If you are reading this, no doubt you have seen the incredible first ever image of a black hole, published just last week - an amazing feat that has been considered impossible until now. The paradox of a black hole is that its gravity is so powerful that not even light captured by it can escape, making it in effect invisible.
But before this image was made, how did astronomers know that black holes actually existed? The black hole in the historic image published last week is located in the very centre of a large galaxy known as M87. Based on various types of evidence, such as the movements of stars and very high luminosity in the vicinity of the galactic centre, indicating very powerful gravitational and magnetic forces at work, it is suspected that all large galaxies host such a super-massive black hole at their centre.
Have a look at this 2013 image of the centre of galaxy NGC 1433, produced by combining data from the ALMA and Hubble Telescopes – you can see the matter spiralling inwards toward a bright white point in the very middle, which appears to be a strong outflow of matter about 150 light years long, most likely connected with the central black hole
For me, this strong outflow is one of the most dramatic features created by a black hole – it often appears as very focussed twin jets shooting out in opposite directions perpendicular to the plane of the galactic disc, as you can see in this combined X-ray, microwave and visible wavelength image of the galaxy known as Centaurus A.
The blue areas show X-ray emission from jets being ejected at half the speed of light from the bright centre of the galaxy, and at the end of each jet you can see an orange lobe which is the radio emission from the shock-wave created when the high-speed jets collide with the surrounding gas.
Galaxy M87 boasts an impressive jet 1500 light years in length shooting out from its central black hole – it’s not visible in the image published last week but you can see it in this image from the Chandra X-ray telescope, published just last week.
Researchers studying this data from Chandra aim to gain a better understanding of how a black hole is able to produce such powerful jets – it’s clear that they are streams of particles that have been accelerated to extremely high energies, but there are still many questions to be answered about the processes going on within a virtually invisible black hole that are able to produce such a spectacular visible effect.
https://www.eso.org/public/news/eso1907/ ‘Astronomers capture first image of a black hole’
http://chandra.si.edu/photo/2019/black_hole/ (M 87)
https://www.eso.org/public/images/eso1344a/ (NGC 1433)
https://www.eso.org/public/news/eso0903/ (Centaurus A)
https://www.ibtimes.com/jets-supermassive-black-holes-help-regulate-galactic-formation-star-formation-activity-1428662 (NGC 1433)
Image Credits:
- ALMA (ESO/NAOJ/NRAO)/NASA/ESA/F. Combes
- ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray)
- NASA/CXC/Villanova University/J. Neilsen