Comet ISON dies as it rounds the Sun.


Our star apparently destroyed this surprisingly fragile celestial visitor during their close encounter.
Time-lapse image of Comet ISON from SOHO
Comet ISON comes in from the bottom right and moves out toward the upper right, getting fainter and fainter, in this time-lapse image from the ESA/NASA Solar and Heliospheric Observatory. The image of the sun at the center is from NASA’s Solar Dynamics Observatory.
ESA/NASA/SOHO/SDO/GSFC
Comet ISON (4.5 billion B.C. – A.D. 2013) survived for more than 4.5 billion years in the frigid depths of the solar system, but it fizzled during its brief moment in the Sun on November 28. Through a combination of ISON’s delicate makeup, the Sun’s intense heat, and — most importantly — our star’s powerful tidal forces, the comet’s nucleus failed to survive its brush within 730,000 miles (1.16 million kilometers) of the Sun’s surface.As the comet approached perihelion (its least distance from the Sun) November 28, it continued to brighten at roughly the rate astronomers had predicted. Late on the evening of the 27th (in North America), ISON peaked at magnitude –2.0. Images from coronagraphs aboard both the Solar and Heliospheric Observatory (SOHO) and the Solar Terrestrial Relations Observatory (STEREO) showed the comet as a bright point of light trailed by one distinct dust tail and a narrow dust streamer.

But ISON started to fade even before its closest approach to the Sun. The Solar Dynamics Observatory (SDO), which is equipped with the best cameras for close-up observations of our star and its surroundings, failed to see the comet at perihelion. And once ISON had moved far enough beyond the Sun that it could reappear in SOHO’s coronagraphs, it was nowhere to be found.

As astronomers began to write their post-mortems, however, the unpredictable comet rose from the dead like the legendary Phoenix. Some 24 hours after perihelion, SOHO once again captured images of ISON showing a thin dusty tail and a diffuse central condensation that some interpreted as a small remnant of the comet’s nucleus. But the revival soon began to peter out — by late on November 29, the glow had faded to around 6th magnitude.

It appears that the show amateur astronomers were hoping ISON would produce once it emerged from the Sun’s glare in early December won’t take place. Most scientists think the nucleus has dissipated, and any remaining dust likely will be too faint to see through anything but large telescopes. Even though ISON’s saga seems over, astronomers will spend months poring over their observations of this one-of-a-kind visitor.

 

Huge Solar Eruption November 20th.


On Nov. 20, 2012, at 7:09 a.m. EST, the sun erupted with a coronal mass ejection or CME. Not to be confused with a solar flare, a CME is a solar phenomenon that can send solar particles into space and can reach Earth one to three days later. When Earth-directed, CMEs can affect electronic systems in satellites and on Earth.

 

NASA’s Solar Terrestrial Relations Observatory (STEREO) captured this image of a coronal mass ejection on Nov. 20, 2012 at 8:54 a.m. EST, about two hours after it left the sun.

Experimental NASA research models, based on observations from the Solar Terrestrial Relations Observatory (STEREO), show that the Nov. 20 CME left the sun at speeds of 450 miles per second, which is a slow to average speed for CMEs. CMEs can cause a space weather phenomenon called a geomagnetic storm, which occurs when CMEs successfully connect up with the outside of the Earth’s magnetic envelope, the magnetosphere, for an extended period of time. In the past, CMEs of this speed have not usually caused substantial geomagnetic storms. They have caused auroras near the poles but are unlikely to cause disruptions to electrical systems on Earth or interfere with GPS or satellite-based communications systems.

NOAA’s Space Weather Prediction Center (http://swpc.noaa.gov) is the United States government’s official source for space weather forecasts.

 

On December 11 (tentative), SWPC will introduce two new forecast products titled the 3-Day Forecast and the Forecast Discussion.  These new products will: be available twice a day at 0030 and 1230 UTC; provide space weather information in two separate formats, abbreviated and detailed; and use NOAA Space Weather Scale information.  Examples of these new products are available to familiarize our users at http://www.swpc.noaa.gov/info/3-Day.pdf(the concise, 1-page summary) and http://www.swpc.noaa.gov/info/Discussion.pdf(the in-depth space weather analysis for the technical user).  These two products will supplement the existing product suite and no current products will be discontinued.

Source: http://beforeitsnews.com

NASA STEREO Observes One of the Fastest CMEs On Record.


On July 23, 2012, a massive cloud of solar material erupted off the sun’s right side, zooming out into space, passing one of NASA’s Solar TErrestrial RElations Observatory (STEREO) spacecraft along the way. Using the STEREO data, scientists at NASA’s Goddard Space Flight Center in Greenbelt, Md. clocked this giant cloud, known as a coronal mass ejection, or CME, as traveling between 1,800 and 2,200 miles per second as it left the sun.

Conversations began to buzz and the emails to fly: this was the fastest CME ever observed by STEREO, which since its launch in 2006 has helped make CME speed measurements much more precise. Such an unusually strong bout of space weather gives scientists an opportunity to observe how these events affect the space around the sun, as well as to improve their understanding of what causes them.

“Between 1,800 and 2,200 miles per second puts it without question as one of the top five CMEs ever measured by any spacecraft,” says solar scientist Alex Young at Goddard. “And if it’s at the top of that velocity range it’s probably the fastest.”

The STEREO mission consists of two spacecraft with orbits that for most of their journey give them views of the sun that cannot be had from Earth. Watching the sun from all sides helps improve our understanding of how events around the sun are connected, as well as gives us glimpses of activity we might not otherwise see. On July 23, STEREO-A lay – from Earth’s perspective — to the right side and a little behind the sun, the perfect place for seeing this CME, which would otherwise have been hard to measure from Earth. The Solar Heliospheric Observatory (SOHO), an ESA and NASA mission, also observed the CME. It is the combination of observations from both missions that helps make scientists confident in the large velocities they measured for this event.

Measuring a CME at this speed, traveling in a direction safely away from Earth, represents a fantastic opportunity for researchers studying the sun’s effects. Rebekah Evans is a space scientist working at Goddard’s Space Weather Lab, which works to improve models that could some day be used to improve predictions of space weather and its effects. She says that the team categorizes CMEs for their research in terms of their speed, with the fastest ones – such as this one — labeled “ER” for Extremely Rare.

“Seeing a CME this fast, really is so unusual,” says Evans. “And now we have this great chance to study this powerful space weather, to better understand what causes these great explosions, and to improve our models to incorporate what happens during events as rare as these.”

Orbiting the sun some 89,000,000 miles away, STEREO-A could observe the speed of the CME as it burst from the sun, and it provided even more data some 17 hours later as the CME physically swept by – having slowed down by then to about 750 miles per second. STEREO has instruments to measure the magnetic field strength, which in this case was four times as strong as the most common CMEs. When a CME with strong magnetic fields arrives near Earth, it can cause something called a geomagnetic storm that disrupts Earth’s own magnetic environment and can potentially affect satellite operations or in worst-case scenarios induce electric currents in the ground that can affect power grids.

“We measure magnetic fields in ‘Tesla’ and this CME was 80 nanoTesla,” says Antti Pulkkinen, who is also a space weather scientist at Goddard. “This magnetic field is substantially larger even than the CMEs that caused large geomagnetic storms near Earth in October 2003. We call those storms the Halloween storms and scientists still study them to this day.”

While large, this measurement of the magnetic field is still smaller than one of the greatest space weather events on record, the Carrington Event of 1859, during which the magnetic fields at Earth measured 110 nanoTesla.

When the CME passes over one of the STEREO spacecraft, the instruments can also measure the direction in which the magnetic field points – a crucial data point since it is the southward pointing magnetic fields in a CME that travel in the opposite direction of Earth’s own magnetic fields and thus can cause the most disruption. This CME traveled with an unusually large southward magnetic field of 40 nanoTesla that stayed steady for several hours.

The event also pushed a burst of fast protons out from the sun. The number of charged particles near STEREO jumped 100,000 times within an hour of the CME’s start. When such bursts of solar particles invade Earth’s magnetic field they are referred to as a solar radiation storm, and they can block high frequency radio communications as used, for example, by airline pilots. Like the CME, this solar energetic particle (SEP) event is also the most intense ever measured by STEREO. While the CME was not directed toward Earth, the SEP did – at a much lower intensity than at STEREO – affect Earth as well, offering scientists a chance to study how such events can widen so dramatically as they travel through space.

Evans points out that all of this solar activity was produced by a specific active region that NASA’s space weather scientists had been watching for three weeks before the super fast eruption on July 23.

“That active region was called AR 1520, and it produced four fairly fast CME’s in Earth’s direction before it rotated out of sight off the right limb of the sun,” says Evans. “So even though the region had released multiple CMEs and even had an X-class flare, its strength kept increasing over time to eventually produce this giant explosion. To try to understand how that change happens makes for very exciting research.”

STEREO is but one of several missions that observe the sun constantly, and the data is always interesting as there is much to be learned from observing the quiet sun as well as an active one. But the sun displays an activity cycle during which it gets more active approximately every 11 years as it heads toward what’s called “solar maximum.” The next solar maximum is currently predicted for 2013. We can expect more and more space weather events until then, and each one will help scientists better understand the sun and how its effects can permeate the entire solar system.

 

 

Karen C. Fox
Source: NASA’s Goddard Space Flight Center