Science fiction has longed played with the question of whether life exists beyond Earth. This same question has also motivated researchers to search for planets capable of sustaining life, especially given that our Sun has about five billion more years left until it swells and consequently consumes Earth.
Recently, a team of international researchers discovered a collection of seven planets outside of our solar system that may be able to sustain life. Detected by the Spitzer Space Telescope (SST), these planets orbit a single star and are all approximately the same size as Earth. Three out of the seven planets are considered to be in the habitable zone based on their distance from the burning star.
Thomas Zurbachen, the associate administrator of the agency’s Science Mission Directorate in Washington, views the study’s findings as a step closer to determining whether there is life beyond Earth.
“Answering the question ‘Are we alone?’ is a top science priority and finding so many planets like these for the first time in the habitable zone is a remarkable step forward toward that goal,” Zurbachen said in a NASA press release.
These seven planets, also known as exoplanets, are only a few of the 3,500 exoplanets confirmed in the universe, but are still remarkable due to their size and Earth-like qualities. The collection of planets is about 40 light years from Earth, which converts to 235 trillion miles.
The team first reported on the system in May 2016 after collecting data using the Transiting Planets and Plantesimals Small Telescope (TRAPPIST). The researchers initially found only three planets in the system. TRAPPIST was used to study the changes in brightness of the star, which was later given the name TRAPPIST-1. To their surprise, researchers observed shadows similar to eclipses, which interrupted the pattern of starlight. They interpreted these shadows as belonging to orbiting planets.
As a follow-up to the initial discovery, the ground based European Southern Observatory’s Very Large Telescope and SST, verified the existence of two of those planets and detected an additional five planets. The SST, which was launched in 2003, follows behind Earth as it orbits the Sun. This infrared telescope detects long wavelengths emitted by objects in space that we cannot see with our eyes. Stars are also known to glow the brightest in infrared light. The SST was used to measure the size and estimate the mass of six out of the seven planets.
Based on the computed densities, scientists suggest that most of the planets were likely to be rocky. The lengths of their orbits have been estimated to range from one and a half to about 13 earth days for planets closest to the star and those more distant, respectively.
Interestingly, the exoplanets orbit around an ultra cool dwarf star. As you can infer from the name, this star is colder, and is half the temperature of our Sun. It is also one-tenth of the Sun’s mass. The dwarf star is much younger than our Sun and is expected to continue burning for an additional 10 trillion years, about nine trillion years longer than our Sun will burn.
Furthermore, these seven exoplanets are spaced very closely to one another. If humans were to stand on one of these exoplanets and look up into the sky, they would see the nearest planet, similar to how humans on Earth see the Moon. The exoplanets are also considered to be tidally locked to their star, which means that each side of the planet is either in perpetual day or night, which can lead to various different weather patterns and extreme temperature changes on each planet.
This finding has spurred excitement in the scientific community. Sean Carey, the manager of NASA’s Spitzer Science Center at the California Institute of Technology and the Infrared Processing and Analysis Center in Pasadena, California, expressed the remarkability of the study.
“This is the most exciting result I have seen in the 14 years of Spitzer operations,” said Carey in an interview with CNN. “Spitzer will follow up in the fall to further refine our understanding….More observations of the system are sure to reveal more secrets.”
The next step in the team’s investigation is to determine whether these planets contain liquid water, given how essential this resource is on Earth. NASA’s Hubble Space Telescope has begun its preliminary survey of four of the planets, three of which are considered to be in the habitable zone. Researchers are interested in studying whether these planets have high concentrations of hydrogen, which would render the planets inhospitable to living organisms.
Researchers are primarily interested in the composition of the exoplanets’ atmosphere and whether they posses the molecules vital to life such as water, methane, oxygen and ozone, as well as whether they demonstrate temperatures and surface pressures analogous to Earth’s.