April 20, 2021

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Could NASA’s Nancy Grace Roman Telescope find 100,000 planets?

6 min read

Due for launch in the mid-2020s, the Nancy Grace Roman Telescope is destined to become one of the great planet-hunting telescopes. Although the main mirror at the heart of the Roman Telescope is no larger than the one in the Hubble Space Telescope, the Roman mirror is just 25 percent as massive as its predecessor. With a wider field of view greater than Hubble, this next-generation telescope, formerly known as WFIRST, may discover 100,000 worlds orbiting other stars.

The Roman Telescope will study the sky in infrared wavelengths utilizing two methods to detect exoplanets. The first of these techniques, the transit method, measures dips of light seen from a star as a planet passes “in front of” its stellar parent as seen from Earth. The second method, gravitational microlensing, notes slight increases in light caused by the presence of an exoplanet.

Keep squinting, you’ll see it…

Hit the play button above for a look at how exoplanets are found using the transit method, in this video provided by NASA.

Most exoplanets discovered so far were found using the transit method. Regular, periodic dimming of a star is the easiest way to find planets, but it only works for systems where an exoplanet passes between the star and Earth.

Astronomers currently know of nearly 4,400 planets orbiting other stars. Of these, about 2,800 were discovered using the transit method by the Kepler spacecraft (which ended its mission in 2018).

The same technique is currently being utilized by the Transiting Exoplanet Survey Satellite (TESS).

Hit the play button above for a look at how gravitational microlensing can reveal the presence of distant exoplanets, in this video by NASA.

Gravitational microlensing, a brightening of light from a star, results when light from the star bends due to the gravitational forces of an exoplanet, in much the same way as light bends while passing through a convex lens in a telescope. This phenomenon was first predicted by Albert Einstein in his General Theory of Relativity.

“Microlensing events are rare and occur quickly, so you need to look at a lot of stars repeatedly and precisely measure brightness changes to detect them. Those are exactly the same things you need to do to find transiting planets, so by creating a robust microlensing survey, Roman will produce a nice transit survey as well,” said astrophysicist Benjamin Montet of the University of New South Wales in Sydney.

Credit: NASA