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Phoenix update

Scientists report on the progress of the Phoenix lander exploring the northern plains of Mars during this July 31 update.

 Briefing | Panorama

Expedition 18 crew

The American, Russian and Japanese crewmembers to serve aboard the space station during various stages of the Expedition 18 mission, plus spaceflight participant Richard Garriott hold this pre-flight news conference.

 Play

STS-94: Rapid re-flight

Three months after their 1997 flight was cut short by a fuel cell problem, the same seven astronauts returned to space aboard shuttle Columbia to fulfill the Spacelab science mission. The STS-94 crew tells the story in this post-flight presentation.

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STS-124: In review

The STS-124 crew narrates highlights from its mission that delivered Japan's Kibo lab module to the station.

 Full presentation
 Mission film

Jason 2 launch

A ULA Delta 2 rocket launched the Jason 2 oceanography satellite from Vandenberg Air Force Base on June 20.

 Full Coverage

Jason 2 preview

The joint American and European satellite project called Jason 2 will monitor global seal levels.

 Mission | Science

STS-124 space shuttle mission coverage

Extensive video collection covering shuttle Discovery's mission to deliver the Japanese Kibo science lab to the station is available in the archives.

 Full Coverage

Phoenix lands on Mars

The Phoenix spacecraft arrived at Mars on May 25, safely landing on the northern plains to examine the soil and water ice.

 Full Coverage

STS-82: In review

The second servicing of the Hubble Space Telescope was accomplished in Feb. 1997 when the shuttle astronauts replaced a pair of instruments and other internal equipment on the observatory.

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The first stars
HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS NEWS RELEASE
Posted: July 31, 2008

The universe began with the Big Bang about 13.7 billion years ago. Very soon after that event, the first stars formed. Today, those stars are dead and gone leaving little evidence of their size and composition behind. Now, a new computer simulation now offers the most detailed picture yet of how these first stars came into existence. These findings will be published by the journal Science on Friday, 1 August.


In this artist impression, swirling clouds of hydrogen and helium gasses are illuminated by the first starlight to shine in the Universe. In the lower portion of the artwork, a supernova explodes ejecting heavier elements that will someday be incorporated into new stars and planets. Credit: David A. Aguilar, CfA
 
The composition of the early universe was quite different from that of today, and the physics that governed the early universe were also somewhat simpler. Dr. Naoki Yoshida, Nagoya University in Nagoya, Japan and co-author Dr. Lars Hernquist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA, incorporated these conditions of the early universe, sometimes referred to as the "cosmic dark ages," to simulate the formation of an astronomical object that would eventually shine as a star.

According to their simulations, gravity acted on minute density variations in matter, gases, and the mysterious "dark matter" of the universe after the Big Bang in order to form the early stages of a star called a protostar. With a mass of just one percent of our Sun, Dr. Yoshida's simulation also shows that the protostar would likely evolve into a massive star capable of synthesizing heavy elements, not just in later generations of stars, but soon after the Big Bang. These stars would have been up to one hundred times as massive as our Sun and would have burned for no more than one million years.

"This general picture of star formation, and the ability to compare how stellar objects form in different time periods and regions of the universe, will eventually allow investigation in the origins of life and planets," said Hernquist.

"The abundance of elements in the Universe has increased as stars have accumulated," he says, "and the formation and destruction of stars continues to spread these elements further across the Universe. So when you think about it, all of the elements in our bodies originally formed from nuclear reactions in the centers of stars, long ago."

Their simulation of the birth of a protostar in the early universe signifies a key step toward the ambitious goal of piecing together the formation of an entire primordial star and of predicting the mass and properties of these first stars of the universe. More powerful computers, more physical data, and an even larger range will be needed for further calculations and simulations, but these researchers hope to eventually extend this simulation to the point of nuclear reaction initiation ­ when a stellar object becomes a true star.

"Dr. Yoshida has taken the study of primordial star formation to a new level with this simulation, but it still gets us only to the halfway point towards our final goal. It is like laying the foundation of a skyscraper," said Volker Bromm, Assistant Professor of Astronomy at the University of Texas, Austin and the author of a companion article. "We must continue our studies in this area to understand how the initially tiny protostar grows, layer by layer, to eventually form a massive star. But here, the physics become much more complicated and even more computational resources are needed."

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.