Cosmic watercolour

R Corona Australis nebula

The R Corona Australis nebula is a complex mix of gas and dust 420 light-years from Earth, where young stars are beginning their lives.

  • R Corona Australis starbirth region
  • 420 light-years from Earth
  • Gas glows blue from reflected starlight

This magnificent view of the region around the star R Coronae Australis was created from images taken with the Wide Field Imager (WFI) at the European Southern Observatory’s (ESO) La Silla Observatory in Chile.

R Coronae Australis lies at the heart of a nearby star-forming region and is surrounded by a delicate bluish “reflection” nebula embedded in a huge dust cloud.

The new image—a combination of twelve separate pictures taken through red, green and blue filters—reveals surprising new details in this dramatic area of sky, which spans roughly the width of the full Moon.

The nebula is located some 420 light-years away in the small constellation of Corona Australis (the Southern Crown). The complex is named after the star R Coronae Australis, which lies at the centre of the image. It is one of several stars in this region that belong to the class of very young stars that vary in brightness and are still surrounded by the clouds of gas and dust from which they formed.

See the full-size version of the image here (new window).

Colours of the night

The intense radiation given off by these hot young stars interacts with the gas surrounding them and is either reflected or re-emitted at a different wavelength.

These complex processes, determined by the physics of interstellar gas and the properties of the stars, are responsible for the magnificent colours of nebulae. The light blue nebulosity seen in this picture is mostly due to the reflection of starlight off small dust particles.

The young stars in the R Coronae Australis complex are similar in mass to the Sun and do not emit enough ultraviolet light to ionise a substantial fraction of the surrounding hydrogen. This means that the cloud does not glow with the characteristic pink colour seen in many star-forming regions.

The image below shows a wider view of the R Corona Australis region. See the full-size version here (new window).

R Corona Australis nebula

A wider view of the R Corona Australis region. A globular star cluster, NGC 6723, is just above and to the right.

A prominent dark “lane” crosses the image from the centre to the bottom left. Here the visible light emitted by the stars that are forming inside the cloud is completely absorbed by the dust. These stars could only be detected by observing at longer wavelengths, by using a camera that can detect infrared radiation.

Adapted from information issued by ESO.

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