NASA published revised data from the Kepler Space Telescope, revealing the existence of 219 exoplanets observed over the course of its first mission. Researchers suggest that in total, the telescope has found 50 habitable zones with a total of 10 planets orbiting within them.

A habitable zone refers to the area surrounding a star where liquid water could exist on a planet’s surface.

Kepler-186f, the first rocky planet found in the habitable zone of its host star. The discovery was made by analyzing data obtained by the Kepler Space Telescope up until 2014. Image credit: NASA Ames/Seti Institute/JPL-Caltech
Kepler-186f, the first rocky planet found by Kepler in the habitable zone of its host star. The discovery came from data obtained by the Kepler Space Telescope up until 2014. Image credit: NASA Ames/Seti Institute/JPL-Caltech

The Kepler space telescope has found a total of 3,496 planets among 4,496 candidates, distributed in 582 planetary systems.

The released data comes from the eight Kepler space telescope catalog. Researchers will make use of the new findings to look for planets that could potentially harbor life.

More discoveries from the Kepler Space Telescope’s catalog

The catalog comes from analyzing once again the data obtained by the telescope during the first fours years of its primary mission, known as K1. The issue is that the telescope could have misinterpreted luminosity signals, counting them as planets, or perhaps by counting the same planet more than once. Researchers created false signals to test the telescope’s efficacy and then recalculated the existing data.

They managed to classify observed planets into two additional categories apart from “giant planets”: Those composed primarily of rock and more or less the size of the Earth, and those composed of gas that are smaller than Neptune. Neptune is 17 times the mass of the Earth and 57.74 times larger.

Rocky planets were almost always bigger than the Earth, although the reason why remains a mystery. The most common variety were planets 75 percent larger than the Earth; half of these worlds are packed with dense clouds of hydrogen and helium.

“We like to think of this study as classifying planets in the same way that biologists identify new species of animals. Finding two distinct groups of exoplanets is like discovering mammals and lizards make up distinct branches of a family tree,” stated Benjamin Fulton from the University of Hawaii at Manoa, who led the effort to find the radius of about 2,000 Kepler planets by studying the 1,300 stars they orbited.

Despite the fact that there are thousands of planets, only a handful are habitable. Additionally, about half the planets known to exist either have no solid surface or their atmosphere is so dense that life as we know it cannot possibly thrive on it.

“This carefully-measured catalog is the foundation for directly answering one of astronomy’s most compelling questions: how many planets like our Earth are in the galaxy?” stated Susan Thompson, from the SETI Institute.

Graph showing discovered planets. Yellow dots represent the ones discovered in Kepler's eight catalog. Image Credit: NASA/Ames Research Center/Wendy Stenzel
Graph showing discovered planets. Yellow dots represent the ones presented in Kepler’s eight catalog. Image Credit: NASA/Ames Research Center/Wendy Stenzel

The Kepler Space Telescope’s quest for habitable planets

NASA scientists are pleased with what the Kepler space telescope has achieved, as it was the primary source for finding potentially habitable exoplanets. Besides finding these planets, the telescope helps researchers understand how frequent they are and if they can predict their existence to some extent.

The Kepler K1 mission was to explore and structure planetary systems that contain planets similar to the Earth. But one might wonder how a telescope identifies a planet out of the millions of stars scattered throughout the universe.

The method is pretty simple actually. When a star shines, its light reaches as far as it possibly can. In the case of the Kepler Space Telescope, the light enters its receptors, and the telescope can make a measurement of the star’s location and luminosity.

Now, if a planet happens to orbit that star, then its luminosity will steadily drop for the period that the planet travels between the star and the telescope, only to regain its initial intensity after the planet has passed. This event is known as a “transit,” and astronomers can see Mercury and Venus transit when the Sun’s luminosity drops for a small window of time.

The next step is to calculate the size of the planet’s orbit by measuring how long the planet takes to pass between the star and the telescope. The magnitude of the drop in brightness and the size of the star can reveal the planet’s size.

Finally, from the star’s temperature and the data mentioned above, astronomers can calculate the planet’s temperature and hypothesize whether it is habitable or not.

Interestingly, Kepler’s primary mission ended in May 2013 after one of the telescope’s reaction wheels malfunctioned. The mission was redesigned back in 2014 and is expected to end sometime in 2017 or 2018. Still, three years after obtaining the first dataset of Kepler’s observations, researchers could find more planets, showing that an equipment malfunction rarely limits the possibilities for deep-space exploration. Now, the redesigned K2 mission has the telescope serve as a communications array.

“It feels a bit like the end of an era, but actually I see it as a new beginning. It’s amazing the things that Kepler has found. It has shown us these terrestrial worlds, and we still have all this work to do to really understand how common Earths are in the galaxy,” stated Thompson

Source: NASA