Is it possible to orbit a black hole

At intermediate speeds you will orbit the black hole in a complicated pattern. There is exactly one launch speed that will put you on a circular orbit. This provides a stable vantage point if you start far from the black hole, but it is like playing Russian roulette if you start too close. The newly discovered black hole is about 1, light-years from our solar system in the star system HR On a human scale, a thousand light-years is an immense distance.

But in the grand scheme of the galaxy, which is more than , light-years across, HR is quite close, and it suggests the Milky Way is littered with black holes. Researchers have long estimated that the Milky Way is home to hundreds of millions of black holes, extremely dense objects whose gravitational fields are so intense, not even light can escape. But finding these dark objects has proven extremely difficult. But the majority of black holes in our galaxy are invisible, so the only way to find them is by observing their gravitational effects on surrounding objects.

Instead, they wanted to learn more about a pair of odd stars orbiting each other. The outer star, known as a Be star, is several times more massive than the sun and burns hotter and bluer. A separate group published a study that detailed a star system nicknamed LB-1 with a black hole about 70 times more massive than our sun. The work immediately raised eyebrows. But all studies of systems like HR , with multiple objects in close proximity, contend with a couple potential sources of error, El-Badry says.

The two stars can be identified only by the differing spectra of light that they emit. If HR 's inner star is such a mimic, researchers would have to recalculate the presumed black hole's mass.

Outside a black hole, however, everything is just dandy. A particular black hole will have a certain mass anywhere from a few times the mass of the sun for the smaller ones in the galaxy up to billions of times heavier for the true monsters roaming the cosmos , and orbiting the black hole is just like orbiting anything else of identical mass. Gravity is just gravity, and orbits are orbits.

Indeed, lots of stuff in the universe finds itself orbiting around black holes. Once these foolhardy adventurers get caught in the black hole's gravitational embrace, they begin the journey toward the end. As material falls toward the black hole, it tends to get squeezed into a razor-thin band known as an accretion disk.

That disk spins and spins, with heat, friction, and magnetic and electric forces energizing it, causing the material to glow brightly. In the case of the most massive black holes, the accretion disks around them glow so intensely that they get a new name: active galactic nuclei AGN , capable of outshining millions of individual galaxies.

In the accretion disk, individual bits of material rub up against other bits, draining them of rotational energy and driving them ever-inward to the gaping maw of the black hole's event horizon. But still, if it weren't for those frictional forces, the material would be able to orbit around the black hole in perpetuity, the same way that the planets can orbit around the sun for billions of years.

As you get closer to the black hole's center, though, you reach a certain point where all hopes of stability are dashed against the rocks of gravity.

Just outside the black hole, but before reaching the event horizon, the gravitational forces are so extreme that stable orbits become impossible. Nevertheless, without a sun, the incoming light would vanish, removing almost all the energy for life on Earth. But it turns out that there are a number of other energy sources for a planet orbiting a supermassive black hole. They are surrounded by a hot accretion disc of gas that is falling into the black hole.

The conditions in such a disc are just too extreme to support liquid water, but Schnittman says they can be made more comfortable by imagining that the accretion rate of the black hole is a tiny fraction of the observed value. The result is that any planet orbiting close to a supermassive black hole would do so in a cloud of hot gas.

Further out, the gas would be cooler. For it to be room temperature, the planet would have to orbit at distance that is times the gravitational radius of the black hole. So on the face of it, liquid water would be possible on such a planet. Whether life could evolve is trickier to assess. There is a small problem with the film in that the planet clearly orbits beyond the accretion disc, which Schnittman says would be dynamically unstable. A bigger problem is that if the accretion rate were lower, the density of the disc would also be lower, making it more difficult to radiate.

And without this radiation, the accretion disc would just heat up beyond the temperature of liquid water. So there is a paradox at the heart of this argument that ultimately invalidates it. All is not lost, however. There is another source of energy in the form of cosmic microwave background, the echo of the Big Bang. Astronomers have measured this radiation, and it has a temperature of just 2.

But this is where the magic of relativity comes into play.