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First Look at a Black Hole

This article appeared in the 5/10/19 edition of the Davis Enterprise.

First Look at a Black Hole

First image of the event horizon of a black hole, M87, captured by the Event Horizon Telescope. Image courtesy of the Event Horizon Telescope Collaboration

First Look at a Black Hole 

 

By Vinita Domier

Davis Astronomy Club

 

 

On April 10, we finally got to see what a black hole really looks like with the release of the first ever photograph of a supermassive black hole at the center of M87, a supergiant elliptical galaxy in the Virgo constellation. Prior to this breakthrough, the presence of black holes was only indirectly observed by their gravitational effects on the surrounding space, matter, and radiation, and all black hole images in the media were either artist renditions or computer simulations. 

This momentous feat was accomplished by utilizing a tried and true technique known as very long baseline interferometry used in high resolution radio astronomy where multiple telescopes observe the same object simultaneously, albeit with a phase delay due to their differing distances to the object. The radio signals from each telescope are then computationally added together to form an image that is equivalent to one obtained by a telescope whose diameter is comparable to the maximum distance between the telescopes.

To observe black holes, one earth-sized virtual radio telescope known as the Event Horizon Telescope (EHT) was created by utilizing eight existing ground-based radio telescopes located at high altitudes in six locations in four continents - Hawaii, Arizona, Mexico, Spain, Chile, and Antarctica. The synchronized data collected at each site was then compiled by supercomputer correlators located in Massachusetts and Germany using sophisticated algorithms.

A black hole is a dark region in space from where even electromagnetic radiation cannot escape due to immense gravity as the escape velocity exceeds 300,000 km/sec (speed of light in a vacuum). The center of this spherical infinitely dense region is known as the singularity, and the edge of this region where escape velocity equals the speed of light is known as the event horizon. The darkness extends beyond the event horizon, however, due to the shadow of the black hole projected onto the line-of-sight of an observer by the gravitational bending of some of the light rays from the bright ring-shaped accretion disk that surrounds it.

The supermassive black hole in the center of the M87 galaxy was directly observed by EHT in 2017 at a radio frequency of 230 GHz (1.3 mm wavelength). The data obtained was algorithmically integrated to produce the historic false color visual image of a black hole that is the size of our solar system but is 6.5 million times more massive than our sun and is 55 million light years distant from earth. The EHT image shows a circular dark shadow in the center encircled by a glowing ring. The size of the event horizon is under 40 million km across and is 2.5 times smaller than the central dark hole shadow.

Please join the Davis Astronomy Club on Saturday, May 11 starting at 7:30pm at the Explorit Science Center (3141 5thStreet, Davis) for the discussion on Event Horizon Telescope and black holes. Everyone is invited to the free meeting indoors, followed by a star party outdoors where will observe the first quarter moon and M87 in the Virgo constellation. 

 

 

Explorit's coming events:



·      NEW THIS SUMMER-Check out the new evening teen camp July 8 – 12 "The Stars and Our Night Sky" for ages 12-16 yrs. Learn about the stars, planets, moons, black holes and other phenomenon in the sky. Explore the use of various telescopes and learn to identify stars and planets.

 

 

 

  • Visit Explorit's latest exhibition, Earth Explorations. Explorit'sExploration Galleryis open to the public every Wednesday, Friday, Saturday and Sunday, 1:00-5:00 p.m.  Admission is $5.00 per person; Explorit members, teachers and children 2 and under are free.

 

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Explorit Science Center is located at 3141 5th St. For more information call (530) 756-0191 or visit http://www.explorit.org, or "like" us on Facebook at www.facebook.com/explorit.fb.

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