Expert: Ed - 6/18/2008

Question
Hello, and thanks for being willing to answer questions. My question is, what
is the designation of the twenty-first brightest star that is in the open star
cluster called the Hyades? If you want to know why I ask this question, I will
answer, but I thought I should probably leave out extra information.

Thanks very much,

Julian

Answer
Julian,

This was a tough question.  I learned a lot, doing online research, while trying to answer it.  Tragically, eventually I had to throw in the towel and consult an actual astronomy professor at UMASS.

In short, the best answer seems to be that the stars designated HD 27176, also known as 51 Tau, and HD 33254 also known as 16 Orion, are cited as being tied for 20th place.  Both those stars also have many other designations.  So, take your pick.  One of them should be a defensible candidate for being the 21st brightest star in the Hyades.

Also, I have to own up to an oversight.  In your question, you used the term "brightness," as opposed to absolute magnitude.  I wasn't entirely confident what that referred to.  Brightness at what wavelength, etc.  I only JUST noticed, 30 seconds ago, that in the subject line of your question, you did specify absolute magnitude.  So, I don't think that will affect the answer, but it might.  So, if this is for serious research purposes, you should probably double-check my answer somehow.  Cornell's astronomy department has a great "ask an astronomer" feature!  Or just try a few more folks on this site.

The answer I'm giving comes from consulting some old articles, dating back to van Bueren's work in the early 1950s.  I think the answer I'm giving is actually from an article by astronomers named Crawford and Perry, sometime in the 60s, but I would need to go back and check that again.  If so, they drew upon van Bueren's studies.  I am happy to say that I was able to locate those articles on my own, but I thought I was probably missing something more up-to-date.  Also, I wasn't entirely sure that I could understand the articles, because I'm only an amateur.  But if an astronomy professor at UMASS is going to go to those same studies, then I figure that's probably good enough for your purposes.  There has been lots of more recent work on the Hyades, notably by the Hipparcos satellite, but it sounds like any juggling of the rank of brightness is at dimmer levels than the 21st brightest star.

I am sorry I can't be more confident with an answer.  That is the best I can do.  

Can I ask why you are seeking this data?  It's so obscure.  Are you writing a science fiction story, with this as a plot element of some kind?  Or are you testing AllExperts in some way?  I would be keenly interested to know why you asked this question.

Well, have a good one, and Keep Looking Up!
--Ed