US space agency scientists Nasa are getting ready to use the powerful James Webb telescope to explore a planet relatively close to Earth and with similar characteristics. There is only one big difference: it is possible that the rains there are made of lava.
Named 55 Cancri e, this exoplanet (as planets outside the Solar System are classified) orbits a star that is just 40 light-years away, so close that it can be seen with the naked eye in the sky, in the constellation Cancer. .
A tweet commenting on his characteristics went viral in social networksbut the discovery of 55 Cancri e is not recent: astrophysicists have known of its existence since 2004. The novelty is that NASA will use the James Webb telescope to study it more closely.
They found an Earth-like exoplanet! 🥰🥰🥰
Pro: looks like Earth
Against: ᶜʰᵒᵛᵉ ˡᵃᵛᵃ ᵈᵉ ⁿᵒᶦᵗᵉ https://t.co/2ockyzJPyi— Felipe Castilho (@felcastilho) June 4, 2022
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And not only him: on the 26th of May, NASA announced who will use James Webb to also study LHS 3844 b. The two exoplanets are called “super Earths” by scientists because they are rocky and close in size to our planet, but with extreme geological and climatic conditions.
Super Earth, super hot
55 Cancri e is just 2.4 million kilometers away from its star, which is also similar to our Sun. This means that, over there, a year ends in 18 hours.
Because it is so close to its star, the heat is so extreme that, even though this is a rocky planet, any mineral on the surface would exceed its melting point. Therefore, scientists believe that it is covered by oceans of lava.
It was believed that, because it was so close to its star, 55 Cancri, it did not rotate (turn around its own axis), but always had one side facing its “Sun” and the other in eternal darkness. .
But observations made with NASA’s Spitzer Space Telescope have brought up more questions than answers about this super Earth. Astronomers have noted that the hottest point on 55 Cancri’s surface is not the point that receives most heat from the Sun directly. Furthermore, the temperature on the supposed “dayside” of the exoplanet varies over time.
One explanation for this is that the planet has a dynamic atmosphere that moves heat. “55 Cancri e may have a thick atmosphere dominated by oxygen or nitrogen,” says Renyu Hu of NASA’s Jet Propulsion Laboratory, who leads a team that will use the James Webb’s infrared camera (NIRCam) to study the spectrum of thermal emission from the dayside of the planet. “If it has an atmosphere, Webb has the sensitivity and wavelength range to detect it and determine what it’s made of.”
Illustration of the James Webb telescope armed and ready for space observation
Image: Disclosure / NASA
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The other possible explanation is the one that stirred tweets: the 55 Cancri e may not always be locked in the same position, but rather be rotating around its axis with slow cycles of day and night. This is what happens to Mercury, the planet closest to the Sun in our Solar System, which completes three rotations every two orbits around our star.
In this scenario, the surface would heat up, melt and even vaporize during the day. At night, the steam cools and condenses to form a lava shower. The drops would revert to solid form as they hit the ground.
“This could explain why the hottest part of the planet is displaced,” explained Alexis Brandeker, a researcher at Stockholm University who leads another team studying the planet. “Just like on Earth, it would take time for the surface to warm up. The hottest time of day would be in the afternoon, not noon.”
Brandeker’s team plans to test this hypothesis by using James Webb’s NIRCam to measure the temperature of the bright side of the exoplanet during four different orbits. If it is like Mercury, each hemisphere will be observed twice. Thus, scientists will be able to detect the temperature differences between the hemispheres.
Super Earth, no lava
—Artist’s rendering of LHS 3844 b, rocky airless planet that James Webb will investigate
Imagem: NASA/JPL-Caltech/R. Hurt (IPAC)
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Less impressive than the planet where it rains lava is the other super Earth that NASA will investigate. LHS 3844 b is cooler, so its rocky surface must be solid. The difference is that there is probably no air there.
Previous observations have shown that this exoplanet, discovered in 2019 and located 49 light-years from Earth, does not appear to have an atmosphere — or at least not one dense enough to be detected by our telescopes.
For NASA, this is an advantage: it allows a clearer study of its rocky surface. Laura Kreidberg of the Max Planck Institute for Astronomy in Germany will use James Webb’s mid-infrared instrument (MIRI) to analyze thermal emission spectrometry from the dayside of LHS 3844 b.
She then plans to compare the results with the spectrometry of known rocks such as basalt and granite to find out what kind of rock is on the surface of LHS 3844 b. If the planet is volcanically active, the experiment could also reveal the presence of traces of volcanic gases there.
Why does it matter?
Of the more than 5,000 exoplanets confirmed in the galaxy, with the most diverse characteristics and compositions, why did NASA decide to study these two so soon?
Rocky planets like LHS 3844 b and 55 Cancri e are harder to find than gas giants, which we know a lot more about. Also, “super Earths” like these can give us more clues about the formation of our own planet.
“They will give us fantastic new perspectives on Earth-like planets in general, helping us learn what the early Earth might have looked like when it was hot as these planets are today,” Kreidberg told NASA.
The study is also a way to test the James Webb telescope, which only recently completed its alignment and was ready to photograph the universe.
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