What is a comet? It is a small solar system body that orbits the Sun like the rest of our planets. Comets are big chunks of ice, dust, rocky particles and gas. They are kind of like dirty snowballs of leftovers from the beginning of our solar system. Comets get their name from the Greek word "kometes" which means long hair that references their tails. Did you know that comets actually have two tails instead of one? They split in different directions and are made up of different material. The dust tail is the clunky curved tail containing gas and dust following the comet. The ion gas tail is formed by the interaction between the Sun’s weather and the gaseous particles of the coma which is the evelope of evaporated gas that surrounds the solid part of the comet. Which way the ion tail is pointing depends on where the Sun is. So if a comet is traveling towards the Sun the ion tail will follow behind, but if the comet is traveling away from the Sun the ion tail will be in front of the comet. Wow!
Where do they come from?The Kuiper Belt and the Oort Cloud are regions of space beyond the planetary region of our solar system. Did you know that when objects from the Kuiper Belt and Oort Cloud enter the inner solar system they become comets due to interactions with the sun? Those objects orbiting in the Kuiper Belt and Oort Cloud are mainly composed of rock, water ice, and frozen gases such as carbon dioxide, carbon monoxide, ammonia and methane. Each of these regions contain billions of something called dark comets, but they have so much room in space to swirl around they get no closer to each other than we on Earth do to the Sun.
Why do Comets travel out of the Oort Cloud or Kuiper Belt?Believe it or not comets could spend billions of years in the Kuiper Belt or Oort Cloud. Sometimes those comets will come close to one another, or even crash into each another. When this happens the comets change directions and new paths will bring them into the Inner Solar System. When a comet approaches the warmer Inner Solar System region, the ice begins to sublime which means to vaporize into gas, leaving behind those magnificent shinny tails becoming the most brilliant and rarest objects in the night sky. Although it is the most glorious part of their lives, traveling through the Inner Solar System eventually kills them. After several thousand years they eventually evaporate down to speck of ice or dust, not nearly enough to leave a tail and some comets evaporate away forever.
Ever since the Earth formed 4.5 billion years ago, it has been bombarded with rocks from space. Large space rocks are called asteroids, and small ones are called meteoroids or shooting stars. Each year about 50,000 tons of this material enters the Earth’s atmosphere. Most of it burns up in the atmosphere but some rocks make it to the Earth's surface. Most asteroids revolve around the Sun between Mars and Jupiter in a region called the asteroid belt.
Kind of like comets, asteroids are also small Solar System bodies that orbit the Sun. However they are made of rock and metal and do not have a visible tail like comets do. Asteroids are more like planets and moons. Scientists often call asteroids minor planets. Believe it or not there are millions of asteroids. The biggest asteroid is Ceres. It is about 950 kilometers in diameter, that’s almost 600 miles. It was the first asteroid ever discovered, probably because it was the easiest to see. Asteroids are not easy to spot because they often look like dark blobs against the darkness of outer space.
Where do they come from and how many are there?Where do you think an asteroid comes from? One theory suggests an exploded planet produced them, while another theory suggest a planet failed to evolve completely.
As of today 26 gigantic asteroids have been discovered, which is probably most of the big ones out there. But there are still millions of smaller ones out there that have not yet been discovered just because they are too tiny to see.
What is the Minor Planet Center?Did you know that there is an organization called the Minor Planet Center, or MPC, which is the single worldwide location for receipt and distribution of positional measurements of minor planets, comets and other irregular natural satellites of the major planets? The MPC is responsible for the identification, designation and orbit computation for all of these objects. This Center maintains the entire master files of observations and orbits, while keeping track of the discoverer of each object, and announces those discoveries to the rest of the world by electronic circulars and thru the worldwide web.
Collision PreventionYou may wonder why we can't just destroy dangerous asteroids? But to try to destroy an asteroid or comet in space by a single explosive charge on or below its surface would risk breaking it into a number of large uncontrollable pieces, which could still hit the Earth, which could cause even more damage. And some scientists predict that such a shattered asteroid would re-form due to gravity within hours of destruction.
A more promising method of destruction would be to fly a spacecraft alongside the object, perhaps for months or years, nudging it in a controlled way from time to time with explosives or other means. This relatively gentle approach is particularly important because many asteroids and comets are held together only by their own very weak gravitational fields. The longer the time before impact, the more effective even a small nudge would be. Knowing this, what do you think would be the best way?
Imagine this floating rocks smaller than an asteroid but larger than a grain of sand all floating in space. These are called "meteoroids." They range in size from that of a pencil point to around 10 meters in diameter. These asteroids are renamed "meteors" while they travel through Earth's atmosphere, and "meteorites" if they hit the ground. A meteoroid that burns up as it passes through the Earth's atmosphere is known as a meteor. If you've ever looked at the night sky and seen a streak of light or 'shooting star' what you are actually seeing is a meteor.
When many meteors occur at the same time in the same part of the sky it is called a meteor shower. A meteor shower happens when Earth passes through the path of a comet. When this happens, the bits of comet debris, most no larger than a grain of sand, create streaks of light in the night sky as they burn up in Earth's atmosphere. On any night, there are several small meteors that shoot across the sky. However, during a meteor shower, tens to hundreds of meteors can be seen each hour. Many of these meteor showers can be predicted and occur at the same time each year.
As for meteorites receiving the nickname of "shooting stars", it is a little misleading because it causes some people to think that these fast moving trails of light really are stars that have fallen out of the sky. But, this is not true. Our Sun is a star, in fact it is the closest one to us, and stars are much bigger than a comet, a meteor, or even an asteroid . Meteorites are not that big we can thank the stars for that!
And really, comets, asteroids, and meteors are not a worry to us here on Earth. This is because their orbits stay the same year in and year out, just as the Earth's does. This is because their orbits stay the same year in and year out, just as the Earth's does. Once an asteroid is identified and its orbit determined, our scientist could predict its future path very accurately.
Chelyabinsk MeteorOn Feb. 15, 2013, a 65-foot-wide (about the size of a school bus) asteroid called the Chelyabinsk asteroid detonated in the skies over the Russian city of Chelyabinsk, causing millions of dollars of damage and injuring 1,500 people. The dramatic and scary event served as a wake-up call for many scientists to alert the world to the dangers posed by the millions of space rocks that reside in Earth's neck of the cosmic woods. And as of today it was the largest asteroid impact on land in more than a century.
NASA also has lots of tracking stations, 22 to be exact! And one of the tracking station called The Goldstone Deep Space Communications Complex. It is located in the U.S. state of California's Mojave Desert and is operated by the Jet Propulsion Laboratory. Its main purpose is to track and communicate with space missions. It is named after Goldstone, California, a nearby gold-mining ghost town. Spooky!
Goldstone has a 70m antenna that has been used as a sensitive radio telescope for such scientific investigations as mapping quasars and other celestial radio sources; radar mapping planets, the Moon, comets and asteroids; spotting comets and asteroids with the potential to strike Earth; and the search for ultra-high energy neutrino interactions in the moon which use large-aperture radio antennas.
Sentinel is a space observatory currently being built by Ball Aerospace for the B612 Foundation. Did you know that The B612 Foundation is a dedicated to protecting the Earth from asteroid strikes. The foundation's goal is to design and build a asteroid-finding space telescope, that is scheduled for launch in the 2017-2018 timeframe. The Sentinel's super cooled infrared telescope will help identify asteroids and other near-Earth objects that poise a risk of collision with Earth.
Comet ISONRecently, comets have also been making headlines. In early Nov. 2013, Comet ISON entered the Earth's orbit as it continued its way toward the sun for a fiery close encounter in late November. The comet fascinated scientists and astronomers alike especially during a later outburst, which boosted the comet's brightness tenfold. The comet's encounter with the sun ended with the comet's ultimate demise into a cloud of dust. Talk about exciting space news!
RosettaComets are hard to catch! The comet 67P flies at 55,000 kilometers per hour. That's over 34,000 mile per hour! It took the space probe Rosetta 10 years to catch up with it. Because Rosetta had to save energy, the European Space Agency that operates Rosetta even had to put Rosetta into hibernation for almost three whole years! Still, Rosetta has traveled almost six and a half billion kilometers in a game of science "tag" and now in 2014 is flying alongside 67P collecting brand new information about comets right up close using NASA instruments. It's so far away, it takes over 20 minutes to talk to Rosetta from Earth, but this is the first time ever any spacecraft has ever flown with a comet. The more we learn about comets, the more we learn about our solar system and the precious water that is how life began. Really cool!
H2O MiningH2O or water is our Earth's precious commodity and we need it every day in order to live. Why is water called H2o? Because there are two hydrogen atoms for every oxygen atom. During a process called electrolysis, water can be split into separate elements, hydrogen and oxygen. The power to drive this process can come from solar cells, capturing the sun's energy to split the hydrogen and oxygen. Then, the two elements can be stored and eventually burned together in a rocket engine to provide thrust for the mission. That is the kind of fuel used by the Space Shuttle's main engines. Most people don't realize that the Shuttle used to fly into space on a flame of water. Used this way, water is simply an energy storage medium, slowly taking in the energy required to split it apart, storing that energy in concentrated form as chemical energy, and giving it back as thermal energy very rapidly when we burn it, so that the rocket nozzle converts it into kinetic energy by pushing the rocket. This is how the water we drink becomes the energy to power rockets!