According to a paper recently published in the journal Nature, a record number of seven possibly-habitable exoplanets orbiting around a single star have been discovered. This is an exciting discovery, as it is a huge step forward in our chase of a “second Earth”. With the discovery of these many Earth-sized planets, the possibility of answering the age-old question of exterrestrial life becomes more hopeful.
“The discovery gives us a hint that finding a second Earth is not a matter of if, but when,” said Thomas Kutcher, an associate administrator of the science mission directorate at NASA’s Washington headquarters.

The planets were found by an international group of astronomers and are located about 40 light years away from Earth in the constellation Aquarius. This exoplanet system is called TRAPPIST-1, after the Transiting Planets and Planetesimals Small Telescope that was used to find them. Their star is an ultra-cool dwarf, allowing liquid water to exist on planets that are closer to the star than the distance between our star and Mercury. The short distance also results in the planets being very clustered together and possibly tidally locked to their star, causing perpetual day and nights.

Using NASA’s Spitzer Space Telescope, a team of astronomers were able to accurately measure the size and precisely estimate the density of these planets. Based on the information attained, all of the TRAPPIST-1 planets are likely to be rocky, leading to the possibility of them being water-rich or having liquid water on their surface.

“The seven wonders of TRAPPIST-1 are the first Earth-size planets that have been found orbiting this kind of star. It is also the best target yet for studying the atmospheres of potentially habitable, Earth-size worlds,” said Michael Gillon, lead author of the paper and principal investigator of the TRAPPIST exoplanet survey at the University of Liege, Belgium.

Three of the seven planets are in the habitable zone of their system. The habitable zone is the region around a star where a rocky planet is likely to have liquid water.
This groundbreaking discovery brings hope to scientists currently searching for signs of life beyond our solar system. This suggests that Earth-sized worlds are much more common in the Milky Way galaxy than previously thought.

“With this amazing system, we know there must be many more potentially life-bearing worlds out there waiting to be found,” said Sara Seager, a professor of planetary science and physics at MIT.