Archive for Orion

A new observational basis for star formation studies in Orion

Posted in astronomy with tags , , on March 8, 2016 by Tim Kendall


A new paper entitled “VISION – Vienna Survey in Orion. I. VISTA Orion A Survey” is the first looking at the closest region of massive star formation – Orion. At the moment the complete paper by S. Meingast, J. Alves, D. Mardones, et al. (2016) is available here:

The Orion nebula cluster (ONC), the nearest region of massive star formation, is embedded in the much larger Orion A molecular cloud. The ONC has been studied much more extensively than other parts of Orion A, in spite of the opportunity that this region offers to understand the processes connected with the formation of both low- and high-mass stars. Using the ESO Visible and Infrared Survey Telescope for Astronomy (VISTA), the authors have surveyed the entire Orion A molecular cloud in the J, H, and K (short) near-infrared bands, covering a total of around 18.3 square degrees, and present the most detailed and sensitive near-infrared (NIR) observations of the entire molecular cloud to date. They find about 2500 embedded objects in Orion A and confirm the existence of a recently discovered foreground population above the Galactic field. The Orion A VISTA catalog contains 799 995 sources, which increases the source counts by about an order of magnitude compared to the 2MASS survey. It provides a basis for future studies of star formation processes toward Orion.


The Herschel view of the heart of Orion

Posted in astronomy with tags , , , on August 27, 2013 by Tim Kendall


Image: ESA/Herschel/ Ph. André, V. Könyves, N. Schneider (CEA Saclay, France) for the Gould Belt survey Key Program. The image is a composite of the wavelengths of 70 microns (blue), 160 microns (green) and 250 microns (red) and spans about 1.3 x 2.4 degrees. North is up and east is to the left. In this view, the nebula corresponds to the brightest region in the center of the image, where it is lit up by the Trapezium group of stars at its heart. Embedded within the red and yellow filaments are a handful of point-like sources: these are protostars, the seeds of new stars that will soon ignite and begin to flood their surrounds with intense radiation.


This colour-composite image of IC 5146 shows the extended filamentary structure of this star-forming cloud. A detailed study of this complex has shown a total of 27 filaments that all appear to have very similar widths, with a value of about 0.3 light years. The glowing cavity at the top of the image, also known as the Cocoon Nebula, is an HII region, where a young and bright B0 star illuminates the ionised hydrogen gas, causing it to shine. Some young stellar objects are visible as bright spots along the main filaments; many other young stellar objects are located in the Cocoon Nebula but are not visible in this image.

The Orion Nebula from Spitzer

Posted in astronomy with tags , , on May 23, 2013 by Tim Kendall

A colony of hot, young stars is stirring up the cosmic scene in this new picture from NASA's Spitzer Space Telescope.
Image credit: NASA/JPL/California Institute of Technology

I have looked at Orion in many recent posts. The Orion molecular cloud complex extends several degrees on the sky roughly centred on M42 and M43, shown in the main image. The complex contains many other well-known objects including M78, the Flame Nebula, and the famous Becklin-Neugebauer object, a protostar and one of the first finds of infrared astronomy, detected in 1966. The location on the sky of the three Messier objects is shown (left), as is the young O9.5V star sigma Orionis, which is associated with a young cluster known for containing planetary mass objects. The star itself is now known to be photoevaporating a nearby (1200 AU) dust cloud.

Orion in a new, submillimeter light

Posted in astronomy with tags , on May 15, 2013 by Tim Kendall

Image credit: ESO/Digitized Sky Survey 2

This dramatic new image of cosmic clouds in the constellation of Orion reveals what seems to be a fiery ribbon in the sky. The large bright region at top is the familiar Orion Nebula, M42. This orange glow represents faint light coming from grains of cold interstellar dust, at wavelengths too long for human eyes to see. It was observed by the ESO-operated Atacama Pathfinder Experiment (APEX) in Chile.

Clouds of gas and interstellar dust are the raw materials from which stars are made. But these tiny dust grains block our view of what lies within and behind the clouds — at least at visible wavelengths — making it difficult to observe the processes of star formation. This is why astronomers need to use instruments that are able to see at other wavelengths of light. At submillimetre wavelengths, rather than blocking light, the dust grains shine due to their temperatures of a few tens of degrees above absolute zero. A cloud of dust with a temperature of only ten degrees Kelvin has its peak of emission at around 0.3 millimetres — in the part of the spectrum where APEX is very sensitive. The APEX telescope with its submillimetre-wavelength camera LABOCA, located at an altitude of 5000 metres above sea level on the Chajnantor Plateau in the Chilean Andes, is the ideal tool for this kind of observation. The dust clouds form beautiful filaments, sheets, and bubbles as a result of processes including gravitational collapse and the effects of stellar winds. These winds are streams of gas ejected from the atmospheres of stars, which are powerful enough to shape the surrounding clouds into the convoluted forms seen here.

The research paper is “A Herschel and APEX Census of the Reddest Sources in Orion: Searching for the Youngest Protostars” by A. Stutz et al., ApJ 767, 36 (2013) [ESO pdf]. For more on the young protostars in the Orion molecular cloud see here.