Hi any astronomers out there - I’m trying to write some science fiction for NaNoWriMo, and I’ve been thinking about setting an alien civilization on a fictitious planet circling a star that might be known as Gliese 364 (it might also be known as I Hydrae according to this page) a little less than 50 light years from here.
I have two questions if anyone can help me out:
Are Gliese 364 and I Hydrae both names of the same star? (I’m confused because this other page identifies I Hydrae as a different star 500+ light years away.)
I’m also wondering about the classifications - one of these stars is classified G0V, and the other is F9IV… I gather from wikipedia’s stellar classification article that G0V would be hotter that the sun but still main sequence, while F9IV would be both much hotter than the sun and much larger… is that right? What else could we know from the classification?
The Sun is a G2V, so while a G0V would be a bit hotter, it’d still be basically Sunlike.
As for the specific star or stars you’re asking about, I’m not really finding anything resembling consistent information on them, and one of the top Google hits is a paranormal site.
Which one is a paranormal site? Was it one of the ones I linked to? At least I could avoid anything from there.
Are there any good star atlases available online? If I can at least find a source that should be reliable, I can stick with it instead of the random crazies convinced UFOs are the reason their text messages never go through.
You would (if you’re looking for earth like conditions) want the Stellar effective Temp and Stellar Mass and Metallicity to be roughly on par with Sol. Earth and Jupiter are both listed so Sol is already in to help with the comparison.
I should add that the table is for confirmed planets which is only a part of Kepler’s output - you could dig around in the candidate lists.
The star in question is given as N16 Hya, a “Variable Designation” of 175 G., a “Gliese Catalog” of 364, and a “Bright Star Catalog HR number” of 84117…
This is all pretty confusing - do astronomers have a universal systematic naming arrangement for stars, or does each compiler/catalog give its own designation, resulting in multiple identifies for an individual star?
Note: F class stars are hotter than G class stars. The order is OBAFGKMS. The nmemonic to remember this is “Oh Be A Fine Girl, Kiss Me Smack!” There are some oddball categories not provided here, but they would not main sequence stars. Also, I forget if “S” is really a main sequence class, or also an oddball class, at best.
S is more of an oddball class. The sequence is now OBAFGKMLTY, where L and T are for brown dwarfs and Y is for objects too cold to be those. Y objects are generally around 300 to 400 kelvins (note that 300 kelvins is about room temperature).
But equally important is the Roman numeral after the spectral class. A V there indicates a main sequence star such as the sun. An IV is a subgiant, which is a star that’s no longer on the main sequence but has moved off it on the way to being a giant.
I’ve also seen the sequence as OBAFGKMRNS. I can’t remember what sorts of objects are described by R, N, and S, but they’re apparently not considered as important as the L, T, and Y categories nowadays. In any event, everyone agrees on O through M.
R and N are carbon stars. Class S has unusual elements in its atmosphere. They all look redder than they would based just on their temperature, so they were placed after M. The spectral classes were originally based on the color of the star but are now based on temperature.
