![]() The remaining trickle of gas that does accrete onto the SMBH is not enough to allow it to grow to more than 10 11 solar masses in the age of the universe. Modeling this process, Inayoshi and Haiman demonstrate that at such high rates, the majority of the gas instead gets stuck in the disk, causing star formation at radii of tens to hundreds of light-years and never getting close enough to fuel the SMBH. Growing an SMBH that’s more massive than 10 10 solar masses requires gas to be quickly funneled from the outer regions of the galaxy (hundreds of light-years out), through the large accretion disk that surrounds the black hole, and into the nuclear region (light-year scales): the gas must be brought in at rates as high as 1,000 solar masses per year. So why don’t we see any giants larger than around 10 billion solar masses, regardless of where we look? Two astronomers from Columbia University, Kohei Inayoshi (Simons Fellow) and Zoltán Haiman, suggest that there is a limiting mass for SMBHs that’s set by small-scale physical processes, rather than large processes like galaxy evolution, star formation history, or background cosmology. Though accretion rates start out very high at large radius, they drop to just a few solar masses per year at small radii, because much of the gas is lost to star formation in the disk. radius in a star-forming accretion disk, for several different values of black-hole mass. A black hole time machine could allow an astronaut to find out what the world will be like in the future.Accretion rate (solid) and star formation rate (dashed) vs. An astronaut could take a short trip near a black hole and return to Earth after years, decades, or even centuries had passed there. Someday humans might be able to use black holes to time travel forward. When the spacewalker returned to the spaceship after an hour-long spacewalk, years would have passed for those aboard the spacecraft. But if anyone back on the spacecraft could observe the astronaut’s watch from far away, they’d see its hands slow down as the spacewalker got closer to the black hole. If an astronaut left his spacecraft to explore a black hole up close, he’d see the hands on his watch ticking at normal speed. The intense gravity near a black hole makes time behave in strange ways. ![]() (A* is scientist-code for “A-star.”) The most common type of black holes, stellar black holes, are only up to 20 times more massive than our sun. This is the kind of black hole that’s at the center of our galaxy, the Milky Way it’s called Sagittarius A*. Lower-mass black holes are expected to evaporate even faster for example, a black hole of mass 1 TeV/c 2 would take less than 10 88. They’re up to one million times more massive than our sun. A black hole with the mass of a car would have a diameter of about 10 24 m and take a nanosecond to evaporate, during which time it would briefly have a luminosity of more than 200 times that of the Sun. Supermassive black holes are the largest type of black hole. Though astronomers can’t see black holes, they know they’re there by the effect they have on objects that get too close. Many of these exotic giant galaxies with so-called supermassive black holes at the centers, with masses a billion times that of the sun. ![]() That’s why we can’t see black holes in space-they've gobbled up all the light. A new generation of power radio telescope arrays is in the early stages of generating pictures of 10s of millions of radio sources in the sky. This includes light, the fastest thing in the universe. Nothing can move fast enough to escape a black hole’s gravity. ![]() The giant star is eventually squashed into a supersmall dot you can’t see.Ī black hole’s gravity, or attractive force, is so strong that it pulls in anything that gets too close. This causes an explosion called a supernova. The star implodes, and its center collapses under its own weight. Most black holes, regardless of their size, are born when a giant star runs out of energy. At the center of most galaxies is one of the strangest and deadliest things in the universe: a black hole. ![]()
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