Move to the moon 600

For hundreds of years, it has been a scientist's dream to find alien life and civilization. Of course, scientists are not like some people who eat melons. When they see something they don't understand, such as UFOs, they dream and insist on blaming aliens.

Scientists are talking about evidence, and now the evidence is that cells have not been found on other planets in the solar system except the earth.

The first thing is to look for planets outside the solar system that are attached to other stars, especially terrestrial planets in livable zones. The so-called livable zone is an area where the planet temperature is neither too hot nor too cold and liquid water can exist at a suitable distance from the star; Earth-like planets, like the earth, are surrounded by a layer of rock with a solid surface.

Because scientists are convinced that livable zones and terrestrial planets are necessary conditions to find life similar to Earth. Of course, there may be life or civilization completely different from the earth in the universe, and under what conditions can these lives and civilizations be bred and evolved. At present, there is no discovery and no theory, so we won't discuss it today.

Since the invention of the telescope, scientists have been looking for planets outside the solar system for hundreds of years, but it is disappointing to find a needle in a haystack. Until 1992, two American astronomers, aleksander wolszczan and Dale Flair, first discovered two exoplanets orbiting pulsars, which were named PSR B 1257+ 12 B and PSR B 1257+ 12C respectively. 1995, two Swiss astronomers, Mike Meyer and Didier Queloz, first discovered an exoplanet orbiting a sun-like star and named it Pegasus 51b.

Since then, the search for exoplanets (extrasolar planets) has become a hot topic for astronomers. Many ground-based telescopes and scientific project teams have joined the search for exoplanets, and new planets are constantly being discovered. Hubble, the first space telescope launched in 1990, was the first to discover the planets around Beiluoshimen by direct imaging. However, some of these findings are "amateur" and even "professional" are not efficient. The scientific community urgently needs a more professional and efficient exoplanet search plan.

Kepler Mission (sometimes abbreviated as Kepler), also known as Kepler Mission in English, is the world's first space telescope dedicated to detecting terrestrial planets outside our solar system. It was launched from Cape Canaveral Air Force Base on March 7, 2009.

Johannes kepler was a German astronomer and mathematician in the17th century. He discovered three laws of planetary motion, namely, the law of orbit, the law of area and the law of periodicity, which made great contributions to human understanding of the universe and planetary motion. The Kepler mission was named after him.

Kepler telescope does not revolve around the earth like Hubble telescope, but revolves around the sun like the earth and follows the earth's ass like a follower, but will gradually move away from the earth after four years, about 0.5 AU (75 million kilometers) away from the earth. Its observation field of view points to the field where Cygnus and Lyra are located, far away from the ecliptic plane, so that it will not only be covered by the earth, but also be able to observe continuously, and will not be affected by the diffusion of the earth and the moon, nor will it be leaked by sunlight.

Kepler's mass is about 1.039 kg, its aperture is 0.96 m, its primary mirror is 1.4 m, and its field of view is about 105 square degree (apparent diameter is about 1.2 degree). Kepler's field of vision is similar to that covered by a fist when a person stretches out his arm. The observation depth is about 3000 light years, and the width is about 0.5% of the whole day.

Kepler showed its extraordinary strength as soon as it was launched. During its service for more than 9 years, more than 5,000 candidate exoplanets were observed, and 2,662 were confirmed by examination, including 49 candidate habitable terrestrial planets and more than 30 confirmed.

The global scientific community also uses various methods to find exoplanets. The first exoplanet was discovered in 1995. By the end of 2020, the total number of exoplanets discovered is 4373. From this data, the discovery of Kepler mission alone accounts for more than 60% of the total number of discovered exoplanets.

At present, there are many scientific methods to detect exoplanets. For example, the earliest planets were discovered by the apparent velocity method, as well as the gravitational microlens method, astrometry, chronometry, occultation method and so on. These are measured by indirect observation and physical principles.

Exoplanets cannot be directly "seen" and can only be "measured" by means of stellar light variation and gravitational perturbation. Because the angle of view of exoplanets is too small, there are only 100 planets discovered by direct imaging method. The planets discovered by this method are all huge "hot Jupiter", that is, young wooden planets with a temperature of 600~2000K, and most of them are dozens of times the mass of Jupiter.

Direct imaging is not able to "see" directly, but to "measure" through the invisible infrared light changes of stars. These methods of searching for exoplanets all have a very complicated theory, so I won't talk about it today, just occultation method.

The Kepler mission used occultation method to find exoplanets. Occultation method, also known as transit method or transit method, is a method to determine the existence of planets by observing the subtle changes of stellar luminosity when exoplanets cross the surface of stars in a visual direction.

Therefore, the most important instrument installed on Kepler is the high-precision space photometer developed by NASA. Its main function is not to obtain a clear image of the planet, but to obtain the luminosity change of the star by measuring the luminosity of the star, so as to calculate whether there are planets around it.

Kepler observed a sun-like star with m(V)= 12 for 6.5 hours, and it could detect 20ppm (20 parts per million) of comprehensive luminosity change, while the luminosity change caused by a planet similar to Earth was about 84ppm.

In this way, "Kepler" directionally observed the luminosity of 654.38+ten thousand stars in orbit, and detected the existence of planetary transit through the subtle changes of stellar luminosity, and calculated the period of revolution, orbit size, transit depth and planet size. For the transiting planet, its mass is also calculated by the spectrum and luminosity of the planet's parent star, so as to calculate whether the planet is in a livable zone.

Before Kepler's launch, the exoplanets discovered by the scientific community were basically "hot Jupiter" with great mass and volume. After Kepler's launch, a large number of smaller terrestrial planets similar to Earth were discovered, the first star system with six planets, the first planet orbiting two stars and the smallest planet orbiting a sun-like star were discovered.

In order to facilitate reading, the naming rules of planets are particularly explained: after the star name, the planets are named B, C, D, E, F, G, H, etc. according to the order of the planets approaching the main star. The planets discovered by Kepler all begin with Kepler's star name. For example, Kepler 20 is a star name, and Kepler 20e is a fourth-order planet near Kepler 20.

Kepler 20e and Kepler 20f are the earliest asteroids discovered by human beings. The radii of these two stars are 0.8 times and 1.03 times that of radius of the earth, respectively. They are two of the five planets in Kepler 20 system, about 950 light-years away from us. Kepler 20 is a sun-like star, its mass is about 9 1% of that of the sun, and its surface temperature is slightly lower than that of the sun, about 5466K K k. These two terrestrial planets are too close to the main star and are generally considered unsuitable for life, while other planets are woody planets.

But this discovery is an important turning point, ending the history of not finding exoplanets.

The smallest planet discovered by Kepler is the planet in Kepler 42 star system. It is a red dwarf star only 126 light years away from us, with a mass of only 0. 13 times that of the sun and a luminosity of only 0.24% of the sun. At present, it is found to be accompanied by three planets, of which Kepler 42b is about 0.78 times the size of the earth, Kepler 42c is about 0.73 times the size of the earth, and Kepler 42 is about 0.73 times the size of the earth.

Kepler 186 is a red dwarf star about 500 light years away, and its mass is about 0.54 times that of the sun. It is accompanied by five planets, of which Kepler 186f is the most striking, and its size is about 1. 1 times that of the earth. In the livable zone, some scientists analyze that it may be the most promising planet for life. However, some analysts found that although they are cousins of the earth, they are not twins. In the marginal area outside the livable zone, there is likely to be water ice instead of liquid water, which may be unsuitable for living.

Kepler 1649c is an accidental discovery. This planet, which was omitted in the review, was accidentally discovered when Kepler re-examined the materials taken by Kepler in 2020 after several years of retirement. This planet, which is about 300 light-years away from us, is a rocky planet with a volume of 1.06 times that of the earth. Theoretically, it is in the livable zone of stars and is considered to be the most earth-like planet so far.

Disappointingly, because its main star is a red dwarf, its mass is very small, so the livable zone is very close to the main star. Kepler 1649c period of revolution only has 19 days, which is not suitable for life.

Kepler also discovered Kepler 90 galaxy, which is a solar system similar to Draco, which is 2545 light years away. It is the star system with the largest number of exoplanets discovered so far, and it is accompanied by eight planets like our solar system.

There are many kinds of exoplanets discovered by Kepler, including planets orbiting two or even four stars, and many big cousins of the earth, such as Earth 2.0, which cannot be described here.

In recent years, in the process of searching for extraterrestrial planets, many planets that look like the earth have been discovered, such as Big Sister and Earth 2.0. So will there be aliens on these planets?

In fact, "Kepler" doesn't know, and no one knows. Because although human beings have made continuous progress in observing exoplanets, none of them can really "see clearly". Those so-called big cousins, Earth 2.0 and so on. Just screaming, it's far from the earth's aura. Just as it is difficult to find two identical leaves or two fingerprints on the earth, it is also difficult to find a planet exactly like the earth in the universe.

There may be extraterrestrial life and civilization in the universe, or there may be life or civilization completely different from the earth, but so far there is no evidence or even any clue in this regard. In this case, as a rigorous popular science article, we can't speculate at will.

The 20 18 Kepler mission had to be gloriously retired because of fuel exhaustion, so who will fill its position? Will the future planetary search plan be shelved? You don't have to worry. A new generation of planet hunters developed by NASA has appeared for a long time. It is a new generation of exoplanet survey satellite, TESS for short. It was successfully launched on April 9, 20 18, Beijing time, replacing the older generation of Kepler and continuing the unfinished business.

TESS's observation area is 400 times that of Kepler, which means it can search all day. It divides the sky into 26 different regions and surveys the sky once every 27 days, focusing on the 200,000 largest and brightest stars near the earth. Scientists hope to find at least 20 thousand exoplanets through it and find a more livable planet among them.

Searching for exoplanets, on the one hand, is to discover extraterrestrial life or civilization, on the other hand, is to find the most suitable place for human beings to migrate to other planets in the future when the earth is uninhabitable. This is a preventive measure for human reproduction and a great move by a group of far-sighted scientists, industrialists and politicians. As a human being, I am very glad to have such excellent peers.

What did you say?/Sorry? Welcome to the discussion and thank you for reading.