The Most Bizarre Exoplanets As NASA Discoveries Top 5,000

NASA's catalog of planets discovered outside the solar system, known as extrasolar or exoplanets, has reached an incredible milestone with over 5,000 worlds now identified.

The number of exoplanets exceeded 5,000 on March 21 when 65 new worlds were added to the NASA Exoplanet Archive. The archive records exoplanet discoveries that appear in peer-reviewed, scientific papers, confirmed using multiple detection methods or by analytical techniques. Some are like nothing found within our solar system.

The feat is even more impressive considering the fact that until the early to mid-nineties we had yet to discover a planet outside our solar system.

One of the most common types of planets discovered outside the solar system are hot Jupiters. These are worlds that have a similar composition to the solar system's most massive planet, the gas giant Jupiter, and orbit extremely close to their parent star.

They can also have a mass up to 12 times that of Jupiter and have shapes that are deformed by their extreme proximity to the intense gravitational influence of their star.

Thomas Mikal-Evans of the Max Planck Institute for Astronomy told Newsweek hot Jupiters are "interesting because they're so unlike anything in our own solar system.

"It's fascinating to work out what would happen in the atmosphere of a planet like Jupiter if it's orbiting 15 times closer to its star than the Sun-Mercury distance, and then to go and test those predictions."

Raining Liquid Sapphire On Hot Jupiters

Mikal-Evans was part of a team that investigated the atmospheric conditions of the hot Jupiter WASP-121b, located around 850 light-years from Earth. They discovered that because the planet is so close to its star and tidally locked so that one side perpetually faces it, temperatures are great enough at around 6,000 degrees Fahrenheit to vaporize metal.

The truly alien aspect of WASP-121b occurs when these metal clouds are blown from the planet's permanent dayside reaching its perpetual, and much colder nightside. This causes the metals, particularly titanium and aluminum, to turn to liquid and rain on the planet's surface.

Mikal-Evans said: "Aluminum, in particular, would probably condense in the form of corundum which when mixed with other trace elements like chromium, iron, and titanium, makes the minerals ruby and sapphire."

This means that the space-facing nightside of WASP-121b could be experiencing rains of liquid ruby and sapphire.

WASP-121b
An illustration of WASP-121b, one of the most alien exoplanets ever discovered. The world is so hot on its tidally locked dayside that metal vaporizes and is then blown to the nightside where it rains to the surface. ESA/G. Bacon STSci/NASA G. Bacon STScI/NASA/ESA

Another consequence of hot Jupiter's close proximity to their parent star is their incredibly short orbits. Some of these worlds have years that last no longer than 24 hours.

In March, Newsweek reported on the discovery of such a world. GJ 367b is an exoplanet located 31 light-years from Earth that has an orbit, and therefore a year, that lasts no longer than 8 hours. The proximity of this hot Jupiter to its red dwarf host star also means it is bombarded by radiation around 500 times more intense than that experienced by Earth.

Don't Judge An Exoplanet By Its Appearance

While these hot Jupiters have appearances that hint at their hellish surface conditions, not all exoplanets should be judged by their outward appearance. One such world is HD 189733 b, which from space resembles a tranquil, glassy blue marble.

HD 189733 b
A illustration of HD 189733 b. Don't be fooled by this planet's tranquil appearance, on its surface winds many times the speed of sound send glass rains slicing sideways rather than falling to the ground. M. Kornmesser/ESO

At the surface of this world, discovered in 2005, however, winds of around 5,400 miles per hour—seven times the speed of sound—causing glass rain to slash through the air, falling sideways rather than falling to the ground.

Of course, the search for exoplanets isn't just limited to finding extreme worlds. Astronomers are also searching for worlds that are analogous to the planets of the solar system.

Especially rocky or terrestrial worlds similar to Earth that exist in their star's habitable zone, or the distance that allows temperatures "just right" for liquid water to exist. And searching for these conditions means engaging in the search for life elsewhere in the Milky Way.

But, just because these planets are similar to Earth in some ways, does not mean they can't be radically different in others. Super-Earths are rocky worlds that have a radius of up to four times that of our planet.

Gliese 1132 b is a super-Earth located around 40 light-years from earth. The exoplanet is so close to its red dwarf star that it is being stretched and squeezed by intense tidal forces.

This causes violent volcanic activity on the planet, which resulted in it growing a second atmosphere composed of volcanic gases after its initial atmosphere was stripped due to intense radiation from its star.

Weird Exoplanets Come in All Sizes

Not all exoplanets are strange and alien because of their imposing size or violent conditions, however. Exoplanet hunters are frequently turning up planets outside the solar system that are remarkable for how small or light they are.

L 98-59b size comparison
A diagram showing how L 98-59b compares in size to some other planets, including Earth. Goddard Space Flight Center/Conceptual Image Lab/NASA

One such example is L 98-59b, a planet that orbits a star located around 35 light-years from Earth. Discovered in 2019, this exoplanet has a mass half that of Venus, making it the smallest planet spotted at the time using the so-called radial velocity method that measures the movement of the star caused by the presence of the planets.

An incredibly light exoplanet was discovered just this year at a distance of around four light-years, orbiting Proxima Centauri, the closest star to the sun. The planet designated Proxima d has a quarter of the mass of Earth, making it one of the lightest exoplanets ever discovered.

The fact astronomers could uncover this world at all is an exciting promise of things to come for exoplanet hunting, which will also get a considerable boost when the James Webb Space Telescope begins operations later this year.

Exoplanet line up
An illustration of exoplanets in NASA's Exoplanet Archive. The number of worlds documented in this catalog has exceeded 5,000. NASA