Furthermore, short-period comets comets with smaller and faster orbits could ultimately evolve into asteroid-like objects after the depletion of their volatile components. A better understanding of the relationship between asteroids and comets throughout the Solar System is thus an essential step in unravelling the first stages of the formation of our Sun and its neighbourhood. Our knowledge of comets and asteroids has dramatically improved over the last decades. ESA's Rosetta mission was designed specifically to achieve important scientific goals by making investigations actually on and around a comet itself.
The mission provided information on the chemical and physical properties of the comet surface and performed sophisticated analyses on the dust grains and the gas flowing out from the nucleus. It followed the comet from a distance of a few kilometres to several hundred in order to map the surface in high detail as well as explore the comet's coma and the interaction with the solar wind. You have already liked this page, you can only like it once! Like Thank you for liking You have already liked this page, you can only like it once!
Occasionally, a comet streaks through the inner solar system; some do so regularly, some only once every few centuries. Many people have never seen a comet, but those who have won't easily forget the celestial show. A comet primarily consists of a nucleus, coma, hydrogen envelope, dust and plasma tails. Scientists analyze these components to learn about the size and location of these icy bodies, according to ESA. The nucleus is the solid core of a comet consisting of frozen molecules including water, carbon monoxide, carbon dioxide, methane and ammonia as well as other inorganic and organic molecules — dust.
According to ESA the nucleus of a comet is usually around 10 kilometers across or less. As a comet gets closer to the sun, the ice on the surface of the nucleus begins turning into gas, forming a cloud around the comet known as the coma. According to science website howstuffworks. Surrounding the coma is a hydrogen envelope that can be up to 6. As the comet gets closer to the sun, the hydrogen envelope gets bigger.
There are two main types of comet tails, dust and gas. Comet tails are shaped by sunlight and the solar wind and always point away from the sun according to Swinburne University of Technology. According to NASA, comet tails get longer as a comet approaches the sun and can end up millions of miles long.
The dust tail is formed when solar wind pushes small particles in the coma into an elongated curved path. Whereas the ion tail is formed from electrically charged molecules of gas. Comet tails may spray planets, as was the case in with Comet Siding Spring's close encounter with Mars.
We can see a number of comets with the naked eye when they pass close to the sun because their comas and tails reflect sunlight or even glow because of energy they absorb from the sun. However, most comets are too small or too faint to be seen without a telescope. Comets leave a trail of debris behind them that can lead to meteor showers on Earth.
For instance, the Perseid meteor shower occurs every year between August 9 and 13 when Earth passes through the orbit of Comet Swift-Tuttle.
Astronomers classify comets based on the durations of their orbits around the sun. Short-period comets need roughly years or less to complete one orbit, long-period comets take more than years, and single-apparition comets are not bound to the sun , on orbits that take them out of the solar system, according to NASA.
Recently, scientists have also discovered comets in the main asteroid belt — these main-belt comets might be a key source of water for the inner terrestrial planets. Scientists think short-period comets, also known as periodic comets , originate from a disk-shaped band of icy objects known as the Kuiper Belt beyond Neptune's orbit, with gravitational interactions with the outer planets dragging these bodies inward, where they become active comets.
Long-period comets are thought to come from the nearly spherical Oort Cloud even further out, which get slung inward by the gravitational pull of passing stars.
In , scientists found there may be seven times more big long-period comets than previously thought. Some comets, called sun-grazers, smash right into the sun or get so close that they break up and evaporate.
Some researchers are also concerned that comets may pose a threat to Earth as well. Comets are generally named after their discoverer. For example, comet Shoemaker-Levy 9 got its name because it was the ninth short-periodic comet discovered by Eugene and Carolyn Shoemaker and David Levy. In antiquity, comets inspired both awe and alarm, "hairy stars" resembling fiery swords that appeared unpredictably in the sky.
Often, comets seemed to be omens of doom — the most ancient known mythology, the Babylonian " Epic of Gilgamesh ," described fire, brimstone, and flood with the arrival of a comet, and the Roman emperor Nero saved himself from the "curse of the comet" by having all possible successors to his throne executed. This fear was not just limited to the distant past — in , people in Chicago sealed their windows to protect themselves from what they thought was the comet's poisonous tail.
For centuries, scientists thought comets traveled in the Earth's atmosphere , but in , observations made by Danish astronomer Tycho Brahe revealed they actually traveled far beyond the moon.
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