Just over two years ago, astronomers managed to capture the first image of Sagittarius A*, a supermassive black hole at the heart of the Milky Way, our galaxy.
Obtained by the Event Horizon Telescope (EHT), its bright disk surrounds the dark core, and represents the shadow of the event horizon.
Seeing such a monster, with a mass estimated at 4.3 million times that of the Sun and a diameter of around 23.5 million kilometers, in our cosmic “backyard”, we may wonder: Will it one day swallow the Earth?
And the answer is: “no”. Although it is indeed a giant, Sagittarius A* is currently not experiencing significant activity or intense accretion of matter. Despite this, it attracts and absorbs small amounts of gas and dust from the center of the galaxy.
It is the matter from these “snacks” that, heated and compressed, causes the black hole to emit radiation, mainly in the form of X-rays that astronomers detect.
Why doesn’t Sagittarius A* pose an immediate danger to Earth?
Although it is an impressive object and an overwhelming sight by human standards, Sagittarius A* is relatively small when compared to the immensity of the Milky Way, with its 100 thousand light years in length.
This means that this object is not “THE” black hole in the galaxy, although it is the central supermassive black hole, like others that exist in most large star systems. In the Milky Way, there are other black holes, both stellar and intermediate-mass.
Among the reasons why Sgr A* does not pose a risk to Earth is firstly its distance of approximately 26 thousand light years, which makes any interaction quite unlikely.
Despite having four million times the mass of the Sun, this size becomes insignificant compared to its distance from Earth. Even if it were placed in the place of the Sun, the Earth would remain intact.
Finally, the great fear of being sucked into the black hole is negligible in the case of Earth, because, although it is an extremely dense gravitational field, it decreases radically with distance.
The future of the galaxy and a scheduled threat: Andromeda
For Sagittarius A* to one day become an active galactic nucleus, which means a region with intense energy emissions, there needs to be much more material than today for it to “devour”.
This condition could occur, according to experts, but only in four billion years, when the Milky Way collides with Andromeda, our neighboring galaxy. Currently, the two are approaching each other at an impressive speed of 402 thousand km/h.
and should reorganize the materials around the massive black holes of both galaxies. This could activate Sgr A* as a galactic nucleus.
As incredible as it may seem, not even in this apocalyptic scenario, the Earth should be directly affectedbecause the stars are so far from each other that collisions will be very rare.
Either way, this is nothing we need to worry about, because at that point, the Earth will no longer be home to life as we currently know it.
And the fault will not be with the black hole or Andromeda, but with the person who currently supports life: the Sun. In about a billion years, it should gradually increase its brightness, until it evaporates the ocean and destroys our atmosphere.
