On Wednesday, NASA confirmed that the tally of discovered and identified exoplanets has surpassed 6,000.
Acting director of NASA’s astrophysics division, Shawn Domagal-Goldman, said in a statement that the milestone “represents decades of cosmic exploration driven by NASA space telescopes – exploration that has completely changed the way humanity views the night sky”.
He says that NASA and the United States will “lead the next giant leap – studying worlds like our own around stars like our sun”.
The milestone figure comes 30 years after the first exoplanet was discovered in 1995, a star similar to Earth’s sun, 51 Pegasi B. The consistent work towards discovering new exoplanets signifies the curiosity and exploration for the universe around us, and the search for potential life outside Earth.
“If we want to find out if we’re alone in the universe, all of this knowledge is essential,” said Dawn Gelino, head of NASA’s Exoplanet Exploration Program in a statement.
What are exoplanets?
NASA defines exoplanets as any planet in the Milky Way galaxy beyond our solar system. The majority of them orbit other stars; however, there are few known as “rogue planets” which are untethered to any star.
Though fewer than 100 exoplanets have been directly imaged due to their parent star’s light making them faint to space photography technology, researchers believe there are billions of undiscovered exoplanets floating through our galaxy.
Of the now 6,007 exoplanets identified, 2,035 of them are categorised as “Neptune-Like”, which NASA characterises as having “hydrogen and helium-dominated atmospheres with cores of rock and heavier metals”. There are 1,984 exoplanets classified as “gas giants”, made of mostly helium and/or hydrogen, similar to Jupiter in our solar system. A total 1,761 “Super-Earths” have been identified and while they do not provide any habitable or Earth-like characteristics, their namesake comes from their size, being smaller than Neptune-like planets but bigger than Earth. And 220 Terrestrial exoplanets have been found, which are rocky, iron-rich planets, similar to Mercury or Venus. The remaining seven exoplanets are unknown as to which category they fall under.
Though the rate of identification has accelerated drastically in recent years, with only 5,000 exoplanets identified just three years ago, the process is lengthy and complex. Thousands of potential exoplanet candidates are still awaiting confirmation, as all candidate planets must be confirmed through follow-up observations, which is both a lengthy and costly procedure.
The search for life continues on
The work to find habitable, life-sustaining planets in our galaxy remains paramount in astronomical research and exoplanet hunting. NASA says that to discover if a confirmed exoplanet is hospitable to life, scientific research and discovery will “emphasise finding rocky planets similar to Earth and studying their atmospheres for biosignatures – any characteristic, element, molecule, substance or feature that can be used as evidence of past or present life”.
In a video celebrating the milestone, NASA said, “We’re entering the next great chapter of exploration, worlds beyond our imagination.
“To look for planets that could support life, to find our cosmic neighbors and to remind us the universe still holds worlds waiting to be found.”