Did You Know?Most long-term comets (those which have an orbital period of more than 200 years) are thought to be pushed from the Oort cloud towards the inner solar system by the gravity of stars that pass near enough to dislodge these objects from their orbit.
The Oort cloud, or the Öpik-Oort cloud, is an immense, spherical cloud made from billions of rocky and icy comets that surround the Kuiper belt and the inner solar system. It is thought to have formed out of the remains of the same material that formed the Sun and its planets, and were expelled by the gravitational forces of giant planets like Jupiter and Saturn.
The cloud was theorized by Estonian astronomer Ernst Öpik in 1932, and again by Dutch astronomer Jan Oort in 1950. There has been no direct confirmation of this theory as yet. However, it is widely accepted by most modern astronomers and physicists that it is the source of most long- and short-term comets. More recently, proposals have been made to send solar-powered spacecraft to study the Oort cloud. Let's now look at a few amazing facts about this obscure region of our solar system.
- Solar System: 0 - 30 AU from the Sun
- Kuiper Belt: 30 - 55 AU from the Sun
- Oort Cloud: 5,000 - 100,000 AU from the Sun
Interesting Facts About the Oort Cloud
1) The formation of the Oort cloud is thought to have happened when our newly formed Sun gravitationally attracted some of the cometary material from nearby stars to form planets and other objects such as asteroids. However, some of this material was ejected to the outer reaches of the solar system by large planets such as Jupiter, to form the Oort cloud.
2) The dwarf planet Sedna is believed to be a part of the inner Oort cloud. It orbits the Sun once every 10,500 years.
3) The objects found in the Kuiper belt and the Oort cloud are called Trans-Neptunian Objects (TNO). The number of TNOs in the Oort cloud is estimated to be more than 2 trillion.
4) While the outer Oort cloud is spherical in shape, the inner cloud is more like a thick disk.
5) The Oort cloud is believed to be the origin of most comets that have ever been recorded by man. The other source is thought to be the Kuiper belt.
6) The Oort cloud is located approximately 5,000 to 100,000 AU from the Sun. This equals 465 billion to 9,300 billion miles. In comparison, Jupiter is 5 AU and Pluto is 39 AU from the Sun.
7) Due to the immense distance between the Sun and the Oort cloud, the gravitational bond between them is very weak. This enables small gravitational pushes from nearby stars to send TNOs towards the Sun. These are the long-period comets that are recorded by man.
8) The cloud is much further away than the Kuiper belt, hence, there have been no exploratory spacecraft sent to the area till today. However, recently, proposals have been made to do the same.
9) It is estimated that a solar-powered spacecraft will take more than 30 years to reach the Oort cloud.
10) Although the Oort cloud is massive, no man-made telescopes can capture images of this region, despite taking photos of galaxies much farther away. This happens because the objects in the cloud are small and far apart. Cameras in telescopes do not have the resolution to capture these TNOs.
11) Most of the TNOs in the cloud measure around 70 miles wide.
12) The climate in the region around the Oort cloud is too extreme for any life that is familiar to man to exist.
13) One of the most famous comets, Halley's Comet, originated from the Oort cloud.
14) The composition of most Trans-Neptunian Objects in the cloud is of water, ammonia, and methane.
15 The objects in the Oort cloud are scientifically important, because they hold clues to the origin of our solar system, and possibly the universe.
16) The cloud reaches approximately ¼ the distance from our Sun to the closest star Proxima Centauri.
17) Many experts believe that the cloud has billions of objects that are at least 12 miles in diameter, besides trillion other smaller objects.
Although the information we have on the Oort cloud is limited at this time, with rapid technological advances, we can hope to get a closer look at this mysterious place, in the decades to come.