How could we learn about our solar system? How did the planets form, their ends, how did life form on Earth, and are there other life forms in the universe? The key to these questions lies in understanding exoplanets.
Exoplanets, by definition, mean planets outside the solar system orbiting another star.
The first exoplanets were discovered in 1992. The two planets, Poltergeist and Phobetor, were found orbiting a pulsar (a dead star) named PSR B1257+12.
Since then, as of June 2024, there have been 5,632 confirmed exoplanets in 4,188 planetary systems.
The first exoplanets were named by the public in 1992 through naming contests. Later, the International Astronomical Union (IAU) established official naming conventions for exoplanets.
While most exoplanets resemble those in our solar system, some defy imagination with their strangeness. Here are the 10 most extraordinary and weirdest exoplanets discovered so far.
Habitable Planets and Earth Doppelgangers: Life Beyond Earth?
Humanity has always wondered – Are we alone in this vast universe?
In this section, we’ll explore exoplanets with conditions that might allow life to exist and even some uncanny Earth twins!
Kepler 452b – Super Earth
Kepler 452b, also known as Earth’s Cousin due to its similarity in appearance and its 385-day orbit around its star, is located 1400 light years away from the Earth in the constellation Cygnus.
As the name suggests, it orbits the Star Kepler 452. It has a mass roughly 5 times that of Earth and a 50% larger radius.
It is 6 billion years old, which makes it 1.5 billion years older than our sun. Little about its environment is known, but if it’s terrestrial, it will be highly volcanic due to its higher mass.
Kepler 22b – The Ocean Planet That Might Host Life
Located 640 light-years away in the constellation Cygnus, this ocean planet resides within the habitable zone of a star very similar to our sun, Kepler 22.
It is 9 times more massive than Earth and twice in radius. Scientists have ruled out the possibility of earth-like composition and proposed more volatile conditions with liquid or gaseous outer shell by the radial velocity measurement system.
What is the Radial Velocity Measurement System?
Also known as the Doppler spectroscopy method, radial velocity denotes the speed with which the object moves away from the Earth.
Doppler spectroscopy detects exoplanets by observing the star’s spectral line shifts caused by a planet’s gravitational pull (radial velocity measurements) since stars do not stay in constant position.
These shifts indicate the star’s motion towards (blueshift) and away from (redshift) Earth, revealing the planet’s presence and characteristics.
Natalie Batalha, a scientist working on the Kepler Space Telescope project, speculated, “If it is mostly ocean with a small rocky core, it’s not beyond the realm of possibility that life could exist in such an ocean.
Planets That Hold Records
Not all planets are created equal!
We are about to encounter some exoplanets that break the mold, setting records for their size, temperature, or even their age!
PSR B1620-26b “Methuselah” – Oldest Exoplanet Discovered
Also known as Methuselah, after the biblical Methuselah, who lived to be the oldest person.
Not only does it hold the title of the oldest exoplanet ever, but it is also the first circumbinary planet to be discovered.
What Is Circumbinary?
Celestial objects orbiting two stars at once are called circumbinary.
It is believed to be 12.7 billion years old! Which is just 1.1 billion years after the beginning of the universe, which is relatively soon in cosmic terms.
KELT 9 b – Hottest Exoplanet Discovered
Named after the device, it was found using the Kilodegree Extremely Little Telescope by astronomers Scott Gaudi and Denise Stephens in 2016.
It is a large, hot Jupiter planet, roughly 2.5 times the mass of Jupiter.
It is so hot that it breaks down molecules into their constituent atoms such as single-ionized iron and neutral oxygen, on the day side with temperatures reaching 4,600 K (4,327 °C; 7,820 °F— warmer than some red dwarf stars).
However, it bonds again and forms molecules when the temperature cools down during the night side.
TrES-2b – Darkest Exoplanet Discovered
Meet TrES-2b, the hot Jupiter planet located 750 light years away from the solar system.
It reflects less than 1% of the light it receives from its host star, less than charcoal. The Kepler mission confirmed its extremely low albedo (fraction of light that’s reflected) in 2011.
The best-fit model of TrES-2b suggests that its albedo could be 0.04%.
To put it in perspective, the blackest object on earth, “Vantablack,” has an albedo of 0.035%.
K2-33b – Youngest Exoplanet Discovered
K2-33b is a very young super-Neptunian planet, K2-33b is estimated to be 5-10 million years old.
That is, the planet was formed when Hominini, the ancestors of modern humans, started separating from apes.
This planet orbits the star K2-33 and was first detected by NASA’s Kepler space telescope during its K2 mission.
Subsequent observations with the W. M. Keck Observatory and the Spitzer Space Telescope confirmed its existence and age.
K2-33b is notably close to its host star, orbiting about 10 times closer than Mercury does to the Sun, which is unusual for such a young planet.
This discovery provides valuable insights into the early stages of planet formation, as most other known exoplanets are over a billion years old.
Planets That Are Just Weird
Now, we’re about to venture into the strange and unusual. These exoplanets defy easy explanations, with features that have had Astronomers scratching their heads.
PSO J318.5−22 – The Loner/Rogue Planet
Michael Liu, the team leader from the Institute for Astronomy at the University of Hawaii, comments, “We’ve never observed a free-floating object in space that resembles this. It exhibits all the traits of young planets found orbiting other stars, yet it drifts alone in space.”
Yes, a 12 million-year-old Loner planet, freely floating in space approximately 80 light-years away from Earth.
How a gas giant planet would roam freely in space is still unknown. Some theories suggest that due to gravitational perturbations (forces other than the gravitational force due to a single body, i.e., by 2 or more bodies), it may have drifted after it was formed by the nebular hypothesis.
What is the Nebular Hypothesis?
This hypothesis suggests that planetary systems are formed from gas and dust orbiting the star, which clump together to form the planets.
The Poltergeist – PSR B1257+12b
PSR B1257 + 12b, also known as Poltergeist, was one of the first exoplanets to be discovered.
PSR stands for Pulsating Source of Radio. It was one of three exoplanets found to be orbiting the pulsar named Lich.
What are Pulsars?
A highly magnetized, rotating neutron star that emits beams of electromagnetic radiation
The other planets were named Phobetor (found in 1992) and Draugr (found in 1994).
All three of these planets are bathed in radiation due to them orbiting a pulsar.
The name “Poltergeist” was assigned because it fits the eerie and mysterious nature of a planet orbiting a pulsar.
Gliese 504 b – The Pink Planet
Also known as GJ 504 b, this gas giant exoplanet has a dull magenta or pinkish color.
It was discovered in 2013 using direct imaging techniques with the Subaru Telescope in Hawaii.
The planet glows with a magenta hue from the residual heat of its formation, with surface temperatures around 237.8°C (460°F).
The pink is due to specific wavelengths of light emitted and scattered by the various gases present in its atmosphere, primarily methane.
The planet’s young age, estimated at around 160 million years, means it hasn’t had enough time to cool down significantly since its formation.
Gliese 504 is still contracting and radiating the leftover heat from its initial formation processes.
This heat makes the planet glow, similar to how a heated metal glows as it cools down.
COCONUTS-2b – Long Distance Relationship Planet
COCONUT-2b or COol Companions ON Ultrawide orbiTS-2b or WISEPA J075108.79-763449.6 is a gas giant exoplanet with 6.3 times the mass of Jupiter.
COCONUT-2b takes 1.1 million years to orbit around its host star L 34-26 and is located 7506 Astronomical Units (1 AU = 150 million kilometers/93 million miles) away from L 34-6.
This means the distance between COCONUT-2b and its host star is 7506 times greater than the distance between Earth and the Sun.
It holds the record for the largest orbit around a single star.
