What is the Oort Cloud?
WHAT IS THE OORT CLOUD?
The Oort cloud is a huge spherical cloud of comets and dust that extends three light years from the Sun in all directions. The fact that the cloud is spherical rather than disc-shaped sets it apart from other collections of debris in the solar system, such as the asteroid and Kuiper belts. The sphere is so large that its edge is closer to our nearest star than to the sun itself. The edges of the Oort cloud generally represent the limits of the sun’s gravitational influence — comets that stray too far from the edge get lost into space and become interstellar wanderers.
The Oort cloud, after Jan Oort who postulated its existence in 1950. Comets arrive in the solar system from all directions, often from as far away as 100,000 AU. An AU, or Astronomical Unit, is the distance from earth to the sun. Pluto, for comparison, is 39 AU from the sun.
WHERE IS THE OORT CLOUD?
The comets in the Oort cloud are at distances of 50,000 to 100,000 times the distance between Earth and the Sun. That is 1,000 times further away from the Sun than Pluto is and about one fourth the distance to the nearest star. Light would take a year to travel that far.
HOW DID THE OORT CLOUD START?
The Oort cloud objects may have started closer to the Sun during the Solar System’s formation. Then gas giants pulled them far away with their gravity. The Oort cloud objects were sent in all directions, making the Oort cloud ball shaped instead of disk shaped. The gravity of other stars made the objects’ orbits more circular, making the objects stay far away from the Sun. Maybe the gravity of other stars could sometimes send the objects back toward the Sun. We would see them as comets.
One object discovered so far is Sedna. It is 1,180 to 1,800 km across. Its orbit stretches from 76 to 928 times Earth’s distance from the Sun. Sedna takes about 11,250 Earth years to orbit the Sun once. The last time Sedna was where it is now in its orbit, Earth’s last Ice Age was ending! Some scientists consider it an inner Oort cloud object. Others think that it should be included in the Kuiper Belt, making the belt bigger.
D: thats amazing, but if its so far away, how could we possibly see that? unless its all just a prediction.