Small Magellanic Cloud
Galaxy · Satellite of the Milky Way
The Small Magellanic Cloud is a dwarf galaxy orbiting the Milky Way. It is famous because studying its stars gave astronomers a way to measure the size of the universe.
- 200,000 light-years awayEven light – the fastest thing there is – needs 200,000 years to get here.
- Dwarf irregularType
- The cosmic measuring tapeFamous for
Take a closer look
A Pinch of Heavy Elements
The Small Magellanic Cloud’s stars contain only about a fifth as much of the heavier elements – like oxygen and iron – as our Sun. That makes it a handy window into the past, because galaxies in the early universe were also short of these ingredients.
Pulled Like Taffy
The SMC is being tugged by both the Large Magellanic Cloud and the Milky Way. Their gravity has pulled out a long bridge of gas and stars – the Magellanic Bridge – that links the two Clouds, and a huge trail of gas that streams behind them across the sky.
Webb Finds Planet Nurseries
In the SMC’s busy star cluster NGC 346, the James Webb Space Telescope spotted young stars still wrapped in dusty discs that can build planets – even though the galaxy has so few heavy elements. Puzzlingly, these discs seem to last longer than similar ones in our own galaxy.
How we found out
- 1908–1912
Henrietta Swan Leavitt, studying photographic plates at Harvard, finds that Cepheid variable stars in the SMC that pulse more slowly are brighter.
- 1913
Ejnar Hertzsprung uses her discovery to estimate the distance to the SMC.
- 1920s
Edwin Hubble uses Leavitt’s law to measure the distance to Andromeda – and other galaxies.
How can you tell how far away a light is?
If you know how bright it really is, you can compare it to how bright it looks. Leavitt’s Cepheids are “standard candles” with a known real brightness.
See it yourself
From the Southern Hemisphere: a smaller misty patch near the bright star Achernar.
From the encyclopedia
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