An artist's conception of stars moving in the central regionsof a giant elliptical galaxy that harbors a black hole.
"Astronomers Find Biggest Black Holes Yet" by DENNIS OVERBYE, New York Times 12/5/2011
Excerpt
Astronomers are reporting that they have taken the measure of the biggest, baddest black holes yet found in the universe, abyssal yawns 10 times the size of our solar system into which billions of Suns have vanished like a guilty thought.
Such holes, they say, might be the gravitational cornerstones of galaxies and clues to the fates of violent quasars, the almost supernaturally powerful explosions in the hearts of young galaxies that dominated the early years of the universe.
One of these newly surveyed monsters, which weighs as much as 21 billion Suns, is in an egg-shaped swirl of stars known as NGC 4889, the brightest galaxy in a sprawling cloud of thousands of galaxies about 336 million light-years away in the Coma constellation.
The other black hole, a graveyard for the equivalent of 9.7 billion Suns, more or less, lurks in the center of NGC 3842, a galaxy that anchors another cluster known as Abell 1367, about 331 million light-years away in Leo.
“These are the most massive reliably measured black holes ever,” Nicholas J. McConnell, a graduate student at the University of California, Berkeley, said in an e-mail, referring to the new observations.
These results are more than just cool and record-setting. Observations with the Hubble Space Telescope over the years have shown that such monster black holes seem to inhabit the centers of all galaxies — the bigger the galaxy, the bigger the black hole. Researchers said the new work could shed light on the role these black holes play in the formation and evolution of galaxies.
"Planet found orbiting habitable zone of sun-like star" by Irene Klotz, Reuters 12/6/2011
The most Earth-like planet ever discovered is circling a star 600 light years away, a key finding in an ongoing quest to learn if life exists beyond Earth, scientists said on Monday.
The planet, called Kepler-22b, joins a list of more than 500 planets found to orbit stars beyond our solar system. It is the smallest and the best positioned to have liquid water on its surface -- among the ingredients necessary for life on Earth.
"We are homing in on the true Earth-sized, habitable planets," said San Jose State University astronomer Natalie Batalha, deputy science team lead for NASA's Kepler Space Telescope that discovered the star.
The telescope, which was launched three years ago, is staring at about 150,000 stars in the constellations Cygnus and Lyra, looking for faint and periodic dimming as any circling planets pass by, relative to Kepler's line of sight.
Results will be extrapolated to determine the percentage of stars in the Milky Way galaxy that harbor potentially habitable, Earth-size planets.
This is the first detection of a potentially habitable world orbiting a Sun-like star, scientists reported in findings to be published in The Astrophysical Journal.
Kepler-22b is 600 light years away. A light year is the distance light travels in a year, about 6 trillion miles (10 trillion km).
GROUND TELESCOPES
Planets about the same distance from their parent stars as Earth take roughly a year to complete an orbit. Scientists want to see at least three transits to be able to rule out other explanations for fluctuations in a star's light, such as small companion stars. Results also are verified by ground and other space telescopes.
Kepler-22b, which is about 2.4 times the radius of Earth, sits squarely in its star's so-called "habitable zone," the region where liquid water could exist on the surface. Follow-up studies are under way to determine if the planet is solid, like Earth, or more gaseous like Neptune.
"We don't know anything about the planets between Earth-size and Neptune-size because in our solar system we have no examples of such planets. We don't know what fraction are going to be rocky, what fraction are going to be water worlds, what fraction are ice worlds. We have no idea until we measure one and see," Batalha said at a news conference at NASA Ames Research Center in Moffet Field, California.
If Kepler-22b has a surface and a cushion of atmosphere similar to Earth's, it would be about 72 degrees Fahrenheit (22 C), about the same as a spring day in Earth's temperate zone.
Among the 2,326 candidate planets found by the Kepler team, 10 are roughly Earth-size and reside in their host stars' habitable zones.
Another team of privately funded astronomers is scanning the target stars for non-naturally occurring radio signals, part of a project known as SETI, or the Search for Extraterrestrial Intelligence.
"As soon as we find a different, a separate, an independent example of life somewhere else, we're going to know that it's ubiquitous throughout the universe," said astronomer Jill Tarter, director of the SETI Institute in Mountain View.
The Kepler team is meeting for its first science conference this week.
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