Physics of An Exploding Cosmic Ray Balloon

Feb. 21, 2019: On Nov. 14, 2018, the students of Earth to Sky Calculus launched a space weather balloon to measure increasing levels of cosmic rays in the atmosphere. At the apex of the flight, the balloon exploded and the radiation sensors parachuted back to Earth. A video camera on top of the payload recorded the pop:


These images illustrate recent findings about the physics of exploding balloons. In a Physical Review Letter entitled “Popping Balloons: A Case Study of Dynamical Fragmentation,” researchers from the Ecole Normale Supérieure in Paris report a series of laboratory experiments in which one balloon after another was popped and analyzed.

Basically, there are two ways a balloon can pop: along a single tear (the “opening regime”) or along many tears (the “fragmentation regime”). This video shows the two regimes in action. Which way the balloon decided to pop depends on the stress in the rubber membrane. When the stress is low, it can be relieved with a single tear, but when the stress is high, many tears are required to do the job.

Space weather balloons explode in the fragmentation regime, and the new research explains why. When space weather balloons are launched, they measure no more than 6 to 8 feet in diameter. By the time they reach the stratosphere, they have stretched into a sphere as wide as a house. So much stress requires many tears to release.

More information about this research is available from the American Physical Society.

Cosmic Rays Increasing for the 4th Year in a Row

Feb. 21, 2019: Cosmic rays in the stratosphere are intensifying for the 4th year in a row. This finding comes from a campaign of almost weekly high-altitude balloon launches conducted by the students of Earth to Sky Calculus. Since March 2015, there has been a ~13% increase in X-rays and gamma-rays over central California, where the students have launched hundreds of balloons.


The grey points in the graph are Earth to Sky balloon data. Overlaid on that time series is a record of neutron monitor data from the Sodankyla Geophysical Observatory in Oulu, Finland. The correlation between the two data sets is impressive, especially considering their wide geographic separation and differing methodologies. Neutron monitors have long been considered a “gold standard” for monitoring cosmic rays on Earth. This shows that our student-built balloons are gathering data of similar quality.

Why are cosmic rays increasing? The short answer is “Solar Minimum.” Right now, the 11-year solar cycle is plunging into one of the deepest minima of the Space Age. The sun’s weakening magnetic field and flagging solar wind are not protecting us as usual from deep-space radiation. Earth to Sky balloon launches in multiple countries and US states show that this is a widespread phenomenon.


Cosmic rays are of interest to anyone who flies on airplanes. The International Commission on Radiological Protection has classified pilots as occupational radiation workers because of cosmic ray doses they receive while flying. A recent study by researchers at the Harvard School of Public Health shows that flight attendants face an elevated risk of cancer compared to members of the general population. They listed cosmic rays as one of several risk factors. There are also controversial studies that suggest cosmic rays promote the formation of clouds in the atmosphere; if so, increasing cosmic rays could affect weather and climate.

Asteroid to Eclipse Sirius

Feb. 17, 2019: On Monday night, Feb. 18th, the brightest star in the night sky will disappear. It’s a rare eclipse of Sirius by asteroid 4388 Jürgenstock. As recently as two days ago, specialists thought the eclipse would be visible in a narrow corridor cutting across the central USA. New calculations, however, suggest a different path:

Sirius’s shadow will cross southern parts of Chile and Argentina, Central America and the Caribbean. This will happen on Feb. 18th between 09:11 pm PST and 09:27 pm PST.

According to David Dunham of the International Occultation Timing Association, the eclipse could last for as much as 1.8 seconds, with Sirius fading to minimum brightness for 0.2 seconds of that time. The angular diameter of Sirius is 0.006 arcseconds. Asteroid Jürgenstock is just a little wider: 0.007 arcseconds, so theoretically Sirius should be completely blocked. “But the asteroid may be a little larger or smaller than predicted, and it’s likely to be irregularly-shaped, so there is a good chance that even at the center, the star will not completely disappear,” notes Dunham.

Named after Venezuelan astrometrist Jürgen Stock, asteroid 4388 Jürgenstock orbits the sun in the inner regions of the asteroid belt between Mars and Jupiter. It is approximately 5 kilometers (3.1 miles) in diameter. Video recordings of the eclipse could help trace the shape of the distant space rock.

Resources: finder charts, observing tips, eclipse home page.

A Meteoroid Hits the Moon During Lunar Eclipse

Jan. 22, 2019: On Jan. 21st at 04:41:43 UT, a meteoroid slammed into the Moon. We know this because so many people witnessed the explosion. It happened during a total eclipse of the Moon, visible from five continents. Dr. Fritz Helmut Hemmerich photographed the eclipse from the Canary Islands of Spain and captured the fireball:

“This is a happy shot!” says Hemmerich. “The shot just before and the shot just a few seconds later show nothing. The fireball was short-lived and I’m glad I caught it in this 2-second exposure.”

Dozens of reliable images and videos of the impact have surfaced in the days since the eclipse. Analyzing one sharp image taken by Christian Fröschlin of the Netherlands, geologist Justin Cowart has estimated the selenographic coordinates of the impact site: 29.47S, 67.77W +/- 4km. This puts it just to the west of the lunar crater Lagrange H. NASA’s Lunar Reconnaissance Orbiter may be able to use such coordinates to target its cameras and photograph the crater.

Meteoroids hit the Moon all the time. Literally. NASA has been observing impact flashes since 2005. Recently, other groups in Europe have joined the hunt. Flashes are typically recorded once every 2 to 3 hours of observing time. Impactors range in size from softballs to boulders, liberating energies equal to tons of TNT when they strike.

Above: The impact flash, photographed by Hunter McWilliams of Lubbock, Texas

The rare thing about this strike is that it was photographed during a full Moon, when lunar glare usually overwhelms the glow of any fireball. During the eclipse, Earth’s shadow turned lunar day into almost-night for an hour, allowing the fireball to be seen.

Readers, were you taking pictures of the eclipse around 04:41 UT? Check your photos. You might have captured an explosion. Submit images here.

Realtime Eclipse Photo Gallery

Earth’s Shifting Magnetic Pole May be Confusing Your Cell Phone

Jan. 16, 2019: Pick up your cell phone and look at it. That rectangular marvel of modern technology contains thousands of lines of code. Among them is the World Magnetic Model (WMM)–a program that helps your phone navigate.  And it’s in a bit of trouble. Researchers have announced that the WMM needs an emergency update because Earth’s magnetic field is changing.


Savvy backcountry hikers have long known that compass needles don’t really point north. The magnetic north pole is displaced hundreds of miles from the true north pole and, to make matters worse, it wanders unpredictably from year to year. To find true north in the continental USA, you have to correct compass directions by as much as 20 degrees using a special “declination table.”

The World Magnetic Model is a computer program that makes this correction for you. It improves the navigation of devices ranging from nuclear submarines to common smartphones.

“The WMM is the standard magnetic model used for navigation by organizations such as NATO, the Ministry of Defence, and the US Department of Defense, and also by smartphone operating systems such as Android and iOS,” explains Will Brown of the British Geological Survey’s Geomagnetism Team, which produces the model in collaboration with NOAA of the USA.


“When you open your smartphone’s map app, you may see an arrow pointing which way you’re facing, and there’s something quite clever going on underneath,” he continues. “Your phone contains a magnetometer that is measuring the Earth’s magnetic field. In order to make sense of this information, Android and iOS operating systems use the WMM to correct the measurements to true north.”

Normally the World Magnetic Model is updated every 5 years. For decades that’s been often enough to track natural changes in our planet’s magnetism caused by fluctuations in Earth’s molten core. But suddenly things are changing faster than before.


Annual rate of change of declination for 2015.0 to 2020.0 from the World Magnetic Model (WMM2015). This information is about to be updated by a new WMM.

“Since late 2014, Earth’s core field has varied in an unpredicted, and currently unpredictable, manner [including a sudden change in declinaton called a ‘geomagnetic jerk‘ in 2014/2015],” says Brown. “The aim of the WMM is to be globally accurate within 1 degree of declination, but we were going to exceed that limit in only 3 years.” That’s why, for the first time, they are issuing an update to the WMM before the usual 5 year mark in 2020.

The new model is based data from a global network of 160 surface observatories and satellites in low-Earth orbit such as ESA’s Swarm mission. It was supposed to be released on Jan. 15th but has been delayed until Jan. 30th because of the partial shutdown of the US government.

A Collision in the Asteroid Belt

Jan. 14, 2019: Last week, astronomers working with the ATLAS project in Hawaii announced an astonishing change to asteroid 6478 Gault. The space rock had sprouted a tail. It is now gliding through the asteroid belt giving every appearance of being a comet. On Jan. 9th, Damian Peach of Selsey UK photographed the 6478 Gault and its 400,000 kilometer-long tail:

“This is a 60 minute sequence of images, which I captured using a 20-inch telescope,” says Peach.

What happened to 6478 Gault? A clue may be found in its lineage. Asteroid Gault is a member of the Phocaea family, a swarm of rocks in the inner asteroid belt that formed as a result of inter-asteroid collisions some 2.2 billion years ago. The family gets its name from its most massive survivor, 25 Phocaea, which is about 75 km in diameter.

Gault’s tail may be a result of a recent collision. Researchers with the ATLAS project have looked at images of Gault in Dec. 2018 and Jan. 2019. Extrapolating its appearance backwards in time, they suggest that Gault hit another object in the asteroid belt in Nov. 2018. If that idea is correct, the tail would be debris from the crash.

Asteroid Gault was discovered in 1988 by the famous astronomer couple Carolyn and Eugene Shoemaker at the Palomar Observatory in California. For the next 30 years, the 4-km wide space rock did little to attract attention. Now, astronomers around the world are eagerly monitoring 6478 Gault to see what happens next. Stay tuned.

Readers, would you like to take pictures like Damian Peach? He’s willing to teach you how. Subscribe to his Patreon page for expert tutorials.

Realtime Space Weather Photo Gallery

FULL MOON VALENTINE’S PENDANT: Poets, lovers, and artists have long known this simple truth: Nothing is more romantic than a full Moon. Now you can give the full Moon as a Valentine’s Gift–the full Moon space pendant, that is. This one flew to the stratosphere on Dec. 26, 2018, onboard an Earth to Sky Calculus cosmic ray balloon:

You can have it for $99.95. The students are selling these spherical glass pendants to support their cosmic ray ballooning program. Each one comes with a Valentine’s card showing the pendant in flight and telling the story of its journey to the edge of space and back again.

Far Out Gifts: Earth to Sky Store
All sales support hands-on STEM education

Partial Solar Eclipse

Jan. 5, 2019: When the sun rises over Beijing on Jan 6th, something will be missing. As in … 31.5% of the sun. On that morning, the New Moon is going to pass in front of the sun, off center, turning the usual disk into a crescent. This movie created by graphic artist Larry Koehn shows the eclipse zone, which includes significant population centers in China, Korea and Japan:

This is not a total eclipse. At maximum, the Moon will cover 71% of the sun–a deep crescent that may be seen by the residents of Srednekolymsk, a small town in northern Russia. Elsewhere, such as Tokyo, Seoul, and Beijing, less than half of the sun will vanish behind the black lunar disk. The zone of visibility stretches from coastal China to the Aleutian islands of Alaska.

Sunrise observers of the eclipse could witness scenes like this:

James Kevin Ty took this picture from the Philippines during a similar eclipse in Jan. 2010. “The low-hanging sun was dim and I didn’t need any special filter to photograph it using my Canon 350D,” says Ty. “In the foreground, a young couple sat together in a boat enjoying the romantic view.”

Many people watching the eclipse at sunrise or sunset may be tempted to stare at the relatively dim sun. BE CAREFUL. Even the tiniest sliver of sun left uncovered by the Moon can hurt your eyes. Eclipse glasses are recommended for safety.

Observing tip: Try looking down. Beneath a leafy tree, you might be surprised to find hundreds of crescent-shaped sunbeams dappling the grass. Overlapping leaves create natural pinhole cameras, each one casting an image of the crescent-sun onto the ground beneath the canopy. Note the crescent-eyed turkey shown above. Partial eclipse shadow play is safe–and lots of fun.

During the eclipse, photographers in Asia will be posting photos to Monitor our realtime photo gallery for the latest:

Realtime Solar Eclipse Photo Gallery

China Lands on the Farside of the Moon

Jan. 3, 2019: Going where no nation has gone before, today China successfully landed a rover on the farside of the Moon. The Chang’e 4 lunar probe touched down in the South Pole-Aitken Basin, the largest, deepest and oldest known crater in the solar system, at 10:26 am Beijing time on Jan. 3rd.

From Earth, we can see only one side of the Moon. The other side, the farside, is perpetually hidden from view. Apollo astronauts have flown over the farside of the Moon, and many satellites have photographed the Moon from behind–revealing it to be a rugged, heavily cratered landscape startlingly different from the side we typically see.

China’s rover will be the first to explore a farside crater, probing it with ground-penetrating radar and measuring its mineral composition with an infrared spectrometer. If water is present, the rover might find it.

The first pictures of the landing site have been relayed to Earth by the Queqiao satellite, which China launched in May 21, 2018, specifically for this purpose. This is what the South Pole-Aitken Basin looks like from the inside:

The landing was remarkable. Mission control had no line-of-sight contact with the lunar farside, so the lander had to perform many complex maneuvers autonomously. (1) As it descended to an altitude of about 2 km, onboard cameras captured the shadows of objects on the lunar surface, identifying large obstacles such as rocks and craters so the probe could avoid them. (2) At 100 meters up, the probe hovered to identify smaller obstacles and measured the slopes on the surface. Its computer calculated again and selected the safest site. (3) At 2 meters above the surface, the engine stopped. Then the golden lander with a silver rover on top touched down on the desolate gray surface with four legs, throwing up some dust. The probe performed the entire landing process, lasting about 12 minutes with no intervention from ground control.

Realtime Space Weather Photo Gallery

GIFTS FROM THE EDGE OF SPACE: The students of Earth to Sky Calculus are about to kick off a new year of cosmic ray balloon launches, continuing a 5-year campaign to monitor increasing levels of radiation in Earth’s atmosphere. You can help. Buy any gift item from the Earth to Sky Store and we’ll give you 10% off to celebrate the New Year.

All items in the Earth to Sky Store have flown to the edge of space onboard cosmic ray balloons. Each one comes with a greeting card showing the item in flight and telling the story of its journey. All sales support the Earth to Sky Calculus cosmic ray ballooning program and hands-on STEM research.

Far Out Gifts: Earth to Sky Store
All sales support hands-on STEM education

First Images of Ultima Thule

Jan. 2, 2019: The first high-resolution images of Ultima Thule have reached Earth following New Horizons’ historic flyby on New Year’s Day. Hot off the presses, the photos reveal a pair of roughly spherical planetestimals stuck together in the middle. The contact binary strangely resembles BB-8:

“This flyby is a historic achievement,” says New Horizons Principal Investigator Alan Stern of the Southwest Research Institute in Boulder, Colorado. “Never before has any spacecraft team tracked down such a small body so far away in the abyss of space. We’re getting our first close-up look at ancient planetesimals.”

Planetestimals are the building blocks of planets. Here in the inner solar system, no pristine examples remain for us to study. They have been swallowed by planets, hammered by asteroids, and scorched by solar radiation. Ultima Thule, however, has been preserved in the deep freeze of the outer solar system for more than 4 billion years. It is truly a relic of the genesis of planets.

Mission scientists believe that Ultima Thule formed by accretion. A swarm of smaller planetesimals gathered under the pull of their own meagre gravity to form two spherical bodies, medium-sized planetesimals which themselves slowly bumped together and stuck. The result was Ultima Thule.

This is just the beginning of Ultima Thule’s revelations. First images released today have a resolution of about 140 meters per pixel. Images arriving in the days and weeks ahead will be as much as 5 times sharper, possibly revealing craters, hills, landslides, rilles and other unknowns.

New Horizons also scanned the area for tiny moons–the debris of the original swarm that gave birth to this strange object. Detections, if any, will be revealed in future transmissions from the spacecraft.

Browse: Slides from the science briefing and latest images from New Horizons

Rare Video of Clouds in the Stratosphere

Dec. 27, 2018: The habits of a weatherman are hard to break–even on holiday. So it was that Dutch meteorologist Jacob Kuiper found himself outside on Christmas morning, looking up. What he saw amazed him. “The sky was filling with strange clouds,” says Kuiper. “At first I thought they were some form of cirrus, but these clouds were uncommonly wavy with unusual curls. When I saw the telltale flashes of color, I realized they must be polar stratospheric clouds (PSCs).”

Kuiper made a time-lapse video of the display. Note the hypnotic waves and how, at the 25 second mark, ordinary clouds may be seen scudding far below them:

Polar stratospheric clouds are not your ordinary Christmas clouds. Indeed, they have little to do with regular weather, floating so high above Earth that even airplanes cannot reach them.

Normally, the stratosphere is free of clouds–completely transparent. It’s very dry up there with a wide separation between molecules of water. When the temperature drops to around -85ºC, however, those sparse molecules begin to reluctantly gather, forming crystals of ice that become PSCs.

“I have been working in the National Meteorological Office in the central part of The Netherlands (KNMI) for 40 years,” says Kuiper. “Only twice have I seen a display of stratospheric clouds this widespread. It was thrilling. I didn’t expect the stratosphere over our country to be cold enough, but one of the stratosphere scientists in our Met. Office confirmed my idea. He also was quite surprised.”

Above: PSCs inside the Arctic Circle in 2017. Photo credit: Mia Stålnacke of Kiruna, Sweden

Tiny ice crystals in PSCs can produce episodes of iridescence so brilliant that they are sometimes mistaken for auroras. The display Kuiper recorded contained only a few brief flashes of those colors–just enough for an identification.

PSCs come in two varieties: Type I contains hydrated droplets of nitric acid and sulphuric acid. These are chemicals that can destroy ozone. Indeed, an ozone hole formed over the UK in Feb. 2016 following an outbreak of Type 1 PSCs. Type II PSCs are icy and colorful, and they do little damage to the ozone layer. The clouds Kuiper witnessed may be a mixture of both.

The display was so rare that researchers in the Met Office conducted an extra round of Christmas radio soundings to probe the stratosphere. They are still processing the data, so stay tuned!

Realtime Space Weather Photo Gallery

A GIFT FROM THE EDGE OF SPACE: The students of Earth to Sky Calculus are about to kick off a new year of cosmic ray balloon launches, continuing a 5-year campaign to monitor increasing levels of radiation in Earth’s atmosphere. You can help. Buy any gift item from the Earth to Sky Store and we’ll give you 10% off to celebrate the New Year.

All items in the Earth to Sky Store have flown to the edge of space onboard cosmic ray balloons. Each one comes with a greeting card showing the item in flight and telling the story of its journey. All sales support the Earth to Sky Calculus cosmic ray ballooning program and hands-on STEM research.

Far Out Gifts: Earth to Sky Store
All sales support hands-on STEM education