New method measures spin of a supermassive black hole

Nearly every galaxy in the cosmos houses a supermassive black hole at its center; our own Milky Way Galaxy contains Sagittarius A*, a black hole four million times as massive as our sun. Although Sagittarius A* is by far the closest supermassive black hole to Earth, it is not the only one that is ripe for study.

A team at Durham University in the United Kingdom, led by Professor Chris Done, has conducted observations of a supermassive black hole even more massive than Sagittarius A* – 10 million times more massive than the sun. This particular supermassive black hole, PG1244+026, is located in a spiral galaxy 500 million light years from Earth. PG1244+026 is surrounded by an accretion disc of material being consumed by the black hole.

Done and colleagues gathered data on x-rays and optical and ultraviolet light generated as the black hole devours the disc; they used this information, obtained by the European Space Agency’s XMM-Newton satellite, to determine the distance between the black hole and the disc. This distance depends on the rate of the black hole’s spin; the faster the black hole spins, the closer it pulls the disc towards itself. Having determined the distance separating PG1244+026 and its accretion disc, the team was able to determine the spin of the black hole.

Although it is immense compared to our sun, PG1244+026 is tiny compared to the mass of its host galaxy. “We know the black hole in the center of each galaxy is linked to the galaxy as a whole, which is strange because black holes are tiny in relation to the size of the galaxy,” Done explained in a press release. “This would be like something the size of a large boulder (10 [meters across]) influencing something the size of the Earth.”

Supermassive black holes, such as PG1244+026, eject high energy particles that can hinder the cooling of intergalactic gases and impede the formation of new stars in the outer reaches of a galaxy. The reason black holes emit these jets of particles is not known, but Done and team think they could be connected to the spin of the black hole.

A spinning black hole also pulls space and time and the accretion disc along with it; as the accretion disc moves inward, closer to the black hole, the spin of the black hole increases. By accurately measuring the spins of black holes such as PG1244+026, Done and colleagues aspire to reveal how supermassive black holes affect the evolution of their galaxies. The new research has been published in the journal Monthly Notices of the Royal Astronomical Society.


New experiment supports Einstein’s universal speed limit

Researchers at the University of California, Berkeley have devised a new method to test one of 20th Century physics’ grandest and most influential tenets: the universal speed limit, that is, the speed of light.

The new experiment was designed by Berkeley postdoc Michael Hohensee, graduate student Nathan Leefer, and Professor Dmitry Budker. “As a physicist, I want to know how the world works, and right now our best models of how the world works – the Standard Model of particle physics and Einstein’s theory of general relativity – don’t fit together at high energies,” Hohensee explained in a press release. “By finding points of breakage in the models, we can start to improve these theories.”

A central assumption of both the Standard Model and general relativity is that the speed of light, 186,000 miles per second, is universal and is the maximum attainable speed for objects moving in any direction. Previous research has studied radiation emitted by high-energy electrons to discern any violations of universal light speed. For example, if the speed limit were lower in one direction than in another, this would violate the Standard Model and suggest that a novel explanation was necessary.

In their new experiment to detect such violations, Hohensee and colleagues studied two isotopes of the rare-earth element dysprosium; isotopes are variants of an element that differ in their numbers of neutrons. The researchers wanted to determine if Earth’s orientation, position, and direction of motion affected the amount of the transition energy needed to drive electrons in the samples from one energy state to a higher state. They first hit the dysprosium samples with two laser beams that excited the electrons to energy state B, and then used a microwave beam to push the electrons to the next energy state, A. This procedure was repeated numerous times from 2010 to 2012.

Once the team had determined the microwave frequency most effective at pushing the electrons from state B to A, they could derive the energy necessary to alter the velocity of the electrons as they leapt from B to A. They found that the maximum speed of an electron, i.e., the speed of light, is equal in all directions to within 17 nanometers per second. If the electrons’ velocity depended on their direction of movement, there would have been a daily shift in the transition energy due to Earth’s rotation. Also, there would have been an annual change in the transition energy if there were any influence from Earth’s revolution through the sun’s gravitational field.

The team will refine their experiment and might eventually achieve measurements 1,000 times more precise than their current findings.

The new research was published in the July 29 issue of the journal Physical Review Letters.


2013 Perseid meteor shower set to dazzle skywatchers

Cast your eyes skyward for a spectacular astronomical display on August 12 and 13. In the pre-dawn hours of those two days, the Perseid meteor shower will attain its zenith as Earth sails through a stream of debris from Comet Swift-Tuttle.

The optimal time to spot the Perseids on August 12 and 13 is between 10:30 PM and 4:30 AM local time. The meteor rate will begin low before midnight and steadily increase through the night; it will reach its peak before sunrise when the constellation Perseus is high in the sky. If possible, try to avoid the glare of city lights; typically, three times as many faint meteors can be spotted from the countryside.

Stargazers will be blessed with dark skies from late at night until dawn thanks to a crescent moon that will set soon after midnight. During the darkest-sky hours, over 100 Perseid meteors could be visible each hour. The meteors will strike Earth’s atmosphere at around 132,000 miles per hour, and create a very impressive display as they incinerate.

A team led by Bill Cooke of NASA’s Meteoroid Environment Office has been tracking meteor shower activity across the southern United States since 2008, thanks to a network of cameras distributed throughout the region. Of the seven major comet-born meteor showers that grace Earth each year, the Perseids are the most numerous; other showers include the Lyrids, Orionids, and Geminids.

The copiousness of the Perseids is likely due to the great size of Comet Swift-Tuttle, the nucleus of which is approximately 26 kilometers in diameter – much larger than most other comets. Although meteors can be spotted burning up in the atmosphere year-round, they are far more frequent when Earth passes through the debris field ejected by a comet, such as Swift-Tuttle, as it approaches the sun and rocks, ice, dust, and gas boil off its surface.

Comet Swift-Tuttle is the largest known object that makes repeated passes close to Earth. It was observed in the night sky in 1862, reappeared in 1992, and is due to light up the sky again in 2126. Although the comet comes quite close to Earth and the Moon, its orbit is stable and there is no threat of impact for the next 2,000 years. In the year 4479, the comet will come within five million miles of Earth, and the chances of impact are literally one in a million.

So, sit back, relax, and enjoy the Perseid show next month.


Confirmation that neutrinos do change ‘flavor’

An experiment in Japan has verified that neutrinos, an ultra-common category of elementary particle, transform from one type to another.

Neutrinos are one of the most ubiquitous types of elementary particle, a subatomic particle that is not composed of smaller components, in the universe. The Big Bang produced neutrinos in vast quantities, and it is estimated that neutrinos from this source number over 300 per cubic centimeter everywhere in the universe.

The particles have many present-day sources as well: stars, including our sun, which produces over 60 billion per square centimeter per second; supernovae; cosmic rays; radioactive decay on Earth and elsewhere; and artificial sources such as nuclear reactors and particle accelerators. Neutrinos are probably the third most common particle in the universe, after photons and hypothetical dark matter particles.

Neutrinos are similar to electrons but have no electric charge and are far lighter, with only four-millionths as much mass. Neutrinos hardly interact at all with other particles – billions of solar neutrinos are streaming through every human on Earth, as well as Earth itself, every moment of every day.

There are three types of neutrinos: electron, muon, and tau, named after their partner particles. Neutrinos can oscillate, or shift from one type, or ‘flavor’, to another. In 2011, the Tokai-to-Kamioka experiment (T2K) discovered the first hints of a new type of oscillation: muon neutrinos becoming electron neutrinos.

Now, fresh experiments by the T2K team have confirmed the existence of this oscillation. A muon-neutrino beam was produced at the Japan Proton Accelerator Research Complex (J-PARC) in Tokai village on the east coast of Honshu, the main island of Japan. The beam was detected 185 miles away on the island’s west coast at the massive underground Super-Kamiokande Detector.

The new data indicate that more electron neutrinos were detected than expected; 4.6 electron neutrino events were anticipated, but 28 occurred. This result would be impossible if some of the muon neutrinos had not transformed into electron neutrinos.

T2K will next investigate whether neutrinos and their antimatter counterparts, antineutrinos, alter their flavors in the same way. If the processes are different, it might explain why the universe is composed of matter rather than antimatter.

T2K is a collaborative effort by scientists from 59 institutions in 11 countries. The new discovery is even more remarkable considering that J-PARC staff had to repair the particle accelerator after the horrendous earthquake that struck Japan in 2011.


Freezing molecules provide clues to planet formation

The Atacama Large Millimeter/submillimeter Array (ALMA) in Chile has detected a series of snow lines around TW Hya that mark distances at which the star’s heat is no longer sufficient to keep certain molecules in a gaseous state.

Located approximately 175 light-years from Earth, TW Hya is part of the TW Hydra Association, a gaggle of stars less massive than our sun located in the constellation Hydra. TW Hya is only three million years old, quite young compared to our sun’s age of 4.6 billion years, and it is only 0.4 times the mass of the sun. At this age and mass, TW Hya is classified as a pre-main sequence star.

Surrounding TW Hya is a protoplanetary disc of material that will eventually condense to form planets; in fact, on June 13, NASA’s Hubble Space Telescope observed a gap in the disc that indicates the presence of an incipient planet plowing through the dust. The disc is over 100 AU in diameter (1 AU equals 93 million miles, the distance between Earth and the sun). TW Hya is the closest pre-main sequence star with a protoplanetary disc to Earth, and so receives a great deal of attention as scientists strive to answer questions about how planets form in young solar systems.

New research led by Chunhua Qi of the Harvard-Smithsonian Center for Astrophysics has discerned snow lines in the protoplanetary disc of TW Hya. Temperature decreases farther away from the star, so different substances freeze into snow at different distances in the disc. Moving outwards from the star, water freezes first, followed by carbon dioxide, methane, and carbon monoxide. As snow of some kind forms around the dust in the disc, it prevents the dust particles from fragmenting when they collide and increases the amount of solid matter in the disc, promoting aggregation of dust into larger and larger bodies that could eventually become planets.

The distances of the different snow lines from TW Hya also allow predictions to be made about what type of planets might form. In a solar system like ours, the water snow line would be between the orbits of Mars and Jupiter, and the carbon monoxide line would correspond to Neptune’s orbit. Inside the water line, rocky planets, such as Earth and Mars, form because only dust is present as a solid; beyond the carbon monoxide line, ice giants, such as Neptune, form.

To identify the carbon monoxide line, ALMA searched TW Hya’s disc for diazenylium, which cannot survive in the presence of carbon monoxide gas. Diazenylium exists only where carbon monoxide as frozen into snow.

The research was published in the July 18 issue of the journal Science Express.


Gold originated in the collisions of neutron stars

Most of the elements we encounter on Earth were created in dying massive stars. After a star more than eight times the mass of our sun uses up its supply of hydrogen through nuclear fusion into helium, they develop carbon-oxygen cores. At 1 billion degrees Kelvin, the star ignites carbon, and oxygen, neon, and magnesium fuse to produce silicon, which in turn fuses to form iron.

Once the star’s core has been converted to iron, it begins to degenerate and cool and finally collapses rapidly. The outer layers of the star explode into space – a supernova. The elements ejected into space can eventually become components of a nascent solar system, such as the disc of dust and gas that surrounded our young sun 4.6 billion years ago. Those elements become incorporated into newly forming planets, such as Earth, and into any life that might arise on those planets. Hence Carl Sagan’s phrase “We’re made of star stuff.”

However, unlike heavy elements such as iron, gold cannot be generated within a star. New research led by Edo Berger of the Harvard-Smithsonian Center for Astrophysics has identified the phenomenon responsible for producing gold.

Berger and colleagues studied a recent gamma ray burst, GRB 130603B, which occurred 3.9 billion light-years from Earth and was detected by NASA’s Swift satellite on June 3. The burst lasted for less than two-tenths of a second. Gamma ray bursts are flashes of high-energy light from an extraordinarily energetic explosion. The gamma rays vanish quickly, but they leave behind an after-glow as high-speed particles collide with the surrounding interstellar matter.

The after-glow of GRB 130603B did not correspond in brightness or behavior with previously observed after-glows. Instead, the after-glow was dominated by infrared light, indicating that it originated from exotic elements undergoing radioactive decay. Such elements are created by the neutron-rich material ejected by colliding neutron stars. Neutron stars form when the core of a massive star collapses and protons and electrons are crushed together. Neutron stars can contain 1.3 to 2.5 times as much mass as the sun in a sphere only 12 miles across; the material is so dense that a sugar-cube-sized sample of a neutron star would weigh more than 1 billion tons.

The collision that generated GRB 130603B ejected matter, including gold, equivalent to one-hundredth the mass of the sun. Given the amount of gold produced by GRB 130603B and the number of gamma ray bursts estimated to have happened during the universe’s existence, all the gold in the universe might have been formed in gamma ray bursts.

The new research has been submitted for publication in the periodical Astrophysical Journal Letters.


Study: Length of day affected by Earth’s core

It seems an immutable fact of life: there are precisely 24 hours in a day – that is, it takes 24 hours for Earth to rotate once around its axis. However, this was not always the case; for example, 300 million years ago, in the Carboniferous Period, a day on Earth was only 21 hours long and a year lasted 450 days.

300 million years is a long time, but a new study by Richard Holme of the University of Liverpool and Olivier de Viron of the University of Paris Diderot has characterized the source of variation in length of day within a decade: Earth’s fluidic outer core.

Earth’s interior is demarcated into a series of concentric spherical layers, like the inside of an onion. Earth’s crust is at most only 100 kilometers thick. Below the crust lies the far thicker mantle, 2,900 kilometers of hot, dense semi-solid rock rich in iron, magnesium, and calcium; the greater heat and density of the mantle are attributable to greater temperature and pressure that increase with depth. Inwards of the mantle is the 2,200 kilometer-thick outer core and the 1,250 kilometer-thick inner core. The entire core is metallic, composed of iron and nickel, but the outer core is liquid while the inner core is solid. Earth’s rotation causes the fluidic outer core to spin, generating Earth’s magnetic field.

Holme and de Viron analyzed data on the length of day (LOD) from 1962 to 2012. They corrected for LOD fluctuations that happen on a yearly or shorter basis, caused by oceanic and atmospheric effects; for example, the force of wind blowing against mountain ranges alters LOD by plus or minus a millisecond per year.

Once this statistical technique had been employed, Holme and de Viron were able tease out longer, decade-scale cycles. They identified a 5.9-year cycle over which LOD changes by fractions of milliseconds per year. This cycle is caused by fluctuations in the motion of the outer core relative to the mantle.

The study also found a well-known decade-long cycle, over which LOD increases by a few milliseconds over approximately 10 years and then steadily decreases, also caused by changes in motion in the core. However, the study also recognized three unexpected jumps in LOD in 2003, 2004, and 2007, which interrupted the longer-term fluctuations by a fraction of a millisecond for several months before returning to normal. These “jerks” might be linked to events in which a large portion of liquid outer core temporarily attaches to the mantle, altering its momentum.

The study by Holme and de Viron was published in the July 11 issue of the journal Nature.


NASA relies on GPS to measure hurricane strength

GPS has become a fact of life, guiding millions of people on endeavors as epic as ocean crossings and as simple as finding a good restaurant. Now, new research at NASA’s Langley Research Center has identified a new use for the global satellite system: mapping and measuring hurricane wind speeds.

GPS satellites transmit radio waves towards Earth’s surface, relaying information about the satellite’s position and the time that the message was sent. As with other forms of radiation, such as visible light, GPS radio waves can bounce off a surface. When the radio waves strike the surface of a body of water, approximately 60 percent of the signal is reflected towards the sky. However, wind blows over water, creating waves that vary in intensity with the speed of the wind. As the surface of the water becomes rougher, the reflected radio waves become more distorted and are scattered in various directions.

The research team, led by Stephen Katzberg, has used these principles to devise a method to determine hurricane wind speeds and their distribution within a storm. The system uses GPS receiver chips aboard aircraft. A computer compares the signals emanating from satellites overhead with the reflected, distorted signals bouncing up from the ocean below. Based upon this, the computer calculates the approximate wind speed with accuracy to within 11 miles per hour. This is a remarkable degree of accuracy; for example, the wind speed of a Category 3 hurricane, in the middle of the Saffir-Simpson Hurricane Wind Scale, is 111 to 129 miles per hour.

The new system invented by Katzberg and colleagues is not intended to fully replace the current system, in which hurricane hunting aircraft release 16-inch tubes crammed with scientific instruments. These tubes, called dropsondes, can be used only once and cost about $750 each. Each mission uses around 20 dropsondes. Their high cost requires that dropsondes be spread out in and around storms, and their distance from each other requires meteorologists to fill in gaps with some guesswork.

Dropsondes do still have some advantages over the new GPS system. They can measure pressure, humidity, and temperature in addition to wind speed and they can measure wind speed accurately to within 1.1 miles per hour. However, unlike the dropsondes, the GPS system can run continuously and gather more wind data.

NASA intends to launch a system of small satellites in 2016 to measure reflected GPS signals from low orbit. This system, the Cyclone Global Navigation Satellite System, will monitor wind speeds.

The team’s research is described in a paper accepted for publication in Radio Science, a periodical of the American Geophysical Union.


Telescope captures amazing baby photos of monster star

A vast “stellar womb” over 500 times the mass of our sun has been observed by the Atacama Large Millimeter/submillimeter Array (ALMA), which peers through the clear skies of the high desert of Chile.

ALMA took a microwave scan of the Spitzer Dark Cloud (SDC) 335.579-0.292. This hazy environment of dense filaments of gas and dust was first observed by NASA’s Spitzer Space Telescope and ESA’s Herschel Space Observatory. Now, a team led by Nicholas Peretto of CEA/AIM Paris-Saclay in France and Cardiff University in the United Kingdom, has employed the more sensitive ALMA to measure the quantity of dust and the motion of gas in SDC 335.579-0.292. In so doing, the team discovered an astonishing embryonic star, or “protostellar core”.

Of the many stars forming in SDC 335.579-0.292, the protostellar core observed by ALMA is by far the most massive, “the largest protostellar core ever spotted in the Milky Way,” Peretto effused in a European Southern Observatory (ESO) press release. “Even though we already believed that the region was a good candidate for being a massive star-forming cloud, we were not expecting to find such a massive embryonic star at its center.”

The enormous protostellar core is already more than 500 times more massive than our sun, and ALMA data indicate that even more material is still flowing inwards, giving the nascent star still more mass. The protostellar core and surrounding material will eventually collapse inwards to create a new star up to 100 times the mass of our sun. Only approximately one in 10,000 stars in the Milky Way attain such a tremendous mass.

ALMA’s observations of the giant protostellar core support the hypothesis that massive stars, stars 10 or more times as massive as our sun, form through inward collapse of the entire parent cloud as material flows into the cloud’s center to form one or more new massive stars, rather than through fragmentation of the cloud to form several protostellar cores that collapse on their own.

Observing such a massive protostellar core at this stage of development is unheard of and is a “spectacular result”, said team member Gary Fuller of the University of Manchester, U.K. “Their birth is extremely rapid and their childhood is short,” Fuller said of the rare massive stars.

Elucidating as the new findings are, they utilized only a quarter of the full array of antennas at ALMA. In Peretto’s words, “ALMA will definitely revolutionize our knowledge of star formation, solving some current problems, and certainly raising new ones.”

The team’s findings will be reported in the journal Astronomy & Astrophysics.


Lake Vostok may provide clues for life on other planets

Under more than 3,700 meters (12,130 feet) of Antarctic glacial ice rests a vast body of liquid water known as Lake Vostok. With a volume of 1,800 cubic kilometers and an average depth of 125 meters, Lake Vostok is the seventh largest and fourth deepest lake on Earth, and the largest subglacial lake on the planet. Vostok’s water remains liquid thanks to a geothermal heat source in the continental crust beneath the lake and the pressure of the overlying ice, and now it is providing scientists with an idea of just how life can adapt to nearly any environment, including space.

A team from Bowling Green State University, led by Yury M. Shtarkman, has analyzed genetic material contained in an ice core recently drilled by Russian researchers. The samples come from the accretion ice, a layer of relatively pristine ice that forms between the liquid water of the lake and the overlying glacier.

Shtarkman and his colleagues contend that the genetic material is not outside contamination, based upon the results of several previous studies: a higher concentration and diversity of cells is present in the accretion ice layer than in the glacier; unique bacterial and fungal sequences have been identified in the same sections of the accretion ice core; and all the genetic sequences are most closely related to species that inhabit similar environments, such as lake/ocean sediment and frigid, polar, and/or deep-sea settings.

In their current study, reported in PLoS ONE, Shtarkman and colleagues were able to identify 1,623 genetic sequences to their species. Ninety-six percent of the sequences came from bacteria and six percent from eukaryotes (mostly fungi). Some of the bacteria identified are normally associated with more complex organisms, including anemones, worms, and fish. These results suggest that a complex ecosystem might be thriving under the ice in Lake Vostok.

Although the lake has been isolated from Earth’s atmosphere for 14 million years, it was once exposed to the outside world; over 35 million years ago, Antarctica was far more hospitable and Vostok was free of ice, allowing organisms ample time to migrate in. Since becoming sealed under the glacier, Vostok’s organisms would have followed their own evolutionary course, possibly sustained by nutrients from hydrothermal vents fed by the geothermal activity in the underlying crust.

According to SETI astrobiologist Dale Andersen in an interview with Discovery News, research on Lake Vostok “helps us learn how to explore these kinds of environments better.” Vostok is a dry run, so to speak, for human exploration of the liquid oceans hypothesized to exist under the ice that covers some of our solar system’s moons, including Jupiter’s Ganymede and Europa, and Saturn’s Enceladus.