2023-08-15 14:01:03
If the Sun were there, there would be no nights on Earth. Such is the stellar density in the globular cluster NGC 6652, a spectacular ‘ball of stars’ recently photographed by the Hubble Space Telescope, that despite its seniority in space and the fact that James Webb has been taking center stage lately, it continues to sending us extraordinary images. If the Sun were there, in fact, in our sky the stars would be so close to each other that they would form a continuous tapestry of light, with no room or occasion for darkness.
At 30,000 light-years away, in the constellation Sagittarius, NGC 6652 is ‘only’ 6,500 light-years from the center of our galaxy and contains, according to a study published in 2020 in ‘Research in Astronomy and Astrophysics’some of the oldest stars in the entire Milky Way, and perhaps the entire Universe.
Globular clusters are dense spherical groupings of thousands (sometimes millions) of very old stars, with ages between 10,000 and 13,000 million years, that is, almost as old as the Universe (whose age is 13,760 million years). ). So far, astronomers have found about 150 such clusters in the halo around our galaxy, and they have also been observed around other neighboring galaxies. Their number seems related to the size of the galaxy they orbit, and studying them allows scientists to delve into the remote past of galaxies, and also into that of the Universe in general.
According to a recent study that appeared last May in ‘Astronomy and Astrophysics‘, globular clusters formed very early in the history of the Universe, just a few hundred million years after the Big Bang, and they did so around gigantic supermassive stars (thousands of times heavier than the Sun), but with very long lifetimes. short (barely a couple of million years). Stellar giants that could also have given rise to the first supermassive black holes, around which stars clustered to form the first galaxies.
The Hubble image shows a large number of pale blue stars along with more reddish ones that appear in the foreground. Of course, all of them very close together, forming a dense and compact sphere, the result of an intense gravitational attraction.
The spectacular new image is the result of the work of two different teams of scientists, who combined data from two of Hubble’s instruments: the Advanced Camera for Surveys and the Wide Field Camera 3. One of the teams was investigating the age of the globular clusters in the Milky Way, while the other tried to measure the amount of carbon, nitrogen and oxygen in clusters like NGC 6652, to better understand the composition of the stars it contains.
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