NASA announced on Monday that it has added the 5,000th alien world to its Exoplanet Archive marking a big milestone for planetary science.
“The 5,000-plus planets found so far include small, rocky worlds like Earth, gas giants many times larger than Jupiter, and ‘hot Jupiters’ in scorchingly close orbits around their stars,” officials at NASA’s Jet Propulsion Laboratory (JPL) in Southern California said in a statement.
“There are ‘super-Earths,’ which are possible rocky worlds bigger than our own, and ‘mini-Neptunes,’ smaller versions of our system’s Neptune,” JPL officials added. “Add to the mix planets orbiting two stars at once and planets stubbornly orbiting the collapsed remnants of dead stars.”
The NASA Exoplanet Archive is housed at the California Institute for Technology (Caltech). To be added to the catalog, planets must be independently confirmed by two different methods, and the work must be published in a peer-reviewed journal.
The first exoplanets were found in the early 1990s. While telescopes on the ground and in space have done well to get the count to 5,000 since then, Jessie Christiansen, science lead of the NASA Exoplanet Archive, stated on Caltech’s website that the worlds found to date are “mostly in this little bubble around our solar system, where they are easier to find.”
“Of the 5,000 exoplanets known, 4,900 are located within a few thousand light-years of us,” Christiansen added.
“And think about the fact that we’re 30,000 light-years from the center of the galaxy; if you extrapolate from the little bubble around us, that means there are many more planets in our galaxy we haven’t found yet, as many as 100 to 200 billion. It’s mind-blowing.”
The first confirmed planetary discovery came in 1992, when astronomers Alex Wolszczan and Dale Frail published a paper in the journal Nature. They spotted two worlds orbiting a pulsar (a rapidly rotating, dense star corpse) by measuring subtle changes in the timing of the pulses as the light reached Earth.
Ground-based telescopes did the heavy lifting in those early years, and it took several more searches to finally uncover the first planet around a sun-like star in 1995.
“Some Kind of Life Exists Somewhere”
The Transiting Exoplanet Survey Satellite (TESS), launched in 2018, continues to make new exoplanet discoveries.
But soon powerful next-generation telescopes and their highly sensitive instruments, starting with the recently launched James Webb Space Telescope, will capture light from the atmospheres of exoplanets, reading which gases are present to potentially identify tell-tale signs of habitable conditions.
The Nancy Grace Roman Space Telescope, expected to launch in 2027, will make new exoplanet discoveries using a variety of methods. The ESA (European Space Agency) mission ARIEL, launching in 2029, will observe exoplanet atmospheres; a piece of NASA technology aboard, called CASE, will help zero in on exoplanet clouds and hazes.
“To my thinking, it is inevitable that we’ll find some kind of life somewhere – most likely of some primitive kind,” Alexander Wolszczan, the lead author on the paper that, 30 years ago, unveiled the first planets to be confirmed outside our solar system said.
The close connection between the chemistry of life on Earth and chemistry found throughout the universe, as well as the detection of widespread organic molecules, suggests detection of life itself is only a matter of time, he added.