NASA’s flagship telescope has found the first evidence of an atmosphere around a rocky planet outside our Solar System. It’s not the kind of world we can live on, but it could teach us more about how rocky planets form and retain their atmospheres. The hellish super-Earth called 55 Cancri e, is 41 light years away and circles its red dwarf star so closely that it’s tidally locked, with permanent day and night sides.
55 Cancri e is too hot to be habitable
The planet 55 Cancri e, located 41 light-years away in the constellation Cancer, is covered by dark molten rock and a thin veil of vaporized rock. Its atmosphere may be enriched with carbon dioxide and carbon monoxide, according to astronomers using NASA’s James Webb Space Telescope. The scientists spotted the gases in data from the telescope’s NIRCam and MIRI instruments. The resulting spectrum showed a “dip” in the brightness of a certain part of the star’s emission line, suggesting the presence of an atmosphere.
The team thinks the gases blanketing the planet are bubbling out from its interior, replenished by rocks melting and releasing gas as they churn in a magma ocean beneath their surfaces. This would create a secondary atmosphere that could be more stable than the primary one, which would otherwise be stripped away by stellar radiation.
However, the researchers also found evidence of a thick surface layer that might be rich in water and nitrogen. Those molecules can be swept away by the intense heat from the planet’s host star, but they might survive if the temperature isn’t too high.
Astronomers first detected 55 Cancri e in 2004 after studying the star it orbits. Its gravity causes the star to wobble, and this change is measurable by telescopes on Earth. The team studied the spectrum of the star, and discovered subtle tugs that indicated the presence of a planet with three times the mass of Earth. They modeled the planet’s composition and determined it is probably made of carbon (mainly diamonds and graphite) with some iron, silicon carbide, and possible silicates.
While the planet’s density is similar to that of Earth, its intense heat makes it unlikely that life can survive there. But the fact that a rocky planet with an atmosphere has been detected suggests that such worlds may be much more common than once thought.
The discovery of 55 Cancri e supports a model of planet formation that suggests rocky planets tend to form close to their stars, but do not preferentially form around stars that contain metallic elements such as iron and silicon. This finding, based on a new method for measuring the atmospheric composition of exoplanets, is published in The Astrophysical Journal. The method was developed by Dr. Andrew Hu of JPL and adapted by graduate student Isabel Angelo, who worked on the study as part of her internship at the observatory.
It has a thick atmosphere
Before this discovery, scientists had largely concluded that 55 Cancri e had no atmosphere. However, the team found evidence that it does have one, and that its thickness is a mystery. They found this by studying the planet’s polarity and day-night temperature contrast using data from NASA’s Spitzer Space Telescope. Their results suggest that the planet’s thick atmosphere carries heat around, which can explain its extreme temperatures.
The discovery is a breakthrough in the search for rocky exoplanets with an atmosphere outside our Solar System. It is the strongest evidence yet that a planet can have a thick, gaseous atmosphere even when it is blasted by scorching temperatures and radiation from its host star. It also suggests that the presence of a second atmosphere on an exoplanet is not uncommon.
This rocky planet super-Earth, 41 light years away from Earth, circles its host star Copernicus so closely that it has permanent day and night sides. It is eight times more massive and twice as wide as our own planet, and has a molten lava ocean with surface temperatures of up to 3,600 degrees Fahrenheit. It has been compared to the Star Wars lava world of Mustafar, where Darth Vader established his fortress in Revenge of the Sith.
Astronomers had previously ruled out an atmosphere on 55 Cancri e because of its extreme temperature contrast between its hot day side and cold night side. However, the new study finds that this temperature difference is due to a thermal imbalance in the planet’s atmosphere, not because its atmosphere is being stripped off by the harsh radiation of its star.
To determine this, the astronomers used data from Spitzer’s Infrared Array Camera to watch 55 Cancri e over its entire orbit. They compared the changes in brightness that Spitzer observed to a model of how energy flows on and off the planet, and they realized that an atmosphere with volatile molecules would best explain the temperature differences they saw.
The observations are in line with the theory that the chemical composition of a planet is related to its host star, because it forms from material left over from the formation of the stars. However, this is not a one-to-one correlation, and many other processes are at play during planet-forming. As more data is gathered from extrasolar systems, a clearer picture of how rocky exoplanets form will emerge.
It’s surrounded by a magma ocean
Imagine being a small rock, surrounded on all sides by a sea of boiling lava and under an enormous star that looms over you. That’s essentially the scenario of 55 Cancri e, the first rocky planet astronomers have ever seen with an atmosphere. The discovery, announced last week by a team led by Renyu Hu of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, is one of the biggest advances so far in astrobiologists’ quest to find planets that can support life as we know it.
Scientists made the surprising find by using a technique called “secondary eclipse spectroscopy.” This involves subtracting the brightness of the star from that of the planet when the latter is passing in front of its host star, which blocks some of the light as it circles around the planet. Using this approach, scientists can identify the presence of gases that make up the planet’s atmosphere. The resulting spectrum was analyzed by the JPL team, along with scientists at the University of Bern in Switzerland and the Institut de Physique du Globe in Toulouse, France.
The rocky planet spectra show that the planet is surrounded by an atmosphere rich in carbon dioxide or carbon monoxide. These gases absorb the wavelengths of infrared light that are emitted by the planet, as shown by the dip in the spectra at 4 to 5 microns. Observations with the Spitzer Space Telescope and its NIRCam GRISM spectrometer and MIRI low-resolution spectrometer reveal that the planet’s dayside temperature is lower than it would be without an atmosphere, which distributes heat from the planet to its night side.
The researchers also compared their findings with a model of the planet’s atmosphere, which took into account how well its volatile molecules hold onto heat from its host star. They found that the model predicted that a planet with a substantial atmosphere would have an overall warmer temperature than they observed. This is a strong indication that the planet has a vaporous shroud of carbon dioxide and other gases, not just a thin layer of melted rock.
It’s likely to have a second atmosphere
Scientists have discovered a thick atmosphere around a hot rocky exoplanet 41 light years from Earth. The discovery is the strongest evidence to date for a planetary atmosphere outside our solar system. The discovery was made with the help of the James Webb Space Telescope. Scientists analyzed data from two eclipses of the planet as it passed behind its host star. By separating the light from the star and the planet, they were able to determine the makeup of the atmosphere. They found that the planet likely has a second atmosphere consisting of carbon, nitrogen and water. This atmosphere could help to hold the temperature of the planet stable. The results of the study were published in Nature.
The exoplanet is twice the size of Earth and orbits a red dwarf, the smallest type of ordinary star. It is the only rocky planet known to be tidally locked, meaning that it keeps the same face toward its star at all times. The star is very close to the planet, and it takes six days for light to travel from one to the other.
Previous studies of the planet had varying results. Some suggested that the planet has an atmosphere, while others argued it was a bare lava world with no significant atmosphere at all. The new findings suggest that the planet has a substantial atmosphere, and the most probable composition is one similar to that of Earth. This atmosphere may be formed from gases dissolved in the vast lava ocean that covers 55 Cancri e.
To make their conclusion, the scientists compared Spitzer observations of the planet before and after it passed behind its star. Spitzer acted like night-vision goggles to measure changes in the brightness of the planet, which is an indication of how much heat it was emitting. They then matched the changes in brightness to energy flow models. They realized that an atmosphere, possibly with ingredients such as nitrogen and water, would best explain the temperatures.
The findings are important because they offer clues to how rocky planets in inhospitable environments can maintain their atmospheres. They also shed light on how life might form on other rocky planets, such as Earth and Venus.