How did scientists know that there are two trillion galaxies in the universe? | Science

Astronomers expect to be able to look back 200 million years after the Big Bang through the James Webb Telescope.

Our visible universe, which spans billions of light-years in all directions, contains numerous galaxies. Each galaxy has a large galaxy. But have you ever wondered how many galaxies there are in the universe? Counting and calculating the limits of our tools seems like an impossible task.

According to For an article Released on Big Monday, the exact number of galaxies remains a mystery, with ratings rising from thousands to millions to billions, all with advanced telescope technology.

If we make the most accurate estimate using the best technology available today, we would say that there are 170 billion galaxies in our universe. But recent estimates suggest that there are more than two trillion galaxies in the universe, so we know that.

Hubble deep field image

The technique used by scientists to observe galaxies in the universe is to operate a telescope to observe for a long time in a certain empty space in the sky where there are no known stars or galaxies. The longer the telescope observes the space, the more light it collects – from a distance – so that more galaxies are found in the universe.

Scientists first did this in the mid-1990s using the Hubble Space Telescope, which focused on observing a specific sky over 32 million areas of the sky, almost none of which.

By observing that small sky, the Hubble Extreme Deep Field (XTF) image was created, revealing a total of 5,500 galaxies, indicating the highest density of galaxies ever observed. This is the best attempt by scientists to track the number of galaxies in the universe.

The next step is to estimate the number of galaxies in the entire universe, which is one way, when we take a portion of the sky captured by a telescope. Then you can determine the number of galaxies in the universe by using the ratio of the area of ​​the sky to the whole universe.

Assuming that there is no significant cosmic variation and that the universe is homogeneous, the same evaluation method can be followed. Says Mario Livio, an astronomer at the Space Telescope Science Institute in Baltimore, Maryland. A statement Posted on “Space” According to Albert Einstein’s theory of general relativity, the universe is identical to the cosmological principle.

Also, according to NASA, if you look at the contents of the universe, it appears almost identical everywhere and in all directions. This means that the matter in the universe is homogeneous, albeit averaging in very large quantities, which is called cosmological principle.

So, we can estimate the number of galaxies in the universe by taking the shape we observed in the form of the Hubble Deep Field, i.e. 5,500 galaxies, and multiplying it by the number of images that would cover the entire sky, i.e. 32 million. , Which will eventually form 176 billion galaxies in the universe.

However, this is not an actual estimate. This is a very small amount, because galaxies that are very faint, very small, or very close to other galaxies are visible in this estimate. Also, galaxies obscured by neutral gas and dust are nowhere to be seen, and galaxies outside the redshift capabilities of the Hubble telescope are nowhere to be seen.

Two trillion galaxies .. How?

Today, scientists estimate that the number of galaxies visible to Hubble is 10 times greater than the number of galaxies in the observable universe. But how did this number come about?

According to BigThink, the big raw material to come up with a real estimate is how precisely the structure in the universe develops. If we can run a simulation that starts with the elements that make up the universe, the exact starting points that reflect our reality, and the exact laws of physics that describe nature, we can simulate how the universe came to be.

Significantly, when we look at simulations that best fit the observed data, we get an estimate of the actual number of galaxies in our observable universe, which is two trillion.

If we compare this number with the number we got from the “Hubble Deep Field” image, we can see that 90% of the galaxies in our universe are far beyond the detection capabilities of mankind’s largest laboratory.

Livio says astronomers could improve this figure by looking through the James Webb Space Telescope, as scientists expect the Hubble Space Telescope to look back at galaxies that formed about 450 million years later, while astronomers could look back to 200. Millions of years after the Big Bang by the James Webb Telescope.