Looking Up: 'B' Is For Brightest

Oct 1, 2018

Credit Till Credner - AlltheSky.com / Wikimedia Commons

The alpha star is not always the brightest star in a constellation, as we learn on this week's Looking Up.

I want to tell you about a very strange star known formally as Beta Ceti, and less formally as Diphda.

Normally, the brightest star in a constellation gets to be the “alpha” star, but in Cetus the Whale, the brightest star is the beta, Diphda. And Diphda is weird. The name means, well, first frog. Which means, of course, that there must be a second frog star, which there is, the much brighter Fomalhaut. I told you it was weird up there.

Diphda is a dying giant star, but is warmer than most others, and is about 145 times brighter than our Sun. So far, so good, but Diphda has a dark secret, or at least an invisible one. It seems this quiet little star is also, and surprisingly, a major source of x-rays. That really shouldn’t be. Astronomers think the star’s magnetic field above the surface is somehow twisting and magnifying the x-rays in Diphda’s corona. And to do that, it should be spinning rapidly, but it isn’t. There are a number of theories about how this can happen, but we just don’t know. So Diphda is kind of like that really strange neighbor that does weird things. So keep an eye on the oddball Diphda – we don’t know what it will do next!

If you’d like to take a closer look Diphda, or any of the other wonderful and amazing things in the sky, please visit csastro.org for a link to information on our monthly meetings and our free public star parties.