Hidden secrets of Orion's clouds

The new image from the VISION survey (VIenna Survey In Orion) is a montage of images taken in the near-infrared part of the spectrum [1] by the VISTA survey telescope at ESO's Paranal Observatory in Chile. It covers the whole of the Orion A molecular cloud, one of the two giant molecular clouds in the Orion molecular cloud complex (OMC). Orion A extends for approximately eight degrees to the south of the familiar part of Orion known as the sword [2].

VISTA is the world's largest dedicated survey telescope, and has a large field of view imaged with very sensitive infrared detectors, characteristics that made it ideal for obtaining the deep, high-quality infrared images required by this ambitious survey.

The VISION survey has resulted in a catalogue containing almost 800,000 individually identified stars, young stellar objects and distant galaxies, This represents better depth and coverage than any other survey of this region to date [3].

VISTA can see light that the human eye cannot, allowing astronomers to identify many otherwise hidden objects in the stellar nursery. Very young stars that cannot be seen in visible-light images are revealed when observed at longer infrared wavelengths, where the dust that shrouds them is more transparent.

The new image represents a step towards a complete picture of the star formation processes in Orion A, for both low and high mass stars. The most spectacular object is the glorious Orion Nebula, also called Messier 42 [4] seen towards the left of the image. This region forms part of the sword of the famous bright constellation of Orion (The Hunter)(constellation). The VISTA catalogue covers both familiar objects and new discoveries. These include five new young stellar object candidates and ten candidate galaxy clusters.

Elsewhere in the image, we can look into Orion A's dark molecular clouds and spot many hidden treasures, including discs of material that could give birth to new stars (pre-stellar discs), nebulosity associated with newly-born stars (Herbig-Haro objects), smaller star clusters and even galaxy clusters lying far beyond the Milky Way. The VISION survey allows the earliest evolutionary phases of young stars within nearby molecular clouds to be systematically studied.

This impressively detailed image of Orion A establishes a new observational foundation for further studies of star and cluster formation and once again highlights the power of the VISTA telescope to image wide areas of sky quickly and deeply in the near-infrared part of the spectrum [5].

Notes

[1] The VISION survey covers approximately 18.3 square degrees at a scale of about one-third of an arcsecond per pixel.

[2] The other giant molecular cloud in the Orion Molecular Cloud is Orion B, which lies east of Orion's Belt.

[3] The complete VISION survey includes an even larger region than is shown in this picture, which covers 39 578 x 23 069 pixels.

[4] The Orion nebula was first described in the early seventeenth century although the identity of the discoverer is uncertain. The French comet-hunter Messier made an accurate sketch of its main features in the mid-eighteenth century and gave it the number 42 in his famous catalogue. He also allocated the number 43 to the smaller detached region just north of the main part of the nebula. Later William Herschel speculated that the nebula might be "the chaotic material of future suns" and astronomers have since discovered that the mist is indeed gas glowing in the fierce ultraviolet light from young hot stars that have recently formed there.

[5] The successful VISION survey of Orion will be followed by a new, bigger public survey of other star-forming regions with VISTA, called VISIONS, which will start in April 2017.