In the last few decades, we went from knowing the existence of just a handful of planets to the realization that planets are extremely common in our galaxy. Since then, thanks to advancements in both ground- and space-based telescopes, the number has continued to grow. Now NASA has confirmed we have passed the 5,000 mark of confirmed exoplanets, with 5,005 strange new worlds orbiting in the Milky Way.
“It’s not just a number,” Jessie Christiansen, science lead for the Exoplanet Archive and a research scientist with the NASA Exoplanet Science Institute, said in a statement. “Each one of them is a new world, a brand-new planet. I get excited about every one because we don’t know anything about them.”
The first exoplanet – well, the first two – was announced on January 9, 1992, by radio astronomers Aleksander Wolszczan and Dale Frail. These two worlds were orbiting the pulsar PSR 1257+12, a special kind of neutron star, the compressed core of a star that went supernova.
“If you can find planets around a neutron star, planets have to be basically everywhere,” Wolszczan said. “The planet production process has to be very robust.”
These 5,005 planets (and maybe 8,500 candidates yet to be confirmed) are but a drop in the ocean of all the planets that are expected to exist in our galaxy. Hundred of billion worlds are there to be discovered, some we haven't seen up close before, such as Hot Jupiters and super-Earths.
And with so many worlds out there, there is obviously the question of life. Will we find evidence that some of these worlds are inhabited? Something for upcoming telescopes to puzzle out, for sure, but the evidence is building that the foundational chemistry of life on Earth has close connections to molecules and chemistry seen elsewhere in the universe. Our little corner of the cosmos is hopefully not that special.
“To my thinking, it is inevitable that we’ll find some kind of life somewhere – most likely of some primitive kind,” Wolszczan said.
Of the 5,005 worlds discovered, 30 percent of them are gas giants like Jupiter and Saturn. Thirty-five percent are Neptune-sized, while 31 percent are Super-Earths, a few times bigger than our planet but not quite as big as Neptune. And finally, 4 percent are terrestrial, small rocky planets the size of Earth or smaller.
There is still so much to find out about these distant worlds: how they formed, how they evolved, and what they are like at this moment. This milestone is just a reminder to go further and discover even more.