Do suns/stars ever orbit other suns/stars?

Question

The thought just came to me, the general understanding of a solar system so most people is obviously an understanding of our own solar system. Where you have planet orbiting a sun and satellites orbiting planets etc. First question:
What is the definition of a planet?

I know that suns/stars vary massively in size and that there a stars much much bigger than our sun. Second questions:
Do stars ever orbit other stars ie one of the smallest stars orbiting one of the largest?

My third question is answered by the the first too. I speculated that the definition of a planet would an object of a certain size orbiting a star. (I won't know this until your answer of course). But if that is the definition, and a star can orbit another star, can a star be a planet?

I realise that potentially my third question makes no sense, depending on the answer to the first question.

Answer 1

The definition of a planet is a celestial rounded body (rounded by its own gravity) that orbits a star and has cleared its general neighborhood but is not massive enough to undergo thermonuclear fusion (Pluto does not satisfy the second characteristic, stars satisfy the third characteristic).



Yes stars do orbit other stars, there are plenty of examples of binary stars (two stars orbiting one another). Our solar system orbits the main body of our galaxy (the milky way).



No a star cannot be a planet.



The centre of the milky way contains a huge black hole (4 million solar masses) and a huge number of stars, the sheer amount of stuff in the galactic centre gives it a large amount of gravity - attracting objects outside of the centre (this can be seen in the picture in the sources, the bulging yellow area is the galactic centre). Our solar system is outside the galactic centre and thus we orbit it.

Answer 2

The definition of a planet - there are 3 criteria



1) The object is spherical

2) orbits the sun

3) cleared its neighborhood (orbital path) of debris





Do stars orbit other stars



Anything in space can orbit anything else if the speed on first approch, and size is correct. By size I mean MASS - and there are binary and even 3 star systems



but in those systems one star is not orbiting another, 2 or 3 stars are orbiting a center point, but the larger star in the system may dominate the orbital path



but yes, its possible, if a small star with low mass, was in the orbital range of a huge massive star, it could orbit it





Can a star be planet?



No - these are two distinct things. Even tho it may seem like a star could fit the criteria of a planet, a Star has its own criteria it meets, making it the Star !





Again - the star orbiting, people that mention binary systems, are talking abut a center point of mass, for example, two stars will circle a center point, because their combined pull of gravity causes that type of reaction



but yes, like i said, anything can orbit anything, if the speed/mass ect... are all in range





and lastly, the stars at the center of the milky way orbit a "Supermassive" Black hole - its a black hole millions to billions times the mass of the sun. It is now being found it exists in the center of almost every Galaxy. Stars at the center move at VERY Fast speeds around the SuperMassive Black hole - they are AWESOME, look it up at wikipedia, They are so powerful its insane!

Answer 3

In practical terms, yes. To be more precise, binary (or triple) stars do not orbit each other, but orbit a common center of gravity. Planets in orbit around these stars can be imagined, but it would depend on the distance between each star, and could only happen if the distance is great enough. If the two stars were closer together, the tidal forces operating on the planet would prevent it, or the orbit, remaining stable, so it would be unlikely that such a system would occur in the normal way, but only from the temporary capture of a passing body. All the stars in the Milky Way, not just the inner ones, orbit the center of the Galaxy, where, we suspect, there is a supermassive black hole of several million solar masses.

Answer 4

Sure. "Binary Stars" are quite common.



However, in this case ONE of the star is usually a brown dwarf -- a dead star. Because of the immense gravities of the two stars, it is not likely that a binary star system has any planets. No, it is not possible for a "star" to be a "planet". A "planet" is not defined only by the fact that it orbits. there are many other characteristics that make a "sun" and a "planet" different -- like suns give off energy, while planets absorb it.





There have been about 300 "planets" discovered in other solar system, but many scientists that that MOST of these are are actually binary star systems.



You can easily look up BINARY STARS on an internet search engine.



i don't think I've ever heard of a trinary star system though -- three stars orbiting each other.

Answer 5

Multiple star systems are quite common. Although, in most cases, one orbiting another isn't the most accurate term in the sense the the barycentre (common center of gravity) in which both (or more) stars orbit in this type of system is not "inside" of one of the stars... like when the earth and sun orbit around their common center, that center is so incredibly close to the center of the sun, because the sun's mass is so enormous compared to the earths. We have an example in our solar system of bodies orbiting a barycenter that does not lie within the body of the larger mass... the Pluto-Charon system has it's barycenter outside of the surface of Pluto. See source for some animations of various multiple star system orbital patterns.



We have detected star systems with as many as 6 stars gravitationally bound in orbits to each other. Castor, one of the bright stars in Gemini, is one of these star systems. A double-triple... (or triple-double? I don't recall which).



Catyclismic variables are also something you might be interested in. In these binary systems, two very different stars are in orbit around a common center, while one of them "steals" matter away from another... resulting in a Type Ia supernova (more details in sources).

Answer 6

Most stars are in binary or multiple systems. Single stars like our sun are in the minority. If is often true that the stars of a binary or multiple system are of unequal masses. No, a star is not a planet just because it orbits another star.



A planet is a spherical (or oblate spherical) non-stellar mass that has cleared its orbit of debris and has no degenerate matter at its core. Planets shade into dwarf planets (asteroids and icy bodies) at the low end of the mass scale, and into brown dwarfs (protostars) at the upper end of the mass scale.

Answer 7

The binary stars are orbiting each other, not some other "common mass"

Answer 8

The moon shines with meditated solar. without solar the Moon would be very very dim reflecting the easy from out synthetic easy materials. without solar or Stars or synthetic lighting fixtures fixtures then the darkness may be finished (with the exception of the fires we'd easy)

Answer 9

For the last two additional questions on the first additional details unless you add another set:



http://www.universetoday.com/2008/12/10/beyond-any-reasonable-doubt-a-supermassive-black-hole-lives-in-centre-of-our-galaxy/

http://en.wikipedia.org/wiki/S2_(star)

http://en.wikipedia.org/wiki/Sagittarius_A*