With beautifully aligned mirror segments and science instruments being calibrated, NASA’s James Webb Space Telescope is just a few weeks away from full service. As soon as the first observations are revealed this summer, Webb’s in-depth science will begin.
Among the investigations planned for the first year are studies of two hot alien planets classified as “super-Earths” for their size and rocky composition: 55 Cancri e covered with lava. lava and LHS 3844 have no air. B. Researchers will train Webb .’s high accuracy spectrograph on these planets to understand the geological diversity of planets in the galaxy and the evolution of rocky planets like Earth.
Super hot Super Earth 55 Cancri e
55 Cancri e orbits less than 1.5 million miles from its Sun-like star (1/5 the distance between Mercury and the Sun), completing one revolution in less than 18 hours. With a surface temperature much higher than the melting point of typical rock-forming minerals, the planet’s diurnal surface is thought to be covered by oceans of lava.
Planets orbiting this star close to their star are said to be neatly locked, with one side always facing the star. Therefore, the hottest point on the planet must be the point most directly opposite the star, and the amount of heat emitted by the day won’t change much over time.
But this does not seem to be the case. The 55 Cancri e observations from NASA’s Spitzer Space Telescope show that the hottest region is offset from the part most directly opposite the star, while the total amount of heat detected from the diurnal side remains unchanged.
Imagine if the Earth was a lot closer to the Sun. So close that an entire year lasts only a few hours. So close that gravity locked one hemisphere in perpetual harsh daylight and the other in endless darkness. So close that the oceans boiled, rocks began to melt, and the clouds formed lava rain.
While nothing of this kind exists in our solar system, planets like this – rocky, roughly the size of Earth, extremely hot and close to their stars – are not rare in the Milky Way galaxy.
What are the surfaces and atmospheres of these planets really like? NASA’s James Webb Space Telescope is about to provide some answers.
55 Cancri e Is There a Thick Atmosphere?
One explanation for these observations is that the planet has a dynamic atmosphere that moves heat around. “55 Cancri e may have a dense atmosphere dominated by oxygen or nitrogen,” said Renyu Hu of NASA’s Jet Propulsion Laboratory in Southern California, who is leading a team that will use Webb’s Near Infrared Camera (NIRCam) and Mid-Range Infrared Instruments (MIRI) to grasp thermal emission spectroscopy in the day of the planet. “If it has atmosphere, [Webb] has the sensitivity and wavelength range to detect it and determine what it’s made of,” added Hu.
Or is Lava rain in the evening on 55 Cancri e?
Yet another intriguing possibility is that the 55 Cancri e is not neatly locked. Instead, it could be like Mercury, rotating three times for each of its two orbits (known as a 3:2 resonance). As a result, the planet will have a day-night cycle.
“That could explain why the hottest part of the planet is displaced,” explains Alexis Brandeker, a researcher from Stockholm University who leads another planetary team. “Just like on Earth, it will take time for the surface to warm up. The hottest time of the day will be in the afternoon, not right at noon. “
Brandeker’s group plans to test this hypothesis by using NIRCam to measure the heat radiated from the illuminating face of 55 Cancri e in four different orbits. If the planet had a 3:2 resonance, they would observe each hemisphere twice and be able to detect any differences between the hemispheres.
In this case, the surface would heat up, melt, and even evaporate during the day, forming a very thin atmosphere that Webb could detect. In the evening, the steam will cool and condense to form lava droplets that flow back to the surface, returning to solid as night falls.
Credit: ILLUSTRATION: NASA, ESA, CSA, Dani Player (STScI)
Slightly cooler than Super Earth LHS 3844 b
While 55 Cancri e will provide insight into the strange geology of a world covered in lava, LHS 3844 b offers a unique opportunity to analyze solid rock on exoplanet surfaces.
Like 55 Cancri e, LHS 3844 b orbits extremely close to its star, completing one revolution in 11 hours. However, because its star is relatively small and cool, the planet is not hot enough for the surface to melt. In addition, Spitzer’s observations indicate that the planet is unlikely to have a significant atmosphere.
Surface of LHS 3844 b What is it made of?
Although we will not be able to directly image the surface of LHS 3844 b with Webb, the lack of an occulted atmosphere makes it possible to study the surface by spectroscopy.
“It turns out that different rocks have different spectra,” explains Laura Kreidberg at the Max Planck Institute for Astronomy. “With the naked eye you can see that granite is lighter in color than basalt. There is a similar difference in the infrared light that the stone emits. “
Kreidberg’s team will use MIRI to capture the thermal emission spectrum of the LHS 3844 b date face, and then compare it with the spectra of known rocks, such as basalt and granite, to determine its composition. . If the planet is volcanically active, the spectrum may also reveal the presence of small amounts of volcanic gas.
The importance of these observations goes beyond just two of the more than 5,000 confirmed exoplanets in the galaxy. “They will give us amazing new perspectives on Earth-like planets, helping us understand what the early Earth might have been like when it was as hot as these planets are today,” Kreidberg said. “.
These observations of 55 Cancri e and LHS 3844 b will be conducted as part of Cycle 1 of Webb General observer program. The Joint Observer programs were selected competitively using a dual anonymous rating system, the same system used to allocate time on Hubble.
The James Webb Space Telescope is the world’s leading space science observatory. Webb will solve the mysteries of our solar system, look beyond distant worlds around other stars, and probe the mysterious structures and origins of the universe and the location of we are in it. Webb is an international program led by NASA with ESA (European Space Agency) and Canadian Space Agency partners.
Banner image: Illustration showing what exoplanet 55 Cancri e might look like, based on current understanding of the planet. 55 Cancri e is a rocky planet nearly twice the diameter of Earth orbiting just 0.015 astronomical units from its Sun-like star. Due to its narrow orbit, the planet is extremely hot, with daytime temperatures reaching 4,400 degrees Fahrenheit (about 2,400 degrees Celsius). Illustrator: NASA, ESA, CSA, Dani Player (STScI)
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