Photographer starlight

The moon is full of stars. When we look up at the stars, all we can see is what they used to be. Of course, it is true that stars enter our eyes, but it takes a long time for these stars to reach the earth. At this moment, the light they emit will last for years or thousands of years before reaching the earth and being seen by us.

The above picture shows the beautiful Milky Way, which was shot by a photographer near the Andes in Chile at an altitude of 5000 meters. Bright Jupiter protrudes from the center of the Milky Way. On its right is the obviously dark yellow giant Antares, and on the far right edge is the Small Magellanic Cloud, one of the satellite galaxies of the Milky Way. Source: NASA official website.

The narrow sense of "stars" refers to those luminous "points" in the night sky, which can be roughly divided into the following categories:

1, some planets close to the earth in the solar system, such as Venus, Jupiter and Saturn. ;

Sometimes you can see those moving stars in the night sky. They may be satellites or the International Space Station. For example, Dongfanghong No.1 in China may be visible to the naked eye.

The stars that are most easily seen by naked eyes are stars, such as the Big Dipper, Sirius, Polaris, Altair, Vega and so on. These stars are in the range of tens to hundreds of light years from us;

4. The last category is extragalactic galaxies, but it is hard to see with naked eyes, because it is too far away from us, including large and small Magellanic galaxies, Andromeda galaxies and triangle galaxies. It is relatively close to the Milky Way, and the farthest triangle galaxy is about 3 million light years.

The latest data on the diameter of the Milky Way is 200,000 light years. The solar system is located on one of its spiral arms, about 26,000 light years away from the center of the Milky Way. Generally, the stars visible to the naked eye are all within the "small white circle" in the above picture.

We all know that the speed of light is 300,000 kilometers per second. People see objects because light enters our eyes, so the light emitted by objects does not reach our eyes instantly, but takes time. Especially when the distance is too large to ignore the travel time of light, for example, the average distance between the sun and the earth is 65.438+0.5 billion kilometers, and it takes about 8 minutes and 20 seconds for light to reach the earth from the surface of the sun. This also means that the sun we see every day is what it was 8 minutes and 20 seconds ago. If the sun suddenly disappears at this moment, you can see the scene when it disappears on the earth after 8 minutes and 20 seconds, and then the earth will completely enter the dark moment.

Source: NASA official website invaded and deleted.

Even in daily life, when an object is one meter away, what we see is the same as before, but this time interval will be very broken, and the time for flying at the speed of light for one meter can still be ignored. So what we see is the past, and scientifically speaking, "looking to the future" is impossible.

Text/science black hole, image source network intrusion.