how many planets are there?

Question

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Answer 1

There have traditionally been 9 planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.

Scientists used to think that there was perhaps a tenth planet, Planet X, that we couldn't see causing some weird gravitational effects on Uranus and Neptune. However, I believe that this has been resolved since we have gotten more accurate mass information on Uranus and Neptune and no tenth planet is necessary.

However, more objects have been discovered near Pluto and of a similar and in some cases larger size than Pluto. These are the Kuiper Belt Objects. Some of the larger ones are Xena, Sedna, Quaoar, Ixion, and Varuna. It's something like a second asteroid belt just past Pluto. There is some debate over whether or not these should also be considered planets (since they are in some cases as massive or bigger than Pluto) or whether we should just revoke planet status for Pluto. So depending on how you look at it, there are between 8 and perhaps thousands of planets.

But officially, there are 9 in our solar system, according to the International Astronomical Union which is responsible for naming all objects be they planets, comets, or asteroids.

As for extrasolar (beyond the Sun) planets, over a hundred and fifty have been discovered through gravitational effects. Only one has actually been observed transiting across a star. There is evidence that multiplanetary systems are common (the first one discovered was the Upsilon Andromedae system) and that some of the planets discovered have smaller companions orbiting them. All of the planets discovered outside of our solar system have been gas giants since they are larger and have more easily observable effects on stars.

Here's a website with a list of planetary systems discovered with the star they were found around, the number of planets known to be there, and the team that discovered them. The sun is the very first entry.
http://www.princeton.edu/~willman/planetary_systems/

Answer 2

There are 10 planets in our solar system:

Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
Planet X (really)

There are so many planets in the universe, that there is no number for it - actually, there are more GALAXIES than there is a number for. To give you an idea of how huge the universe is and how many galaxies & planets there are, see the link below; it is the deepest view into space taken by the Hubble telescope and basically represents less than a pinhead of the actual sky- and waaaay zoomed in at that. I think there are over 10,000 galaxis in just this picture alone, and there would be trillions more if the could zoom in infinitley. check it out below.

Answer 3

Currently, there are nine well-known planets in our Solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto . Three planetoids and millions of minor planets.
Our solar system could be divided into:
# The inner solar system contains the Sun, Mercury, Venus, Earth and Mars
# The main asteroid belt lies between the orbits of Mars and Jupiter.
# The planets of the outer solar system are Jupiter, Saturn, Uranus, Neptune and Pluto:
# Solar System's final frontier: (home of the planetoids) Kuiper Belt and the Oort Cloud. The planetoids are :
- Quaoar (Kwa-whar), officially known as 2002 LM60, orbits the Sun every 288 years about a billion miles beyond the orbit of Pluto
- Orcus (officially knows as 2004 DW), It is considered a "plutino" or "little Pluto" because of its similar orbit with the planet
- 2003 UB313, it orbits the Sun about every 560 years, and has a small moon

Answer 4

The correct answer is that no one knows. We have located 10 planets in our solar system, but there may well be others that we have not as yet discovered. We don't know how many other solar systems there are in the universe. The bottom line is, no one knows.

Answer 5

Technically, 10, with two pending and maybe one deletion.

Mercury
Venus
Earth
Moon
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
Charon (pending)
Xena (pending, hopefully with a name change)

The moon and earth are a "double planet" system, as the moon sometimes "falls" toward the sun, rather than only the earth. This was explained to me a while back by a really nice if kooky science teacher. That's why Charon also may be re-evaluated... but may be deleted if Pluto is taken off the list. Xena... god I hate that name... may be granted planet status, but that's still pending.

Answer 6

In our system the argument is presented for 10 items that can be called planets, there are countless other planets in the universe.

Answer 7

uptil now 9 have been discovered

Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto

but there aresome more planets tht scientists hv some knowledge of.. like, a planet which is about 3 times larger than jupiter and another planet which have water!!

Answer 8

No one knows for sure. There nine in this system that have ID ed and named. A tenth has been seen, not sure if it is a planet or a moon.

Answer 9

Millions

Answer 10

There were nine planets in our solar system... up until a few years ago, when a trans-Neptunian object (2003-UB313), was classified as a planet.