How are the breathtaking photos of the deep space of the universe taken?

When a picture of a nebula in the depths of the universe is presented to us, we will be shocked by the vastness and magic of the universe. To ask how this picture came from, most people know that it was taken by a telescope, but many people don't know that it was taken by a telescope under long-term exposure.

It is impossible to see the gorgeous scene in the photo directly with a telescope. At that moment, our eyes can receive so few photons that we can hardly see anything. In order to receive as many photons as possible, people try to make the lens of the telescope bigger, and a bigger lens is helpful to receive photons from distant stars.

In fact, there is another way, and that is long-term exposure.

When taking a photo, just press the shutter for less than a second, and a photo will appear in front of us. In this short time, light will come in from the lens and shine on the photosensitive element, and tens of millions of photosensitive points on the photosensitive element will record the photons that shine on it.

A perfect photo must have the right exposure. If there is too much light, the photos will shine and the night will become day. If the light input is too small, the photo will be dark, so it is important to control the exposure time.

Astronomical photos, because the starry sky is too dark, need long exposure. The longer the exposure time, the more photons you get, and the clearer and more perfect the photo will be.

The photos taken by large astronomical telescopes are all obtained in a long exposure state, and the exposure time is as long as several hours, and this is just a clear photo of the target.

For dim celestial bodies in the depths of the distant universe, they are almost invisible, or dim, and need a longer exposure time. As long as the time is long enough, you will find that there is not nothing there, but also many celestial bodies. Generally, celestial bodies in the depths of the universe need long exposure to be presented.

In 2004, Hubble telescope photographed the blank area of Nantian Spherical Furnace constellation, and the exposure lasted for several hours, and obtained Hubble deep space photo HUDF. Thousands of dim and extremely distant galaxies appeared in the photo, which became the most far-reaching image of the universe at that time.

10 years later, Hubble pointed the lens at a small piece of night sky in the southern sky again and observed it for 50 days. The cumulative exposure time exceeds 2 million seconds. This long exposure took another XDF field of view, which was composed of many photos, and made us see the depths of the universe more clearly.