Universe Guide

Extrasolar Planet (Exoplanet)

Extrasolar Planet Facts

What is an Extrasolar Planet (Exoplanet)?

Extrasolar Planet (Exoplanet) means any planet that is outside our solar system. The first exoplanet that was discovered was discovered in the early nineties around a pulsar with the easy to roll off name, PSR B1257+12. It has since been renamed by I.A.U. as Lich after the fantasy creature. It is not named after the creatures that inhabit the World of Warcraft nor a nod to Arthas Menethil, the Lich King.

Ever since we found 51 Pegasi, the first exoplanet around a Sun like planet, we have found thousands. They discovered the planet by observing the star and noticed it wobbled. With further investigation, they realised that this wobble could be caused by planet circling it. The planet had the unofficial name of Bellerophon. When a large object such as Jupiter travels round the Sun, it causes it to wobble because of its sheer mass. The sizes of these planets that we've been finding are on a scale equal to that of Jupiter or bigger. It is believed by many scientists that most if not all of these newly discovered planets are gas giants which will mean that they are incapable to supporting life. A lot of these exoplanets whizz round their stars at an astonishing speed and some are really close to their star. With probably one or two exceptions, all the planets are found round insignificant stars, some of which you couldn't see if you looked up at the stars.

Search for Alien Life with Exoplanets

Discovering planets increases the chances that we are not alone in the galaxy. We'll never be able to get to these planets unless we find out a w ay of generating wormholes. These planets to support life would have to be in the Goldilocks zone. This zone is named after the the fairy-tale which means its not too hot and its not too cold to support life. The planet HD 209458 b has been spotted leaking oxygen. Its distance from the Sun, and orbital length can effectively rule it out of contention for supporting life.

The NASA space probe Kepler was launched (2006) to scan the stars for Earth sized planets if there are any planets in a small region of space. This will provide the basis for two future missions, 'Space Interferometry Mission' (2009) whose primary mission is to measure the distances of the stars more accurately. Its second mission is to scan for planets. Sadly, the mission was cancelled after being postponed many times. Another project by N.A.S.A. was to create the Terrestrial Planet Finder to connect a number of telescopes together to search for planets but like S.I.M., it too was postponsed and then cancelled.

Unlike the past two cancelled missions, TESS (Transiting Exoplanet Survey satellite) is due to take off in March 2018 to survey the brightest stars for transiting exoplanets. Transiting planets are ones that pass in front of the star. It will not be limited to the small area that Kepler was limited to but look at the whole of the galaxy. It is expected to be in operation for two years. 2

Further down the line is PLATO (Planetary Transits and Oscillations of stars), a European Space Agency (E.S.A.) project that is not due until 2024. The primary objective is to look for Earth sized planets and and those that are in the Goldilocks zone that could possibly contain life maybe not as we know it then. 3

There's no single planet to be most likely to contain life, there are a number of candidates. One of the most likely is Kepler 22b which is just slightly bigger than Earth and is within the star's goldilocks zone. It is not the only planet in that solar system but it is in the Goldilocks zone.

Sizes of Exoplanets

Exoplanets are no different really from the planets that exist in our solar system. Exoplanets can be Earth sized, Mercury sized (small), Dwarf Sized (Ceres) and giant gas planets (Jupiter).

Largest Exoplanet Discovered

The largest exoplanet that has been discovered is GQ Lupi b in the constellation of Lupus. It is three times the size (radius) of Jupiter, the largest planet in our solar system. It orbits its star at 100 times the distance Earth is from the Sun. The planet is too far away from its star to be hot enough to support life. N.A.S.A.

Smallest Exoplanet Discovered

Kepler-37 b is the smallest so far discovered exoplanet at the time of writing. It orbits very close to it star and is therefore too hot to be able to support life. It is a third the size of the Earth so spotting it is quite an achievement. It zooms round its star at 13.4 days. N.A.S.A.

Methods used to discover Exoplanets

Radial Velocity

Even the smallest planet can have an effect on a star. All the planets in the Solar System has an effect on the planet. When a planet orbits, it pulls on the star and by looking at the pull, scientists can detect a planet in orbit. By studying the light from star, you can tell if the star is moving towards you (blue) or moving away (red).

Transit Photometry

When a planet passes in front of a star, it causes the star to dip in part or in whole. If the planet has dipped, an orbiting planet is a good reason for why the star has gone slightly darker in part. The amount of darkness on the star can allow scientists to infer the size and closeness of the planet.


Microlensing is when light from a distant object is magnified due to the light from a nearer object. It is used to detect exoplanets that are very far away which would otherwise not be able to be studied.


Astrometry is like Radial Velocity except instead of looking as to whether the star is moving back and forth, it is looking to see if the star is moving left or right.

Direct Imaging

This is examing the star visually. All the other methods are based on calculations to give up their planets. This method not as widely used as the other methods tries to view the planet first hand. It requires extreme magnification and that the object be not far away. We've not got to the stage where we can see what the planet actually looks like, they are only a blob at the moment.

The Nearest/Closest Extrasolar Planet to Earth

On the 24th August 2016, scientists studying at the European Space Organisation observatory in Chile announced that they had found a planet around Proxima Centauri in the constellation of Centaurus. They had found it sixteen years earlier but had only now got all the information that they required to go public with the finding. The star is a dim red dwarf star part of the Alpha Centauri multiple star system. The star is too dim to see with the naked eye and was only discovered in 1915. The planet is said to be within the Goldilocks Zone of the star. The planet zips round its star (orbits) at a very fast about 11 days. The star is a slow burner and would last trillions of years and so if we made it to a planet we wouldn't have to worry about finding another planet again. Which is probably not that true because a supernova in a nearby system would cause untold damage to the environment. The planet has been calculated as being a fraction bigger than our own planet Earth.

The next nearest exoplanet to Earth is Alpha Centauri Bb which orbits the middle sized star in Alpha Centauri which happens to also be the second nearest star after Proxima Centauri. If we could travel at the speed of light, it would take us about 4.4 years to get there. If however there was a Wormhole then depending on how good the wormhole was, be there and back in no time.

The current record holder for the furthest exoplanet from Earth is OGLE-05-390lb in the constellation of Scorpius. It is 6,500 light years away and any chance of meeting any Aliens from that planet are non-existent unless there's a transwarp drive that could get us there but they only currently exist in science fiction.

Are there any Extragalactic Planets?

Extragalactic or Extragalaxy Planets are planets that are in another galaxy. Scientists in and around 2009 used a technique called Pixel-lensing based on light being bent when it passes a bigger object, found what they believe to be a giant Jupiter orbiting a star in the Andromeda Galaxy and that planets are not just a Milky Way phenomena. 4 The Andromeda Galaxy is a close galaxy to our own and is moving at a speed of 75 miles a second towards us. Even at such speed and distance, the galaxy is not expected to collide with the milky way for another four billion years, long after the Earth has gone and the Sun has gone supernova.

How are Extrasolar Planets named?

The very first exoplanet discovered was 51 Peg and the discoverers unofficially named the planet Bellerophon as the Greek hero who tamed Pegasus, the fabled winged horse in Greek Mythology after all the planet was in the constellation of Pegasus. It was Perseus who flew the winged horse to rescue Andromeda. However the planet is only ever referred to as 51 Pegasi but unofficially as Belleraphon. However when IAU ran a competition, 51 Peg became known as Dimidium.

Planets that begin with the name Kepler were discovered by the kepler space telescope that was launched in 2009 to study a small region of space in Cygnus where there is a large amount of stars. Its original mission timeline was supposed to be three and half years but after six years, it is still going strong. At present, it has found over a thousand planets in 440 solar systems with an estimated 3200 unconfirmed planets and that's all in the one area of space. 1

WASP planets were discovered by the WASP (Wide Angle Search for Planets) search team that is a predominately British academic group searching for exo-planets involving but not limited to Keele University and University of Leicester. They have access to two large robotic telescopes, one on La Palma (North) in the Canaries and the other (South) in South Africa. Unlike the Kepler project, they aren't limited to a specific area of space. The telescope are situated where they are because its dry, not much cloud and they are situated high in the mountains.

OGLE (Optical Gravitational Lensing Experiment) is a Polish academic mission that seeks out extrasolar planets in our galaxy. They use the Las Campanas Observatory in Chile to aid them in discovering extrasolar planets.

Corot planets are those discovered by a French led team (French: COnvection ROtation et Planetaires Transits Plan; English: COnvection ROtation and planetary Transits) . They sent a satellite into space in 2006, before the Kepler mission and have been using the results from the satellite to detect extrasolar planets.

Planets are named after the Star that they orbit and then lettered b,c,d,e,f etc. There is no planet named 'a' because a represents the star. Some stars will have common names such as Algieba, Fomalhaut etc but others will have more cryptic names such as Kepler 47. Kepler is the name of a satellite in space that first spotted the star and then the planet.

The IAU, the governing body for all things Astronomical ran a competition to name some stars and some planets in 2015. None of the planets got names from television and films such as Vulcan or Bespin. The names chosen were names of ancient mythological gods and some were of people (e.g. Harriot,Janssen, Lippershey, Brahe, Galileo, Copernicus), all allocated to planets in 55 Cancri. All previously name objects had the same sort of naming structure which is why they went down that path.

Are there any Exomoons?

Any moons found orbiting a exoplanet would be referred to as a Extrasolar Moon or Exomoon for short. Our solar system is nothing special, other stars out there are similar, with the same variety of planets, rocky and gaseous. Like our planets, some exoplanets will almost certainly have a moon. Nothing for definite but scientists do believe that they have found an exomoon. Its only hinted at at the moment but in future, it could be confirmed. The moon is orbiting a giant planet 420 light years away. 5

Can a planet like Tatooine exist?

Tatooine is the fictional planet in Star Wars where Anakin Skywalker was born and lived his infant life before becoming a Jedi and then turning to the dark side to become a Sith Lord, a practitioner of the Dark Side of the Force. Tatooine is a desert planet that has two stars which you see when Luke Skywalker looks out at the horizon as the night is beginning. There have a number of planets discovered circling Multiple Star System such as the one circling Algieba but that planet was a gas giant, what makes Kepler 47 is that the planet is in the habitable zone (aka Goldilocks Zone) so could in theory have life. If you look carefully on the right side of the picture, you might just be able to make out the second sun orbiting the first.

Luke Skywalker on Tatooine and a Possible Real Life Tatooine Solar System

Artists Impression of a World

The below series of pictures are what Dave using Terragen imagined what a extrasolar planet would look like. He came with a Mars-Like planet called Olanis. The planet is obviously not-suitable for hosting life. However the planet in the background Crumaria could contain life.


What is a Zombie Planet?

The star Lich, previously known as PSR B1257+12 is a pulsar, a rotating neutron star. It is located in the constellation of Virgo. The star has three planets named Poltergeist, Draugr and Phobetor, all named after names of nightmare creatures. The planets are bathed in radiation that comes from the spinning arms of the neutron star. There is no way any life could survive and live on the planet. As it was the first star to have planets in orbit, the IAU entered the star into the star naming competition because of its historical significance. ref: N.A.S.A,


The term 'Super-Earths' refers to exoplanets that are bigger than Earth, by a factor of maybe three or four or more but are not as big as Neptune. The planets can be either rocky or a gas giant. They can be in the Goldilocks Zone and harbour life. As the planets are bigger than Earth, their gravity will be much bigger as well which means if we were to land on the planet, we would have a hard time adjusting to the planet. Life forms on the planet would be much stronger than us puny humans.

List of Discovered Planets

I have detailed some, not all the currently discovered exoplanets using available data on-line . The biggest source of exoplanet information is Exoplanet Orbit Database, a free to access list of discoveries. To view details on an exoplanet on this site, you need to visit the host star page. The host star page is linked from the constellation page that the star can be located in. So if you want to see information of Trappist-1 b planet, visit the Aquarius page then select Trappist-1 from the list of links. Alternatively, you can go straight to the star if you know its name.

Canes VenaticiCanis MajorCanis MinorCapricornus
Coma BerenicesCorona AustralisCorona BorealisCorvus
LacertaLeoLeo MinorLepus
PictorPiscesPiscis AustrinusPuppis
Triangulum AustraleTucanaUrsa MajorUrsa Minor

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