That is one mighty big lens
Blog vol 2. 51. That is one mighty big lens.
After 35 years of being an optometrist, the world of lenses and refraction of light are second nature. However, I am still continually amazed by the work being done with lenses of all different sorts.
In the news today, there was an article on the Supermassive Black Hole (SMBH) at the centre of our galaxy called Sagittarius A.
Back in 2019, a composite image put together by eight different telescopes around the world called the Event Horizon Telescope or EHT, showed the first actual photos of a black hole. Now the EHT has set its sights on the Sag A hole which is only 90 million miles in size but massive, four million times the mass of our Sun.
Black holes were first discovered by observing how light bends as it passes through the hole, with the huge mass of the hole bending any light that passes near, resulting in a lens affect, called a gravitational lens.
As early as 1912, when Einstein was formulating his theory of relativity, he reasoned that there must be black holes and that light would bend around them. Astronomers, in 1979, noticed that objects seen through these holes are either distorted or “doubled” in appearance.
Figure 1: An illustration of the image of a star behind a black hole getting split into two as seen by a telescope on the other side. Image credit: NASA Roman Space Telescope
The larger the celestial body you are looking at, the more doubling you will see. In the case of Sag A, the doubling is relatively small, due to its distance from us (26 000 light years away). To get a noticeable gravitational lens affect from this hole would require larger and more sensitive telescopes, and that is what the EHT group will be announcing on May 12. Stay tuned.
Just a small side note, for this is all mind blowing stuff, to get to Sag A travelling at Warp 9.975 (Star Trek convention) it would take 26 earth years just to get there, making you realize that any of the Sci-Fi books or movies we enjoy have the travellers go as fast as the speed of the plot (no more questions, anyone).
Just to put the wide cosmos into perspective.
til next week,
the good doctor
