this post was submitted on 17 Jun 2023
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Actually as weird as those names look, they all make sense..
I hate when people say stuff like this and then never elaborate why.
The name HD 189733 b is derived from the naming convention used for astronomical objects. Let's break it down:
Therefore, HD 189733 b signifies the first planet discovered orbiting the star HD 189733. This naming convention allows astronomers and researchers to identify and differentiate between different planets and their host stars in a systematic manner.
TOI 849 b is TESS Object of Interest's 849th discovery of interest. The numbers are essentially arbitrary outside of that numbers before them have already been taken.
Hell yea. This is the content I came here for. Thanks for the explanation.
What if it is a 2 star system? A and b etc. is taken. HD 189733 is good the first star, then we find the second... HD189733 AA?
I fucked up a little so I understand the confusion, stars are typically in capital letters, A, B, C.
though clear distinctions are also made here. B, C, D implies a hierarchy of orbits, A is the primary gravitational pull in its system
Aa, Ab, (etc.) is used when two (or more) stars have a common center of mass
Real implications of this example:
Kepler-16A and Kepler-16B have a planet that orbits both (but to be clear they do not having a common center of mass), so it is Kepler-16b, and I didn't look it up but I assume it's not 16ABb because there aren't any A or B planets to differentiate it with
Polaris Aa and Ab are orbiting around a common center of mass, and Polaris B orbits them from further away
Castor has 6 stars, here's an image
Aa and Ab are still the main center of mass in this system
as an added bonus, black holes do not have a naming convention yet, Sagittarius A* is just in the Sagittarius A region and * is to indicate an exciting or interesting object
and to my knowledge, it is theoretically possible for a planet to orbit an Aa star without orbiting an Ab star but I don't think we know of any, I assume it would be named like Aa b
When you say common center of mass, so you mean the as in something like... Once it is outside of the object? Otherwise I assume everything has a common center of mass with everything.
Thanks for the info!
Common center of mass means they spin around each other, currently the moon orbits earth, but long long in the future, even though the moon is smaller, it will have waned the pull of the earth to an extent where you both go around in the same circle, this happens quicker with objects the more equal in size they are
There are an estimated 400 billion stars in the milky way galaxy and an estimated 2 trillion galaxies in the observable universe. It would not be reasonable or even possible to give every star a unique alphabetical name even for all the known languages in history.
We just need to combine words of different languages. Is there are 100 languages with 10'000 words each, that gives us ... Overflow number of options. Thank you windows calculator, who needs arbitrary precision anyway. 10^20'000 is a big number tho.