WR22: a star in question

The Carina Nebula is known for being one of the largest nurseries of massive stars in our Galaxy. Amongst the stellar wildlife which populates the Carina, it is WR22 which holds the particular attention of the ULg’s High Energy Astrophysics Group (GAPHE). A star which has kept many surprises in store for the astronomers.

A genuine jewel of the Southern skies, the majestic Carina Nebula, alias NGC 3372 for the professionals, stretches over 300 light years. The region is sculpted with numerous filaments of gas and clouds of dust. Like the famous Orion nebula in the Northern skies, the Carina Nebula is the delight of young and old astronomers because it is already easily visible to the naked eye, despite the 7,500 to 8,500 light years which separate us from it. It is thus over five times further away from us than Orion.


If the Carina Nebula is a target for amateur astronomers always on the hunt for the most beautiful photos, it is also much sought after by the world’s largest telescopes which usher us into the intimacy of stars being formed. In effect this region is known for being one of the largest nurseries of stars in our Galaxy. It is home to numerous young and massive stars, such as the famous and unique η Carinae, whose mass it is thought to be over 100 times that of the Sun (concerning the study of the stellar winds of Carinae, read the article Collisions between solar winds).

Carinae starMassive stars are of interest because their mass leads them to take an evolutionary path very different from that taken by more common stars, such as our Sun. At the beginning they collapse on themselves under the effect of their own gravity, as do all the other stars, but the temperatures reached within their centres are a lot greater, leading to a rapid rise of nuclear reactions and an accelerated evolution. Moreover, to expel the energy stored within its core, a massive star emits large quantities of photons which are so energetic that they throw out the star’s external layers in the form of winds which can reach speeds of 2000 km/s, or even more. These winds correspond to a very high rate of mass loss and to an enriching of the interstellar environment of heavy elements formed within the star…whilst stars of low mass lose practically no material in the form of winds.

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