Each week, researchers from the Hubble Space Telescope they share an image they have captured of a particular object or region in space. This week’s Hubble image shows the Small Magellanic Cloudor SMC, which is a satellite galaxy of our Milky Way.
The SMC is small compared to our galaxy, only 7,000 light-years across compared to the Milky Way’s roughly 100,000 light-years, making it a type called a dwarf galaxy. It is also one of our closest neighbors and a satellite galaxy of the Milky Way, which means that it is gravitationally bound to our galaxy. It can be seen with the naked eye, along with its companion the Large Magellanic Cloud, mostly visible from the southern hemisphere.
This image is only a small part of the SMC. “The Small Magellanic Cloud contains hundreds of millions of stars, but this image focuses on only a small fraction of them,” they write Hubble scientists. “These stars comprise the open cluster NGC 376, which has a total mass only about 3,400 times that of the Sun. Open clusters, as their name suggests, are loosely knit and sparsely populated.”
The SMC was the site of one of the most important discoveries in the history of astronomy, as pioneer Henrietta Leavitt observed a type of variable star called a Cepheid variable there. Leavitt showed that these stars have an established relationship between how bright they shine and how often they pulsate, allowing researchers to tell how bright a star would be based on its pulse. By comparing the luminosity of a Cepheid variable to its observed brightness, researchers can tell precisely how far away it is. This means that these stars can be used as distance markers, allowing astronomers to measure distances in the universe.
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