Volcanic Comet 29P Erupts Again

Oct. 24, 2021:

The British Astronomical Association (BAA) is reporting another strong outburst of Comet 29P/Schwassmann-Wachmann. The volcanic comet suddenly brightened 10-fold on Oct. 23.75 UT when a sunlit vent opened, spewing ‘cryomagma’ into space. Dr. Richard Miles of the BAA provided this light curve:

Comet 29P is one of the strangest objects in the solar system. In fact, it strains the definition of “comet.” 29P is a ball of ice 60 km wide (much larger than a typical comet) trapped in a planet-like orbit between Jupiter and Saturn. It appears to be festooned with ice volcanoes which erupt ~20 times a year.

A rapidfire “super-eruption” of 4 volcanoes in late September created an expanding shell of vaporized cryomagma, which astronomers have been monitoring. Yesterday’s eruption propelled a new compact shell into the old larger one:

Above: Comet 29P photographed less than 12 hours after the Oct. 23rd eruption. Credit: Jean-Francois Soulier of France.

29P rotates once every ~58 days. As sunlight sweeps across its frozen surface, cryovolcanoes erupt under the high sun. “The latest eruption has taken place some 59 days after a similar event on August 25th, and may be an example of an outburst from the same cryovolcano erupting a second time on the next rotation of the nucleus,” says Miles.

Amateur astronomers with mid-sized telescopes and astrophotography experience are encouraged to monitor 29P. It changes every night. The comet is located in the constellation Auriga, high in the northern sky at midnight. Point your optics here and check the BAA’s Mission 29P website for updates.

more images: from Eliot Herman using a telescope in Mayhill, New Mexico

The Strange Magnetization of Sunspot AR2887

Oct. 24, 2021: Something does not add up. New sunspot AR2887 has two primary cores, each about the size of Earth. Usually when a sunspot looks like this, the two cores have opposite magnetic polarities, positive (+) and negative (-). In this case, however, they’re the same.

Pictured above is a magnetic map of AR2887 from NASA’s Solar Dynamics Observatory. It shows the primary poles of double sunspot AR2887 are both negative (-). Surrounding patches of positive (+) magnetic flux provide balance.

Perhaps AR2887 is not one but actually two sunspots jammed together in close proximity. We’ll get a better view of its magnetic architecture as AR2887 turns toward Earth in the days ahead. Stay tuned. Solar flare alerts: SMS Text.

more images: from Cai-Uso Wohler of Bispingen, Lueneburg Heath, Germany; from Francois Rouviere of Cannes, France; from Richard Jaworski of Carlingford, NSW, Australia; from Maximilian Teodorescu of Magurele, Romania;

20 Years Ago, A Severe Geomagnetic Storm

Oct. 21, 2021: Paolo Bardelli will never forget Oct. 21, 2001. “The sky over my hometown in Italy suddenly filled with intense red auroras,” he recalls. “This happened exactly 20 years ago today.”

Above: Red auroras over Tradate, Italy (latitude +45N), on Oct. 21, 2001. Photo credit: Cesare Guaita

A trip down memory lane: In 2001, Solar Cycle 23 was peaking and solar activity was very high. Strong flares were a daily occurance. On Oct. 19th, giant sunspot AR9661 erupted twice in quick succession, producing almost identical X1.6-class solar flares. The double blast hurled two bright CMEs toward Earth: CME #1, CME #2.

This is what the sun looked like that day:

The first CME took only two days to reach Earth. It was fast and potent. The storm cloud’s arrival on Oct. 21, 2001, ignited a severe geomagnetic storm (Kp=8). Solar wind speeds in the CME’s wake topped 700 km/s, keeping the storm going for more than 15 hours.

In Troutman, North Carolina, Ronnie Sherril witnessed the CME’s impact. “Auroras were visible in twilight even before the evening sky faded to black,” says Sherril, who took this picture at 7:30 pm local time:

“By 10:30 pm the sky had exploded into bright red with yellowish beams,” says Sherril. “What an awesome display!”

Less than a day later the second CME arrived, and it happened all over again. Another 15 hours of strong-to-severe storming ensued. Using data from a global network of magnetometers, NOAA made this record of planetary K-indices during the two-day event:

Red auroras were sighted in Germany, France, Italy, Spain, Australia, Japan, and in the United States as far south as latitude 35N. Remarkably, there were no widespread power outages or satellite disruptions. The Internet functioned normally throughout. It was mainly an aurora show.

Some observers are ready for more. “We are hoping for something similar for Solar Cycle 25, as the sun has recently had a good increase in its activity,” says Bardelli. Indeed, young Solar Cycle 25 is intensifying, but Solar Max isn’t expected for another 3 to 4 years. Until then, browse the October 2001 Aurora Photo Gallery.

A Volcanic Comet Blows its Top

Oct. 14, 2021: So you think you know what a comet is? Think again. Comet 29P/Schwassmann-Wachmann is challenging old ideas. Astronomers call it a comet, but, really, “giant space volcano” might be a better description. It’s a 60-km-wide ball of ice orbiting the Sun beyond Jupiter, and it appears to be one of the most volcanically active bodies in the entire Solar System.

Comet 29P just blew its top … again. In late September 2021, 29P erupted 4 times in quick succession, blowing shells of “cryomagma” into space. Arizona amateur astronomer Eliot Herman has been monitoring the debris:

“Initially it looked like a bright compact object,” says Herman. “Now the expanding cloud is 1.3 arcminutes wide (bigger than Jupiter) and sufficiently transparent for background stars to shine through.”

When this object was discovered in 1927, astronomers thought they had found a fairly run-of-the-mill comet, unusual mainly because it was trapped in a nearly circular orbit between Jupiter and Saturn. 29P quickly proved them wrong as it began to erupt over and over again. Modern observations show that outbursts are happening as often as 20 times a year (almost 3 times the rate of the widely-quoted Wikipedia figure, 7.3 times per year).

“The current outburst, which began on Sept. 25th, appears to be the most energetic of the past 40 years,” says Dr. Richard Miles of the British Astronomical Association (BAA). “Within a span of only 56 hours, four eruptions took place in quick succession, creating a ‘superoutburst.'”

Miles is a leading researcher of 29P, and he has developed a theory to explain what’s happening. The “comet,” he believes, is festooned with ice volcanoes. There is no lava. The “magma” is a cold mixture of liquid hydrocarbons (e.g., CH4, C2H4, C2H6 and C3H8) akin to those found in the lakes and streams of Saturn’s moon Titan. In Miles’s model, the cryomagma contains a sprinkling of dust and it is suffused with dissolved gases N2 and CO, all trapped beneath a surface which, in some places, has the consistency of wax. These bottled-up volatiles love to explode when a fissure is opened–hence some of 29P’s more spectacular eruptions.

Above: A time series of previous outbursts from June 2020 – April 2021. These are all small compared to the current superoutburst. Source: Mission 29P.

In a seminal paper published 5 years ago, Miles studied the modern record of eruptions and he found some patterns. Data suggest that 29P rotates every 57.7 days. The most active vents are concentrated on one side of the ice-ball in a range of longitudes less than 150 degrees wide. At least 6 discrete sources have been identified.

While most outbursts fade within a week or so, this superoutburst is still visible. The rat-a-tat-tat eruption in September boosted the comet’s brightness 250-fold, and it hasn’t declined much since then. With an integrated magnitude between +10 and +11, the expanding cloud is well within the range of backyard telescopes.

“Comet 29P can be seen with an 8 inch ‘scope,” says Herman. “In smaller instruments it will appear to be a bright dot. To resolve the cloud and photograph individual stars shining through it, I used the big half-meter iTelescope T11.”

Ready see something weird? 29P is located in the constellation Auriga, easy to find high in the sky at midnight. Visit Sky&Telescope for observing tips. Also, for the latest news check out the BAA’s MISSION 29P website.

Auroras in the USA

Oct. 12. 2021: It’s been a while. Last night, auroras were sighted in more than a dozen US states after a CME struck Earth’s magnetic field. “The G2 geomagnetic storm produced the first visible auroras from coastal Massachusetts since 2017,” reports Chris Cook, who snapped this 30-second self portrait around 1am EDT on Oct. 12th:

The red-topped auroras Cook witnessed are relatively rare; they appear during geomagnetic storms that spread far from the poles. Red is caused by oxygen atoms meeting the solar wind as high as 500 km above Earth’s surface.

In some states the auroras were so bright onlookers photographed them using nothing more than their cell phones. iPhone or Android? You decide:

The iPhone photo on the left comes from Tyler Knight of Mound, Minnesota, while the Samsung Galaxy image on the right was taken by meteorologist James Sinko on Castle Hill, Maine. Across the border in Saskatoon, Canada, Frank Lang recorded a must-see video using his iPhone 12.

At the apex of the storm, auroras descended as far south as Nebraska. Caryl Bohn photographed their faint red glow from the town of West Oak.

Subscribers to our Space Weather Alert system were notified the instant the CME hit. The alert was triggered by a sudden uptick in solar wind speed signalling the arrival of a shock front:

The plot shows data from NOAA’s DSCOVR spacecraft. When the CME passed by, the solar wind quickened by 120 km/s. At the same time, the plasma density tripled, and the temperature increased almost 10-fold. These are classic signs of a direct hit by a CME.

A New Meteor Shower: The Arids

Oct. 6, 2021: For thousands of years, Comet 15P/Finlay has been dive-bombing Earth’s orbit, leaving trails of dust on our planet’s doorstep, yet, strangely, there has never been a meteor shower. Until now. On Sept. 27th, Earth hit a stream of debris from Comet Finlay, and a meteor shower was born.

Above: An Arid meteor (inset) detected by the Cerro Tololo station of the CAMS Chile network on Sept. 29. [video] [more]

“It is called the Arid meteor shower, because the meteors radiate from the far-southern constellation Ara, the Altar,” explains Peter Jenniskens of the SETI Institute, whose meteor cameras in New Zealand and Chile detected the mini-outburst of 13 Arids.

It’s long overdue. Every 6 years, Finlay passes only 0.01 au from Earth’s orbit. Somehow, we’ve dodged the debris. “This is the first time we’ve ever seen meteors from the comet,” says Jenniskens.

The shower might not be over. Earth is poised to hit another of Finlay’s debris streams, and this one could trigger a storm.

“We predict an encounter sometime between Oct. 6th at 2200 UT and Oct. 7th at 0100 UT,” says astronomer Quanzhi Ye of the University of Maryland. “Forecasts range from ~50 to as many as 1100 meteors per hour.”

The debris was ejected by the comet in 2014 and 2015. In those years, something unexpected happened. Astronomers watching Finlay dive through the inner Solar System were surprised when the comet erupted–twice–more than quadrupling in brightness and producing massive jets of gas and dust.

Above: Finlay’s outburst in 2015 from “Bangs and Meteors from the Quiet Comet 15P/Finlay” by Ye et al. (Astrophysical Journal, Oct. 2015)

“Somewhere between 100 million and a billion kilograms of material were ejected–about the mass of a small hill,” says Ye, who has spent years studying Finlay and its debris.

If Earth grazes this material, a meteor storm could occur. Unfortunately for sky watchers, the best place to see it is in Antarctica. However, the timing also favors observers in parts of South America. “Our cameras are well-positioned to record anything that happens,” says Jenniskens.

UPDATE: The newly-discovered Arid meteor shower may have just produced an outburst over Antarctica. The University of Colorado Boulder operates a shortwave meteor radar at McMurdo Sound, and it detected a significant peak in meteor activity around 2300 UT on Oct. 6th. That matches the time Earth was expected to encounter a stream of debris from parent comet 15P/Finlay.