WFIRST Will Use Relativity to Find More Exoplanets!

We, humans, are continuously expanding our research and reach into space. Moving further in the search of more celestial objects, NASA is planning to send  Wide-Field Infrared Survey Telescope (WFIRST), to space in 2025.

The objective of this next-generation telescope will be searching for extra solar planets. It has a 2.4-meter telescope, 18 detectors, a 300-megapixel camera, and an extraordinary survey speed.

With these specifications, WFIRST will be able to scan a hundred times greater area. 100 times greater area than in the space that the Hubble Space Telescope used to.

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Gravitational Microlensing- The Method WFIRST works

WFIRST is not only equipped with high-sensitivity and advanced suite of instruments. But it will also rely on a technique called Gravitational Microlensing to search for and characterize exoplanets.

Gravitational Microlensing is essentially a low-scale version of the gravitational lensing technique.

In this technique, the gravitational force of a massive celestial object between the observer and the target. It is used to focus and magnify the light coming from a distant source.

Transit Photometry- The Old Method

Till now, the exoplanets that have been discovered were done by using the Transit Method also known as Transit Photometry.

In this method, the passage of a planet in the face of a star (i.e. a transit) results in measurable periodic dips in its brightness.

While WFIRST (Wide-Field Infrared Survey Telescope) will monitor for these dips in brightness. It will also be keeping an eye on the periodic surges in radiance generated by microlensing events.

The Microlensing Method

Like Gravitational Lensing (GL),  Einstein’s General Theory of Relativity predicted these events.

In this theory, it is stated that the curvature of spacetime becomes altered. This happens in the presence of the gravitational force produced by a massive object.

Gravitational Lensing relies on galaxies and galaxy clusters. Microlensing relies on chance alignments between two distant stars as they drift through space.

Whenever two stars align closely from our vantage point here on Earth. Then the light from the more distant star curves as it travels past the warped space-time of the nearer star.

If the alignment is especially close. The nearer star will have a “lensing” effect where it magnifies the light coming from the background star.

Similarly, planets that orbit a foreground star have a small lensing effect. This will reveal much about the planet itself.

Because of how they rely on change alignments, microlensing events are a rare occurrence compared to transits.

But with its ability to scan a much wider area of the sky than any previous space telescope, WFIRST will have a much better chance of detecting these events.

As David Bennett, who leads the gravitational microlensing group at NASA’s Goddard Space Flight Center, explained:

Moreover, microlensing is a better method for finding planets that orbit within and beyond their respective star’s habitable zones (HZs).

For instance, microlensing events can allow astronomers to place tight constraints on a planet’s mass and distance from its host star. Whereas the Transit Method is good for gauging a planet’s size and orbital period, but not its mass or distance.

Exoplanet Census

Combined with the many discoveries made by NASA’s Kepler and Transiting Exoplanet Survey Satellite (TESS) missions. WFIRST will complete the first census containing exoplanets with a wide range of masses and orbits. This will allow astronomers to narrow the search for habitable worlds. 

Matthew Penny, an assistant professor at Louisiana State University who led a study to predict WFIRST’s (Wide-Field Infrared Survey Telescope) microlensing survey capabilities said (his quotes are highlighted in blue):

“Trying to interpret the planet’s population today is like making a try with the interpretation of a picture half covered.

To get a full understanding of how planetary systems were formed. We need to find planets of every possible mass at all distances.

There is no other technique that can do this except the WFIRST’s (Wide-Field Infrared Survey Telescope) microlensing survey. Combined with the results from Kepler and TESS, it will reveal far more of the picture.

“WFIRST’s (Wide-Field Infrared Survey Telescope) microlensing survey will not only advance our understanding of planetary systems. Rather it will enable a whole host of other studies of the variability of 200 million stars.

It will also create a clear image of the structure and formation of the inner Milky Way. This will also identify the population of black holes. It will also search other dark, compact objects that are hard or impossible to study in any other way.”

Areas WFIRST (Wide-Field Infrared Survey Telescope) will Cover

Unlike previous surveys, WFIRST (Wide-Field Infrared Survey Telescope) will explore regions of the galaxy that haven’t been systematically searched yet. The unsearched areas include the center of our galaxy, where the majority of stars in the Milky Way reside.

Because of its infrared imaging capabilities, WFIRST will be able to see through the obscuring gas and dust. This prevents the telescopes from studying planets in the crowded central region.

On top of that, WFIRST’s (Wide-Field Infrared Survey Telescope) surveys will also be a lot more ambitious than its predecessors.

Between 2009 and 2018, Kepler searched 100 square degrees of the sky. It tracked 100,000 stars at a distance of about 1000 light-years.

Currently, TESS is scanning the entire sky and tracking 200,000 stars at a distance of about 100 light-years.

It will search an area of the sky measuring just 3 square degrees. But, it will follow 200 million stars at distances of around 10,000 light-years.

James Webb Space Telescope (JWST) and WFIRST (Wide-Field Infrared Survey Telescope) will make a combination. This Combination will take the study of exoplanets into a hyperdrive!

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