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Archive for August 4, 2014

Mapping Dark Matter, 4.5 Billion light Years Away


Credit: ESA/Hubble, NASA, HST Frontier Fields

Credit: ESA/Hubble, NASA, HST Frontier Fields

Using the NASA/ESA Hubble Space Telescope, an international team of astronomers have mapped the mass within a galaxy cluster more precisely than ever before. Created using observations from Hubble’s Frontier Fields observing programme, the map shows the amount and distribution of mass within MCS J0416.1–2403, a massive galaxy cluster found to be 160 trillion times the mass of the Sun.

The detail in this ‘mass map’ was made possible thanks to the unprecedented depth of data provided by new Hubble observations, and the cosmic phenomenon known as strong gravitational lensing. The team, led by Dr Mathilde Jauzac of Durham University in the UK and the Astrophysics & Cosmology Research Unit in South Africa, publish their results in the journal Monthly Notices of the Royal Astronomical Society.

Measuring the amount and distribution of mass within distant objects in the Universe can be very difficult. A trick often used by astronomers is to explore the contents of large clusters of galaxies by studying the gravitational effects they have on the light from very distant objects beyond them. This is one of the main goals of Hubble’s Frontier Fields, an ambitious observing programme scanning six different galaxy clusters — including MCS J0416.1–2403.

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NASA’s Fermi Space Telescope Reveals New Source Of Gamma Rays


Image Credit: NASA/DOE/Fermi LAT Collaboration

Image Credit: NASA/DOE/Fermi LAT Collaboration

Observations by NASA’s Fermi Gamma-ray Space Telescope of several stellar eruptions, called novae, firmly establish these relatively common outbursts almost always produce gamma rays, the most energetic form of light.

“There’s a saying that one is a fluke, two is a coincidence, and three is a class, and we’re now at four novae and counting with Fermi,” said Teddy Cheung, an astrophysicist at the Naval Research Laboratory in Washington, and the lead author of a paper reporting the findings in the Aug. 1 edition of the journal Science.

A nova is a sudden, short-lived brightening of an otherwise inconspicuous star caused by a thermonuclear explosion on the surface of a white dwarf, a compact star not much larger than Earth. Each nova explosion releases up to 100,000 times the annual energy output of our sun. Prior to Fermi, no one suspected these outbursts were capable of producing high-energy gamma rays, emission with energy levels millions of times greater than visible light and usually associated with far more powerful cosmic blasts.

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Hubble Shows Farthest Lensing Galaxy Yields Clues To Early Universe


Credit: NASA, ESA, K.-V. Tran (Texas A&M University), and K. Wong (Academia Sinica Institute of Astronomy & Astrophysics)

Credit: NASA, ESA, K.-V. Tran (Texas A&M University), and K. Wong (Academia Sinica Institute of Astronomy & Astrophysics)

Astronomers using NASA’s Hubble Space Telescope have unexpectedly discovered the most distant cosmic magnifying glass, produced by a monster elliptical galaxy. Seen here as it looked 9.6 billion years ago, this monster elliptical galaxy breaks the previous record holder by 200 million years. These “lensing” galaxies are so massive that their gravity bends, magnifies, and distorts light from objects behind them, a phenomenon called gravitational lensing.

The object behind the cosmic lens is a tiny spiral galaxy undergoing a rapid burst of star formation. Its light has taken 10.7 billion years to arrive here. Seeing this chance alignment at such a great distance from Earth is a rare find.

Locating more of these distant lensing galaxies will offer insight into how young galaxies in the early universe built themselves up into the massive dark-matter-dominated galaxies of today. Dark matter cannot be seen, but it accounts for the bulk of the universe’s matter.

“When you look more than 9 billion years ago in the early universe, you don’t expect to find this type of galaxy-galaxy lensing at all,” explained lead researcher Kim-Vy Tran of Texas A&M University in College Station. “It’s very difficult to see an alignment between two galaxies in the early universe.”

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