# Variable star

1. Mar 4, 2004

### juan avellaneda

mira is a binary star!! thats new for me
and this photos show the real surfasce of mira and betelgeuse, wow
if im not wrong , Betelgeuses diameter was first meassured by interferometry
there are other supergiants waiting, like "Garnet" star, or R hydra. Whats the most giant star ever discovered??
thanks a lot for this new sights of the stars

2. Mar 4, 2004

### meteor

The biggest star ever discovered is epsilon Aurigae. It has a diameter of 2700 times the diameter of the sun

Saludos

3. Mar 20, 2004

### Labguy

I have been looking around and keep finding that Eta Carina and/or Garnet Star are largest actual diameter. Do you have a site for me re: epsilon Aurigae ?

4. Mar 20, 2004

### wolram

5. Mar 20, 2004

### Labguy

That gave light curves, and the home page mentioned the possibility of a giant "gas cloud" surrounding the two smaller stars accounting for the long period. I didn't see anything about the physical size of Epsilon Auriga itself except for its spectral class. ?? Anything more on the physical size of the star itself instead of associated (possible) gas clouds? If we count associated gas clouds with size, I think Eta Carina has them all beat.

From: http://groups.yahoo.com/group/astrospace-l/message/2005

"The "garnet star" has the largest known actual diameter:
http://features.LearningKingdom.com/fact/archive/1999/06/07.html [Broken] "

Or maybe: http://www.astronomyinfo.pwp.blueyonder.co.uk/Big&Little.htm
" The star imaged below is possibly the largest star in the milky way galaxy. It is called Eta Carina in the southern constellation of Carina." But, http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0010271.html would support Epsilon Auriga.

No argument here, I just wonder if "they" know the largest individual star, now that my curiosity is peaked.

Last edited by a moderator: May 1, 2017
6. Mar 20, 2004

### meteor

Labguy,
http://www.aavso.org/vstar/vsots/1002.shtml [Broken]
it says that the Garnet star (Mu Cephei) is the third largest star in the sky, and that the largest is Epsilon Aurigae

I have a notebook where I write curious facts about astrophysics and it my notes Epsilon Aurigae has a diameter of 2700 solar diameters. Mu Cephei has a diameter of 2500 solar diameters. It is also confirmed in this page
http://www.minorplanetsearch.com/hap_ic1396.html [Broken]
From the page you gave
http://www.astronomyinfo.pwp.blueyonder.co.uk/Big&Little.htm
it says that eta carinae has a diameter of 100 solar diameters, but
it's surrounded by two lobes of gas that makes it to seem bigger.
I wouldn't count those lobes as forming part of the star, just are gases that are been expelled in the final stages of eta carinae, just before it goes supernova.
It's just like when a star that reaches the end of the main sequence expells all these gases when it reaches the phase of planetary nebula. I don't think that we should count these gases like forming part of the star
I remember to have observed Epsilon Aurigae with my telescope. I didn't knew then that it was the biggest star, but when I read it, I was happy to have observed it.
Perhaps it's time to return to do some observational astronomy. It has been more than 3 months since I don't touch my telescope.I Have been lately very much busy studying theoretical aspects of cosmology

Last edited by a moderator: May 1, 2017
7. Mar 20, 2004

### Nereid

Staff Emeritus
This reference gives absolute radii of several thousand stars, many determined with an accuracy of ~<1%. Apart from an item which seems obviously erroneous (RS Vul), the largest diameter in the list is "EPS AUR", at 2700 sol. #2 is "VV CEP" with diameter listed as 2000, 1940, and 1230 (three different observations). However, note that $$\epsilon$$ Aur has other entries: 1270, 1000, 716, ...

Mira ($$o$$ Cet) has lots of entries, one of which is 230.

[Edit: fixed typo, cleared up an ambiguity]

Last edited: Mar 21, 2004
8. Mar 21, 2004

### Labguy

Meteor & Nerid;
Thanks for the links, that's what I needed. I didn't "want" to count associated gas as with Eta Carina. I have dabbled with stellar evolution for years, it just never dawned on me to wonder which star(s) were the largest measured to-date.