It’s a bird… it’s a plane… it’s a super star cluster! NASA’s Chandra X-ray telescope has imaged a star cluster that is “super” in every way. Westerlund 1 is super-big, super-massive, super-young, super-close — and it’s forming stars at a super-fast rate.
Westerlund 1 is about 13,000 light-years from Earth—which means it’s relatively close—and the 3- to 5-million-year-old star cluster is about 7 light-years across. If that age doesn’t seem too young to you, remember that our solar system’s average age is about 4.6 years billion years old. Westerlund 1 also has a mass equivalent to up to 100,000 suns and is one of the few remaining superstars in the Milky Way.
Studying Westerlund 1 could help astronomers better understand the inner workings of these cosmic star factories. The image is part of the first data released from the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS), led by astronomers at the Italian National Institute of Astrophysics in Palermo. As part of the EWOCS program, Chandra observed Westerlund 1 for a total of about 12 days.
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In its current epoch, the Milky Way produces very few stars, with only a handful of stellar bodies being formed each year. However, our galaxy wasn’t always so quiet. It used to produce many more stars; at its peak about 10 billion years ago, it gave birth to tens to hundreds of stars each year.
Astronomers believe that this intense star formation was mainly localized in super star clusters such as Westerlund 1. These are young star clusters with masses at least 10,000 times that of the Sun.
The X-rays from Westerlund 1 seen by Chandra, visible as pink and white in the image, come from young stars. Meanwhile, the pink, green and blue blobs represent diffuse heated gas throughout the supercluster.
The new Chandra data triple the number of known X-ray sources in Westerlund 1. Before the EWOCS project, Chandra detected 1,721 X-ray sources in the cluster; on the other hand, the EWOCS data revealed nearly 6,000 X-ray sources. These include faint stars with masses less than the mass of the Sun.
This gives astronomers a new population of stars to study in Westerlund 1. This means that the proximity of Westerlund 1 not only makes it a good target for studying star formation as a whole and decoding how such cluster environments affect planet birth, but the supercluster is also useful for studying of how stars with different masses evolve.
Chandra also found that the 1,075 stars it detected are crammed into a 4-light-year-wide region at the heart of Westerlund 1. To get an idea of ​​how dense this region is with stars, consider that there are 4.24 light-years between the Sun flight. and its nearest stellar neighbor, Proxima Centauri.
The more diffuse pink blob that dominates the Chandra image of Westerlund 1 represents the halo of hot gas at the center of the supercluster. Not only could this aspect of the region help provide a more accurate estimate of Westerlund 1’s mass, but it could also help assess how this particular collection of stars formed and how it has changed over time.
The EWOCS results are discussed in a paper published in February in the journal Astronomy and Astrophysics.