Transiting exoplanets cause their ultra-cool host – TRAPPIST-1 – to change its brightness!

Image courtesy: NASA Ames/G. Barentsen

New Delhi: On February 22, NASA announced its big discovery of seven Earth-like planets around TRAPPIST-1, a star residing in a far-away galaxy, with all of them possessing the characteristics of liquid water, which is the key to life.

TRAPPIST-1, the 'ultra-cool' dwarf star as it is called, boasts of some incredible characteristics itself, which NASA's Kepler space telescope has been busy in decoding.

NASA recently released a fully pixelated animation which shows how each pixel has caught the light collected from TRAPPIST-1. Not directly visible in the movie are the seven Earth-size planets that orbit the star.

Kepler has managed to detect a change in brightness when a planet passes in front of a star from the vantage point of the telescope.

According to the American space agency, transiting planets block a tiny fraction of starlight that produces miniscule dips in the brightness of their host star. An Earth-size planet passing in front of a small ultra-cool dwarf star like TRAPPIST-1 creates less than a one percent dip in brightness, and is not visible with the naked eye.

Astronomers use sophisticated algorithms to search the data for these dips in brightness, and in particular, to correct for the spacecraft’s small movements in space—this is the 'flickering' of the pixels seen in the movie.