The Meerkat of Science: Where the Light Stops
Previously, I wrote of what becomes of massive stars when they die. One of the products of a stellar behemoth’s death is a black hole, a point in space of infinite density, where gravity is so strong that not even light can escape.
Black holes are objects of tremendous fascination. They conjure up fearful thoughts, but may actually be fundamental to the formation and evolution of galaxies. Lurking at the heart of our galaxy is something we might call a monster, yet it may also be the reason we are here. With this post, let us consider the supermassive black hole.
From Stellar to Super
The mechanism by which black holes go from masses a few times that of our sun to several million times the mass of our sun is not yet understood (which is not to say we will never understand, science is after all a process of constant learning). There are a number of theories about how we have gotten from black holes formed from dying stars, to what we observe in our own (among many others) galaxy. Those theories are concerned with how massive stars – potentially more massive than possible in current conditions – formed and died in the early universe, when there might have been many massive stars collapsing into black holes, which subsequently absorbed mass from the material around them, and merged with one another. However this happened, something led to the formation of SMBHs, and they have wound up at the centre of many galaxies. There is certainly a relationship between SMBHs and galaxies, albeit one which is not fully understood as of yet.
What is known is that the scale of SMBHs is as staggering as it is terrifying. The one at the heart of the Milky Way is believed to have a mass of between 4.1 and 4.3 million solar masses, and that mass is squeezed into an area smaller than the orbit of Mercury. This particular black hole is also tiny when compared to others, in both size and mass.
The Titans of the Night
The first direct image of a supermassive black hole, found in the galactic core of Messier 87.[1][2] This view is somewhat from above, looking down on one of its galactic jets.[3] Rather than an accretion disc, it shows synchrotron radiation in the microwaverange (1.3 mm). This light was emitted by electronscaptured in the plasma vortex at the base of a jet.[4] Radiation of this wavelength does not reveal the thermal features thought to dominate the emissions of an accretion disc. The synchrotron radiation is shown after its interaction with the black hole’s photon sphere, which generates the ring. The dark central feature indicates the region where no pathexists between the event horizon and Earth. The edge of the photon sphere shows an asymmetry in brightness because of Doppler beaming. The image was released in 2019 by the Event Horizon Telescope Collaboration.
The black hole at the heart of Messier 87 is thought to have a mass of 6.5 billion solar masses, meaning it dwarfs our own galaxy’s black hole many times over. What’s even more incredible is that Messier 87 is itself relatively small! Ton 618 comes in at over 40 billion times the mass of our Sun, and it stretches to a diameter 40 times that of Neptune’s orbit around the Sun. In a further awe-inspiring twist, Ton 618 is not the biggest or most massive monster in the cosmos. Phoenix A is believed to have a mass of 100 billion solar masses, and is even larger than Ton 618 as well. These objects drive the activity within their host galaxies, absorbing material but also stirring up their environment, and thus driving star formation.
Black holes strike us as objects of fear, but there is so much more to them. In their own way, black holes are hauntingly beautiful, and they seem to be an integral to the formation of galaxies, and therefore us. Something to ponder!
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