Triangulum Galaxy (M33)
Galaxy · Spiral
The Triangulum Galaxy is the third-largest galaxy in our Local Group, after Andromeda and the Milky Way. It is a beautiful, loosely wound spiral, full of pink star-forming regions.
- 2.7 million light-years awayEven light – the fastest thing there is – needs 2.7 million years to get here.
- ~40 billionStars
- 3rd largest in the Local GroupRank
Take a closer look
No Bulge in the Middle
Unlike the Milky Way and Andromeda, Triangulum has no big bright bulge at its centre, and astronomers have found no sign of a giant black hole there. Instead it is rich in gas, which it is busily turning into fresh new stars along its loose, patchy arms.
Inside a Star Factory
Its star factory, NGC 604, is a glowing cloud so wide that light takes well over a thousand years to cross it – dozens of times wider than the Orion Nebula. More than 200 hot, blue, heavyweight stars blaze inside it, carving out huge bubbles in the gas.
Watching a Galaxy Turn
By tracking tiny radio beacons in its gas clouds over several years, astronomers measured Triangulum actually turning – and sliding slowly across our sky. It was one of the first times anyone measured a spiral galaxy’s sideways motion directly, a bit like timing a carousel from millions of light-years away.
How we found out
- Before 1654
Giovanni Battista Hodierna probably observes it first.
- 1764
Charles Messier catalogues it as M33.
- 2019
Hubble releases a huge, detailed mosaic of the galaxy.
What is the “Local Group”?
Our galaxy’s neighbourhood: the Milky Way, Andromeda, Triangulum and dozens of smaller dwarf galaxies, held together by gravity.
See it yourself
Binoculars from a dark site, near Andromeda.
From the encyclopedia
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