A space telescope designed to reveal unprecedented details about exoplanets, which are worlds beyond our solar system, launched early Wednesday morning from French Guiana. You can watch footage of the launch at this link.
The CHaracterising ExOPlanet Satellite (CHEOPS), a joint mission by the European Space Agency and the Swiss Space Office, is the first mission to focus on small exoplanets that have already been discovered orbiting bright stars.
While its predecessors, such as NASA’s Kepler spacecraft, were geared toward finding new exoplanets, CHEOPS will characterize the atmospheres and densities of catalogued worlds, as well as their potential to host life.
“The question of whether there is life beyond our solar system, or are we alone, is possibly one of the most profound we can ask ourselves, and one that many people (not just scientists) have been asking or a very long time,” said Kate Isaak, the project scientist for CHEOPS, in an email.
The spacecraft, which launched at 3:54AM EST, will help address this question by training its sights on exoplanets that have a mass range from Earth to Neptune (Neptune is about 17 times as massive as Earth).
This category includes rocky planets like Earth and Mars, small gas worlds like Uranus and Neptune, and “Super-Earths,” a type of planet our solar system lacks, which are several times bigger than Earth but much smaller than Neptune.
CHEOPS will use a highly sensitive photometer to capture an enhanced view of exoplanet transits, which occur when planets pass in front of their host star from the spacecraft’s perspective. The mission may also discover moons or ring systems around some exoplanets with this technique.
While the masses of the target worlds are known, CHEOPS can measure the length of an exoplanet’s radius against the backdrop of its star’s light. With both the mass and size values, it’s possible to calculate the densities of these alien worlds, and that unlocks all kinds of details about their likely characteristics.
Are Super-Earths more often rocky or gaseous? What is the internal structure of planets in this mass and size range? Is it possible that these worlds have oceans, or other necessary conditions to host life as we know it? Those are some of the questions the CHEOPS team hopes to answer.
“We will be able to do this for many small planets, in different orbits around different types of stars,” said Isaak. “With this, we will get significant insight into how planets form and evolve, and if and how the different planet types are related.”
The mission will also observe the behavior of host stars, because that is an important factor in determining the habitability of a planet. Some stars regularly belch out flares of radiation, which could scorch out any life on their planets, for instance.
The orbital distance between planets and stars is also a key detail. ‘“Ultra-hot Jupiter” planets occupy such small orbits that their temperatures may rival those of a star, according to David Ehrenreich, the CHEOPS mission scientist at the University of Geneva.
“Exoplanets receiving a lot of irradiation are thought to react and evolve differently based on their natures,” said Ehrenreich in an email. “A bare, rocky ‘super-Earth’ could be covered by a magma ocean. A ‘hot Jupiter’ like 51 Pegasi b could have clouds made out of tar, so that they would appear extremely dark.”
“With CHEOPS, we are hoping to determine the cloud coverage patterns of all these kinds of objects,” he continued. “For more temperate planets, we will observe the stars and determine their flaring patterns: how frequent do they flare, how intensely?”
These observations will help scientists understand what conditions might be like on worlds such as Proxima b, the closest known exoplanet to Earth. Proxima b is about 1.3 times as massive as Earth, and orbits the red dwarf Proxima Centauri, a star that emits powerful flares. CHEOPS may be able to find out if these planets can retain an atmosphere, or any other indicators of habitability, in the face of such intense blasts of radiation.
The CHEOPS team is also hoping to observe Super-Earths such 55 Cancri e, located about 40 light years from Earth, and the “Mini-Neptune” HD 97658b, which is 70 light years away. Though the mission will mostly study small planets, Isaak said the team also wanted to “compare and contrast” some gas giants, such as KELT-9b, the hottest known exoplanet, and HD 80606b, which is much cooler because of its wider elongated orbit.
“There is an initial target list for CHEOPS, which the science team has been working on for a number of years now,” she said. “It is dynamic, however, and will evolve over the course of the mission as new targets are discovered that need their sizes to be measured or improved upon.”
CHEOPS will now park itself in a geocentric orbit above the terminator, the line where day meets night. With its back to the Sun, the mission will gaze at bright stars that we know host exoplanets, characterize the properties of those worlds, and assess their odds of supporting life.
“The next step is to determine how planets form and evolve, and whether the conditions for life exist,” Isaak said. “Then we can look to see whether there is, in fact, life beyond our solar system.”