In this new image, the NASA/ESA Hubble Space Telescope has captured the brilliance of NGC 362, a globular star cluster located approximately 27,000 light-years away in the constellation Tucana.
This image from the NASA/ESA Hubble Space Telescope shows the globular cluster NGC 362. Image credit: NASA / ESA / Hubble.
Globular clusters offer some of the most spectacular sights in the night sky. The word ‘globulus,’ from which these clusters take their name, is Latin for small sphere.
These objects typically contain 100,000 to 10 million stars packed in a region 100 light-years in diameter, and are the best example of a ‘simple’ stellar population, i.e. a group of stars with the same age and chemical composition.
The stars that compose globular clusters all orbit the cluster center, occasionally interacting, gravitationally, with a close-passing star. The orbits of these stars are typically not as circular as the orbits of planets in our Solar System.
Globular clusters are fairly clean of interstellar gases. Many of them have a core containing a group of unusually young and massive stars called blue stragglers.
These clusters once ruled our Milky Way Galaxy. Back in the old days, back when the Milky Way first formed, perhaps thousands of globular clusters roamed the Galaxy.
Many globular clusters were destroyed by repeated fateful encounters with each other or the Milky Way’s center.
Today, there are around 180 left — and the one shown in this Hubble image, NGC 362, is one of the more unusual ones.
As stars make their way through life they fuse elements together in their cores, creating heavier and heavier elements — known in astronomy as metals — in the process. When these stars die, they flood their surroundings with the material they have formed during their lifetimes, enriching the interstellar medium with metals.
Stars that form later therefore contain higher proportions of metals than their older relatives.
By studying the different elements present within individual stars in NGC 362, astronomers discovered that the cluster boasts a surprisingly high metal content, indicating that it is younger than expected.
Although most globular clusters are very ancient objects formed around the same time as their host galaxy, NGC 362 bucks the trend, with an age lying between 10 and 11 billion years old.
This image of NGC 362 is a composite of separate exposures acquired by Hubble’s Advanced Camera for Surveys (ACS). Three filters — a blue filter (F435W) and two red filters (F625W and F658N) — were used to sample various wavelengths.
