MSL launch delayed to Saturday, Nov. 26

The launch of a United Launch Alliance Atlas V carrying NASA's Mars Science Laboratory (MSL) has been delayed one day to allow time for the team to remove and replace a flight termination system battery. The launch is rescheduled for Saturday, Nov. 26 from Space Launch Complex-41 at Cape Canaveral Air Force Station, Florida. The one hour and 43 minute launch window opens at 10:02 a.m. EST.

The Monday, Nov. 21 schedule of prelaunch tours and briefings will remain the same. Rollout of the Atlas V to the launch pad moves to Friday, Nov. 25. The rest of the week's briefings and events are being reevaluated and a new prelaunch schedule will be issued on Monday.

 

NASA's Hubble Observes Young Dwarf Galaxies Bursting With Stars

Using its near-infrared vision to peer 9 billion years back in time, NASA's Hubble Space Telescope has uncovered an extraordinary population of young dwarf galaxies brimming with star formation. While dwarf galaxies are the most common type of galaxy in the universe, the rapid star-birth observed in these newly found examples may force astronomers to reassess their understanding of the ways in which galaxies form .

The galaxies are a hundred times less massive, on average, than the Milky Way, yet churn out stars at such a furious pace that their stellar content would double in just 10 million years. By comparison, the Milky Way would take a thousand times longer to double its star population.


The universe is estimated to be 13.7 billion years old, and these newly discovered galaxies are extreme even for the young universe -- when most galaxies were forming stars at higher rates than they are today. Astronomers using Hubble's instruments could spot the galaxies because the radiation from young, hot stars has caused the oxygen in the gas surrounding them to light up like a bright neon sign.
"The galaxies have been there all along, but up until recently astronomers have been able only to survey tiny patches of sky at the sensitivities necessary to detect them," said Arjen van der Wel of the Max Planck Institute for Astronomy in Heidelberg, Germany, lead author of a paper on the results being published online on Nov. 14 in The Astrophysical Journal. "We weren't looking specifically for these galaxies, but they stood out because of their unusual colors."

This image reveals 18 tiny galaxies uncovered by NASA's Hubble Space Telescope. The puny galaxies, shown in the postage stamp-sized images, existed 9 billion years ago and are brimming with star birth. Hubble's Wide Field Camera 3 and Advanced Camera for Surveys spied the galaxies in a field called the Great Observatories Origins Deep Survey (GOODS). The galaxies are among 69 dwarf galaxies found in the GOODS (marked by green circles in the large image) and other fields. Images of the individual galaxies were taken November 2010 to January 2011. The large image was taken between Sept. 2002 and Dec. 2004, and between Sept. 2009 and Oct. 2009.

The observations were part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS), an ambitious three-year study to analyze the most distant galaxies in the universe. CANDELS is the first census of dwarf galaxies at such an early epoch. 

"In addition to the images, Hubble has captured spectra that show us the oxygen in a handful of galaxies and confirmed their extreme star-forming nature," said co-author Amber Straughn at NASA's Goddard Space Flight Center in Greenbelt, Md. "Spectra are like fingerprints. They tell us the galaxies' chemical composition."

The resulting observations are somewhat at odds with recent detailed studies of the dwarf galaxies that are orbiting as satellites of the Milky Way.

The observations were part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS), an ambitious three-year study to analyze the most distant galaxies in the universe. CANDELS is the first census of dwarf galaxies at such an early epoch.

"In addition to the images, Hubble has captured spectra that show us the oxygen in a handful of galaxies and confirmed their extreme star-forming nature," said co-author Amber Straughn at NASA's Goddard Space Flight Center in Greenbelt, Md. "Spectra are like fingerprints. They tell us the galaxies' chemical composition."

The resulting observations are somewhat at odds with recent detailed studies of the dwarf galaxies that are orbiting as satellites of the Milky Way.

"Those studies suggest that star formation was a relatively slow process, stretching out over billions of years," explained Harry Ferguson of the Space Telescope Science Institute (STScI) in Baltimore, Md., co-leader of the CANDELS survey. "The CANDELS finding that there were galaxies of roughly the same size forming stars at very rapid rates at early times is forcing us to re-examine what we thought we knew about dwarf galaxy evolution."

The CANDELS team uncovered the 69 young dwarf galaxies in near-infrared images taken with Hubble's Wide Field Camera 3 and Advanced Camera for Surveys.

The observations suggest that the newly discovered galaxies were very common 9 billion years ago. However, it is a mystery why the newly found dwarf galaxies were making batches of stars at such a high rate. Computer simulations show star formation in small galaxies may be episodic. Gas cools and collapses to form stars. The stars then reheat the gas and blow it away, as in supernova explosions. After some time, the gas cools and collapses again, producing a new burst of star formation, continuing the cycle.

"While these theoretical predictions may provide hints to explain the star formation in these newly discovered galaxies, the observed bursts are much more intense than what the simulations can reproduce," van der Wel said.

The James Webb Space Telescope, an infrared observatory scheduled to launch later this decade, will be able to probe these faint galaxies at an even earlier era to see the glow of their stars, reveal their chemical composition, and offer better details on their formation.

Source : NASA

NASA Extends MESSENGER Mission

NASA has announced that it will extend the MESSENGER mission for an additional year of orbital operations at Mercury beyond the planned end of the primary mission on March 17, 2012. The MESSENGER probe became the first spacecraft to orbit the innermost planet on March 18, 2011.

"We are still ironing out the funding details, but we are pleased to be able to support the continued exploration of Mercury," said NASA MESSENGER Program Scientist Ed Grayzeck, who made the announcement on November 9 at the 24th meeting of the MESSENGER Science Team in Annapolis, Md.

The spacecraft's unprecedented orbital science campaign is providing the first global close-up of Mercury and has revolutionized scientific perceptions of that planet. The extended mission will allow scientists to learn even more about the planet closest to the Sun, says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington.

"During the extended mission we will spend more time close to the planet than during the primary mission, we'll have a broader range of scientific objectives, and we'll be able to make many more targeted observations with our imaging system and other instruments," says Solomon. "MESSENGER will also be able to view the innermost planet as solar activity continues to increase toward the next maximum in the solar cycle. Mercury's responses to the changes in its environment over that period promise to yield new surprises."

The extended mission has been designed to answer six scientific questions, each of which has arisen only recently as a result of discoveries made from orbit:

1. What are the sources of surface volatiles on Mercury?
2. How late into Mercury's history did volcanism persist?
3. How did Mercury's long-wavelength topography change with time?
4. What is the origin of localized regions of enhanced exospheric density at Mercury?
5. How does the solar cycle affect Mercury's exosphere and volatile transport?
6. What is the origin of Mercury's energetic electrons?

"Advancements in science have at their core the evaluation of hypotheses in the light of new knowledge, sometimes resulting in slight changes in course, and other times resulting in paradigm shifts, opening up entirely new vistas of thought and perception," says MESSENGER Project Scientist Ralph McNutt, of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "With the early orbital observations at Mercury we are already seeing the beginnings of such advancements. The extended mission guarantees that the best is indeed ‘yet to be' on the MESSENGER mission, as this old-world Mercury, seen in a very new light, continues to give up its secrets."

Source: NASA

NASA's Fermi Finds Youngest Millisecond Pulsar, 100 Pulsars To-Date

 

A pulsar is a type of neutron star that emits electromagnetic energy at periodic intervals. A neutron star is the closest thing to a black hole that astronomers can observe directly, crushing half a million times more mass than Earth into a sphere no larger than a city. This matter is so compressed that even a teaspoonful weighs as much as Mount Everest.

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LWith this new batch of pulsars, Fermi now has detected more than 100, which is an exciting milestone when you consider that, before Fermi's launch in 2008, only seven of them were known to emit gamma rays," said Pablo Saz Parkinson, an astrophysicist at the Santa Cruz Institute for Particle Physics at the University of California Santa Cruz, and a co-author on two papers detailing the findings.

One group of pulsars combines incredible density with extreme rotation. The fastest of these so-called millisecond pulsars whirls at 43,000 revolutions per minute.

Millisecond pulsars are thought to achieve such speeds because they are gravitationally bound in binary systems with normal stars. During part of their stellar lives, gas flows from the normal star to the pulsar. Over time, the impact of this falling gas gradually spins up the pulsar's rotation.

The strong magnetic fields and rapid rotation of pulsars cause them to emit powerful beams of energy, from radio waves to gamma rays. Because the star is transferring rotational energy to the pulsar, the pulsar's spin slows after this transfer is completed.



This plot shows the positions of nine new pulsars (magenta) discovered by Fermi and of an unusual millisecond pulsar (green) that Fermi data reveal to be the youngest such object known. With this new batch of discoveries, Fermi has detected more than 100 pulsars in gamma rays.

Typically, millisecond pulsars are around a billion years old. However, in the Nov. 3 issue of Science, the Fermi team reveals a bright, energetic millisecond pulsar only 25 million years old.

The object, named PSR J1823−3021A, lies within NGC 6624, a spherical collection of ancient stars called a globular cluster, one of about 160 similar objects that orbit our galaxy. The cluster is about 10 billion years old and lies about 27,000 light-years away toward the constellation Sagittarius.

 

Fermi's Large Area Telescope (LAT) showed that eleven globular clusters emit gamma rays, the cumulative emission of dozens of millisecond pulsars too faint for even Fermi to detect individually. But that's not the case for NGC 6624.

It's amazing that all of the gamma rays we see from this cluster are coming from a single object. It must have formed recently based on how rapidly it's emitting energy. It's a bit like finding a screaming baby in a quiet retirement home," said Paulo Freire, the study's lead author, at the Max Planck Institute for Radio Astronomy in Bonn, Germany.

J1823−3021A was previously identified as a pulsar by its radio emission, yet of the nine new pulsars, none are millisecond pulsars, and only one was later found to emit radio waves.

Source: NASA