Wendy Freedman

Yeah.

And everybody is working really hard.

Our proposal, the proposal that we put into James Webb Space Telescope, so this is where we're focused now, was to use three different distance indicators.

The Cepheids that we know and love, the tip of the red giant branch, which is a method that Barry and I and collaborators have been working on for many years in the last decade or so have really refined it in terms of improving its precision.

Yeah, that's fair.

These stars, so our sun, our own sun will become a red giant later in its evolution.

And so these are stars that have masses comparable.

These stars have a degenerate core, which is packed very, very densely.

And they've exhausted all the hydrogen in the core so that most of a star's lifetime is spent burning hydrogen into helium in its core, fusing hydrogen into helium.

And then when the star contracts, it's not hot enough to start burning helium.

And that would happen in a more massive star.

So it's burning hydrogen in a shell and putting more helium onto the surface of this core.

And when the core reaches a certain mass, a certain temperature, then there's a thermonuclear runaway.

So suddenly you can start helium burning.

And it releases a lot of energy very, very quickly.

And then the star settles down onto another obscure term in the Hertzsprung-Brussell diagram, what we call the horizontal branch.

But the point is that these are now fainter stars.

And the position at which this what's called core helium flash occurs, occurs at a very well-known luminosity.

And so what that means is we can use, we will observe stars in different galaxies, see how bright they appear to be.

It's another standard candle.