Astronomers have used the Hobby-Eberly Telescope at The University of Texas at Austin’s McDonald Observatory to measure the mass of what may be the most massive black hole yet — 17 billion Suns — in galaxy NGC 1277. The unusual black hole makes up 14 percent of its galaxy’s mass, rather than the usual 0.1 percent. This galaxy and several more in the same study could change theories of how black holes and galaxies form and evolve.
NGC 1277 lies 220 million light-years away in the constellation Perseus. The galaxy is only ten percent the size and mass of our own Milky Way. Despite NGC 1277’s diminutive size, the black hole at its heart is more than 11 times as wide as Neptune’s orbit around the Sun.
“This is a really oddball galaxy,” said team member Karl Gebhardt of The University of Texas at Austin. “It’s almost all black hole. This could be the first object in a new class of galaxy-black hole systems.” Furthermore, the most massive black holes have been seen in giant blobby galaxies called “ellipticals,” but this one is seen in a relatively small lens-shaped galaxy (in astronomical jargon, a “lenticular galaxy”).
This diagram shows how the diamater of the 17-billion-solar-mass black hole in the heart of galaxy NGC 1277 compares with the orbit of Neptune around the Sun. The black hole is eleven times wider than Neptune’s orbit. Shown here in two dimensions, the “edge” of the black hole is actually a sphere. This boundary is called the “event horizon,” the point from beyond which, once crossed, neither matter nor light can return. Credit: D. Benningfield/K. Gebhardt/StarDate
ABSTRACT – Most massive galaxies have supermassive black holes at their centres, and the masses of the black holes are believed to correlate with properties of the host-galaxy bulge component. Several explanations have been proposed for the existence of these locally established empirical relationships, including the non-causal, statistical process of galaxy–galaxy merging, direct feedback between the black hole and its host galaxy, and galaxy–galaxy merging and the subsequent violent relaxation and dissipation. The empirical scaling relations are therefore important for distinguishing between various theoretical models of galaxy evolution and they furthermore form the basis for all black-hole mass measurements at large distances. Observations have shown that the mass of the black hole is typically 0.1 per cent of the mass of the stellar bulge of the galaxy. Until now, the galaxy with the largest known fraction of its mass in its central black hole (11 per cent) was the small galaxy NGC 4486B. Here we report observations of the stellar kinematics of NGC 1277, which is a compact, lenticular galaxy with a mass of 1.2 × 10^11 solar masses. From the data, we determine that the mass of the central black hole is 1.7 × 10^10 solar masses, or 59 per cent of its bulge mass. We also show observations of five other compact galaxies that have properties similar to NGC 1277 and therefore may also contain over-massive black holes. It is not yet known if these galaxies represent a tail of a distribution, or if disk-dominated galaxies fail to follow the usual black-hole mass scaling relations