How many Planets is in existence in universe ?

Question

Must knows

Answer 1

HOT OFF THE PRESS

Breaking news tonight is that Gliese 581 c discovered yesterday (20.5 light years away) is a planet that is of a habitable temperature and 5 times the mass of earth and this is described as a major breakthrough (see 3rd link) Discovery date 2007-04-23

Gliese 581 b is a large Neptune-sized planet discovered in 2005,

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8 in our Solar System and 3 dwarf planets

228 extra-solar planets known to date; they orbit stars in our immediate vicinity in the Milky Way. The nearest such planet is Epsilon Eridani b about 10.5 light years away and the furthest is a red dwarf star 21,500 light years away. That might sound a lot but the galaxy is 100,000 light years across, so it is still local to us on a cosmic scale.

There are 21 stars known to have more than one planet: 15 with 2 known planets, 4 with 3 known planets and 2 with 4 known planets. Gliese 876 which has 3 planets (b, c and d) is only 15 light years away,

One limitation at the moment is that we tend to only be able to find gas giants and ones that are close to their parent stars, the so-called "Hot Jupiters", Our technical limitations are making it look like smaller rocky planets are much rarer, but they are simply harder to find,

The first extra-solar planet was discovered 15 years ago and we are now findng them at the rate of 20 a year. They were long suspected to exist and indeed had been postulated as existing by the Greek philosopher Democritus 2500 years ago.

Democritus was the first philosopher we know who realized that the celestial body we perceive as the Milky Way is formed from the light of distant stars. Other philosophers, including later Aristotle, argued against this. Democritus was among the first to propose that the universe contains many worlds, some of them inhabited:

"In some worlds there is no Sun and Moon while in others they are larger than in our world and in others more numerous. In some parts there are more worlds, in others fewer (...); in some parts they are arising, in others failing. There are some worlds devoid of living creatures or plants or any moisture."

We are just beginning to prove he was right!

The best current estimate of the number of stars in the universe is 70 sextillion (7 x 10^22) and if one in ten of those has an average of 1.5 planets each, that would be 10^22 planets in the known universe.

There must be a reasonable percentage of these that are in the habitable zone with liquid water, an atmosphere and protected from harmful radiation which have prospects for life evolving there.

Answer 2

Technically most of these answers are correct since your question was not very specific. Currently there have been about 200+ extra solar worlds discovered. (I used the word "worlds" because of the continuing debate over the definition of planet. . . and don't think that the mess involving Pluto is over).
Anyway, you didn't ask that, you asked how many planets are "in existence in the universe". The big assumption that needs to be made to answer that is: Is our Solar system typical in the Universe. If so, then multiply 8 (or 20 or 95 depending on your definition of Planet) times 300 billion (# of stars in the galaxy) times 150 billion (# of Galaxy's in the universe) and you get approx. 3.6x10e23 planets in the universe (that's 360,000,000,000,000,000,000,000 or 380 septillion planets).
But maybe you think that our solar system is pretty unique and only one out if a million stars actually has any kind of planet around it. Further you assume that most of those stars have only 1 planet around it, in that case the figure drops down to ONLY 4.5e16 (45,000,000,000,000,000 or 45 quintillion planets)

Answer 3

We can estimate how many planets per galaxy, but we don't really know how many galaxies exist in the universe...Right now, we know of the 8 major planets in our solar system, and about 110 worlds orbiting other, close-by stars (about 1 star in 8 seems to have planets, in a rough-area sampling), so figure - there are 400,000,000,000 stars in our galaxy; if one-in-8 has planets that's on the order of 50,000,000,000 planets in our galaxy alone.

And our galaxy is fairly small.

Answer 4

We do not know about the entire universe, or even the Milky Way galaxy, but there are 8 planets in our solar system, now that Pluto has been reclassified as a dwarf planet.

Answer 5

That question is impossible to answer because there are more Suns that there are grains of sand on every beach in the world, and if a fraction of those Suns have at least 3 planets and I know most of them have more, hell we have 8 and our sun is average at best, then you can conclude that there would be at least as many planets as there are suns times 3

Answer 6

Nobody knows. It is a huge number though....galaxies hold anywhere from 1 million to hundereds of billions of stars. There are an estimated 125 billion galaxies in our observable universe. So, I would say there are tens to hunreds of trillions of planets (at least).

Answer 7

Probably only like 42. It's good our solar system has such a strong representation then.

Answer 8

we may never know it seems as if every few years they discover more-good luck on you journey to know