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Archive for April, 2013

Mysterious Hot Spots Observed In A Cool Red Supergiant

April 30, 2013 1 comment

Credit: University of Manchester

Credit: University of Manchester

Astronomers have released a new image of the outer atmosphere of Betelgeuse – one of the nearest red supergiants to Earth – revealing the detailed structure of the matter being thrown off the star.

The new image, taken by the e-MERLIN radio telescope array operated from the Jodrell Bank Observatory in Cheshire, also shows regions of surprisingly hot gas in the star’s outer atmosphere and a cooler arc of gas weighing almost as much as the Earth. The scientists publish their results in a paper in the Oxford University Press journal Monthly Notices of the Royal Astronomical Society.

Betelgeuse is easily visible to the unaided eye as the bright, red star on the top left shoulder of Orion the Hunter. The star itself is huge – 1,000 times larger than our Sun – but at a distance of about 650 light years it still appears as a tiny dot in the sky, so special techniques combining telescopes in arrays are required to see details of the star and the region around it.

The new e-MERLIN image of Betelgeuse shows its atmosphere extends out to five times the size of the visual surface of the star. It reveals two hot spots within the outer atmosphere and a faint arc of cool gas even farther out beyond the radio surface of the star.

Full Story: http://www.ras.org.uk/news-and-press/224-news-2013/2244-mysterious-hot-spots-observed-in-a-cool-red-supergiant

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Entire Galaxies Feel The heat From Newborn Stars: Bursts Of Star Birth Can Curtail Future Galaxy Growth


Image credit: ESA, NASA, L. Calçada

Image credit: ESA, NASA, L. Calçada

Astronomers using the NASA/ESA Hubble Space Telescope have shown for the first time that bursts of star formation have a major impact far beyond the boundaries of their host galaxy. These energetic events can affect galactic gas at distances of up to twenty times greater than the visible size of the galaxy — altering how the galaxy evolves, and how matter and energy is spread throughout the Universe.

When galaxies form new stars, they sometimes do so in frantic episodes of activity known as starbursts. These events were commonplace in the early Universe, but are rarer in nearby galaxies.

During these bursts, hundreds of millions of stars are born, and their combined effect can drive a powerful wind that travels out of the galaxy. These winds were known to affect their host galaxy — but this new research now shows that they have a significantly greater effect than previously thought.

An international team of astronomers observed 20 nearby galaxies, some of which were known to be undergoing a starburst. They found that the winds accompanying these star formation processes were capable of ionising gas up to 650 000 light-years from the galactic centre — around twenty times further out than the visible size of the galaxy. This is the first direct observational evidence of local starbursts impacting the bulk of the gas around their host galaxy, and has important consequences for how that galaxy continues to evolve and form stars.

Full Story: http://www.spacetelescope.org/news/heic1308/

VLA Gives Deep, Detailed Image Of Distant Universe


Ultra-Sensitive VLA Image of Distant Galaxies. Credit: Condon, et al., NRAO/AUI/NSF

Ultra-Sensitive VLA Image of Distant Galaxies. Credit: Condon, et al., NRAO/AUI/NSF

Staring at a small patch of sky for more than 50 hours with the ultra-sensitive Karl G. Jansky Very Large Array (VLA), astronomers have for the first time identified discrete sources that account for nearly all the radio waves coming from distant galaxies. They found that about 63 percent of the background radio emission comes from galaxies with gorging black holes at their cores and the remaining 37 percent comes from galaxies that are rapidly forming stars.

“The sensitivity and resolution of the VLA, following its decade-long upgrade, made it possible to identify the specific objects responsible for nearly all of the radio background emission coming from beyond our own Milky Way Galaxy,” said Jim Condon, of the National Radio Astronomy Observatory (NRAO). “Before we had this capability, we could not detect the numerous faint sources that produce much of the background emission,” he added.

Previous studies had measured the amount of radio emission coming from the distant Universe, but had not been capable of attributing all the radio waves to specific objects. In earlier observations, emission from two or more faint objects often was blurred or blended into what appeared to be a single, stronger source of radio waves.

Condon said. “The VLA now is a million times more sensitive than the radio telescopes that made landmark surveys of the sky in the 1960s.”

Full Story: http://www.nrao.edu/pr/2013/vladeep/#caption

Is Antimatter Anti-Gravity?


Antimatter is strange stuff. It has the opposite electrical charge to matter and, when it meets its matter counterpart, the two annihilate in a flash of light. Four University of California, Berkeley, physicists are now asking whether matter and antimatter are affected differently by gravity as well. Could antimatter fall upward – that is, exhibit anti-gravity – or fall downward at a different rate?

Almost everyone, including the physicists, thinks that antimatter will likely fall at the same rate as normal matter, but no one has ever dropped antimatter to see if this is true, said Joel Fajans, UC Berkeley professor of physics.

And while there are many indirect indications that matter and antimatter weigh the same, they all rely on assumptions that might not be correct. A few theorists have argued that some cosmological conundrums, such as why there is more matter than antimatter in the universe, could be explained if antimatter did fall upward.

In a new paper published online on April 30 in Nature Communications, the UC Berkeley physicists and their colleagues with the ALPHA experiment at CERN, the European Organization for Nuclear Research in Geneva, Switzerland, report the first direct measurement of gravity’s effect on antimatter, specifically antihydrogen in free fall. Though far from definitive – the uncertainty is about 100 times the expected measurement – the UC Berkeley experiment points the way toward a definitive answer to the fundamental question of whether matter falls up or down.

Full Story: http://newscenter.berkeley.edu/2013/04/30/is-antimatter-anti-gravity/

NGC 6240: Colossal Hot Cloud Envelopes Colliding Galaxies


Credit: X-ray (NASA / CXC / SAO / E.Nardini et al); Optical (NASA / STScI)

Credit: X-ray (NASA / CXC / SAO / E.Nardini et al); Optical (NASA / STScI)

Scientists have used Chandra to make a detailed study of an enormous cloud of hot gas enveloping two large, colliding galaxies. This unusually large reservoir of gas contains as much mass as 10 billion Suns, spans about 300,000 light years, and radiates at a temperature of more than 7 million degrees Kelvin.

This giant gas cloud, which scientists call a “halo,” is located in the system called NGC 6240. Astronomers have long known that NGC 6240 is the site of the merger of two large spiral galaxies similar in size to our own Milky Way. Each galaxy contains a supermassive black hole at its center. The black holes are spiraling toward one another, and may eventually merge to form a larger black hole.

Another consequence of the collision between the galaxies is that the gas contained in each individual galaxy has been violently stirred up. This caused a baby boom of new stars that has lasted for at least 200 million years. During this burst of stellar birth, some of the most massive stars raced through their evolution and exploded relatively quickly as supernovas.

Full Story and Images: http://www.chandra.harvard.edu/photo/2013/ngc6240/

NOAO: A Better View With Adaptive Optics Into The Heart Of A Globular Cluster


Astronomers at the Southern Observatory for Astrophysical Research (SOAR) and the Cerro Tololo Inter-American Observatory (CTIO) have demonstrated the significant difference that sharp stellar images can make in our understanding of the properties of stars. They have observed the globular cluster NGC 6496 using a new instrument dubbed SAM, for SOAR Adaptive Module, which creates an artificial laser guide star. SAM, built by CTIO/NOAO-S, is mounted on the SOAR 4.1 meter telescope.

From the surface of the earth, stars twinkle as their image wobbles around due to the effects of the Earth’s atmosphere, rather like observing a penny on the bottom of a swimming pool. By removing this wobble, using an adaptive optics system that utilizes a laser guide star, the stellar images are sharpened, and fainter stars appear. The accompanying figure shows this globular cluster, and the difference between the image of NGC 6496 with the artificial laser-produced guide star turned on and off. Turning on the artificial guide star allows the effect of the atmosphere to be determined so that the adaptive optical system can sharpens the image.

Full Story: http://www.noao.edu/news/2013/pr1304.php

Looking For Life By The Light Of Dying Stars


Because it has no source of energy, a dead star — known as a white dwarf — will eventually cool down and fade away. But circumstantial evidence suggests that white dwarfs can still support habitable planets, says Prof. Dan Maoz of Tel Aviv University’s School of Physics and Astronomy.

Now Prof. Maoz and Prof. Avi Loeb, Director of Harvard University’s Institute for Theory and Computation and a Sackler Professor by Special Appointment at TAU, have shown that, using advanced technology to become available within the next decade, it should be possible to detect biomarkers surrounding these planets — including oxygen and methane — that indicate the presence of life.

Published in the Monthly Notices of the Royal Astronomical Society, the researchers’ “simulated spectrum” demonstrates that the James Webb Space Telescope (JWST), set to be launched by NASA in 2018, will be capable of detecting oxygen and water in the atmosphere of an Earth-like planet orbiting a white dwarf after only a few hours of observation time — much more easily than for an Earth-like planet orbiting a sun-like star.

Full Story: http://www.aftau.org/site/News2?page=NewsArticle&id=18487