The mantra among real estate brokers is “location, location, location…” This holds true for neighborhoods in our galaxy too.
One neighborhood to avoid is in the vicinity of the supermassive black hole — inside a very strong radio source known as Sagittarius A* — at the hub of the Milky Way.
A new analysis of recent observations finds evidence for a protoplanetary disk around a red dwarf star plunging in the direction of the black hole. Ruth Murray-Clay and Avi Loeb of the Harvard-Smithsonian Center for Astrophysics did the theoretical work. Stefan Gillessen of the Max-Planck-Institute for Extraterrestrial Physics made the observations using the European Southern Observatory’s Very Large Telescope.
The red dwarf star will make its closest approach in the summer of 2013, hurtling only 270 billion miles from black hole. (Or roughly 54 solar system diameters, as measured from the furthest edge of the Kuiper belt.) It won’t get sucked into the black hole, but it will be flung back along its elliptical orbit out to a distance of a little more than 1/10 light-years.
But the damage is already happening. The protoplanetary disk is disintegrating under the black hole’s tidal pull — stretching the disk like taffy. Add to that a withering blast of ultraviolet radiation from the black hole that is heating and driving off material in the disk.
Astronomers haven’t seen the dim red star at the center of the disk, but infer its presence from a telltale 100 billion-mile diameter cloud of glowing gas created by the disintegration of the disk.
Superficially, the infalling star would resemble a comet with a teardrop shaped head of plasma and long trailing tail (shown in the picture at top of page).
Similar “distressed” protoplanetary disks can be found in the heart of the Orion nebula, where they are being blow-torched by a tsunami of radiation from the hottest central stars.
How did the doomed star end up on such a Kamikaze path? The farthest point of its orbit take its back to its nesting ground, a 3 million-year-old ring of young stars orbiting the black hole. The hapless star’s orbit is in the plane of this ring.
The star was likely formed in the stellar ring and later thrown into its highly eccentric orbit though a close encounter with one or more stars in the ring. The stars exchanged momentum and the red dwarf was tossed onto a new, deadly trajectory.
If this event happens once every few hundred thousand years, it would agree with estimates for how much mass a quiescent black hole may gobble up over time. It might also show us a mechanism for explaining how active black holes that spew out deathly beams of plasma are fueled by a cascade of comets, asteroids and dust.
In the early 1990s, NASA’s Hubble Space Telescope discovered a ring of blue stars encircling the black hole ring in the center of the neighboring Andromeda galaxy. There is also an outer elliptical ring of older stars. Therefore, black hole stellar rings appear to be common throughout the universe.
Most intriguing is the idea that planets can form in the stellar ring around a supermassive black hole. Could the planets be stable long enough for intelligent life to evolve in such neighborhoods? This is very hard to predict because we don’t know how long the stellar ring will remain intact. What’s more, dynamics within the densely pack ring might tear apart planetary systems.
Imagine the predicament of alien astronomers living in such a place. They would have no doubt there was indeed a center to their universe — the black hole. They would watch in amazement as disrupted star systems fell toward the black hole and were shredded apart.
A religion might develop around the idea that a true end-of time “vacuum hose” could be seen in the sky. To the hypothetical aliens, might this be considered a gateway to Heaven… or Hell?
Image credit: S Gillessen/ESO, NASA