Not seeing is believing when it comes to event horizon evidence

January 10, 2001

NASA's two Great Observatories, the Hubble Space Telescope and the Chandra X-ray Observatory, have independently provided what could be the best direct evidence yet for the existence of an event horizon, the defining feature of a black hole and one of the most bizarre astrophysical concepts in nature.

An event horizon is the theorized "one-way ticket" boundary around a black hole from which nothing, not even light, can escape. No object except for a black hole can have an event horizon, so evidence for its existence offers resounding proof of black holes in space.

By using data from Chandra and previous X-ray satellites, a team of researchers studied a dozen "X-ray novae," systems that contain a Sun-like star that orbits either a black hole or neutron star. By comparing the energy output from X-ray novae in their inactive, or dormant, phase, the Chandra team determined the black hole candidates emitted only one percent as much energy as neutron stars.

"It's a bit odd to say we've discovered something by seeing almost nothing, but, in essence, this is what we have done" said Michael Garcia of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass. "By detecting very little energy from these black hole candidates, we have new proof that event horizons exist."

If a collapsed star is a neutron star with a solid surface, energy must be released when infalling material strikes that surface. In contrast, if the accreting object is a black hole, only a small amount of energy can escape before it crosses the event horizon and vanishes forever.

"Seeing just this tiny amount of energy escape from the black hole sources is like sitting upstream watching water seemingly disappear over the edge," said Ramesh Narayan also of the Chandra team. "The most straightforward explanation for our observations is that these objects have event horizons and, therefore, are black holes."

Scientists using the Hubble Space Telescope took an entirely different approach. Joseph F. Dolan, of NASA's Goddard Space Flight Center, Greenbelt, Md., observed pulses of ultraviolet light from clumps of hot gas fade and then disappear as they swirled around a massive, compact object called Cygnus XR-1.

Hubble, measuring fluctuations in ultraviolet light from gas trapped in orbit and around the black hole found two examples of a so-called "dying pulse train," the rapidly decaying, precisely sequential lashes of light from a hot blob of gas spiraling into the black hole. Without an event horizon, the Blob of gas would have brightened as it crashed onto the surface of the accreting body. One event had six decaying pulses; the other had seven pulses. The results are consistent with what astronomers would expect to see if matter were really falling into a black hole, Dolan said.

Chandra researchers used the Advanced CCD Imaging Spectrometer for exposure times that vary roughly from 10,000 to 40,000 seconds per object. Hubble's high-speed photometer sampled light at the rate of 100,000 measurements per second, during three separate Hubble orbits, executed in June, July and August of 1992.

The Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, Inc., for NASA under contract with Goddard Space Flight Center. The Hubble Space Telescope is a cooperative project between NASA and the European Space Agency.

NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge, Mass. The Chandra work was also supported by funds from the National Science Foundation.

Images associated with the release are available at:

NASA/Marshall Space Flight Center News Center

Related Black Hole Articles from Brightsurf:

Black hole or no black hole: On the outcome of neutron star collisions
A new study lead by GSI scientists and international colleagues investigates black-hole formation in neutron star mergers.

The black hole always chirps twice: New clues deciphering the shape of black holes
A team of gravitational-wave scientists led by the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) reveal that when two black holes collide and merge, the remnant black hole 'chirps' not once, but multiple times, emitting gravitational waves--intense ripples in the fabric space and time--that inform us about its shape.

Wobbling shadow of the M87 black hole
New analysis from the Event Horizon Telescope (EHT) Collaboration reveals the behavior of the supermassive black hole in the center of the M87 galaxy across multiple years, indicating the crescent-like shadow feature appears to be wobbling.

How to have a blast like a black hole
Scientists at Osaka University have created magnetized-plasma conditions similar to those near a black hole using very intense laser pulses.

Black hole collision may have exploded with light
Astronomers have seen what appears to the first light ever detected from a black hole merger.

Black hole's heart still beating
The first confirmed heartbeat of a supermassive black hole is still going strong more than ten years after first being observed.

Black hole team discovers path to razor-sharp black hole images
A team of researchers have published new calculations that predict a striking and intricate substructure within black hole images from extreme gravitational light bending.

Planets around a black hole?
Theoreticians in two different fields defied the common knowledge that planets orbit stars like the Sun.

Black hole mergers: Cooking with gas
Gravitational wave detectors are finding black hole mergers in the universe at the rate of one per week.

Going against the flow around a supermassive black hole
At the center of a galaxy called NGC 1068, a supermassive black hole hides within a thick doughnut-shaped cloud of dust and gas.

Read More: Black Hole News and Black Hole Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.