Something's up with the North Star, a cepheid. Its distance, mass and age should be easy to measure. But new calculations keep disagreeing with one another and failing to make sense.
Something strange is going on with the North Star : Read more
"Researchers haven't yet made detailed observations of a full circuit by Polaris B. But they've seen enough of the companion star in recent years to have a pretty detailed picture of what the orbit looks like. With that information, you can apply
Newton's laws of gravity to measure the masses of the two stars, Neilson said. That information, combined with new Hubble Space Telescope "parallax" measurements — another way to calculate the distance to the star — lead to very precise numbers on Polaris's mass and distance. Those measurements say it's about 3.45 times the mass of the sun, give or take 0.75 solar masses. That's way less than the mass you get from stellar evolution models, which suggest a value of about seven times the mass of the sun."
Okay, very interesting for stellar evolution modeling. Next, the Cepheid distance ladder in cosmology