12/27/2022 – Ephemeris – 2022: We finally saw the black hole at the center of our galaxy

This is Bob Moler with Ephemeris for Tuesday, December 27th. Today the Sun will be up for 8 hours and 49 minutes, setting at 5:08, and it will rise tomorrow at 8:19. The Moon, 2 days before first quarter, will set at 10:30 this evening.

Besides the James Webb Space Telescope coming online in July, beginning, hopefully, twenty plus years of astronomical discovery, the Event Horizon Telescope Collaboration released an image of the black hole at the center of the Milky Way, 26,000 light years away In the direction of the constellation of Sagittarius. The collaboration, which consists of eight radio telescopes spread out from Hawai’i, to Europe, from Greenland to the South Pole, observed the black hole, dubbed Sagittarius A* (Pronounced Sagittarius A Star) for hours at the same time. The signals were recorded on disc drives, synchronized by atomic clocks, and then sent to a central processing center to create the image. The image was released last May of a fuzzy donut of the black hole and its accretion disk.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT –5 hours). They may be different for your location.

Addendum

Event Horizon Telescope component radio telescopes. Credits: © APEX, IRAM, G. Narayanan, J. McMahon, JCMT/JAC, S. Hostler, D. Harvey, ESO/C. Malin.

This is the image released May 12, 2022 by the Event Horizon Telescope Collaboration.

M87* size compared to Sagittarius A*. The size of a black hole is directly related to its mass. M87* has a mass of 6.4 billion times the Sun’s mass. It’s 55 million light years away. The mass of Sagittarius A* is only 4.2 million solar masses, and 26,000 light years away. Image credit: Event Horizon Telescope Collaboration.

Karl Jansky’s antenna reconstruction at the National Radio Astronomy Observatory, Green Bank, WV. He could rotate the antenna to find the direction of the source. He found that the source rotated with the sky, and the direction was the azimuth of the constellation of Sagittarius the archer. The source was later dubbed Sagittarius A. It is the brightest radio source in the sky. Click on the image to enlarge it. Credit: mine.

When radio astronomy was in its infancy, bright radio sources were labeled with the constellation they were in and a capital letter. Astronomers didn’t know what they really were. Karl Jansky’s discovery of the first celestial radio source in 1933 has been dubbed Sagittarius A, or Sgr A for short. He worked for Bell Labs, and was seeking the source of interference with wireless telephony transmissions. The source was from the general direction of the center of the galaxy, our Milky Way Galaxy, in the direction of the constellation of Sagittarius the archer.

04/09/2019 – Ephemeris – Tomorrow we may be able to see the supermassive black hole at the center of our galaxy

Ephemeris for Tuesday, April 9th. Today the Sun will be up for 13 hours and 10 minutes, setting at 8:20, and it will rise tomorrow at 7:07. The Moon, 3 days before first quarter, will set at 1:00 tomorrow morning.

There’s a great bit of excitement in astronomical circles for tomorrow’s release of an image of the event horizon of the supermassive black hole at the center of our Milky Way Galaxy, 27 thousand light years away. The black hole is designated Sagittarius A*. Pronounced Sagittarius A Star.  Sagittarius is the constellation it’s located in, capital A for the first radio source found in that constellation and an asterisk, pronounced Star. Eight highly accurate radio telescopes located from Greenland to the south pole, from Hawaii to Europe simultaneously record signals and record them to computer disks. The data are processed together to produce an image with the resolving power of a telescope the diameter of the Earth. The event horizon is smaller than our solar system.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Event Horizon Telescope component radio telescopes. Credits: © APEX, IRAM, G. Narayanan, J. McMahon, JCMT/JAC, S. Hostler, D. Harvey, ESO/C. Malin

For more information see this news article from the AAAS Science Magazine:  https://www.sciencemag.org/news/2019/04/here-s-what-scientists-think-black-hole-looks.

For a non-technical explanation of black holes and the event horizon check this out:  https://www.sciencealert.com/black-holes.