Sedna Facts

Sedna is a minor planet that lies beyond the orbit of the planet Neptune in a region called the Oort Cloud. It is a possible dwarf planet. Sedna is one of the reddest celestial objects in our Solar System.

Sedna Profile

Interesting Sedna Facts

  • Sedna is a minor planet lying beyond the orbit of Neptune.
  • It is a Trans Neptunian object.
  • Sedna was discovered by a team of scientists in 2003.
  • It has a radius of approximately 1000 km.
  • Sedna has been named after the Inuit goddess of the sea and of the marine animals.
  • Its closest point from the sun is 76 astronomical units away.
  • Its farthest point from the sun is 936 astronomical units away.
  • It takes newly 11400 years to complete one orbit around the sun.
  • Sedna takes 10 hours to rotate about its own axis.
  • The Minor planet Sedna has a very high eccentricity.
  • It was initially going to be named the Flying Dutchman.
  • It may come close to the Sun and hence to the Earth by the year 2075 or 2076.
  • It is not known to have any moon.
  • Sedna doesn’t have any rings.
  • It is one of the farthest known objects to human beings.
  • It is believed to be present in the inner parts of a region called the Oort cloud.
  • It is one of the largest known Trans Neptunian objects (TNO).
  • The distance between Earth and the Sun is nearly three times the distance between the sun and the planet Neptune.
  • It is estimated that more than 100 similar objects could be found in the region where Sedna is situated.


Sedna is a minor planet that lies beyond the orbit of the planet Neptune in a region called the Oort Cloud. The Oort Cloud is a hypothetical region that lies beyond the orbit of the planet Neptune. It is a shell-like structure or cloud.

The existence of this cloud is theoretical and predicted. This region is yet to be undiscovered. It has been named after the Dutch astronomer Jan Oort who proposed the possibility of its existence in 1950.

The official designation of the minor planet is 90377 Sedna. It is about 86 astronomical units away from the sun. This is close to 12.9 billion kilometers from the Sun. The distance between the Sun and Sedna is about three times the distance between the planet Neptune and the Sun.

The minor planet takes nearly 11,400 years to complete one orbit around the Sun. There was a lot of debate among scientists about whether to classify the subject as a minor planet or as a dwarf planet.

As one would expect the minor planet is not visible from the earth with the naked eye despite clear visibility or zero light pollution. This is obviously because of its great distance from the Sun. to view Sedna advanced telescopes and other equipment needs to be used. For example, the Hubble Space Telescope in NASA.


This minor planet was discovered by three scientists namely Michael Brown, Chad Trujillo, and David Rabinowitz on the 14th of November 2003. Eris, Haumea, and Makemake were also co-discovered by Michael Brown in the same observatory.

Initially, the name the Flying Dutchman was proposed for the minor planet. This was the name of a legendary ghost Ship which is also a part of The Pirates of the Caribbean movie franchise. It was to be named so because of its slow movement around the sun.

However, this name was dropped, and the minor planet was finally and officially named as Sedna after a figure from the Inuit mythology. This name was chosen by Michael Brown firstly because of its easy pronouncing and secondly because the Inuits were a part of popular culture in his home town of Pasadena.


It is not known for sure how this minor planet was found but there are some speculations. It may have been formed closer to the sun than it is today but got scattered by the gravitational influence of a larger body that is relatively close to a such as the planet Neptune. It may have got drifted away so far that it became an inner Oort cloud object.


The minor planet is red in nature. In fact, it is as red as the planet Mars. The nature of the surface and composition of Sedna has been determined by the method of spectroscopy.

What is Spectroscopy?

When an object light splits into its constituent colors the formation of rainbow takes place. The resulting image formed is called the spectrum.

As different wavelengths of light are absorbed by different objects when we see the spectrum of a particular object dark lines appear on it. These lines are called absorption lines and the pattern all together is called the absorption spectrum. This is the reason why each object has its own unique absorption spectrum.

Hence judging by the absorption spectrum of different objects we can determine the material of the substance with which it is made. Using the same method, scientists have determined that most of the far-off bodies in the solar system such as the ones present in the Kuiper Belt or the Oort Cloud. They are a mixture of ice, rock, methane, ammonia and other volatile gases and ices.


The exact diameter of the minor planet is not known. Still, it can be determined by looking at an absolute magnitude which is 1.8 and its albedo which is 0.32. It can be estimated to be approximately 1000 km. In 2004, it was suggested that the diameter could be 1800 km.

The same was revised in 2007 when it was suggested to be 1,600 km by observing it through the Spitzer Space Telescope. Finally, the Herschel space observatory suggested Sedna’s diameter to be approximately 995 kilometers. This makes the minor planet even smaller than Pluto’s moon called Charon.


Not much is known about what the surface of Sedna is composed of and what is the structure of its atmosphere. However, it is believed to be similar to that of Pluto.


Sedna has a composition that is very much similar to that of Pluto as well as Triton, a moon of Saturn. Objects in the Oort cloud have a very low average temperature. Most of the objects in this belt would be gaseous if they were closer to the sun.

The objects in the Oort Cloud which have a diameter of more than one kilometer are thought to be trillions in number while billions of objects have a diameter of more than 20 kilometers.

According to recent research by NASA, a huge number of objects were formed in the Oort cloud maybe as a result of an exchange of matter between the sun and some stars that were close to it during their formation before they drifted apart.

Orbit & Rotation

The minor planet Sedna has one of the longest orbital periods known to mankind. It has an average orbital period of more than 10,000 years. Its orbit is extremely eccentric. Its farthest distance from the sun that is its aphelion is about 937 astronomical units while its closest distance from the sun that is its perihelion is about 76 astronomical units from the Sun.

This makes its orbit very extreme. Obviously, this makes it one of the farthest known objects of the solar system. Eris however is more distant than Sedna, as it is 97 astronomical units away from the Sun on an average.

Despite its large orbit the orbits of many comets extend further away than that of Sedna. Even when the minor planet is at its closest distance from the sun the sun would only appear as a point sized star in the sky if one observes it from the surface of Sedna.

Sedna has a rotational period of about 10 hours. At the time of its discovery it was thought to have an orbital period of 20 to 50 days which is unusually longer as compared to other similar celestial objects.

Scientists initially speculated that the rotation of the minor planet was slowed down due to the gravitational pull of the largest celestial objects in its proximity such as Pluto or its moon Charon. It is also one of the largest known Trans Neptunian objects to us. Some scientists also believe that about 40 to 120 more objects which have a similar size as the minor planet could exist within the same region.

Magnetic Field

No information about the existence of a magnetic field on Sedna is currently available.


Not much is known about the structure of its atmosphere. However, it is believed to be similar to that of Pluto.


Sedna is not known to have any moons or natural satellites. This is surprising as the discoverers of the minor planet as well as other scientists of the world believe that the celestial body is very likely to have its own natural satellite. Scientists are still looking for its moons and have suggested that because of its large orbit and lack of opportunities to study the minor planet its natural satellite could have been missed by human beings if it exists.

Sedna Exploration

Sedna has never been visited by any spacecraft. It will reach its closest point to the Sun by the year 2075 or 2076. This would give us a unique opportunity to study the minor planet which may not come again for another 12,000 years. Currently, no missions to the minor planet are being considered which is acceptable since the distance between the Earth and Sedna is very large to be covered by human-made spacecraft at this time.

However, it has been observed by several advanced telescopes from the Earth, like the Hubble Space Telescope. They have helped in determining the size and the mass of the minor planet which turned out to be pretty close to what had been previously estimated using other techniques.

What is Oort Cloud?

The Oort cloud, in which Sedna is situated, is one of the most unique and fascinating regions in the solar system. This could be because it is not known for sure if this region exists. Even if it does, it is untouched and undiscovered by man.
Still, the introduction of the concept of the cloud gave the answers and logical explanations about many questions that had been in the minds of people since ancient times, most of them being about long-period comets. Even then this region remains one of the most mysterious known concepts.

Life on Sedna

Obviously no evidence of life has ever been found in this region as the Oort Cloud has never even been visited by a spacecraft. It is quite unlikely that any spacecraft would be sent to this region for at least a few more centuries. It is still just a hypothetical concept that is waiting to be proved.

No human being has ever visited Sedna. It would be very difficult to build a spacecraft and send humans to Sedna as the spacecraft would take several years to reach the minor planet. However, human missions to farther planets may become possible in the future with the advancement of science and technology.

Research on Sedna

Even though we know a significant number of things about the minor planet and the region in which it is situated, a lot still remains unknown. In fact, it is one of the most extensively studied fields in astrology by both professional and amateur astronomers and it is one of those distant objects about which we know a considerable number of things.

Despite this most of it still remains unexplored. This is because the minor planet Sedna extends far away from the extent of human-made machines. However human beings are continuously making efforts to go beyond their reach and find out more about the universe that we know about. This is because the universe is continuously expanding and so is human interest in it. Sedna is actually not a very familiar concept for us on earth.

Dwarf planets and minor planets have not been known to mankind for that long time as compared to the other planets of the solar system. This is because of the fact that they are comparatively smaller in size and are at a great distance from the Sun.


  • 2004: Sedna is discovered
  • 2004: The dwarf planet is officially named ‘Sedna’


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