Can You See the Actual Black Hole

One recent research team found 12 more small black holes within 3 light years from the center of our galaxy. Because black holes emit X-ray radiation only when they consume material, so many black holes remain undetectable. Thus, scientists have discovered 12 black holes, suggesting that there are tens of thousands of black holes in the area.

But until now, no astronomer has ever seen a real black hole. Because black holes absorb all electromagnetic radiation, including light, because they are not observed with any telescope of mankind. The photographs of black holes that we often encounter in science magazines and Internet astronomy sites are all merely illustrations of images.

The biggest problem with the black hole observation is that it is relatively small in spite of being a million times as heavy mass as our sun. Moreover, black holes are surrounded by other bright substances due to strong gravity, so the material itself is difficult to see.

Instead of attempting direct observation of black holes, astronomers choose to find indirect evidence of gravitational and radiation effects of black holes. It measures the orbit of a star or gas that seems to revolve around a very dark point in space, and measures how much mass there is at that dark point.

Unless there is a huge and dark astrophysical object so measured, astronomers see a black hole there. The Chandra X-ray telescope, launched into space in 1999, took quite a bit of indirect images of black holes in this way. This telescope is a space telescope specially designed to see X-rays, because the friction and high velocity of matter formed in the black hole naturally produce X-rays.

Super mass black hole with 4 million times of sun

For example, the gravitational force produced by Sagittarius A *, a super-mass black hole in the center of the Milky Way Galaxy, increases the star’s revolution rate of S2, about 15 times larger than the sun, to about 17.7 million km per hour. Recent astronomers have witnessed the S2 passing through Sagittarius A * at a speed of more than 25 million kilometers per hour. This is a huge rate of about 6940 km per second.

Scientists have recently obtained another concrete evidence that Sagittarius A * is a super-mass black hole. As the S2 slipped through it, astronomers from the European Southern Observatory (ESO) witnessed a short, powerful gas flare from the Accretion disc.

The outer disk of the event horizon, which has a very high temperature outside, is a peripheral area of ​​the black hole where matter does not fall into the black hole even if it is torn by strong gravity.

According to scientists’ calculations, the flares were orbiting about 244,000 kilometers of black holes once every 45 minutes. There is nothing that can manipulate such a powerful movement beyond a super-mass black hole.

Another way to detect a black hole is to hear a collision sound. When two black holes collide, they emit huge gravitational waves. The collision of a black hole occurs a long distance, so gravity waves are very blurry by the time they reach Earth.

Now, however, it is possible to detect these small waves through LIGO, a gravitational observatory in the United States, and VIRGO in Europe. These detected wavelengths are similar to the range of frequencies we can hear, so they can be converted to sound. In other words, you can not see the actual appearance of the black hole, but you can hear the sound.

Real-world observations with earth-sized virtual telescopes

But we may soon see a black hole that no one has ever seen. The Event Horizon Telescope (EHT) project team announced on Tuesday that it will hold a press conference in Brussels, Belgium at 3 pm (10 pm local time).

The main content of this press conference, which is broadcast live on the European Southern Observatory (ESO) website, is reported to be the first result of its efforts to capture the image of Sagittarius A * in the center of our galaxy.

EHT has begun work on observing the actual appearance of black holes from April 2017. Since then, we have been observing the international community by connecting radio telescopes around the world from Hawaii to the South Pole, with a period of about two weeks from March to April each year.

In order to observe a black hole like Sagittarius A *, you need a telescope 1000 times stronger than the Hubble Space Telescope. Instead of making such a giant telescope, it is the EHT project that created a globally sized virtual telescope that combines radio-telescopes scattered around the globe with huge lenses.

These connected telescopes are known to exert their ability to count stitches of baseball balls about 13,000 kilometers away. The EHT network is cooperated by 14 research institutions worldwide.

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Summary

One recent research team found 12 more small black holes within 3 light years from the center of our galaxy. Because black holes emit X-ray radiation only when they consume material, so many black holes remain undetectable.

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