NASA has discovered another Earth? Don't fill your head too full.

NASA announced the "exciting" news about the discovery of extrasolar planets! Online public opinion suddenly fried the pot, and friends who don't care much about scientific topics are also excited: "Another earth!" "We are no longer lonely!" "Long time no see!" "Are we going to enter the new century?" "Our journey is the sea of stars!" "Goodbye, stupid human. I want to go back to my home planet. " "Dark forest! An alien attack is coming! " "It is not enough for human beings to hurt one earth. Should they also hurt another?" "The other me in the parallel world is still single ..."

Very touching brain hole, but young man, you think too much. Bian Xiao said with many years of professional experience that the final news will definitely let you down. Of course, this is not a bad thing for everyone. Nasa's prediction is that "... astronomers are close to the goal we have dreamed of for thousands of years: discovering another earth" is too easy to think about. Coupled with the constant distortion in the process of information dissemination, the public's imagination and expectation are completely different from what scientists want to say.

NASA has done this more than once, especially on the topic of extrasolar planets. But it's not that scientists intentionally mislead. They really think this new discovery is very important. However, academic circles and the public have different ideas and different standards about "another earth". If readers make up too much brain, disappointment is inevitable.

What did NASA find?

To put it simply, this time, by analyzing the observation data of Kepler mission, more than 500 new candidate celestial bodies for extrasolar planets were "wholesale", including 12 celestial bodies similar in size and orbit to the Earth, of which 1 has been confirmed as a planet, numbered "Kepler 452b".

Don't get excited. This planet is similar to the earth in many astronomical senses, but not in the sense of science fiction. Now scientists are not even sure whether it is a solid planet, let alone whether it has enough water, life, civilization and technology to attack the earth.

What are the specific similarities? The diameter of Kepler 452b is no more than twice the diameter of the earth, the distance from its star is appropriate, close to the distance from the earth to the sun, and it is in the so-called "livable zone"-meaning that if there is water on this planet, it may exist in the form of liquid, which will not be completely evaporated by the star, nor will it be so cold that it will only freeze. Liquid water is one of the necessary conditions for the existence of life. In addition, its star is very similar to our sun, its mass is 4% higher than that of the sun, and its brightness is 10%. It can be said that there is not much difference.

Considering the above factors, Kepler 452b may be a solid planet, not a gas planet like Jupiter. According to human common sense, there will definitely be more opportunities for life on solid planets. Just look at the cities on Jupiter in science fiction movies.

That's it? That's it.

What about the agreed aliens? Not exactly.

An unusual new discovery

In 20 13, there was an extrasolar planet code-named Kepler 78b. Its diameter was 1.2 times that of the earth, and its mass was 1.69 to 1.86 times that of the earth. It should be a solid planet. But its surface temperature is at least 2000 degrees Celsius higher than that of the earth, which is not suitable for life. For another example, in 20 14, Japanese scientists discovered a planet with an orbit and mass similar to that of the earth, but it was too cold, and its surface temperature was about -2 10 degrees Celsius. Kepler 186F, discovered in 20 14, is only 10% larger than the earth and is in a livable zone, but its parent star is not a star, but a red dwarf with a low temperature.

The comprehensive conditions of Kepler 452b may be more like the earth, and more intimate than many "earth brothers" who once occupied the headlines of the media. There are not many candidate planets that can reach this level, including Kepler 438b and Kepler 425b announced by NASA in June 20 15. They are also in the livable zone and may be solid planets. But this is far from satisfying the public's scientific fantasy. In this sense, Kepler 452b is not uncommon.

As for more than 500 candidate planets in the same batch, it is not surprising. With the progress of observation technology and data analysis methods, searching for extrasolar planets has become a physical activity to a great extent, just like genome sequencing after mature technology, which is being mass-produced. There are more than 4000 candidate planets discovered by Kepler telescope alone. In 2065,438+04, it once "wholesale" 765,438+05 planets.

What are scientists excited about?

Since we don't even know whether it is a solid planet or whether there is water, why do scientists say this discovery is exciting?

Because humans are so lonely.

So far, humans have not found any signs of extraterrestrial life in the universe. Optimists speculate that there may be billions of "earth brothers" in the Milky Way alone. They are of the right size and temperature, and many of them may have life. Pessimists believe that the formation of life on earth requires too many coincidences, which may have happened once in the universe.

Humans have created brilliant alien civilizations in fantasy, and their imagination has expanded to other universes. But in reality, the greatest achievement in the search for extraterrestrial life is only the level of "there was liquid water on Mars", and even the existence of microorganisms is uncertain. As for the organic matter found outside the earth, it is only methane and the like, which can completely occur through inanimate processes. As far as the current evidence is concerned, life only exists on our planet, has only evolved once, and all use the same set of chemical mechanisms. Really lonely as snow.

Humans have long wanted to get in touch with extraterrestrial civilization. Mathematician Gauss once proposed planting a large forest to form a graph of Pythagoras theorem, so as to attract the attention of aliens. The arrival of the space age has cut off the possibility of searching for moon people and Martians, but the planets in the solar system can still provide us with the conditions for the formation of life and clues to the early evolution process. At the same time, human beings set their eyes and feet farther, while searching for the traces of planets outside the solar system, while launching probes to send greetings to the vast deep space, hoping that someone can hear them.

Although there may be life forms completely different from life on earth in the universe, it is very natural to look for them from a similar angle to ours. The more similar the planet's environment is to the earth, the more likely it is to give birth to life (that's why we are so keen on Mars exploration). The two key points are: it is located in the "livable zone" and the temperature is suitable; Made of rocks, it is solid rather than gaseous (this is directly related to the size of the planet).

Among the thousands of candidate planets outside the solar system that have been discovered by human beings, most of them do not meet the above conditions. Kepler 452b is enough to excite scientists. They think that it is already very similar to the earth, which can provide many interesting research clues and help to better judge how many livable planets there are in the universe. This kind of mood is like, being far away in a foreign country, meeting a local person will be very happy. The public is looking forward to meeting their neighbors and friends who have climbed the wall together, and it is inevitable that they will be disappointed.

In order to understand the excitement of scientists, we sometimes have to slow down our imagination and wait for reality.

(Author: Wang Yanhong, transferred from Xinhuanet)