A Planetary Guide to Outer Space!
When you look at the sky at night what do you see? People who are in the country, away from city lights, can see more in the sky than people who are in the city. Everyone can usually see some stars if the night is not cloudy. Yet the view of the night sky for people in the city is not as clear because of light pollution. A glow in the sky is created by city lights which can mask many of the stars. When you look at the night sky you might see constellations and bright planets. You may also see a brief flash of light from a meteor or an artificial earth satellite moving slowing across the sky. If you are really lucky and in the right place at the right time, you might be able to see the northern lights which appear as beautiful colors in the sky.
You can find many different kinds of stars in the night sky. Some are extremely large including several that are 100 to 200 times bigger than the Sun. There are also a few very old stars that Earth is larger than. Scientists like to study the stars and they place them into groups depending on their similarities and differences.
The most common type of star by far is the red dwarf, but you won't actually see many of them because they are very small and not very bright. This type of star is smaller than the Sun and has less mass. These stars burn fuel very slowly because they are so small which means that they live for a very long time. Yet this also is the reason these stars do not shine as brightly as other stars. Some red dwarfs will actually live for trillions of years before they run out of fuel. They are not very hot when compared to other star types. Imagine a flame. The coolest part of the flame is the top of it which burns red. The middle part of the flame glows yellow and is hotter. The hottest part of the flame glows blue and is closest to the fuel. Just like a flame the color of stars is also determined by their temperature.
Yellow stars are medium in size and temperature. Due to their higher temperature than a red dwarf they burn fuel faster so they do not live as long. They only live for about 10 billion years. Near the end of their lives they swell up and become extremely large. They eventually shrink back down but leave most of their gases behind. These gases create a beautiful cloud surrounding the star which is called a planetary nebula.
A blue giant star is very large but also compact which makes them burn their fuel quickly. This makes them very hot and very bright. They are actually rare stars but because of their brilliance they are many of the stars you typically see at night. Blue giants usually run out of fuel in a mere 10,000 to 100,000 years. When they die, blue giants grow bigger and explode into what is called a supernova. These explosions can be brighter than a whole galaxy and can be seen from great distances.
Another type of star you often see in the night sky is a giant star because they glow very brightly. As a star the size of the sun gets old, it starts to run out of hydrogen fuel. The process of burning hydrogen in the star's core begins to slow which causes the core to become more dense and compact. The center begins to heat up again as it becomes smaller in size. The core starts burning a new fuel, helium, when it gets to a certain size. When helium is ignited it burns much hotter than hydrogen. The additional heat makes the star much bigger because it pushes the star's outer layer farther out.
A super giant star is exactly the same thing as a giant star but is even larger. Blue giant stars eventually start to burn helium which makes them hotter. The extra heat stretches the outside of the star. Size is the only difference between a giant and a super giant star. A dead super giant (or blue giant) star often becomes a black hole.
Did you know that the solar system contains over 100 worlds? You probably already know about the eight main planets but there are also minor planets and moons. Some of these are bigger than Mercury. The minor planet Io has active volcanoes while Europa (another minor planet) has an ocean of liquid water. Titan (yet another minor planet) has rivers, lakes and oceans which are comprised of liquid methane. The solar system consists of planets orbiting our Sun as well as comets, asteroids, moons, minor planets, gas and dust. Everything revolves around the Sun which contains 98 percent of all of the material that is in the solar system. The bigger an object is the greater the gravity that it has. The Sun is very large so all of the other objects in the solar system are attracted toward its gravity. While being pulled toward the Sun these rapidly moving objects are also trying to move away from the Sun toward outer space. Due to the opposing forces, the objects become trapped in between the Sun and outer space. For eternity they orbit their parent star.
The solar system is divided by an asteroid belt into inner and outer solar systems. The inner system consists of Mercury, Venus, our Earth and Mars. The outer system contains Jupiter, Saturn, Uranus, Neptune (and Pluto although it is no longer considered a planet). All the planets circle around the Sun in the same direction.
Mercury is the closest planet to the Sun and the eighth largest of the planets. It is small, rocky and covered with craters. It doesn't have moons. You can actually see Mercury in the night sky either through a pair of binoculars or with your naked eye.
The next planet is Venus which is second from the Sun and the sixth largest planet. It is also a small and rocky planet which is surrounded by a thick yellowish cloud layer of poison called sulfuric acid. Venus's surface is very hot so rain cannot form. It also has no moons. A large amount of the surface area is covered by lava flows. There are many large volcanoes on Venus. It is the brightest star in the night sky and is typically visible to the naked eye.
Our planet, Earth, is the third planet from the Sun and the fifth largest planet. It is small and rocky and can support many varieties of life. It is also the most compact major body in the solar system with a very hot core. One moon orbits Earth. Approximately seventy-one percent of the Earth's surface is covered by water. It is the only planet where water is able to exist on the surface in liquid form. Seventy-seven percent of Earth's atmosphere is nitrogen along with 21 percent oxygen and traces of carbon dioxide, argon and water.
Mars is the seventh largest planet and fourth from the Sun. It is a cold, rocky and lifeless planet. It has permanent ice caps at both of its poles. There are very strong winds and huge dust storms that will blow across the entire planet and continue for months. Two very small moons orbit Mars very close to its surface. These moons are called Phobos and Deimos. Mars has the largest mountain in the entire solar system called Olympus Mons. It is also consists of craters, canyons and bulges. It can easily be viewed by the naked eye, but its brightness depends on its location relative to Earth.
Jupiter sometimes is the brightest star in the night sky as well as the fifth planet from the sun. It is without a doubt the largest planet in the solar system. If you combine all of the other planets Jupiter is more than twice that size. It is considered a huge gas planet which is comprised of 90 percent hydrogen and 10 percent helium. This planet actually has 16 known moons. Four of the moons are big Galilean moons and 12 are small ones. Jupiter does not have a solid surface. The bands and swirls that people see on it are cloud tops which are high in its atmosphere. Very strong winds of greater than 400 miles per hour blow on this planet. It is well-known for its “Great Red Spot” which is oval in shape and is a high-pressure area where the tops of the clouds are colder and higher than surrounding areas. Jupiter has rings that are dark and faint. The four big moons of Jupiter are easily visible with binoculars. You can also see some of its bands and the Great Red Spot if you use a special telescope.
Saturn is known for its beautiful rings. It is the second largest planet and sixth from the Sun. It is a huge gas planet consisting of 75 percent hydrogen and 25 percent helium. Saturn has 18 known moons which is more than any of the other planets. It also has bands and long-lived spots (where large storms are occurring). Its thin rings are very bright and consist of lots of tiny particles which circle the planet at their own speeds and vary in size. Saturn is easy to see in the night sky with the naked eye (planets don't twinkle like stars) and its bigger moons and rings can be seen with an astronomical telescope.
The third largest planet is Uranus which is seventh from the Sun. It is also a big gas planet consisting of mostly rock and different ices. It appears to spin differently than the other planets. It seems to tilt versus spinning right-side up. There are 15 known moons surrounding Uranus. It has dark rings consisting of fairly big particles. The Epsilon rings is its brightest ring out of 11 known rings. On a clear night it is sometimes barely visible to the naked eye. You can often see it through binoculars if you know where you need to look.
Neptune is a big gas planet which is the fourth largest planet but is heavier than Uranus. It can be either the eighth or ninth planet from the Sun depending on Pluto. Pluto sometimes crosses in front of Uranus during its orbit of the Sun. Neptune appears blue because of methane in its atmosphere. It has the fastest winds in the entire solar system which are sometimes as great as 2000 kilometers per hour. Neptune has eight known moons including one big one (Triton) and seven small ones. It has large storms on it and also has faint, dark rings. If you know exactly where to look in the night sky you may be able to see it with binoculars. You would be able to see it much better with a large telescope.
Finally there is Pluto which is no longer considered a planet. It is now believed to be a dwarf planet. It is typically the farthest planet from the Sun, but as stated earlier, will sometimes cross in front of Neptune changing its position. It is a very small planet which is even smaller than seven of the moons in the solar system. It is an icy planet with one moon called Charon. It appears to be lying on its side. It is a very difficult planet to see. You need to observe the night sky for several days before your viewing, use detailed charts and an amateur telescope in order to hopefully see this planet.
The universe consists of clouds, stars, dust, gas, galaxies and life. Matter is organized into strings or strands. Earth orbits the Sun which revolves around the galaxy's center. A group of galaxies referred to as the Local Group includes our galaxy. The Local Group of galaxies is part of the larger galaxy cluster referred to as the Virgo Cluster. All of the millions of galaxy clusters in the universe string together and resemble a spider web.
What does a black hole do? It uses gravity to clean up outer space debris. When a big star gets old and runs out of fuel it can no longer support its heavy weight. There is pressure from the huge hydrogen layers of the star which make the star become smaller in size. It will become eventually smaller than an atom. The squishing of the star makes its gravity stronger. The gravity of a black hole becomes so powerful that even light can be pulled in if it gets too close to it. There are three main parts to a black hole. The “Outer Event Horizon” is its outer layer where gravity is least powerful. You could still escape if you got pulled only into the outer layer. The black hole's middle layer is referred to as “The Inner Event Horizon” and if you didn't escape before you got to this point gravity is too strong here to let you go. “The Singularity” is the name for a black hole's center. This is the part of the hole where gravity is the most powerful.
There are two black hole types which include stellar-mass black holes and supermassive black holes. Stellar-mass black holes are three to 15 times bigger than the Sun. When a giant star attains old age it explodes into a bright light burst called a supernova. The giant star has stopped burning its fuel. Material is typically left over from a supernova and it is referred to by scientists as stellar remnant. This collapses in on itself and becomes very compact. Now a stellar-mass black hole emerges. The second type is the supermassive black hole which is much larger than stellar-mass holes. Even if the Sun became a black hole Earth would not get sucked into it because our planet is too far away from the horizon of this black hole. The gravitational pull would not reach Earth.
Did you know that galaxies can pass right through each other? It is safe for this to happen because stars are very far apart and it is highly unlikely they will collide. The universe is filled with billions of galaxies. Some galaxies are small with merely a few million stars while other galaxies can have as many as 400 billion stars or more. Three types of galaxies exist which differ by their shape.
The most beautiful galaxies are spiral which have long and twisting arms. It is in these arms of circling waves that stars are being created. Some newly formed stars are very big which makes them glow brighter and makes the dust clouds nearby brightly glow. Any area which is near to one of these waves will glow like a fluorescent light. You cannot actually see these waves. The spirals that are visible are merely glowing clouds which are being lit up by the big, hot stars. As the waves continue to move the clouds behind them become less bright and stop glowing until a new wave passes through. The bright, big stars that are formed in the waves do not live long. Their size makes them burn their fuel quickly. They typically die before ever getting to leave the wave. The small stars that do not glow as brightly are the ones that get to leave the waves where they were created.
Elliptical galaxies are usually very old. They do not actively create new stars so the only stars that are in them were created a long time ago. Typically this type of galaxy is smaller but they can also be big. The average elliptical galaxy only has several thousand stars yet there are some which have billions of stars.
If a galaxy is not a spiral or an elliptical it is considered an irregular galaxy. Its appearance can resemble anything and it can have a large variety of characteristics. There are probably many irregular galaxies that used to be a spiral or elliptical galaxy but had an accident which altered it. For example, it could have endured a crash with another galaxy. There are also many other irregular galaxies which were never a spiral nor an elliptical. Most of the galaxies in the universe are clumped into small groups as our galaxy is referred to as the Milky Way Galaxy. This galaxy is located within a group of galaxies called the Local Group. There are approximately 30 galaxies in The Local Group with the largest ones including: The Andromeda Galaxy, The Milky Way Galaxy and Triangulum. Outer space is huge and scientists will continue to constantly learn new things about it.
Your Sky Tonight Star Charts: This website by PBS provides you with a star chart according to your time and location that you can print out and use to identify what you are looking at.
Stars: This excellent and very kid-friendly site provides information on stars as well as the universe, the solar system, black holes, galaxies, nebulae and quasars.
The Nine Planets Just For Kids: This fun and colorful website discusses the solar system and the nine planets.
Black Holes FAQ: This article talks about black holes as well as white holes and wormholes.
Solar System: A great website with information on the solar system as well as the Sun and the major planets.
Our Solar System: The website by NASA discusses many different topics such as the eight planets, dwarf planets, comets and asteroids among numerous other things.
Solar System by National Geographic: The website offers great information on our solar system including moons, rings and magnetospheres.
Stars and Galaxies: This fun website discusses the story of the universe, the Sun, supernovas, The Milky Way and many other things.
The Constellations and Their Stars: The article explains what constellations and stars are and provides interactive star charts and lists such as the brightest 26 stars.
Stars by the BBC: The website discusses stars and offers TV clips on many astronomy subjects such as The Crab Nebula and The Constellation Orion.
Galaxies: This excellent website provides information on the different types of galaxies as well as galaxy evolution, interactions and mergers.
Galaxies by the Institute for Astronomy: The article discusses dwarf galaxies and starbursts and offers other articles on the Sun, the solar system and other topics.
Types of Galaxies: The article offers great pictures of different galaxies and explains the various types.
Ask an Astronomer-Galaxies: The article answer numerous questions regarding galaxies.
Black Holes Gravity's Relentless Pull: This website offers a “Journey to a Black Hole” and a “Black Hole Encyclopedia.”
All About Astronomy-The Planets: Enchanted Learning is a great site for kids and provides information on the entire solar system.
Black Holes: The article offers a lot of information on event horizons, the speed of light, singularities and black hole acceleration among other topics.
No Escape: The Truth About Black Holes: The website discusses if a black hole is truly a hole.
What Are Stars Made Of?: The site explains what stars are made of and provides pictures.
Planets For Kids: This fun and colorful website provides information on the planets, stars, moons and other asteroids.
The Dark Side of the Universe: The article discusses the universe, gravity and related terms.
Milky Way Galaxy: The website talks about the Milky Way Galaxy and other galaxies as well as many other astronomy topics.