Scientists find the reason behind black holes' light shows

Jun 21, 2006
Scientists find the reason behind black holes' light shows
Black holes grow by drawing gas from nearby objects such as stars into an accretion disk. Credit: NASA/CXC/M.Weiss

A team of astronomers led by the University of Michigan may know how black holes are lighting up the Universe. New data from NASA's Chandra X-ray Observatory show, for the first time, that powerful magnetic fields are the key to these brilliant and startling light shows.

It is estimated that up to half of the total radiation in the universe since the Big Bang comes from material falling towards super-massive black holes, including those powering quasars, the brightest known objects. For decades, scientists have struggled to understand how black holes, the darkest objects in the Universe, can generate such prodigious amounts of radiation.

New X-ray data from Chandra give the first clear explanation for what drives this process: magnetic fields. Chandra observed a black hole system in our galaxy, known as GRO J1655-40 (J1655, for short), where a black hole was pulling material from a companion star into a disk.

"By intergalactic standards, J1655 is in our backyard so we can use it as a scale model to understand how all black holes work, including the monsters found in quasars," said Jon Miller, assistant professor at U-M, whose paper on these results appears in this week's issue of the journal Nature.

If gas in a disk around a black hole loses energy, it will swirl toward the black hole, generating light along the way. Scientists have long thought that magnetic fields may drive this energy loss by generating friction in the gas and driving a wind from the disk that carries momentum outward, in an example of conservation of momentum.

By using Chandra spectra, that is, the amount of X-rays at different energies, Miller and his team showed that the speed and density of the wind from the disk in J1655 corresponded to computer simulation predictions for winds driven by magnetic fields. The spectral fingerprint also ruled out the two other major competing theories to magnetically-driven winds.

"In 1973, theorists came up with the idea that magnetic fields could drive the generation of light by black holes," said co-author John Raymond of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass. "Now, over 30 years later, we finally may have proof."

This deeper understanding of how black holes accrete matter also teaches astronomers about other properties of black holes, including how they grow.

"Just as a doctor wants to understand the causes of an illness and not merely the symptoms, astronomers try to understand what causes phenomena they see in the Universe," said co-author Danny Steeghs also of the CfA. "By understanding what makes material fall onto black holes and its energy released, we may also learn how it plunges onto other important objects."

In addition to accretion disks around black holes, magnetic fields may play an important role in disks detected around young Sun-like stars where planets are forming as well as ultra-dense objects called neutron stars.

Source: University of Michigan

Explore further: New mass map of a distant galaxy cluster is the most precise yet

add to favorites email to friend print save as pdf

Related Stories

Radio-burst discovery deepens astrophysics mystery

Jul 10, 2014

The discovery of a split-second burst of radio waves by scientists using the Arecibo radio telescope in Puerto Rico provides important new evidence of mysterious pulses that appear to come from deep in outer ...

Celebrating a decade of the Submillimeter Array

Jun 25, 2014

(Phys.org) —Ten years ago, eight antennas on the summit of Mauna Kea, Hawai'i, united to form a telescope unlike any other. Since then the Submillimeter Array (SMA) has examined the universe in unprecedented ...

Recommended for you

Satellite galaxies put astronomers in a spin

18 hours ago

An international team of researchers, led by astronomers at the Observatoire Astronomique de Strasbourg (CNRS/Université de Strasbourg), has studied 380 galaxies and shown that their small satellite galaxies almost always ...

Video: The diversity of habitable zones and the planets

18 hours ago

The field of exoplanets has rapidly expanded from the exclusivity of exoplanet detection to include exoplanet characterization. A key step towards this characterization is the determination of which planets occupy the Habitable ...

Ultra-deep astrophoto of the Antenna Galaxies

18 hours ago

You might think the image above of the famous Antenna Galaxies was taken by a large ground-based or even a space telescope. Think again. Amateur astronomer Rolf Wahl Olsen from New Zealand compiled a total ...

The most precise measurement of an alien world's size

20 hours ago

Thanks to NASA's Kepler and Spitzer Space Telescopes, scientists have made the most precise measurement ever of the radius of a planet outside our solar system. The size of the exoplanet, dubbed Kepler-93b, ...

User comments : 0