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Leo T

May 25, 2014

Our home galaxy, the Milky Way, belongs to the Local Group, a gathering of more than six dozen galaxies. Its largest members are the Andromeda galaxy and the Milky Way. Both of them are giants that give birth to new stars. Most other Local Group members, though, are faint dwarf galaxies, and most of them have run out of gas — the fuel for making new stars — so they won’t give birth to any more.

Recently, however, astronomers discovered a dwarf galaxy that’s still giving birth to new stars. It’s in the constellation Leo, which is high in the south and southwest at nightfall. Look for Regulus, the bright star that marks the lion’s heart.

Leo T is the dimmest galaxy yet seen that still gives birth to new stars. In fact, the entire galaxy has only a few hundred thousand stars — a far cry from the Milky Way, which boasts hundreds of billions of stars. Yet the small galaxy has lots of gas. In fact, its gas weighs four times more than all of its stars put together, so unlike most other small galaxies, it can still make new stars.

The secret to the little galaxy’s star-making success is simple: the galaxy has managed to steer clear of both the Milky Way and Andromeda. These giant galaxies steal gas from smaller ones that stray too close. But Leo T is 1.4 million light-years from the Milky Way and even farther from Andromeda. As a result, small though it is, Leo T has been able to retain its gas and forge new stars for more than 10 billion years.


Script by Ken Croswell, Copyright 2014

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