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Archive for February 19, 2014

Diamonds In The Tail Of The Scorpion

February 19, 2014 Leave a comment

Credit: ESO

Credit: ESO

A new image from ESO’s La Silla Observatory in Chile shows the bright star cluster Messier 7. Easily spotted with the naked eye close to the tail of the constellation of Scorpius, it is one of the most prominent open clusters of stars in the sky — making it an important astronomical research target.

Messier 7, also known as NGC 6475, is a brilliant cluster of about 100 stars located some 800 light-years from Earth. In this new picture from the Wide Field Imager on the MPG/ESO 2.2-metre telescope it stands out against a very rich background of hundreds of thousands of fainter stars, in the direction of the centre of the Milky Way.

At about 200 million years old, Messier 7 is a typical middle-aged open cluster, spanning a region of space about 25 light-years across. As they age, the brightest stars in the picture — a population of up to a tenth of the total stars in the cluster — will violently explode as supernovae. Looking further into the future, the remaining faint stars, which are much more numerous, will slowly drift apart until they become no longer recognisable as a cluster.

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NASA’s NuSTAR Untangles Mystery Of How Stars Explode

February 19, 2014 Leave a comment

Image credit: NASA/JPL-Caltech/CXC/SAO

Image credit: NASA/JPL-Caltech/CXC/SAO

One of the biggest mysteries in astronomy, how stars blow up in supernova explosions, finally is being unraveled with the help of NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR).

The high-energy X-ray observatory has created the first map of radioactive material in a supernova remnant. The results, from a remnant named Cassiopeia A (Cas A), reveal how shock waves likely rip apart massive dying stars.

“Stars are spherical balls of gas, and so you might think that when they end their lives and explode, that explosion would look like a uniform ball expanding out with great power,” said Fiona Harrison, the principal investigator of NuSTAR at the California Institute of Technology (Caltech) in Pasadena. “Our new results show how the explosion’s heart, or engine, is distorted, possibly because the inner regions literally slosh around before detonating.”

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Astronomers At The National Observatory Continue To Watch Sn 2014J

February 19, 2014 Leave a comment

SN2014J-4m_smThe astronomical community was very excited by the appearance of a supernova in a relatively nearby galaxy in late January 2014. Observations of this supernova, located in the galaxy M 82, and referred to as SN2014J revealed that it is a type Ia. These occur in a binary star system composed of a dense white dwarf star and a companion star, either another white dwarf or a bloated red giant star. These supernovae are especially interesting because they provide one of the best ways to measure distances to faint galaxies, and therefore calibrate the expansion of the universe. At Kitt Peak National Observatory (KPNO), two different teams have been observing SN2014J.

At the Mayall 4-meter telescope on KPNO Dr. Ginger Bryngelson (Francis Marion University) and Dina Drozdov (Clemson University) were serendipitously engaged in a program to observe the slow fading of other previously known Ia supernovae when SN2014J was first spotted, and immediately added this one to their program. As Ms. Drozdov said,” Since this one is so nearby, we will be able to monitor it for much longer past its explosion than others. It will become one of the most widely-studied in history.”

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Clouds Circling Supermassive Black Holes

February 19, 2014 Leave a comment

Artist's concept. Credit: NASA / JPL / Caltech

Artist’s concept. Credit: NASA / JPL / Caltech

Astronomers see huge clouds of gas orbiting supermassive black holes at the centres of galaxies. Once thought to be a relatively uniform, fog-like ring, the accreting matter instead forms clumps dense enough to intermittently dim the intense radiation blazing forth as these enormous objects condense and consume matter.

The international team reports their sightings in a paper to be published in the Monthly Notices of the Royal Astronomical Society, available online now. Videos depicting the swirling clouds are posted to YouTube.

Evidence for the clouds comes from records collected over 16 years by NASA’s Rossi X-ray Timing Explorer, a satellite in low-earth orbit equipped with instruments that measured variations in X-ray sources. Those sources include active galactic nuclei, brilliantly luminous objects powered by supermassive black holes as they gather and condense huge quantities of dust and gas.

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Rocks Around The Clock: Asteroids Pound Tiny Star

February 19, 2014 Leave a comment

Artist's impression. Credit: NASA/JPL-Caltech

Artist’s impression. Credit: NASA/JPL-Caltech

Scientists using CSIRO’s Parkes telescope and another telescope in South Africa have found evidence that a tiny star called PSR J0738-4042 is being pounded by asteroids — large lumps of rock from space.

“One of these rocks seems to have had a mass of about a billion tonnes,” CSIRO astronomer and member of the research team Dr Ryan Shannon said.

PSR J0738-4042 lies 37,000 light-years from Earth in the constellation of Puppis.

The environment around this star is especially harsh, full of radiation and violent winds of particles.

“If a large rocky object can form here, planets could form around any star. That’s exciting,” Dr Shannon said.

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Hubble Watches Stars’ Clockwork Motion In Nearby Galaxy

February 19, 2014 Leave a comment

Artist's Concept. Image Credit: NASA, ESA, A. Feild and Z. Levay (STScI), Y. Beletsky (Las Campanas Observatory), and R. van der Marel (STScI)

Artist’s Concept. Image Credit: NASA, ESA, A. Feild and Z. Levay (STScI), Y. Beletsky (Las Campanas Observatory), and R. van der Marel (STScI)

Using the sharp-eyed NASA Hubble Space Telescope, astronomers have for the first time precisely measured the rotation rate of a galaxy based on the clock-like movement of its stars.

According to their analysis, the central part of the neighboring galaxy, called the Large Magellanic Cloud (LMC), completes a rotation every 250 million years. Coincidentally, it takes our Sun the same amount of time to complete a rotation around the center of our Milky Way galaxy. The arrows in this photo illustration represent the highest-quality Hubble measurements of the motion of the LMC’s stars to show how the galaxy rotates.

The Hubble team, composed of Roeland van der Marel of the Space Telescope Science Institute in Baltimore, Md., and Nitya Kallivayalil of the University of Virginia in Charlottesville, Va., used Hubble to measure the average motion of hundreds of individual stars in the LMC, located 170,000 light-years away. Hubble recorded the stars’ slight movements over a seven-year period.

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When A Black Hole Shreds A Star, A Bright Flare Tells The Story

February 19, 2014 Leave a comment

Computer simulation. Image by James Guillochon

Computer simulation. Image by James Guillochon

Enrico Ramirez-Ruiz uses computer simulations to explore the universe’s most violent events, so when the first detailed observations of a star being ripped apart by a black hole were reported in 2012 (Gezari et al., Nature), he was eager to compare the data with his simulations. He was also highly skeptical of one of the published conclusions: that the disrupted star was a rare helium star.

“I was sure it was a normal hydrogen star and we were just not understanding what’s going on,” said Ramirez-Ruiz, a professor of astronomy and astrophysics at the University of California, Santa Cruz.

In a paper accepted for publication in the Astrophysical Journal and available online at arXiv.org, Ramirez-Ruiz and his students explain what happens during the disruption of a normal sun-like star by a supermassive black hole, and they show why observers might fail to see evidence of the hydrogen in the star. First author and UCSC graduate student James Guillochon (now an Einstein Fellow at Harvard University) and undergraduate Haik Manukian worked with Ramirez-Ruiz to run a series of detailed computer simulations of encounters between stars and black holes.

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