The James Webb Space Telescope plans to explore strange and new rocky worlds in unprecedented detail.
They said in a statement Thursday (May 26) that the Telescope Science Consortium has an ambitious agenda to study the geology of these small planets from “50 light-years away.” The work will be a major extension of the new observatory, which is supposed to finish commissioning in a few weeks.
Rocky planets are more difficult to see than the gas giants in current telescope technology, due to the relative brightness of the small planets next to the star, and their relatively small size. But Webb’s powerful mirror and position in deep space should allow him to examine two planets slightly larger than Earth, known as “super-Earths.”
Neither of these worlds are considered habitable as we know them, but their investigation can still serve as a proof-ground for future in-depth studies of planets like ours. The two planets that officials Webb highlighted include the extremely hot, lava-covered planets 55 Cancri e, and LHS 3844 b, which lacks a significant atmosphere.
55 Cancri E orbits its parent star at 1.5 million miles (2.4 million km), about four percent of the relative distance between Mercury and the Sun.
The planet orbits its star only once every 18 hours, and it has a temperature above the blast furnace surface above the melting point of most types of rock. Scientists also hypothesized that the planet gradually locked in front of the star, which means that one side always faces the scorching sun, although observations from NASA’s Spitzer Space Telescope suggest that the hotter region may be offset a bit.
Scientists say the balanced heat may be due to the thick atmosphere that can move heat around the planet, or because it rains lava at night in a process that removes heat from the atmosphere. (Nocturnal lava also refers to a day and night cycle, which may be due to a 3:2 echo, or three cycles per two orbits, that we see on Mercury in our solar system.)
Two teams will test these hypotheses: one led by research scientist Renew who is from NASA’s Jet Propulsion Laboratory will examine the planet’s thermal emissions for signs of the atmosphere, while a second team led by Alexis Brandeker, assistant professor from Stockholm University, will measure the temperature. Emission from the illuminated side of 55 Cancri e.
LHS 3844 b is also a close orbiter, moving around its parent star only once every 11 hours. However, the star is much smaller and cooler than 55 Cancri E. So it’s possible that the planet’s surface is much cooler, and Spitzer’s observations have shown that there probably isn’t much atmosphere on the planet.
A team led by astronomer Laura Kreidberg at the Max Planck Institute for Astronomy hopes to pick up a signal from the surface using spectroscopy, where different wavelengths of light point to different elements. The planet’s daylight thermal emission spectra will be compared to known rocks such as basalt and granite to see if they can infer the surface composition.
In the same statement, Kreidberg said the two surveys “will give us fascinating new perspectives on Earth-like planets in general, helping us learn what early Earths would have been like when it was as hot as these planets are today.”
Webb is now working through last-stage commissioning procedures such as tracking targets in the solar system and transitioning between hotter and colder positions to test the strength of the mirror and instrument alignment. The $10 billion observatory should finish commissioning in June or so and move to its first cycle of observations shortly thereafter.
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