Inferred: 160 Billion Alien Worlds Out There!

No, we haven’t found life outside Earth as yet, but we have definitely improved our prospects. A growing number of telescopes has fuelled a burgeoning number of exoplanet discoveries, led primarily by the Kepler Space Telescope, which has detected 2330 long-period planets (planets having a period of more than a few days) till date. It has performed really well as compared to ground based telescopes, but there are plans to either upgrade it or replace it with a better model. According to Kepler, the count in the Milky Way now turns out to be 1.6 planets per star, and there being 100 billion stars, the count is 160 billion planets just within our galaxy!

An exoplanet (artist's impression). There are 160 billion of them, at least!

Kepler Space Telescope

Kepler works using a very simple principle. It monitors the light coming from certain stars over a period of a number of months. The data is then sent to ground based command centers, which analyse the data and look for the presence of any periodic dimming and brightening events. Any such periodic changes in the brightness of a star suggests that there is another body circling it, which periodically eclipses the star just a bit during its transit. This method also helps the telescope pick up periodic wobbles of the parent star. Observing the wiggles this causes in the spectral lines of the star, scientists can infer not only the presence of an alien planet, but also pinpoint its mass and orbital period.

Earth-like objects

Very recent observations by Kepler show a marked rise in the number of Earth-like rocky planets being discovered. These might not be of the same size of the Earth, or they might not orbit their stars at the optimal ‘Goldilocks’ distance, but they are not gas giants. This is important, since gas giants are not presumed to hold liquid water or harbor any kind of life form.

The study leading to this estimate of the number of exoplanets was led by Arnaud Cassan from the Paris Institute of Astrophysics and their work appeared in the January 12th issue of Nature.

Contact  may not have been such a far-fetched movie after all!

Published by

Debjyoti Bardhan

Is a science geek, currently pursuing some sort of a degree (called a PhD) in Physics at TIFR, Mumbai. An enthusiastic but useless amateur photographer, his most favourite activity is simply lazing around. He is interested in all things interesting and scientific.