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Galaxies


Black-Hole in M87 (2019, 2021 Update)

The large elliptical galaxy M87 is the dominant member of the Virgo Cluster. The variation in brightness and a jet shooting out from its center indicate that there is a black-hole at the center (Figure 05-02r1). The table in Figure 05-02r2 lists some of the characteristics of
M87, Black-Hole M87 Parameters M87 and its black-hole (also see "Space Fact"). An image of this black-hole is presented to the world by the Event Horizon Telescope(s) (EHT) in April, 2019. However, close examination reveals that the image is a shadow (actually a silhouette) formed by dark object against radio frequency background, and the whole picture is in false colors. It is stitched together with missing data filled in by some sort of educated guessing, a.k.a. "Bayesian Inference".

Figure 05-02r1 M87, Black-Hole [view large image]

Figure 05-02r2 M87 BH Parms

The following shows the theoretical base and processing involved in the imaging.
See "SgrA* Radio Image" for comparison.

By combining past observational data and educated guessed-work, a series of M87 black hole images have been constructed from 2009 to 2017 (Figure 05-20w). It shows lopsided blob of light swirling around the supermassive black hole at the centre of M87*. The bright spot
M87 BH, 2009-2017 moves around because the environment around the black hole changes on a scale of several weeks. Strong magnetic fields stir the accretion disk and produce hotter spots that then orbit the black hole. See "The first-ever image of a black hole is now a movie".

Figure 05-02w M87 Black Hole,
2009-2017 [view large image]

In 2018, a separate team reported evidence of a blob of hot gas circling SgrA*, the Milky Way’s central black hole, over the course of around 1 hour. Because M87* is more than 1,000 times the size of SgrA*, the dynamics around M87* take longer to unfold.

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