A new estimate of the amount of dark matter in the Great Magellanic Cloud suggests that its mass is twice as large as previously thought. The attraction of the Milky Way should therefore be so strong that the two galaxies are expected to collide in two billion years. The quasar of our galaxy should then reignite.
In recent decades, telescopes have produced numerous images of interacting galaxies, deformed by tidal forces, resulting from close encounters and sometimes even causing stars to collide. Dozens of spectacular photographs from the Hubble telescope show it and sometimes, not only two but three or even four galaxies are caught in the act of fusion, as can be seen in the images taken by the Spitzer telescope.
These fusions make galaxies grow by bringing stars and also gas clouds that will collapse to make new ones, under the effect of the resulting shock waves in the interstellar medium. This baryonic material can also feed the accretion disks of supermassive black holes dormant, or almost, in the heart of galaxies, and cause the birth of what is called the active nuclei of galaxies.
These grandiose cosmic events occur only between large galaxies but also when small dwarf galaxies are captured by their bigger sisters, such as the Milky Way and Andromeda. Traces of these past collisions are found in these two spiral galaxies, as the Gaia mission recently showed in the case of our galaxy.
In approximately four billion years, Andromeda and the Milky Way will collide themselves. The gravitational attraction between these giants is, indeed, too strong for the expansion of space that distances us from other galaxies to be operative. But, according to calculations made in the framework of the numerical simulations of the Eagle project (Evolution and Assembly of Galaxies and their Environments) which has already been used to model on computers the formation of large structures in the observable Universe in a cosmological volume of more than 300 million light-years in size, another colossal collision should occur before.
Indeed, as explained by a group of astrophysicists from the Institute of Computational Cosmology, Durham University (UK) in an article published in the Monthly Notices of the Royal Astronomical Society (free access on arXiv), the Great Magellanic Cloud is expected to collide with the Milky Way within about two billion years.
The status of the Great Magellanic Cloud has never been very clear, except that it is the brightest dwarf galaxy, close to the Milky Way at a distance of about 163,000 light-years. It has often been debated that it was orbiting the Milky Way as a satellite … It now seems that its dark matter content is more important than we thought, so that its mass would be in double the amount previously estimated. If this is the case, then it is undergoing a stronger attraction of our Galaxy. It is for this reason that the calculations carried out concerning its future trajectory point today to a collision with the Milky Way, a collision that will lead to a merger.
Researchers at the Institute of Computational Cosmology go even further with their work. The contribution of normal matter and the disturbances caused by the event will transform our supermassive black hole into a quasar and lead the already compact object, by the important process of accretion of matter which will then occur, to increase its mass tenfold which should probably reach 400 million solar masses.
The Solar System and the Earth should not be really affected by the intense radiation of the quaking of the Milky Way quasar. But, although unlikely, it is possible that the gravitational forces involved in the fusion of the Great Magellanic Cloud with the Galaxy lead to the ejection into the intergalactic environment of our Solar System within a current of stars torn off. By then, in any case, the oceans of the Earth will have begun to boil because of the growth of the brightness of the Sun.