Largest Yellow Star Ever Found, 1300 Times The Sun's Diameter

Credit: ESO/Digitized Sky Survey 2 Using ESO's Very Large Telescope Interferometer (VLTI), Olivier Chesneau (Observatoire de la Côte d'Azur, Nice, France) and an international team of collaborators have found that the yellow hypergiant star HR 5171 A[1] is absolutely huge — 1300 times the diameter of the Sun and much bigger than was expected [2].  This makes it the largest yellow star known. It is also in the top ten of the largest stars known — 50% larger than the famous red supergiant Betelgeuse — and about one million times brighter than the Sun. HR 5171, the brightest star just below the centre of this wide-field image, is a yellow hypergiant, a very rare type of stars with only a dozen known in our galaxy. Its size is over 1,300 times that of the Sun -- one of the 10 largest stars found so far. Observations with ESO's Very Large Telescope Interferometer have shown that it is actually a double star, with the companion in contact with the main star. "The new observations also showed that this star has a very close binary partner, which was a real surprise," says Chesneau. "The two stars are so close that they touch and the whole system resembles a gigantic peanut." The astronomers made use of a technique called interferometry to combine the light collected from multipleindividual telescopes, effectively creating a...

Read More........→September 26, 2014

Extreme Power of Black Hole Revealed

Astronomers have used NASA's Chandra X-ray Observatory and a suite of other telescopes to reveal one of the most powerful black holes known. The black hole has created enormous structures in the hot gas surrounding it and prevented trillions of stars from forming The black hole is in a galaxy cluster named RX J1532.9+3021 (RX J1532 for short), located about 3.9 billion light years from Earth. The image here is a composite of X-ray data from Chandra revealing hot gas in the cluster in purple and optical data from the Hubble Space Telescope showing galaxies in yellow. The cluster is very bright in X-rays implying that it is extremely massive, with a mass about a quadrillion - a thousand trillion - times that of the sun. At the center of the cluster is a large elliptical galaxy containing the supermassive black hole. The large amount of hot gas near the center of the cluster presents a puzzle. Hot gas glowing with X-rays should cool, and the dense gas in the center of the cluster should cool the fastest. The pressure in this cool central gas is then expected to drop, causing gas further out to sink in towards the galaxy, forming trillions of stars along the way. However, astronomers have found no such evidence for this burst of stars forming at the center of this cluster. This problem has been noted in many galaxy clusters but...

Read More........→March 19, 2014

‘Death Stars’ In Orion Blast Planets Before They Form

Credit: NRAO/AUI/NSF; B. Saxton The Orion Nebula is home to hundreds of young stars and even younger protostars known as proplyds. Many of these nascent systems will go on to develop planets, while others will have their planet-forming dust and gas blasted away by the fierce ultraviolet radiation emitted by massive O-type stars that lurk nearby. This artist's concept shows two proplyds, or protostars, around a massive O-type star. The nearer proplyd is having its planet-forming dust and gas blasted away by the radiation from the star. The farther proplyd is able to retain its planet-making potential. A team of astronomers from Canada and the United States has used the Atacama Large Millimeter/submillimeter Array (ALMA) to study the often deadly relationship between highly luminous O-type stars and nearby protostars in the Orion Nebula. Their data reveal that protostars within 0.1 light-years (about 600 billion miles) of an O-type star are doomed to have their cocoons of dust and gas stripped away in just a few millions years, much faster than planets are able to form. "O-type stars, which are really monsters compared to our Sun, emit tremendous amounts of ultraviolet radiation and this can play havoc during the development of young planetary systems," remarked Rita Mann, an astronomer with the National Research Council...

Read More........→March 16, 2014

Herschel Discovers Water Vapor Around Dwarf Planet Ceres

Dwarf planet Ceres is located in the main asteroid belt, between the orbits of Mars and Jupiter, as illustrated in this artist's conception. Observations by the Herschel space observatory between 2011 and 2013 find that the dwarf planet has a thin water vapor atmosphere. This is the first unambiguous detection of water vapor around anobject in the asteroid belt. Illustration credit: ESA/ATG medialab, Note: For more information, see PIA17831: Water Detection on Ceres, Herschel Telescope Detects Water on Dwarf Planet and Herschel Discovers Water Vapor Around Dwarf Planet Ceres. Source: Article...

Read More........→January 25, 2014

Binary-Star Formation Theory Boosted By New Study

Credit: Bill Saxton, NRAO/AUI/NSF Using the new capabilities of the upgraded Karl G. Jansky Very Large Array (VLA), scientists have discovered previously-unseen binary companions to a pair of very young protostars. The discovery gives strong support for one of the competing explanations for how double-star systems form. Astronomers know that about half of all Sun-like stars are members of double or multiple-star systems, but have debated over how such systems are formed. Binary star formation through disk fragmentation starts (left) with a young star surrounded by a rotating disk of gas and dust. The disk fragments under its own gravity, with a second star forming within the disk (center), surrounded by its own disk. At right, the two stars form an orbiting pair. 100 Astronomical Units (AU) is roughly the diameter of our Solar System. "The only way to resolve the debate is to observe very young stellar systems and catch them in the act of formation," said John Tobin, of the National Radio Astronomy Observatory (NRAO). "That's what we've done with the stars we observed, and we got valuable new clues from them," he added. Their new clues support the idea that double-star systems form when a disk of gas and dust whirling around one young star fragments, forming another new star in orbit with the first. Young stars that still are...

Read More........→January 07, 2014