How many solar systems are there in Milkyway, our galaxy?

Question

200 million?

or 200 billion?

or are both wrong?

Answer 1

Well, the actual number out there is not known. As everyone's said, Milky Way is estimated to have upwards of 200 billion stars in it. We don't know what percentage of stars have planets orbiting them, but I personally assume that it would be a high percentage. It just seems pretty reasonable to me that forming stars wouldn't be perfect in slurping up their entire stellar disks while condensing. Now whether or not the remaining material forms planets, and whether or not their orbits are stable remains to be seen.

Currently, we can't see with enough precision. When we investigate a star for planets and don't find any, we can't say that there are none - just none found. When we can observe distant stars with enough precision to say with confidence that we would not miss any planets with something like 90+% uncertainty, then we would begin to say which stars definitely do not have planets.

We have found over 200 extrasolar planets to date. I'm not sure how many of them are in unique systems, but I'm thinking the majority are. Given the rate that our puny detection capabilites is spotting them, I'd say the number of 'solar systems' out there in the Milky Way is well over 50 billion.

Answer 2

The Milky Way galaxy contains somewhere between 200 billion and 400 billion STARS.

If you consider a star by itself to be a 'solar system', then your second answer is closest.

Many of those stars do have planets and other stuff around them... but how many is anyone's guess.

Answer 3

It's hard to say, exactly. "The galaxy is estimated to contain 200 billion stars but this number might reach 400 billion if small-mass stars predominate" (Wikipedia), but that doesn't mean that they are all solar systems.

A solar system must have not only a star, but objects orbiting it. Not all of the stars in the galaxy may have obiting matter, particularly since the majority of stars are extremely small, even relative to our own star, the Sun.

Known as red dwarfs, these "stars" are actually the final stage of all extinct low-mass stars, and have "a mass of less than one-half that of the Sun [...] and a surface temperature of less than 3,500 K" (Wikipedia) -- compared to the 6500 K temperature of our Sun.

The smallest star type that we know of are brown stars (aka "failed stars") which are up to 75 times as massive as Jupiter, "too small for major nuclear fusion processes to have ignited in its interior" (ESO.org).

Some red dwarfs have been confirmed to have planets as large as Neptune in orbit. However, "there are several factors which may make life difficult on planets around a red dwarf star" (Wikipedia), and not all stars necessarily have planets orbiting them.

It's safe to say that the 200 billion figure does not apply to solar systems, but merely to stars. How many solar systems there are exactly is almost impossible to guess. The Milky Way is a big place, and sometimes, the most difficult place for astronomers to look is right in their own backyard.

Answer 4

It is only an estimate, but it is around 200 billion stars. I would assume that all stars have solar systems.

"The galaxy is estimated to contain 200[6] billion stars but this number might reach 400 billion[7] if small-mass stars predominate."

Answer 5

200 billion stars is the starting ESTIMATE with some doubling that number. Estimating the number of stars with planets circling them (solar systems) is currently impossible, though the number of stars with confirmed solar systems is increasing almost daily.

Answer 6

There is only ONE Solar System - the one we belong to. Solar System means the family of the sun. So far more than 200 stars are known to have planetary systems, extra solar planetary systems. As for the numbers of extra planetary systems, it could number in the hundreds of millions.

Answer 7

About 14.4 billion starsystems by my own estimate. Those are stars that if they have a planet like earth in the right orbit would be completely right for generating life as on earth. But it is unlikely that all of them have an earth. It is very likely that they have some kind of planet however making them solarsystems. So----rry. Starsystems...

Answer 8

Yay for suziebarclay...the only one to answer correctly (until I showed up).

There is only ONE "solar system." The word "solar" refers to "sol," that being our sun. It is not used to reference other stars. Other stars may well have planets, but they are not "solar" systems.

Answer 9

Both are wrong. It's 315,693,382.
Nobody knows! We've only discovered a handful of planets outside our own solar system so far.

Answer 10

The call of our image voltaic device is THE image voltaic device. the rationalization is by using the fact the sunlight's call (between astromoners) is Sol... subsequently the only celebrity device which you may call 'the image voltaic device' is ours. the different celebrity platforms would be named after the celebrity or stars they comprise. of direction, whoever lives there ought to disagree appropriate to the call.