Scientists took pictures of two black holes and only one was washed out.

category:Internet
 Scientists took pictures of two black holes and only one was washed out.


On the evening of April 10, the first black hole photograph of human beings was released jointly around the world. The protagonist is more than 50 million light-years away, in the middle of the distant M87 galaxy, about 6.5 billion times the mass of the sun.

In fact, in April 2017, the eight EHT telescopes selected two targets, and the other one is closer to the Earth, which is the central black hole of our galaxy. So why didnt you see a picture of a black hole in the center of the Milky Way Galaxy this time?

Yuan Feng, deputy director of the Shanghai Observatory of the Chinese Academy of Sciences, told Peng Mei News (www.thepaper.cn) that there were more technical difficulties in taking photos of the galaxys central black hole. Because the Earth is in the silver disk, the black hole in the observation center needs to pass through many stars, dust and gas, which causes strong scattering effect and makes imaging more difficult.

Yuan Feng, who participated in the EHT projects theoretical team, said that the actual black hole photographs were almost identical to the theoretical calculations, which was another victory of Einsteins general relativity theory. Because of this, black hole photographs are very similar to the image of black hole in the science fiction movie Star Crossing, which is a shadow in the middle and a bright ring outside. After all, the scientific adviser to Star Trek is Kip Thorn, a Nobel Laureate in physics. The body of the black hole is hidden in the shadow, and the luminous part is the gas accumulated around the black hole.

The biggest difference between M87 black hole and Star Crossing black hole is that the latter has a thin accretion disk, while M87 black hole has a thick accretion disk.

So what kind of light does the halo around a black hole emit? Specifically, eight radio telescopes around the world collected 1.3 millimetres of light from turbulent accretion gases.

This kind of light has longer wavelength than the visible light we are familiar with. In fact, there is no color distinction. Scientists can only sense the intensity of the signal. The red in the photo is the effect of post-processing, while Star Crossing chose bright yellow.

Black holes in Star Crossing are presented in bright yellow.

Why choose this band? Its a big deal. On the one hand, the accretion gas of black hole radiates strongly in this band. On the other hand, this band has a relatively short wavelength in radio waves.

The resolution of photographs is related to two main factors. The shorter the observed wavelength, the larger the aperture of the telescope, and the clearer the picture. This time, scientists used Very Long Baseline Interferometry (VLBI) to build a network of eight telescopes with the same aperture as the Earths diameter. So why not use shorter wavelengths of infrared, or even visible light? Yuanfeng explained that in these bands, the Interferometry Technology is not so mature that it can not achieve the purpose of taking pictures of black holes. It can be said that the 1.3mm wavelength is at a technical balance point. From the source, the light is generated by synchrotron radiation on the accretion disk of a black hole. When the gas reaches the accretion disk, the temperature becomes very high, and the particles velocity reaches the relativistic velocity. In the magnetic field generated by the accretion disk, relativistic particle motion emits synchrotron radiation. Source: Wang Fengzhi _NT2541

The resolution of photographs is related to two main factors. The shorter the observed wavelength, the larger the aperture of the telescope, and the clearer the picture. This time, scientists used Very Long Baseline Interferometry (VLBI) to build a network of eight telescopes with the same aperture as the Earths diameter. So why not use shorter wavelengths of infrared, or even visible light? Yuanfeng explained that in these bands, the Interferometry Technology is not so mature that it can not achieve the purpose of taking pictures of black holes. It can be said that the 1.3mm wavelength is at a technical balance point.

From the source, the light is generated by synchrotron radiation on the accretion disk of a black hole. When the gas reaches the accretion disk, the temperature becomes very high, and the particles velocity reaches the relativistic velocity. In the magnetic field generated by the accretion disk, relativistic particle motion emits synchrotron radiation.