Kepler first discovered candidates for rocky planets in the habitable zone

The Israeli astronomer Avi Shaforer from the University of California at Santa Barbara was also involved in the discovery

NASA's Kepler Space Telescope has discovered candidates for an Earth-sized planet, the first of its kind, and more importantly the first of its kind to be discovered in the habitable zone, a region where liquid water can exist on the planet's surface.
Five of the candidates for planets similar in size to Earth are in the habitable zone of a star smaller and colder than the Sun. Kepler also discovered six already confirmed planets orbiting the Sun-like star Kepler-11. This is the largest group of planets orbiting a star discovered by the eclipse method.

Kepler observes the signature of the planets by measuring the tiny drop in star brightness caused by the planet passing in front of them in our field of view. This method is known as the transition method. Since the transit of planets in the habitable zone of a sun like ours takes about a year, and three transits are required to confirm the fact that it is a planet, confirmation of the discovery will require at least three years.

The Kepler mission discovered 1235 bodies that could be planets, including 54 planets that are just the right distance from their star so that they are neither too hot nor too cold and may contain liquid water. IT is calling us and maybe even calling us right now...

Nature magazine reports that hundreds of celestial spots have been identified, which they estimate may be planets, and even some of them could definitely be candidates for Earth number two - a small rocky planet, with an orbit of several hundred days, on which water can exist and, of course, life.

Last month, according to Nature, NASA announced the discovery of the smallest planet that exists outside our solar system. Its diameter is 1.4 times that of Earth and its mass is 4.6 times that of our planet. Although the planet orbits too close to its star to support life, the news was reported as a major breakthrough in the search for a new Earth, especially because it is the first rocky minor planet outside the solar system.

The planet was discovered by NASA's Kepler spacecraft. The Kepler spacecraft was designed as a space telescope with a diameter of 0.95 meters in order to discover exoplanets (planets outside the solar system). It works by monitoring changes in the light from the stars. Unlike most ground-based telescopes, the Kepler mission is designed to focus on the same field of view for 3 to 4 years. This field contains about 150,000 stars in the Lyra and Cygnus systems. These systems were chosen because they have so many stars that they are similar to our sun. Because Kepler focuses on the same point he is able to repeat observations, make three or four repeated observations of transits of minor planets in one-year orbits, the orbit of the Earth around the Sun. And so it is able to capture planets similar to ours.

Two astronomers from the Department of Physics at the University of California, Santa Barbara, Tim Brown and Avi Shaffer, are involved in the mission. Both are also scientists at the university's Coombs Global Observatory, which is run by Brown.

Brown is a co-researcher at Kepler and he had a significant role in the project from the beginning of its planning in the early nineties. Among other things, he signed a catalog of about 156 sun-like stars among the millions of stars in Kepler's field of view.

Statistical analysis of samples of many planet candidates show us that planets come in groups, this means that they reside side by side with other planets and are not alone," Shaporr said.

Another interesting result based on the large sample of candidates discovered by Kepler is that when you consider the geometric probability of the planet Albor from its sun, close to 20% of all stars that have planets, this means that a significant fraction of the stars in the sky are surrounded by alien worlds ” says Brown.

Neitzer says that every month the astronomers download from the Kepler spacecraft to the computers at NASA a stream of light intensity data captured by Kepler. There is a decrease in the brightness of the stars as the planets pass in front of the stars or pass by them. Astronomers need three to four such transits to be sure they have found a planet. These data are converted into graphs that the computer produces. The graphs show the intensity of the light from the star on one axis and on the other axis the change in time of this intensity. Draw additional graphs and get spots that correspond to the planets. Then they filter out the noise of the instruments in the Kepler spacecraft. After all the tedious process they conclude that some of the data are planets. To know that it is not noise but a real planet, the Spitzer space telescope is used, which is sensitive to infrared radiation. It is ideal for noise cancellation. Kepler's findings are also used to direct telescopes here on Earth.

Based on Kepler's data, the researchers found a system in which there is a pair of planets, which are about the size of Jupiter, and have a mass that is of the order of that of Saturn, and they orbit the same star in orbits of several days. Another giant planet was discovered in the same system. Then they discovered another system, where six planets orbit a star and have cycles of between a few days and almost 120 days. Their masses range from twice that of the Earth to 300 times the mass of the Earth. And now they discovered another dense planet, which revolves around a star just like our sun in a short 84-day orbit. The planet is very close to its sun and its mass is 4.6 times that of Earth. And there is no doubt that in this situation it is rocky. But because it is close to its sun at least one side of it must be melting all the time.

All exoplanets confirmed to exist so far orbit much closer to their stars than Earth does. They are too close to the star to develop the existence of flowing water, which is what defines a "habitable zone". However, as the data is collected from the Kepler spacecraft and carefully examined, it is estimated that they will produce reports of smaller and smaller planets, until we get an example that is exactly the size of Earth.

Eventually we may find an Earth-like planet orbiting a star similar to our Sun. If this were to be the case, should the planet be the size of Earth? And should we focus on a planet on which liquid water flows? Perhaps in general life in other remote corners of the universe is more diverse and strange than we expected. In this situation, we might think about life on a completely dry world and then discover the first planet capable of supporting life that we never expected to discover.

• to the article in Nature
• For information on the NASA website
• For information on the website of the University of California at Santa Barbara