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.

08/25/2022 – Ephemeris – Looking to the heart of the Milky Way

This is Bob Moler with Ephemeris for Thursday, August 25th. Today the Sun will be up for 13 hours and 34 minutes, setting at 8:31, and it will rise tomorrow at 6:58. The Moon, 2 days before new, will rise at 5:52 tomorrow morning.

Behind a dark cloud in the Milky Way, just above the spout of the teapot asterism or informal constellation that we see of the zodiacal constellation of Sagittarius, lies the very center of our Milky Way Galaxy. It cannot be seen in visible light, but can be detected with radio waves and infrared light that can penetrate the clouds of dust between. In 1932 Bell Laboratory physicist and radio engineer, Karl Jansky, discovered a source of radio static that came from that region of sky. It was subsequently given the designation Sagittarius A. It turns out that within that source there is an object called Sagittarius A* (Pronounced Sagittarius A Star), invisible in the near infrared, but with the mass of four million suns. It was recently imaged as the black hole at the center of our galaxy.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

Our place in the Milky Way. Note that we appear to be in a barred spiral galaxy. The arms are numbered and named. 3kpc is the 3 kiloparsec arm. 3kpc = 9,780 light years. The Sun is about 27,000 light years from the center. Credit NASA and Wikimedia Commons, via EarthSky.org

Location of the center of the Milky Way and the Teapot of Sagittarius. It’s behind that dark cloud.

An image from the Chandra X-ray Telescope of the center of the Milky Way. SGR A or Sagittarius A is a radio source. SGR A*, pronounced Sagittarius A Star, is the 4 million solar mass black hole in the center of the Milky Way Galaxy. Credit NASA.

M87* size compared to Sagittarius A*. The size of a black hole is directly related to its mass. The asterisk * is pronounced “Star”. Credit: Event Horizon Telescope Collaboration.

The black hole images were reconstructed from data from 8 sub millimeter radio telescopes and arrays of the Event Horizon Telescope Collaboration. The telescopes were located from Greenland to the South Pole and From Hawai’i to Europe. The data from the telescopes, observing the black holes simultaneously, were combined to act like a single telescope with the diameter of the Earth in order to resolve the black holes.

05/16/2022 – Ephemeris – A peek at the monster at the center of the Milky Way

This is Ephemeris for Tuesday, May 17th. Today the Sun will be up for 14 hours and 54 minutes, setting at 9:06, and it will rise tomorrow at 6:11. The Moon, 1 day past full, will rise at 11:33 this evening.

This past Thursday the Event Horizon Telescope Collaboration released an image of the black hole at the center of the Milky Way, 27,000 light years away In the direction of the constellation of Sagittarius, which is currently visible low in the south in the morning hours. How they got the image is too complex to explain here, not that I know how they did it. It appears as a fuzzy donut with three bright areas around the edges. The dark center is the shadow of the black hole, because no light can escape it, plus it severely bends any light that comes near it. The light we’re seeing it is in millimeter microwaves, rather than the nanometer wavelengths of visible light. Part of the fuzziness of the image is due to the motion of the material surrounding it.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

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. The asterisk * is pronounced “Star”. Credit: Event Horizon Telescope Collaboration.

It looks like I’ll have to update my presentation, What Lurks in the Center of the Milky Way? Astronomers were already sure it was a black hole, but the donut appearance of Sagittarius A* clinched it.

Off topic

Last night’s (May 15/16) lunar eclipse, shortly after the partial eclipse began behind clouds. I often checked until totality, but it seems to get worse. I may have missed brief clearings. When I got up, it was clear… Figures.

05/03/2019 – Ephemeris – How do you take a picture of a black hole? Find out tonight.

Ephemeris for Friday, May 3rd. Today the Sun will be up for 14 hours and 19 minutes, setting at 8:49, and it will rise tomorrow at 6:28. The Moon, 1 day before new, will rise at 6:44 tomorrow morning.

Nearly a month ago the world was presented with the news and the image that the Earth spanning Event Horizon Telescope captured a picture of a black hole 55 million light years away. Tonight NMC Professor Jerry Dobek will explain how it was done at tonight’s meeting of the Grand Traverse Astronomical Society at Northwestern Michigan College’s Rogers Observatory starting at 8 p.m. He will explain how simultaneous observations of the black hole by 8 separate sub-millimeter radio telescopes that were separately recorded on disk.  The disks were brought and processed together to produce the image. Starting at 9 p.m. if it’s clear there will be a star party featuring the brighter wonders of the darkening sky.

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

Addendum

The first image of the black hole in M87. Credit Event Horizon Telescope.

04/10/2019 – Ephemeris Extra – Event Horizon Telescope reveals the black hole in galaxy M87

At 10 a.m. I found the live feed from the National Science Foundation presenting the results of the Event Horizon Telescope.  It was one of four simultaneous presentations around the world at that hour.  The buzz beforehand was that they would present the image of the black hole in our galaxy Sagittarius A*.  It was not.  The image presented was of the black hole in the galaxy M87, some 55 million light years away.  It turns out that The black hole in M87 is easier to image.  Our black hole appears to be too variable in brightness for this first attempt.  The M87 black hole has a mass of 6.5 billion times that of our sun.  Our black hole has a mass of about 3 million suns.  The size of a black hole’s event horizon is proportional to its mass.  So the M87 black hole is about 2,000 times larger than our black hole, but about 2,000 times farther away.  So they would appear to be the same size on the sky.

The first image of the black hole in M87. Credit Event Horizon Telescope/Katie Bouman*.

The round spot in the center is not a shadow, but the event horizon itself.  It is black because no light can escape it.  The ring around it is the accretion disc of material spiraling in to the black hole.  I believe the disc is close to perpendicular to our line of sight, but not close.  The brightest part near the bottom is material that is approaching us, while the dimmer part above is material flowing away.

There are many articles and a video of the news conference by pointing you favorite search engine to M87 black hole.

About M87:  More formally Messier 87, is a galaxy near the center of a vast cluster of galaxies about 55 million light years from us.  Charles Messier found it in 1781 while searching for comets.  He recorded it as object number 87 on his list of fuzzy objects that didn’t move and thus were not a comet.   We amateur astronomers use his Messier Catalog to view these, what we call, deep sky objects.  M87 is a giant elliptical galaxy that was also a radio source called Virgo A.

The Wikipedia article Messier 87 has already been updated to include the results presented of earlier today.

* Update:  Dr. Katherine Bouman AKA Katie Bouman lead the team that created the algorithm that processed the data from the eight radio telescopes of the Event Horizon Telescope.  Her ideas on how to perform this feat of mathematical and computer wizardry were presented in a TED Talk in 2016.

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.