Alien craft or natural object? The most mysterious comet, Atlas, is approaching Earth
Initial estimates placed the comet’s diameter at about 11 kilometers (7 miles). However, subsequent data from the Hubble Space Telescope indicated that 3I/ATLAS is likely closer to the maximum size of 5.6 kilometers (3.5 miles). In any case, it is likely the largest interstellar object ever observed.
Phaethon is an asteroid that thinks it’s a comet
What is the difference between an asteroid and a comet? A comet is essentially a dirty ball of ice, made up of rock and ice. The classic image is of a bright “star” in the night sky with a long, curving tail stretching into space as it approaches the sun and begins to release gases and dust. This usually continues until there is nothing left but rock, or until the comet disintegrates into dust.
The Oort Cloud consists of comets with million-year orbits and surrounds the solar system
The spherical shell known as the Oort Cloud is virtually invisible. Its particles are spread so thinly and so far from the light of any star, including the Sun, that astronomers simply cannot see the cloud, even though it envelops us like a blanket. It may be hard for the human mind to comprehend: a cosmic cloud so colossal that it encircles the Sun and eight planets, stretching trillions of miles into deep space.