Astrobiology Top 10: Exoplanets: 1,000 and Counting
The Extrasolar Planets Catalog now has over 1,000 planets listed in their database.
The milestone was reached October 22, and their current count of planets discovered beyond our solar system now sits at 1,010.
[Meanwhile NASA’s Exoplanet Archive only lists 919, indicating there are differences in how scientists keep a tally on exoplanet detections]
Philosophers have long surmised that vast numbers of planets orbit stars throughout the universe. But the first published discovery of an exoplanet that was later confirmed didn’t happen until 1988.
Since then, a flood of discoveries have occurred thanks to new scientific techniques such as the radial velocity method, the transit method, and gravitational lensing. And sophisticated missions like the Kepler Space Telescope have added greatly to the planet count.
In fact, Kepler still has over 3,500 unconfirmed planet “candidates”. Follow-up observations should confirm whether or not the data collected by Kepler actually represent planets, greatly adding to the Extrasolar Planets Catalog.
We’re still a long way from the “billions and billions” of planets predicted, but with upcoming missions like TESS and the James Webb Space Telescope, we’re well on our way to discovering at least thousands more. And maybe a fair number of those will be habitable worlds.
"We now estimate that if we were to look at 10 of the nearest small stars we would find about four potentially habitable planets, give or take," stated Ravi Kopparapu, a post-doctoral researcher in geosciences at Penn State, in a recent press release. "That is a conservative estimate," he added. "There could be more."
Here’s a graph showing the types of planets we’ve discovered so far.
When planet discoveries were first being made, most of the planets were hot Jupiters (or “hot Jovians”) — simply because those types of planets are easiest to find with current detection techniques. But as the searches went on, astronomers found less-massive planets with longer-period orbits around their stars.
The Planetary Habitability Laboratory has its own graph of “potentially habitable exoplanets” that have been discovered so far:
Planetary scientists still argue about what makes a planet “habitable”, but in the meantime astronomers are discovering more and more worlds that both surprise us and give us a hope that we’ll soon find worlds that are remarkably like our own planet Earth.