Cassini Captures a Rarely-Seen Moon

While many of us here on Earth were waiting for the Moon to take a bite out of the Sun this past Sunday, Cassini was doing some moon watching of its own, 828.5 million miles away!

The image above is a color-composite raw image of Methone (pronounced meh-tho-nee), a tiny, egg-shaped moon only 2 miles (3 km) across. Discovered by Cassini in 2004, Methone’s orbit lies between Mimas and Enceladus, at a distance of 120,546 miles (194,000 km) from Saturn — that’s about half the distance between Earth and the Moon.

At an altitude of 1,200 miles (1900 km) this was Cassini’s closest pass ever of Methone, a rare visit that occurred after the spacecraft departed the much larger Tethys.

Along with sister moons Pallene and Anthe, Methone is part of a group called the Alkyonides, named after daughters of the god Alkyoneus in Greek mythology. The three moons may be leftovers from a larger swarm of bodies that entered into orbit around Saturn — or they may be pieces that broke off from either Mimas or Enceladus.

Earlier on Sunday, May 20, Cassini paid a relatively close visit to Tethys (pronounced tee-this), a 662-mile (1065-km) -wide moon made almost entirely of ice. One of the most extensively cratered worlds in the Solar System, Tethys’ surface is dominated by craters of all sizes — from the tiniest to the giant 250-mile (400-km) -wide Odysseus crater — as well as gouged by the enormous Ithaca Chasma, a series of deep valleys running nearly form pole to pole.

Cassini passed within 34,000 miles (54,000 km) of Tethys on May 20, before heading to Methone and then moving on to its new path toward Titan, a trajectory that will eventually take it up out of Saturn’s equatorial plane into a more inclined orbit in order to better image details of the rings and  Saturn’s poles.

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NASA mission to go on with private funding

For nine years the Galaxy Evolution Explorer surveyed the sky with ultraviolet eyes in a NASA mission to catalog hundreds of millions of galaxies spanning 10 billion years of cosmic time.

The spacecraft was placed in standby mode Feb. 7 while NASA and Caltech worked out a Space Act Agreement, signed May 14, to allow the university to resume spacecraft operations and data management for the mission, the agency reported.

"NASA sees this as an opportunity to allow the public to continue reaping the benefits from this space asset that NASA developed using federal funding," said Paul Hertz, director of the agency's astrophysics division at NASA headquarters in Washington.

"This is an excellent example of a public/private partnership that will help further astronomy in the United States."Under the agreement, NASA maintains ownership and liability for the spacecraft until Caltech completes science activities, at which time it will decommission the spacecraft for NASA.The mission's batteries and solar panels have an expected lifetime of 12 years or more, NASA said.

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Mojave Desert Tests Prepare for NASA Mars Roving

Team members of NASA's Mars Science Laboratory mission took a test rover to Dumont Dunes in California's Mojave Desert this week to improve knowledge of the best way to operate a similar rover, Curiosity, currently flying to Mars for an August landing.

The test rover that they put through paces on various sandy slopes has a full-scale version of Curiosity's mobility system, but it is otherwise stripped down so that it weighs about the same on Earth as Curiosity will weigh in the lesser gravity of Mars.

Information collected in these tests on windward and downwind portions of dunes will be used by the rover team in making decisions about driving Curiosity on dunes near a mountain in the center of Gale Crater.

First, however, the Mars Science Laboratory spacecraft, launched Nov. 26, 2011, must put Curiosity safely onto the ground. Safe landing on Mars is never assured, and this mission will use innovative methods to land the heaviest vehicle in the smallest target area ever attempted on Mars. Advances in landing heavier payloads more precisely are steps toward eventual human missions to Mars.

Curiosity is on track for landing the evening of Aug. 5, 2012, PDT (early on Aug. 6, Universal Time and EDT) to begin a two-year prime mission. Researchers plan to use Curiosity to study layers in Gale Crater's central mound, Mount Sharp. The mission will investigate whether the area has ever offered an environment favorable for microbial life.

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for the NASA Science Mission Directorate, Washington. 

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NASA finds mysterious “hidden” planet

NASA’s Kepler mission continues to discover new, mysterious planets in the depths of space, with the space telescope identifying an “unseen” Super-Earth thanks to its blocking of a distant star. Kepler identifies possible planets from their repeat movement in front of stars, tracking the periodic dimming of the star itself rather than attempting to spot the much darker planet. Parent star KOI-872 (Kepler Object of Interest no.872) had shown a surprising erraticism in its dimming, MSNBC reports, with the actual movement varying by up to a few hours.

Kepler had originally indicated a single planet in orbit around KOI-872, with a transition period of once every 34 days. ”The planet should show transits equally spaced, which is not the case,” astronomer David Nesvorny of the Southwest Research Institute in Boulder, Colo. said of the research. “Sometimes the transit is two hours late, sometimes two hours early.”

Computer modeling suggested the time difference could, in fact, be because of a second planet in orbit, much closer to the sun than the first. In fact, astronomers believe there’s a 99-percent chance of a second, Saturn-sized object orbiting the sun every 57 days; “this is the first occasion where there is great confidence that the [computer modeling] method works” Nesvorny says.

The scientists have now moved on to identifying so-called exomoons, which orbit planets just as our own moon orbits the Earth.

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100 Days and Counting to NASA's Curiosity Mars Rover Landing

At 10:31 p.m. PDT today, April 27, (1:31 p.m. EDT), NASA's Mars Science Laboratory, carrying the one-ton Curiosity rover, will be within 100 days from its appointment with the Martian surface. At that moment, the mission has about 119 million miles (191 million kilometers) to go and is closing at a speed of 13,000 mph (21,000 kilometers per hour).

"Every day is one day closer to the most challenging part of this mission," said Pete Theisinger, Mars Science Laboratory project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Landing an SUV-sized vehicle next to the side of a mountain 85 million miles from home is always stimulating. Our engineering and science teams continue their preparations for that big day and the surface operations to follow."

On Sunday, April 22, a week-long operational readiness test concluded at JPL. The test simulated aspects of the mission's early surface operations. Mission planners and engineers sent some of the same commands they will send to the real Curiosity rover on the surface of Mars to a test rover used at JPL.

"Our test rover has a central computer identical to Curiosity's currently on its way to Mars," said Eric Aguilar, the mission's engineering test lead at JPL. "We ran all our commands through it and watched to make sure it drove, took pictures and collected samples as expected by the mission planners. It was a great test and gave us a lot of confidence moving forward."

The Mars Science Laboratory spacecraft, launched Nov. 26, 2011, will deliver Curiosity to the surface of Mars on the evening of Aug. 5, 2012, PDT (early on Aug. 6, Universal Time and EDT) to begin a two-year prime mission. Curiosity's landing site is near the base of a mountain inside Gale Crater, near the Martian equator. Researchers plan to use Curiosity to study layers in the mountain that hold evidence about wet environments of early Mars. 

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NASA's Chandra Sees Remarkable Outburst From Old Black Hole

An extraordinary outburst produced by a black hole in a nearby galaxy has provided direct evidence for a population of old, volatile stellar black holes. The discovery, made by astronomers using NASA's Chandra X-ray Observatory, provides new insight into the nature of a mysterious class of black holes that can produce as much energy in X-rays as a million suns radiate at all wavelengths.

Researchers used Chandra to discover a new ultraluminous X-ray source, or ULX. These objects give off more X-rays than most binary systems, in which a companion star orbits the remains of a collapsed star. These collapsed stars form either a dense core called a neutron star or a black hole.

The extra X-ray emission suggests ULXs contain black holes that might be much more massive than the ones found elsewhere in our galaxy.

The companion stars to ULXs, when identified, are usually young, massive stars, implying their black holes are also young. The latest research, however, provides direct evidence that ULXs can contain much older black holes and some sources may have been misidentified as young ones.

The intriguing new ULX is located in M83, a spiral galaxy about 15 million light years from Earth, discovered in 2010 with Chandra. Astronomers compared this data with Chandra images from 2000 and 2001, which showed the source had increased in X-ray brightness by at least 3,000 times and has since become the brightest X-ray source in M83.

The sudden brightening of the M83 ULX is one of the largest changes in X-rays ever seen for this type of object, which do not usually show dormant periods. No sign of the ULX was found in historical X-ray images made with Einstein Observatory in 1980, ROSAT in 1994, the European Space Agency's XMM-Newton in 2003 and 2008, or NASA's Swift observatory in 2005.

"The flaring up of this ULX took us by surprise and was a sure sign we had discovered something new about the way black holes grow," said Roberto Soria of Curtin University in Australia, who led the new study. The dramatic jump in X-ray brightness, according to the researchers, likely occurred because of a sudden increase in the amount of material falling into the black hole.

In 2011, Soria and his colleagues used optical images from the Gemini Observatory and NASA's Hubble Space Telescope to discover a bright blue source at the position of the X-ray source. The object had not been previously observed in a Magellan Telescope image taken in April 2009 or a Hubble image obtained in August 2009.

The lack of a blue source in the earlier images indicates the black hole's companion star is fainter, redder and has a much lower mass than most of the companions that previously have been directly linked to ULXs. The bright, blue optical emission seen in 2011 must have been caused by a dramatic accumulation of more material from the companion star.

"If the ULX only had been observed during its peak of X-ray emission in 2010, the system easily could have been mistaken for a black hole with a massive, much younger stellar companion, about 10 to 20 million years old," said co-author William Blair of Johns Hopkins University in Baltimore.

The companion to the black hole in M83 is likely a red giant star at least 500 million years old, with a mass less than four times the sun's. Theoretical models for the evolution of stars suggest the black hole should be almost as old as its companion.

Another ULX containing a volatile, old black hole recently was discovered in the Andromeda galaxy by Amanpreet Kaur, from Clemson University, and colleagues and published in the February 2012 issue of Astronomy and Astrophysics.

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