars scattered throughout the galaxy operate".

Monnier was part of an international team of astronomers that captured the image using four of the six telescopes at a facility on Mt. Wilson, Calif., operated by the Center for High Angular Resolution Astronomy (CHARA) at Georgia State University in Atlanta with partial support from the National Science Foundation (NSF).

The CHARA telescopes were able to make the breakthrough observation because they were outfitted with a novel system to clean up some of the distortions from Earth's atmosphere, a technology called the Michigan Infrared Combiner, developed with NSF support at the University of Michigan in Ann Arbor. Recent advances in fiber optic telecommunication technology made this new combiner possible......... Posted by: Sean      Read more         Source

June 5, 2007, 0:19 AM CT

Gearing Up For Mercury Mission Flyby Of Venus

University of Colorado at Boulder scientists will scan Venus during a spacecraft flyby this week using an $8.7 million instrument they designed and built for NASA's MESSENGER Mission, launched in 2004 and speeding toward Mercury.

Built by CU-Boulder's Laboratory for Atmospheric and Space Physics, the instrument will make measurements of the thick clouds and shrouded surface of Venus during the June 5th flyby, said LASP Senior Research Associate William McClintock, a mission co-investigator who led the CU-Boulder instrument development team. Known as the Mercury Atmospheric and Surface Composition Spectrometer, or MASCS, the instrument will compare the atmosphere of Venus with data from other spacecraft that have visited the planet in the past four decades.

"This is our first opportunity for a close flyby of a solar system object with MESSENGER, and we should be able to tell if the atmosphere of Venus has been changing in recent years, " said McClintock. "As importantly, we are using Venus as a test case to learn more about our instrument performance in preparation for the spacecraft's ultimate destination of Mercury".

Carrying seven instruments, MESSENGER will be the first spacecraft ever to orbit Mercury and the first to return data from the hot, rocky planet in more than 30 years. The circuitous, 4.9 billion mile journey to Mercury, which requires more than seven years and 13 loops around the sun, is using the gravity of Venus during its flyby this week to guide it closer to Mercury's orbit......... Posted by: Sean      Read more         Source

May 22, 2007, 9:42 PM CT

Cassini 'CAT Scan' maps clumps in Saturn's rings

Saturn's largest and most densely packed ring is composed of dense clumps of particles separated by nearly empty gaps, as per new findings from NASA's Cassini spacecraft.

These clumps in Saturn's B ring are neatly organized and constantly colliding, which surprised scientists.

Prior interpretations assumed the ring particles were distributed uniformly and so researchers underestimated the total mass of Saturn's rings. The mass may actually be two or more times prior estimates.

"These results will help us understand the overall question of the age and hence the origin of Saturn's rings," said Josh Colwell, assistant professor of physics at the University of Central Florida and a member of the Cassini ultraviolet imaging spectrograph team publishing its results in the journal Icarus this month.

Principal investigator Larry Esposito at the University of Colorado, Boulder is fascinated with the findings.

"The rings are different from the picture we had in our minds," Esposito said. "We originally thought we would see a uniform cloud of particles. Instead we find that the particles are clumped together with empty spaces in between. If you were flying under Saturn's rings in an airplane, you would see these flashes of sunlight come through the gaps, followed by dark and so forth. This is different from flying under a uniform cloud of particles."........ Posted by: Sean      Read more         Source

May 21, 2007, 12:39 AM CT

Breathtaking views of Deuteronilus Mensae

The High Resolution Stereo Camera (HRSC) on board ESA's Mars Express has captured breathtaking images of the Deuteronilus Mensae region on Mars.

The images were taken on 14 March 2005 during orbit number 1483 of the Mars Express spacecraft with a ground resolution of approximately 29 metres per pixel.

They show the Deuteronilus Mensae region, located on the northern edge of Arabia Terra and bordering the southern highlands and the northern lowlands. Situated at approximately 39 degree North and 23 degree East, Deuteronilus Mensae are primarily characterised by glacial features. The scene is illuminated by the Sun from the south-west (from bottom left in the image).

The scene is dominated by a depression measuring approximately 2 000 metres in depth and 110 kilometres in diameter, north to south.

Visible in the centre of the first image, the interior of the depression is characterised by dark material, differing from the light-toned surrounding plains.

Deeply incised valleys of a depth ranging from 800 to 1 200 metres are clearly identifiable in the northern part of the scene. Deeply incised valleys with a depth ranging from 800 to 1 200 metres are clearly identifiable in the northern part of the scene.

It is believed that these valleys may have originated due to intense flooding by melted water ice. The water then froze rather quickly, flowing down the slopes of the depression like a glacier. Aeolian sediments (eroded by the action of wind) traced the flow pattern on the surface......... Posted by: Sean      Read more         Source

May 17, 2007, 7:25 PM CT

Two Supermassive Black Holes In Colliding Galaxies

Astronomers, including UC Riversides Gabriela Canalizo, have used powerful adaptive optics technology at the W. M. Keck Observatory in Hawaii to reveal the precise locations and environments of a pair of supermassive black holes at the center of an ongoing collision between two galaxies 300 million light-years away.

The new observations of the galaxy merger known as NGC 6240 reveal that each of the black holes resides at the center of a rotating disk of stars and is surrounded by a cloud of young star clusters formed in the merger.

Findings from the study are published online in Science Express today; in print in Science at a date to be determined.

"The study of the interplay between galaxy mergers, star formation, and activity from accreting black holes is crucial to our understanding of how the universe evolved to the galaxies and structures we see today," said Canalizo, an assistant professor of physics in UCRs Institute of Geophysics and Planetary Physics

Canalizo, the second author of the research paper, worked with Claire E. Max, the papers lead author, as a postdoctoral researcher at Lawrence Livermore National Laboratory (LLNL) from 2000 to 2003. Willem H. de Vries, a physicist at LLNL and UC Davis, is also a coauthor......... Posted by: Sean      Read more         Source

May 16, 2007, 10:39 PM CT

Cracks on Enceladus

Cracks in the icy surface of Saturn's moon Enceladus open and close daily under the pull of Saturn's gravity, as per new calculations by NASA-sponsored researchers.

"Tides generated by Saturn's gravity could control the timing of eruptions from cracks in the southern hemisphere of Enceladus," said Dr. Terry Hurford of NASA's Goddard Space Flight Center, Greenbelt, Md. Hurford is lead author of a paper on this research appearing in Nature May 17. This paper is one of two studies on Enceladus in this issue of Nature. The other paper explains that tidal forces cause the sides of the cracks to rub together and produce enough heat to vaporize ice into plumes that jettison off the moon, scientists suggest.

In 2005, the Cassini spacecraft flew by Enceladus and saw plumes of material erupting from the south pole of Enceladus. Researchers were surprised to see this because eruptions are powered by heat from an object's interior. Enceladus is tiny in comparison to most moons, only about 500 kilometers (310 miles) in diameter, so it should have lost its interior heat to the cold of space long ago.

A closer look by Cassini revealed a series of 120-kilometer (75-mile) long cracks in the south polar region of Enceladus, which were nicknamed "Tiger Stripes" because they resembled a tiger's distinctive marks. The stripes are warmer than their surroundings, so researchers believe they are the source of the eruptions. The Cassini observations also show the plumes consist of water vapor, so there is evidence for liquid water under the ice. Since liquid water is necessary to support known forms of life, Enceladus has become a promising place to look for extraterrestrial life......... Posted by: Sean      Read more         Source

May 10, 2007, 10:19 PM CT

A New Way To Investigate Exploding Stars

ESA's X-ray observatory XMM-Newton has revealed a new class of exploding stars - where the X-ray emission 'lives fast and dies young'.

The identification of this particular class of explosions gives astronomers a valuable new constraint to help them model and understand stellar explosions.

Exploding stars called novae remain a puzzle to astronomers. "Modelling these outbursts is very difficult," says Wolfgang Pietsch of the Max Planck Institut für Extraterrestrische Physik. Now, ESA's XMM-Newton and NASA's Chandra space-borne X-ray observatories have provided valuable information about when individual novae emit X-rays.

Between July 2004 and February 2005, the X-ray observatories watched the heart of the nearby galaxy, Andromeda, also known to astronomers as M31. During that time, Pietsch and colleagues monitored novae, looking for the X-rays.

They detected that eleven out of the 34 novae that had exploded in the galaxy during the prior year were shining X-rays into space. "X-rays are an important window onto novae. They show the atmosphere of the white dwarf," says Pietsch.

White dwarfs are hot stellar corpses left behind after the rest of the star has been ejected into space. A typical white dwarf contains about the mass of the Sun, in a spherical volume little bigger than the Earth. Given its density, it has a strong pull of gravity. If in orbit around a normal star, it may rip gas from the star......... Posted by: Sean      Read more         Source