The James Webb Space Telescope plans to explore strange new rocky worlds in unprecedented detail.
The telescope science consortium has an ambitious program to study the geology of these small planets “50 light-years away”, they said in a statement Thursday, May 26. The work will be extensive for the new observatory, which should come into service in a few weeks.
Rocky planets are more difficult to see than gas giants in current telescope technology, due to the relative brightness of the smallest planets next to a star and their relatively small size. But Webb’s powerful mirror and deep-space location should allow him to examine two planets slightly larger than Earth, called “super-Earths.”
None of these worlds are habitable as we know them, but studying them could still be a testing ground for future in-depth studies of planets like ours. The two planets highlighted by Webb officials include 55 Cancri e, which is super hot and covered in lava, and LHS 3844 b, which has no substantial atmosphere.
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55 Cancri e orbits its parent star 1.5 million miles (2.4 million km), or about four percent of the relative distance between Mercury and the sun.
Revolving around its star just once every 18 hours, the planet has blast-furnace surface temperatures above the melting point of most rock types. Scientists have also assumed the planet is tidally locked to the star, meaning one side always faces the scorching sun, although observations from NASA’s Spitzer Space Telescope suggest the hottest area could be slightly offset.
Scientists say the offset heat could be due to a thick atmosphere that can move heat around the planet, or because lava rains down at night in a process that removes heat from the atmosphere. (Nocturnal lava also suggests a day-night cycle, which could be due to a 3:2 resonance, or three rotations for two orbits, that we see on Mercury in our own solar system.)
Two teams will test these hypotheses: one led by research scientist Renyu Hu of NASA’s Jet Propulsion Laboratory will examine the planet’s thermal emission for signs of an atmosphere, while a second team led by Alexis Brandeker, an associate professor at Stockholm University, will measure the heat emittance of the illuminated side of 55 Cancri e.
LHS 3844 b is also a near orbiter, circling its parent star just once every 11 hours. The star, however, is smaller and cooler than that of 55 Cancri e. Thus, the planet’s surface is likely much cooler, and Spitzer’s observations have shown that there is probably no substantial atmosphere present on the planet.
A team led by astronomer Laura Kreidberg of the Max Planck Institute for Astronomy hopes to pick up a signal from the surface using spectroscopy, in which different wavelengths of light suggest different elements. Thermal emission spectra from the daylight side of the planet will be compared to known rocks like basalt and granite to see if they can infer a surface composition.
The two surveys “will give us fantastic new insights into Earth-like planets in general, helping us understand what early Earth was like when it was warm like these planets are today,” Kreidberg said in the same communicated.
Webb is currently working on late-stage commissioning procedures, such as tracking targets in the solar system and moving between warmer and cooler attitudes to test his mirror strength and instrument alignment. The $10 billion observatory is expected to complete commissioning around June and move into its Cycle 1 of observations shortly thereafter.