Waves Similar To Those Controlling Weather On Earth Have Now Been Found On The Sun

A team of scientists led by the Max Planck Institute for Solar System Research (MPS) and the University of Göttingen has discovered new waves of vorticity on the Sun. As described in today’s issue of Nature Astronomy, these Rossby waves propagate in the direction opposite to rotation, have lifetimes of several months, and maximum amplitudes at the Sun’s equator. For forty years scientists had speculated about the existence of such waves on the Sun, which should be present in every rotating fluid system. Now, they have been unambiguously detected and characterized for the first time. The solar Rossby waves are close relatives of the Rossby waves known to occur in the Earth’s atmosphere and oceans.

In almost every weather map of the Earth’s northern hemisphere atmospheric Rossby waves are a prominent feature. They appear as meanders in the jet stream separating cold polar air in the north from warmer subtropical air farther to the south. Sometimes these waves reach the equatorial regions and can even affect weather in Australia. In principle, waves of this type (often referred to as planetary waves) arise on every rotating sphere due to the Coriolis force. Saturn’s hexagon, a stable cloud pattern at the planet’s north pole, may also be an expression of these waves.

The existence of Rossby waves in stars was predicted about forty years ago. “Solar Rossby waves have very small amplitudes and periods of several months, thus they are extremely difficult to detect”, says Prof. Dr. Laurent Gizon, coordinator of the team that made the discovery and director at the MPS. The study required high-precision observations of the Sun over many years. The scientists from MPS analyzed a six-year dataset from the Heliospheric and Magnetic Imager (HMI) onboard NASA’s Solar Dynamics Observatory (SDO), in operation since 2010.

“The HMI images have sufficiently high spatial resolution to allow us to follow the movement of photospheric granules on the Sun’s visible surface”, says Dr. Björn Löptien, scientist at the MPS and first author of the article. These granules are small convective cells that are roughly 1500 kilometers in size on the solar surface. In their new study, the researchers used the granules as passive tracers to uncover the underlying, much larger vortex flows associated with the Rossby waves. In addition, methods of helioseismology were used to confirm the discovery and to study the Rossby waves in the solar interior at depths up to 20000 kilometers.

“All in all, we find large-scale waves of vorticity on the Sun that move in the direction opposite to rotation. That these waves are only seen in the equatorial regions is completely unexpected”, Gizon explains. The vorticity patterns are stable for several months. The researchers were able to determine the relationship between the waves’ frequency and wavelength for the first time – thus clearly identifying them as Rossby waves.

“Solar Rossby waves are gigantic in size, with wavelengths comparable to the solar radius”, Gizon explains. They are an essential component of the Sun’s internal dynamics because they contribute half of the Sun’s large-scale kinetic energy.

Are Rossby Waves To Blame For Earth’s Magnetic Field Drifting Westward?

A doctoral student at the University of Cambridge has come up with a possible explanation for the westward drift of the Earth’s magnetic field. In his paper published in Proceedings of the Royal Society A, O.P. Bardsley suggests it may be due to Rossby waves generated in the Earth’s core.

Humans first became aware of the Earth’s magnetic field over 400 years ago, and since that time, have been taking measurements of it. As time passed, it became clear that the field was moving in a westerly direction—and nobody knew why. The actual reason is still not known—Bardsley is proposing a new idea: Somehow, Rossby waves in the Earth’s outer core cause the magnetic drift.

Prior efforts to explain the westward drift have also involved the outer core—one theory suggests that it has a gyre, similar in some respects to the jet stream. If so, it could be dragging the magnetic field as it moves slowly westward. The problem with that theory, Bardsley notes, is that no one has ever found any other evidence of a gyre in the outer core. He suggests Rossby waves make more sense.

Rossby waves are slow and arise when fluids rotate. Because they are generated by most planets, some scientists have taken to calling them planetary waves. Rossby waves on Earth are generated in several places—in the oceans, the atmosphere and the outer core. It is those generated by the fluid in the outer core that Bardsley suggests might be pushing the magnetic field. But there is one major problem: The outer core generates wave crests that move east, not west. Bardsley suggests that this may not be a problem after all—he notes that some ocean waves with crests moving in one direction expend energy in the opposite direction. If that is the case with outer core Rossby waves, he suggests, they could be pushing the magnetic field. He notes that current technology only allows for measuring the energy of the magnetic field in a general sense, not the small details. Much more research is required, he acknowledges, before his theory can be tested, much less proven right or wrong.

Unusual Laser Emission From The Ant Nebula

An international team of astronomers have discovered an unusual laser emission that suggests the presence of a double star system hidden at the heart of the “spectacular” Ant Nebula.

The extremely rare phenomenon is connected to the death of a star and was discovered in observations made by European Space Agency’s (ESA) Herschel space observatory.

When low- to middleweight stars like our Sun approach the end of their lives they eventually become dense, white dwarf stars. In the process, they cast off their outer layers of gas and dust into space, creating a kaleidoscope of intricate patterns known as a planetary nebula. Our Sun is expected to one day form such a planetary nebula.

A nebula is an interstellar cloud of dust, hydrogen, helium and other ionized gases. The Ant Nebula earns its nickname from the twin lobes that resemble the head and body of an ant.

The recent Herschel observations have shown that the dramatic demise of the central star in the core of the Ant Nebula is even more theatrical than implied by its colourful appearance in visible images — such as those taken by the NASA/ESA Hubble Space Telescope.

The new data shows that the Ant Nebula also beams intense laser emission from its core. Lasers are well-known down on earth in everyday life, from special visual effects in music concerts to health care and communications. In space, laser emission is detected at very different wavelengths and only under certain conditions. Only a few of these infrared space lasers are known.

By coincidence, astronomer Donald Menzel who first observed and classified this particular planetary nebula in the 1920s (it is officially known as Menzel 3 after him) was also one of the first to suggest that in certain conditions natural ‘light amplification by stimulated emission of radiation’ — from which the acronym ‘laser’ derives — could occur in nebulae in space. This was well before the discovery of lasers in laboratories.

Dr Isabel Aleman, lead author of a paper describing the new results, said “We detected a very rare type of emission called hydrogen recombination laser emission, which is only produced in a narrow range of physical conditions.

“Such emission has only been identified in a handful of objects before and it is a happy coincidence that we detected the kind of emission that Menzel suggested, in one of the planetary nebulae that he discovered.”

This kind of laser emission needs very dense gas close to the star. Comparison of the observations with models found that the density of the gas emitting the lasers is around ten thousand times denser than the gas seen in typical planetary nebulae and in the lobes of the Ant Nebula itself.

Normally, the region close to the dead star — close in this case being about the distance of Saturn from the Sun — is quite empty, because its material is ejected outwards. Any lingering gas would soon fall back onto it.

Co-author Prof Albert Zijlstra, from the Jodrell Bank Centre for Astrophysics at University of Manchester, added: “The only way to keep such dense gas close to the star is if it is orbiting around it in a disc. In this nebula, we have actually observed a dense disc in the very centre that is seen approximately edge-on. This orientation helps to amplify the laser signal.

“The disc suggests there is a binary companion, because it is hard to get the ejected gas to go into orbit unless a companion star deflects it in the right direction. The laser gives us a unique way to probe the disc around the dying star, deep inside the planetary nebula.”

Astronomers have not yet seen the expected second star, hidden in the heart of the Ant nebula.

Göran Pilbratt, ESA’s Herschel project scientist, added: “It is a nice conclusion that it took the Herschel mission to connect together Menzel’s two discoveries from almost a century ago.”

The paper’s publication coincides with the first UNESCO International Day of Light, and celebrates the anniversary of the first successful operation of the laser in 1960 by physicist and engineer, Theodore Maiman.

Scientists Just Found the Fastest-Growing Black Hole

Researchers have spotted the fastest-growing black hole ever found — and have seen the (thankfully) distant devourer consume a mass equivalent to Earth’s sun every two days.

Researchers used newly released data from the European Space Agency’s Gaia satellite to confirm that the brightly shining object is a black hole, which appears to have been the mass of about 20 billion suns when the light was released and was growing by 1 percent every million years, researchers said in a statement released today (May 15).

“This black hole is growing so rapidly that it’s shining thousands of times more brightly than an entire galaxy, due to all the gases it sucks in daily that cause lots of friction and heat,” Christian Wolf, an astronomer at the Australian National University and first author on the new research, said in the statement. [The Strangest Black Holes in the Universe]

“If we had this monster sitting at the center of our Milky Way galaxy, it would appear 10 times brighter than a full moon. It would appear as an incredibly bright, pinpoint star that would almost wash out all of the stars in the sky,” he added.

Luckily, though, the black hole is far enough away that it likely released its light more than 12 billion years ago, the researchers said. The energy it emits is mostly ultraviolet light, but it also releases X-rays. “Again, if this monster was at the center of the Milky Way, it would likely make life on Earth impossible with the huge amounts of X-rays emanating from it,” Wolf said.

Because of its distance and the expansion of space, that light had shifted into the near-infrared during its billions-of-years journey. Wolf and his colleagues spotted the light with the SkyMapper telescope at the ANU Siding Spring Observatory. They then used the Gaia satellite to measure that the object was sitting still, thereby also confirming that it was incredibly distant and likely a supermassive black hole, the researchers said. Then, another ANU telescope measured the wavelengths released from the object to verify its composition.

“We don’t know how this one grew so large, so quickly in the early days of the universe,” Wolf said. “The hunt is on to find even faster-growing black holes.”

Wolf added that distant black holes like this one can help scientists study the early universe. Researchers can spot the shadows of other objects in front of the black holes, and their radiation also helps clear away obscuring gas.

With giant new ground-based telescopes currently under construction, scientists will also be able to use bright, distant objects like this voracious black hole to measure the universe’s expansion, the researchers said.

The new work was accepted to the journal Publications of the Astronomical Society of Australia.

BREAKING NEWS: ‘Lost’ Asteroid To Pass Close To Earth Tuesday Evening

An asteroid that was lost by tracking satellites eight years ago has been spotted again as it prepares to make an unnervingly close pass by the Earth on May 15. While the giant space rock is expected to miss the planet, the asteroid will give sky watchers a chance to see the action unfold live online.

On Nov. 30, 2010, astronomers discovered an asteroid that could be as large as one of the Great Pyramids of ancient Egypt. It passed within nine million miles of Earth and then scientists lost track of it as it headed back to the outer solar system.

Asteroid 2010 WC9, which is about 426 feet in diameter, was observed for too short of a time for astronomers to be able to predict when its orbit might bring it back to our neighborhood.

This same asteroid is back and about to buzz by us about 70 times closer (126,000 miles away) than it did eight years ago. That puts it at about half the distance between the Earth and moon, making it one of the closest approaches ever observed by such a sizable asteroid.

London’s Northolt Branch Observatories, which helped to rediscover the asteroid, will be broadcasting the flyby live on Facebook. Don’t worry, the broadcast won’t be like a countdown to the apocalypse. 2010 WC9 will sail by the planet safely at about 6:05 p.m. Eastern Standard Time on May 15.

While this asteroid isn’t a threat (this time) it does emphasize the need to keep a watchful eye on the sky to catalog and track as many space rocks as possible.

“There are lots of asteroids and comets in our solar system and it’s impossible to predict the trajectories of all of these objects, but we need to try,} University of Saskatchewan astronomy professor Daryl Janzen said in a news release on May 10.

Just last month, astronomers discovered a slightly smaller asteroid just hours before it passed by the Earth and came even closer to hitting the moon.

On the cosmic scale, these asteroids are large enough to do some damage if they were to impact Earth, especially near a populated area. However, they aren’t considered big enough to do the kind of catastrophic damage caused by the space rock believed to have wiped out the dinosaurs.

“There is an extremely low probability of the planet coming into contact with one of these large near-Earth objects in our lifetime, but there is really good evidence that it happened in the past and led to mass extinction on the planet,” Janzen added. “So, although the probability is low, it’s important to discover as many NEOs as we can, so that if one does enter into a collision course with Earth, we can try to do something about it.”

Orbital Variations Can Trigger ‘Snowball’ States In Habitable Zones Around Sunlike Stars

Aspects of an otherwise Earthlike planet’s tilt and orbital dynamics can severely affect its potential habitability — even triggering abrupt “snowball states” where oceans freeze and surface life is impossible, according to new research from astronomers at the University of Washington.

The research indicates that locating a planet in its host star’s “habitable zone” — that swath of space just right to allow liquid water on an orbiting rocky planet’s surface — isn’t always enough evidence to judge potential habitability.

Russell Deitrick, lead author of a paper to be published in the Astronomical Journal, said he and co-authors set out to learn, through computer modeling, how two features — a planet’s obliquity or its orbital eccentricity — might affect its potential for life. They limited their study to planets orbiting in the habitable zones of “G dwarf” stars, or those like the sun.

A planet’s obliquity is its tilt relative to the orbital axis, which controls a planet’s seasons; orbital eccentricity is the shape, and how circular or elliptical — oval — the orbit is. With elliptical orbits, the distance to the host star changes as the planet comes closer to, then travels away from, its host star.

Deitrick, who did the work while with the UW, is now a post-doctoral researcher at the University of Bern. His UW co-authors are atmospheric sciences professor Cecilia Bitz, astronomy professors Rory Barnes, Victoria Meadows and Thomas Quinn and graduate student David Fleming, with help from undergraduate researcher Caitlyn Wilhelm.

The Earth hosts life successfully enough as it circles the sun at an axial tilt of about 23.5 degrees, wiggling only a very little over the millennia. But, Deitrick and co-authors asked in their modeling, what if those wiggles were greater on an Earthlike planet orbiting a similar star?

Previous research indicated that a more severe axial tilt, or a tilting orbit, for a planet in a sunlike star’s habitable zone — given the same distance from its star — would make a world warmer. So Deitrick and team were surprised to find, through their modeling, that the opposite reaction appears true.

“We found that planets in the habitable zone could abruptly enter ‘snowball’ states if the eccentricity or the semi-major axis variations — changes in the distance between a planet and star over an orbit — were large or if the planet’s obliquity increased beyond 35 degrees,” Deitrick said.

The new study helps sort out conflicting ideas proposed in the past. It used a sophisticated treatment of ice sheet growth and retreat in the planetary modeling, which is a significant improvement over several previous studies, co-author Barnes said.

“While past investigations found that high obliquity and obliquity variations tended to warm planets, using this new approach, the team finds that large obliquity variations are more likely to freeze the planetary surface,” he said. “Only a fraction of the time can the obliquity cycles increase habitable planet temperatures.”

Barnes said Deitrick “has essentially shown that ice ages on exoplanets can be much more severe than on Earth, that orbital dynamics can be a major driver of habitability and that the habitable zone is insufficient to characterize a planet’s habitability.” The research also indicates, he added, “that the Earth may be a relatively calm planet, climate-wise.”

This kind of modeling can help astronomers decide which planets are worthy of precious telescope time, Deitrick said: “If we have a planet that looks like it might be Earth-like, for example, but modeling shows that its orbit and obliquity oscillate like crazy, another planet might be better for follow-up” with telescopes of the future.”

The main takeaway of the research, he added, is that “We shouldn’t neglect orbital dynamics in habitability studies.”

‘Lost’ Asteroid 2010 WC9 Makes an Unusually Close Flyby of Earth

A jumbo-jet-size asteroid gave Earth a close shave today (May 15), whizzing past our planet at a safe distance of 126,000 miles (203,000 kilometers) — or about half the distance between Earth and the moon.
The asteroid, which is officially designated 2010 WC9, made its closest approach at 6:05 p.m. EDT (2205 GMT) while traveling at a speed of 28,655 mph (46,116 km/h), according to the Minor Planet Center.

Astronomers estimate that the asteroid measures 125 to 390 feet (38 to 119 meters) in diameter. That means it’s about as big as New York City’s Statue of Liberty, though it could be even longer than a football field.

While this isn’t exceptionally large for a near-Earth asteroid, it is rare for asteroids this big to venture so close to Earth. According to EarthSky.org, this was “one of the closest approaches ever observed of an asteroid of this size.”

Asteroid 2010 WC9 was first spotted by the Catalina Sky Survey in 2010, but astronomers lost track of it once it became too faint to see. The “lost” asteroid was rediscovered on May 8, and astronomers have been tracking its approach ever since.

The asteroid isn’t visible to the naked eye, but it can be spotted through some telescopes. Astronomers with The Virtual Telescope Project in Italy and Tenagra Observatories in Arizona captured a view of the asteroid today at 2:46 a.m. EDT (0646 GMT). At the time, the asteroid was about 454,000 miles (730,000 km) from Earth.

The Slooh community observatory has also been tracking the asteroid, and yesterday (May 14), the observatory showed a live webcast of the asteroid as seen from its telescopes at the Institute of Astrophysics of the Canary Islands.