some rare facts about planets..!!

Ganymede

Largest moon in the universe.It belongs to Jupiter and it is larger than mercury.Second largest one is Titan(saturn) .It is the only moon in the Solar System to possess a significant atmosphere.

Kelvin–Helmholtz mechanism
The Kelvin–Helmholtz mechanism is an astronomical process that occurs when the surface of a star or a planet cools. The cooling causes the pressure to drop and the star or planet shrinks as a result. This compression, in turn, heats up the core of the star/planet. This mechanism is evident on Jupiter and Saturn and on brown dwarfs whose central temperatures are not high enough to undergo nuclear fusion. It is estimated that Jupiter radiates more energy through this mechanism than it receives from the Sun, but Saturn may not

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Puffy"cork" planet could float on water

Astronomers call it HAT-P-1b, but maybe we should call it Puff Daddy. A new study has spotted the puffiest planet anywhere, orbiting a star in another solar system.

Mercury

Mercury is the innermost and smallest planet in the Solar System,orbiting the Sun once every 87.969 days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about the axis for every two orbits .Mercury can only be viewed in morning or evening twilight.The first of two spacecraft to visit the planet was Mariner 10, which mapped only about 45% of the planet’s surface from 1974 to 1975. The second is the MESSENGER spacecraft, which mapped another 30% during its flyby of January 14, 2008. A final flyby took place in September 2009. MESSENGER is scheduled to attain orbital insertion around Mercury in 2011, and will then survey and map the entire planet.
Venus

Venus is the second-closest planet to the Sun.Earth's "sister planet" because they are similar in size, gravity, and bulk composition. Venus is covered with an opaque layer of highly reflective clouds of sulfuric acid, preventing its surface from being seen from space in visible light. Venus has the densest atmosphere of all the terrestrial planets, consisting mostly of carbon dioxide, as it has no carbon cycle to lock carbon back into rocks and surface features, nor organic life to absorb it in biomass.It is the solar system's brightest planet -- yellow clouds of sulfuric acid reflect the sun's light brightly.Ishtar Terra,the highest mountain on Venus, lies on Ishtar Terra.A long-standing mystery of Venus observations is the so-called Ashen light—an apparent weak illumination of the dark side of the planet, seen when the planet is in the crescent phase

Earth

Earth (or the Earth) is the third planet from the Sun, and the fifth-largest of the eight planets in the Solar System. It is also the largest, most massive, and densest of the Solar System's four terrestrial planets. It is sometimes referred to as the World, the Blue Planet,or Terra.
Home to millions of species, including humans, Earth is the only place in the Universe where life is known to exist. The planet formed 4.54 billion years ago

Mars

Mars has approximately half the radius of Earth. It is less dense than Earth, having about 15% of Earth's volume and 11% of the mass. Its surface area is only slightly less than the total area of Earth's dry land The red-orange appearance of the Martian surface is caused by iron(III) oxide, more commonly known as hematite, or rust.The shield volcano, Olympus Mons (Mount Olympus), at 27 km is the highest known mountain in the Solar System .It is an extinct volcano in the vast upland region Tharsis."Olympus Mons", the largest volcano found in the solar system.,

Ceres

Between Mars and Jupiter, is a Dwarf Planet known as Ceres.  It was discovered in 1801.  It is the smallest dwarf planet discovered in our universe (so far) and is the only one found in the asteroid belt.

Jupiter

Jupiter is so big that you could fit all the other planets in the solar system inside it.  The red spot of Jupiter is the biggest, most violent storm in the known universe -- that spot is at least three times the size of earth! Jupiter is classified as a gas giant along with Saturn, Uranus and Neptune. Together, these four planets are sometimes referred to as the Jovian planets.

 Saturn

Saturn is the second biggest planet, but it’s also the lightest planet.  If there was a bathtub big enough to hold Saturn, it would float in the water!The ring that surrounds Saturn could be the remnants of a moon that was shattered by Saturn's gravity.
Uranus

Uranus’ axis is at a 97 degree angle, meaning that it orbits lying on its side!  Talk about a lazy planet
Neptune

Neptune was discovered in 1846 (over 150 years ago).  Since that time it has still yet to make a complete orbit around the sun, because one Neptune year lasts 165 Earth years!

Like Jupiter, Neptune has a dark spot caused by a storm.  Neptune's spot is smaller than Jupiter's -- it is only about the size of the planet earth.

Pluto

Pluto’s orbit sometimes brings it closer to the Sun than Neptune.  It jumped ahead of Neptune on September 5, 1989 and remained there until February, 1999 when it went back to being the farthest.

Note:  Pluto is no longer considered a planet -- instead, astronomers call it a dwarf planet or planetoid.  Whatever the name, our solar system isn't the neat model we once thought it was.  It takes a bit for grown-ups (like me!) to adapt to the changes in our understanding (I now understand a bit better how folks felt when someone started telling them the earth was round not flat!)

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In January 2005, astronomers in the United States discovered a new body orbiting the sun in our solar system.  They named this planetoid, Eris after the Greek goddess of strife. 

Eris takes approximately 550 earth years to orbit the sun.  The majority of the time, it is further from the sun than Pluto, but for a short time, it is closer.

Eris is actually larger than Pluto (it is the ninth largest object orbitting our sun discovered so far!)

Makemake and Haumea are dwarf planets just like Pluto, but a little further out in our solar system.  Because their orbits are not perfect circles, they trade places in terms of which is closer and which is further from the sun.  

Both were discovered in late 2004/early 2005.

Haumea has a squished egg shape -- thought to be the result of a collision from an asteroid or meteor at some time.

 

 

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In 2004, astronomers in universities in the United States discovered a new body orbiting the sun in our solar system.  They named this planetoid, Sedna after the Inuit goddess of the Ocean.  This is the furthest orbiting body identified in our solar system to date.

Sedna is about three times further from our sun than Pluto.  It takes between 10,500 and 12,000 earth years for Sedna to make one orbit around the sun (we haven't quite figured out exactly how long it takes).