Up until the mid 1990s, astronomers didn't know for certain if there were any planets outside of our own solar system. But ever since the first exoplanet was discovered, it’s been increasingly clear that our Sun isn’t the only one in the universe with a handful of planets orbiting it.
Over the last three decades, astronomers have confirmed 5,557 exoplanets in the universe. While that already seems like a high number of exoplanets, scientists actually believe that the universe is teeming with trillions of them. Makes sense, given a single galaxy can contain billions of stars and there are an estimated two trillion galaxies. The problem is that exoplanets are still relatively hard to find.
Since they are so far away and don't produce their own light like stars, exoplanets are much fainter than the stars they orbit, making it tricky to spot them. But technology is catching up and progress is being made thanks to the massive space telescopes, like NASA’s James Webb Space Telescope (JWST), that are able to observe exoplanets based on a variety of methods.
This is all part of a bigger search to answer a question that humans have asked since the dawn of time: Are we alone? As NASA explains, Earth is the only planet we know of with life on it “so far.” But as scientists search for exoplanets, they’re also trying to figure out if there are signs that life could exist on those planets. In other words, the search for exoplanets could lead to the discovery of extraterrestrial life.
Astronomers and astrophysicists search for extraterrestrial life on exoplanets by looking for biosignatures, such as water, oxygen or chlorophyll. They also look to see if these planets are in the “habitable” zone of its host star or not, meaning that it’s the right enough distance that the planet could sustain life as we know it and likely to have a body of water on it.
The year 2023 kicked off with big exoplanet news when JWST confirmed its first exoplanet, bringing astronomers closer to a new understanding of Earth-like worlds outside our solar system. Formally classified as LHS 475 b, astronomers estimated that the planet is almost the same size as Earth. Since JWST is capable of characterizing the atmospheres of exoplanets, the team at the time couldn’t conclude which molecules were present in the exoplanet’s atmosphere. However, they were able to conclude that that planet is a few hundred degrees warmer than Earth, making it unlikely that life exists on it.
Most excitingly, this was just the first of exciting exoplanet news to take hold over the year. Here’s a year review in exoplanet news marking a year where we’re closer to finding life somewhere else in the universe.
01
Scientists discover potentially habitable TOI 700 e
Located about 100 light-years away, scientists announced this year that they believe the exoplanet TOI 700 e could be habitable for life. Scientists estimated that this exoplanet is 95% Earth’s size and likely rocky, too. While three other planets have also been discovered in this star system, astronomers needed specific TESS observations to discover TOI 700 e.
“This is one of only a few systems with multiple, small, habitable-zone planets that we know of,” said Emily Gilbert, a postdoctoral fellow at NASA’s Jet Propulsion Laboratory at the time. “That makes the TOI 700 system an exciting prospect for additional follow up.”
Newly discovered Earth-size planet TOI 700 e orbits within the habitable zone of its star in this illustration. Its Earth-size sibling, TOI 700 d, can be seen in the distance. (NASA/JPL-Caltech/Robert Hurt)
02
Astronomers discover ‘Earth-like’ exoplanet named Wolf 1069 b
In February 2023, a team of international astronomers announced that they discovered an exoplanet that was remarkably similar to Earth and pretty close to us, at least on a galactic scale. The details of the discovery were published in the journal Astronomy & Astrophysics, which noted that the new planet, dubbed Wolf 1069 b, had roughly 1.26 of the Earth's mass and about 1.08 its size. But perhaps the most interesting detail was that Wolf 1069b is located in the habitable zone of its host star, meaning that liquid water could exist on its surface.
At the time, astronomers said the new exoplanet was very reminiscent of Proxima Centauri b, which is the nearest potentially habitable exoplanet to our solar system. But unlike Earth, Wolf 1069 b is tidally locked, meaning that one side is always facing its star. This means it experiences never-ending daylight while its opposite side is bathed in eternal night. As a result, astronomers believe that if life is habitable here, it would only exist on the daytime half. While the next step would be to search for biosignatures on Wolf 1069 b, astronomers said at the time that we would have to wait a decade, because the technology just isn’t there yet.
03
Scientists discover massive exoplanet 13 times the mass of Jupiter, named TOI-4603b
Astronomers aren’t only interested in discovering exoplanets with biosignatures that are in their solar system’s habitable zones. Every exoplanet discovered has the potential to tell scientists more about the origins of planet formation, the universe and life. In March 20233, news broke that NASA’s TESS discovered a massive exoplanet that had a mass of 13 Jupiters. Named TOI-4603b , the exoplanet is believed to be located 730 light-years away with an orbital period of 7.2 days. It wowed scientists not only because of its size, but because it could also belong to a new category of planets that is not quite fully understood.
04
Scientists discover a ‘warm Jupiter’
A planet with a mass 13 times that of Jupiter is interesting on its own. But another discovery made headlines in 2023 not only for also being bigger than Jupiter, but for how hot it could be. Designated TOI-4127 b, scientists estimated that this exoplanet located 1,061 light-years away from Earth could have a surface of nearly 630º Fahrenheit.
Astronomers theorized this could eventually turn into what they describe as “hot Jupiters,” which is a type of exoplanet that orbits their stars at an extremely close distance. The authors of a paper published about the exoplanet stated that it’s possible these “warm Jupiters” spend part of their lives on elliptical orbits before shifting to orbits that bring them closer to their stars which is when they transition to being a “hot Jupiter.”
05
Another ‘Super-Earth’ discovered by TESS
Located only 120 light years from Earth, Scientists discovered exoplanet TOI-1680 b in 2023 and found that it is about 50 percent bigger than Earth and orbits an M-dwarf star. The exoplanet is believed to orbit its host star every 4.8 days. Astronomers believe Super-Earths are rocky worlds. To date, 1,679 have been discovered.
At the time, astronomers said this “Super Earth” exoplanet could be a good candidate for atmospheric characterization by JWST which could potentially review the presence of water molecules and help astronomers better understand the atmospheres of Super-Earths.
Newly discovered Earth-size planet TOI 700 e orbits within the habitable zone of its star in this illustration. Its Earth-size sibling, TOI 700 d, can be seen in the distance. (NASA/JPL-Caltech/Robert Hurt)
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