Mercury is the closest planet to the sun in our solar system. At first, scientists thought that the planet was very similar to the moon, but it is hard for them to observe Mercury because it is so close to the sun. When the first pictures of Mercury were taken on March 29, 1974, astronomers did in fact find features similar to the moon. Scientists were surprised at how many craters the planet has, which are similar to the other ones on all the planets and moons in the inner solar system. The scientists also found cliffs on Mercury. The planet is 4878 kilometers in diameter and takes 88 days to completely orbit the sun.
Venus is the second planet from the sun and the closest to Earth. It was the first planet to be explored. When scientists first looked at it in the 1950s, they thought the clouds were the surface. But when they had a chance to look through the thick clouds, they found a strange kind of volcano. Instead of the normal characteristics of a volcano, these had lava coming up out of the ground. Scientists called these “coronas”. Venus is 12,103 kilometers in diameter and its day is 243 Earth days, which is longer than its year.
Mars is the fourth planet from the sun. Viking 1, a U.S. spacecraft, landed on it in 1976. They found that the surface is similar to our deserts. Scientists are still wondering if there is water on Mars, which would mean that there is a possibility of life. It is thought that Mars had floods in its past. In 1978, after a major struggle, scientists did an experiment to find out if there was life on Mars; unfortunately, after a few trials, they found no life. Previously in 1971, scientists were disappointed with its surface. They thought it would be more exciting than the moon. However, when Mariner 9 was orbiting the planet, they saw a dust storm. When it calmed down, they found four huge volcanoes. Mars has the largest volcano in our solar system; it is called Olympus Mons after Mount Olympus. It is twenty-five kilometers high; the others aren’t much shorter. The length of a day in Mars is 24 hours and 36 minutes long. It takes 687 days to orbit the sun, and has a diameter of 6786 kilometers. It has two oddly shaped moons named Phobos and Deimos, which are 17 and 19 kilometers wide. Mars, commonly refered to as the “red planet,” lives up to its name because it actually is red.
Jupiter is the fifth planet from the sun. it started its formation like a star, but it didn’t become one because it didn’t take in enough gas. It has the most radiation of all the planets in the solar system. The planet has many moons; four in particular are Io, Europa, Callisto, and Ganymede. Linda Morabito, a scientist, found a volcano on Io and the pictures showed that the volcano was erupting. Io has volcanoes because of Jupiter’s gravity. It doesn’t have a circular orbit around the planet because Europa has a strong pull on it. Europa pulls on Io causing it to have an orbit shape unlike that of a circle. Scientists were surprised that Europa and Ganymede were without many craters. It is possible that Europa could have an ocean beneath its ice-covered surface. NASA is going to send spacecraft there in 2008. Callisto has the most craters of all the satellites in the solar system. Ganymede is the largest satellite in the solar system. Jupiter has a diameter of 142,980 kilometers and a total of 16 moons.
Saturn is the sixth planet from the sun. It has many rings surrounding it, and the space between two of the bands is called the Cassini Division. Many scientists believe that the planet’s rings came from a moon that it used to have. They say the moon somehow came too close to it, and its gravitational pull caused the oon to break apart into pieces, forming the rings. Saturn has 18 satellites, the most in the solar system. Titan is a special kind of moon because it has an atmosphere that is composed of methane and nitrogen and is very large. Saturn is the second largest planet in the solar system with a diameter of 120,540 kilometers.
Uranus is the seventh planet from the sun. William Herschel founded it in 1781; our solar system was previously known to have six planets. Uranus completely relies on the sun for its heat and is tilted so much on its axis that sometimes one of its poles faces the sun. It is 51,120 kilometers in diameter, takes 84 years to orbit the sun, and has 15 moons. Scientists were very frustrated with their little knowledge of the planet, so they were in search of another one past Uranus. This might explain why it has such an abnormal orbit around the sun. Later on, they found out that this strange orbit is due to Neptune.
In 1845, Couch Adams founded Neptune without a telescope. Many didn’t take him seriously because of the fact that he didn’t use a telescope, and he was so young. It is the eighth planet from the sun. Triton, one of Neptune’s moons, orbits it in the opposite direction than most other moons in the solar system. Like Jupiter’s Great Red Spot, Neptune also has a storm called the Great Dark Spot. The planet is 49,530 kilometers in diameter and has eight moons. It takes 165 years for Neptune to orbit the sun.
Pluto is the farthest planet from the sun. Scientists aren’t sure whether it is a real planet or not. Since Charon, Pluto’s only known moon is so close in size to it; Charon and Pluto could possibly be a two-planet system. Scientists didn’t know the planet existed until 1930. Since Pluto’s orbit is an ellipse, sometimes it crosses Neptune’s path, so for a few years, Neptune is actually the ninth planet in the solar system. Its diameter is 2280 kilometers and takes 248 earth years to go around the sun. There isn’t much known about Pluto because scientists have a hard time observing it from so far away.
The Moon is the closest object in space to Earth. It weighs about 70 billion billion tons and takes 27.3 days to go around Earth. We never see the far side of the Moon because it is lighter than the near side. Earth’s gravity is strong enough to keep the heavier side facing it. The Moon’s gravity also has an effect on Earth—it causes our ocean tides. Scientists theorized that the Moon is moving away from us at a rate of three centimeters per year; this is a little more than an inch. They believe that since it is moving away from us, our days are getting longer by 0.002 second per century. This would mean that millions of years ago, Earth’s day was 20 hours long. Galileo used to think that there were seas on the Moon; he called these “maria.” Then, they believed that instead of the maria being seas, they were flowing lava from underneath the Moon’s crust. Later on, astronomers found out that these maria were actually many craters on the surface of the Moon. They explained the maria as being “drier than any desert on Earth.” The Soviets were the first ones to have spacecraft land on the Moon. Their craft, Luna 2, plunged into it on September 15, 1959. They were also the first to take pictures of the opposite side of the Moon. Their spacecraft, Luna 3, sent back pictures in October 1959. The opposite side of the Moon doesn’t have many of Galileo’s maria (craters). American astronauts landed on the Moon on July 20, 1969. The first astronauts, including Neil Armstrong, were chosen because they were military test pilots.
Comets are composed of ice, gases, and dust. Astronomers have called them “large, dirty snowballs.” The movement of water molecules or hydrogen causes comets to form. One of the most popular comets is Halley’s comet, it can be seen every 77 years. Shoemaker-Levy 9 is also a well-known comet that hit Jupiter in 1994. Astronomers found a high amount of ammonia in Jupiter’s atmosphere; it is probable that this is due to the comet. It didn’t create much damage because Jupiter is made mostly of gases. The comet C/199954, also known as LINEAR, came about 35,000,000 miles from Earth. Astronomers believe that it came closer to Earth than most others. It is now located between Saturn and Uranus. Some were formed in the outer solar system, farther than Neptune. Comets would create more destruction if they hit Earth than if meteoroids or asteroids hit Earth because they move faster, but astronomers would have a greater chance of knowing that comets are approaching. They could know as far as a year ahead of time. An object as large as 100 meters wide can create a lot of damage!
Meteoroids are asteroids that are 100 meters in diameter or less. A meteoroid is called a meteor when it hits the atmosphere and a meteorite when it touches the ground. Scientists believe that a meteor that was 100 feet wide caused the Meteor Crater in Arizona. Meteoroids and asteroids are denser than comets. Scientists believe that there are 700,000 objects in the asteroid belt. Jupiter’s gravity is so strong that it doesn’t allow asteroids to become planets. Ida is a unique asteroid because it has a satellite orbiting it. Asteroids may break up into pieces, then called meteoroids.
Extrasolar planets were unheard of until 1995. Extrasolar planets are planets found outside the solar system. All of the known ones are huge and most of them are tremendously close to their star; this is hard for astronomers to comprehend. Scientists recently discovered an atmosphere of an extrasolar planet. They don’t believe it has life on it because it is made up of mostly gases and is very hot since it is so close to its star. Some of these planets have atmospheres because they have gravity. Gravity also causes their star to wobble. Scientists are surprised at their recent discoveries because the Hubble telescope wasn’t designed for that kind of observation. The first solar syster was found in 1999. At this time, astronomers discovered two planets that are 15 light-years away. The first one orbits the star in 30 days and the other 60 days. They also found another solar system that is 123 light-years away. It has one normal-sized planet and one huge planet. Because of all the solar systems that were found outside our own, some not mentioned, astronomers believe that there might be a possibility that ours is abnormal.
Astronomers previously had a hard time learning about astronomy until the invention of the telescope. Even then, their observations were limited until the telescopes improved. Astronomy is an ancient science. People have studied the stars for a long time and named most of the planets after Roman gods. Some constellations even acquired their names from mythology than many ancient people believed in. So, the next time you look at the clear sky during the night, think of what could possibly be out there and all the things that astronomers have yet to discover.
Quotes:
"Teach me your mood, O patient stars!
Who climb each night the ancient sky,
leaving on space no shade, no scars,
no trace of age, no fear to die."
- Emerson, The Poet
"Stars are like animals in
the wild. We may see the
young but never the actual
birth, which is a veiled
and secret event."
- Heinz R. Pagels, American Physicist
"Space isn't remote at all. It's only an hour's drive away if your car could go straight upwards."
- Sir Fred Hoyle
"Shoot for the moon. Even if you miss it you will
land among the stars."
- Les Brown
