Dear Denzil

Very funny. Are you in league with Margie Hansen or something? But seriously... This is a tough question.

You probably know that astronomers look at the sky with optical telescopes and radio telescopes. They can see light from stars and galaxies and so on--and pick up radio waves from them, too. Both types of information are useful.

By the 1960s astronomers had found lots of strong radio sources coming from far out in the universe. The astronomers wanted to match them with photographs taken with optical telescopes.

They ended up discovering that the objects associated with several of these powerful radio sources just looked like stars. (In a photograph all you could see was a point-like object that looked like a star. It wasn't extended like a nebula or a galaxy).

However, when they looked at the optical spectra of these 'radio stars', they found that they were redshifted (like Hubble's galaxies). Because redshift is supposed to match up with distance, this meant that these objects were a very long way away. But being so bright (at radio frequencies) they couldn't possibly be stars. So they called them 'quasi-stellar objects'. ('Quasi' means 'more or less' or 'something like'; 'stellar' means 'star'.)

Pretty soon 'quasi-stellar object' turned into 'quasar'. It was easier to say, and sounded cool.

But why couldn't the quasars just be ordinary stars?

OK, so what are they really? We simply don't know.

There is a theory about how a quasar works, but nobody knows if it's true or not.

Astronomers hope to improve their understanding of quasars but it's going to take a lot of work by people like Sophie before we can be really sure what they are.

Yours sincerely 

Virginia R. Claire


read the question in the original letter