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Archive for April 2, 2013

New Insights On How Spiral Galaxies Get Their Arms

April 2, 2013 1 comment

Credit: NASA/ESA/Hubble Heritage Team

Credit: NASA/ESA/Hubble Heritage Team

Spiral galaxies are some of the most beautiful and photogenic residents of the universe. Our own Milky Way is a spiral. Our solar system and Earth reside somewhere near one of its filamentous arms. And nearly 70 percent of the galaxies closest to the Milky Way are spirals.

But despite their common shape, how galaxies like ours get and maintain their characteristic arms has proved to be an enduring puzzle in astrophysics. How do the arms of spiral galaxies arise? Do they change or come and go over time?

The answers to these and other questions are now coming into focus as researchers capitalize on powerful new computer simulations to follow the motions of as many as 100 million “stellar particles” as gravity and other astrophysical forces sculpt them into familiar galactic shapes. A team of researchers from the University of Wisconsin-Madison and the Harvard-Smithsonian Center for Astrophysics reports simulations that seem to resolve long-standing questions about the origin and life history of spiral arms in disk galaxies.

“We show for the first time that stellar spiral arms are not transient features, as claimed for several decades,” says UW-Madison astrophysicist Elena D’Onghia, who led the new research along with Harvard colleagues Mark Vogelsberger and Lars Hernquist. Vogelsberger added, “The spiral arms are self-perpetuating, persistent, and surprisingly long lived.”

Full Story: http://www.cfa.harvard.edu/news/2013/pr201310.html

Black Hole Wakes Up And Has A Light Snack


Astronomers have watched as a black hole woke up from a decades-long slumber to feed on a low-mass object – either a brown dwarf or a giant planet – that strayed too close. A similar feeding event, albeit on a gas cloud, will soon happen at the black hole at the centre of our own Milky Way Galaxy.

The discovery in galaxy NGC 4845, 47 million light-years away, was made by ESA’s Integral space observatory, with follow-up observations from ESA’s XMM-Newton, NASA’s Swift and Japan’s MAXI X-ray monitor on the International Space Station.

Astronomers were using Integral to study a different galaxy when they noticed a bright X-ray flare coming from another location in the same wide field-of-view. Using XMM-Newton, the origin was confirmed as NGC 4845, a galaxy never before detected at high energies.

Full Story and Video: http://www.esa.int/Our_Activities/Space_Science/Black_hole_wakes_up_and_has_a_light_snack

Supernova Remnant 1987A Continues To Reveal Its Secrets


A team of astronomers led by the International Centre for Radio Astronomy Research (ICRAR) have succeeded in observing the death throws of a giant star in unprecedented detail.

In February of 1987 astronomers observing the Large Magellanic Cloud, a nearby dwarf galaxy, noticed the sudden appearance of what looked like a new star. In fact they weren’t watching the beginnings of a star but the end of one and the brightest supernova seen from Earth in the four centuries since the telescope was invented. By the next morning news of the discovery had spread across the globe and southern hemisphere stargazers began watching the aftermath of this enormous stellar explosion, known as a supernova.

In the two and a half decades since then, the remnant of Supernova 1987A has continued to be a focus for researchers around the world, providing a wealth of information about one of the Universe’s most extreme events.

Full Story: http://www.icrar.org/news/news_items/media-releases/supernova-remnant-1987a-continues-to-reveal-its-secrets