Learn about stars and galaxies.

 Our Solar System - Have you ever looked up into the sky and wondered what was there?  Higher than the birds, past the clouds, and farther than the moon, a whole host of fascinating objects spin in outer space. Let's imagine for a moment that we can leave the earth behind, and explore the solar system that surrounds it. We call it the solar system because everything in it is centered around the sun, and solar means something to do with the sun.  The Sun  The sun is a star, just like many of the stars that you can see in the night sky - just many times closer to us. Still, the sun is very, very far away from the earth; almost 93 millionmiles away: that's why it looks so small, even though it's the biggest object in the solar system. In fact, the sun makes up more than 99 percent of the mass in the solar system.If you put all of the planets, moons, asteroids, comets, and everything else in the solar system together, they would make up less than one quarter ...

 While billions of stars are scattered throughout the universe the one at the center of our solar system Plays a special role for us here on earth. Our Sun formed about 4.5 billion years ago in the Milky Way galaxy's Orion's fur. It was born when a cloud of dust and gas known as a solar nebula Collapsed and in the middle of this formation matter condensed into a burning ball of gas that became our Sun.   The sun's fiery nature along with a tremendous gravitational pull and an extensive magnetic field Helped it to become the heart of our solar system. The Sun can be divided into six layers or regions the corona the chromosphere the photosphere the convective and radiative zones and the core in terms of atom count.   The Sun is about 91% hydrogen the sun's fuel eight point nine percent helium and point one percent heavier elements such as carbon and nitrogen. Due to the sun's extreme temperatures these elements stay in a gas like phase called plasma. I...

 When Pluto was discovered in 1930, it was named the ninth planet of the solar system. More than seventy-five years later, that planetary status was revoked and Pluto was demoted to a dwarf planet. Many people were left wondering what changed,and what the difference was between a planet and a dwarf planet.  The controversy began in 1992 when astronomers discovered other icy bodies out beyond Neptune's orbit, in a region called the Kuiper Belt. The debate only intensified when objects approaching Pluto's size were discovered. In 2005, an object called Eris was discovered,which appeared to be larger than Pluto. Some people wanted Eris recognized as the tenth planet.  Others argued that so many objects similar to Pluto in the same area of space meant that Pluto was not a planet, but some new kind of object. In 2006, the International Astronomical Unionformed a committee to decide once and for all what characteristics qualified an object to be called a planet....

 Pluto, the ninth-largest body orbiting the Sun, has been a matter of contention in recent years. Originally considered a planet following its discovery in 1930, Pluto was regarded as the ninth planet in the solar system for more than 75 years. In 2006, following the discovery of several other small planet-like objects similar to Pluto, astronomers were forced to decide what makes a planet a planet, instead of something else.  According to the rules agreed upon by the International Astronomical Union, Pluto was not really a planet, and on September 13, 2006, it was reclassified, along with the other similar small bodies, as a 'dwarf planet.' Pluto is small - with a diameter of only two-thirds that of Earth's moon - and is made of rocky ice. Astronomers believe that it is about two-thirds rock and one-third water ice. Even though Pluto is small, this much ice represents more than three times the amount of water in all of Earth's oceans combined.   Pluto is...

 Neptune, the eighth and farthest known planet from the sun, is the fourth-largest planet in the solar system. Neptune is the densest of all the gas giants, and so even though it is slightly smaller than Uranus, Neptune is more massive. Like its near twin Uranus, Neptune is made mostly of hydrogen and helium, with traces of other materials and 'ices' like water, ammonia, and methane.   Because of this, Neptune, like Uranus, is sometimes referred to as an "ice giant". While Uranus has a hazy, mostly unremarkable atmosphere, Neptune has active and easily visible weather patterns, which gives it a more distinctive appearance. Like Uranus, Neptune has methane in its atmosphere which gives it a blue color. However, Neptune appears a darker blue than Uranus, and scientist sare not sure why.  When the Voyager 2 spacecraft flew by Neptune in 1989, the planet had a"Great Dark Spot" much like the "Great Red Spot" on Jupiter, but by 1994 the spot ...

 Uranus, the seventh planet from the sun, is the third-largest planet in the solar system, after Jupiter and Saturn, with a diameter about 4 times the Earth's. Like the two larger planets, Uranus is made largely of hydrogen and helium, but it also has many more icy compounds made of water, ammonia, and methane, as well as other materials. Because of this, Uranus is sometimes referred to as an "ice giant."   Uranus has the coldest atmosphere of any planet in the solar system, even though it is not the farthest planet from the sun, with temperatures of about -371 degrees F or -224 Celsius. Unlike Neptune, Uranus does not generate much internal heat. As a result, the weather on Uranus is mostly calm when compared to the feverish activity of the other gas giants.   In fact, at one time Uranus was called 'the most boring planet in the solar system!'. The exception is the weather produced during seasonal changes. Uranus is more than 1.7 billion miles or ab...

 Saturn, the sixth planet from the sun, is the second-largest planet in the solar system, smaller only than Jupiter. Saturn is easy to identify because of the large, beautiful system of rings surrounding it. Like Jupiter, Uranus, and Neptune, Saturn is a gas giant. It is made mostly of hydrogen and helium, with crystals of ammonia in the upper layers of its atmosphere, which is what gives it its pale yellow color.   Although the outermost layers of Saturn are made of gasses, scientists believe that if you traveled down through the atmosphere, you would eventually find that the hydrogen and helium became liquid, and even farther down, metallic, and in the center of the planet, they believe there is a hard rocky core. Saturn is the least dense planet in the solar system.   Although it is much larger than the Earth - about nine times wider and 95 time more massive - it is only about 12% as dense as the Earth is. That means that if you were able to find ...

 Jupiter, the fifth planet from the sun, is also the largest planet. A side from the Sun, Jupiter is the largest object in the solar system. It is called a gas giant, because it is so large and it is made mostly of gasses- hydrogen, helium, methane, and ammonia.  Jupiter is made of many of the same materials as stars: if it had been about 80 times more massive than it is, it might have become a star instead of a planet. It would take more than 300 Earths to equal Jupiter's mass. It is twice as massive as all of the other planets in the solar system put together, and has a diameter of more than 88,000 miles or 142,000 kilometers. It is so large that if it were a big jar, more than thirteen hundred earths could fit inside of it.   Jupiter has been observed for thousands of years and was known to the ancient Romans, who named it after Jupiter, the king of the gods. It is the third brightest object in the night sky - dimmer only than the Moon and Venus. Jupit...

 Mars: the fourth plant from the sun, is the second smallest planet in the solar system, larger only than Mercury. Mars, as one of the five planets visible to the unaided eye, has been known to astronomers since ancient times: it was first recorded by ancient Egyptian astronomers about 4,000 years ago.  Mars is often called the Red Planet, because of its reddish color. Modern astronomers know that Mars is red because of large amounts of iron oxide, or rust, in the rocks and dust on the surface, but in ancient times people associated its red color with warfare. That is why Mars was named for the ancient Romangod of War.   Mars is a small, rocky planet, the last ofthe planets of the inner solar system. It is about 141 million miles, or more than 227million kilometers from the sun, so it gets less than half as much sunlight as the earthdoes.   Temperatures at the frozen poles may dip as low as negative 225 degrees Fahrenheitor negative 143 degrees ...

 Venus - Named after the ancient Roman goddess of beauty, Venus is known for its exceptional brightness in the night sky. But behind this facade is a world of storms and infernos unlike anywhere else in the solar system. Venus, the second planet from the sun, is very similar to Earth from a distance.   But up close, it's a very different world. Venus is about the same size as Earth, just slightly smaller. It's structure is also nearly identical, with an iron core, a hot mantle, and a rocky crust. The crust of Venus, however, is dotted with thousands of volcanoes, including Maxwell Montes, a volcano almost as tall as Mount Everest. Venus also has a thick layered atmosphere.   It's full of clouds that rain (thunder cracking) sulfuric acid, and whip around the planet at speeds up to 224 miles per hour. Faster than some category five hurricanes. The atmosphere is so thick that it creates a surface pressure similar to what it would be about half a mile de...

 The planet Mercury is named after the messenger of the Roman gods, because even the ancients could see how swift and fleeting it is in the sky. But it wasn't until recently that scientists began unraveling Mercury's many mysteries. Mercury is the smallest planet in our solar system. It's diameter currently measures just over 3,000 miles, about the size of the continental United States.    The planet Mercury is named after the messenger of the Roman gods, because      The planet Mercury is named after the messenger of the Roman gods, because   Like Earth, Mercury is a terrestrial planet with three main layers, acore, a mantle, and a crust. Only Mercury's crusthas no tectonic plates. Also, its iron core is enormous by comparison, making up 85% of its radius, while Earth's inner and outer core account for just 55%. Because of the core's exceptional size, it's had a surprising influence on Mercury's overall size,by causing it to shrink....

 Planet Earth is the home of every lifeform, known to us, in the universe. Its age is about 1/3 of the age of the universe and, admitted, It is a thing of beauty. a slightly squashed fair with a heavy metal core,  and a lighter surface crust,  wrapped in a thin sliver of sweet air to breathe, with vast oceans, fertile plains,  magnificent mountains,  fresh water rivers, streams, lakes and aquifers,  orbiting a star which warms us, and gives us energy.  But how did our home come in to existence,  and what's it made of? 4.6 billion years ago,  Earth was created from the remnants of dead stars, that collected in a giant, dirty gas cloud. The gas cloud became denser in its center, and formed an accretion disk.    Small particles started clumping together,  and building larger and larger objects,  until they form the objects we call "Planets" today. This process took 10 to 20 million years,  and is still n...

 If you’re not a morning person, then you’d probably love living on the moon or out in space! The whole “lack of oxygen” thing aside, a ‘round-the-clock night sky sounds pretty tempting! But that got me wondering… - Why is there so much light on Earth, but almost none once you leave our planet? You might think that it’s light during theday and dark at night because the Earth spins on its axis, and the Sun illuminates either hemisphere. That’s part of the reason, but it’s more complicated than that. I mean, our star shines on the Moon too, butthe sky above it is always black! It all comes down to the unique atmosphere surrounding our Earth. It’s full of dust, dirt, gases, and water droplets – which all act like tiny mirrors and reflect the sunlight. When sunlight bumps into these small particles,it diffuses and creates different colors.  That’s why we see a blue sky and all those spectacular shades during sunrise and sunset. - It’s a whole different story elsewhere…...

 Well hi! Unless you’re an astronomer, you probably don’t think of stars as moving all that quickly. You might not even know they move at all. If that’s the case, you’d be surprised to learn that a star called S5-HVS1 is zipping through our galaxy at over ten thousand milesper second. [siren] Alright buddy, what’s your hurry? License and registration. Ow -- you’re awfully bright…) As with many of the best discoveries, astronomers found this rogue star entirely by accident.   Researchers were conducting a survey of what they called stellar streams, remnants of smaller galaxies, torn apart and absorbed into the much larger Milky Way. An astronomer by the name of Sergey Koposov was going through some of the survey data when he came across some unusual readings. He was looking for stars with unusually rapid orbits, but was surprised to find one fleeing the galaxy at record speeds. Now, it’s hard to tell by looking at them,but stars are in constant motion, orbiting the center ...