Anybody have any information about Rho2 Cephei?

[lunarhalo]

Hi, I am new to both this community and stargazing, i.e I am more like an astrophysics enthusiast and wanabe stargazer. I was doing some random research on a couple of stars and am interested in acquiring some more detail on Rho2 Cephei (Al Kalb Al Rai). First of all, I don't understand why it is said to belong to the Cepheus constellation as the diagram clearly shows that it is outside any discernible shape. Secondly, Google search results tend to return information on Rho2 that is either 1) Incomplete 2) Irrelevant 3) Incomprehensible. If any can someone please post a bit of historical, cultural and scientific details (images if possible) of this mysterious star? Are there any planets orbiting it? Are there any black holes/supernovas/white dwarfs/nebulae nearbly? How old is the star? Is it a yellow giant? What is the stars mass? What does its name mean? How far away is it? Forgive me for my potentially annoying curiosity. I would also appreciate it if the replies are made in laymen's terms as I am still new to this subject.

Thank you for taking the time to read this.

lunarhalo

[Kevdan]

Hi,

Cant realy answer all your questions , but if you have stellarium or other programs try to find it and when clicked on it will give you magintude, position and distance from earth, not all what you were looking for but a start.

Kev.

[Qualia]

Hiya Lunar Halo, it's just a hunch but jsandse may know a thing or two. He's a member here and I'm sure he wouldn't object to a private message. This link may answer oneor two of your questions: http://www.wolframalpha.com/entities/stars/rho_2_cephei/dz/up/9c/ ?

[DirkSteele]

"First of all, I don't understand why it is said to belong to the Cepheus constellation as the diagram clearly shows that it is outside any discernible shape."

A constellations borders are not determined by the actual shape that you or I would recognise as the constellation, but actually by borders that the diagram you linked to shows in blue. Any star within these borders is associated with that constellation so in this case it is in Cephus.

The spectral classification is A3V. The A3V means it is an A Type main sequence star , or a dwarf star. It has a bluish tint (as defined by is A class) and would show strong hydrogen lines if you looked at the spectra of the star as well as ionised metal lines (for more info on what this means Google stellar spectroscopy). From the A3 classification we can also say that it has a mass about twice that of the Sun, a radius about 1.7x that of the sun and a surface temperature of about 8,400C. Other more well known A class stars include Vega and Altair. The next class down from A, is G type stars, of which the Sun is a member (G2V).

It's distance according to the Hipparchus catalogue is 73 parsecs / 237 light years. In miles that is approx 1,391,190,000,000,000.

A class stars tend to only stay on the main sequence (normal lifetime of hydrogen burning in the core) for about 1 billion years (versus 10 billion for the Sun - currently about 4.5bn years old) so they tend to be quite young in stellar terms. They also often emit more infrared than would be expected from the star alone, which is usually a good indication of a dusty debris disk around the star that may be forming planets. However, I do not know if this particular star has that characteristic.

As for other objects of interest such as black holes and the like, I do not know off the top of my head.

Hope this gets you started.

[Helen]

The SIMBAD database is a good start http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=rho2+cephei&submit=SIMBAD+search Its a very powerful tool and there are tutorials on how to use the various elements (see the lifebelt on the menu).

Helen