What are the chances of two earths appearing in the universe?

Do you mean a planet with living conditions, such as a rocky planet with water and oxygen, and a star with the right size? There are many of them.

This was discovered on 20 1 1.

The event that NASA Kepler planned to observe the new planet "Kepler -22b" caused an uproar. Many people interpret it as "the first habitable Earth-like planet". What is the real situation? Can the discovery of this new planet make human beings realize their dream of emigration?

Recently, scientists who participated in NASA's Kepler mission announced that they had discovered a new planet that might be suitable for living around a sun-like star for the first time through the Kepler telescope. The exposure of this achievement has aroused people's infinite reverie, and this paper will also interpret the most concerned issues in the incident one by one.

How did Kepler 1 discover this planet? How accurate can these techniques and methods be?

Planets themselves do not emit light, so direct observation is very difficult. However, if the unlit planet passes in front of the star, it will block part of the starlight, causing the brightness of the star we see to dim slightly in a short time and then return to normal. If such starlight dimming happens periodically, it can be determined that there is an invisible planet there after at least four observations.

Kepler telescope is a special detector for NASA to discover alien planets in this way. Since its launch in 2009, it has been continuously monitoring about 654.38+0.5 million stars and recording their subtle changes in brightness. If the earth passes in front of the sun, the blocked sunlight will reduce the brightness of the sun by about one millionth, while Kepler can detect the change of starlight as weak as one millionth.

The new planet "Kepler -22b" was discovered in this way-Kepler telescope observed that the period of the star was about 290 days, and the starlight dimmed and returned to normal. Astronomers have determined the radius of the planet according to the dimming range of the brightness of the star, which is about 2.4 times that of the earth; According to the period of this phenomenon, astronomers calculated the orbit of the planet and determined that it was just in the "livable zone" of that star.

Why might this new planet be habitable?

Let's take a look at our most familiar solar system: the solar system has eight planets, and only the earth has a pleasant temperature, so that water can exist on the surface in liquid form for a long time. Why is this happening? The fundamental reason is that the distance between the earth and the sun is neither too close nor too far, and the solar radiation received is just right. The area around the sun that can meet this condition is called "livable zone".

The distance from the livable zone of different stars to the stars is not fixed, which has a lot to do with the properties of the stars. If the temperature and brightness of a star are higher than that of the sun, the livable zone will be farther away from it; If the temperature and brightness are lower than the sun, the livable zone will be closer. In addition, the livable zone is not a very narrow area. The livable zone of the solar system extends from the outer side of Venus orbit to the outer side of Mars orbit, so strictly speaking, both the Earth and Mars are in the livable zone of the solar system. It's just that Mars is too small to maintain a thick atmosphere. Later, it became cold and dry and uninhabitable.

Kepler -22b revolves around a sun-like star. The light emitted by this star is about 25% weaker than sunlight, so the livable zone there is closer to the star than the livable zone of the solar system. On the other hand, the distance from Kepler -22b to its parent star is about 15% shorter than the average distance from the earth to the sun, which just makes it comfortably in the livable zone. Therefore, if the nature of the new planet is similar to that of the earth, liquid water can exist on the surface of that planet for a long time.

Scientists are not sure whether the planet is liquid or solid, so how can you be sure that the surface temperature of the planet is 2 1 celsius?

Through the observation of Kepler telescope, astronomers can measure how far the new planet is from its "sun" and how much light and heat its "sun" can release at any moment. However, it is still impossible to determine the temperature of the planet surface only by these two conditions, because the latter is not only related to the intensity of "sunlight", but also to many properties of the planet surface and even the atmosphere.

The Kepler telescope's method for finding alien planets can't determine the quality of the planets, nor can it directly observe the planets, so it is difficult for astronomers to determine whether the planets are rocky planets like the Earth, gaseous planets like Jupiter, or even completely different liquid planets. As for what kind of atmosphere the planet has and what kind of material the surface is made of, it is even more unknown.

However, if we assume that this planet is very similar to the earth, with similar land and sea and similar atmosphere to produce greenhouse effect, astronomers can calculate that its average surface temperature is about 22℃. But this data can only be regarded as "for reference only" because there are too many uncertainties. Assuming that other conditions remain unchanged, but there is no atmosphere on the surface of that planet, the average surface temperature will be as low as-1 1℃.

Is this really the "first habitable terrestrial planet" confirmed by NASA?

This planet is not "the first habitable terrestrial planet" as reported by some domestic media. When NASA official website released this news, he used the title "NASA Kepler mission confirms that its first planet is in the habitable zone of sun-like stars". The correct Chinese translation should be "NASA Kepler plans to confirm that its first planet is in the habitable zone of sun-like stars".

The "first planet" here refers to the first one confirmed by the Kepler project, not the first livable planet discovered by astronomers. In fact, Kepler has discovered 2326 suspected planets around about 1.5 million stars it monitors, of which 207 are close to the Earth, 680 are super-Earths,165,438+086,5438+0 are Neptune, 203 are Jupiter and 55 are Jupiter.

Kepler must observe the dimming of starlight four times to determine that this phenomenon is indeed caused by the blocking of starlight by planets-this step is called "confirmation". Among the planet candidates announced by Kepler in February this year, 54 planets may be located in the "livable zone", and Kepler -22b announced this time is the first confirmed planet. Among the newly announced planetary candidates, 48 may still be located in the "livable zone".

In addition, this planet has not been proved to be a terrestrial planet, which is also a myth.

So far, Kepler probe has found 2326 candidates for suspected planets, but its main scientific purpose is not to find planets suitable for human habitation. Image from NASA.

What impact will this discovery have on academics and reality?

The main purpose of Kepler probe in science is not to find another earth suitable for human habitation, but to conduct a small-scale "population spot check" on the planets in the Milky Way. In other words, through Kepler's continuous monitoring of about 65.438+0.5 million stars, astronomers want to know what percentage of the 200 billion stars in the Milky Way have planets, how many planets they have, and what are the statistical distribution laws of the heads of these planets and the distances from their parent stars. These basic information will be of great help to the study of the formation of planets and stars.

Therefore, in this batch of data released by Kepler, astronomers pay more attention to the number of candidate planets of various sizes in the newly announced planetary candidates. Of course, it is also important to determine Kepler's first livable planet, which at least provides a conclusive evidence that livable planets in the Milky Way are not very rare. This discovery also provides an alternative observation target for more advanced observation equipment in the future. By then, with the help of more advanced equipment, we may be able to measure the mass of this planet, even analyze its atmospheric composition, and infer whether it is really livable with more accurate data.

At this stage, the main significance of this discovery is that it has become a hot topic, leading the public to pay attention to science and lead us to explore the unknown world. At the same time, it also provides an opportunity for scientists to show their work and achievements to the public. The yearning for the unknown alien world may plant a curious seed in many people's hearts, and even have the opportunity to sprout into a love of science.

What is the possibility of human migration to this planet?

Among the existing man-made spaceships, the fastest one is the "New Horizon" probe flying to Pluto, and its speed is about 15.5 km/s at present. If it flies to Kepler -22b 600 light years away at this speed, it will take about11600,000 years to arrive. Even the closest star to the sun, proxima centauri is 4.22 light years away. According to the current speed of New Horizon, it will take at least 80,000 years to reach proxima centauri. Therefore, according to the existing technical level of human beings, the possibility of emigrating to this planet is almost zero.

Of course, the possibility of a breakthrough in human science and technology cannot be ruled out. Maybe one day, we will build a spaceship with the speed of light and open an "arbitrary door" that can shuttle through the universe. At that time, if observation proves that Kepler -22b is indeed a terrestrial planet and suitable for human habitation, it may become a destination for human exploration and even settlement in the future.

/article/778 14/ hope to adopt.