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Wolf in sheep’s clothing

The Crescent Nebula

The Crescent Nebula, a huge cloud of gas illuminated from within by the intense radiation of a Wolf-Rayet star.

THIS IMAGE OF the Crescent Nebula or NGC 6888 was obtained using the Wide Field Camera on the Isaac Newton Telescope in the Canary Islands.

The Crescent Nebula is a cloud of gas illuminated by a central, massive Wolf-Rayet star, WR 136, whose intense outpouring of ultraviolet radiation is responsible for heating and ionising most of the gas ejected by the star earlier in its life.

Strong winds blown by WR 136 are interacting with the previously expelled material and as a result, the nebula shows a complex structure which resembles a crescent red Moon.

The image is a three-colour composite made from data collected using filters to isolate the light emitted by hydrogen alpha (H-alpha) and doubly ionised oxygen (OIII) atoms, and coded in the image as red, green (25% H-alpha and 75% OIII) and blue.

You can see the full-size, high-resolution image here (will open in a new window or tab)

Information courtesy IAC. Image obtained and processed by members of the IAC astrophotography group—A. Oscoz, D. López, P. Rodríguez-Gil and L. Chinarro.

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Hot star: don’t get too close!

WR 22 and the Carina Nebula

The hot, massive, young star in the centre of this image is WR 22, a member of the rare class of Wolf–Rayet stars, seen against the backdrop of the Carina Nebula. At the distance of the nebula, this image covers an area of 72 x 72 light-years.

A spectacular new image from the European Southern Observatory’s (ESO) Wide Field Imager at the La Silla Observatory in Chile shows the brilliant and unusual star WR 22 and its colourful surroundings.

WR 22 is a very hot and bright star that is shedding its atmosphere into space at a rate many millions of times faster than the Sun. It is located in the outer part of the dramatic Carina Nebula, a huge cloud of gas and dust from which it and many other stars formed.

Very massive stars live fast and die young. Some of them have such intense radiation passing through their thick atmospheres late in their lives that they shed gas into space many millions of times more quickly than relatively sedate stars such as our Sun.

These rare, very hot and massive objects are known as Wolf–Rayet stars, after the two French astronomers who first identified them in the mid-nineteenth century. Wolf-Rayet stars typically have surface temperatures between 25,000 and 50,000 degress Celsius. (The Sun’s surface temperature is only 5,500 degrees.)

WR 22 is one of the most massive examples yet measured, is one of many exceptionally brilliant stars associated with the beautiful Carina Nebula (also known as NGC 3372) in the southern Milky Way. The outer part of this huge region of star formation forms the colourful backdrop to this image.

See the full-size, high-resolution image here (0.7MB, will open in a new window)

The central part of nebula lies off to the left of WR 22, and can be seen in the wider view below.

A wider view of the Carina Nebula

A wider view of the Carina Nebula, showing WR 22 at right and a bright conglomeration at left that hides another huge and famous star, Eta Carinae.

See the full-size, high-resolution version of the wide-field image here (0.7MB, will open in a new window)

The subtle colours of the nebula are a result of the interactions between the intense ultraviolet radiation coming from hot massive stars, including WR 22, and the vast gas clouds, mostly hydrogen, from which they formed.

WR 22 is a part of a binary star system and has been measured to have a mass at least 70 times that of the Sun. Although it is over 5,000 light-years from Earth, it is so bright that it can just be faintly seen with the unaided eye under good conditions.

Adapted from information issued by ESO.

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