Sometimes I complain about the earthly weather, but mostly I like to post about astronomy and space events. Hope you enjoy the articles.
By: Susie77, 2:56 PM GMT on September 28, 2012
From Science at NASA
Curiosity Finds Old Streambed on Mars
Sept. 27, 2012: NASA's Curiosity rover mission has found evidence a stream once ran vigorously across the area on Mars where the rover is driving. There is earlier evidence for the presence of water on Mars, but this evidence -- images of rocks containing ancient streambed gravels -- is the first of its kind.
"From the size of gravels it carried, we can interpret the water was moving about 3 feet per second, with a depth somewhere between ankle and hip deep," said Curiosity science co-investigator William Dietrich of the University of California, Berkeley. "Plenty of papers have been written about channels on Mars with many different hypotheses about the flows in them. This is the first time we're actually seeing water-transported gravel on Mars. This is a transition from speculation about the size of streambed material to direct observation of it."
NASA's Curiosity rover found evidence for an ancient, flowing stream on Mars at a few sites, including the rock outcrop pictured here, which the science team has named "Hottah" after Hottah Lake in Canada’s Northwest Territories. Image credit: NASA/JPL-Caltech/MSSS
The finding site lies between the north rim of Gale Crater and the base of Mount Sharp, a mountain inside the crater. Earlier imaging of the region from Mars orbit allows for additional interpretation of the gravel-bearing conglomerate. The imagery shows an alluvial fan of material washed down from the rim, streaked by many apparent channels, sitting uphill of the new finds.
The rounded shape of some stones in the conglomerate indicates long-distance transport from above the rim, where a channel named Peace Vallis feeds into the alluvial fan. The abundance of channels in the fan between the rim and conglomerate suggests flows continued or repeated over a long time, not just once or for a few years.
The discovery comes from examining two outcrops, called "Hottah" and "Link," with the telephoto capability of Curiosity's mast camera during the first 40 days after landing. Those observations followed up on earlier hints from another outcrop, which was exposed by thruster exhaust as Curiosity, the Mars Science Laboratory Project's rover, touched down.
"Hottah looks like someone jack-hammered up a slab of city sidewalk, but it's really a tilted block of an ancient streambed," said Mars Science Laboratory Project Scientist John Grotzinger of the California Institute of Technology in Pasadena.
The gravels in conglomerates at both outcrops range in size from a grain of sand to a golf ball. Some are angular, but many are rounded.
"The shapes tell you they were transported and the sizes tell you they couldn't be transported by wind. They were transported by water flow," said Curiosity science co-investigator Rebecca Williams of the Planetary Science Institute in Tucson, Ariz.
The science team may use Curiosity to learn the elemental composition of the material, which holds the conglomerate together, revealing more characteristics of the wet environment that formed these deposits. The stones in the conglomerate provide a sampling from above the crater rim, so the team may also examine several of them to learn about broader regional geology.
The slope of Mount Sharp in Gale Crater remains the rover's main destination. Clay and sulfate minerals detected there from orbit can be good preservers of carbon-based organic chemicals that are potential ingredients for life.
"A long-flowing stream can be a habitable environment," said Grotzinger. "It is not our top choice as an environment for preservation of organics, though. We're still going to Mount Sharp, but this is insurance that we have already found our first potentially habitable environment."
Production editor: Dr. Tony Phillips | Credit: Science@NASA
By: Susie77, 4:20 PM GMT on September 24, 2012
( We knew this would happen eventually -- the emanations from Washington DC have reached the very edges of our galaxy. ~~ Sue )
NASA'S CHANDRA SHOWS MILKY WAY IS SURROUNDED BY HALO OF HOT GAS
WASHINGTON -- Astronomers have used NASA's Chandra X-ray Observatory
to find evidence our Milky Way Galaxy is embedded in an enormous halo
of hot gas that extends for hundreds of thousands of light years. The
estimated mass of the halo is comparable to the mass of all the stars
in the galaxy.
If the size and mass of this gas halo is confirmed, it also could be
an explanation for what is known as the "missing baryon" problem for
Baryons are particles, such as protons and neutrons, that make up more
than 99.9 percent of the mass of atoms found in the cosmos.
Measurements of extremely distant gas halos and galaxies indicate the
baryonic matter present when the universe was only a few billion
years old represented about one-sixth the mass and density of the
existing unobservable, or dark, matter. In the current epoch, about
10 billion years later, a census of the baryons present in stars and
gas in our galaxy and nearby galaxies shows at least half the baryons
are unaccounted for.
In a recent study, a team of five astronomers used data from Chandra,
the European Space Agency's XMM-Newton space observatory and Japan's
Suzaku satellite to set limits on the temperature, extent and mass of
the hot gas halo. Chandra observed eight bright X-ray sources located
far beyond the galaxy at distances of hundreds of millions of
light-years. The data revealed X-rays from these distant sources are
absorbed selectively by oxygen ions in the vicinity of the galaxy.
The scientists determined the temperature of the absorbing halo is
between 1 million and 2.5 million kelvins, or a few hundred times
hotter than the surface of the sun.
Other studies have shown that the Milky Way and other galaxies are
embedded in warm gas with temperatures between 100,000 and 1 million
kelvins. Studies have indicated the presence of a hotter gas with a
temperature greater than 1 million kelvins. This new research
provides evidence the hot gas halo enveloping the Milky Way is much
more massive than the warm gas halo.
"We know the gas is around the galaxy, and we know how hot it is,"
said Anjali Gupta, lead author of The Astrophysical Journal paper
describing the research. "The big question is, how large is the halo,
and how massive is it?"
To begin to answer this question, the authors supplemented Chandra
data on the amount of absorption produced by the oxygen ions with
XMM-Newton and Suzaku data on the X-rays emitted by the gas halo.
They concluded that the mass of the gas is equivalent to the mass in
more than 10 billion suns, perhaps as large as 60 billion suns.
"Our work shows that, for reasonable values of parameters and with
reasonable assumptions, the Chandra observations imply a huge
reservoir of hot gas around the Milky Way," said co-author Smita
Mathur of Ohio State University in Columbus. "It may extend for a few
hundred thousand light-years around the Milky Way or it may extend
farther into the surrounding local group of galaxies. Either way, its
mass appears to be very large."
The estimated mass depends on factors such as the amount of oxygen
relative to hydrogen, which is the dominant element in the gas.
Nevertheless, the estimation represents an important step in solving
the case of the missing baryons, a mystery that has puzzled
astronomers for more than a decade.
Although there are uncertainties, the work by Gupta and colleagues
provides the best evidence yet that the galaxy's missing baryons have
been hiding in a halo of million-kelvin gas that envelopes the
galaxy. The estimated density of this halo is so low that similar
halos around other galaxies would have escaped detection.
The paper describing these results was published in the Sept. 1 issue
of The Astrophysical Journal. Other co-authors were Yair Krongold of
Universidad Nacional Autonoma de Mexico in Mexico City; Fabrizio
Nicastro of Harvard-Smithsonian Center for Astrophysics in Cambridge,
Mass.; and Massimiliano Galeazzi of University of Miami in Coral
NASA's Marshall Space Flight Center in Huntsville, Ala., manages the
Chandra program for NASA's Science Mission Directorate in Washington.
The Smithsonian Astrophysical Observatory controls Chandra's science
and flight operations from Cambridge.
For Chandra images, multimedia and related materials, visit:
For an additional interactive image, podcast and video on the finding,
By: Susie77, 12:00 PM GMT on September 13, 2012
From Science at NASA
Sept. 12, 2012: News flash: The Milky Way galaxy just got a little weirder.
Back in 2011 astronomers were amazed when NASA's Kepler spacecraft discovered a planet orbiting a double star system. Such a world, they realized, would have double sunsets and sunrises just like the fictional planet Tatooine in the movie Star Wars. Yet this planet was real.
Now Kepler has discovered a whole system of planets orbiting a double star.
The star system, known as Kepler-47, is located 4,900 light-years from Earth in the constellation Cygnus. Two stars orbit one another at the center of the system: One is similar to the sun in size, but only 84 percent as bright. The second star is smaller, only one-third the size of the sun and less than 1 percent as bright. Kepler found two planets orbiting this mismatched pair.
"The presence of a full-fledged planetary system orbiting Kepler-47 is an amazing discovery," says Greg Laughlin, professor of Astrophysics and Planetary Science at the University of California in Santa Cruz. “This is going to change the way we think about the formation of planets.”
The inner planet, Kepler-47b, closely circles the pair of stars, completing each orbit in less than 50 days. Astronomers think it is a sweltering world, where the destruction of methane in its super-heated atmosphere might lead to a thick global haze. Kepler-47b is about three times the size of Earth.
The outer planet, Kepler-47c, orbits every 303 days. This puts it in the system's habitable zone, a band of orbits that are “just right” for liquid water to exist on the surface of a planet. But does this planet even have a surface? Possibly not. The astronomers think it is a gas giant slightly larger than Neptune.
The discovery of planets orbiting double stars means that planetary systems are even weirder and more abundant than previously thought.
This diagram compares our own solar system to Kepler-47, a double-star system containing two planets, one orbiting in the so-called "habitable zone." Credit: NASA/JPL-Caltech/T. Pyle
"Many stars are part of multiple-star systems where two or more stars orbit one another. The question always has been -- do they have planets and planetary systems?" says William Borucki, Kepler mission principal investigator at NASA's Ames Research Center. "This Kepler discovery proves that they do."
Our own sun is a single, isolated star, with a relatively simple gravitational field that rules the motions of the planets orbiting it.
But, as Borucki points out, not all stars are single. Astronomers estimate that more than half of the stars in the galaxy have companions. There are double, triple and even quadruple star systems. Any planets in such systems would have to navigate a complex gravitational field, tugged in multiple directions by multiple stars. In fact, for many years, astronomers doubted that planets could even form in such an environment.
Kepler-47 erases those doubts—and poses a conundrum: "These planets are very difficult to form using the currently accepted paradigm,” says Laughlin. “I believe that theorists, myself included, will be going back to the drawing board to try to improve our understanding of how planets are assembled in the dusty gaseous disks that surround many young stars.”
The Kepler spacecraft is on a mission to find Earth-like planets that might support life. Says Borucki: "In our search for habitable worlds, we have just found more opportunities for life to exist."
Author: Dr. Tony Phillips| Production editor: Dr. Tony Phillips | Credit: Science@NASA