In the last 20 years or so, it seems like a new exoplanet has been discovered almost on a daily basis. The term exoplanet is used to classify those planets which have extrasolar (outside our solar system) origins. Although the first-ever confirmed detection of an exoplanet came in 1992, the scientific world had already discovered a planet that orbits a star outside our solar system back in 1988.
In the 21st century, major space agencies around the world have dedicated their extensive amount of resources to closely study these exoplanets and among them ESO’s HARPS and NASA’ Kepler space telescope have revolutionized this field of study.
Since 2009, Kepler has detected more than two thousand extrasolar planets, way more than any other Earth or ground-based telescopes, including HARPS, which itself has discovered almost hundreds of them.
Unlike distant stars, we cannot possibly observe exoplanets with naked eyes and even with the help of most of the modern telescopes. The reason behind this is that they are extremely small and faint.
To overcome this issue, astrophysicists seek help from various advanced scientific methods that work on light. By analyzing the light emitted from the distant object, we can derive various characteristics of the planet, like its atmospheric and surface composition.
Table of Contents
Quick Overview
Total Number of Exoplanets Discovered: 3,672+
First-Ever Exoplanet Detected: 1988
Nearest Exoplanet: Proxima-b
Farthest Exoplanet Detected: SWEEPS-11, SWEEPS-4
Below, we have compiled 22 of the most interesting Exoplanets with some thrilling details.
22. WASP-12b
Image Courtesy: ESA/Hubble
Our first candidate is an exoplanet orbiting a yellow dwarf, or a G dwarf main-sequence star in the constellation of Auriga. Due to its extremely close orbit around the host star, WASP-12b has one of the lowest densities among all the detected exoplanets.
In 2017, with the help of Hubble space telescope, researchers discovered that this planet reflects almost all of the light that fell on its surface, causing it to appear a pitch-black planet.
21. PSR B1620-26 b
Artist Impression of planet PSR B1620-26 b
PSR B1620-26 b, popularly known as ‘the genesis planet‘, is perhaps the oldest exoplanet we have detected to date. Studies revealed that the planet is about 12.7 billion years old (formed just 1 billion years after the Big Bang).
Located in the constellation Scorpius at a distance of 12,400 light-years from Earth, this old planet revolves around two stars – a pulsar and a white dwarf.
20. Gliese 436
Image Courtesy: ESA/Hubble
Gliese 436 is a Neptune sized hot planet orbiting an M-type red dwarf in a two-planet solar system at a distance of 33 light-years from Earth. The Gliese 436 has one of the smallest orbital radius and mass among all the discovered exoplanets and was only surpassed by even smaller Kepler planets which were discovered later.
Various studies suggest the existence of ‘burning ice’ under its surface. Scientists believe that it had a significant amount of water buried under the immense pressure between its rocky core and crust. The pressure was so massive that it actually turned into solid ice.
19. Proxima b
Image Courtesy: ESO/M. Kornmesser
Forget about all the exoplanets over some freaky distances, here we have a planet that might possibly sustain life and is only 4 light-years away. Lying within the habitable zone of its host star, Proxima-b is one of the most sought after exoplanets among astronomers worldwide.
18. 2MASS J2126
Image Courtesy: University of Hertfordshire/Neil Cook
When astronomers first detected the exoplanet 2MASS J2126- 8140 in the constellation of Octans, they were stunned because there was no visible host star to the planet. They named it a “rough planet.”
But later studies revealed that it does indeed have a star located at trillion kilometers away, making it undoubtedly the largest planetary system ever discovered. To put this into perspective, the distance is about 7,000 times the distance between the Earth and the Sun and it has an orbit 140 times wider than that of Pluto.
17. HIP 68468 System
Image Courtesy: Gabi Perez / Instituto de Astrofísica de Canarias
At a distance of 300 light-years, astronomers have discovered a Sun-like star or solar-twin, which is apparently eating away its own planets. Hip 68468 is orbited by two confirmed planets HIP 68468 b and HIP 68468 c.
Years of research and observations indicate that at least one more planet used to orbit the star alongside the two other companions. While it might be the first-ever planet-eating star discovered, this phenomenon could be more common than we actually think.
16. Gliese 876 d
Image Courtesy: NASA/Ames
At the time of its discovery, Gliese 876 d had the lowest mass of any extrasolar planets except the three pulsar planets detected so far. Due to this, the planet is categorized as one of the earliest detected super-Earths.
15. HR 8799
Located at 129 light-years from Earth, HR 8799 is the first-ever directly imaged multi-exoplanet system. The system features a debris disk-like Kuiper belt and at least four massive planets
14. Kepler-36 system
Image Courtesy: ESO
The Kepler-36 planetary system (with two confirmed planets) has one of the most unique orbital settings ever discovered. The two planets, one is a super-Earth and the other is a mini-Neptune, revolve around their host star in a very unusually close orbit. Their closest approach is about 1.5 million kilometers.
13. HD 189733 b
Image Courtesy: ESO/M. Kornmesser
HD 189733 b is one of the most extensively studied exoplanets discovered to date. About the size of Jupiter, it was first detected transiting its host star with the help of X-ray enabled telescopes. Being a hot Jupiter is probably the major reason why it has been studied with different spectral wavelengths and instruments over the years.
12. Kepler-78b
Image Courtesy: David A. Aguilar (CfA)
Based on its current characteristics, many actually believe that this exoplanet shouldn’t have existed in the first place and they have every right to think so. Kepler-78b is the only detected planet revolving around its host star Kepler-78, which has about 75% of the total radius of the Sun.
What is bothering scientists about this particular exoplanet is how it is still there revolving dangerously close to the star. Studies revealed that Kepler-78b is 40 times closer to its host star than Mercury to the Sun, and completes a revolution in just 8.5 hours.
11. PSR B1257+12 system
Image Courtesy: NASA/JPL
Did you notice something unusual? Yes, its name. Almost all the exoplanets or the host stars in this list have a distinct pattern in their names but not this one, why? Between 1992 and 1994, astronomers discovered three distinctive exoplanets orbiting around the unusual host star.
The PSR B1257+12, around which these planets are orbiting, is actually a pulsar or dead star which is located in the constellation Virgo at a distance of 2300 light-years from the Sun. Soon after their detection, those three exoplanets became the first-ever confirmed pulsar planets to be discovered by any of the existing observational techniques.
Right now there is another confirmed pulsar planet discovered in 2003, but it’s revolving another pulsar. These extremely rare planetary systems revealed a possibility of the existence of planets in entirely new systems.
Read: Exoplanets Discovered Beyond Milky Way Galaxy Using Quasar Microlensing
10. 55 Cancri e
Image Courtesy: ESA/Hubble
At the time of its discovery, the 55 Cancri e was the first-ever super-Earth, detected to orbit a main-sequence star, predating another super-Earth Gliese 876 d by almost a year. The planet is so close to its host star that it only takes 18 Earth days to complete an orbit. Recent studies revealed that it could be a carbon-rich planet.
9. Kepler-22b
Image Courtesy: NASA/JPL
Kepler-22b is another intriguing exoplanet discovered by NASA’s Kepler mission in 2009. It became the first-ever and the only planet to revolve around a sun-like star Kepler-22, which is situated in the constellation of Cygnus at an estimated distance of 620 light-years.
The exoplanet is dubbed as a ‘Waterworld‘, similar to Gliese 1214 b, but unlike the GJ 1214 b, it’s located inside the habitable zone of the system.
8. Kepler-10b
Image Courtesy: NASA
Located in the Draco constellation at a distance of 564 light-years from Earth, Kepler-10b was the first rocky Earth-like planet detected by the Kepler space mission. Upon its discovery, the far-off planet became instantly popular among astronomers worldwide.
They were excited to study more about Earth-like planets with the help of data collected from the Kepler-10b. Space researchers like Geoff Marcy from the UC Berkeley said this discovery is ‘among the most overwhelming astronomical discoveries in human history.’
7. Kepler-444 system
Image Courtesy: Peter Devine/Tiago Campante
There’s not one but five Earth-sized exoplanets detected in the Kepler-444 system, which makes it one of the most intriguing planetary systems out there other than our own. The Kepler-444 system is among one of the oldest planetary systems with an estimated age of 11.2 billion years.
According to NASA, even though no life could possibly exist on either of these interesting exoplanets due to their extreme proximity to the host star, they could reveal many important things about the formation of the earliest solar systems in our galaxy.
6. CoRoT-7b
Image Courtesy: European Southern Observatory
CoRoT-7b is classified as a super-Earth extra-solar planet which is revolving around COROT-7, a G-type star at a distance of 489 Light Years from the Earth. The important discovery of this rocky Earth-like planet revealed the possibility of the existence of more Earth-like planets and somehow showed that the current search of possibly habitable planets might actually bear fruit someday.
CORoT-7b also has a very short orbital period – it completes one revolution around its host star in less than 24 hours (Earth hour).
5. 51 Pegasi b
Image Courtesy: NASA/JPL
51 Pegasi b or Dimidium (unofficially) belongs to a class of planets known as hot Jupiters. The planet was the first-ever confirmed extra-solar planet revolving around a Sun-like star 51 Pegasi, which marked a new beginning in the field of astronomical exploration.
In 2017, while observing the planet, researchers discovered traces of water on its atmosphere for the first time.
4. Kepler-16b
Artistic impression of Kepler-16A in yellow, Kepler-16B in reddish-orange and Kepler-16 (AB)-b in violet
With a mass similar to Saturn and orbiting not one but two astronomical bodies, the Kepler-16b is the first-ever confirmed example of the unambiguous circumbinary planet. A real-life “Tatooine,” some would say. Various closer studies over the years have revealed that the planet consists of half of ice and rock and half of gas.
3. Kepler-11 system
Image Courtesy: NASA/JPL
The detection of the Kepler-11 system in the constellation Cygnus at 2000 light-years from Earth revealed that a planetary system can also be closely fitted, with as much as five planets within the orbit of Mercury, and can still remain stable.
So far, a total of 6 planets have been discovered revolving around the star Kepler-11. Their estimated mass is between those of Earth and Neptune.
Read: An Extremely Unusual Exoplanet That Shouldn’t Exist
2. HD 209458 b (“Osiris”)
Image Courtesy: ESA/Hubble
HD 209458 AKA Osiris was first detected in 1999 with the help of an astronomical method known as a transit. It was not until 2005 that NASA’s Spitzer Space Telescope measured light directly coming from the exoplanet, making it the first-ever extrasolar planet to be confirmed with this technique.
The unique case of Osiris proved that transit observations of distant planets outside of our solar systems are actually feasible and somewhat reliable.
Read: Exoplanets Discovered Beyond Milky Way Galaxy Using Quasar Microlensing
1. Kepler-186f
Image Courtesy: NASA/SETI/JPL
Detected in 2014, Kepler-186f is the first Earth-like exoplanet discovered in the ‘Goldilocks zone’, the area around a star that has appropriate conditions for water to emerge on the planet’s surface.
Read: Google AI Found A New Exoplanet In Faraway Solar System
Located at the Cygnus constellation, this much-hyped extra-solar planet is about 550 light-years away from Earth, which is why the current technology is unable to study it more closely. In 2015, an essay concluded that Kepler-186f is one of the three best candidates for potentially habitable planets outside our solar system.
