Now, in a study in the journal Nature, astronomers at Columbia University provide additional evidence that a pair of closely orbiting black holes is causing the rhythmic flashes of light coming from quasar PG 1302-102.

Based on calculations of the pair’s mass–together, and relative to each other–the researchers go on to predict a smashup 100,000 years from now, an impossibly long time to humans but the blink of an eye to a star or black hole. Spiraling together 3.5 billion light-years away, deep in the Virgo constellation, the pair is separated by a mere light-week. By contrast, the closest previously confirmed black hole pair is separated by 20 light-years.

“This is the closest we’ve come to observing two black holes on their way to a massive collision,” said the study’s senior author, Zoltan Haiman, an astronomer at Columbia. “Watching this process reach its culmination can tell us whether black holes and galaxies grow at the same rate, and ultimately test a fundamental property of space-time: its ability to carry vibrations called gravitational waves, produced in the last, most violent, stage of the merger.”

At the center of most giant galaxies, including our own Milky Way, lies a supermassive black hole so dense that not even light can escape. Over time, black holes grow bigger–millions to billions times more massive than the sun–by gobbling up stars, galaxies and even other black holes.

A supermassive black hole about to cannibalize its own can be detected by the mysterious flickering of a quasar–the beacon of light produced by black holes as they burn through gas and dust swirling around them. Normally, quasars brighten and dim randomly, but when two black holes are on the verge of uniting, the quasar appears to flicker at regular intervals, like a light bulb on timer.

Recently, a team led by Matthew Graham, a computational astronomer at the California Institute of Technology, designed an algorithm to pick out repeating light signals from 247,000 quasars monitored by telescopes in Arizona and Australia. Of the 20 pairs of black hole candidates discovered, they focused on the most compelling bright quasar– PG 1302-102. In a January study in Nature, they showed that PG 1302-102 appeared to brighten by 14 percent every five years, indicating the pair was less than a tenth of a light-year apart.

Intrigued, Haiman and his colleagues wondered if they could build a theoretical model to explain the repeating signal. If the black holes were as close as predicted, one had to be circling a much larger counterpart at nearly a tenth of the speed of light, they hypothesized. At that speed, the smaller black hole would appear to brighten as it approached Earth’s line of sight under the relativistic Doppler beaming effect.

If correct, they predicted they would find a five-year cycle in the quasar’s ultraviolet emissions–only two-and-a-half times more variable in its intensity. Analyzing UV observations collected by NASA’s Hubble and GALEX space telescopes they found exactly that.

Previous explanations for the repeating signal include a warp in the debris disks orbiting the black holes, a wobble in the axis of one black hole and a lopsided debris disk formed as one black hole draws material off the other–all creating the impression of a periodic flicker from Earth.

The new study also offers a new technique for investigating other converging black holes, the researchers said. By estimating the combined and relative mass of PG 1302-102’s black holes, they narrow down the pair’s predicted crash time to between 20,000 and 350,000 years from now with a best estimate of 100,000 years. (The predicted crash time by Graham’s team was 10,000 to several million years from now with a best estimate of 250,000 years).

“We can start to put numbers on the rates that black holes come together and build up into larger black holes, and use what we’re learning to search for more black holes pairs,” said study coauthor David Schiminovich, an astronomer at Columbia.

An uptick in the number of black hole binary discoveries has made astronomers hopeful that a collision could be detected in the next decade. This summer, Graham and his colleagues reported another 90 candidates, while astronomers at Columbia expect to soon unveil discoveries of their own from data collected at California’s Palomar Observatory.

With more black holes to watch, the chance of witnessing a crash and the gravitational waves predicted, but not yet detected, by Einstein’s general theory of relativity, grows.

“The detection of gravitational waves lets us probe the secrets of gravity and test Einstein’s theory in the most extreme environment in our universe–black holes,” said the study’s lead author, Daniel D’Orazio, a graduate student at Columbia. “Getting there is a holy grail of our field.”

Story Source:

The above post is reprinted from materials provided by Columbia University. Note: Materials may be edited for content and length.

Journal Reference:

1. Daniel J. D’Orazio, Zoltán Haiman, David Schiminovich. Relativistic boost as the cause of periodicity in a massive black-hole binary candidate. Nature, 2015; 525 (7569): 351 DOI:10.1038/nature15262

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To obtain these highest-resolution radar images of the asteroid, scientists used the 230-foot (70-meter) DSS-14 antenna at Goldstone, California, to transmit high-power microwaves toward the asteroid. The signal bounced off the asteroid, and its radar echoes were received by the National Radio Astronomy Observatory’s (NRAO) 100-meter (330-foot) Green Bank Telescope in West Virginia. The radar images achieve a spatial resolution as fine as 13 feet (4 meters) per pixel.

The radar images were taken as the asteroid flew past Earth on October 31 at 1 p.m. EDT at about 1.3 lunar distances (300,000 miles, or 480,000 kilometers) from Earth. Asteroid 2015 TB145 is spherical in shape and approximately 2,000 feet (600 meters) in diameter.

“The radar images of asteroid 2015 TB145 show portions of the surface not seen previously and reveal pronounced concavities, bright spots that might be boulders, and other complex features that could be ridges,” said Lance Benner of NASA’s Jet Propulsion Laboratory in Pasadena, California, who leads NASA’s asteroid radar research program. “The images look distinctly different from the Arecibo radar images obtained on October 30 and are probably the result of seeing the asteroid from a different perspective in its three-hour rotation period.”

“Working with our observatory partners, we were able to get our resolution down to less than 13 feet (four meters) per pixel,” said Shantanu Naidu, a postdoctoral student at the California Institute of Technology in Pasadena, and a member of the radar team. “It is a truly remarkable achievement, one which we will later be able to apply when future flyby opportunities present themselves.”

The next time that asteroid 2015 TB145 will be in Earth’s neighborhood will be in September 2018, when it will make a distant pass at about 24 million miles (38 million kilometers), or about a quarter the distance between Earth and Sun.

Radar is a powerful technique for studying an asteroid’s size, shape, rotation, surface features and surface roughness, and for improving the calculation of asteroid orbits. Radar measurements of asteroid distances and velocities often enable computation of asteroid orbits much further into the future than would be possible otherwise.

The 100-meter GBT is the world’s largest fully steerable radio telescope. Its location in the National Radio Quiet Zone and the West Virginia Radio Astronomy Zone protects the incredibly sensitive telescope from unwanted radio interference, enabling it to perform unique observations.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

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The above post is reprinted from materials provided by National Radio Astronomy Observatory. Note: Materials may be edited for content and length.

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For many years it was thought that these megafloods were caused by the release of a deep global hydrosphere in the Martian subsoil. However, the research conducted by J. P. Alexis Rodríguez of the Planetary Science Institute (PSI-USA), with the participation of Rogelio Linares and Mario Zarroca of the Department of Geology of the Universitat Autònoma de Barcelona (UAB), has revealed that their origin could have been vast quantities of sediment and ice deposited 450 million years before the floods.

The findings from this project, which was partially supported by NASA funding for the PSI under its Planetary Geology and Geophysics Program, are detailed in the study entitled “Martian outflow channels: How did their source aquifers form, and why did they drain so quickly?”

The article, co-authored by the UAB Geology Department members mentioned above, describes how the sediments carried by rivers and glaciers filled up enormous canyons below an ancient ocean located in the Northern Lowlands, and how it was the release of the water trapped in these buried sediments that caused the megafloods, whose effects we can observe in the present.

The canyons filled up, the ocean disappeared and the planet surface remained frozen for around 450 million years. Subsequently, 3200 million years ago, the heat from lava beneath the canyons thawed the ice trapped in the sediments and enormous rivers of subterranean water spread over hundreds of kilometres, before eventually bursting out on to the now-dry surface and causing the megafloods.

In the words of the Geology Department researchers, “Our research suggests that, given that the process was regional rather than global, there could still be large reservoirs of subterranean water trapped under the surface of Mars, in the areas around the old northern ocean, or in other parts of the planet where seas and lakes formed at the same time.” “Traces of ancient environments capable of sustaining life forms similar to those on Earth could have been preserved in sub-surface materials that are now exposed,” claim R. Linares and M. Zarroca. “The results obtained could have clear implications both for exobiological research and for future human activity on Mars.”

To illustrate the scale of the Martian megafloods, the UAB researchers have estimated the effect they would have on Europe, quantifying it as around 2,500,000 km².

Story Source:

The above post is reprinted from materials provided by Universitat Autònoma de Barcelona. Note: Materials may be edited for content and length.

Journal Reference:

1. J. Alexis P. Rodriguez, Jeffrey S. Kargel, Victor R. Baker, Virginia C. Gulick, Daniel C. Berman, Alberto G. Fairén, Rogelio Linares, Mario Zarroca, Jianguo Yan, Hideaki Miyamoto, Natalie Glines. Martian outflow channels: How did their source aquifers form, and why did they drain so rapidly?Scientific Reports, 2015; 5: 13404 DOI: 10.1038/srep13404

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