Oort Cloud Facts



The Oort cloud is a spherical cloud of comets that lies at the outer reaches of our solar system, roughly 1 light year away from our Sun.

There are believed to be many millions of objects in the Oort cloud most of which are comets and it was the Dutch astronomer Jan Oort that first calculated the existence of the region.

He worked on a theory of why comets kept appearing and decided that there was a region (now named after him, the Oort cloud) that was producing these comets.

Although we have not yet made any direct observations of the Oort cloud, it is widely accepted to exist among leading scientists and astronomers.

Read on for more interesting Oort cloud facts.

There are believed to be 0.1 to 2 trillion icy bodies contained within the Oort cloud.

Most comets are believed to have originated from the Oort cloud.


The Oort cloud is thought to be made up of two separate regions; a spherical outer Oort cloud and a disc shaped inner Oort cloud or Hills cloud as it is sometimes called.

Many of the comets in the Oort cloud have a long eccentric orbit that will only take them into the inner solar system once.

The most famous object discovered in the Oort cloud is Sedna. Sedna is a planet like transneptunian object that is orbiting our Sun at a massive distance away. The object only approaches the Sun briefly during its 10,500 solar orbit.

One of the most well known comets, Halley’s Comet, originated in the Oort cloud.

Objects in the Oort cloud are known as transneptunian objects.

No spacecraft has observed the Oort cloud and it is not likely that any will get anywhere close to the Oort cloud for tens of years due to the massive distance involved.

There are two main classes of comet that are found in the Oort cloud; the short (ecliptic) period comets and the long (isotropic) period comets. Short period comets have short orbits and long period comets have very long orbits.


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