NASA'S Spitzer Finds Distant Galaxies Grazed On Gas

Trent J. Perrotto

Headquarters, Washington

 

Whitney Clavin

Jet Propulsion Laboratory, Pasadena, Calif.

WASHINGTON -- Galaxies once thought of as voracious tigers are more like grazing cows, according to a new study using NASA's Spitzer Space Telescope.

Astronomers have discovered that galaxies in the distant universe continuously ingested their star-making fuel over long periods of time. This goes against previous theories that galaxies devoured their fuel in quick bursts after run-ins with other galaxies.

"Our study shows the merging of massive galaxies was not the dominant method of galaxy growth in the distant universe," said Ranga-Ram Chary of NASA's Spitzer Science Center at the California Institute of Technology in Pasadena, Calif. "We're finding this type of galactic cannibalism was rare. Instead, we are seeing evidence for a mechanism of galaxy growth in which a typical galaxy fed itself through a steady stream of gas, making stars at a much faster rate than previously thought."

Chary is the principal investigator of the research appearing in the Aug. 1 issue of the Astrophysical Journal. According to his findings, these grazing galaxies fed steadily over periods of hundreds of millions of years and created an unusual amount of plump stars, up to 100 times the mass of our sun.

"This is the first time that we have identified galaxies that supersize themselves by grazing," said Hyunjin Shim, also of the Spitzer Science Center and lead author of the paper. "They have many more massive stars than our Milky Way galaxy."

Galaxies like our Milky Way are giant collections of stars, gas and dust. They grow in size by feeding off gas and converting it to new stars. A long-standing question in astronomy is: Where did distant galaxies that formed billions of years ago acquire this stellar fuel?

The most favored theory was that galaxies grew by merging with other galaxies, feeding off gas stirred up in the collisions.

Chary and his team addressed this question by using Spitzer to survey more than 70 remote galaxies that existed 1 to 2 billion years after the big bang (our universe is approximately 13.7 billion years old). To the surprise of the astronomers, these galaxies were blazing with what is called H alpha, radiation from hydrogen gas that has been hit with ultraviolet light from stars. High levels of H alpha indicate stars are forming vigorously. Seventy percent of the surveyed galaxies show strong signs of H alpha. By contrast, only 0.1 percent of galaxies in our local universe possess the signature.

Previous studies using ultraviolet-light telescopes found about six times less star formation than Spitzer, which sees infrared light.

Scientists think this may be due to large amounts of obscuring dust, through which infrared light can sneak. Spitzer opened a new window onto the galaxies by taking very long-exposure infrared images of a patch of sky called the GOODS fields, for Great Observatories Origins Deep Survey.

NASA's Jet Propulsion Laboratory in Pasadena manages the Spitzer Space Telescope mission for the agency's Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center. Caltech manages JPL for NASA. For more information about Spitzer, visit http://www.nasa.gov/spitzer.

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A Green Ring Fit for a Superhero

This glowing emerald nebula seen by NASA's Spitzer Space Telescope is reminiscent of the glowing ring wielded by the superhero Green Lantern. In the comic books and the Hollywood movie, the diminutive Guardians of the Planet "Oa" forged his power ring, but astronomers believe rings like this are actually sculpted by the powerful light of giant "O" stars, the most massive type of star known to exist.

Named RCW 120, this region of hot gas and glowing dust can be found in the murky clouds encircled by the tail of the constellation Scorpius. The ring of dust actually is glowing in infrared colors that our eyes cannot see, but show up brightly when viewed by Spitzer's infrared detectors. At the center of this ring are a couple of giant stars whose intense ultraviolet light has carved out the bubble, though they blend in with other stars when viewed in infrared.

This bubble is far from unique. Just as the Guardians of Oa have selected many beings to serve as Green Lanterns and patrol different sectors of space, Spitzer has found that such bubbles are common and an can be found around O stars throughout our Milky Way galaxy. The small objects at the lower right area of the image may themselves be similar regions seen at much greater distances across the galaxy.

Rings like this are so common in Spitzer's observations that astronomers have even enlisted the help of the public to help them find and catalog them all. Anyone interested in joining the search as a citizen scientist can visit "The Milky Way Project," part of the "Zooniverse" of public astronomy projects, at http://www.milkywayproject.org/.

Image Credit: NASA/JPL-Caltech

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NASA Telescopes Help Discover Surprisingly Young Galaxy

Trent Perrotto

Headquarters, Washington

 

Whitney Clavin

Jet Propulsion Laboratory, Pasadena, Calif.

 

Ray Villard

Space Telescope Science Institute, Baltimore, Md.

 

Larry O'Hanlon

W.M. Keck Observatory, Mauna Kea, Hawaii

WASHINGTON -- Astronomers have uncovered one of the youngest galaxies in the distant universe, with stars that formed 13.5 billion years ago, a mere 200 million years after the big bang. The finding addresses questions about when the first galaxies arose, and how the early universe evolved.

NASA's Hubble Space Telescope was the first to spot the newfound galaxy. Detailed observations from the W.M. Keck Observatory on Mauna Kea in Hawaii revealed the observed light dates to when the universe was only 950 million years old; the universe formed about 13.7 billion years ago.

Infrared data from both Hubble and NASA's Spitzer Space Telescope revealed the galaxy's stars are quite mature, having formed when the universe was just a toddler at 200 million years old.

"This challenges theories of how soon galaxies formed in the first years of the universe," said Johan Richard of the Centre de Recherche Astronomique de Lyon, Université Lyon 1 in France, lead author of a new study accepted for publication in the Monthly Notices of the Royal Astronomical Society. "It could even help solve the mystery of how the hydrogen fog that filled the early universe was cleared."

This galaxy is not the most distant ever observed, but it is one of the youngest to be observed with such clarity. Normally, galaxies like this one are extremely faint and difficult to study, but, in this case, nature has provided the astronomers with a cosmic magnifying glass. The galaxy's image is being magnified by the gravity of a massive cluster of galaxies parked in front of it, making it appear 11 times brighter. This phenomenon is called gravitational lensing.

"Without this big lens in space, we could not study galaxies this faint with currently available observing facilities," said co-author Eiichi Egami of the University of Arizona in Tucson. "Thanks to nature, we have this great opportunity to see our universe as it was eons ago."

The findings may help explain how the early universe became "reionized." At some point in our universe's early history, it transitioned from the so-called dark ages to a period of light, as the first stars and galaxies began to ignite. This starlight ionized neutral hydrogen atoms floating around in space, giving them a charge. Ultraviolet light could then travel unimpeded through what had been an obscuring fog.

The discovery of a galaxy possessing stars that formed only 200 million years after the big bang helps astronomers probe this cosmic reionization epoch. When this galaxy was developing, its hot, young stars would have ionized vast amounts of the neutral hydrogen gas in intergalactic space. A population of similar galaxies probably also contributed to this reionization, but they are too faint to see without the magnifying effects of gravitational lensing.

NASA's James Webb Space Telescope (JWST), scheduled to launch later this decade, will be able to see these faint galaxies lacking magnification. A successor to Hubble and Spitzer, JWST will see infrared light from the missing population of early galaxies. As a result, the mission will reveal some of our universe's best-kept secrets.

"Seeing a galaxy as it appeared near the beginning of the universe is an awe-inspiring feat enabled by innovative technology and the fortuitous effect of gravitational lensing," said Jon Morse, NASA's Astrophysics Division director at the agency's headquarters in Washington.

"Observations like this open a window across space and time, but more importantly, they inspire future work to one day peer at the stars that lit up the universe following the big bang."

For more information about Spitzer and Hubble, visit http://www.nasa.gov/spitzer and http://www.nasa.gov/hubble.

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NASA Telescopes Help Discover Surprisingly Young Galaxy

Trent Perrotto

Headquarters, Washington

 

Whitney Clavin

Jet Propulsion Laboratory, Pasadena, Calif.

 

Ray Villard

Space Telescope Science Institute, Baltimore, Md.

 

Larry O'Hanlon

W.M. Keck Observatory, Mauna Kea, Hawaii

WASHINGTON -- Astronomers have uncovered one of the youngest galaxies in the distant universe, with stars that formed 13.5 billion years ago, a mere 200 million years after the big bang. The finding addresses questions about when the first galaxies arose, and how the early universe evolved.

NASA's Hubble Space Telescope was the first to spot the newfound galaxy. Detailed observations from the W.M. Keck Observatory on Mauna Kea in Hawaii revealed the observed light dates to when the universe was only 950 million years old; the universe formed about 13.7 billion years ago.

Infrared data from both Hubble and NASA's Spitzer Space Telescope revealed the galaxy's stars are quite mature, having formed when the universe was just a toddler at 200 million years old.

"This challenges theories of how soon galaxies formed in the first years of the universe," said Johan Richard of the Centre de Recherche Astronomique de Lyon, Université Lyon 1 in France, lead author of a new study accepted for publication in the Monthly Notices of the Royal Astronomical Society. "It could even help solve the mystery of how the hydrogen fog that filled the early universe was cleared."

This galaxy is not the most distant ever observed, but it is one of the youngest to be observed with such clarity. Normally, galaxies like this one are extremely faint and difficult to study, but, in this case, nature has provided the astronomers with a cosmic magnifying glass. The galaxy's image is being magnified by the gravity of a massive cluster of galaxies parked in front of it, making it appear 11 times brighter. This phenomenon is called gravitational lensing.

"Without this big lens in space, we could not study galaxies this faint with currently available observing facilities," said co-author Eiichi Egami of the University of Arizona in Tucson. "Thanks to nature, we have this great opportunity to see our universe as it was eons ago."

The findings may help explain how the early universe became "reionized." At some point in our universe's early history, it transitioned from the so-called dark ages to a period of light, as the first stars and galaxies began to ignite. This starlight ionized neutral hydrogen atoms floating around in space, giving them a charge. Ultraviolet light could then travel unimpeded through what had been an obscuring fog.

The discovery of a galaxy possessing stars that formed only 200 million years after the big bang helps astronomers probe this cosmic reionization epoch. When this galaxy was developing, its hot, young stars would have ionized vast amounts of the neutral hydrogen gas in intergalactic space. A population of similar galaxies probably also contributed to this reionization, but they are too faint to see without the magnifying effects of gravitational lensing.

NASA's James Webb Space Telescope (JWST), scheduled to launch later this decade, will be able to see these faint galaxies lacking magnification. A successor to Hubble and Spitzer, JWST will see infrared light from the missing population of early galaxies. As a result, the mission will reveal some of our universe's best-kept secrets.

"Seeing a galaxy as it appeared near the beginning of the universe is an awe-inspiring feat enabled by innovative technology and the fortuitous effect of gravitational lensing," said Jon Morse, NASA's Astrophysics Division director at the agency's headquarters in Washington.

"Observations like this open a window across space and time, but more importantly, they inspire future work to one day peer at the stars that lit up the universe following the big bang."

For more information about Spitzer and Hubble, visit http://www.nasa.gov/spitzer and http://www.nasa.gov/hubble.

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