Planet image photography

Our earth is a planet. It goes around the sun. Our earth doesn't shine, so although the sun can be seen from far away, it is also a star, just like the star we see at night. However, our earth looks extremely dim in the distance, so dim that it is difficult to be found without special means.

Voyager 1 returned from Pluto orbit and took a family photo of the solar system, including an image of the earth. This photo was called "light blue spot" by Carl Sagan, an American scientist and popular science writer. In this photo, the earth shows only a few pixels. But Voyager 1 is only a few billion kilometers away from us. From the perspective of the universe, it is still next to the solar system, far from "seeing the earth on other planets", but the earth has become so dim.

In fact, this can be explained by our observation of extrasolar planets. Ever since Copernicus told us that the earth is also a planet, astronomers have been speculating that the sun is also a star, and there should be planets around other stars. But in 400 years, astronomers failed to find planets around other stars.

Several planets were discovered around pulsars for the first time. According to the disturbance of the planet to the pulsar, its frequency spectrum has changed, so it has not been directly seen. It was not until this century that astronomers developed more advanced means, which can shield the light emitted by stars by optical means and directly detect the light reflected by planets with large telescopes, which is as difficult as detecting a firefly a few meters away from a bright street lamp in the distance.

We can imagine that astronomers from other planets must at least develop the same technical means to find the earth, and the telescope should be aimed at the sun.

The problem is that our universe is so huge, the Milky Way has 200 billion stars, and our sun (at present) is on the spiral arms with relatively dense star distribution.

So aliens may not find us that easily. They can only find stars and planets near other solar systems, and they can roughly know their orbits, but we need to further develop our science and technology to understand the more specific conditions of those planets.