Massive Black Holes Caught in Death Spiral

BY DENNIS OVERBYE



The apocalypse is still on, apparently-at least in a galaxy about 3.5 billion light-years from here.

Last winter, astronomers at the California Institute of Technology reported that two supermassive black holes appeared to be spiraling toward a cataclysmic collision that could bring an end to that galaxy.

The evidence was a rhythmic flickering from the galaxy’s nucleus, a quasar known as PG1302-102, which Matthew Graham and his colleagues interpreted as the fatal mating dance of a pair of black holes with a total mass of more than a billion suns. Their merger, the astronomers calculated, could release as much energy as 100 million supernova explosions, mostly in the form of violent ripples in space-time known as gravitational waves that would blow the stars out of that hapless galaxy like leaves off a roof.

The supermassive black holes are all that remains of galaxies once all protons decay, but even these giants are not immortal. (Photo credit: Wikipedia)

Now a new analysis of the system by Daniel D’ Orazio of Columbia University in New York and his colleagues has added weight to that conclusion. Mr. D’ Orazio, a graduate student, and Zoltan Haiman and David Schiminovich propose that most of the light from the quasar is coming from a vast disk of gas surrounding the smaller of the two black holes.

As the black holes and their attendant disks swing around each other at high speeds, the light from the disk that is coming toward us receives a boost from relativistic effects-a so-called Doppler boost-the way a siren grows louder and more high-pitched as it approaches, giving rise to a periodic increase in brightness every five years.

The Columbia astronomers ‘model predicts that the variation would be two or three times greater in ultraviolet light than in visible light. And that is exactly what they found when they compared archival data from the Hubble Space Telescope and NASA’s Galex space telescope to the visible-light data previously analyzed by Dr. Graham’s group.

“What’s big is that the Doppler boost is inevitable,” Dr. Haiman said in an email. Given reasonable assumptions about the masses of the black holes, their model predicts the right ultraviolet data.

“This is rare in ‘messy’ astronomy,” he said, “to have an indisputable clean effect, which explains the data.”

Follow-up observations of ultraviolet and visible light emissions in the coming years could help clinch the case, the authors said. Their paper was published last month in the journal Nature.

Their model suggests that the black holes are orbiting each other at a distance of some 320 billion kilometers, less than tenth of a lightyear, a cosmic whisker. At that distance, the black holes would be rapidly losing energy by radiating gravitational waves and could spiral together into the final bang in as little as 100,000 years, Dr. Haiman said, depending on their relative masses.

An artist's conception of a supermassive black hole and accretion disk. (Photo credit: Wikipedia)

“Basically, the more massive the holes, the faster gravitational waves drive them together, and we do require them to be as massive as allowed to be ,” he said in an email. For their model to hold up, the larger of the black holes has to be a billion solar masses or more.

(Because the galaxy is so far away, the cataclysm might well have already happened more than three billion years ago, but the news still won’t reach us for another 100,000 years or so. So it is still in the future, as far as earthlings-whoever they will be by then-are concerned.)

E.Sterl Phinney, a Caltech astronomer and expert on supermassive black holes, agreed that Dr.Haiman’s model explained the quasar variations. “So Occam’s razor makes it attractive,” he said, referring to the long-held principle that physicists should adopt the simplest theory that fits the facts. But it was surprising, he said, to find two supermassive black holes that have gotten so close.

Black holes, predicted by Albert Einstein’s general theory of relativity, are objects so dense that not even light can escape from them. Every galaxy of note seems to have a supermassive black hole, weighing millions or billions of times as much as the sun, burping sparks of half-eaten stars and gas.

“A scientific theory is only as good as the tests which it has passed,” Mr. D’ Orazio said.

Einstein’s theory has passed all of the observational and experimental tests thrown at it so far. But some of its predictions can be tested only in the most extreme gravitational environments, namely black holes.



Taken from TODAY Saturday Edition, The New York Times International Weekly, October 3, 2015

Planet Mercury Is Shown To Be More Than a Little Bore

English: Artist's rendering of the MESSENGER spacecraft orbiting Mercury (Photo credit: Wikipedia)

By KENNETH CHANG


NASA’s Messenger spacecraft, in orbit around Mercury for the past four years, came to an abrupt end on April 30 when it crashed into the surface.

That event brought to a close a mission that has painted an unexpected portrait of Mercury, once thought a boring round rock not much different from Earth’s moon. Mercury, the smallest planet in our solar system, is only slightly larger than the moon, although it has more drastic temperature swings – 427 degrees Celsius during the day, minus 184 degrees at night.

“It’s really been exciting to see a planet unfold, a planet that is one of our neighbors,” said Sean C. Solomon, the principal investigator for the mission. “Almost every aspect of Mercury has had its share of surprises.”

Messenger – a shortening of Mercury Surface, Space Environment, Geo-chemistry and Ranging – discovered that Mercury shrank slightly as it cooled over billions of years; mapped ancient lava flows; found enigmatic shallow depressions that are some of the youngest and brightest features on the surface; and confirmed the presence of ice in perpetually dark crates near the poles.

The water ice, perhaps a billion tons, was not a complete surprise. Radio telescope observations from Earth had hinted at something reflective, and the shadowed craters are extremely cold. Beyond confirming the suspected, Messenger also made a new discovery: The ice was covered by an unexplained dark layer.

“We have a reasoned hypothesis,” Dr. Solomon said. The material could be carbon-rich compounds, similar to substances found in certain meteorites and in comets. “It’s tarlike in its consistency,” he said. “It’s as dark as tar.”

The biggest scientific finding of the mission, Dr. Solomon said, was that Mercury was rich in “volatiles,” elements like chlorine, sulfur, potassium and sodium that easily evaporate at moderate temperatures. Mercury is small and dense, full of iron, and the thinking about how it formed was that it must have been heated to temperatures that should have boiled off the volatiles. Yet the volatiles are still there.

Scientists now have to come up with new ideas to explain how Mercury formed. When NASA launched Messenger in 2004, knowledge of Mercury was sparse. The only close-ups had come in three flybys by NASA’s Mariner 10 in the 1970’s

For more than six years, Messenger took a circuitous route through the inner solar system, making flybys of Earth, Venus and Mercury, to slow itself down enough to enter orbit around Mercury. On March 18, 2011, finally arrived.

The orbital portion of the mission was to last one year, then was extended twice.

Even the craft’s destruction could provide insights by digging up what lies beneath the surface- but it will be some time before anyone will see what that is. NASA does not have any follow-up Mercury missions set, but an ambitious European and Japanese collaboration called BepiColombo is scheduled to launch in 2017. It is to arrive at Mercury in 2024.

That mission consists of two orbiters, one focusing on the planet, the other on the surrounding space environment, in greater and finer detail than Messenger.

Johannes Benkhoff, the project scientist for BepiColombo at the European Space Agency, described Messenger as “really a fantastic mission.”

“It’s perfect that we have BepiColombo to follow on” Messenger’s findings, Dr. Benkhoff said. “They have provided a lot of new results, unexpected results.”

BepiColombo is named after Giuseppe Colombo, an Italian scientist nicknamed Bepi who came up with the orbital trajectories that enabled NASA’s Mariner10 flybys.

Dr. Solomon is looking forward to the next trip to Mercury I still want to learn more about, “he said.


Taken from TODAY Saturday Edition, The New York Times International Weekly, May 9, 2015

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Chile quake may have moved Earth's axis

Chile quake moved Earth's axis, shortened days: scientist

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AFP - Wednesday, March 3

A gap in a road caused by Saturday's earthquake and the ensuing tsunami in Pulluhue, 320 km south of Santiago. The powerful earthquake that shook Chile on Saturday probably shifted the Earth's axis and made days slightly shorter, a NASA scientist said.

WASHINGTON (AFP) - – The powerful earthquake that shook Chile on Saturday probably shifted the Earth's axis and made days slightly shorter, a NASA scientist said.

Richard Gross, a research scientist at NASA's Jet Propulsion Laboratory in California, calculated that the planet's axis would have shifted by eight centimeters (three inches) during the 8.8 magnitude quake, NASA said in a statement.

Earth days are 24 hours long because that's the amount of time it takes the planet to make one full rotation on its axis, so shifting the axis would affect rotation.

If, indeed, the planet's axis did shift by eight centimeters during the Chilean quake, days would have shortened by 1.26 microseconds, Gross calculated.

A microsecond is one-millionth of a second, so no need to adjust watches just yet.

The Chilean quake shifted the Earth's axis by even more than the 9.1-magnitude temblor off Indonesia that set off the deadly tsunami in Asia in 2004, Gross worked out.

That's partly because the faultline responsible for the earthquake in Chile "dips into Earth at a slightly steeper angle than does the fault responsible for the 2004 Sumatran earthquake" and is more effective at moving Earth's mass vertically and shifting the planet's axis.

The 2004 quake in Asia caused the Earth to move by around seven centimeters and chopped an estimated 6.8 microseconds off the length of a day, NASA said.

From Yahoo.SG News; original article is found here

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Two NASA space probes near moon

Updated 3 hours, 15 minutes ago

Story Highlights

• Two space probes to begin collecting data from the moon Tuesday
• One probe will send back lilve video on the Internet
• Orbiter will collect data to be used to plan a lunar outpost

Dan Andrews, LCROSS manager, left, and Craig Tooley, LRO manager stand in front of the spacecraft.

(CNN) -- Two NASA spacecraft closed in on the moon Tuesday morning -- one to send streaming video to Earth as it swings past the moon, the other to map the lunar surface from orbit, the space agency said.

The two probes were to begin collecting data after nearing the moon's orbit about 5:30 a.m. ET.

By about 8:20 a.m. E.T., the space agency will begin streaming footage on the Internet.

The Lunar Reconnaissance Orbiter, and the Lunar Crater Observation and Sensing Spacecraft, lifted off June 18 atop the same Atlas V rocket.

Drawing depicts the Lunar Reconnaissance Orbiter, which will look for potential landing sites on moon.

The mission is the first in NASA's plan to return to the moon, then travel to Mars and beyond, the space agency said.

During the mission, the agency will collect all sorts of data, including day-night temperature maps, NASA said. There is particular emphasis on the polar areas of the moon, where sunlight is more plentiful and where water might exist.

The data that the orbiter collects and sends to Earth will be used in planning an eventual lunar outpost, the agency said. The orbiter also will look for potential landing sites for astronauts.

From CNN.com; see the source article here.

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Two NASA space probes near moon

Updated 3 hours, 15 minutes ago

Story Highlights

• Two space probes to begin collecting data from the moon Tuesday
• One probe will send back lilve video on the Internet
• Orbiter will collect data to be used to plan a lunar outpost

Dan Andrews, LCROSS manager, left, and Craig Tooley, LRO manager stand in front of the spacecraft.

(CNN) -- Two NASA spacecraft closed in on the moon Tuesday morning -- one to send streaming video to Earth as it swings past the moon, the other to map the lunar surface from orbit, the space agency said.

The two probes were to begin collecting data after nearing the moon's orbit about 5:30 a.m. ET.

By about 8:20 a.m. E.T., the space agency will begin streaming footage on the Internet.

The Lunar Reconnaissance Orbiter, and the Lunar Crater Observation and Sensing Spacecraft, lifted off June 18 atop the same Atlas V rocket.

Drawing depicts the Lunar Reconnaissance Orbiter, which will look for potential landing sites on moon.

The mission is the first in NASA's plan to return to the moon, then travel to Mars and beyond, the space agency said.

During the mission, the agency will collect all sorts of data, including day-night temperature maps, NASA said. There is particular emphasis on the polar areas of the moon, where sunlight is more plentiful and where water might exist.

The data that the orbiter collects and sends to Earth will be used in planning an eventual lunar outpost, the agency said. The orbiter also will look for potential landing sites for astronauts.

From CNN.com; see the source article here.

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• Two NASA space probes near moon (cnn.com)
• Lunar Reconnaissance Orbiter and LCROSS to reach the Moon on Tuesday. (space.gs)
• Scrappy Post-Apollo Lunar Science Sets Stage for New Missions (wired.com)