Large quantities of pollen and algae in sediment cores were taken around
Antarctica. Fossils of plant life in Antarctica are difficult to come by because
the movement of the massive ice sheets covering the landmass grinds and scrapes
away the evidence
A new university-led study with NASA participation finds
ancient Antarctica was much warmer and wetter than previously
suspected. The climate was suitable to support substantial vegetation
-- including stunted trees -- along the edges of the frozen
continent.
The team of scientists involved in the study, published online June 17
in Nature Geoscience, was led by Sarah J. Feakins of the University
of Southern California in Los Angeles, and included researchers from
NASA's Jet Propulsion Laboratory in Pasadena, Calif., and Louisiana
State University in Baton Rouge.
By examining plant leaf wax remnants in sediment core samples taken
from beneath the Ross Ice Shelf, the research team found summer
temperatures along the Antarctic coast 15 to 20 million years ago
were 20 degrees Fahrenheit (11 degrees Celsius) warmer than today,
with temperatures reaching as high as 45 degrees Fahrenheit (7
degrees Celsius). Precipitation levels also were found to be several
times higher than today.
"The ultimate goal of the study was to better understand what the
future of climate change may look like," said Feakins, an assistant
professor of Earth sciences at the USC Dornsife College of Letters,
Arts and Sciences. "Just as history has a lot to teach us about the
future, so does past climate. This record shows us how much warmer
and wetter it can get around the Antarctic ice sheet as the climate
system heats up. This is some of the first evidence of just how much
warmer it was."
Scientists began to suspect that high-latitude temperatures during the
middle Miocene epoch were warmer than previously believed when
co-author Sophie Warny, assistant professor at LSU, discovered large
quantities of pollen and algae in sediment cores taken around
Antarctica. Fossils of plant life in Antarctica are difficult to comel
by because the movement of the massive ice sheets covering the
landmass grinds and scrapes away the evidence.
"Marine sediment cores are ideal to look for clues of past vegetation,
as the fossils deposited are protected from ice sheet advances, but
these are technically very difficult to acquire in the Antarctic and
require international collaboration," said Warny.
Tipped off by the tiny pollen samples, Feakins opted to look at the
remnants of leaf wax taken from sediment cores for clues. Leaf wax
acts as a record of climate change by documenting the hydrogen
isotope ratios of the water the plant took up while it was alive.
"Ice cores can only go back about one million years," Feakins said.
"Sediment cores allow us to go into 'deep time.'"
Based upon a model originally developed to analyze hydrogen isotope
ratios in atmospheric water vapor data from NASA's Aura spacecraft,
co-author and JPL scientist Jung-Eun Lee created experiments to find
out just how much warmer and wetter climate may have been.
"When the planet heats up, the biggest changes are seen toward the
poles," Lee said. "The southward movement of rain bands associated
with a warmer climate in the high-latitude southern hemisphere made
the margins of Antarctica less like a polar desert, and more like
present-day Iceland."
The peak of this Antarctic greening occurred during the middle Miocene
period, between 16.4 and 15.7 million years ago. This was well after
the age of the dinosaurs, which became extinct 64 million years ago.
During the Miocene epoch, mostly modern-looking animals roamed Earth,
such as three-toed horses, deer, camel and various species of apes.
Modern humans did not appear until 200,000 years ago.
Warm conditions during the middle Miocene are thought to be associated
with carbon dioxide levels of around 400 to 600 parts per million
(ppm). In 2012, carbon dioxide levels have climbed to 393 ppm, the
highest they've been in the past several million years. At the
current rate of increase, atmospheric carbon dioxide levels are on
track to reach middle Miocene levels by the end of this century.
High carbon dioxide levels during the middle Miocene epoch have been
documented in other studies through multiple lines of evidence,
including the number of microscopic pores on the surface of plant
leaves and geochemical evidence from soils and marine organisms.
While none of these 'proxies' is as reliable as the bubbles of gas
trapped in ice cores, they are the best evidence available this far
back in time. While scientists do not yet know precisely why carbon
dioxide was at these levels during the middle Miocene, high carbon
dioxide, together with the global warmth documented from many parts
of the world and now also from the Antarctic region, appear to
coincide during this period in Earth's history.
Tuesday, June 19, 2012
Sunday, June 17, 2012
The story of outer space: Small planets are made specially, they do not need stars with heavy metal content
Planets are created disks of gas and dust around new stars. Planets like Earth are composed almost entirely of elements such as iron, oxygen, silicon and magnesium.
The formation of small worlds like Earth previously was
thought to occur mostly around stars rich in heavy elements such as
iron and silicon. However, new ground-based observations, combined
with data collected by NASA's Kepler space telescope, shows small
planets form around stars with a wide range of heavy element content
and suggests they may be widespread in our galaxy.
A research team led by Lars A. Buchhave, an astrophysicist at the
Niels Bohr Institute and the Centre for Star and Planet Formation at
the University of Copenhagen, studied the elemental composition of
more than 150 stars harboring 226 planet candidates smaller than
Neptune.
"I wanted to investigate whether small planets needed a special
environment in order to form, like the giant gas planets, which we
know preferentially develop in environments with a high content of
heavy elements," said Buchhave. "This study shows that small planets
do not discriminate and form around stars with a wide range of heavy
metal content, including stars with only 25 percent of the sun's
metallicity."
Astronomers refer to all chemical elements heavier than hydrogen and
helium as metals. They define metallicity is the metal content of
heavier elements in a star. Stars with a higher fraction of heavy
elements than the sun are considered metal-rich. Stars with a lower
fraction of heavy elements are considered metal-poor.
Planets are created disks of gas and dust around new stars. Planets
like Earth are composed almost entirely of elements such as iron,
oxygen, silicon and magnesium.
The metallicity of a star mirrors the metal content of the
planet-forming disk. Astronomers have hypothesized that large
quantities of heavy elements in the disk would lead to more efficient
planet formation. It has long been noted that giant planets with
short orbital periods tend to be associated with metal-rich stars.
Unlike gas giants, the occurrence of smaller planets is not strongly
dependent on the heavy element content of their host stars. Planets
up to four times the size of Earth can form around stars with a wide
range of heavy element content, including stars with a lower
metallicity than the sun. The findings are described in a new study
published in the journal Nature.
"Kepler has identified thousands of planet candidates, making it
possible to study big-picture questions like the one posed by Lars.
Does nature require special environments to form Earth-size planets?"
said Natalie Batalha, Kepler mission scientist at NASA's Ames
Research Center at Moffett Field, Calif. "The data suggest that small
planets may form around stars with a wide range of metallicities --
that nature is opportunistic and prolific, finding pathways we might
otherwise have thought difficult."
The ground-based spectroscopic observations for this study were made
at the Nordic Optical Telescope on La Palma in the Canary Islands;
Fred Lawrence Whipple Observatory on Mt. Hopkins in Ariz.; McDonald
Observatory at the University of Texas at Austin; and W.M. Keck
Observatory atop Mauna Kea in Hawaii.
Launched in March 2009, Kepler searches for planets by continuously
monitoring more than 150,000 stars, looking for telltale dips in
their brightness caused by passing, or transiting, planets. At least
three transits are required to verify a signal as a planet. Follow-up
observations from ground-based telescopes are also needed to confirm
a candidate as a planet.
Ames manages Kepler's ground system development, mission operations
and science data analysis. NASA's Jet Propulsion Laboratory in
Pasadena, Calif., managed the Kepler mission development.
Ball Aerospace & Technologies Corp. in Boulder, Colo., developed the
Kepler flight system and supports mission operations with the
Laboratory for Atmospheric and Space Physics at the University of
Colorado in Boulder.
The Space Telescope Science Institute in Baltimore archives hosts and
distributes Kepler science data. Kepler is NASA's 10th Discovery
Mission and is funded by NASA's Science Mission Directorate at the
agency's headquarters in Washington.
The formation of small worlds like Earth previously was
thought to occur mostly around stars rich in heavy elements such as
iron and silicon. However, new ground-based observations, combined
with data collected by NASA's Kepler space telescope, shows small
planets form around stars with a wide range of heavy element content
and suggests they may be widespread in our galaxy.
A research team led by Lars A. Buchhave, an astrophysicist at the
Niels Bohr Institute and the Centre for Star and Planet Formation at
the University of Copenhagen, studied the elemental composition of
more than 150 stars harboring 226 planet candidates smaller than
Neptune.
"I wanted to investigate whether small planets needed a special
environment in order to form, like the giant gas planets, which we
know preferentially develop in environments with a high content of
heavy elements," said Buchhave. "This study shows that small planets
do not discriminate and form around stars with a wide range of heavy
metal content, including stars with only 25 percent of the sun's
metallicity."
Astronomers refer to all chemical elements heavier than hydrogen and
helium as metals. They define metallicity is the metal content of
heavier elements in a star. Stars with a higher fraction of heavy
elements than the sun are considered metal-rich. Stars with a lower
fraction of heavy elements are considered metal-poor.
Planets are created disks of gas and dust around new stars. Planets
like Earth are composed almost entirely of elements such as iron,
oxygen, silicon and magnesium.
The metallicity of a star mirrors the metal content of the
planet-forming disk. Astronomers have hypothesized that large
quantities of heavy elements in the disk would lead to more efficient
planet formation. It has long been noted that giant planets with
short orbital periods tend to be associated with metal-rich stars.
Unlike gas giants, the occurrence of smaller planets is not strongly
dependent on the heavy element content of their host stars. Planets
up to four times the size of Earth can form around stars with a wide
range of heavy element content, including stars with a lower
metallicity than the sun. The findings are described in a new study
published in the journal Nature.
"Kepler has identified thousands of planet candidates, making it
possible to study big-picture questions like the one posed by Lars.
Does nature require special environments to form Earth-size planets?"
said Natalie Batalha, Kepler mission scientist at NASA's Ames
Research Center at Moffett Field, Calif. "The data suggest that small
planets may form around stars with a wide range of metallicities --
that nature is opportunistic and prolific, finding pathways we might
otherwise have thought difficult."
The ground-based spectroscopic observations for this study were made
at the Nordic Optical Telescope on La Palma in the Canary Islands;
Fred Lawrence Whipple Observatory on Mt. Hopkins in Ariz.; McDonald
Observatory at the University of Texas at Austin; and W.M. Keck
Observatory atop Mauna Kea in Hawaii.
Launched in March 2009, Kepler searches for planets by continuously
monitoring more than 150,000 stars, looking for telltale dips in
their brightness caused by passing, or transiting, planets. At least
three transits are required to verify a signal as a planet. Follow-up
observations from ground-based telescopes are also needed to confirm
a candidate as a planet.
Ames manages Kepler's ground system development, mission operations
and science data analysis. NASA's Jet Propulsion Laboratory in
Pasadena, Calif., managed the Kepler mission development.
Ball Aerospace & Technologies Corp. in Boulder, Colo., developed the
Kepler flight system and supports mission operations with the
Laboratory for Atmospheric and Space Physics at the University of
Colorado in Boulder.
The Space Telescope Science Institute in Baltimore archives hosts and
distributes Kepler science data. Kepler is NASA's 10th Discovery
Mission and is funded by NASA's Science Mission Directorate at the
agency's headquarters in Washington.
When stars die a spectacular death: Why supernova does not explode? Nasa searches for the answer
The distribution of the material in a supernova remnant tells you a lot about the original explosion
Somewhere in the Milky Way, a massive old star is about to die a spectacular death. As its nuclear fuel runs out, the star begins to collapse under its own tremendous weight. Crushing pressure triggers new nuclear reactions, setting the stage for a terrifying blast. And then... nothing happens.
At least that's what supercomputers have been telling astrophysicists for decades. Many of the best computer models of supernovas fail to produce an explosion. At the end of the simulation, gravity wins the day and the star simply collapses.
Clearly, physicists are missing something.
"We don't fully understand how supernovas of massive stars work yet," says Fiona Harrison, an astrophysicist at the California Institute of Technology.
To figure out what’s going on, Harrison and colleagues would like to examine the inside of a real supernova while it's exploding. That's not possible, so they're doing the next best thing.
Using a telescope named "NuSTAR" --short for Nuclear Spectroscopic Telescope Array -- they'll be scanning the debris from supernovas as soon as possible after the blast.
Launched over the Pacific Ocean on June 13, 2012, by a Pegasus XL rocket, NuSTAR is the first space telescope that can focus very high-energy X-rays, producing images roughly 100 times sharper than those possible with previous high-energy X-ray telescopes.
When NuSTAR finishes its check-out and becomes fully operational, scientists will use it to scan supernovas for clues etched into the pattern of elements spread throughout the explosion's debris.
"The distribution of the material in a supernova remnant tells you a lot about the original explosion,” says Harrison.
An element of particular interest is titanium-44. Creating this isotope of titanium through nuclear fusion requires a certain combination of energy, pressure, and raw materials. Inside the collapsing star, that combination occurs at a depth that's very special. Everything below that depth succumbs to gravity and collapses inward to form a black hole. Everything above that depth will be blown outward in the explosion. Titanium-44 is created right at the cusp.
So the pattern of how titanium-44 is spread throughout a supernova remnant can reveal a lot about what happened at that crucial threshold during the explosion. And with that information, scientists might be able to figure out what's wrong with their computer simulations.
Some scientists believe the computer models are too symmetrical. Until recently, even with powerful supercomputers, scientists have only been able to simulate a one-dimensional sliver of the star. Scientists just assume that the rest of the star behaves similarly, making the simulated implosion the same in all radial directions.
But what if that assumption is wrong?
"Asymmetries could be the key," Harrison says. In an asymmetrical collapse, outward forces could break through in some places even if the crush of gravity is overpowering in others. Indeed, more recent, two-dimensional simulations suggest that asymmetries could help solve the mystery of the "non-exploding supernova."
If NuSTAR finds that titanium-44 is spread unevenly, it would be evidence that the explosions themselves were also asymmetrical, Harrison explains.
To detect titanium-44, NuSTAR needs to be able to focus very high energy X-rays. Titanium-44 is radioactive, and when it decays it releases photons with an energy of 68 thousand electron volts. Existing X-ray space telescopes, such as NASA's Chandra X-Ray Observatory, can focus X-rays only up to about 15 thousand electron volts.
Normal lenses can't focus X-rays at all. Glass bends X-rays only a miniscule amount—not enough to form an image.
X-ray telescopes use an entirely different kind of "lens" consisting of many concentric shells. They look a bit like the layers of a cylindrical onion.
Incoming X-rays pass between these layers, which guide the X-rays to the focal surface. It's not a lens, strictly speaking, because the X-rays reflect off the surfaces of the shells instead of passing through them, but the end result is the same.
The NuSTAR team has spent years perfecting delicate manufacturing techniques required to make high-precision X-ray optics for NuSTAR that work at energies as high as 79 thousand electron volts.
Their efforts could end up answering the question, "Why won't the supernova explode?
Wednesday, June 13, 2012
Challenging tasks of aquanauts: Nasa team studies the secrets of the Deep
An international crew of aquanauts is settling into its
home on the ocean floor, where the team tests concepts for a potential
asteroid mission. The expedition is the 16th
excursion of the NASA Extreme Environment Mission Operations (NEEMO).
The crew of four began its mission in the National Oceanic and
Atmospheric Administration's Aquarius Reef Base undersea research
habitat off the coast of Key Largo.
NEEMO sends groups of astronauts, engineers and scientists to live in
the Aquarius lab, 63 feet below the surface of the Atlantic Ocean.
The laboratory is located in the Florida Keys National Marine
Sanctuary. For NASA, Aquarius provides a convincing simulation to
space exploration, and NEEMO crew members experience some of the same
tasks and challenges under water that they would in space.
The NEEMO 16 mission will focus on three areas related to asteroid
missions. The crew of aquanauts will investigate communication
delays, restraint and translation techniques, and optimum crew size.
The isolation and microgravity environment of the ocean floor allows
the NEEMO 16 crew to study and test concepts for how future
exploration of asteroids might be conducted. NASA's Orion spacecraft
and the Space Launch System rocket, which currently are in
development, will allow people to begin exploring beyond the
boundaries of Earth's orbit. The first human mission to an asteroid
is planned for 2025.
NEEMO 16 Commander Dottie Metcalf-Lindenburger of NASA will be joined
by European Space Agency astronaut Timothy Peake; Japan Aerospace
Exploration Agency astronaut Kimiya Yui; and Steven W. Squyres,
Goldwin Smith professor of astronomy at Cornell University and
chairman of the NASA Advisory Council. Squyres also was a member of
NEEMO 15.
The NEEMO crew members will be chronicling their mission using several
social media outlets, blogs and live video streams from the crews'
helmets, the air lock and outside the habitat.
home on the ocean floor, where the team tests concepts for a potential
asteroid mission. The expedition is the 16th
excursion of the NASA Extreme Environment Mission Operations (NEEMO).
The crew of four began its mission in the National Oceanic and
Atmospheric Administration's Aquarius Reef Base undersea research
habitat off the coast of Key Largo.
NEEMO sends groups of astronauts, engineers and scientists to live in
the Aquarius lab, 63 feet below the surface of the Atlantic Ocean.
The laboratory is located in the Florida Keys National Marine
Sanctuary. For NASA, Aquarius provides a convincing simulation to
space exploration, and NEEMO crew members experience some of the same
tasks and challenges under water that they would in space.
The NEEMO 16 mission will focus on three areas related to asteroid
missions. The crew of aquanauts will investigate communication
delays, restraint and translation techniques, and optimum crew size.
The isolation and microgravity environment of the ocean floor allows
the NEEMO 16 crew to study and test concepts for how future
exploration of asteroids might be conducted. NASA's Orion spacecraft
and the Space Launch System rocket, which currently are in
development, will allow people to begin exploring beyond the
boundaries of Earth's orbit. The first human mission to an asteroid
is planned for 2025.
NEEMO 16 Commander Dottie Metcalf-Lindenburger of NASA will be joined
by European Space Agency astronaut Timothy Peake; Japan Aerospace
Exploration Agency astronaut Kimiya Yui; and Steven W. Squyres,
Goldwin Smith professor of astronomy at Cornell University and
chairman of the NASA Advisory Council. Squyres also was a member of
NEEMO 15.
The NEEMO crew members will be chronicling their mission using several
social media outlets, blogs and live video streams from the crews'
helmets, the air lock and outside the habitat.
The mystery of outer space: What makes black holes to grow in the centre of galaxies
New evidence from NASA's Chandra X-ray Observatory
challenges prevailing ideas about how black holes grow in the centers
of galaxies. Astronomers long have thought that a supermassive black
hole and the bulge of stars at the center of its host galaxy grow at
the same rate -- the bigger the bulge, the bigger the black hole.
However, a new study of Chandra data has revealed two nearby galaxies
with supermassive black holes that are growing faster than the
galaxies themselves.
The mass of a giant black hole at the center of a galaxy typically is
a tiny fraction -- about 0.2 percent -- of the mass contained in the
bulge, or region of densely packed stars, surrounding it. The targets
of the latest Chandra study, galaxies NGC 4342 and NGC 4291, have
black holes 10 times to 35 times more massive than they should be
compared to their bulges. The new observations with Chandra show the
halos, or massive envelopes of dark matter in which these galaxies
reside, also are overweight.
This study suggests the two supermassive black holes and their
evolution are tied to their dark matter halos and did not grow in
tandem with the galactic bulges. In this view, the black holes and
dark matter halos are not overweight, but the total mass in the
galaxies is too low.
"This gives us more evidence of a link between two of the most
mysterious and darkest phenomena in astrophysics -- black holes and
dark matter -- in these galaxies," said Akos Bogdan of the
Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge,
Mass., who led the new study.
NGC 4342 and NGC 4291 are close to Earth in cosmic terms, at distances
of 75 million and 85 million light years. Astronomers had known from
previous observations that these galaxies host black holes with
relatively large masses, but are not certain what is responsible for
the disparity. Based on the new Chandra observations, however, they
are able to rule out a phenomenon known as tidal stripping.
Tidal stripping occurs when some of a galaxy's stars are stripped away
by gravity during a close encounter with another galaxy. If such
tidal stripping had taken place, the halos mostly would have been
missing. Because dark matter extends farther away from the galaxies,
it is more loosely tied to them than the stars and more likely to be
pulled away.
To rule out tidal stripping, astronomers used Chandra to look for
evidence of hot, X-ray-emitting gas around the two galaxies. Because
the pressure of hot gas -- estimated from X-ray images -- balances
the gravitational pull of all the matter in the galaxy, the new
Chandra data can provide information about the dark matter halos. The
hot gas was found to be distributed widely around NGC 4342 and NGC
4291, implying that each galaxy has an unusually massive dark matter
halo and that tidal stripping is unlikely.
"This is the clearest evidence we have, in the nearby universe, for
black holes growing faster than their host galaxy," said co-author
Bill Forman, also of CfA. "It's not that the galaxies have been
compromised by close encounters, but instead they had some sort of
arrested development."
How can the mass of a black hole grow faster than the stellar mass of
its host galaxy? The study's authors suggest a large concentration of
gas spinning slowly in the galactic center is what the black hole
consumes very early in its history. It grows quickly, and as it
grows, the amount of gas it can accrete, or swallow, increases along
with the energy output from the accretion. After the black hole
reaches a critical mass, outbursts powered by the continued
consumption of gas prevent cooling and limit the production of new
stars.
"It's possible that the supermassive black hole reached a hefty size
before there were many stars at all in the galaxy," said Bogdan.
"That is a significant change in our way of thinking about how
galaxies and black holes evolve together."
The results were presented June 11 at the 220th meeting of the
American Astronomical Society in Anchorage, Alaska. The study also
has been accepted for publication in The Astrophysical Journal.
NASA's Marshall Space Flight Center in Huntsville, Ala., manages the
Chandra program for the agency's NASA's Science Mission Directorate
in Washington. The Smithsonian Astrophysical Observatory in
Cambridge, Mass., controls Chandra's science and flight operations.
challenges prevailing ideas about how black holes grow in the centers
of galaxies. Astronomers long have thought that a supermassive black
hole and the bulge of stars at the center of its host galaxy grow at
the same rate -- the bigger the bulge, the bigger the black hole.
However, a new study of Chandra data has revealed two nearby galaxies
with supermassive black holes that are growing faster than the
galaxies themselves.
The mass of a giant black hole at the center of a galaxy typically is
a tiny fraction -- about 0.2 percent -- of the mass contained in the
bulge, or region of densely packed stars, surrounding it. The targets
of the latest Chandra study, galaxies NGC 4342 and NGC 4291, have
black holes 10 times to 35 times more massive than they should be
compared to their bulges. The new observations with Chandra show the
halos, or massive envelopes of dark matter in which these galaxies
reside, also are overweight.
This study suggests the two supermassive black holes and their
evolution are tied to their dark matter halos and did not grow in
tandem with the galactic bulges. In this view, the black holes and
dark matter halos are not overweight, but the total mass in the
galaxies is too low.
"This gives us more evidence of a link between two of the most
mysterious and darkest phenomena in astrophysics -- black holes and
dark matter -- in these galaxies," said Akos Bogdan of the
Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge,
Mass., who led the new study.
NGC 4342 and NGC 4291 are close to Earth in cosmic terms, at distances
of 75 million and 85 million light years. Astronomers had known from
previous observations that these galaxies host black holes with
relatively large masses, but are not certain what is responsible for
the disparity. Based on the new Chandra observations, however, they
are able to rule out a phenomenon known as tidal stripping.
Tidal stripping occurs when some of a galaxy's stars are stripped away
by gravity during a close encounter with another galaxy. If such
tidal stripping had taken place, the halos mostly would have been
missing. Because dark matter extends farther away from the galaxies,
it is more loosely tied to them than the stars and more likely to be
pulled away.
To rule out tidal stripping, astronomers used Chandra to look for
evidence of hot, X-ray-emitting gas around the two galaxies. Because
the pressure of hot gas -- estimated from X-ray images -- balances
the gravitational pull of all the matter in the galaxy, the new
Chandra data can provide information about the dark matter halos. The
hot gas was found to be distributed widely around NGC 4342 and NGC
4291, implying that each galaxy has an unusually massive dark matter
halo and that tidal stripping is unlikely.
"This is the clearest evidence we have, in the nearby universe, for
black holes growing faster than their host galaxy," said co-author
Bill Forman, also of CfA. "It's not that the galaxies have been
compromised by close encounters, but instead they had some sort of
arrested development."
How can the mass of a black hole grow faster than the stellar mass of
its host galaxy? The study's authors suggest a large concentration of
gas spinning slowly in the galactic center is what the black hole
consumes very early in its history. It grows quickly, and as it
grows, the amount of gas it can accrete, or swallow, increases along
with the energy output from the accretion. After the black hole
reaches a critical mass, outbursts powered by the continued
consumption of gas prevent cooling and limit the production of new
stars.
"It's possible that the supermassive black hole reached a hefty size
before there were many stars at all in the galaxy," said Bogdan.
"That is a significant change in our way of thinking about how
galaxies and black holes evolve together."
The results were presented June 11 at the 220th meeting of the
American Astronomical Society in Anchorage, Alaska. The study also
has been accepted for publication in The Astrophysical Journal.
NASA's Marshall Space Flight Center in Huntsville, Ala., manages the
Chandra program for the agency's NASA's Science Mission Directorate
in Washington. The Smithsonian Astrophysical Observatory in
Cambridge, Mass., controls Chandra's science and flight operations.
Mission Mars: Nasa's Mars rover team plan to land in the vicinity of prime science site on the Red Planet
NASA has narrowed the target for its most advanced Mars rover, Curiosity, which will land on the Red Planet in August. The car-sized rover will touch down closer to its ultimate destination for science operations, but also closer to the foot of a mountain slope that poses a landing hazard.
"We're trimming the distance we'll have to drive after landing by almost half," said Pete Theisinger, Mars Science Laboratory project manager at NASA's Jet Propulsion Laboratory. "That could get us to the mountain months earlier."
It was possible to adjust landing plans because of increased confidence in precision landing technology aboard the Mars Science Laboratory spacecraft, which is carrying the Curiosity rover. That spacecraft can aim closer without hitting Mount Sharp at the center of Gale crater. Rock layers located in the mountain are the prime location for research with the rover.
Curiosity is scheduled to land at approximately 10:31 p.m. PDT Aug. 5 (1:31 a.m. EDT, Aug. 6). Following checkout operations, Curiosity will begin a two-year study of whether the landing vicinity ever offered an environment favorable for microbial life.
Theisinger and other mission leaders described the target adjustment during an update to reporters on Monday, June 11, about preparations for landing and for operating Curiosity on Mars.
The landing target ellipse had been approximately 12 miles wide and 16 miles long (20 kilometers by 25 kilometers). Continuing analysis of the new landing system's capabilities has allowed mission planners to shrink the area to approximately 4 miles wide and 12 miles long (7 kilometers by 20 kilometers), assuming winds and other atmospheric conditions are as predicted.
Even with the smaller ellipse, Curiosity will be able to touch down at a safe distance from steep slopes at the edge of Mount Sharp.
"We have been preparing for years for a successful landing by Curiosity, and all signs are good," said Dave Lavery, Mars Science Laboratory program executive at NASA. "However, landing on Mars always carries risks, so success is not guaranteed. Once on the ground we'll proceed carefully. We have plenty of time since Curiosity is not as life-limited as the approximate 90-day missions like NASA’s Mars Exploration Rovers and the Phoenix lander.”
Curiosity will be in good company as it nears landing. Two NASA Mars orbiters, along with a European Space Agency orbiter, will be in position to listen to radio transmissions as Mars Science Laboratory descends through Mars' atmosphere.
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