Astronomy is the study of space and everything in it, including Earth. Scientists argue over what its the exact study of. Some think its the study of everything because space has everything in it. Others say its the study of celestial bodies.

A supernova is a star that explodes. It can create a light one thousand times brighter than the sun.


Comets are part of astronomy. The longest comet tail ever recorded was 354 million miles long. That is bigger than the Earth itself. It belonged to comet Hyakutake in May 1996. NASA classifies comets by how long they take to orbit around the sun. Short-period comets take less than 200 years. Long-period comets take longer than 200 years to orbit around the sun. The nucleus of a comet is a ball of ice or rock. The ice consists mainly of frozen water, but might contain frozen ammonia, carbon dioxide, carbon monoxide, and methane. As it nears the sun, the rock and ice melt or break off to form the dust tail of the comet. Comas, the dust tail of the comet, can reach 10 million miles long or longer.


The sun is what keeps us alive. Without its light and heat, we would all freeze. Believe it or not, its only considered an average size star.
The sun formed about 5 billion years ago from a mass of dust and gas. The sun's core converts 700 million tons of hydrogen into 695 million tons of helium.
The remaining 5 million tons are converted into an amount of pure energy that's about 600 times greater than the amount of water in Niagara Falls. Light, which travels at 186,000 miles per second, takes about 8 minutes to reach Earth from the sun. The sun's outer atmosphere is called its corona, and its inner atmosphere is its chromosphere



mercury.jpgThe closest plant to the sun is mercury, and is also the eight largest planet. It was named after the Roman god Mercury, who is the Roman counterpart of the Greek god Hermes. Mercury rotates once every 159 Earth days. Mercury's surface is comparable to the moon's. Both Mercury and the moon's surface are also covered by silicates in the tiny form of particles. The atmosphere of Mercury is dry, extremely hot, and almost airless. Many scientists believe that there was no possible way that life ever existed on Mercury. Its average temperature during the day would be somewhere around 840 degrees F, while it would get as cold as -275 degrees F at night.


external image moz-screenshot.pngvenus.jpeg Venus is the second closest planet to the sun. Venus was named after the Greek god Aphrodite for its brightness and beauty. Venus, an inferior planet, shows phases when looked at from Earth. Venus's rotation is unusually slow (243 Earth days per Venus day). Venus is also considered Earth's sister planet, because they both have a few craters indicating young surfaces, Venus is just a little smaller than Earth, and the densities and chemical compositions of each are similar. Venus has many different gases in its atmosphere, including a layer many kilometers thick of sulfuric acid. These clouds make it impossible to see Venus's surface from here.


earth.jpeg Earth is actually the third closest planet to the sun, and we live on it. The Earth is approximately 4.6 billion years old and it's the fifth largest planet in our solar system. The Earth's surface is about 70% water. The Earth also has an average diameter of 12,742 kilometers. The estimated temperature of the core is between 5000 and 7000 degrees Celsius. Earth is actually not a complete sphere, because of its rotation the equator bulges out a little. Earth takes 23 hours 56 minutes and 4 seconds to rotate once around its axis. A year is 365.2564 days long. Its the .2564 that creates the need for a leap year. The Earth's axis tilts about 23 1/2 degrees, which causes the different seasons. The Earth is made mostly of iron, oxygen, silicon, and magnesium.


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mars.jpeg Mars is the fourth closest planet to the sun. Mars is named after the Roman God of War, which in Greek was named Ares. Viewed from Earth, Mars has a reddish-orange look, which the ancient civilizations referred to as the color of blood. Scientists have found evidence that water used to flow on Mars' surface. We have also found tons of ice in the south pole of Mars, along with channels, rivers, and other waterways. Some scientists have found evidence they believe had once supported life on Mars, but most scientists are not convinced. Mars also has deeper canyons and taller mountains than Earth. Mars has an atmosphere 100 times less dense than Earth's.


jupiter.jpgJupiter ​​is the fifth closest planet to the sun and is also the largest planet in our solar system. Its diameter is more than 11 times the size of Earth's. Jupiter is 483,780,000 miles from the sun. Jupiter is literally a ball of gas surrounding its barely solid core. The giant red spot on Jupiter's surface is believed to be a raging storm that never quits, but scientists don't know what caused it. The color of the clouds that circle Jupiter are red, brown, yellow and white. Jupiter also has liquids on its surface, but it wouldn't be solid enough to stand on. Jupiter rotates around its axis in 9 hours and 56 minutes. Jupiter also sends out radio waves strong enough to be picked up by our radio telescopes, which help us determine Jupiter's rotational speed. Jupiter is heavier than any other planet, but its density is barely more than the density of water.


saturn.jpgSaturn comes right after Jupiter, which means its the sixth closest planet to the sun. The most interesting feature about Saturn is its seven rings. These rings are made of ice crystals, which orbit the planet. The widest one is 180,000 miles across, but so thin that looking straight at it, nothing is seen. Saturn is also the second largest planet in the solar system, its diameter being ten times bigger than Earth's. Saturn also has the second shortest day at 11 hours. This rapid rotation causes the middle part of the planet to bulge, causing its poles to flatten. It also is a all of gas except of a hot, metallic core. Its surface is believed to be mostly composed of ammonia, methane, and water. The planet gives off more than 2 1/2 times the heat it receives from the sun. It is believed to be caused by the sinking helium going through layers of hydrogen.


uranus.jpeg Uranus, the second last planet from the sun, is very unique from the other planets. It takes light 2 hours and 40 minutes to reach Uranus. Uranus is a ball of gas and liquid, with a rocky core about the size of Earth's. The atmosphere of Uranus is made of frozen crystals of methane, and below is probably thicker clouds made of liquid water and crystals of ammonia ice. The surface of Uranus is made of 83 percent hydrogen, 15 percent helium, and 2 percent methane, along with a little of other gases. There may be an ocean of liquid water containing dissolved ammonia on the surface of Uranus. Scientists think that the cause of why Uranus is tilted is because a rock of some sorts hit Uranus when it was still forming. Uranus's axis lies almost in a straight line to the sun. The gravity of Uranus is 9/10 of what it is on Earth. The temperature of the atmosphere is -355 degrees F, the ocean is 4,200 degrees F, and the core is 12,600 degrees F.


neptune.jpeg Neptune, the last planet from the sun since Pluto is no longer a planet, has a blue look because of the clouds of frozen methane on its outskirts. Clouds closer to the surface are composed of hydrogen sulfide. Neptune's year is 165 Earth years, but has a shorter day, only 16 hours and 7 minutes. Neptune is primarily made of hydrogen, helium, water, and silicates. Thick clouds made of heavily compressed gases surround Neptune. Winds are another well-known fact about Neptune, which blow these clouds at about 700 miles per hour. In 1989, the Voyager 2 had captured a great dark spot resembling a hurricane on Neptune's surface, but in 1994 the Hubble telescope fund it had vanished. Neptune has a strong enough gravity to affect Uranus's orbit, which was how Neptune was found in the first place. Triton, Neptune's biggest satellite, or orbiting rock, was probably a comet that was caught in Neptune's gravity force. Neptune also has rings composed mostly of dust, because they are so thin sometimes they can't be seen.


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