How many planets are there in the universe?

Answer 1

HOW MANY ARE KNOWN AT THE MOMENT?:

8 in our solar system + 3 dwarf planets

(Planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus & Neptune) (Dwarf Planets: 1 Ceres, 134340 Pluto, 136199 Eris)

And over 342,500 Small Solar System Bodies (asteroids, minor planets)

AND IN THE MILKY WAY GALAXY?

Since pulsar planets were discovered in 1992 and 51 Pegasi b was discovered in 1995 we now know a total of 209 orbiting other stars:

Detected by radial velocity method: 169 planetary systems, 197 planets, 20 multiple planet systems.

Detected by microlensing: 4 planets.

Detected by direct imaging: 4 planets.

Pulsar planets: 2 planetary systems, 4 planets, 1 multiple planet system.

See the full list in the Encyclopaedia of Exoplanets (see fifth link) published and maintained by the Paris Observatory. Appropriately as it was the work of Urbain LeVerrier at that observatory that led to the discovery of Neptune in 1846.

ASTEROID AND KUIPER BELTS AROUND OTHER STARS

Interestingly two stars, Tau Ceti (11.89 light years away) (see first link) and HD 69830 (41 light years away) (which also has 3 Neptune-sized planets within its habitable zone) (see second and third links) have been found to have asteroid belts in the last couple of years.

Tau Ceti's belt is at least 10 times as massive as ours and HD 69830's belt is at least 20 times as massive as ours. And if ours contains over a third of a million objects, what will theirs contain?!

WHAT OF THE FUTURE?

Improved detection rates can be expected in the coming years. Principally from CoRoT (see sixth link) and the Kepler Mission (see seventh link): which being space-based will avoid the problems the earth's atmosphere creates for ground-based telescopes,

COROT:

On 15th November 2006 the CoRoT spacecraft arrived at the Baikonour launch base,

COROT (COnvection ROtation and planetary Transits) is a space mission approved and led by the French Space Agency (CNES) in conjunction with the European Space Agency and other international partners. The primary objective of COROT will be to search for extrasolar planets, particularly those of large terrestrial size. It is scheduled for launch on December 22, 2006, and will be the first mission of its kind.

COROT consists of a 27 cm in diameter afocal telescope with an array of spectroscopic detectors. The satellite has a launch mass of 630 kg, is 4.10 metres long, 1.984 metres in diameter and powered by two solar panels.

A Russian rocket will lift the satellite into a circular polar orbit with an altitude of 827 km. Over its planned 2½ years mission it will observe perpendicular to its orbital plane meaning there will be no Earth occultations, allowing 150 days of continuous observing. During the northern Summer it will observe in an area around Serpens Cauda and during the Winter it will observe in Monoceros. Between this observing periods for 30 days, COROT will observe 5 other patches of the sky.

The probe will monitor the brightness of stars, watching for the slight dimming that happens in regular intervals when planets transit their primary. COROT will be sensitive enough to detect rocky planets, though only those several times larger than Earth; it is also expected to discover new gas giants, which comprise almost all of the known extrasolar planets.

COROT will also undertake asteroseismology. It can detect luminosity variations associated with acoustic pulsations of stars. This phenomenon allows calculation of a star's precise mass, age and chemical composition and will aid in comparisons between the sun and other stars.

In each field of view there will be one main target star for the asteroseismology as well as up to nine other targets. Simultaneously, it will be recording the brightness of 12,000 stars brighter than apparent magnitude 15.5 for the extrasolar planet study. It is expected that a few dozen planets will be found.

THE KEPLER MISSION

The scientific objective of the Kepler Mission, due for launch in 2008, is to explore the structure and diversity of planetary systems. This is achieved by surveying a large sample of stars to achieve several goals:

Determine how many terrestrial and larger planets there are in or near the habitable zone of a wide variety of spectral types of stars

Determine the range of sizes and shapes of the orbits of these planets

Estimate how many planets there are in multiple-star systems

Determine the range of orbit size, brightness, size, mass and density of short-period giant planets

Identify additional members of each discovered planetary system using other techniques

Determine the properties of those stars that harbor planetary systems

The random probability of a planetary orbit being along the line-of-sight to a star is the diameter of the star divided by the diameter of the orbit. For an Earth-like planet at 1 AU transiting a solar-like star the probability is 0.47%, or about 1 in 210; it's slightly larger at 0.72 AU (the orbital distance of Venus), 0.65%; such planets would be Earth-like if the host star is a late G-type star such as Tau Ceti. In addition, because planets in a given solar-system tend to orbit in similar planes, the possibility of multiple detections around a single star is actually rather high. For instance, if an alien Kepler-like mission observed Earth transiting the Sun, there is a 12% chance of also seeing Venus transit.

The Kepler Mission has probably the best chance of detecting Earth-like planets at current technology levels. One important advantage it has is that it is designed to observe 100,000 stars simultaneously.

This provides a much better chance for seeing a transit. In addition, the 1 in 210 probability means that if 100% of stars observed had Earth-like terrestrial planets, Kepler would find about 480 of them. The mission is therefore ideally suited to determine the frequency of Earth-like planets around other stars

Answer 2

It is estimated that there are at least between 200 - 400 BILLION planets in our Milky Way Galaxy alone!
The exact number of Galaxies in the universe is unknown, as we can only see and observe a very small part of it, but researchers estimate the number of Galaxies to be up to 500 BILLION!! This makes for a staggering number of planets, and to say this is only a small part of the 'whole picture', should put this into perspective.
It truly is MIND BLOWING!!!

Answer 3

One universe, several million galaxies, and billions of stars with trillions of planets. Why not. I have never been arrogant enough to believe we are the only life in the universe. But what does it matter? We are but a drop of water in another's universe. Or as it is stated in the Songs, we are but a mote in Gods eye.

Answer 4

Many scientists would like to know the answer to that question. There is ongoing research.

from www.planetary.org

"By extrapolating from the more than 200 planets discovered so far, the authors conclude that there are a staggering 6 billion Jupiter-sized planets in our galaxy alone."

Probably many times that amount of smaller planets.

Then there are hundreds of billions of galaxies.

Want a VERY rough guess???

50 billion planets per galaxy
200 billion galaxies
10 billion trillion planets
10^22

Answer 5

We can't even make up or minds about the number of planets in our galaxy and you are asking about the number of planets in the universe! We don't even know what the universe looks like or even what it is!

Answer 6

For every grain of sand on earth, there are a thousand galaxies. So far the Milky Way has been identified to have nearly 60 or 80 planets. So if every galaxy has 100, we're still talking about orders of magnitude well beyond billions, trillions, quadrillions, etc.

Answer 7

u first tell me how many solar systems or galaxies r there in the universe?


think over this question before thinking about number of planets.

Answer 8

You really don't want to start counting the planets in the whole universe, trust me.

Answer 9

There are 9 planets in The Universe.........

Answer 10

Nobody knows. About 70 have been found so far, there are MANY more.

Answer 11

897.