Cassini Sees Objects Blazing Trails in Saturn Ring

Images from NASA's Cassini spacecraft have revealed half-mile-sized (kilometer-sized) objects punching through parts of Saturn's F ring, leaving glittering trails behind them. These trails in the rings, which scientists are calling "mini-jets," fill in a missing link in our story of the curious behavior of the F ring

Scientists working with images from NASA's Cassini spacecraft have discovered strange half-mile-sized (kilometer-sized) objects punching through parts of Saturn's F ring, leaving glittering trails behind them. These trails in the rings, which scientists are calling "mini-jets," fill in a missing link in our story of the curious behavior of the F ring. The results will be presented tomorrow at the European Geosciences Union meeting in Vienna, Austria.

"I think the F ring is Saturn's weirdest ring, and these latest Cassini results go to show how the F ring is even more dynamic than we ever thought," said Carl Murray, a Cassini imaging team member based at Queen Mary University of London, England. "These findings show us that the F ring region is like a bustling zoo of objects from a half mile [kilometer] to moons like Prometheus a hundred miles [kilometers] in size, creating a spectacular show."

New images and movies of the mini-jets and other peculiar F ring behavior are available athttp://www.nasa.gov/mission_pages/cassini/whycassini/cassini20120423.html . 

Scientists have known that relatively large objects like Prometheus (as long as 92 miles, or 148 kilometers, across) can create channels, ripples and snowballs in the F ring. But scientists didn't know what happened to these snowballs after they were created, Murray said. Some were surely broken up by collisions or tidal forces in their orbit around Saturn, but now scientists have evidence that some of the smaller ones survive, and their differing orbits mean they go on to strike through the F ring on their own.

These small objects appear to collide with the F ring at gentle speeds - something on the order of about 4 mph (2 meters per second). The collisions drag glittering ice particles out of the F ring with them, leaving a trail typically 20 to 110 miles (40 to 180 kilometers) long. Murray's group happened to see a tiny trail in an image from Jan. 30, 2009 and tracked it over eight hours. The long footage confirmed the small object originated in the F ring, so they went back through the Cassini image catalog to see if the phenomenon was frequent.

"The F ring has a circumference of 550,000 miles [881,000 kilometers], and these mini-jets are so tiny they took quite a bit of time and serendipity to find," said Nick Attree, a Cassini imaging associate at Queen Mary. "We combed through 20,000 images and were delighted to find 500 examples of these rogues during just the seven years Cassini has been at Saturn." 

In some cases, the objects traveled in packs, creating mini-jets that looked quite exotic, like the barb of a harpoon. Other new images show grand views of the entire F ring, showing the swirls and eddies that ripple around the ring from all the different kinds of objects moving through and around it.

2001 Monolith Object Spotted on Mars

Amateur stargazers have discovered an intriguing object jutting out from the surface of Mars. The seemingly perfectly rectangular, upright structure, found in NASA images of the Red Planet, bears a striking resemblance to the monoliths planted on Earth and the moon by aliens in the classic sci-fi film "2001: A Space Odyssey."

NASA's WISE Mission Sees Skies Ablaze With Blazars

Astronomers are actively hunting a class of supermassive black holes throughout the universe called blazars thanks to data collected by NASA's Wide-field Infrared Survey Explorer (WISE). The mission has revealed more than 200 blazars and has the potential to find thousands more.

Blazars are among the most energetic objects in the universe. They consist of supermassive black holes actively "feeding," or pulling matter onto them, at the cores of giant galaxies. As the matter is dragged toward the supermassive hole, some of the energy is released in the form of jets traveling at nearly the speed of light. Blazars are unique because their jets are pointed directly at us.

"Blazars are extremely rare because it's not too often that a supermassive black hole's jet happens to point towards Earth," said Francesco Massaro of the Kavli Institute for Particle Astrophysics and Cosmology near Palo Alto, Calif., and principal investigator of the research, published in a series of papers in the Astrophysical Journal. "We came up with a crazy idea to use WISE's infrared observations, which are typically associated with lower-energy phenomena, to spot high-energy blazars, and it worked better than we hoped." 

The findings ultimately will help researchers understand the extreme physics behind super-fast jets and the evolution of supermassive black holes in the early universe.

WISE surveyed the entire celestial sky in infrared light in 2010, creating a catalog of hundreds of millions of objects of all types. Its first batch of data was released to the larger astronomy community in April 2011 and the full-sky data were released last month. 

Massaro and his team used the first batch of data, covering more than one-half the sky, to test their idea that WISE could identify blazars. Astronomers often use infrared data to look for the weak heat signatures of cooler objects. Blazars are not cool; they are scorching hot and glow with the highest-energy type of light, called gamma rays. However, they also give off a specific infrared signature when particles in their jets are accelerated to almost the speed of light. 

One of the reasons the team wants to find new blazars is to help identify mysterious spots in the sky sizzling with high-energy gamma rays, many of which are suspected to be blazars. NASA's Fermi mission has identified hundreds of these spots, but other telescopes are needed to narrow in on the source of the gamma rays.

Sifting through the early WISE catalog, the astronomers looked for the infrared signatures of blazars at the locations of more than 300 gamma-ray sources that remain mysterious. The researchers were able to show that a little more than half of the sources are most likely blazars. 

"This is a significant step toward unveiling the mystery of the many bright gamma-ray sources that are still of unknown origin," said Raffaele D'Abrusco, a co-author of the papers from  Harvard Smithsonian Center for Astrophysics in Cambridge, Mass. "WISE's infrared vision is actually helping us understand what's happening in the gamma-ray sky." 

The team also used WISE images to identify more than 50 additional blazar candidates and observed more than 1,000 previously discovered blazars. According to Massaro, the new technique, when applied directly to WISE's full-sky catalog, has the potential to uncover thousands more. 

"We had no idea when we were building WISE that it would turn out to yield a blazar gold mine," said Peter Eisenhardt, WISE project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., who is not associated with the new studies. "That's the beauty of an all-sky survey. You can explore the nature of just about any phenomenon in the universe."

Cosmic 'Leaf Blower' Robs Galaxy of Star-Making Fuel (Route for Spirals to Ellipticals?)

Time is running out for the galaxy NGC 3801, seen in this composite image combining light from across the spectrum, ranging from ultraviolet to radio. NASA's Galaxy Evolution Explorer and other instruments have helped catch the galaxy NGC 3801 in the act of destroying its cold, gaseous fuel for new stars. Astronomers believe this marks the beginning of its transition from a vigorous spiral galaxy to a quiescent elliptical galaxy whose star-forming days are long past. Image credit: NASA/JPL-Caltech/SDSS/NRAO/ASIAA 


Supernova explosions and the jets of a monstrous black hole are scattering a galaxy's star-making gas like a cosmic leaf blower, a new study finds. The findings, which relied on ultraviolet observations from NASA's Galaxy Evolution Explorer and a host of other instruments, fill an important gap in the current understanding of galactic evolution. 

It has long been known that gas-rich spiral galaxies like our Milky Way smash together to create elliptical galaxies such as the one observed in the study. These big, round galaxies have very little star formation. The reddish glow of aging stars comes to dominate the complexion of elliptical galaxies, so astronomers refer to them as "red and dead." 

The process that drives the dramatic transformation from spiral galactic youth to elderly elliptical is the rapid loss of cool gas, the fuel from which new stars form. Supernova explosions can start the decline in star formation, and then shock waves from the supermassive black hole finish the job. Now astronomers think they have identified a recently merged galaxy where this gas loss has just gotten underway.

"We have caught a galaxy in the act of destroying its gaseous fuel for new stars and marching toward being a red-and-dead type of galaxy," said Ananda Hota, lead author of a new paper in the Monthly Notices of the Royal Astronomical Society. Hota, an astronomer in Pune, India, conducted the study as a post-doctoral research fellow at the Institute of Astronomy & Astrophysics at Academia Sinica in Taipei, Taiwan. 

"We have found a crucial missing piece to connect and solve the puzzle of this phase of galaxy evolution," Hota added. 

The supermassive black holes that reside in the centers of galaxies can flare up when engorged by gas during galactic mergers. As a giant black hole feeds, colossal jets of matter shoot out from it, giving rise to what is known as an active galactic nucleus. According to theory, shock waves from these jets heat up and disperse the reservoirs of cold gas in elliptical galaxies, thus preventing new stars from taking shape.     

The galaxy Hota and his team looked at, called NGC 3801, shows signs of such a process. NGC 3801 is unique in that evidence of a past merger is clearly seen, and the shock waves from the central black hole's jets have started to spread out very recently. The researchers used the Galaxy Evolution Explorer to determine the age of the galaxy's stars and decipher its evolutionary history. The ultraviolet observations show that NGC 3801's star formation has petered out over the last 100 to 500 million years, demonstrating that the galaxy has indeed begun to leave behind its youthful years. The lack of many big, new, blue stars makes NGC 3801 look yellowish and reddish in visible light, and thus middle-aged. 

What's causing the galaxy to age and make fewer stars? The short-lived blue stars that formed right after it merged with another galaxy have already blown up as supernovae. Data from NASA's Hubble Space Telescope revealed that those stellar explosions have triggered a fast outflow of heated gas from NGC 3801's central regions. That outflow has begun to banish the reserves of cold gas, and thus cut into NGC 3801's overall star making. 

Some star formation is still happening in NGC 3801, as shown in ultraviolet wavelengths observed by the Galaxy Evolution Explorer, and in infrared wavelengths detected by NASA's Spitzer Space Telescope. But that last flicker of youth will soon be extinguished by colossal shock waves from the black hole's jets, seen in X-ray light by NASA's Chandra X-ray Observatory. These blast waves are rushing outward from the galactic center at a velocity of nearly two million miles per hour (nearly 900 kilometers per second). The waves will reach the outer portions of NGC 3801 in about 10 million years, scattering any remaining cool hydrogen gas and rendering the galaxy truly red and dead.

Astronomers think the transition captured early-on in the case of NGC 3801 -- from the merger of gas-rich galaxies to the rise of an old-looking elliptical -- happens very quickly on cosmic time scales. 

"The quenching of star formation by feedback from the active galactic nucleus probably occurs in just a billion years. That's not very long compared to the 10-billion-year age of a typical big galaxy," said Hota. "The explosive shock wave event caused by the central black hole is so powerful that it can dramatically change the future course of the evolution of an entire galaxy."

Gallery of Surface Features on Vesta

Slideshow of features here...

http://www.jpl.nasa.gov/news/news.cfm?release=2012-082&cid=release_2012-082&msource=12082

Astronomers Find Cosmic Lenses with Feeding Black Holes

The Hubble Space Telescope's sharp view was used to look for gravitational arcs and rings (indicated by arrows), which are produced when one galaxy acts as a lens to magnify and distort the appearance of another galaxy behind it. In this case, the foreground galaxies contain actively accreting black holes called quasars. Image credit: NASA, ESA, EPFL (Switzerland)


In space, it sometimes happens that two galaxies are aligned in just the right way that the closer galaxy distorts and magnifies the appearance of the one behind it. For astronomers, finding these alignments is like coming across giant, cosmic magnifying glasses. 

Now, a team of astronomers, including Daniel Stern from NASA's Jet Propulsion Laboratory in Pasadena, Calif., has found several rare examples of this phenomenon, called gravitational lensing, in which the foreground galaxy hosts an actively accreting supermassive black hole. 

Such feeding black holes, called quasars, are among the brightest objects in the universe, far outshining the total starlight of their host galaxies. Because they are so bright, it is hard for astronomers to measure the mass of their host galaxies. However, gravitational lenses are invaluable for estimating the mass of a quasar's host galaxy. The amount of the background galaxy's distortion can be used to accurately measure the lensing galaxy's mass. 

The team hopes to build an even bigger catalog of these quasar lenses, and to use these data to better understand the interplay between black hole feeding and star formation in galaxy evolution.

NASA Releases New WISE Mission Catalog of Entire Infrared Sky

ASA unveiled a new atlas and catalog of the entire infrared sky today showing more than a half billion stars, galaxies and other objects captured by the Wide-field Infrared Survey Explorer (WISE) mission. 

"Today, WISE delivers the fruit of 14 years of effort to the astronomical community," said Edward Wright, WISE principal investigator at UCLA, who first began working on the mission with other team members in 1998. 

WISE launched Dec. 14, 2009, and mapped the entire sky in 2010 with vastly better sensitivity than its predecessors. It collected more than 2.7 million images taken at four infrared wavelengths of light, capturing everything from nearby asteroids to distant galaxies. Since then, the team has been processing more than 15 trillion bytes of returned data. A preliminary release of WISE data, covering the first half of the sky surveyed, was made last April. 

The WISE catalog of the entire sky meets the mission's fundamental objective. The individual WISE exposures have been combined into an atlas of more than 18,000 images covering the sky and a catalog listing the infrared properties of more than 560 million individual objects found in the images. Most of the objects are stars and galaxies, with roughly equal numbers of each. Many of them have never been seen before. 

WISE observations have led to numerous discoveries, including the elusive, coolest class of stars. Astronomers hunted for these failed stars, called "Y-dwarfs," for more than a decade. Because they have been cooling since their formation, they don't shine in visible light and could not be spotted until WISE mapped the sky with its infrared vision. 

WISE also took a poll of near-Earth asteroids, finding there are significantly fewer mid-size objects than previously thought. It also determined NASA has found more than 90 percent of the largest near-Earth asteroids. 

Other discoveries were unexpected. WISE found the first known "Trojan" asteroid to share the same orbital path around the sun as Earth. One of the images released today shows a surprising view of an "echo" of infrared light surrounding an exploded star. The echo was etched in the clouds of gas and dust when the flash of light from the supernova explosion heated surrounding clouds. At least 100 papers on the results from the WISE survey already have been published. More discoveries are expected now that astronomers have access to the whole sky as seen by the spacecraft. 

"With the release of the all-sky catalog and atlas, WISE joins the pantheon of great sky surveys that have led to many remarkable discoveries about the universe," said Roc Cutri, who leads the WISE data processing and archiving effort at the Infrared and Processing Analysis Center at the California Institute of Technology in Pasadena. "It will be exciting and rewarding to see the innovative ways the science and educational communities will use WISE in their studies now that they have the data at their fingertips."