NASA STEREO Probes: Silent now for six weeks

Artist’s conception of one of the Solar TErrestrial RElations Observatory (STEREO) spacecraft. 

Credit: NASA

No one knows exactly why a NASA solar probe stopped talking to Earth six weeks ago, but it's possible the spacecraft is out of power and is drifting without a way of calling for help, the agency said in an update.

On Oct. 1, NASA suddenly lost contact with one of the two Solar TErrestrial RElations Observatory (STEREO) spacecraft, which are currently examining the far side of the Sun.

The probes are considered crucial for solar forecasting, so the loss is a blow. While the STEREO-Behind probe has been mute since then, the agency says "not all hope is lost" for a recovery.

STEREO-Behind went silent after NASA deliberately reset the spacecraft. Along with its twin, STEREO-Ahead, in the coming years the spacecraft will need to reposition its antenna to avoid getting fried by the Sun.

Also, there is a period where each spacecraft will need to work autonomously, because the Sun's radio interference will make it difficult or impossible for communications to get through.

To prepare the spacecraft, NASA has been testing them out ahead of these events, which are called "solar conjunction operations."

STEREO-Ahead passed the tests and entered these operations in August, where it will remain until 2016. STEREO-Behind was supposed to go into this phase on Dec. 1.

Preparations started Sept. 27, when STEREO-Behind was put into the same safe mode test that was used on STEREO-Ahead.

First complete image of the far side of the sun taken on June 1, 2011. Click image for larger version. 

Credit: NASA/STEREO.

"One part of this test was to observe the firing of the spacecraft hard command loss timer, which resets the spacecraft if no commands are received after three days," NASA wrote in an update.

"The purpose of this is to correct any problems that might be preventing the spacecraft from receiving commands from the ground. While the spacecraft is out of contact on the far side of the Sun, this reset will occur every three days."

The timer did fire as planned on Oct. 1, and the spacecraft reset as expected. However, the radio signal coming from STEREO-Behind wasn't as strong as expected. Then, it disappeared altogether.

While there's not much information to work with, NASA says it does know a few things. Before the reset, information or telemetry from the spacecraft showed it was working fine.

After the reset, though, they could tell the inertial measurement unit (IMU) was turned on. This is unusual, and shows that the guidance system's star tracker hadn't picked up its guide stars as expected.

"This is not unexpected, there have been other occasions when it took the star tracker several minutes, or even a few days, to start determining the spacecraft orientation based on star images," NASA said.

An artist’s concept shows both STEREO surrounding the sun on opposite sides. 

Credit: NASA

"In fact, on Sept. 28, as part of the same test sequence, the spacecraft was reset, and it took 12 minutes for the star tracker to start providing an attitude solution."

"When the star tracker is ofline, the spacecraft will automatically turn on the IMU to provide rotational rate information."

NASA thinks the star tracker's struggles would explain why the radio signal wasn't as strong as expected, because the spacecraft's high-gain antenna wasn't aimed at Earth properly.

But there's more, it appears one of the IMU's laser gyroscopes isn't working and is giving "bad data to the attitude control system", NASA said.

So now the spacecraft was facing two failures, which is tough for it to deal with, the agency added.

Deployment of STEREO Spacecraft Panels. 

Credit: 2002-Johns Hopkins University Applied Physics Laboratory. 

Did the spacecraft recognize the problem? If it did, it would have used the last backup system, five solar aspect sensors, which should have made sure the solar panels were pointed in the right direction to provide power.

If not, the spacecraft might have thought it was in a roll, turned on its thrusters, and then spun itself in such a way that it could have lost sunlight power.

NASA is trying to send out commands to address all of these failure possibilities, and it emphasizes that a recovery is still possible.

The Solar and Heliospheric Observatory (SOHO), for example, also lost power in 1998 when a spin put its solar panels out of reach of the Sun.

However, as its orbit changed, the Sun's light eventually fell across the panels and power was restored. The spacecraft was recovered and still works today.

NASA Science Fleet: Comet Siding Spring C/2013 A1

Credit: NASA

NASA's extensive fleet of science assets, particularly those orbiting and roving Mars, have front row seats to image and study a once-in-a-lifetime comet flyby on Sunday, Oct. 19.

Comet C/2013 A1, also known as comet Siding Spring, will pass within about 87,000 miles (139,500 kilometers) of the Red Planet, less than half the distance between Earth and our moon and less than one-tenth the distance of any known comet flyby of Earth.

Siding Spring's nucleus will come closest to Mars around 2:27 p.m. EDT, hurtling at about 126,000 mph (56 kilometers per second).

This proximity will provide an unprecedented opportunity for researchers to gather data on both the comet and its effect on the Martian atmosphere.

"This is a cosmic science gift that could potentially keep on giving, and the agency's diverse science missions will be in full receive mode," said John Grunsfeld, astronaut and associate administrator for NASA's Science Mission Directorate in Washington.

"This particular comet has never before entered the inner solar system, so it will provide a fresh source of clues to our solar system's earliest days."

Siding Spring came from the Oort Cloud, a spherical region of space surrounding our sun and occupying space at a distance between 5,000 and 100,000 astronomical units.

It is a giant swarm of icy objects believed to be material left over from the formation of the solar system.

Siding Spring will be the first comet from the Oort Cloud to be studied up close by spacecraft, giving scientists an invaluable opportunity to learn more about the materials, including water and carbon compounds, that existed during the formation of the solar system 4.6 billion years ago.

Some of the best and most revealing images and science data will come from assets orbiting and roving the surface of Mars.

Mars Atmosphere and Volatile EvolutioN (MAVEN)

In preparation for the comet flyby, NASA maneuvered its Mars Odyssey orbiter, Mars Reconnaissance Orbiter (MRO), and the newest member of the Mars fleet, Mars Atmosphere and Volatile EvolutioN (MAVEN), to reduce the risk of impact with high-velocity dust particles coming off the comet.

The period of greatest risk to orbiting spacecraft will start about 90 minutes after the closest approach of the comet's nucleus and will last about 20 minutes, when Mars will come closest to the center of the widening trail of dust flying from the comet's nucleus.

"The hazard is not an impact of the comet nucleus itself, but the trail of debris coming from it. Using constraints provided by Earth-based observations, the modeling results indicate that the hazard is not as great as first anticipated."

"Mars will be right at the edge of the debris cloud, so it might encounter some of the particles, or it might not," said Rich Zurek, chief scientist for the Mars Exploration Program at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.

The atmosphere of Mars, though much thinner that Earth's, will shield NASA Mars rovers Opportunity and Curiosity from comet dust, if any reaches the planet. Both rovers are scheduled to make observations of the comet.

NASA's Mars orbiters will gather information before, during and after the flyby about the size, rotation and activity of the comet's nucleus, the variability and gas composition of the coma around the nucleus, and the size and distribution of dust particles in the comet's tail.

Observations of the Martian atmosphere are designed to check for possible meteor trails, changes in distribution of neutral and charged particles, and effects of the comet on air temperature and clouds.

MAVEN will have a particularly good opportunity to study the comet, and how its tenuous atmosphere, or coma, interacts with Mars' upper atmosphere.

Earth-based and space telescopes, including NASA and ESA's iconic Hubble Space Telescope, also will be in position to observe the unique celestial object.

The agency's astrophysics space observatories, Kepler, Swift, Spitzer, Chandra, and the ground-based Infrared Telescope Facility on Mauna Kea, Hawaii, also will be tracking the event.

NASA's asteroid hunter, the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE), has been imaging, and will continue to image, the comet as part of its operations, and the agency's two Heliophysics spacecraft, Solar TErrestrial RElations Observatory (STEREO) and Solar and Heliophysics Observatory (SOHO), also will image the comet.

The agency's Balloon Observation Platform for Planetary Science (BOPPS), a sub-orbital balloon-carried telescope, already has provided observations of the comet in the lead-up to the close encounter with Mars.

Images and updates will be posted online before and after the comet flyby. Several pre-flyby images of Siding Spring, as well as information about the comet and NASA's planned observations of the event, are available online.

NASA Studies of the ultraviolet sun

Four of the telescopes on the Solar Dynamics Observatory observe extreme ultraviolet light activity on the sun that is invisible to the naked eye. 

Credit: NASA/SDO

You cannot look at the sun without special filters, and the naked eye cannot perceive certain wavelengths of sunlight.

Solar physicists must consequently rely on spacecraft that can observe this invisible light before the atmosphere absorbs it.

"Certain wavelengths either do not make it through Earth's atmosphere or cannot be seen by our eyes, so we cannot use normal optical telescopes to look at the spectrum," said Dean Pesnell, the project scientist for the Solar Dynamics Observatory (SDO), at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Several spacecraft can observe these invisible light wavelengths. SDO for example has four telescopes that image the sun in the ultraviolet spectrum.

As beams of ultraviolet light pass into the telescope, a mirror with special coatings filters and amplifies the ultraviolet light's otherwise poor reflection.

The incoming photons are then recorded as pixels and converted into electrical signals, similar to how your cell phone camera sees visible light.

"It's exactly the same process, whether it's ultraviolet light, infrared light, visible light, or radio," said Joseph Gurman, project scientist for both the Solar and Heliospheric Observatory (SOHO) and the Solar Terrestrial Relations Observatory (STEREO) at Goddard.

"In this case we're trying to understand how the sun changes and how those changes affect life here on Earth."

Ultraviolet light causes molecular radiation damage to our skin, seen as sunburns that can lead to cancer.

Its cousin, extreme ultraviolet radiation, and the associated solar storms have the potential to disrupt communications and spacecraft navigation.

"These are very damaging, energetic photons, and we want to understand what chain of events produces these photons," Pesnell said.

The Solar Dynamics Observatory (SDO) observed a solar flare (upper left) and a coronal mass ejection (right) erupting from the sun’s limb in extreme ultraviolet light on August 6, 2010. 

Credit: NASA/SDO

Thankfully our planet's atmosphere absorbs much of this solar radiation, making life on Earth possible.

However, this means that to study extreme ultraviolet light, instruments must do it from the vacuum of space.

"Ultraviolet light from the sun can show us the origins of solar storms that can lead to power outages, cell phone disruptions, and delays in shipping packages due to the rerouting of planes from over the pole," Gurman said.

By understanding what occurs in the sun's atmosphere, scientists hope to predict when powerful solar events such as coronal mass ejections and solar flares may occur.

Spacecraft record solar activity as a binary code, 1s and 0s, which computer programs can translate into black and white. 

Scientists coloroured the images for realism, and then zoom in on areas of interest. 

Credit: NASA/Karen Fox

"You really want to know what's happening on the sun as soon as you can," said Jack Ireland, a solar visualization specialist at Goddard.

"We can then use computer models to estimate how solar events will affect Earth's space environment."

The information can then be used by NOAA's Space Weather Prediction Center, in Boulder, Co. to alert power companies and airlines to take the necessary precautions, thus avoiding power outages and keeping airplane passengers safe.

The sun has gone quiet: Sunspots and CME

The Sun by the Atmospheric Imaging Assembly of NASA's Solar Dynamics Observatory. 

Credit: NASA

The sun has gone quiet. Almost too quiet.

A few weeks ago it was teeming with sunspots, as you would expect since we are supposed to be in the middle of solar maximum-the time in the sun's 11-year cycle when it is the most active but now, there is hardly a sunspot in sight.

In an image taken Friday by NASA's Solar Dynamics Observatory, there is a tiny smidgen of brown just right of center where a small sunspot appears to be developing. But just one day before, there was nothing. It was a totally spotless day.

So what's going on here? Is the "All Quiet Event" as solar physicist Tony Phillips dubbed it, a big deal, or not?

"It is weird, but it's not super weird," said Phillips, who writes about solar activity on his web site SpaceWeather.com.

"To have a spotless day during solar maximum is odd, but then again, this solar maximum we are in has been very wimpy."

Phillips notes that this is the weakest solar maximum to have been observed in the space age, and it is shaking out to be the weakest one in the past 100 years, so the spotless day was not so totally out of left field.

"It all underlines that solar physicists really don't know what the heck is happening on the sun," Phillips said.

"We just don't know how to predict the sun, that is the take away message of this event."

Sunspots are interesting to solar observers because they are the region of the sun where solar activity such as solar flares (giant flashes of light) and coronal mass ejections (when material from the sun goes shooting off into space) originate.

They are caused by highly concentrated magnetic fields that are slightly cooler than the surrounding surface of the sun, which is why they appear dark to us.

Those intense magnetic fields can get twisted up and tangled, which causes a lot of energy to build up. Solar flares and coronal mass ejections occur when that energy is released in a very explosive way.

Alex Young, a heliophysicist at Goddard Space Flight Center, said it is hard to say what is and isn't unusual when it comes to the sun.

"We've only been observing the sun in lots of detail in the last 50 years," he said.

"That's not that long considering it's been around for 4.5 billion years." And it's not like astronomers have never seen the sun this quiet before.

Three years ago, on Aug. 14, 2011 it was completely free of sunspots and, as Phillips points out, that year turned out to have relatively high solar activity overall with several X-class flares.

So in that case, the spotless sun was just a "temporary intermission," as he writes on his web site.

Whether this quiet period will be similarly short-lived or if it will last longer remains to be seen.

"You just can't predict the sun," Phillips said.

NASA SOHO: Necklaces of solar activity

Back in 1998, the Sun was behaving as expected. The approximately 11-year cycle of activity was proceeding smoothly, heading towards a peak in 2001.

The Solar and Heliospheric Observatory (SOHO) captured this image on 9 November 1998 through its ultraviolet telescope, showing radiation from iron atoms bathed in a gas of around a million degrees Celsius.

This textbook image of solar activity shows two brighter bands circling the Sun at the same latitude in each hemisphere.

At visible wavelengths these bright loops and patches are associated with dark smudges known as sunspots.

They are produced when loops of magnetism become buoyant and rise from inside the Sun into the atmosphere.

When the cycle begins, the active regions appear at high latitudes in sparse numbers, disappearing after a few weeks or so.

As the cycle proceeds, new and often larger active regions appear more frequently at successively lower latitudes.

Many can be larger than Earth, and they sometimes persist for months.

This activity takes place in both hemispheres simultaneously, and about five or six years into the cycle sunspots reach lower latitudes closer to the equator. This is known as solar maximum.

After this, the number of spots begins to decline until they virtually disappear and the cycle starts again at high latitudes. It is one of the enduring mysteries of the Sun why this cycle happens.

Certainly, it is linked to the way the Sun generates magnetism deep inside its gaseous layers but the details remain elusive.

In recent years, the Sun has deviated from this textbook behaviour. The current cycle was about two years late in starting, the hemispheres are behaving differently and the peak of activity is relatively modest.

The next cycle is expected to continue in this new vein. It may even be weaker than the current cycle.

SOHO views X-class solar flare

The Coronal Mass Ejection (CME) resulting from the big X-class solar flare on 10 June 2014 as seen through the LASCO C2 instrument of the ESA/NASA Solar and Heliospheric Observatory (SOHO).

LASCO (Large Angle Spectrometric Coronagraph) is able to take images of the solar corona by blocking the light coming directly from the Sun with an occulter disk, creating an artificial eclipse within the instrument itself.

SOHO is a project of international collaboration between ESA and NASA to study the Sun from its deep core to the outer corona and the solar wind. More about SOHO:

Credits: SOHO (ESA & NASA)

Giant Sun Plasma Tendril: Solar Eruption - SDO Video

A massive formation on the sun made of super-hot magnetic plasma erupted this week in an explosive solar storm captured on video by NASA's SDO spacecraft.

The huge plasma tendril, known as a solar filament, erupted on Wednesday (June 4), blowing part of itself out into space in what astronomers call a coronal mass ejection (CME).

NASA's powerful Solar Dynamics Observatory recorded a video of the solar filament eruption while the Solar and Heliospheric Observatory (SOHO) tracked the subsequent CME.

Astronomer Tony Phillips of Spaceweather.com, a website that tracks solar flare events, wrote in a post Thursday (June 5) that amateur and professional astronomers had watched the filament for more than a week to see how it would meet its end.

"Astronomers had been bracing for the possibility that the filament would collapse, causing a Hyder flare when it landed on the solar surface," Phillips wrote in the June 5 post. "Instead, it erupted and hurled part of itself into space."

Phillips added that the solar eruption was not aimed directly at Earth, but could deal a "glancing blow" to the planet's magnetic field on Saturday (June 7), possibly amplifying northern lights displays.

A giant solar plasma filament on the sun rising up off the star's surface on June 4, 2014 in this full-disk view from NASA's Solar Dynamics Observatory. 

The filament ultimately triggered a solar eruption known as a coronal mass ejection.

Credit: NASA/SDO

NASA's Solar Dynamics Observatory and SOHO, a joint mission by NASA and the European Space Agency, are part of a fleet of space observatories regularly watching the sun for signs of solar storms, eruptions and flares.

The most powerful solar eruptions can pose a danger to astronauts and spacecraft in space, as well as interrupt satellite navigation and communications systems. They can also interfere with ground-based power and communications systems.

Strong and moderate solar storms can also supercharge the Earth's auroras, triggering dazzling northern lights shows.

ESA NASA SOHO: Solar Cycle

Credit: SOHO (ESA & NASA)

It took 10 years to create this image of our changing Sun.

Taken from space by the Solar and Heliospheric Observatory (SOHO), it shows a dramatically different picture than the one we receive on Earth.

From Earth's surface, we are treated to a biased view.

Every day our world is bathed in the Sun's light and heat, and at these visible and infrared wavelengths our luminary shines to within a fraction of a percent of the same energy every day.

At ultraviolet and X-ray wavelengths, this is not true. Launched in 1995, SOHO has been continuously monitoring the Sun since then, in part to study this variation.

Back in 2006, one image for each year of the mission until then was chosen and displayed in this montage.

The bright parts of these images correspond to gas in the Sun's atmosphere at a temperature of about 2 million degrees Celsius.

Unlike visible light, the intensity of the ultraviolet radiation from the Sun varies greatly.

This variation becomes more pronounced the shorter the wavelength, especially in the X-ray region of the spectrum.

This is governed by solar activity, which runs in an approximately 11-year cycle.

It is linked to the generation of the Sun's magnetic field although our precise understanding of this mechanism remains elusive.

The waxing and waning of cycle-23, counted since 1755 when systematic record-taking began, can be seen clearly in this image.

At its peak in 2001, the Sun was a maelstrom of activity, releasing about 10 times more ultraviolet light than at the minimum periods that can be seen in 1996 and 2006.

Now in cycle-24, the Sun is again at a peak of activity, although it is milder than that of 2001.

NASA's Solar Dynamics Observatory (SDO): Massive Sunspot AR1944

One of the largest sunspots in the last nine years, labeled AR1944, was seen in early January 2014, as captured by NASA's Solar Dynamics Observatory (SDO). 

An image of Earth has been added for scale. 

Credit: NASA/SDO

An enormous sunspot, labeled AR1944, slipped into view over the sun's left horizon late on Jan. 1, 2014.

The sunspot steadily moved toward the right, along with the rotation of the sun, and now sits almost dead center, as seen in the image above from NASA's Solar Dynamics Observatory (SDO).

Sunspots are dark areas on the sun's surface that contain complex arrangements of strong magnetic fields that are constantly shifting.

The largest dark spot in this configuration is approximately two Earths wide, and the entire sunspot group is some seven Earths across.

For comparison, another giant sunspot, five to six Earths across, is shown below from 2005. The image was captured by the European Space Agency and NASA's Solar and Heliospheric Observatory (SOHO).

Sunspots are part of what's known as active regions, which also include regions of the sun's atmosphere, the corona, hovering above the sunspots.

Active regions can be the source of some of the sun's great explosions: solar flares that send out giant bursts of light and radiation due to the release of magnetic energy, or coronal mass ejections that send huge clouds of solar material out into space.

As the sunspot group continues its journey across the face of the sun, scientists will watch how it changes and evolves to learn more about how these convoluted magnetic fields can cause space weather events that can affect space-borne systems and technological infrastructure on Earth.

Two of the largest sunspots in the last nine years: the one on the left is from Jan. 17, 2005, captured by ESA/NASA's Solar Heliospheric Observatory; the one on the right is from Jan. 7, 2014, captured by NASA's Solar Dynamics Observatory. 

Credit: ESA/NASA SOHO and NASA SDO

Solar activity not a key cause of climate change

A composite of space- and ground-based observations in different wavelengths gathered on the day of the solar eclipse of 3 November 2013. 

The result is an overall view of the Sun and its surrounding corona, extending far out into space.

Credit: SOHO

Climate change has not been strongly influenced by variations in heat from the sun, a new scientific study shows.

The findings overturn a widely held scientific view that lengthy periods of warm and cold weather in the past might have been caused by periodic fluctuations in solar activity.

Research examining the causes of climate change in the northern hemisphere over the past 1000 years has shown that until the year 1800, the key driver of periodic changes in climate was volcanic eruptions.

These tend to prevent sunlight reaching the Earth, causing cool, drier weather. Since 1900, greenhouse gases have been the primary cause of climate change.

The findings show that periods of low sun activity should not be expected to have a large impact on temperatures on Earth, and are expected to improve scientists' understanding and help climate forecasting.

Scientists at the University of Edinburgh carried out the study using records of past temperatures constructed with data from tree rings and other historical sources.

They compared this data record with computer-based models of past climate, featuring both significant and minor changes in the sun.

They found that their model of weak changes in the sun gave the best correlation with temperature records, indicating that solar activity has had a minimal impact on temperature in the past millennium.

The study, published in Nature Geoscience, was supported by the UK Natural Environment Research Council.

Dr Andrew Schurer, of the University of Edinburgh's School of GeoSciences, said: "Until now, the influence of the sun on past climate has been poorly understood.

We hope that our new discoveries will help improve our understanding of how temperatures have changed over the past few centuries, and improve predictions for how they might develop in future.

Links between the sun and anomalously cold winters in the UK are still being explored."

More information: Small influence of solar variability on climate over the past millennium, DOI: 10.1038/ngeo2040

The Sun reverses its magnetic poles - Video

This visualization shows the position of the sun's magnetic fields from January 1997 to December 2013. The field lines swarm with activity:

The magenta lines show where the sun's overall field is negative and the green lines show where it is positive.

A region with more electrons is negative, the region with less is labeled positive. Additional gray lines represent areas of local magnetic variation.

The entire sun's magnetic polarity, flips approximately every 11 years—though sometimes it takes quite a bit longer—and defines what's known as the solar cycle.

The visualization shows how in 1997, the sun shows the positive polarity on the top, and the negative polarity on the bottom.

Over the next 12 years, each set of lines is seen to creep toward the opposite pole eventually showing a complete flip.

By the end of the movie, each set of lines are working their way back to show a positive polarity on the top to complete the full 22 year magnetic solar cycle.

At the height of each magnetic flip, the sun goes through periods of more solar activity, during which there are more sunspots, and more eruptive events such as solar flares and coronal mass ejections, or CMEs.

The point in time with the most sunspots is called solar maximum.

Image showing the sun's magnetic fields on Jan. 1, 1997, June 1, 2003, and Dec. 1, 2013. Green indicates postive polarity. Purple is negative.

Learn more about the sun's activity from Dr Alex Young.


Alex Young is interviewed about the current solar cycle and what a magnetic flip means for the earth and NASA's study of magnetic fields

Comet ISON drawn in by Sun's gravity and burns up - Video

The comet has most likely disintegrated under the high heat and gravitational stress of the Sun on Nov. 28, 2013. 

It is not visible in Solar Dynamics Observatory (SDO) footage and NASA scientists confirmed that they do not see it. 

 Credit: NASA / SDO / SOHO

NASA Stereo: ISON Comet approaching the Sun - video

Now that we have observations of the comet in the NASA STEREO instruments and, more recently, the ESA/NASA SOHO LASCO C3 instrument, CIOC team member Matthew Knight has been able to start recording photometry of the comet.

His results seem to imply that the comet may have experienced an outburst during the (approximate) period Nov 21 - 23 with corresponding brightness increase, followed by a leveling off and then dropping back down to "pre-outburst" levels.

Since entering the LASCO C3 field of view, comet ISON has increased by at least a factor of four, and indications are it may be closer to a factor of ten. In the most recently available images, the comet appears to be around magnitude +0.5.

It is now the opinion of the CIOC Team that Comet ISON is now behaving like a sungrazing comet. We can not comment on whether the nucleus is in tact or not, but our analyses indicate that its rate of brightening is directly in line with that we have experienced with other sungrazing comets.

This has no implication on its chances of survival. We strongly encourage all professional solar observatories who have plans in place for observing the comet, to please do so, and the teams should plan for an object brighter than negative one magnitude (and we are being conservative on this estimate).

Today's tl;dr is somewhat upbeat: we don't know if ISON will survive, and we won't know until it either does it or vaporizes but the comet is still "alive" and brightening dramatically in accordance with the behaviour we expect of sungrazers. Professional observers with solar telescopes should plan for a negative magnitude object, and we urge observation from these facilities.

Comet ISON Dances near the Sun

In this photo provided by NASA, a contrast-enhanced image produced from the Hubble images of comet ISON taken April 23, 2013 reveals the subtle structure in the inner coma of the comet. 

In this computer-processed view, the Hubble image has been divided by a computer model coma that decreases in brightness proportionally to the distance from the nucleus, as expected for a comet that is producing dust uniformly over its surface. 

ISON's coma shows enhanced dust particle release on the sunward-facing side of the comet's nucleus, the small, solid body at the core of the comet. 

This information is invaluable for determining the comet's shape, evolution, and spin of the solid nucleus. (AP Photo/NASA)

Comet ISON is teasing the solar system as it dances with the sun and it's giving astronomers mixed signals.

Will it meet a fiery death—or survive—when it whips around the sun on Thursday?

The icy comet will be only about 1 million miles ( 1.6 million kilometers) away from the sun's super-hot surface during its close encounter on US Thanksgiving day.

On Monday, it looked like it was about to die even before it got there. On Tuesday, it appeared healthy again.

"We have never seen a comet like this," Naval Research Laboratory astrophysicist Karl Battams said during a NASA news conference Tuesday. "It has been behaving strangely."

Because it is so close to the sun, ISON will likely not be visible from Earth on Thursday—except via a fleet of NASA telescopes and spacecraft aimed at the comet as it gets closest to the sun at 1:37 p.m. EST( (1837 GMT), he said and it will be a few hours before scientists know whether the comet survives.

But even if the comet dies, Johns Hopkins University scientist Carey Lisse said there's a good chance that people on Earth will get an interesting cosmic show.

The comet's remnants could paint the sky with a wide swath of green in the Northern Hemisphere.

The Sun and one of physics' biggest unsolved problems

The sun with a coronal hole (the large dark region at the bottom). Credit: NASA

Daniel Wolf Savin and Michael Hahn have been fascinated by the universe since they were boys.

For Savin, a senior research scientist in the Columbia Astrophysics Laboratory, discovering Albert Einstein at age 12 spurred the desire to "learn everything about the universe."

Years later, Hahn, an associate research scientist who grew up 40 miles from Savin's home town in Connecticut, started gazing at the stars as a teenager; he eventually became president of the astronomy club at his alma mater, Carnegie Mellon.

Now the two have made a big leap toward cracking one of the biggest mysteries in astrophysics—why the corona, or plasma surrounding the sun, is so much hotter than the sun's surface.

The coronal heating problem, as it is known, is important because the corona is the source of solar wind, which is responsible for the northern and southern lights and can also disrupt telecommunications and power grids.

"Satellites can be slowly pushed out of their orbits if they're deflected by the solar wind so if we can better understand the cause, we can create better models for space weather," says Savin, referring to conditions beyond the atmosphere.

Scientists have proposed two main theories to explain why the temperature of the gas in the corona, which lies above the solar surface, soars to over 1 million degrees Kelvin even though the surface of the sun is a relatively cool 6,000 degrees. (The center of the sun is 15 million degrees.)

This unexpected phenomenon has puzzled researchers since 1939, when scientists first discovered the temperature difference; it's as if a flame were coming out of an ice cube.

Read the full article here at www.phys.org

NASA SOHO: Sun Diving Comet crash - Video

A sun-diving Kreutz-family comet came to its conclusion on Oct. 10, 2013. NASA's SOHO was on hand to witness it.

Credit: NASA / SOHO

Irish Radio observatory finds link: solar storms and radio bursts

New research by scientists at Trinity College Dublin, University College London, and the University of Hawai'i, published online in Nature Physics, has shown for the first time a direct link between solar storms, shock waves and solar radio bursts.

The Sun gives light and heat that makes life possible on Earth.

It can, however, have more sinister effects, sometimes unleashing huge eruptions of hot gas, called solar storms, which carry billions of tons of matter travelling at millions of kilometres an hour in Earth's direction.

These storms can be accompanied by solar radio bursts, which can cause damaging effects on many of the technologies that we rely on in our everyday lives.

Eoin Carley

"Radio bursts from solar storms can have adverse effects on both satellite and terrestrial communications. In fact, mobile phone networks can experience increased dropped-calls during periods of increased solar activity," said Eoin Carley, Irish Research Council PhD student at the School of Physics, Trinity College Dublin and first author on a recent paper on this topic in Nature Physics.

Despite decades of study, the link between solar storms and solar radio bursts has remained unclear.

This led Professor Peter Gallagher, a solar physicist at Trinity's School of Physics, to establish a radio observatory at Birr Castle in the midlands of Ireland to monitor solar radio bursts.

"What we have found is fascinating – a real insight into how solar radio bursts are created", said Professor Gallagher.

"Using antennas at Trinity's Rosse Observatory in Birr Castle together with images from NASA's STEREO and Solar Dynamics Observatory spacecraft, we have identified a missing link between solar storms and radio bursts."

Birr Castle Observatory

The findings, which were published online this week in Nature Physics, show that solar storms create huge shock waves that race through the solar atmosphere at millions of kilometres per hours.

As they do, they can accelerate electrons to huge energies, which then produce radio waves.

"Our results not only give an insight into the fundamental physics of explosions on the Sun, but enable us to better understand how the Sun affects the Earth and potentially its impacts on our daily lives" according to Carley.

NASA SOHO: Capture an Earth directed coronal mass ejection (CME)

The SOHO LASCO C2 instrument captured this image of the Earth-directed CME. SOHO's coronographs are able to take images of the solar corona by blocking the light coming directly from the Sun with an occulter disk. 

The location of the actual sun is shown with an image taken by SDO. 

Credit: ESA & NASA/SOHO, SDO

On August 20, 2013 at 4:24 am EDT, the sun erupted with an Earth-directed coronal mass ejection or CME, a solar phenomenon which can send billions of tons of particles into space that can reach Earth one to three days later.

These particles cannot travel through the atmosphere to harm humans on Earth, but they can affect electronic systems in satellites and on the ground.

Experimental NASA research models, based on observations from NASA's Solar Terrestrial Relations Observatory show that the CME left the sun at speeds of around 570 miles per second, which is a fairly typical speed for CMEs.

Earth-directed CMEs can cause a space weather phenomenon called a geomagnetic storm, which occurs when they funnel energy into Earth's magnetic envelope, the magnetosphere, for an extended period of time.

The CME's magnetic fields peel back the outermost layers of Earth's fields changing their very shape. In the past, geomagnetic storms caused by CMEs of this strength have usually been mild.

Magnetic storms can degrade communication signals and cause unexpected electrical surges in power grids. They also can cause aurora.

The SOHO LASCO C3 instrument captured this coronographic image of the Earth-directed CME. 

The bright white object to the right is the planet Mercury. 

Credit: ESA & NASA/SOHO

ESA SOHO Video: 2 CMEs Side by Side

Two coronal mass ejections (CMEs) expand side-by-side from the Sun and out into space in this movie, playing out in front of the ESA/NASA Solar and Heliospheric Observatory, SOHO, on 1-2 July 2013.

The shaded disc at the centre of the image is a mask in SOHO’s LASCO instrument that blots out direct sunlight to allow study of the faint details in the Sun's corona. The white circle added within the disc shows the size and position of the visible Sun.

CMEs comprise millions of tonnes of gas and race away from the Sun at several million kilometres per hour.

In the event shown in this movie, one small CME slowly emerges directly above the Sun as seen by SOHO. Shortly after, a much larger, faster event bursts from the left, and together the CMEs expand into space.

The larger event was likely triggered as a solar filament became unstable and lifted away from the Sun. Filaments form in magnetic loops and suspend cool, dense gas above the solar surface.

From above, filaments appear as dark lineaments against the hotter surface below, but in profile they form giant glowing loops called prominences. When their magnetic fields become unstable, they can trigger flares or CMEs.

Neither of these two CMEs interacted with Earth but when other events like these do, even a glancing blow to the planet’s magnetic field can ignite spectacular natural light displays – aurora – over the poles.

But in the most extreme events CMEs can cause much trouble, initiating geomagnetic storms that can result in regional power outages and communications blackouts.

The shaded disc at the centre of the image is a mask in SOHO’s LASCO instrument that blots out direct sunlight to allow study of the faint details in the Sun's corona. The white circle added within the disc shows the size and position of the visible Sun.

NASA SOHO: Large coronal hole near the sun's north pole

The European Space Agency/NASA Solar and Heliospheric Observatory, or SOHO, captured this image of a gigantic coronal hole hovering over the sun's north pole on July 18, 2013, at 9:06 a.m. EDT. 

Credit: ESA&NASA /SOHO

The European Space Agency/NASA Solar and Heliospheric Observatory, or SOHO, captured this image of a gigantic coronal hole hovering over the sun's north pole on July 18, 2013, at 9:06 a.m. EDT.

Coronal holes are dark, low density regions of the sun's outermost atmosphere, the corona.

They contain little solar material, have lower temperatures, and therefore, appear much darker than their surroundings.

Coronal holes are a typical feature on the sun, though they appear at different places and with more frequency at different times of the sun's activity cycle.

The activity cycle is currently ramping up toward what is known as solar maximum, currently predicted for late 2013.

During this portion of the cycle, the number of coronal holes decreases. During solar max, the magnetic fields on the sun reverse and new coronal holes appear near the poles with the opposite magnetic alignment.

The coronal holes then increase in size and number, extending further from the poles as the sun moves toward solar minimum again. At such times, coronal holes have appeared that are even larger than this one.

The holes are important to our understanding of space weather, as they are the source of a high-speed wind of solar particles that streams off the sun some three times faster than the slower wind elsewhere.

While it's unclear what causes coronal holes, they correlate to areas on the sun where magnetic fields soar up and away, failing to loop back down to the surface, as they do elsewhere.