Four days ago, NASA made an amazing announcement – the biggest discovery of exoplanets to date. According to their figures, which added 1,284 planets to the total world count, the confirmed exoplanets are now more than 3,000 (3,264, to be precise) among which 225 terrestrial. With more than 2,000 still “candidate”, meaning whose existence has still to be confirmed.
“Analysis was performed on the Kepler space telescope’s July 2015 planet candidate catalogue, which identified 4,302 potential planets. For 1,284 of the candidates, the probability of being a planet is greater than 99 percent – the minimum required to earn the status of “planet.” An additional 1,327 candidates are more likely than not to be actual planets, but they do not meet the 99 percent threshold and will require additional study. The remaining 707 are more likely to be some other astrophysical phenomena. This analysis also validated 984 candidates previously verified by other techniques.” (NASA Press Release, May 10, 2016)
Impossible not to be excited, especially when thinking about the likelihood of spotting that famous Earth 2.0 astronomers are searching for everywhere. So far, since Kepler was launched in 2009, we have found 21 worlds with a size less than twice the size of Earth and that orbit in the habitable zones of their parent stars (two essential requirements for qualify as “Earth twin”. (For a series of posts about exoplanets and their characteristics, see this).
The chart gives a good representation of the candidates: the ones in orange are the nine new validated planets just announced by NASA while the blue ones are the 12 previous known planets.
“These planets are plotted relative to the temperature of their star and with respect to the amount of energy received from their star in their orbit in Earth units. The sizes of the exoplanets indicate the sizes relative to one another. The images of Earth, Venus and Mars are placed on this diagram for reference. The light and dark green shaded regions indicate the conservative and optimistic habitable zone.”
In case you wonder how Kepler managed to make all these discoveries, well, it monitored for 4 years about 150,000 stars in a single patch of sky, measuring the tiny, telltale dip in the brightness of a star that can be produced by a transiting planet. For more details about the five main methods to discover exoplanets, this interactive page is a good starting point.
We can expect exoplanet discovery to continue and accelerate in the near future, especially when, in 2018, NASA is going to launch its Transiting Exoplanet Survey Satellite, which will use Kepler’s method to monitor 200,000 bright nearby stars and search for planets and focussing on Earth and Super-Earth-sized.
In the meantime, you can play with NASA’s application Eyes on Exoplanets, a fully rendered and scientifically accurate3D universe, which allows you to zoom in for a close look at more than 1,000 exotic planets known to orbit distant stars. Enjoy!