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Theta 1 Orionis C
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Title: Optical interferometric observations of Theta 1 Orionis C from NPOI and implications for the system orbit
Authors: J. Patience (1), R. T. Zavala (2), L. Prato (3), O. Franz (3), L. Wasserman (3), C. Tycner (4), D. J. Hutter (2), C. A. Hummel (5) ((1) University of Exeter, (2) U.S. Naval Observatory, Flagstaff Station, (3) Lowell Observatory, (4) Central Michigan, (5) European Southern Observatory)

With the Navy Prototype Optical Interferometer (NPOI), the binary system Theta 1 Orionis C, the most massive member of the Trapezium, was spatially resolved over a time period extending from February 2006 to March 2007. The data show significant orbital motion over the 14 months, and, after combining the NPOI data with previous measurements of the system from the literature, the observations span 10 years of the orbit. Our results indicate that the secondary did not experience an unusually close periastron passage this year, in contradiction to the prediction of a recently published, highly eccentric ~11 year orbit. Future observations of this source will be required to improve the orbital solution. Possible implications of the results in terms of system distance are discussed, although a main conclusion of this work is that a definitive orbit solution will require more time to obtain sufficient phase coverage, and that the interaction effects expected at periastron did not occur in 2007.

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RE: Orion Nebula
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The Orion nebula with its hot gas bubble
The Orion nebula

Right in time for the festive season, ESA's XMM-Newton X-ray observatory has discovered a huge cloud of high-temperature gas resting in a spectacular nearby star-forming region, shaped somewhat like the silhouette of Santa Claus.
An early present for astronomers, the cloud suggests that hot gas from many star-forming regions leaks into the interstellar medium. The Orion nebula is the nearest dense star-forming region to Earth that contains stars much more massive than the Sun.
XMM-Newtons newly-discovered gas cloud is composed of winds blowing from these high-mass stars that are heated to millions of degrees as they slam into the surrounding gas.

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Stars in our galaxy may often pump out waves of million-degree gas that make surrounding nebulas glow with X-rays.
These new findings could shed light into how planetary systems form including our own solar system, researchers said.
Astrophysicists focused on the Orion Nebula, a cloud of dense and turbulent gas visible to the naked eye in the night sky, right below the belt of the constellation Orion. Four extremely bright and massive stars, called the Trapezium, light up the nebula.

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You'd think astronomers would have all the key stats on the Orion Nebula (Messier 42) by now. Visible to the unaided eye, this deep-sky showpiece was first studied with a spectroscope in 1864 and first photographed in 1880. It's the first thing many people look at with their first telescope, and the last that William Herschel wanted to see with his last. The nebula has been studied at all wavelengths, harbours many variable stars, and is home to the Trapezium, the best-known multiple star in the sky.

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Using the supersharp radio "vision" of the National Science Foundation's Very Long Baseline Array (VLBA), astronomers have made the most precise measurement ever of the distance to a famous star-forming region. The measurement -- to the heavily studied Orion Nebula -- changes scientists' understanding of the characteristics of the young stars in the region.

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The widely photographed and heavily studied Orion Nebula is nearly 300 light-years closer to Earth than previously thought, according to a new study.
The finding, detailed in the Oct. 10 issue of Astrophysical Journal, also hikes up the age of the nebula's stellar inhabitants.

"These stars are nearly twice as old as previously thought" - study team member Geoff Bower, an astronomer at the University of California, Berkeley.

The new measurements were made using the National Science Foundation's Very Long Baseline Array (VLBA). The scientists determined the distance to a star called GMR A, one of a cluster of stars in the Orion Nebula, by measuring the slight shift in the star's apparent position while the Earth was on opposite sides of its annual orbit around the sun.
This technique, called parallax, allows astronomers to measure the angle of an object's small shift in position and to calculate its distance.

"This measurement is four times more precise than previous distance measurements" - Geoff Bower.

The new VLBA measurements shorten the Orion Nebula's distance from 1,565 to 1,270 light-years away.

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Orion Nebula
Credit: X-ray: NASA/CXC/Penn State/E.Feigelson & K.Getman et al.; Optical: NASA/ESA/STScI/M. Robberto et al.
JPEG (379.9 kb) Tiff (7.1 MB) PS (6 MB)

At a distance of about 1,500 light years, the Orion Nebula is one of the closest star formation regions to Earth. This makes Orion - a favourite for amateur astronomers and casual sky watchers - an excellent location to study how stars are born and behave during their stellar childhoods. In this composite image, the central region of Orion is seen as never before through NASA's Chandra X-ray Observatory and the Hubble Space Telescope.

Coordinates (J2000) RA 05h 35m 16.60s | Dec -05d 23m 20.42s


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Title: The distance to the Orion Nebula
Authors: K. M. Menten (1), M. J. Reid (2), J. Forbrich (1,2), A. Brunthaler (1) ((1) MPIfR, (2) CfA)

We have used the Very Long Baseline Array to measure the trigonometric parallax of several member stars of the Orion Nebula Cluster showing non-thermal radio emission. We have determined the distance to the cluster to be 414 7 pc. Our distance determination allows for an improved calibration of luminosities and ages of young stars. We have also measured the proper motions of four cluster stars which, when accurate radial velocities are measured, will put strong constraints on the origin of the cluster.

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An image released today by the Gemini Observatory brings into focus a new and remarkably detailed view of supersonic "bullets" of gas and the wakes created as they pierce through clouds of molecular hydrogen in the Orion Nebula. The image was made possible with new laser guide star adaptive optics technology that corrects in real time for image distortions caused by Earth's atmosphere.

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Bullet-like clumps of gas hurtle through the Orion stellar nursery at supersonic speed in a new image from the Gemini North observatory. The unusual structures are revealed in unprecedented detail by newly commissioned laser-equipped optics.
The so-called 'bullets' are located in the Orion Nebula, a star-forming region about 1500 light years from Earth. Each of the few dozen observed is a dense clump of gas about as wide as Pluto's orbit around the Sun.
Tearing through the surrounding medium of thin gas at 400 kilometres per second, the bullets create shock waves in front of them. As the shock waves propagate, they produce lengthy glowing trails each about 400 times longer than our entire solar system.
Based on the length of the trails and the bullets' speed, the bullets appear to have formed simultaneously less than 1000 years ago.
Exactly what triggered their birth is unknown. But they may be related to a nearby, bright source of infrared light thought to be a moderately heavy star that is partially obscured by dust.

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Orion Nebula00
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Credit: Gemini Observatory

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Title: Large Scale Flows from Orion-South
Authors: W. J. Henney, C. R. O'Dell, Luis A. Zapata, Ma. T. Garcia-Diaz, Luis F. Rodriguez, Massimo Robberto

Multiple optical outflows are known to exist in the vicinity of the active star formation region called Orion-South (Orion-S). We have mapped the velocity of low ionisation features in the brightest part of the Orion Nebula, including Orion-S, and imaged the entire nebula with the Hubble Space Telescope. These new data, combined with recent high resolution radio maps of outflows from the Orion-S region, allow us to trace the origin of the optical outflows. It is confirmed that HH 625 arises from the blueshifted lobe of the CO outflow from 136-359 in Orion-S while it is likely that HH 507 arises from the blueshifted lobe of the SiO outflow from the nearby source 135-356. It is likely that redshifted lobes are deflected within the photon dominated region behind the optical nebula. This leads to a possible identification of a new large shock to the southwest from Orion-S as being driven by the redshifted CO outflow arising from 137-408. The distant object HH 400 is seen to have two even further components and these all are probably linked to either HH 203, HH 204, or HH 528. Distant shocks on the west side of the nebula may be related to HH 269. The sources of multiple bright blueshifted Herbig-Haro objects (HH 202, HH 203, HH 204, HH 269, HH 528) remain unidentified, in spite of earlier claimed identifications. Some of this lack of identification may arise from the fact that deflection in radial velocity can also produce a change in direction in the plane of the sky. The best way to resolve this open question is through improved tangential velocities of low ionisation features arising where the outflows first break out into the ionised nebula.

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