Astronomy is the scientific study of celestial objects originated from outside Earth's atmosphere, including stars, planets, comets, and galaxies, and the universe as a whole. It is known as one of the oldest scientific studies.

Our Solar SystemSolar_System.htm

The solar system currently has eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Pluto, formerly the ninth planet, recently lost it's status as a plant because it was so small. The solar system also contains other objects that float in space, such as meteoroids, comets, dwarf planets, and cosmic dust. All of the objects in the solar system orbit the sun. The sun is so big, all other objects could fit inside a numerous amount of times. The four inner planets (Mercury, Venus, Earth, and Mars) are generally very rocky and relatively small. The last four (Jupiter, Saturn, Uranus, and Neptune) are made mainly out of gas, and are a lot larger. Between the two planets Mars and Jupiter, there is an asteroid belt, which is consists of millions of irregularly shaped asteroids that also orbit the sun. Scientists believe our solar system is more than 4.6 billion years old.


Mercury is the first and smallest planet in the solar system. It is the closest planet to the sun, and was named after the Greek god of commerce, thievery, travel, and messages, Hermes. The diameter of Mercury in about 3,032 miles at the equator, and it orbits the sun nearly once every 88 days. Its orbit is that of an oval shape. It has no moons, and takes 58.6 days to rotates, which is longer than any other planet except Venus. One day on Mercury would be about 176 Earth days. Mercury's surface is much like Earth's moon, with the craters and smooth plains. The largest known crater is the Caloris Basin, with a 300 mile diameter. Mercury's poles contain ice, because the basins are shielded from sun so they can't melt. The temperature has extreme variations, getting as hot as 840 degrees Fahrenheit and as cold as -275 degrees Fahrenheit. Plant and animal life most likely do not exist because of its intense heat and low oxygen supply.


Venus is the second planet closest to the sun, and sits between Mercury and Earth. It was named after the Greek goddess of love and beauty, Aphrodite. The planet has no moons, and is covered with a thick layer of clouds. These thick clouds create a "greenhouse effect" that makes it very hot. It is about 7,519 miles in diameter, and the temperatures range between 900 degrees Fahrenheit to -50 degrees Fahrenheit. Venus is about 25,998,792 miles from Earth. Its atmosphere is about 95% carbon dioxide, and the other 5% is made up of nitrogen, sulfuric acid, and traces of other elements. The surface is rocky, with lots of dust and no water, with a 200 mile long river of lava running through it. One day lasts about 243 Earth days, and it takes about 225 Earth days to rotate around the sun, meaning one day is longer than one orbit around the sun. The planet is the brightest object in the sky besides the sun and the moon. It spins from east to west, which is the opposite of Earth.


Planet Earth is about 7,953 miles in diameter. It is the third planet from the sun and the fifth largest planet in the solar system. It is the only planet of the eight planets not named after a Greek god. The atmosphere is about 78% nitrogen, 21% oxygen, and the remaining 1% is made up of argon, carbon dioxide, hydrogen, helium, and methane. Earth has one moon, simply named "the moon". One rotation around the sun lasts 365 days, and one day lasts 24 hours. Water from oceans, seas, rivers, etc. cover 71% of the surface. It is estimated to be more than 4.5 billion years old.


Mars is the 4th planet from the sun, and is the only planet whose surface can be seen in detail from the Earth. It was named after Ares, the Greek god of war. This planet has two moon, Phobos and Deimos. It only takes about 24 hours and 37 minutes to fully rotate, and the temperatures vary from 60 degrees Fahrenheit to -220 degrees Fahrenheit. Its diameter is about 4,223 miles, and its atmosphere is made up mainly of carbon dioxide.


Jupiter is the largest planet in the solar system. It has at least 39 moons, including Europa, Io, Callisto, and Ganymede. It has a diameter of 88,736 miles, and if the planet was hollow, it could fit more than one thousand planet Earths inside. Jupiter has a faint ring system, but it can't be seen from Earth. The atmosphere is made up mainly of hydrogen and helium, with small amounts of methane, water vapor, ammonia and other compounds. The planet is commonly known for the Great Red Spot. The Great Red Spot is a giant storm constantly moving in a counter-clockwise rotation on the planet. Jupiter was named after the Greek god of all gods and thunder, Zeus.


Planet Saturn is the second most massive planet in the solar system. It also has a ring system like Jupiter, which shares a lot of characteristics with Saturn, but Saturn's rings are much more intricate, and are made up of billions of ice particles. It is named after Cronus, the ruler of the Titans, and the father of the Greek gods and goddesses. The planet has at least 31 moons. Some of these moons include Titan, Hyperion, Mimas, Enceladus, Rhea, and Phoebe. The diameter is about 74,974 miles across. Its atmosphere consists of hydrogen and helium and the surface is made up of liquid and gas. It takes about 10 hours and 40 and a half minutes to rotate and 29 and a half years to orbit around the sun.


Uranus is the seventh planet from the sun, and also the third largest planet. It has a diameter of 32,190 miles. This planet orbits the sun about every 89 Earth years, and rotates in about 17 hours and 14 minutes. It has 27 moons, its largest largest being Titania, Miranda, Ariel, Umbriel, and Oberon. Uranus's atmosphere is made up of about 83% hydrogen, 15% helium, and 2% methane, with the small traces of acetylene and other hydrocarbons. The planet is easily distinguished by its tilted appearance, believed to be caused by getting hit by a massive sized object. Uranus has thirteen rings, all darkly colored and hard to see through. Scientists say the rings are made out of water ice mixed with organic molecules and, unlike Saturn, Uranus's ring are very thin, measuring only 4 or 5 miles wide. The planet was named after the Greek Titan of the sky, Ouranus.


The planet Neptune is the last and farthest planet from the sun. It is named after the Greek god Poseidon, god of the sea and earthquakes. The planet had a diameter of 30,760 miles across, and if it were hollow, it could fit about 60 planet Earths inside. Neptune orbits the sun every 165 Earth years, and one complete rotation lasts 16 and a half hours. The strongest winds on any planet were found on Neptune, measuring 1,200 miles per hour near the Great Dark Spot, a constant moving storm much similar to Jupiter's Giant Red Spot. The planet has four sets of rings, made out of dust that are very narrow and faint.

Dwarf Planetsdwarf_planet_sizes_sm.jpg

In 2006, the International Astronomical Union declared a new classification system for objects in space: small solar system bodies (asteroids and meteors), larger planets (Earth, Saturn, etc.), and the in-between sized dwarf planets. The dwarf planets category has 5 official planets. Pluto, Ceres, Eres, Makemake, and Haumea.


Pluto used to be one of the nine planets in our solar system, but was recently classified as a dwarf planet, so it is no longer a planet in the solar system. It is usually the farthest planet from the sun out of the original nine planets, but for 20 years of every 249 year orbit around the sun, it is closer than Neptune. It is estimated that this will not happen again until September of the year 2226. The dwarf planet's rotation time is just under 6 and a half earth days. The surface of Pluto is 98% nitrogen, with small traces of methane and carbon monoxide also present. It has one moon, Charon, which is about equal in size.


Ceres is the largest asteroid in the asteroid belt between Mars and Jupiter, and also the first, therefore classifying it as a dwarf planet. It was found on January 1st, 1801, by G. Piazzi. It's diameter is about 590 miles wide. It was considered a planet, until 2006, when Pluto was stripped of it's name as a planet, also claiming Ceres as a dwarf planet.

Eris and Makemake

Eris and Makemake orbit the Sun along with Pluto on the outer skirts of the solar system and are frozen because they are so far away. In July of 2005, Eris, first named UB313, was found. It is larger than Pluto, with a diameter of 1,850 miles, and is classified as the largest object found to orbit the sun since Neptune and its moon was found in 1846. Makemake, originally known as 2005 FY9, was discovered in late March in 2005. It is the third largest object classified in the category of dwarf planets, and is about one third of the size of Pluto.


Haumea is a dwarf planet in the Kuiper Belt. Like Makemake, it is about one third of the size of Pluto, and was discovered in 2004. From the Sun, it is about 50 times the distance of the Sun and Earth. On September 17, 2008, it was officially considered a dwarf planet.


The Sun

The sun is the largest object in our solar system. It could hold about 1.3 million planet Earths inside. It contains 98% of the solar system mass. The outer surface itself is 11,000 degrees Fahrenheit. In the core, the temperature reaches 27,000,000 degrees Fahrenheit. Since the Sun has been burning for 4.6 billion years, scientists believe it will continue to burn for another 5 billion years. Then it will start to swell up from the helium changing, getting so large that it will swallow up the whole Earth. It will then change from a red giant to a white dwarf, and then finish the process like a regular star would.


moon_phases_diagram1.jpgMoons are small objects that resemble tiny planets that orbit the real planets. They are usually smaller than the original planet they orbit. Some planets can have no moons, a couple moons, or a large number of moons. Mercury and Venus are the two planets that have no moons, and Earth is the only planet that has just one moon. Mars has two moons, Phobos and Deimos, which are both very small compared to Earth's moon. Jupiter has at least 63 moons, Saturn has 61, and Uranus has 27. Neptune has 13 moons. Dwarf planets also have moons. Pluto has 3 moons, the most well know is Charon.
When a moon orbits the planet, it goes through a cycle of different phases. There are a total of eight phases. The first phase is called the "new moon," and you cannot see it. Next, you have the "waning crescent," and then the "first quarter," also known as the half moon. The fourth phase is called the "waxing gibbous," and the next one is the "full moon," where you can see the whole moon. After that is the "waning gibbous," and then the "third quarter," which is also known as a half moon, but you see the opposite side of the first quarter. The last phase is the "waning crescent," and then the cycle starts again beginning with the new moon.
Moon Phases

Comets, Asteroids, and Meteors


Comets are celestial bodies that move around space and revolve around the sun. They are distinguished by their long tails. A common nickname for these are dirty snowballs, because the round objects are covered in dust and ice. When heading towards the sun, the heat evaporates causing the ice to brighten, which forms the long tail that can sometimes be millions of kilometers long in space. The most well known comet is Comet Halley, named after British astronomer Edmund Halley, who calculated the comet's orbit. The next return from this comet is predicted to be in 2061.


Asteroids are minor planets, also known as planetoids.
Asteroid belt
Three of the largest planetoids are Ceres, Pallas, and Vesta. Scientists believe some asteroids are part of where a planet should have been, but couldn't form because Jupiter's gravity prevented it. The asteroid belt is very well known. It is a section between the inner planets and outer planets filled with thousands of asteroids that orbit the sun.


Meteors are chunks taken off of asteroids or other planets. Often, they are the size of baseballs, flying 30,000 miles per hour through space, though sometimes they can be larger or smaller. The smaller meteors are usually dust from passing comets. Meteors are well known for their meteor showers. They are well known for their bright lights, which is caused by them entering Earth's atmosphere and getting heated up. A great number of meteors are destroyed during meteor showers, but those that make it to Earth are known as meteorites.

Northern hemisphere constellations

A constellation is a group of brightly lit stars that seem close together from Earth's surface, but are actually far apart in space. The pictures you see depend on your point of view, but often they are named after Greek gods, goddesses and heroes from long ago. Two popular constellations would be the Big Dipper and the Little Dipper, which are part of the Ursa Major and Ursa Minor in the Northern Hemisphere. There are 88 constellations as of 2010. The grouping of the constellations are not entirely relevant. To people on Earth, they look like they are placed right next to each other, but really, they are miles and miles away from each other. They only look like they are next to each other because the stars of each individual constellation are all pointing the same way.


The Milky Way
Galaxies are groups of stars, dust, and gases held up by gravity. Our solar system is in the middle of the Milky Way, one of more than 100 billion galaxies in the universe. Some galaxies that have been recorded are nearly 10 billion to 13 billion light years away. A single light year is just under 6 trillion miles long. The smallest galaxies haves less than one billion stars, the largest ones have more than one trillion stars.
Besides the Milky Way, only 3 other galaxies can be seen with the naked eye: the Small Magellanic Cloud, which is 160,000 light years away from Earth; the Large Magellanic Cloud, which is 180,000
light years away; and the Andromeda Galaxy, 2 million light years from Earth.

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