Looking to the Future of Exoplanet Science - Eos
Upcoming missions seeking to unravel the secrets of exoplanets abound. An informal survey of astronomers revealed which of those projects they most eagerly await.
From article, (The European Space Agency’s (ESA) upcoming planet hunter, called Planetary Transits and Oscillations of Stars (PLATO), came in third place in our survey. Although this 6-year mission is not scheduled to launch until 2024, its goal of monitoring more than 1 million stars for signals of planetary transits has caught the attention of the scientific community.
Discovering planets through the tiny amount of light they block as they pass in front of their stars has been commonplace since the launch and success of NASA’s Kepler Space Telescope in 2009. Intended to build upon Kepler’s success, PLATO includes among its scientific goals detecting thousands of exoplanets (including rocky worlds), understanding the makeup and dynamics of planetary systems, and learning enough about the planets to determine their habitability.
The mission lifetime of PLATO is also a step up from that of Kepler. Because Kepler’s primary mission ended after 4 years, it was able to detect only a handful of rocky planets in their habitable zones. PLATO scientists calculate that a 6-year mission will significantly increase the haul of Earth-like planets in the Goldilocks zone and also potentially unveil smaller planets, exomoons, exoplanets with rings, and possibly exo-asteroids.
Coming in second place is the exoplanet telescope that is also the next to launch: NASA’s Transiting Exoplanet Survey Satellite (TESS). NASA selected TESS in 2013 to be funded under the agency’s Explorers Program, a 60-year-old program that develops small- and medium-sized missions costing less than $180 million (in today’s dollars). Now, just 5 years later, the telescope is completely built and is undergoing final testing before launch. The satellite is currently scheduled to lift off from Cape Canaveral Air Force Station in Florida this year, sometime from early March to late June.
Like PLATO, TESS carries on the legacy of the Kepler Space Telescope by monitoring hundreds of thousands of stars for the signatures of planetary transits. But what makes TESS unique is that the stars it will be monitoring are scattered across the sky. In fact, TESS will conduct the first space-based, all-sky transit survey, which it will carry out in a mere 2 years.
The TESS team plans to spend the mission’s first year mapping the Southern Hemisphere sky and the second year mapping the northern sky. TESS will monitor the brightest 200,000 stars in small patches of the sky for 27 days apiece before moving on to another area. This technique is not only expected to discover thousands of transiting exoplanet candidates but to begin to reveal areas in the Milky Way galaxy where exoplanets are most likely to form. TESS’s initial list of targets contains 750 billion objects.
TESS’s targets are 30–100 times brighter than Kepler stars, so they will be easier to follow up with ground-based telescopes, according to TESS scientists at the meeting. Because TESS will measure only the planets’ sizes, follow-up observations from the ground will be needed to reveal their masses, densities, and atmosphere properties. The TESS team also hopes to provide a wealth of future targets for the James Webb Space Telescope to focus on during its first few years of operation.
The James Webb Space Telescope (JWST) won the most votes in our poll. Considered by many to be the successor to the HST, this highly anticipated exoplanet mission has been in the works since 1996. It is currently scheduled to launch from French Guiana in spring 2019.
Despite how excited exoplanet scientists are about the telescope, JWST is not dedicated solely to the search for and characterization of exoplanets. After the telescope opens its “eyes,” it will observe planets, stars, galaxies, and the universe in equal proportion. Moreover, the planetarycomponent of JWST’s mission is not even exclusive to exoplanets, as it will also explore planets and other objects in our solar system and study the potential for life close to home.
JWST will feature four instruments that together will observe infrared light for imaging and spectroscopy. Infrared light is ideal for studying exoplanets, particularly Earth-like planets, because the contrast between stars and planets is highest at those wavelengths. By viewing exoplanets across a broad swath of the infrared spectrum, JWST will measure the chemical contents of the atmospheres of Earth-sized planets around Sun-like stars and begin to tell us what conditions may be like on the surfaces of those planets.
The scientific advisory board of JWST has already selectedwhich areas of science the telescope will pursue during its first 6 months of operation, and exoplanet projects received 2 of the 13 highly coveted spots. One project will observe planetary transits with all four instruments, and the other project will directly image and obtain spectra of young exoplanets and planet-forming disks.
Currently, there are 17 funded or planned exoplanet missions in the works for future launch to space or at major ground-based observatories around the world. A few notable missions to add to the four detailed here are ESA’s Characterising Exoplanets Satellite (CHEOPS), scheduled to launch by the end of this year; NASA’s Habitable Exoplanet Imaging Mission (HabEx), a proposed flagship mission dedicated solely to exoplanets; and the EPICS instrument, an exoplanet imager and spectrograph planned for the Extremely Large Telescope (ELT), which is now under construction.
What’s more, dozens of smaller exoplanet-hunting instruments will be added to preexisting telescopes, such as the Habitable Zone Planet Finder (HPF) at the ground-based Hobby-Eberly Telescope in Texas. Astronomers are also planning creative twists on data from other telescopes, like Gaia, that were not made to search for exoplanets to enable them to do so.)
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