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Posts Tagged ‘protostar’

‘Death Stars’ In Orion Blast Planets Before They Even Form


Artist's concept. Credit: NRAO/AUI/NSF; B. Saxton

Artist’s concept. 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.

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 of Canada in Victoria, and lead author on a paper in the Astrophysical Journal. “Using ALMA, we looked at dozens of embryonic stars with planet-forming potential and, for the first time, found clear indications where protoplanetary disks simply vanished under the intense glow of a neighboring massive star.”

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Commentary On The Press Release “A Drastic Chemical Change Occurring In Birth Of Planetary System: Has The Solar System Also Experienced it?”

February 13, 2014 Leave a comment

An infrared image of the protostar L1527 taken by the Spitzer Space Telescope. Credit: J. Tobin/NASA/JPL-Caltech

An infrared image of the protostar L1527 taken by the Spitzer Space Telescope.
Credit: J. Tobin/NASA/JPL-Caltech

Stars are formed by the contraction of interstellar gas and dust. Around a protostar, gas and dust form a disk in which planets are eventually formed. Then, are the chemical compositions of the interstellar cloud and the disk identical? The new ALMA observations show that the answer is ‘no.’ This finding has a large impact on understandings of the formation process of planets and protoplanetary disks.

The international research team, led by Dr. Nami Sakai, an assistant professor at the Department of Physics, The University of Tokyo, observed a baby star L1527 in the constellation Taurus with ALMA. The team observed radio emission from cyclic-C3H2 [note 1] and sulfur monoxide (SO) molecules to analyze the motion and temperature of the gas around the baby star.

L1527 is a well-known protostar (baby star) and many astronomers have pointed telescopes at it. For example, NASA’s Spitzer Space Telescope took infrared images of the star. The stellar light escapes through a cavity excavated by a powerful bipolar gas flow from the star and illuminates the surrounding gas, which makes a butterfly-shaped nebula extending in the east-west direction (Figure 1). Past radio observations revealed that gas is circling around the star to form a disk and we see the disk edge-on.

Radio observations by ALMA have the advantage of being able to see the gas directly, which is invisible in infrared light. Various molecules in the gas emit characteristic radiation as radio waves under characteristic conditions (temperature, density, chemical compositions). Therefore astronomers can investigate the nature of the gas by observing various molecules.

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ALMA Discovers Large “Hot” Cocoon Around A Small Baby Star

October 8, 2013 Leave a comment

Artist impression. Credit: NAOJ

Artist impression. Credit: NAOJ

A large hot molecular cloud around a very young star was discovered by ALMA. This hot cloud is about ten times larger than those found around typical solar-mass baby stars, which indicates that the star formation process has more diversity than ever thought. This result was published in the Astrophysical Journal Letters on September 20th, 2013.

Stars are formed in very cold (-260 degrees Celsius) gas and dust clouds. Infrared Dark Clouds (IRDC) are dense regions of such clouds, and thought that in which clusters of stars are formed. Since most of stars are born as members of star clusters, investigating IRDCs has a crucial role in comprehensive understanding the star formation process.

A baby star is surrounded by the natal gas and dust cloud, and the cloud is warmed up from its center. Temperature of the central part of some, but not all, of such clouds reaches as high as -160 degrees Celsius. Astronomers call those clouds as “hot core” – it may not be hot on the Earth, but is hot enough for a cosmic cloud. Inside hot cores, various molecules, originally trapped in the ice mantle around dust particles, are sublimated. Organic molecules such as methanol (CH3OH), ethyl cyanide (CH3CH2CN), and methyl formate (HCOOCH3) are abundant in hot cores.

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New Theory Points To ‘Zombie Vortices’ As Key Step In Star Formation

August 21, 2013 Leave a comment

Artist conception. Image courtesy of NASA/JPL-Caltech

Artist conception. Image courtesy of NASA/JPL-Caltech

A new theory by fluid dynamics experts at the University of California, Berkeley, shows how “zombie vortices” help lead to the birth of a new star.

Reporting today (Tuesday, Aug. 20) in the journal Physical Review Letters, a team led by computational physicist Philip Marcus shows how variations in gas density lead to instability, which then generates the whirlpool-like vortices needed for stars to form.

Astronomers accept that in the first steps of a new star’s birth, dense clouds of gas collapse into clumps that, with the aid of angular momentum, spin into one or more Frisbee-like disks where a protostar starts to form. But for the protostar to grow bigger, the spinning disk needs to lose some of its angular momentum so that the gas can slow down and spiral inward onto the protostar. Once the protostar gains enough mass, it can kick off nuclear fusion.

Full Story: http://newscenter.berkeley.edu/2013/08/20/zombie-vortices-key-step-in-star-formation/

SOFIA Observations Reveal A Surprise In Massive Star Formation


Researchers using the airborne Stratospheric Observatory for Infrared Astronomy (SOFIA) have captured the most detailed mid-infrared images yet of a massive star condensing within a dense cocoon of dust and gas.

The star is G35.20-0.74, more commonly known as G35. It is one of the most massive known protostars and is located relatively close to Earth at a distance of 8,000 light years.

Until now, scientists expected the formation process of massive stars would be complicated by the turbulent, chaotic environments in the centers of new star clusters where they form. But observations of G35 suggest this giant star, more than 20 times the mass of our sun, is forming by the same orderly process as do stars with the same mass as the sun. Stars most like the sun are understood to form by simple, symmetric collapse of interstellar clouds.

Full Story: http://www.sofia.usra.edu/News/news_2013/04_16_13/index.html

ALMA Detects Signs Of Star Formation Surprisingly Close To Galaxy’s Supermassive Black Hole


Credit: Yusef-Zadeh et al., ALMA (ESO, NAOJ, NRAO), NRAO/AUI/NSF

Credit: Yusef-Zadeh et al., ALMA (ESO, NAOJ, NRAO), NRAO/AUI/NSF

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have discovered signs of star formation perilously close to the supermassive black hole at the center of the Milky Way Galaxy. If confirmed, this would be the first time that star formation was observed so close to the galactic center.

The center of our galaxy, 27,000 light-years away in the direction of the constellation Sagittarius, is home to a monstrous black hole with a mass of four million suns. Extending outward from this gravitational behemoth for many light-years is a turbulent region of space that is thought to be wracked by such extreme tidal forces that any star-forming clouds of dust and gas would be stretched thin and shredded long before infant stars could emerge.

Yet against these extreme odds, ALMA spotted telltale jets of material bursting out of what appear to be dense cocoons of gas and dust. These jets, if they were observed in more placid surroundings, would indicate the formation of a young star. The results were accepted for publication in the Astrophysical Journal Letters.

Full Story: http://www.nrao.edu/pr/2013/protostar/

Herschel Discovers Some Of The Youngest Stars Ever Seen


Astronomers have found some of the youngest stars ever seen, thanks to the Herschel space observatory, a European Space Agency mission with important NASA contributions.

Observations from NASA’s Spitzer Space Telescope and the Atacama Pathfinder Experiment (APEX) telescope in Chile, a collaboration involving the Max Planck Institute for Radio Astronomy in Germany, the Onsala Space Observatory in Sweden, and the European Southern Observatory in Germany, contributed to the findings.

Dense envelopes of gas and dust surround the fledging stars known as protostars, making their detection difficult. The 15 newly observed protostars turned up by surprise in a survey of the biggest site of star formation near our solar system, located in the constellation Orion. The discovery gives scientists a peek into one of the earliest and least understood phases of star formation.

“Herschel has revealed the largest ensemble of such young stars in a single star-forming region,” said Amelia Stutz, lead author of a paper to be published in The Astrophysical Journal and a postdoctoral researcher at the Max Planck Institute for Astronomy in Heidelberg, Germany. “With these results, we are getting closer to witnessing the moment when a star begins to form.”

Full Story: http://www.jpl.nasa.gov/news/news.php?release=2013-102