* Astronomy

Hidden Secrets of Orion's Clouds

This spectacular new image is one of the largest near-infrared high-resolution mosaics of the Orion A molecular cloud, the nearest known massive star factory, lying about 1350 light-years from Earth. It was taken using the VISTA infrared survey telescope at ESO's Paranal Observatory in northern Chile and reveals many young stars and other objects normally buried deep inside the dusty clouds.
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Orions Fingers: New Clarity on an Explosive Outflow

The Orion Nebula, probably the most well-known deep sky object in the night sky, also offers rare glimpses into catastrophic episodes in the lives of stars. Widespread, high-velocity outflow points to an explosive origin of the region known as the "Orion Fingers." With new observations using adaptive optics imaging from Gemini South, John Bally of the University of Colorado and colleagues find over 120 high-velocity outflows in this region. Direct comparisons with earlier observations reveal the motion of these fingers. Measurements of their properties, and comparison with simulations, are evidence that an explosive event drives the outflows, which may be connected to the birth of "runaway," massive stars.
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Title: Young Stellar Objects in Lynds 1641: Disks, Accretion, and Star Formation History
Authors: Min Fang, Jinyoung Serena Kim, Roy van Boekel, Aurora Sicilia-Aguilar, Thomas Henning, Kevin Flaherty

We investigate the young stellar objects (YSOs) in the Lynds~1641 (L1641) cloud using multi-wavelength data including Spitzer, WISE, 2MASS, and XMM covering ~1390 YSOs across a range of evolutionary stages. In addition, we targeted a sub-sample of YSOs for optical spectroscopy. We use this data, along with archival photometric data, to derive spectral types, extinction values, masses, ages, as well as accretion rates. We obtain a disk fraction of ~50% in L1641. The disk frequency is almost constant as a function of stellar mass with a slight peak at log(M_*/M_sun)\approx-0.25. The analysis of multi-epoch spectroscopic data indicates that the accretion variability of YSOs cannot explain the two orders of magnitude of scatter for YSOs with similar masses. Forty-six new transition disk (TD) objects are confirmed in this work, and we find that the fraction of accreting TDs is lower than for optically thick disks (40--45% vs. 77--79% respectively). We confirm our previous result that the accreting TDs have a similar median accretion rate to normal optically thick disks. We confirm that two star formation modes (isolated vs. clustered) exist in L1641. We find that the diskless YSOs are statistically older than the YSOs with optically-thick disks and the transition disk objects have a median age which is intermediate between the two populations. We tentatively study the star formation history in L1641 based on the age distribution and find that star formation started to be active 2--3 Myr ago.

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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.
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.
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