which is the smallest planet in universe?

Answer 1

We were till recently only capable of detecting planets of at least the size of Jupiter in other solar systems so the smallest planet we knew about was inevitably the smallest planet in our own solar system,

That is still the case but for how much longer? Given the rapid developments in this field.

New information is now to hand as a result of new methods of detection, Smaller extra-solar planets have been found orbiting red dwarf stars, previously considered an unlikely place to find them, As 85% of stars in the Milky Way are red dwarfs this significantly increases the chances of life being found elsewhere in the universe.

THE THREE SMALLEST KNOWN EXTRA-SOLAR PLANETS

In August 2004, a planet orbiting Mu Arae with a mass of approximately 14 times that of the Earth was discovered with the ESO HARPS spectrograph. It is the third lightest extrasolar planet orbiting a main sequence star to be discovered to date.

In June 2005 a third planet orbiting the red dwarf star Gliese 876 was announced. With a mass estimated at 7.5 times that of Earth, it is currently the second-lightest known exoplanet that orbits an ordinary main-sequence star. It orbits at 0.021 AU with a period of 1.94 days.

On January 25, 2006 the discovery of OGLE-2005-BLG-390Lb was announced. This is the most distant and probably the coldest exoplanet yet found. It is believed to orbit a red dwarf star around 21,500 light years away, towards the centre of our galaxy. It was discovered using gravitational microlensing and is estimated to have a mass of 5.5 times that of Earth, making it the least massive known exoplanet to orbit an ordinary main-sequence star.

Prior to this discovery, the few known exoplanets with comparably low masses had only been discovered on orbits very close to their parent stars, but this planet is estimated to have a relatively wide separation of 2.6 AU from its parent star.

NAMING CONVENTION

According to astronomical naming conventions, the official designation for a body orbiting a star is the star's catalogue number followed by a letter. The star itself is designated with the letter 'a', and orbiting bodies by 'b', 'c', etc.

HOW MANY DO WE NOW KNOW ABOUT?

I had thought we had found about 9 such planets orbiting other suns. I was wrong, As of April 2006 we were up to 185 and as of June 21 2006, 194. As Wikipedia explains:

"Of the 185 extrasolar planets (those outside our solar system) discovered to date (14 April 2006) most have masses which are about the same or larger than Jupiter's.

Exceptions include a number of planets discovered orbiting burned-out star remnants called pulsars, such as PSR B1257+12, the planets orbiting the stars Mu Arae, 55 Cancri and GJ 436 which are approximately Neptune-sized, and a planet orbiting Gliese 876 that is estimated to be about 6 to 8 times as massive as the Earth and is probably rocky in composition."

(Gliese 876 is about 38 light years away from us.)

"It is far from clear if the newly discovered large planets would resemble the gas giants in our solar system or if they are of an entirely different type as yet unknown, like ammonia giants or carbon planets.

In particular, some of the newly discovered planets, known as hot Jupiters, orbit extremely close to their parent stars, in nearly circular orbits. They therefore receive much more stellar radiation than the gas giants in our solar system, which makes it questionable whether they are the same type of planet at all."

There is also a class of hot Jupiters that orbit so close to their star that their atmospheres are slowly blown away in a comet-like tail: the Chthonian planets.

NASA has a program underway to develop a Terrestrial Planet Finder artificial satellite, which would be capable of detecting the planets with masses comparable to terrestrial planets.

The frequency of occurrence of these planets is one of the variables in the Drake equation which estimates the number of intelligent, communicating civilizations that exist in our galaxy.

The first system to have more than one planet detected was υ Andromedae. Twenty such multiple-planet systems (including our own) are now known.

As regards main sequence stars, there are currently 45 known planets in 19 multiple planet systems and 144 known planets in single-planet systems.

Plus there are currently five known planets orbiting two different pulsars, one known planet orbiting a brown dwarf and two suspected free-floating planets, i.e. they don't appear to orbit a star.

MULTI-PLANET SYSTEMS

Star Planet / Minimum Mass(× Jupiter) / Orbital Distance (× Earth) / Orbital Period (days)

47 Ursae Majoris b 2.63 2.13 1089.0
47 Ursae Majoris c 0.792 3.79 2594

55 Cancri A e 0.045 0.038 2.81
55 Cancri A b 0.784 0.115 14.67
55 Cancri A c 0.217 0.24 43.93
55 Cancri A d 3.92 5.257 4517.4

Gliese 777 A c 0.057 0.128 17.1
Gliese 777 A b 1.502 3.92 2891

Gliese 876 d 0.023 0.021 1.94
Gliese 876 c 0.56 0.13 30.1
Gliese 876 b 1.98 0.21 61.02

HD 12661 b 2.30 0.83 263.6
HD 12661 c 1.57 2.56 1444.5

HD 37124 b 0.61 0.53 152.46
HD 37124 c 0.6 1.64 843.6
HD 37124 d 0.66 3.19 2295

HD 38529 b 0.78 0.129 14.309
HD 38529 c 12.70 3.68 2174.3

HD 69830 b 0.033 0.0785 8.667
HD 69830 c 0.038 0.186 31.56
HD 69830 d 0.058 0.63 197

HD 73526 b 2.9 0.66 188.3
HD 73526 c 2.5 1.05 377.8

HD 74156 b 1.86 0.294 51.643
HD 74156 c > 6.17 3.40 2025

HD 82943 b 0.88 0.73 221.6
HD 82943 c 1.63 1.16 444.6

HD 108874 b 1.36 1.051 395.4
HD 108874 c 1.018 2.68 1605.8

HD 128311 b 2.58 1.02 420.514
HD 128311 c 3.21 1.76 919

HD 168443 b 7.7 0.29 58.116
HD 168443 c 16.9 2.85 1739.50

HD 169830 b 2.88 0.81 225.62
HD 169830 c 4.04 3.60 2102

HD 202206 b 17.4 0.83 255.87
HD 202206 c 2.44 2.55 1383.4

HD 217107 b 1.37 0.074 7.1269
HD 217107 c 2.1 4.3 3150

Mu Arae d 0.044 0.09 9.55
Mu Arae b 1.7 1.5 638
Mu Arae c 3.1 4.17 2986

Upsilon Andromedae A b 0.687 0.0595 4.617113
Upsilon Andromedae A c 1.98 0.832 241.23
Upsilon Andromedae A d 3.95 2.54 1290.1

Answer 2

Smallest Planet In Universe

Answer 3

Pluto is so old school! There have been more discovered beyond Pluto with more to come as astronomers begin peering further into the Kuiper Belt. There is Sedna (3/4 Pluto's size) and further out 2003UB313 with the purposed name Xena, which is found to have a companion - you got it - Gabrielle. At first - Xena was believed to be larger than Pluto - 105% - but more recently it has been found that Xena has a higher albeto than expected and therefore is actually smaller.

What makes up a planet is still a controversy. See reference below for a discussion of these planets and how planets are determined. Currently smallest planets we are able to see beyond our solar system is about the size of Neptune.

Most of the early ones discovered were larger than Jupiter - our largest planet - and closer to the main star. Recently - the measurements have been sensitive enough to detect more solar-like configurations where earth like planets could be present but not yet directly detected.

Answer 4

NOBODY...AND I DO MEAN NOBODY, can answer that question!!! The "Universe" is a vast and complex place. We live in a "galaxy" that is roughly 100,000 light-years in diameter. The "Universe" contains countless trillions of not multi "zillions" of "galaxies", many of which are much larger than our own galaxy, called the "Milky Way Galaxy". The "smallest PLANET?" Have you never read so much as this, that upon the Earth and even through our space-telescopes, NO OTHER "planet" has ever been directly observed because of the great and cast distances in our Universe. As a matter if FACT, Astronomers have utterly FAILED to even observe another "planet" right here in our own Galaxy...because they don't emit light and far too small for even our greatest telescopes to observe. Had you known these things which are factual, you wouldn't have asked your p-articular question....but nevertherless my friend, you're learning, and learning more with every passing day. Your question was a "good" question for someone who is just learning about our galaxy and universe...so keep up the good work and keep asking because, "THERE'S NO SUCH THING AS A STUPID QUESTION"...it's only the "answers" that are often stupid and without thought of consideration. Personally, I liked your question because it was at the very least, an HONEST question!!!

Answer 5

All the planets that have been found to-date in the universe are much larger than ours. This is mainly because we don't yet have a great way to find small planets, not that there are no other small planets. So, the best answer that can be given today is that Pluto is the smallest *known* planet in the universe.

Answer 6

Pluto is the ninth and smallest of the traditional planets of the Solar system, though its status as a planet has been disputed in recent years.

The story of how Pluto was discovered actually begins with the discovery of Neptune. In the 1840s, using Newtonian mechanics, Urbain Le Verrier and John Couch Adams had correctly predicted the position of the then-undiscovered planet Neptune after analysing the perturbations in the orbit of Uranus which could only have been caused by the gravitational pull of another massive planet. Thanks to their calculations, Neptune was discovered by Johann Gottfried Galle on September 23, 1846.

By the late 19th century, astronomers started speculating that Neptune's orbit too was being disturbed by another planet. By 1909, William H. Pickering and Percival Lowell had suggested several possible celestial coordinates for such a planet. In May 1911, the Bulletin of the Astronomical Society of France published the calculations of the Indian astronomer Ketakar which predicted a location for the undiscovered planet. Although Lowell died in 1916, the search for the elusive planet continued.

Pluto was discovered after an extensive search by the astronomer Clyde Tombaugh at the Lowell Observatory in Arizona on February 18, 1930 when he compared photographic plates taken on January 23 and 29. Tombaugh also referenced a lesser-quality photo taken on January 20 to confirm movement. After the observatory obtained confirming photographs, the news of the discovery was telegraphed to the Harvard College Observatory on March 13, 1930. The planet was later found on photographs dating back to March 19, 1915. Its mean distance from Earth and its mean daily motion turned out to be 39.48 AU and 14.283".

For more info see http://en.wikipedia.org/wiki/Pluto

Answer 7

Looks like we need to wait for the definition to be decided by the International Astronomical Union (IAU) this coming September 2006.

Meanwhile, Pluto is pretty much the lower bound of the size of a planet.

Definition of planet

The definition of planet has proven elusive despite the term being one of the best-known terms in astronomy. The term planet has existed for thousands of years, not only in science but as part of wider culture, applied in its long history to everything from divination to environmentalism. That the solar system consists of nine planets is a widely-held and often repeated idea.

To date, however, no actual scientific definition of the word "planet" exists. Until the beginning of the 1990s, there was little need for a definition, as astronomers had only a single sample within the solar system to work from, and the sample was small enough for its many irregularities to be dealt with individually.

However, since 1992 and the discovery of myriad tiny worlds beyond the orbit of Neptune, the size of the sample has risen from nine to at least several dozen. Following the further discovery of the first extrasolar planet beyond our solar system in 1995, the number of samples is now approaching hundreds.

These new discoveries have not only increased the number of potential planets, but, in their variety and peculiarity (some large enough to be stars, others smaller than our Moon) challenged long received notions of what a planet could be.

Pluto — Diameter: 2274 KM
Moon — Diameter: 3476 KM

The issue of a correct definition for planet came to a head in 2005 with the discovery of the trans-Neptunian object 2003 UB313, a body larger than the smallest accepted planet, Pluto. The International Astronomical Union, or IAU, which is the body responsible for resolving issues of astronomical nomenclature, has stated that it intends to release its final decision on the matter in September 2006.

http://en.wikipedia.org/wiki/Definition_of_planet

Answer 8

Considering we haven't discovered any planets outside our solar system smaller than Jupiter yet, then the smallest planet in our Solar System, and the known universe, is Pluto.

Answer 9

There's a quark in my toenail, which orbits the sun.

So I named it "Goofy" and declare it the smallest planet.

That's a goofy answer, but once something gets too small astronomers don't want to call it a planet any more. So you'll have to wait until they can agree on the smallest size for a planet. Good luck!

Answer 10

we cannot say which is the smallest planet but as far as we have discovered and conformed the smallest planet is pluto which is the smallest planet in our solar system
we have found some more planets like sedna etc but some scientists are saying that they are kuipier belt objects

Answer 11

The smallest planet in the universe???? There's only a gazillion of them. It would depend on your definition of "planet." Anything smaller than "x" orbiting a larger body is a moon. Or it could be a double-planet. Depending on your arbitrary limit of "x", anything smaller is an asteroid or meteor.