Posted on by Tammy Plotner

Meteor Shower Points Towards Undiscovered Earthbound Comet

This February Eta Draconid was filmed by Peter Jenniskens with one of the low-light-level video cameras of the Cameras for Allsky Meteor Surveillance (CAMS) station in Mountain View, California, at 07:59:24 UT on February 4, 2011. CREDIT: All Sky Cameras/Peter Jenniskens

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With the annual Perseid Meteor Shower already underway, we’re looking to the skies and thinking about what causes these celestial fireworks. We know for the most part that meteor showers are the by-product of comets, but what happens when seemingly random meteors become not so random? The answer is a long term comet which could be pointed right at Earth.

Comets don’t just wander through the Solar System. They take very specific paths around the Sun and when its orbit passes close to ours, we get visual clues in the form of a meteor shower. Long term comets are in no hurry. Their elliptical sojourns can take anywhere from 200 to 10,000 years to complete – with a dense dust trail leading the way. We compute when and where the comet comes from by its orbital period, but what happens if that orbital period leads to a new discovery? And what happens if that comet’s orbit seems destined to encounter us? We just might get some advance warning from monitoring an unexpected meteor shower.

“Such meteor showers are extremely rare. They happen only about once or twice every sixty years, when the thin meteoroid stream is exactly in Earth’s path at the time when Earth arrives at that spot.” says Peter Jenniskens (SETI Institute) and Peter S. Gural (SAIC). “Because they are so rare, many of these showers remain to be discovered. Here, we report that one such shower, previously unknown, just showed up on February 4, 2011.”

Thanks to the use of the new NASA-sponsored network of low-light video cameras called the Cameras for Allsky Meteor Surveillance (CAMS) project, more than three hundred “new” meteor showers documented by the IAU Working List of Meteor Showers are under investigation. The February 4 occurrence centered around Eta Draconis came as a surprise, but the observing team of three separate stations went to work confirming the meteoroid orbital elements. The event lasted around seven hours and was confirmed through astrometric tracks for all moving objects in all cameras that recorded that night and with radio reflections during that day taken in Finland.

“The similarity of the orbits implies that the February eta Draconids are a dynamically young stream. The orbital period suggests a long-period comet, perhaps a Halley-type comet. If this indeed is a long-period comet dust trail, then the dust was ejected in the previous return to the Sun.” says Jenniskens and Gural. “Such dust trails get perturbed enough on the way in that the orbital periods change dramatically and dust trail sections catch up on each other, spreading out into a more diffuse stream already after one orbit.”

Oddly enough, no meteoritic activity from this new stream was recorded either before or after its February 4th apparition… nor was it active between 2007 through 2009. The conclusion is that it’s caused by the dust trail of a long period comet and it has formally been named the February Eta Draconids. What long term comet does the stream belong to? Well, the answer to that question is still up in the air and a good point to ponder while viewing this year’s Perseids.

“This is an important discovery, because it points to the presence of a potentially hazardous comet. If the dust trail can hit the Earth, so can the comet: the planetary perturbations do not depend on the mass of the object.” says the team. “Of course, an impact will occur only if the comet orbit is perturbed into Earth’s path right at the time when Earth passes by the comet orbit on February 4. It is in principle possible to guard against such impacts by looking along the comet orbit to those spots where the comet would be in such a dangerous position. In that way, perhaps a few years of warning could be provided.”

Original New Story: Space.Com.

Posted on by Tammy Plotner

HARPS Tunes In On “Noisy” Planets

Montage of the HARPS spectrograph and the 3.6m telescope at La Silla. The upper left shows the dome of the telescope, while the upper right illustrates the telescope itself. The HARPS spectrograph is shown in the lower image during laboratory tests. The vacuum tank is open so that some of the high-precision components inside can be seen. Credit: European Southern Observatory

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Able to achieve an astounding precision of 0.97 m/s (3.5 km/h), with an effective precision of the order of 30 cms-1, the High Accuracy Radial velocity Planet Searcher (HARPS) echelle spectrograph has already discovered 16 planetary objects in the southern hemisphere and has now logged four more. And that’s only the beginning…

“A long-period companion, probably a second planet, is also found orbiting HD7449. Planets around HD137388, HD204941, and HD7199 have rather low eccentricities (less than 0.4) relative to the 0.82 eccentricity of HD7449b. All these planets were discovered even though their hosting stars have clear signs of activity.” says X. Dumusque (et al). “Solar-like magnetic cycles, characterized by long-term activity variations, can be seen for HD137388, HD204941 and HD7199, whereas the measurements of HD7449 reveal a short-term activity variation, most probably induced by magnetic features on the stellar surface.”

Using radial velocity is currently the preferred method for detecting new planets. But, despite the quality of the equipment, low mass planets placed at a great distance from the host star become problematic because of the star’s own “noise”. RV is an indirect method which utilizes the presence of star wobble to spot orbiting bodies. Unfortunately, normal star activity such as magnetic cycles, spots and plagues can produce similar signals, but now long term variables like these are being fine tuned into the equation.

“The planets announced in this paper for the first time have been discovered even though their host stars display clear signs of activity. We have found that HD7449 exhibits signs of short term activity, whereas HD7199, HD137388, and HD204941 have solar-like magnetic cycles.” says Dumusque. “When examining the RVs and the fitted planets for HD7199, HD137388, and HD204941, it is clear that magnetic cycles induce RV variations that could be misinterpreted as long-period planetary signature. Therefore, the long-term variations in the activity index have to be studied properly to distinguish between the real signature of a planet and long-term activity noise.”

The paper then goes on to explain our Sun should show RV variations of 10ms?1 over its cycle and that it is typical behavior for solar-like stars. Perhaps all stars which display magnetic cycles also have long-term RV variations? “The high precision HARPS sample, composed of 451 stars, provides a good set of measurements to search for this activity-RV correlation.” says Lovis (et al). “A more complete study is in progress and will be soon published.”

Factual Information Courtesy of Wikipedia. Further Reading: The HARPS search for southern extra-solar planets. XXX. Planetary systems around stars with solar-like magnetic cycles and short-term activity variation.

Posted on by Tammy Plotner

Searching For Gravitational Waves

Two-dimensional representation of gravitational waves generated by two neutron stars surrounding each other. Credit: NASA

[/caption]Colliding neutron stars and black holes, supernova events, rotating neutron stars and other cataclysmic cosmic events… Einstein predicted they would all have something in common – oscillations in the fabric of space-time. This summer European scientists have joined forces to prove Einstein was right and capture evidence of the existence of gravitational waves.

Europe’s two ground-based gravitational wave detectors GEO600 (a German/UK collaboration) and Virgo (a collaboration between Italy, France, the Netherlands, Poland and Hungary) are underway with a joint observation program which will continue over the summer, ending in September 2011. The detectors consist of a pair of joined arms placed in a horizontal L-shaped configuration. Laser beams are then passed down the arms. Suspended under vacuum at the ends of the arms is a mirror which returns the beam to a central photodetector. The detectors work by measuring tiny changes (less than the diameter of a proton), caused by a passing gravitational wave, in the lengths (hundreds or thousands of meters). The periodic stretching and shrinking of the arms is then recorded as interference patterns.

Much like our human ears are able to distinguish the direction of sound from being spaced apart, so having interferometers placed at different locations benefits the chances of picking up a gravitational wave signal. By placing receivers at a distance, this also helps to eliminate the chances of picking up a mimicking terrestrial signal, since it would be unlikely for it to have the same characteristics at two locations while a genuine signal would remain the same.

“If you compare GEO600 and Virgo, you can see that both detectors have similar sensitivities at high frequencies, at around 600Hz and above”, says Dr Hartmut Grote, a scientist at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) and the Leibniz University in Hannover, Germany. “That makes it very interesting for us to search this band for possible gravitational waves associated with supernovae or gamma-ray bursts that are observed with conventional telescopes.”

Of all phenomena, gamma-ray bursts are expected to be one of the strongest sources of gravitational waves. As the most luminous transient event in the known Universe, this collapse of a supermassive star core into a neutron star or black hole may be the most perfect starting point for the search. As of now, the frequencies will depend on the mass and may extend up to the kHz band. But don’t get too excited, because the nature of gravitational wave signals is weak and chances of picking up on it is low. However, thanks to Virgo’s excellent sensitivity at low frequencies (below 100 Hz), it is a prime candidate for gathering signals from isolated pulsars where the gravitational wave signal frequency should be at around 22Hz.

And we’ll be listening for the results…

Original Story Source: Albert Einstein Institute News.

Posted on by Tammy Plotner

Coming To A Solar System Near You… Super-Earth!

Planetary system of HR 8799 imaged by Marois et al (2010). The central star is of spectral type A with a mass of 1.5 solar-masses at a distance of 128 light-years from the Sun. The planets have the masses of Mb = 7MJ , Mc = Md = 10MJ , and Me = (7?10)MJ , with semimajor axes of 68, 38, 24, and 14.5 AU, respectively. Figure with the permission of NPG.

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It is our general understanding of solar system composition that planets fall into two categories: gas giants like Jupiter, Saturn, Neptune and Uranus… and rocky bodies that support some type of atmosphere like Earth, Mars and Venus. However, as we reach further into space we’re beginning to realize the Solar System is pretty unique because it doesn’t have a planetary structure which meets in the middle. But just because we don’t have one doesn’t mean they don’t exist. As a matter of fact, astronomers have found more than 30 of them and they call this new class of planet a “Super-Earth”.

“Super-Earths, a class of planetary bodies with masses ranging from a few Earth-masses to slightly smaller than Uranus, have recently found a special place in the exoplanetary science.” says Nader Haghighipour of the Institute for Astronomy and NASA Astrobiology Institute, University of Hawaii. “Being slightly larger than a typical terrestrial planet, super-Earths may have physical and dynamical characteristics similar to those of Earth whereas unlike terrestrial planets, they are relatively easier to detect.”

Having a super-Earth in the neighborhood opens the avenue towards habitability. Chances are planets of this type have a dynamic core and are able to maintain a type of atmosphere. When combined with being within the habitable zone of a host star, this raises the bar towards possible life on other planets.

“It is important to note that the notion of habitability is defined based on the life as we know it. Since Earth is the only habitable planet known to humankind, the orbital and physical characteristics of Earth are used to define a habitable planet.” says Haghighipour. “In other words, habitability is the characteristic of an environment which has similar properties as those of Earth, and the capability of developing and sustaining Earthly life.”

But being a super-Earth means that there is a lot more going on than just being in the zone. To qualify it must meet three requirements: its composition, the manifestation of plate tectonics, and the presence of a magnetic field. For the first, the presence of liquid water is a high priority. In order to determine this possibility the values of its mass and radius have to be known. To date, two super-Earth planets for which these values have been determined – CoRoT-7b and GJ 1214b – have given us fascinating numerical modeling to help us better understand their composition. Plate tectonics also plays a role through geophysical evolution – just as the presence of a magnetic field has been considered essential for habitability.

“Whether and how magnetic fields are developed around super-Earths is an active topic of research.” notes Haghighipour. “In general, in order for a magnetic field to be in place around an Earth-like planet, a dynamo action has to exist in the planet’s core.”

Last, but not least, comes an atmosphere – the “presence of which has profound effects on its capability in developing and maintaining life.” From its chemical properties we can derive the “planet’s possible biosignatures” as well as the chemicals which formed it. Atmosphere means environment and all of this leads back to being within a habitable zone and of sufficient gravity to keep atmospheric molecules from escaping. Says Haghighipour, “It would not be unrealistic to assume that super-Earths carry gaseous envelopes. Around low-mass stars, some of such atmosphere-bearing super-Earths may even have stable orbits in the habitable zones of their host stars.”

Has a super-Earth been detected? You betcha’… and studied right down to its spectral signature. “The recently detected super-Earth GL 581 g with its possible atmospheric circulation in the habitable zone of its host star may in fact be one of such planets.” says Haghighipour. “More advanced telescopes are needed to identify the biosignatures of these bodies and the physical and compositional characteristics of their atmospheres.”

Further Reading: Super-Earths: A New Class of Planetary Bodies.

Posted on by Tammy Plotner

96 New Reasons To Love Star Clusters

Using data from the VISTA infrared survey telescope at ESO’s Paranal Observatory, an international team of astronomers has discovered 96 new open clusters hidden by the dust in the Milky Way. Thirty of these clusters are shown in this mosaic. The images are made using infrared light in the following bands: J (shown in blue), H (shown in green), and Ks (shown in red). Credit: ESO/J. Borissova

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“Ninety-six clusters of stars in the sky…. Ninety-six clusters of stars… You take one down and pass it around…” Do you need ninety-six new reasons to love astronomy? Then you’re going to want to hear about all the new discoveries the VISTA infrared survey telescope at ESO’s Paranal Observatory has made. Read on…

An international team of astronomers has taken observations to the next level with their discovery of 96 new star clusters which have been hidden behind the dusty cloak of interstellar matter. By utilizing sensitive infrared detectors and the world’s largest survey telescope, the intrepid crew set a new record for finding so many faint and small clusters at one time.

“This discovery highlights the potential of VISTA and the VVV survey for finding star clusters, especially those hiding in dusty star-forming regions in the Milky Way’s disc. VVV goes much deeper than other surveys,” says Jura Borissova, lead author of the study.

As astronomy enthusiasts well know, there’s more to a galactic cluster than just a pretty grouping of stars. Age, relation and motion all play a role. Some are loose groupings – held together by mutual gravitational attraction. Others are torn apart through interactions. Still others are in the process of formation, caught in the act with their gases showing. Yet all share a common denominator: they are around few hundred million years old and they are the by-product of a galaxy with active star formation.

“In order to trace the youngest star cluster formation we concentrated our search towards known star-forming areas. In regions that looked empty in previous visible-light surveys, the sensitive VISTA infrared detectors uncovered many new objects,” adds Dante Minniti, lead scientist of the VVV survey.

Once the grouping has been discovered, classification comes next. Through the use of specialized computer software, the team was able to separate foreground stars from genuine cluster components. Observation then came into play as stellar members were counted, sizes estimated, distances computed and extinction taken into consideration.

“We found that most of the clusters are very small and only have about 10–20 stars. Compared to typical open clusters, these are very faint and compact objects — the dust in front of these clusters makes them appear 10,000 to 100 million times fainter in visible light. It’s no wonder they were hidden,” explains Radostin Kurtev, another member of the team.

Since antiquity only 2500 open clusters have been found in the Milky Way, but astronomers estimate there might be as many as 30,000 still hiding behind the dust and gas. That means these new 96 open clusters could be only the very beginning of a host of new discoveries. “We’ve just started to use more sophisticated automatic software to search for less concentrated and older clusters. I am confident that many more are coming soon,” adds Borissova.

Until then we’ll just “Take one down and pass it around… 29,999 clusters of stars in the sky.”

Original Story Source: ESO Press Release.

Posted on by Tammy Plotner

“Snow White” or “Rose Red” (2007 OR10)

An artist's conception of 2007 OR10, nicknamed Snow White. Astronomers suspect that its rosy color is due to the presence of irradiated methane. [Credit: NASA]

Discovered in 2007 by former graduate student Meg Schwamb, dwarf planet Snow White orbits at the edge of the Solar System. Roughly half the size of Pluto, its color was nicknamed erroneously. At one time it was surmised the diminutive planet was a white, icy world broken away from a larger planet, but further studies show it may be the most red of all.

Astronomers at the California Institute of Technology (Caltech) have been taking a much closer look at dwarf planet 2007 OR10. This Kuiper Belt Object is a frozen world, covered in water ice which may have originated volcanically. While the slush covered rock could be assumed to be white, a more rosy hue is in order. Why? According to the new research, Snow White may have a thin atmosphere of methane that’s methodically dissipating.

“You get to see this nice picture of what once was an active little world with water volcanoes and an atmosphere, and it’s now just frozen, dead, with an atmosphere that’s slowly slipping away,” says Mike Brown, the Richard and Barbara Rosenberg Professor and professor of planetary astronomy, who is the lead author on a paper to be published in the Astrophysical Journal Letters describing the findings. “With all of the dwarf planets that are this big, there’s something interesting about them—they always tell us something,” Brown says. “This one frustrated us for years because we didn’t know what it was telling us.”

When dwarf planet 2007 OR10 was first discovered, the best instrument at the time for study was the Near Infrared Camera (NIRC) at the Keck Observatory. But, it wouldn’t be long until Adam Burgasser, a former graduate student of Brown’s and now a professor at UC San Diego, helped design a new instrument called the Folded-port Infrared Echellette (FIRE) to study Kuiper Belt Objects. Last fall, Brown, Burgasser, and postdoctoral scholar Wesley Fraser put FIRE to the test with the 6.5-meter Magellan Baade Telescope in Chile to take a closer look at Snow White. As they had surmised, the little planet was red – but what they weren’t expecting was the presence of water ice. “That was a big shock,” Brown says. “Water ice is not red.”

Is Snow White alone in its rose garden? The answer is no. A few years earlier Brown also discovered another dwarf planet – Quaoar – which had both a red spectrum and water ice. Because of its small size, Quaoar couldn’t hold on to an atmosphere. Over its evolutionary period, the volatile compounds were lost to space, leaving only methane which appears red. Because the spectrum of both small planets are similar, the conclusion is they both share similar properties. “That combination—red and water—says to me, ‘methane,'” Brown explains. “We’re basically looking at the last gasp of Snow White. For four and a half billion years, Snow White has been sitting out there, slowly losing its atmosphere, and now there’s just a little bit left.”

But the team is being cautious for now. While findings point to water ice, the presence of methane isn’t yet documented and will need further studies with larger telescopes like Keck. If their hypothesis turns out to be true, Snow White will join Quaoar as one of two dwarfs capable of keeping their volatile natures intact. Next up for the team is renaming 2007 OR10 since “white” no longer describes it. Before the discovery of water ice and the possibility of methane, “2007 OR10” might have sufficed for the astronomy community, since it didn’t seem noteworthy enough to warrant an official name. “We didn’t know Snow White was interesting,” Brown says. “Now we know it’s worth studying.”

Original Story Source: Caltech News Release. For further reading: Mike Brown’s Planets.

Posted on by Tammy Plotner

Alone In The Dark?

This is the portion of sky in which astronomers found the Segue 1 dwarf galaxy. Can you see it? Credit: Marla Geha

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Two years ago, Marla Geha, a Yale University astronomer, Joshua Simon from the Carnegie Institution of Washington, and their colleagues discovered something unusual while studying with the Keck II telescope and information for the Sloan Digital Sky Survey. Their observations turned up a contrasting group of stars which all appeared to be moving in unison – not just a moving cluster of similar stars which could have been torn away from the nearby Sagittarius dwarf galaxy. The team knew they were on to something, but a competing group of astronomers at Cambridge University was skeptical. Too bad… there was a dark treasure right there before their eyes.

Not to be dissuaded, Simon, Geha and their group returned to Keck and turned the photographic eye of the telescope’s Deep Extragalactic Imaging Multi-Object Spectrograph (DEIMOS) towards their target area. Even though it was only about 1,000 small, dim stars, they wanted to know how they migrated both in respect to the Milky Way and to each other. Named Segue 1, the target the team was looking at could possibly have 3,400 times more mass than can be accounted for by its visible stars… a galaxy dominated by dark matter and salted with a handful of ancient suns. If the 1,000 or so stars were all there was to Segue 1, with just a touch of dark matter, the stars would all move at about the same speed, said Simon. But the Keck data show they do not. Instead of moving at a steady 209 km/sec relative to the Milky Way, some of the Segue 1 stars are moving at rates as slow as 194 kilometers per second while others are going as fast as 224 kilometers per second.

Using the DEIMOS instrument on the Keck II telescope, astronomers could identify which stars were moving together as a group. They are circled here in green Credit: Marla Geha

“That tells you Segue 1 must have much more mass to accelerate the stars to those velocities,” Geha explained. The paper confirming Segue 1’s dark nature appeared in the May 2011 issue of The Astrophysical Journal. “The mass required to cause the different star velocities seen in Segue 1 has been calculated at 600,000 solar masses. But there are only about 1,000 stars in Segue 1, and they are all close to the mass of our Sun,” Simon said. “Virtually all of the remainder of the mass must be dark matter.”

But the information from DEIMOS didn’t stop there… It also revealed an eclectic collection of nearly primordial metal-poor stars. The researchers managed to gather iron data on six stars in Segue 1 with the Keck II telescope, and a seventh Segue 1 star was measured by an Australian team using the Very Large Telescope. Of those seven, three proved to have less than one 2,500th as much iron as the Sun. “That suggests these are some of the oldest and least evolved stars that are known,” said Simon. This is fascinating data considering investigations for stars of this type out of the Milky Way’s billions have produced less than 30. “In Segue 1 we already have 10 percent of the total in the Milky Way,” Geha said. “For studying these most primitive stars, dwarf galaxies are going to be very important.”

By subtracting out all the other objects in the image and leaving the Segue I member stars, the “darkest galaxy” emerges. Credit: Marla Geha

By confirming Segue 1’s massive concentration of dark matter, other types of research into this dark galaxy’s lifestyle now become more dedicated. The space-based Fermi Gamma Ray Telescope has also been looking its way in hopes of catching a gamma-ray event created by the collision and annihilation of pairs of dark matter particles. So far the Fermi telescope has not detected anything of the sort, which isn’t entirely surprising and doesn’t mean the dark matter isn’t there, said Simon.

“The current predictions are that the Fermi telescope is just barely strong enough or perhaps not quite strong enough to see these gamma rays from Segue 1,” Simon explained. So there are hopes that Fermi will detect at least the hint of a collision. “A detection would be spectacular,” said Simon. “People have been trying to learn about dark matter for 35 years and not made much progress. Even a faint glow of the predicted gamma rays would be a powerful confirmation of theoretical predictions about the nature of dark matter.”

Let’s hope Segue 1 isn’t alone in the dark.

Original News Source: Keck Observatory Science News.

Posted on by Tammy Plotner

Chandra Captures Enticing Evidence Of Black Hole’s Bondi Radius

The galaxy NGC 3115 is shown here in a composite image of data from NASA's Chandra X-ray Observatory and the European Southern Observatory's Very Large Telescope (VLT). Credit: X-ray: NASA/CXC/Univ. of Alabama/K.Wong et al, Optical: ESO/VLT

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Those who are interested in black holes are familiar with the event horizon, but the Chandra X-Ray Observatory is giving us an even more detailed look into the structure surrounding these enigmas by imaging the inflowing hot gases. Galaxy NGC 3115 contains a supermassive black hole at its heart and for the first time astronomers have evidence of a critical threshold known as the “Bondi radius”.

Located approximately 32 million light years from the Solar System in the constellation of Sextans, NGC 3115 is a prime candidate for study. Contained in its nucleus is a billion-solar-mass black hole which is stripping away hot gases from nearby stars which can be imaged in X-ray. “The Chandra data are shown in blue and the optical data from the VLT are colored gold. The point sources in the X-ray image are mostly binary stars containing gas that is being pulled from a star to a stellar-mass black hole or a neutron star. The inset features the central portion of the Chandra image, with the black hole located in the middle.” says the team. “No point source is seen at the position of the black hole, but instead a plateau of X-ray emission coming from both hot gas and the combined X-ray emission from unresolved binary stars is found.”

In order to see the machination of the black hole at work, the Chandra team eradicated the signal given off by the binary stars, separating it from the super-heated gas flow. By observing the gas at varying distances the team could then pinpoint a threshold where the gas first becomes impacted by the supermassive black hole’s gravity and begins moving towards the center. This point is known as the Bondi radius.

“As gas flows toward a black hole it becomes squeezed, making it hotter and brighter, a signature now confirmed by the X-ray observations. The researchers found the rise in gas temperature begins at about 700 light years from the black hole, giving the location of the Bondi radius.” says the Chandra team. “This suggests that the black hole in the center of NGC 3115 has a mass of about two billion times that of the Sun, supporting previous results from optical observations. This would make NGC 3115 the nearest billion-solar-mass black hole to Earth.”

Original Story Source: Chandra News Further Reading: Resolving the Bondi Accretion Flow toward the Supermassive Black Hole of NGC 3115 with Chandra.

Posted on by Tammy Plotner

Amber Waves Of Energy

These jets, known as spicules, were captured in an SDO image on April 25, 2010. Combined with the energy from ripples in the magnetic field, they may contain enough energy to power the solar wind that streams from the sun toward Earth at 1.5 million miles per hour. Credit: NASA/SDO/AIA

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Have you ever seen the hot summer wind blow across a ripening field of wheat? If so, you’re familiar with the rippling effect. Now imagine that same crop – only the stalks are 32,000 feet high and on the surface of the Sun. This cascading effect is called Alfvén waves.

Thanks to NASA’s Solar Dynamics Observatory (SDO), we’re now able to see the effect of Alfvén waves, track their movements and see how much energy is being carried along. These new findings have enlightening solar researchers and may be the key to two other enigmatic solar occurrences – the intense heating of the corona to some 20 times hotter than the Sun’s surface and solar winds that blast up to 1.5 million miles per hour.

“SDO has amazing resolution so you can actually see individual waves,” says Scott McIntosh at the National Center for Atmospheric Research in Boulder, Colo. “Now we can see that instead of these waves having about 1000th the energy needed as we previously thought, it has the equivalent of about 1100W light bulb for every 11 square feet of the Sun’s surface, which is enough to heat the Sun’s atmosphere and drive the solar wind.”

Credit: NASA/SDO/AIA

As McIntosh points out in his July 28 Nature article, Alfvén waves are pretty simple. Their movement undulates up and down the magnetic field lines similar to the way a vibration travels along a guitar string. The plasma field enveloping the Sun moves in harmony with the field lines. The SDO can “see” and track this movement. Although the scenario is much more complex, understanding the waves is key to understanding the nature of the Sun-Earth connection and other less clear cut questions such as what causes coronal heating and speeds of the solar wind.

“We know there are mechanisms that supply a huge reservoir of energy at the sun’s surface,” says space scientist Vladimir Airapetian at NASA’s Goddard Space Flight Center in Greenbelt, Md. “This energy is pumped into magnetic field energy, carried up into the sun’s atmosphere and then released as heat.” But determining the details of this mechanism has long been debated. Airapetian points out that a study like this confirms Alfvén waves may be part of that process, but that even with SDO we do not yet have the imaging resolution to prove it definitively.

Hannes Alfvén first theorized the waves in 1942, but it wasn’t until 2007 that they were actually observed. This proved they could carry energy from the Sun’s surface to the atmosphere, but the energy was too weak to account for the corona’s high heat. This study says that those original numbers may have been underestimated. McIntosh, in collaboration with a team from Lockheed Martin, Norway’s University of Oslo, and Belgium’s Catholic University of Leuven, analyzed the great oscillations in movies from SDO’s Atmospheric Imagine Assembly (AIA) instrument captured on April 25, 2010. “Our code name for this research was ‘The Wiggles,'” says McIntosh. “Because the movies really look like the Sun was made of Jell-O wiggling back and forth everywhere. Clearly, these wiggles carry energy.”

The “wiggles” – known as spicules – were then modeled against Alfvén waves and found to be a good match. Once pinpointed, the team could then could analyze the shape, speed, and energy of the waves. “The sinusoidal curves deviated outward at speeds of over 30 miles per second and repeated themselves every 150 to 550 seconds. These speeds mean the waves would be energetic enough to accelerate the fast solar wind and heat the quiet corona.” says the team. “The shortness of the repetition – known as the period of the wave – is also important. The shorter the period, the easier it is for the wave to release its energy into the coronal atmosphere, a crucial step in the process.”

According to preliminary data, the spicules leaped to coronal temperatures of at least 1.8 million degrees Fahrenheit. The pairing of Alfvén waves and heat may just be what it takes to keep the corona at its current temperature… but not enough to cause radiation bursts. “Knowing there may be enough energy in the waves is only one half of the problem,” says Goddard’s Airapetian. “The next question is to find out what fraction of that energy is converted into heat. It could be all of it, or it could be 20 percent of it – so we need to know the details of that conversion.”

More study? You betcha’. And the SDO team is up to the task.

“We still don’t perfectly understand the process going on, but we’re getting better and better observations,” says McIntosh. “The next step is for people to improve the theories and models to really capture the essence of the physics that’s happening.”

Original Story Source: NASA SDO News.

Posted on by Tammy Plotner

Peace In The Light… An Orion Sunset

NGC 2023 - Credit: ESA/Hubble & NASA

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Here the stellar winds are carving out a cavity in a vast reflection nebula. It’s an area of Orion that many of us have seen before – but not like the Hubble Space Telescope reveals it. Located right next door to the famous Horsehead Nebula, NGC 2023 can be glimpsed in a telescope as a tiny patch of light that closely resembles its more famous cousin – the Orion Nebula. Spanning approximately four light years across and located some 1500 light-years from Earth, this awesome visage conjures up a peaceful picture of the setting Sun.

However, there’s no sun slipping beyond a horizon in NGC 2023. Hidden inside is a hot, newborn star illuminating the dusty cloud of gas which is its womb. Radiation pressure runs rampant from this massive young B-type star hidden just outside the edge of this image – its winds blowing the material away from it and forming the fanciful shapes we see. Caught in the act are young proto-stars awaiting their turn to be born.

Unlike our Earthly clouds, the clouds we see here are 5000 times denser than the interstellar medium. It is here where weird green clumps could be Herbig-Haro objects – the product of high-speed gases impacting the diaphanous material and creating shockwaves. Their lives are short – lasting only a few thousand years – but what an image they create! If only they could sing…

“I can’t light no more of your darkness… All my pictures seem to fade to black and white…I’m growing tired and time stands still before me… Frozen here on the ladder of my life.”

Original Story Source: Hubble News Photo Release.