LARGEST VOID IN THE UNIVERSE
To be ‘under one’s nose’ at a distance of 581 million lightyears, you can only really be a quasar. The closest to us of these rather alarming objects is within a galaxy designated Markarian 231, which was discovered in 1969 in the constellation of Ursa Major. This year astronomers using the Hubble Space Telescope revealed that the centre of this Seyfert galaxy is powered by not one but two black holes, weighing in at 150 million and four million solar masses respectively. The asymmetric nature of Markarian 231, along with long tails of young stars, points to a probable merger with a smaller galaxy, and it is likely that the smaller black hole came from this. With an orbital period of just 1.2 years, these two monsters will collide and merge in the next few hundred thousand years.
Above: Curiosity’s landing site, Gale Crater, as imaged by India’s Mars Orbiter Mission; left: the orbiter also snapped this full disc image of Mars on its arrival
Markarian 231, 581 lightyears distant and the home of our
nearest quasar When Edwin Hubble discovered the whole ‘rest of the Universe’, it was too soon for conspiracy theorists to strike. Imagine, then, if we only discovered that there were other galaxies in the 1960s? That’s exactly what would have happened if we lived in the centre of the Boötes Void, which used to be the largest known ‘void’ in the Universe. But announced this year was the analysis of a ‘supervoid’ 1.8 billion lightyears across, dwarfing the Boötes Void. Of course ‘void’ is a misnomer: it is really a region of space that is ‘underdense’ compared to everywhere else. In fact, this region is missing some 10,000 galaxies. This record is likely to be broken in due course, but only for a limited number of times. The Universe is only large enough to contain a handful of voids of this scale.