The telescope will study of them is the lava-covered ’55 Cancri e’ and the other is the airless ‘LHS 3844 b’ (Picture: Nasa)

Nasa’s James Webb Space Telescope is a million miles from Earth and has two new targets in sight.

In its first year of operation, Nasa’s billion dollar telescope will study two hot ‘super-Earths’ for their size and rocky composition.

One of them is the lava-covered ’55 Cancri e’ and the other is the airless ‘LHS 3844 b’.

Researchers will train Webb’s high-precision instruments on these planets to try and understand the geologic diversity of planets across the galaxy, and the evolution of rocky planets like Earth.

55 Cancri e is less than 1.5 million miles from its Sun-like star. That’s one twenty-fifth of the distance between Mercury and the Sun so an entire year lasts only a few hours.

Planets that orbit this close to their star are assumed to be tidally locked, with one side locked in permanent searing daylight and the other in endless darkness.

With surface temperatures far above the melting point of typical rock-forming minerals, Nasa thinks its possible that the planet’s ‘clouds rain lava’. 

Is it possible for a rocky planet to be so hot that the surface is molten and the clouds rain lava? 🔥 ☂️ #NASAWebb will find out:

📷: Artist illustration, credit NASA, ESA, CSA, Dani Player (STScI)

— NASA Webb Telescope (@NASAWebb) May 26, 2022

Rocky, roughly Earth-sized planets that are extremely hot and close to their stars are not uncommon in the Milky Way galaxy. The James Webb Space Telescope is on a mission to study these planets.

The hottest spot on 55 Cancri e should be the one that faces the star most directly but observations from Nasa’s Spitzer Space Telescope suggest that’s not the case.

’55 Cancri e could have a thick atmosphere dominated by oxygen or nitrogen,’ explained Renyu Hu of NASA’s Jet Propulsion Laboratory in Southern California, who leads a team that will use Webb’s cameras to capture the thermal emission spectrum of the day side of the planet.

‘If it has an atmosphere, [Webb] has the sensitivity and wavelength range to detect it and determine what it is made of,’ Hu added.

It’s also possible that 55 Cancri e is not tidally locked but like Mercury, rotates three times for every two orbits, resulting in a day-night cycle.

‘That could explain why the hottest part of the planet is shifted,’ explained Alexis Brandeker, a researcher from Stockholm University who leads another team studying the planet.

Brandeker’s team plans to test this hypothesis using NIRCam to measure the heat emitted from the lit side of 55 Cancri e during four different orbits.

The other planet, LHS 3844 b, also 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 be molten.

While Webb won’t be able to image the surface of LHS 3844 b directly, the lack of an obscuring atmosphere makes it possible to study the surface with spectroscopy.

‘It turns out that different types of rock have different spectra,’ explained Laura Kreidberg at the Max Planck Institute for Astronomy.

‘You can see with your eyes that granite is lighter in color than basalt. There are similar differences in the infrared light that rocks give off,’

Kreidberg’s team will study the thermal emission spectrum of the day side of LHS 3844 b, and compare it to spectra of known rocks, like basalt and granite, to determine its composition. If the planet is volcanically active, the spectrum could also reveal the presence of trace amounts of volcanic gases.

The findings are expected to shed new perspectives on Earth-like planets, helping us learn what the early Earth might have been like when it was hot like these planets are today.

Soon after the first observations are revealed this summer, Webb’s in-depth science is expected to begin.

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