101 must-see cosmic objects: M87
M87 is another elliptical Messier galaxy in the Virgo cluster, 55 million light-years distant and some 120,000 light-years wide. It lies about 3½° northwest of Rho Virginis. But M87 surpasses M84 and M86 in terms of mass: it has at least a trillion stars totaling a mass of 2.7 trillion suns. This makes it one of the largest, most massive, and brightest galaxies in our local universe.
Charles Messier discovered M87 on March 18, 1781 – the same night he found M84 and M86 – and one can only wonder what went through his mind when he spotted these three comet-like objects in the same area of the sky. At magnitude 8.6, M87 is slightly brighter than the other two and between them in size.
M87 is most likely the visible remnant of an extragalactic merger between two galaxies. This combined cosmic powerhouse now has a furious jet of matter erupting from its core. Heber Curtis of Lick Observatory first noticed this “curious straight ray” in 1918 on photographic plates. The jet is a very powerful central radio source and is powered by a 6.5 billion solar mass black hole – one of the largest known. In 2017, astronomers used an international network of radio telescopes called the Event Horizon Telescope to zoom into M87’s core and capture the first image of a black hole and its shadow, which was released in April 2019.
The first visual sighting of M87’s 5,000 light-year jet was made by Otto Struve through the Mount Wilson 100-inch Telescope. It was thought to be beyond the reach of amateur astronomers until the late Barbara Wilson first saw it through her 20-inch reflector at the 1991 Texas Star Party. Otherwise, the galaxy is pretty typical for an elliptical. Namely, it resembles an unresolved globular cluster or the head of a comet that is just beginning to shine – one with a bright spherical shell that gradually condenses inward. An elliptical dimmer, 11th magnitude NGC 4478, lies only 10′ southwest of M87; low to high magnifications are needed to see well.
Be sure to explore the full list of 101 cosmic objects you must see on Astronomy. New entries will be added weekly throughout 2022.
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