Farthest Galaxy Yet Revealed by Cosmic Lens

Charles Q. Choi, SPACE.com, 09/20/12

The earliest known confirmed galaxy has been discovered with the help of cosmic lenses formed out of the warped fabric of space and time, researchers say.

This distant, ancient galaxy may have once helped clear out the murky fog that once filled the early universe, scientists added.

Astronomers estimate that the universe began about 13.7 billion years ago during the Big Bang. Recent findings suggest the first galaxies formed less than 500 million years after the universe's birth.

Little is known about the earliest galaxies since their light is very faint, given how far away they are. One tool researchers can use to peer at these galaxies are so-called gravitational lenses, magnifying glasses resulting from the warped fabric of reality.

Gravity curves space-time; the greater the mass of an object in space, the stronger its gravitational pull. This, in turn, bends light around it, affecting how telescopes on Earth view it. [Big Bang to Now in 10 Easy Steps]

Astronomers can gauge the age of an object by estimating its distance. Since the speed of light appears the same throughout the universe, knowing how far away an object is reveals how long it took for its light to get here. Scientists can work out the distance of an object by looking at how much the light from it is distorted.

Using gravitational lensing caused by one of the most massive known galaxy clusters, scientists glimpsed a galaxy that existed when the universe was about 500 million years old using two NASA space observatories: the Hubble Space Telescope and the Spitzer Space Telescope.

Based on its level of development, the researchers estimate this galaxy is about 150 million times the mass of the sun and formed less than 200 million years after the Big Bang. This is currently the earliest known and most distant galaxy that scientists have confidently identified.

"We feel like archaeologists with a pre-Neanderthal fossil in hand," lead study author Wei Zheng, an astronomer at Johns Hopkins University, told SPACE.com.

Astronomers have detected potentially older galaxies, but their faintness makes it difficult to make out key details regarding their age.

"Such a discovery would not have been possible if the object was un-lensed," Zheng said.

The age of this galaxy reveals it formed during the so-called "epoch of reionization" that occurred about 150 million to 800 million years after the Big Bang. This critical but still largely mysterious event occurred when intense ultraviolet radiation cleared the fog of atomic hydrogen that once pervaded the cosmos by ionizing it into its constituent protons and electrons.

"This provides us with a unique glimpse of star formation and galaxy growth in the period spanning 300 [million] to 500 million years after the Big Bang," astronomer Daniel Stark at the University of Arizona at Tucson, who did not take part in this study, told SPACE.com. "While caution should be exercised in the interpretation of a single object, the results presented in the Zheng paper point to significant star formation activity throughout this period."

Much remains uncertain as to what sources of radiation caused the epoch of reionization. Since the researchers found this ancient galaxy after only monitoring a small patch of sky, Zheng said the early universe may have overall been rich with galaxies that drove reionization.

The scientists detailed their findings in the Sept. 20 issue of the journal Nature.

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Mysterious Origin of Cosmic Rays Pinned Down

Clara Moskowitz, Staff Writer, SPACE.com

WASHINGTON – Superfast protons sometimes slam into the Earth from space flying at close to the speed of light.

Where these particles, called cosmic rays, come from has been a scientific mystery. But new evidence helps confirm the leading explanation – that they originate in the distant remnants of dead stars.

Such a so called supernova remnants contains shells of gas that were ejected from a star before it collapsed in a supernova explosion. They harbor strong magnetic fields that are thought to behave like giant particle accelerators, speeding up particles that become cosmic rays.

New observations from NASA's Fermi Gamma-ray Space Telescope reveal supernova remnants that are emitting radiation a billion times more energetic than visible light. This radiation, which is the short-wavelength gamma ray light, could be a signature of cosmic rays, which are thought to produce gamma rays when they collide with gas.

"Understanding the sources of cosmic rays is one of Fermi's key goals," said Stefan Funk, an astrophysicist at the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University and the SLAC National Accelerator Laboratory in Menlo Park, Calif. "Fermi now allows us to compare emission from remnants of different ages and in different environments."

Funk presented the findings Monday at a meeting of the American Physical Society in Washington, D.C.
Fermi's Large Area Telescope (LAT) observed gamma ray light from three supernova remnants called W51C, W44, and IC 443, whose stars died between 4,000 and 30,000 years ago. The telescope also spied a much younger remnant, called Cassiopeia A, which is only about 330 years old.

"Older remnants are extremely bright in GeV gamma rays, but relatively faint at higher energies. Younger remnants show a different behavior," said Yasunobu Uchiyama, a Panofsky Fellow at SLAC. "Perhaps the highest-energy cosmic rays have left older remnants, and Fermi sees emission from trapped particles at lower energies."

Scientists think that the younger supernova remnants have stronger magnetic fields, which are able to hold on to particles long enough to accelerate them to the highest speeds, creating the highest-energy cosmic rays.

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Galaxy's Dying Stars Confirm Cosmic Ray Source

Clara Moskowitz, Staff Writer, SPACE.com 

Recent photographs of an active galaxy offer new confirmation for the idea that supernova explosions are the creators of surprisingly energetic particles called cosmic rays.

Cosmic rays are protons that whiz through space at almost the speed of light. They originate far beyond the solar system, but when some make it past Earth's atmosphere they can carry such an energetic punch that they knock out electronics systems. Scientists have long been unsure of the process that ramps the particles up to such great speeds, though gathering evidence suggests that these super-fast protons originate during the death of a star

When a very large star dies, it implodes into a black hole while expelling its outer layers in a powerful explosion called a supernova. Scientists think that some of the energy released during these blasts acts as a sort of supercharger, accelerating particles to extremely fast speeds and creating cosmic rays.

New proof of this idea has come from recent observations of the Cigar Galaxy (M82) by the VERITAS gamma ray telescope array in Amado, Ariz. The galaxy sits about 12 million light-years from Earth in the direction of the constellation Ursa Major (also known as the Big Dipper). It is a starburst galaxy, meaning it has exceptionally high levels of star formation.

With so many stars forming in M82, there are also high numbers of massive stars and supernovas, making the galaxy a perfect testing ground for the cosmic ray explanation. If supernovas are responsible for cosmic rays, scientists figured, then a place with more of the stellar explosions will also have higher concentrations of the energetic particles.

Indeed, researchers found that the density of cosmic rays in M82 was 500 times that of the Milky Way, confirming the hypothesis.

"This discovery provides fundamental insight into the origin of cosmic rays," said Rene Ong, a professor of physics at the University of California, Los Angeles, and the spokesperson for the VERITAS collaboration.

Though the telescope couldn't image cosmic rays directly in the distant galaxy, the researchers looked for gamma rays, a very energetic form of light produced when cosmic rays interact with gas and radiation within the galaxy. They used this measurement to extrapolate how many cosmic rays lie within M82.

The findings are detailed in the Nov. 1 online issue of the journal Nature.

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