12 out-of-this-world exoplanet discoveries in 2023

Conor Feehly

December 25, 2023 at 2:00 AM·8 min read

Various colored circles circled by dotted lines scattered about a black canvas.

This year saw planetary scientists add a number of exciting new worlds to our growing 5,000+ catalog of exoplanets. Among them are planets like we have never seen before. Here is a look back at some of the standout exoplanet discoveries of 2023.

1. JWST Identifies Heavy Elements in Distant Gas Giant's Atmosphere

Exoplanet Smertrios is a hot Jupiter exoplanet with an atmosphere that defies expectations.

Earlier in the year, observations made with the James Webb Space Telescope (JWST) confirmed the presence of heavy elements — carbon and oxygen — in the atmosphere of the distant exoplanet HD149026b. The planet is more commonly known as Smertrios.

The discovery came as a surprise to astronomers, as gas giants from our own solar system, such as Jupiter and Saturn, predominantly house only hydrogen and helium in their atmospheres. The general rule tends to be, the bigger the planet, the less heavy elements in its atmosphere. The discovery turned this idea on its head.

2. TESS Spots World With Long Orbital Period and Cold Surface Temperatures

a large wavy-striped planet hangs in space. a star can be seen burning in the disance next to the crescent of another planet.

NASA's Transiting Exoplanet Survey Satellite (TESS) has added roughly 2,000 worlds to our menu of exoplanets, however, one particular planet, a gas giant called TOI-4600c stood out to planetary scientists.

Most discovered exoplanets orbit very close to their home star, however, TOI-4600c orbits its star every 482.82 days or 16 months. This gives it the longest year for any planet discovered by TESS. The gas giant is also a cool -110 degrees Fahrenheit, or -78 degrees Celsius at the surface.

3. Rare Planetary System Has Six Close Orbiting 'sub-Neptunes'

an orange star is orbited by six planets, each a different color. their orbits are outlined with white circles

Located only 100 light-years from our solar system, scientists spotted a planetary system where six planets orbit extremely close to their parent star — so close, in fact, that all six planets could fit within the distance between Mercury and our sun.

Astronomers also believe the planetary system has remained unchanged for over a billion years, as the planets orbit in close to perfect mathematical resonance.

4. Massive Planet Discovered Orbiting Tiny Star

the top half of a large purple orb raises from the bottom like an eye peering upward, its diameter spanning the bottom of the image, near its top, lighter purple in the shape of an eye, with a red/orange iris and yellow pupil. a small orange/yellow sun hangs above in the center. Illustration shows a massive planet in orbit around a diminutive star.

In research which challenged planetary scientist's notions of what is possible, a massive exoplanet named LHS 3154 b, which is 13 times more massive than Earth, was found to be orbiting an ultracool dwarf star.

The planet resembles Neptune in size, while the star is nine times less massive than the Sun. The ratio between the Neptune-sized world and its parent star, which is 51 light-years away, is 100 times greater than the mass ratio between Earth and sun.

5. Astronomers Capture Longest Video of Travelling Exoplanet

An illustration shows Beta Pictoris b orbiting its parent star

Using 17 years of data, astronomers created a time-lapsed video of the orbit of the exoplanet Beta Pictoris b. The data was condensed into 10 seconds of footage, which captures 75% of the planet's orbit around its parent star which takes 23 Earth years to complete.

The planet is located in a system 64 light-years from Earth, and the planet itself has a mass 12 times that of Jupiter, the largest planet in our solar system.

6. Trappist System Planets Resemble Mercury

A blazing red star is seen with just part of a planet in the foreground.

Observations with the JWST's Mid-Infrared Instrument (MIRI) found that two inner planets of the Trappist planetary system likely do not have atmospheres. TRAPPIST-1b, which is a little more massive than Earth, is likely a bare rock with no atmosphere, with a scorching surface temperature of 232 degrees Celsius (450 degrees Fahrenheit).

The results were followed up withstrasdf similar findings for TRAPPIST-1c, the next planet in the system, three months later. Astronomers put the lack of atmospheres in these planets down to violent activity of their home star.

7. Mini Neptune Cloaked in Haze Unlike Anything From Our Solar System

a planet with a hazy grey atmosphere in space

Planetary scientists aimed the JWST at a 'mini-Neptune' planet named Gliese 1214 b, and found that it was surrounded by a dense haze or cloud layer. Gliese 1214 b had initially proven difficult to observe due to its reflective atmosphere, but researchers believe it's possible the planet contains high amounts of water vapor.

The 48 light-year away planet orbits very close to its home star however, so it's unlikely to hold any liquid oceans at the surface. Mini-Neptunes, which are planets that are smaller than Neptune, but larger than Earth, are curiously absent from our own solar system.

8. Metallic Clouds on Planet Act as Gigantic Cosmic Mirror

An illustration of the exoplanet LTT9779b as it orbits its star

Astronomers identified an exoplanet called LTT9779 b which reflects a whooping 80% of light that shines on it from its parent star. Comparatively, Earth reflects 30% of its light. The ultra-hot planet, which is 264 light-years from Earth, is exceptionally reflective due to the high proportion of metals in its atmosphere.

With the planet being five times as wide as Earth, it earns the title of "largest cosmic mirror ever discovered."

9. Scientists Observe Planet Losing Its Atmosphere

An artist’s illustration shows a gas giant planet (lower right) closely orbiting its host star (left), with another star in the distance (upper right). The two stars are themselves in orbit with each other.

Astronomers have observed an exoplanet, roughly 950 light-years from Earth, explosively losing its atmosphere due to its extremely close proximity to its home star. The planet, known as HAT-P-32 b has a mass around 68% that of Jupiter but is twice as wide as the solar system's largest planet.

HAT-P-32 exists just 3.2 million miles from its parent star, or about 3% of the distance between Earth and the sun, and completes an orbit every 2.2 days. This proximity means the gas giant is roasted by radiation from its parent star, classifying HAT-P-32 b as a "hot Jupiter" planet. Astronomers monitored the trailing gas tail of HAT-P-32 b created from helium flowing from its atmosphere with telescopes from Earth.

10. Binary Star System Home to Dual Worlds

two suns in the night sky over a rocky planet

While binary star systems, where two stars orbit each other, are common in the cosmos, it is far less likely that these systems harbor planets. That's because binary stars are likely to stir up planetary forming disks during the adolescent phase of planetary systems. Only one such binary system was known to host multiple planets, however, earlier in the years, scientists discovered another multi planetary system orbiting a pair of stars.

Astronomers investigated the binary system TOI-1338, located about 1,320 light-years from Earth, and discovered a circumbinary planet dubbed TOI-1338b orbiting TOI-1338's pair of stars. In their failed attempts to measure the mass of the planet, they discovered another planet.

11. Scorched World Has Atmosphere of Vaporized Rock

On a planet where temperatures reach 4,350 degrees Fahrenheit (2,400 degrees Celsius), which is hot enough to vaporize iron, researchers identified 11 chemical elements abundant in the atmosphere which indicate the atmosphere is composed of rock-forming elements.

Located some 634 light-years away, the roasted planet gets its temperatures from its close proximity to its star. Classified as an "ultra-hot Jupiter," which is a massive planet that exists incredibly close to its star, the exoplanet is a twelfth of the distance from its star, WASP-76, than Mercury is to the sun.

12. TESS Data Reveals Eight 'Super-Earths'

Color illustration of a rocky planet on the left and a portion of a much-larger star on the right. About three-quarters of the lit side of the planet is visible; the other quarter is in shadow. The surface of the planet has gray, orange, and yellow mottling. Most of the orange and yellow is in the region that is facing the star directly. The grayer portions are toward the poles and shadowed side of the planet. The edge of the disc of the planet appears to be glowing, suggesting a thin atmosphere. The star is bright orange-yellow, with a turbulent appearance similar to the Sun.

With data captured from NASA's Transiting Exoplanet Survey Satellite (TESS), scientists identified eight new exoplanets considered to be 'super-Earths', a class of exoplanet that is larger than Earth but smaller than Neptune.

Astronomers are particularly interested in super-Earths, as they represent a gap in exoplanet data, namely a scarcity of planets of that particular mass. By identifying more super-Earths, researchers hope they may be able to understand why this gap in exoplanet data exists.

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