esahubble_potw1303a January 21st, 2013
Credit: ESA/Hubble & NASA
Globular clusters are roughly spherical collections of extremely old stars, and around 150 of them are scattered around our galaxy. Hubble is one of the best telescopes for studying these, as its extremely high resolution lets astronomers see individual stars, even in the crowded core. The clusters all look very similar, and in Hubbles images it can be quite hard to tell them apart and they all look much like NGC 411, pictured here. And yet appearances can be deceptive: NGC 411 is in fact not a globular cluster, and its stars are not old. It isnt even in the Milky Way. NGC 411 is classified as an open cluster. Less tightly bound than a globular cluster, the stars in open clusters tend to drift apart over time as they age, whereas globulars have survived for well over 10 billion years of galactic history. NGC 411 is a relative youngster not much more than a tenth of this age. Far from being a relic of the early years of the Universe, the stars in NGC 411 are in fact a fraction of the age of the Sun. The stars in NGC 411 are all roughly the same age, having formed in one go from one cloud of gas. But they are not all the same size. Hubbles image shows a wide range of colours and brightnesses in the clusters stars. These tell astronomers many facts about the stars, including their mass, temperature and evolutionary phase. Blue stars, for instance, have higher surface temperatures than red ones. The image is a composite produced from ultraviolet, visible and infrared observations made by Hubbles Wide Field Camera 3. This filter set lets the telescope see colours slightly further beyond red and the violet ends of the spectrum.
Provider: Hubble Space Telescope | ESA
Image Source: https://www.spacetelescope.org/images/potw1303a/
Curator: ESA/Hubble, Garching bei München, Germany
Image Use Policy: Creative Commons Attribution 4.0 International License
Detailed color mapping information coming soon...
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