Posted on by Nancy Atkinson

Sneak Attacks from the Sun

This image combines all of STEREO's wavelengths into one three-dimensional photograph (visible with 3D anaglyph glasses). Credit: NASA

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From a Harvard Smithsonian Center for Astrophysics press release:

Our Sun can be a menace when it sends out powerful solar blasts of radiation towards the Earth. Astronomers keenly watch the Sun to learn more about what powers these solar eruptions, in hopes of being able to predict them. New research shows that one-third of the Sun’s blasts are “sneak attacks” that may occur without warning.

“If space weather forecasters rely on some of the traditional danger signs, they’ll miss a significant fraction of solar eruptions,” said Suli Ma of the Harvard-Smithsonian Center for Astrophysics (CfA).

To reach their conclusion, Ma and her colleagues studied 34 solar eruptions over 8 months using the STEREO spacecraft. STEREO allows us to study the Sun from two different angles simultaneously. It consists of two spacecraft, one ahead of Earth in its orbit and the other trailing behind. The researchers used it to ensure that the events leaving the Sun were definitely on the side facing the Earth.

STEREO is ideal for studying coronal mass ejections, or CMEs. A CME is a huge eruption from the Sun that blasts a billion tons of highly charged particles into space at speeds greater than a million miles per hour. When those charged particles reach Earth, they interact with our planet’s magnetic field, potentially creating a geomagnetic storm. Such a storm can interfere with satellite communications, disrupt power grids, or even short out orbiting satellites.

Previous to STEREO, astronomers thought that all Earth-facing CMEs were accompanied by warning signals like flares (smaller explosions accompanied by high-energy radiation), coronal dimmings (darkening of the corona caused by discharge of matter in the CME) or filament eruptions (long ribbons of plasma arching violently out from the solar surface). Therefore, by watching for those signals, we could potentially predict an impending eruption.

This new research found that 11 of the 34 CMEs observed by STEREO were “stealthy,” showing none of the usual signals. As a result, any system designed to watch for such warning signs could miss one-third of all solar blasts.

“Meteorologists can give days of warning for a hurricane, but only minutes for a tornado,” explained Smithsonian astronomer Leon Golub. “Currently, space weather forecasting is more like tornado warnings. We might know an eruption is imminent, but we can’t say exactly when it will happen. And sometimes, they catch us by surprise.”

The team plans to continue looking for subtle clues that might allow us to predict an impending “stealth” CME. They caution that their study occurred during a prolonged minimum of solar activity; conditions may change as solar activity increases over the next few years.

“The Sun is entering its stormy season, ramping up toward its next period of maximum activity in 2013 and 2014,” said Ma. “The more we learn and understand about it now, the better.”

The paper discussing their findings appeared in the Oct. 10, 2010 issue of The Astrophysical Journal. It was authored by Suli Ma, G. Attrill, and Leon Golub (CfA); and J. Lin (Chinese Academy of Sciences).

Posted on by Nicholos Wethington

Breaking News: Watch A Gigantic Looping Solar Prominence

As of 18:49 UT, a gigantic solar prominence was visible to the Solar Dynamics Observatory in the ultraviolet spectrum. Image Credit: SDO

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The Solar Dynamics Observatory never fails to deliver absolutely stunning images from the Sun: as of 18:49 UT today, the above picture is what the Sun looked like in the ultraviolet spectrum. The prominence that you are seeing looping off the Sun is estimated at over 700,000 km across, which is about the radius of the entire Sun. Amazing!

You can head over to the Solar Dynamics Observatory site to watch this gigantic loop of solar plasma develop in real time.

There’s nothing to worry about here on Earth, though – we are safe from such activity on the Sun, even if that prominence is big enough swallow up thousands of Earths. There is no coronal-mass ejection or flare to go along with this prominence, both phenomena on the Sun that can reach Earth and mess with satellites and our power grid.

As you can see (or rather, not see) in this visible light image below, the flare seems to only be visible in the ultraviolet. Other spectra of the Sun as imaged by the SDO are available here. Why is this? Phil Plait, the Bad Astronomer, explains it best:

“In visible light, the light from the extremely thin material in the prominence is totally overwhelmed by the intense emission from the Sun’s surface, and is invisible. It’s only when we filter out most of the Sun’s light (and let through light specifically given off by the plasma in the prominence) that we can see it at all,” he wrote.

The Sun in the visible light spectrum, as seen from SDO at 18:00 UT. The two visible sunspots seem to be unrelated to this large prominence. Image Credit: SDO

This video shows the buildup up this most recent spectacular solar show, as this portion of the Sun comes into view from a 48-hour period between December 4th and 6th:

[UPDATE]: Here is a video that shows the prominence eruption as it expanded:

Spaceweather.com also has some other fantastic images that are linked to on their front page. Prominences like this can come crashing down quickly when they become unstable, so head over to the SDO site to watch the action as it develops!

Source: The Bad Astronomer, SDO

Posted on by Nancy Atkinson

Aurora Alert! Solar Flare Heading Our Way

This image shows a three and a half hour (0000 - 0330 UT) time lapse movie of the flare and filament event. Credit: NASA/SDO

An active sunspot (1123) erupted early this morning (Nov. 12th), producing a C4-class solar flare and apparently hurling a filament of material in the general direction of Earth. Coronagraph images from the Solar and Heliospheric Observatory (SOHO) and NASA’s twin STEREO spacecraft show a faint coronal mass ejection emerging from the blast site and heading off in a direction just south of the sun-Earth line. The cloud could deliver a glancing blow to Earth’s magnetic field sometime between Nov. 13th to the 15th. High latitude sky watchers could see auroras on those dates.
Continue reading “Aurora Alert! Solar Flare Heading Our Way”

Posted on by Mark Thompson

Solar Explosions Spark Controversy

Solar Prominence

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Nowhere in the Solar System are conditions more extreme than the Sun. Every second it converts millions of tons of matter into energy to create the intense levels of heat and light we expect of our local star. Study the Sun in different wavelengths and its violent nature can really become apparent. The STEREO satellite has been studying the Sun at a wavelength of 304Å and the results support a controversial solar theory.

Coronal Mass Ejections (or CMEs) are common on the Sun and they have a very real impact to us here on Earth. The solar explosions expel trillions of trillions of tons of super hot hydrogen gas into space, sometimes in the direction of the Earth. Traveling at speeds up to 2,000 kilometers per second it takes just a day for the magnetized gas to reach us and on arrival it can induce strong electric currents in the Earth’s atmosphere leading not only to the beautiful auroral displays but also to telecommunication outages, GPS system failures and even disturbances to power grids.

Solar flares, to use their other name, were first observed back in 1859 and since then, scientists have been studying them to try to understand the mechanism that causes the eruption. It has been known for some time that the magnetically charged gas or plasma is interacting with the magnetic field of the Sun but the detail has been at best, elusive.

In 2006, the international satellite STEREO was launched with the objective of continuously monitoring and studying the CMEs as they head toward the Earth and its data has helped scientists at the Naval Research Laboratory (NRL) in Washington, D.C., start to understand the phenomenon.

Using this new data, scientists at the NRL compared the observed activity with a controversial theory that was first proposed by Dr James Chen (also from the NRL) in 1989. His theory suggested that the erupting clouds of plasma are giant ‘magnetic flux ropes’, effectively a twisted up magnetic field line shaped like a donut. The Sun being a vast sphere of gas suffers from differential rotation where the polar regions of the Sun and the equatorial regions all rotate at different speeds. As a direct result of this, the plasma ‘drags’ the magnetic field lines around and the Sun and it gets more and more twisted up . Eventually, it bursts through the surface, taking some plasma with it giving us one of the most dramatic yet potentially destructive events in the Universe.

Dr Chen and a Valbona Kunkel, a doctorate student at George Mason University, applied Dr. Chen’s model to the new data from STEREO and found that the theory agrees with the measured trajectories of the ejected material. It therefore looks like his theory, whilst controversial may have been right all along.

Its strange to think that our nearest star, the Sun, still has secrets. Yet thanks to the work of Dr. Chen and his team, this one seems to have been unraveled and understanding the strange solar explosions will perhaps help us to minimise impact to Earth based technologies in years to come.

Mark Thompson is a writer and the astronomy presenter on the BBC One Show. See his website, The People’s Astronomer, and you can follow him on Twitter, @PeoplesAstro

Posted on by Jon Voisey

Breaking News: The Sun Worked 175 Years Ago!

The sunspot butterfly diagram. This modern version is constructed (and regularly updated) by the solar group at NASA Marshall Space Flight Center.
The sunspot butterfly diagram. This modern version is constructed (and regularly updated) by the solar group at NASA Marshall Space Flight Center.

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You’ll have to forgive my title. After writing so many articles as moderately as I could, I couldn’t help but engage in a bit of sensationalism of my own, especially in the interest of sarcasm. Although it’s not especially exciting that the sun has indeed been working for nearly two centuries (indeed, much longer than that), what is interesting is how using historical data, scientists have confirmed that process we see today have been relatively consistent since 1825.


The observations revolve around a familiar diagram known as the Butterfly diagram (pictured above). This diagram depicts the position of sunspots at various latitudes on the sun’s surface as time progresses. At the beginning of a cycle, sunspots start of at high latitudes and as the cycle progresses, appear at lower and lower latitudes until they disappear and the cycle repeats. The pattern formed resembles the wings of a butterfly, thereby giving the diagram its name.

Although sunspots have been observed as far back as 364 BC by Chinese astronomers, telescopic observations of them did not start until the early 1600’s. Continuous observation of the sun and its spots started in 1876 at the Royal Greenwich Observatory. There Edward Maunder recognized the pattern of sunspots and published them in the format that is the now famous Butterfly diagram in 1904. The diagram, as its usually shown only comprises data starting from around 1876 and continuing until present day. But the use of new records have extended the diagram back an additional 51 years, covering four new solar cycles. Although many observations exist with total sunspot counts, this new set of data includes detailed documentation of the position of the spots on the solar disc.

The observations were created by German astronomer Heinrich Schwabe. Originally an apothecary, he won a telescope in a lottery in 1825 and was fascinated, selling his family business four years later. Schwabe observed the Sun compulsively attempting to discover a new planet with an orbit interior to Mercury by witnessing it transiting the Sun. Although this effort was doomed to failure, Schwabe maintained detailed records of the sunspots. He even recognized the pattern of spots occurred in an 11 year cycle and published the discovery in 1843. It was met with little attention for several years until it was included in Alexander von Humboldt’s Kosmos. Due to this discovery, the 11 year solar cycle is also referred to as the Schwabe cycle.

From 1825 until 1867, Schwabe compiled at least 8468 observations of the Sun’s disc, drawn on 5cm circles. On his death, these documents, as well as the rest of his scientific works, were donated to the Royal Astronomical Society of London, and in 2009, were provided to a team of researchers for digitization. From the 8468 drawings, 7299 “have a coordinate system which is found to be aligned with the celestial equator” making them suitable for translation into scientific data.

Thus far, the team has converted 11% of the images into usable data and already, it has created a detailed butterfly diagram preceding those produced elsewhere. From it, the astronomers undertaking the conversion have made some interesting observations. The cycle beginning around 1834 was weaker than others around that time. The following one, starting around 1845, displayed a notable asymmetry where sunspots in the southern hemisphere were conspicuously lacking for the first 1-2 years of the cycle, whereas most cycles are fairly well mirrored. Although unusual, such phase shifts are not unprecedented. In fact, another study using historical records has demonstrated that, for the last 300 years, one hemisphere has always led (although not usually so greatly) for several cycles before trading off.

As with the recently discussed historical project on weather trends this reanalysis of historical data is one of many such projects giving us a broader picture of the trends we see today and how they have changed over time. While undoubtedly, many will be demonstrated to be mundane and familiar, undeserving of the exaggerated significance of my title, this is how science works: by expanding our knowledge to test our expectations.

NOTE: I’d Emailed the team asking for permission to show their image of the historical butterfly diagram, but since I haven’t gotten permission, I didn’t reproduce it here. But you can still view it in the paper. Go do so. It’s awesomely familiar.

Posted on by Nicholos Wethington

NASA to Send a Probe Into the Sun

An artist's impression of the Solar Probe Plus satellite, which will fly into the corona of the Sun to get an unprecedented look at how our Sun works. Image Credit: NASA

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NASA recently announced its choices for the experiments to fly aboard the Solar Probe Plus spacecraft, which is slated to launch no later than 2018. This spacecraft will perform the unprecedented task of flying into the Sun’s atmosphere – or corona – to take measurements of the plasma, magnetic fields and dust that surround our nearest star. It will be the first human-made satellite to approach the Sun at such a close proximity.

The previous record-holder for a spacecraft that approached the Sun was Helios 2, which came within 27 million miles (43.5 million kilometers) of the Sun in 1976. Solar Probe Plus will shatter that record, flying to 3.7 million miles (5.9 million kilometers) of the Sun’s surface at its closest approach. In flying so close to the Sun, the spacecraft will be able to get amazingly detailed data on the structure of the atmosphere that surrounds the Sun.

As you can imagine, it gets a little toasty as one gets that close to the Sun. Solar Probe Plus will utilize a special heat shield made of an 8-foot (2.4 m), 4.5 inch (11 cm)-thick special carbon-composite foam plate that will protect the craft from temperatures of up to 2600 degrees Fahrenheit (1400 degrees Celsius) and intense solar radiation. The heat shield is a modified version of that which was used in the MESSENGER mission to Mercury.

NASA has chosen five science projects out of the thirteen that were proposed since 2009. The selected proposals are, according to the press release:

— Solar Wind Electrons Alphas and Protons Investigation: principal investigator, Justin C. Kasper, Smithsonian Astrophysical Observatory in Cambridge, Mass. This investigation will specifically count the most abundant particles in the solar wind — electrons, protons and helium ions — and measure their properties. The investigation also is designed to catch some of the particles in a special cup for direct analysis.
— Wide-field Imager: principal investigator, Russell Howard, Naval Research Laboratory in Washington. This telescope will make 3-D images of the sun’s corona, or atmosphere. The experiment actually will see the solar wind and provide 3-D images of clouds and shocks as they approach and pass the spacecraft. This investigation complements instruments on the spacecraft providing direct measurements by imaging the plasma the other instruments sample.
— Fields Experiment: principal investigator, Stuart Bale, University of California Space Sciences Laboratory in Berkeley, Calif. This investigation will make direct measurements of electric and magnetic fields, radio emissions, and shock waves that course through the sun’s atmospheric plasma. The experiment also serves as a giant dust detector, registering voltage signatures when specks of space dust hit the spacecraft’s antenna.
— Integrated Science Investigation of the Sun:principal investigator, David McComas of the Southwest Research Institute in San Antonio. This investigation consists of two instruments that will take an inventory of elements in the sun’s atmosphere using a mass spectrometer to weigh and sort ions in the vicinity of the spacecraft.
— Heliospheric Origins with Solar Probe Plus: principal investigator, Marco Velli of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. Velli is the mission’s observatory scientist, responsible for serving as a senior scientist on the science working group. He will provide an independent assessment of scientific performance and act as a community advocate for the mission.

Two important questions that the mission hopes to answer is the perplexing mystery of why the Sun’s atmosphere is hotter than its surface, and the mechanism for the solar wind that emanates from the Sun into the Solar System. The spacecraft will have a front-row seat to watch the solar wind speed up from subsonic to supersonic speed.

Because of the conservation of momentum, it takes a lot of slowing down to send a spacecraft towards the Sun. The Earth and objects on the Earth are traveling around the Sun at an average of 30 kilometers per second (67,000 miles per hour). So, to slow the spacecraft down enough to get it close to the Sun, it will have to fly around Venus seven times! This is the opposite of a gravity assist, or “slingshot”, in which a satellite gains energy by flying by a planet. In the case of Solar Probe Plus, as well as that of MESSENGER, multiple flybys of Venus imparts some of the craft’s energy to Venus, thereby slowing down the spacecraft.

The Solar Probe Plus mission is part of NASA’s “Living With a Star Program”, of which the Solar Dynamics Observatory is also a mission. This program is designed to study the impact our Sun has on the space environment of the Solar System, and acquire data to better equip future space missions.

Source: NASA press release, APL mission site

Posted on by Jon Voisey

The Race to Stellar Formation

The Cosmic Web - NGC 2070 by Joseph Brimacombe

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Racing is rarely the term that comes to mind when one considers astronomy. However, many events are a race to reach stability before a system flies apart or implodes. The formation of stars from gigantic interstellar clouds is just such a race in which stars struggle to form before the cloud is dispersed. Although a rough estimation of the requirements for collapse are discussed in introductory astrophysics classes (See: Jeans Mass Criterion) this formulation leaves out several elements that come into play in the real universe. Unfortunately for astronomers, these effects can be subtle but significant but untangling them is the subject of a recent paper uploaded to the arXiv preprint server.

The Jeans Mass Criterion only takes into consideration a gas cloud in isolation. Whether or not it will collapse will depend on whether or not the density is sufficiently high. But as we know, stars don’t form in isolation; They form in stellar nurseries which form hundreds to thousands of stars. These forming stars contract under self gravity, and in doing so, heat up. This increases the local pressure and slows contraction as well as giving off additional radiation that also affects the cloud at large. Similarly, solar winds (particles streaming from the surface of formed stars) and supernovae can also disrupt further formation. These feedback mechanisms are the target of a new study by a group of astronomers led by Laura Lopez from the University of California Santa Cruz.

To investigate how each feedback mechanism operated, the group selected the Tarantula Nebula (aka, 30 Doradus or NGC 2070), one of the largest star forming regions easily accessible to astronomers since it resides in the Large Magellanic Cloud. This region was selected due to its large angular size which allowed the team to have good spatial resolutions (down to scales smaller than a parsec) as well as being well above the plane of our own galaxy to minimize interference from gas sources in our own galaxy.

To conduct their study, Lopez’s team broke 30 Dor into 441 individual regions to assess how each feedback mechanism worked in different portions of the nebula. Each “box” consisted of a column slicing through the nebula that was a mere 8 parsecs to a side to ensure sufficient quality of the data across the entire spectrum since observations were used from radio telescopes to X-ray and used data from Spitzer and Hubble.

Perhaps unsurprisingly, the team found that different feedback mechanisms played varying roles in different places. Close the the central star cluster (<50 parsecs), radiation pressure dominated the effects on the gas. Further out, pressure from the gas itself played the stronger role. Another potential feedback mechanism was that of “hot” gas being excited by X-ray emission. What the team uncovered is that, although there is a significant amount of this material, the nebula’s density is insufficient to entrap it and allow it to have a large effect on the overall pressure. Rather, they described this portion as “leaking out of the pores”.

This research is some of the first to observationally explore, on a large scale, many of the mechanisms that have been proposed by theorists in the past. Although such research may seem inconsequential, these feedback mechanisms will have large effects on the distribution of stellar masses (known as the Initial Mass Function). This distribution determines which the relative amounts of massive stars which help to create heavy elements and drive the chemical evolution of galaxies as a whole.

Posted on by Nancy Atkinson

Sound Waves from Distant Star Reveal Magnetic Solar Cycle

The COROT spacecraft. Credits: CNES/D. Ducros

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Astronomers have been able to monitor a the sound waves of a star 100 light years away and found a magnetic cycle analogous to our Sun’s solar cycle. “Essentially, the star is ringing like a bell,” says scientist Travis Metcalfe from the National Center for Atmospheric Research, a co-author of the new study. “As it moves through its starspot cycle, the tone and volume of the ringing changes in a very specific pattern, moving to higher tones with lower volume at the peak of its magnetic cycle.”

The team examined the star’s acoustic fluctuations, using a technique called stellar seismology. The team hopes to assess the potential for other stars in our galaxy to host planets, including some perhaps capable of sustaining life.

“Understanding the activity of stars harboring planets is necessary because magnetic conditions on the star’s surface could influence the habitable zone, where life could develop,” says CEA-Saclay scientist Rafael Garcia, the study’s lead author.

The scientists studied a star known as HD49933, which is located 100 light years from Earth in the constellation Monoceros, just east of Orion. By stellar seismology, they detected the signature of “starspots,” areas of intense magnetic activity on the surface that are similar to sunspots. While scientists have previously observed these magnetic cycles in other stars, this was the first time they have discovered such a cycle using this method.

“We’ve discovered a magnetic activity cycle in this star, similar to what we see with the Sun,” says co-author and NCAR scientist Savita Mathur. “This technique of listening to the stars will allow us to examine potentially hundreds of stars.”

HD49933 is much bigger and hotter than the Sun, and its magnetic cycle is much shorter. Whereas past surveys of stars have found cycles similar to the 11-year cycle of the Sun, this star has a cycle of less than a year.

Studying many stars with stellar seismology could help scientists better understand how magnetic activity cycles can differ from star to star, as well as the processes behind such cycles. The work could especially shed light on the magnetic processes that go on within the Sun, furthering our understanding of its influence on Earth’s climate. It may also lead to better predictions of the solar cycle and resulting geomagnetic storms that can cause major disruption to power grids and communication networks.

The scientists examined 187 days of data captured by the international Convection Rotation and Planetary Transits (CoRoT) space mission.

This short cycle is important to scientists because it may enable them to observe an entire cycle more quickly, thereby gleaning more information about magnetic patterns than if they could only observe part of a longer cycle.

Source: NCAR

Posted on by Nancy Atkinson

Amazing Sunspot Image from New Solar Telescope

The most detailed sunspot ever obtained in visible light was seen by new telescope at NJIT's Big Bear Solar Observatory. Credit: Big Bear Solar Observatory

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A new type of adaptive optics for solar observations has produced some incredible results, providing the most detailed image of a sunspot ever obtained in visible light. A new telescope built by the New Jersey Institute of Technology’s Big Bear Solar Observatory has seen its ‘first light’ using a deformable mirror, which is able to reduce atmospheric distortions. This is the first facility-class solar observatory built in more than a generation in the U.S.

The New Solar Telescope (NST) is located in the mountains east of Los Angeles. It has 97 actuators that make up the deformable mirror. By the summer of 2011, in collaboration with the National Solar Observatory, BBSO will have upgraded the current adaptive optics system to one utilizing a 349 actuator deformable mirror. The telescope has a 1.6 m clear aperture, with a resolution covering about 50 miles on the Sun’s surface.

The NST will be the pathfinder for an even larger ground-based telescope, the Advanced Technology Solar Telescope to be built over the next decade. Philip R. Goode from NJIT is leading a partnership with the National Solar Observatory (NSO) to develop a new and more sophisticated kind of adaptive optics, known as multi-conjugate adaptive optics. This new optical system will allow the researchers to increase the distortion-free field of view to allow for better ways to study these larger and puzzling areas of the Sun, and a 4-meter aperture telescope will be built in the next decade.

Source: NJIT

Posted on by Nancy Atkinson

Amazing Image: Map of Magnetic Field Lines of the Sun

Magnetic field lines on the Sun, on August 20, 2010. Credit: NASA SDO/Lockheed Martin Space Systems Compan

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The Sun’s corona is threaded with a complex network of magnetic fields, and this amazing new image from the Solar Dynamics Observatory shows the magnetic field lines associated with a coronal hole that is now turning to face Earth. This map is from data taken on August 20, 2010 by the Helioseismic and Magnetic Imager instrument (HMI). The magnetic field lines are color coded: white lines show fields that are closed, not releasing solar wind, and gold lines show open fields, letting solar wind escape. Understanding these magnetic fields is important because it is thought that solar storms and flares, which can affect us here on Earth, result from changes in the structure and connections of these fields.

Coronal holes are large regions in the corona that are darker, less dense and cooler than surrounding areas. The open structure of their magnetic field allows a constant flow of high-density plasma to stream out of the holes. There is an increase in the intensity of the solar wind effects on Earth when a coronal hole faces.

During a solar minimum, such as the one from which the Sun is just emerging, coronal holes are mainly found at the Sun’s polar regions, but they can be located anywhere on the sun during solar maximum. The fast-moving component of the solar wind is known to travel along open magnetic field lines that pass through coronal holes.

Scientists are finding out that much of the structure of the Sun’s corona is shaped by the magnetic field. Although it varies over time and from place to place on the Sun, the Sun’s magnetic field can be very strong. Inside sunspots, the magnetic field can be several thousand times the strength of the Earth’s magnetic field.

Learn more about magnetic field lines and how SDO’s HMI instrument will help us to better understand the Sun in this video from SDO:

More info: HMI webpage, SDO website

Sources: @Camilla_SDO Twitpic page, SDO Facebook, Solar Physics page from Montana University