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This is an artist impression of the extrasolar planet of the size of Jupiter, HD 189733b, overshadowed by its parent star. Credits: ESA, NASA, Mr. Kornmesser (ESA / Hubble) and STScI
In April 2018, NASA launched the Exoplanets of Transit Survey (TESS) satellite. Its primary goal is to locate Earth-sized planets and larger "super-Earths" orbiting nearby stars for further study. One of the most powerful tools that will examine the atmospheres of some planets discovered by TESS will be NASA's James Webb Space Telescope. As observing small exoplanets with thin atmospheres like the Earth will be a challenge for Webb, astronomers will initially target gaseous exoplanets.
Some of Webb's early observations of giant gaseous exoplanets will be performed by the Discretionary Early Release Science program. The exoplanets project team in transit at the center of Webb's scientific operations plans to conduct three types of observations that will provide new scientific knowledge and a better understanding of the performance of Webb's scientific instruments.
"We have two main objectives. The first is to transfer Webb exoplanet datasets to the astronomical community as soon as possible. The second is to do great science so that astronomers and the public can see how powerful this observatory is, "said Jacob Bean, of the University of Chicago, co-principal investigator on the project. 39, exoplanets in transit
. is to provide critical knowledge and ideas to the astronomical community that will help catalyze the exoplanet research and make the most of Webb in the limited time we have, "said Natalie Batalha of NASA's Ames Research Center, principal investigator project.] Transit – An Atmospheric Spectrum
When a planet crosses past or transits its host star, starlight is filtered through the atmosphere of the The molecules in the atmosphere absorb certain wavelengths or colors of light.By dividing the star's light into a rainbow spectrum, astronomers can detect these sections Missing light and determine which molecules are in the atmosphere of the planet.
For these observations, the project team selected WASP-79b. 780 light years from Earth. L & # 39; team it expects to detect and measure the abundance of water, carbon monoxide and carbon dioxide in WASP-79b. Webb could also detect new molecules not yet seen in exoplanet atmospheres
Phase Curve – A Meteorological Map
Planets whose orbits are very close to their stars tend to hang. One side of the planet is permanently facing the star while the other side is facing, just as one side of the moon is still facing the earth. When the planet is in front of the star, we see its back cooler. But as it orbits around the star, more and more of the heat of the day appears. By observing an entire orbit, astronomers can observe these variations (called phase curves) and use the data to map the temperature, clouds, and chemistry of the planet as a function of longitude.
The team will observe a phase curve of the "hot Jupiter" known as WASP-43b, which orbits around its star in less 20 hours. By looking at different wavelengths of light, they can sample the atmosphere at different depths and get a more complete picture of its structure. "We have already seen dramatic and unexpected variations for this planet with Hubble and Spitzer, and with Webb we will reveal these variations in much more detail to understand the physical processes that are responsible," said Bean.
Eclipse – The Glare of a Planet
The biggest challenge in observing an exoplanet is that the star's light is much brighter, inundating the weak light of the planet. To work around this problem, one method is to observe a planet in transit when it disappears behind the star, and not when it passes through the star. By comparing the two measures, one taken when the star and the planet are visible, and the other when only the star is in view, astronomers can calculate the amount of light coming from of the planet alone.
This technique works best planets that shine brightly in infrared light. The team plans to study WASP-18b, a planet that is fired at a temperature of nearly 4800 degrees Fahrenheit (2,900 K). Among other questions, they hope to determine if the planet's stratosphere exists because of the presence of titanium oxide, vanadium oxide or another molecule.
Living Planets
Ultimately, astronomers want to use Webb to study potentially habitable planets. In particular, Webb will target planets in orbit around red dwarf stars, as these stars are smaller and lighter, making it easier to detect the signal of a planet in orbit. Red dwarfs are also the most common stars in our galaxy.
"TESS is expected to locate more than a dozen orbiting planets in habitable red dwarf areas, some of which may actually be habitable.We want to know if these planets have atmospheres and Webb will be the only one to tell us, "said Kevin Stevenson of the Space Telescope Science Institute, a co-principal investigator on the project. "The results will go a long way towards answering the question of whether life-friendly conditions are common in our galaxy."
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