In order to study the next earth, NASA may need to cast some shadows

The HabEx team proposed a 4-meter telescope with a coronagraph and a 52-meter diameter star shield. (“It’s great to have belts and suspenders,” said Bertrand Mennesson, NASA JPL Chief Scientist and HabEx Co-Chair.) In addition to providing 10-10 Suppressed, star shadows can image a wide spectral bandwidth, checking the wavelengths of ozone, oxygen, and water vapor in a single image. (LUVOIR’s coronagraph needs to take many images to capture the entire spectrum to obtain clues to these characteristics.) It may also allow imaging of exoplanets at a small distance from the host star, helping to capture “hidden” at closer distances. Planets among planets. Orbit to their sun.

However, star shadows that must fly separately from the telescope pose some challenges that coronagraphs do not. The need for a separate power source will limit the use of the aircraft to approximately 100 observations before it needs to be scrapped or refueled. It also requires two spaceships for delicate, coordinated flights.

Then, of course, there is also the problem of unfolding like origami. Arya and others have been working on this task, using blanket-like Kapton polymer sheets and unfolded carbon fiber frames to make several large test star-shaped tones. (The “blanket” is made of multiple layers of Kapton, so any holes made by the micrometeorite impact in the shade of the tree will not affect its shadow.) This is not easy. The edges of the petals of the star shadows must be very sharp to reflect as little sunlight as possible into the telescope. Any disturbance may affect the imaging of exoplanets. “We are creating an optical precision structure that must automatically fold and unfold, which brings a lot of challenges,” Arya said. “We are gradually solving these problems, but there is still a series of work to be done to prove this technology.”

Perhaps because the task at hand is too difficult, some astrophysicists believe that the coronagraph add The star-shaped shadow may be the perfect punch or two. “I really see the benefits of hybrid systems,” Mennesson said. From one star to another, the coronagraph can image a large number of potentially habitable exoplanets, and then the star shadows can provide a high-resolution appearance, and the bandwidth and throughput of each planet’s light are very large—— It is very suitable for in-depth characterization of its livability. HabEx and the LUVOIR team work closely together, and any future team may learn from their members.

Star shadows may not only be suitable for deep space missions. NASA has provided funds to Mather’s team to study the use of orbiting star shadows to discover exoplanets from Earth. Killer WhaleOr the orbit can be configured with artificial stars. It will be the first hybrid terrestrial space observatory to use laser beacons in space to help ground telescopes focus, thereby eliminating distortion caused by observation through the atmosphere. The next step of the proposal will be to see a 100-meter long “RemoteOcculter” star shadow in low-Earth orbit, which will cast its shadow onto the telescope. “Shading of orbiting stars is much more difficult, but it may be the ultimate exoplanet observation system,” Mather wrote in an email. “Using it, we can see an earth orbiting a nearby star in one minute, and in one hour we can know whether it has water and oxygen like us.”

The decision on which of these projects will continue will take many years. The directions of HabEx and LUVOIR may be released during NASA City Hall at the American Astronomical Society meeting on January 11, and the ORCAS and RemoteOcculter mission proposals are still under study. But the James Webb Space Telescope launched in December will soon return images taken with its low-contrast star shadows. The telescope will be fully operational in mid-2022, and it is expected to become the new leader in exoplanet hunting until a more powerful shadow jet appears.


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