This is CBS Eye in the World.

I'm John Batstra.

I welcome Dr. Ken Croswell, writing most recently at Science News about the stars in our

beautiful galaxy and distinctions made between a red dwarf and a brown dwarf.

Ken is the author of the Lives of Stars in the Alchemy of Heavens.

So I follow his lead when we come to this very particular language about stars.

We have a beautiful star.

It is main sequence, Ken teaches me.

But not all stars are main sequence.

And the most popular, that is to say, the most numerous star in the galaxy is a dwarf,

a red dwarf.

Ken, a very good evening to you.

What does it mean when you call a star a dwarf?

A red dwarf, a brown dwarf, a yellow dwarf, a blue dwarf?

What does dwarf mean?

Good evening to you.

Well, good evening, John.

Unfortunately, this term is not terribly well used by astronomers, in my opinion.

For most stars, they'll not all.

The term dwarf means that the star is engaged in nuclear reactions that convert hydrogen

into helium at its core, it is a main sequence star.

That's the case for the sun, that's the case for these red dwarfs that we are going

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