How to find the center of the Milky Way … and what lurks there

Want to know where the center of our galaxy is? Face south around nightfall in late July and find the Teapot of Sagittarius about ‘two fists’ to the left of bright Antares in Scorpius. The core is a blank bit of sky just above the spout near the 4.5 magnitude star 3 Sagittarii.  Stellarium

Ever stared straight at the heart of the Milky Way galaxy? Give it a try this coming week. With dark skies and no moon, the time is right.

Artist’s view of the 4 million mass black hole at the center of the Milky Way. The hole measures about 28 million miles in diameter. Credit: NASA

Notice I didn’t say into the heart. No human eyes can penetrate the veil of interstellar dust that cloaks the galactic central point 26,000 light years away in the direction of the constellation Sagittarius. Only X-ray, gamma ray and radio telescopes can ‘part the way’ and expose the galaxy’s dark secret which astronomers call Sagittarius A*.

There, at the center of it all, lies a black hole with a mass of 4 million suns. The innermost 3.2 light years centered on the black hole swarms with thousands of aged stars and about 100 fresh-born ones, some in very tight orbits about the hole. Gas clouds abound, and there’s at least another smaller black hole nearby.

NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, captured these first, focused views of the supermassive black hole at the heart of our galaxy in high-energy X-ray light. Known as Sagittarius A* (A star), the bright flare formed when Sgr A* was consuming and heating matter. The background image, taken in infrared light, shows its location. Credit: NASA

Occasionally the central black hole flares to life when a random asteroid, gas cloud or stray star passes too close and gets ripped to pieces before disappearing down the gullet of the beast. Heated by friction, the material sends out every type of light from visible to X-rays and gamma rays. But no one can see all the excitement because it’s hidden by light years of dust grains. To the eye, the center looks nondescript and static, but nothing could be further from the truth.

The Milky Way is beautiful to gaze at this time of year. Take a drive to the country and park your car where the sky is dark and open to the south. At nightfall, you’ll see a fiery-hued star a few fists up from the southern horizon at nightfall. That’s Antares in Scorpius. Now shift your gaze two fists to the left or east and see if you can spot the outline of the Teapot. Once you’ve found it, galactic center lies just above the spout.

Closeup of the Spout showing a couple bright star clusters and the Lagoon Nebula, a rich star-forming region. Credit: Bob King

Though the center remains hidden, large chunks of the Milky Way hover like clouds against the black sky. Every puffy piece is comprised of billions of distant stars the light of which blends together to form a misty haze. Here and there are smaller knots. These are individual gas clouds called nebulae and bright star clusters. A pair of 40-50mm binoculars will show many of these wonders and countless fainter stars plainly. If we could magically remove the dust between us and the galactic center, the rich intensity of stars in the Sagittarius direction would be bright enough to cast shadows at night.

Take it all in. Let your eyes follow the arc from the southern horizon clear up across the eastern sky and back down to the northeastern horizon. We live here – can you believe it?

Moon nestles in Hyades then departs for Venus

The crescent moon slips in front of the Hyades star cluster only a degree from Aldebaran tomorrow morning. Don’t miss the other bright star cluster, the Pleiades, just above. Look low in the northeastern sky about an hour before sunrise to catch the scene. Stellarium

That old devil moon’s up to its old tricks again. Tomorrow morning, early risers will see it tucked inside the V-shaped face of Taurus the Bull. Better known as the Hyades star cluster, look for the crescent to pass just 1° north of the bright star Aldebaran. A pair of binoculars will enhance the view by pulling in more stars and revealing details in the spooky, earth-lit moon. Sunlight illuminates the lunar crescent, but the remainder is light reflecting off Earth out to the moon and back again.

The crescent is lit by the sun while the remainder glows dimly from twice-reflected light called earthshine. Credit: Bob King

To the eye, ‘earthlight’ looks smoky gray and nearly featureless though binoculars will show the lunar seas and larger craters. The quality of the light mimics a lunar eclipse but instead of red we see the pale blue glow of sunlight reflecting back from our planet’s oceans.

At 153 light years, the Hyades is the nearest star cluster to our solar system, one of the reasons you can see it without a telescope. Aldebaran appears to be a full-fledged cluster member, but it’s a ruse. The bright, ruddy star lies much closer to us along the same line of sight.

Venus and a very thin crescent moon on July 24 about 45 minutes before sunrise low in the northeast. Stellarium

The Hyades were born in a dense cloud of interstellar dust and gas 625 million years ago around the time underwater life flourished in the late Precambrian era. When you gaze at the cluster tomorrow, the light that touches your retinas left the Hyades the same time Abraham Lincoln took office.

The moon moves on toward Venus after vacationing in the Hyades, passing south of the planet on Thursday morning. It will be extremely thin that morning and should make a pretty sight for anyone looking low in the northeastern sky 45 minutes before sunrise.

Shhh! Don’t wake the sun

Contrast these views of the nearly spotless sun on July 16-17, 2014 with a picture taken about two weeks earlier (below). Credit: Giorgio Rizzarelli

Who doesn’t enjoy a nap on a lazy summer afternoon? That’s what the sun’s been up to past few days. Instead of a steady parade of sunspots, it put its pencils away and went to sleep. For a time on July 17 not a singe magnetic blemish marred the entire Earth-facing hemisphere. The last time that happened was nearly 3 years ago on Aug. 14, 2011.

Ten groups including three visible with the naked eye dot the sun on July 8, 2014. Credit: NASA

The solar blank stare lasted but a day; by the 18th two small groups emerged. Today three little spot clusters have emerged but again, they’re on the small side.

I think the reason the sun looks so stark is that only two weeks ago nearly a dozen sunspot regions freckled the disk including three visible with the naked eye with a safe solar filter.

These ups and downs aren’t unusual unless this downturn continues for weeks. Expect more bubbles of magnetic energy to rise from beneath the glaring surface of the sun called the photosphere and spawn fresh groups soon. Because we now have eyes on the farside of the sun courtesy of the dual STEREO solar probes, we know the complete story. There are at least seven spotted regions in hiding there today.

Sunspot numbers are plotted for the last three solar cycles through the present. The double peak of the current cycle is shown. Credit: NASA

Sunspots and flares peak approximately every 11 years. We’re still riding the roller coaster near the top of the arc after the most recent solar maximum in late 2013. Some maxima are strong, others weak. The current max – Cycle 24 – is the weakest since Cycle 14 in February of 1906 and one of the wimpiest on record. Occasionally a cycle will have two peaks like the current one. The first peak occurred in Feb. 2012 and the second just this past June. What makes Cycle 24 even more unusual is that the second peak is higher than the first – the first time this has ever been recorded. Like people, every maximum has a personality of its own.

Doug Bieseker of the NOAA Space Weather Prediction Center has analyzed historical records of solar activity and he finds that most large events such as strong flares and significant geomagnetic storms typically occur in the declining phase of solar cycles—even weak ones, so don’t give up hope for some great auroral displays ahead.

A coronal mass ejection blew off on the farside of the sun early this morning July 20. It appears to envelop Jupiter, but the planet is 490 million miles in the background. SOHO uses an occulting disk to block the brilliant sun. Credit: NASA/ESA

The sun’s got a buddy this week – Jupiter! We can’t see the planet from the ground because it’s swamped by solar glare, but the Solar and Heliospheric Observatory (SOHO) has a great view from space. Watch the sun approach from the right and pass the planet over the next few days. After the 24th, Jupiter will move into the morning sky.

Let’s face it, comets are just weird

Comet 67P/C-G photographed from a distance of about 7,500 miles (12,000 km) on July 14 the European Space Agency’s Rosetta spacecraft. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Mesmerizing. The recent video of Comet 67P/Churyumov-Gerasimenko tumbling end over end looks like a boot booted into space. 36 images were used to create the brief time lapse which makes it look like as if the comet’s spinning rapidly. Its actual rotation period is 12.4 hours. Still, the extremely irregular shape of the 67P/C-G poses new challenges for the Rosetta team as they contemplate how to safely set down the Philae lander on such an irregularly shaped body come November 11.

Questions abound on how 67P/C-G got its peculiar shape. Most familiar solar system bodies like the planets and many of their moons are spherical or nearly so. Gravity’s the sculptor here. If an object’s about 240 miles (385 km) or larger in diameter, self-gravity will pull everything to the center and collapse the body into a sphere. Small objects like comets and most asteroids just don’t have enough material to ‘go spherical’. Comet 67P/C-G is only a few miles across, so it’s free to assume a variety of shapes.

These are all the comets we’ve seen up close so far by sending spacecraft there. All are small and most non-spherical. Credit: NASA/ESA

This all reminds me of a famous anecdote about Fritz Zwicky, a brilliant but prickly Swiss astronomer who worked most of his life at Caltech. He pioneered the use of supernovae as ‘yardsticks’ to measure distances to faraway galaxies and was the first to propose the existence of dark matter. Zwicky didn’t get along with everyone at Mt. Wilson Observatory, calling the astronomers there “Spherical bastards”. Why? “Because they’re bastards no matter how you look at them.”

Comet 8P/Tuttle, believed to be a contact binary, imaged by Arecibo radar Dec. 29, 2007-Jan. 5, 2008. Credit: Arecibo Observatory

ANYWAY … comets, being small icy bodies, come in a great variety of shapes from round to bowling pins to rubber duckies. Many ideas have been tossed around as to how 67P looks the way it does. I haven’t taken a poll but would suspect many astronomers would consider the comet a contact binary, two separate comets on convergent paths moving slowly enough that they melded together into one larger object.

Comet 67P/C-G and the Rosetta spacecraft to scale. The comet is about 4 km (2.5 miles) across. Credit: ESA

We also see contact binaries among the asteroids, but ice makes comets unique. Heat from the sun vaporizes that ice and carves away at the comet’s surface. Could eons of solar heating have shaped Churyumov-Gerasimenko? Comets are also fragile compared to most asteroids; some even crumble apart as they near the sun. It’s possible that vaporization of subsurface ices left parts of 67P in a weakened state which then crumbled away to sculpt its peculiar outline. Other possibilities include a near-catastrophic impact or gravitational stretching  during close encounters with Jupiter or Saturn.

Starting August 6 when Rosetta enters orbit around 67P, scientists will have more than a year to study it up close. Perhaps then we’ll get some more answers on its shapely origins. For instance, if we discover that each lobe of 67P has a different density or composition, the contact binary explanation would make a good fit. For now, let’s just say that comets’ weird shapes make them even more lovable.

Odd glows around sun may be caused by Canadian forest fires

A large, pale blue aureole or disk surrounds the sun this morning July 18 in a sky filled with high-altitude smoke from forest fires burning in Canada’s Northwest Territories. Wide-angle 15mm lens view. Credit: Bob King

It happens every summer. Forest fires in Canada pump out vast quantities of smoke which are carried by winds to the south and east. Arriving days later over the northern Great Plains and Midwest, the blue sky soon turns a pallid gray.

Smoke from forest fires near Faber Lake in the Northwest Territories streams south in this photo taken July 7, 2014 by NASA’s Terra satellite. Credit: NASA

The smoke spreads in subtle ripples and bands and dims sun and stars alike. Technically, the sky is clear, and that’s what you’ll hear from the weather service, but the smoky haze creates an overcast of its own. Sunlight is less intense, while the solar disk glows pale yellow-orange compared to its normal white-yellow. It may even disappear from view well before sunset, fading away in the fiery haze.

Wide-angle photo this morning showing the blue aureole and brownish outer ring around the sun. Could smoke particles be responsible for the appearance? Credit: Bob King

Early this morning, under faux clear skies, I noticed an unusual pale blue disk or aureole around the sun about four fists (40 degrees) wide. Beyond that lay a wide, darker ‘ring’ tinted a pale gray-brown. Forest fires release gobs of minute smoke particles and oil droplets into the atmosphere which, like the ash from volcanic eruptions, can occasionally color the sun or moon blue.

Patches and bands of smoke from forest fires are seen in this National Weather Service satellite photo taken this morning July 18, 2014. Credit:NASA

It works like this. Particles that are about 1 micron across (1/1000 of a millimeter) are the same size as the wavelength of red light. The sun pours out all colors of light, but when the red portion strikes the ash or smoke, it’s scattered about the sky. The shorter wavelength blue light isn’t affected and continues to pass directly to our eyes, coloring the sun a pale blue. In effect, the particles act like a blue filter.

Bishop’s Ring around the sun due to volcanic ash of the Eyjafjallajökull volcano on Iceland. Photographed from Leiden, the Netherlands on May 18, 2010. Credit: Marco Langbroek

I’ve seen no blue moons or suns yet, but I wonder if the blue aureole might be the result of smoke particles. It resembles a phenomenon called Bishop’s Ring seen around the sun during volcanic eruptions and created by ash and sulfur droplets. Notice though the ball of the sun remains red-orange, indicating that the smoke particles are not the right size to create a blue sun. At least not yet.

A red sky sunset Friday evening July 18. Colors are enhanced from airborne smoke. Credit: Bob King

If you live where the sky is affected by the smoke of distant fires, keep an eye on the sun, moon and sky for unusual colors, disks and rings. We’d love to hear what you’re seeing.

Abundant high altitude dust on Mars scatters red light away from the sun, lending both the solar disk and sky near it a pale blue. Photo taken on May 19, 2005 by the Spirit Rover. Credit: NASA/ JPL-Caltech

My blue disk this morning also reminded me of the blue aureole around the rising sun on Mars taken by the Spirit Rover. Dust in the Martian atmosphere scatters red light like much like ash and fire smoke do on Earth. Blue sunrises and sunsets there are probably fairly common.

Can a boot print on the moon last a million years?

Buzz Aldrin first photographed a pristine patch of the lunar soil (left) before stepping onto it with his boot (right). The fine-grained consistency of the soil crisply records details in the tread. It’s estimated the impression will last 1 to 2 million years. Click to enlarge. Credit: NASA

One of my favorite pictures taken during the Apollo 11 mission to the moon 45 years ago was Buzz Aldrin’s famous boot print in the lunar soil. While it looks like he might have been doing it just for fun, pressing his boot into the fine, powdery soil had a purpose.

Aldrin and Neil Armstrong were asked to carefully observe and assess the properties of the regolith. Notice things like how deep their boots sank in the gritty stuff as well as how it affected their ability to walk about on the surface. Close up photos were taken, including 3D stereo images. Mission control didn’t leave a pebble unturned. It was all part of the mission’s Soil Mechanics Investigation.

After taking the first boot print photo, Aldrin moved closer to the little rock and took this second shot. The dusty, sandy pebbly soil is also known as the lunar ‘regolith’. Click to enlarge. Credit: NASA

The soil on the Moon is very fine-grained, with more than half of all grains being dust particles less than 0.1 millimeters across. It not only adhered to their boots in fine layers but provided good traction. Typically the astronauts boots sunk down only one-half to one inch (1.5-2.5 cm) into the lunar regolith.

In this view taken with a camera mounted on the Lunar Module (LEM), Buzz Aldrin takes the picture of his boot next to the rock seen in the earlier photo. The first boot print is just behind his foot. Credit: NASA

Even though the moon is airless, windless and essentially waterless, erosion happens. Bombardment by protons from the solar wind and micrometeorites (bits of interplanetary dust shed by comets and spalled from asteroids) never stops.

Earth’s atmosphere slows micrometeorites, allowing them to drift down gently to the surface. No so on the airless moon, where space grit grinds away mercilessly on the lunar rocks. Before the unmanned Surveyors landed, some astronomers thought that moon dust might be so deep it would swallow a spacecraft. Before Neil Armstrong made his historic ‘first step’, he first tested the ground to make sure it was firm.

More than 3.5 billion years of bombardment by micrometeorites have rounded the outlines of the lunar Apennine Mountains. The lunar module Apollo 15 ‘Falcon’ in the foreground. Click to visit NASA’s Apollo 11 image archive.  Credit: NASA

Their surfaces are riddled with countless ‘zap pits’ from micrometeorites that strike the surface at thousands of miles an hour. Slowly, inexorably the mountains are ground into more rounded forms. It’s estimated that micrometeorites churn the lunar soil once every 10 million years. Aldrin’s boot prints and for that matter, all the impressions in the dust left by the astronauts and their equipment, will remain in place for 1 to 2 million years. Incredibly long by human standards.

Extreme temperature differences between daytime highs and nighttime lows also must play a part in breaking apart rocks and furthering erosion. At the lunar equator, mean surface temperatures reach almost 260 ºF at noon and then drop to -279 ºF during the night. The moon also gets whacked by larger meteorites that send up plumes of dust that fill in crevices and soften sharp edges.

Sunday marks the 45th anniversary of the Apollo 11 lunar landing, when our toes touched a world other than Earth. While astronauts left countless impressions in the lunar dust, Aldrin’s single boot print has come to symbolize humanity’s first steps from the cradle of Earth into that big thing we call the universe. I hope we can return soon.

Curiosity finds big iron meteorite on Mars

NASA’s Curiosity Mars rover took this photo of an iron meteorite called “Lebanon,” similar in shape and luster to iron meteorites found on Mars by the Spirit and Opportunity rovers. The smaller piece in the foreground is called “Lebanon B.” The circles are high resolution views taken with the Remote Micro-Imager. Click to see them. Credit: NASA/JPL-Caltech/LANL/CNES/IRAP/LPGNantes/CNRS/IAS/MSSS

It’s not the first meteorite found on the Red Planet, but it’s sure the largest. A 6-foot-long (2 meters) iron meteorite named ‘Lebanon’ was spotted by Curiosity’s cameras poking its head out of the Martian soil on May 25th. NASA released the stunning portrait this afternoon.

4.971 kg Sikhote Alin iron meteorite that fell in 1947 in the then Soviet Union. It displays beautiful regmaglypts. Credit: Svend Buhl

With its gunmetal sheen and numerous ‘thumbprints’ it looks identical to many fresh iron meteorites found on Earth. Those Swiss cheese-like holes called regmaglypts form in a couple different ways. Softer, less heat resistant minerals like iron sulfide (troilite) riddle some iron meteorites.

During the plunge through a planet’s atmosphere, the surface of a meteoroid heats up, melts and gets sculpted by powerful, super-heated air. Softer materials melt away or ‘ablate’, giving the meteorite its classic thumbprint texture.

Martian winds and weather could also have eroded out the softer materials to create the cavities. Perhaps both processes were (and still are) at play. The circles are individual,high-resolution photos taken by Curiosity’s Remote Micro-Imager. When you click the image above, you’ll be able to explore the iron’s surface in great detail.

This view of a rock called “Block Island,” the second largest meteorite found on Mars, comes from the panoramic camera on Opportunity. It’s about 26 inches (67 cm) across. Credit: NASA/JPL

This is Curiosity’s first meteorite discovery and the 8th and largest found on the planet. The earlier generation Spirit Rover stumbled onto two potential meteorites – Allan Hills and Zhong Shan – inside Gusev Crater in 2006. They resembled those found by the rover’s twin, Opportunity, which uncovered five confirmed iron meteorites. Here’s Opportunity’s space rock booty to date:

Heat Shield Rock - Found in 2005. Renamed Meridiani Planum meteorite for its location. Type: iron meteorite
* Block Island – 2009 / iron meteorite
* Mackinac Island – 2009 / iron meteorite
Shelter Island - 2009 / iron meteorite
* Oileán Ruaidh - 2010 / iron meteorite

While irons aren’t the most common meteorite – stony meteorites are – they resist erosion better and stand out from the general rocks. That’s probably the reason all those found so far have been metallic.

What the? Rosetta’s comet is two comets in one!

Check this out! Rosetta’s comet is a contact binary, made of two separate comets that approached one another slowly enough sometime in the past to stick together as one. Click to enlarge. Credit: ESA /Rosetta /MPS for OSIRIS Team MPS /UPD /LAM /IAA /SSO /INTA / UPM /DASP /IDA

This just in. Comet Churyumov-Geramsimenko, the comet the Rosetta probe’s been chasing for the past 10 years, is really a double, what astronomers call a contact binary. Sometime in the past, two comets – possibly leftovers from the breakup of one larger object – approached one another at an estimated speed of 10 feet per second (3 meters/second) and stuck together to make the current day comet with a diameter of 2.5 x 2.2 miles (4 x 3.5 km).

A tighter crop on the comet shows its wild shape. Can’t wait for the closeups! Credit: ESA /Rosetta /MPS for OSIRIS Team MPS /UPD /LAM /IAA /SSO /INTA / UPM /DASP /IDA

Planetary Society blogger Emily Lakdawalla writes that the comet’s dual form could present some difficulties for the Philae lander, set to drop down on the comet’s surface this November 11:

“Philae navigator Eric Jurado as saying that “navigation around such a body should not be much more complex than around a nucleus of irregular spherical type, but landing the Philae probe however, could be more difficult, as this form restricts potential landing zones.”

I think the images are simply amazing and couldn’t wait to share them. Wow!

Catch Comet Jacques near Venus at dawn

Venus will help us find Comet Jacques in Taurus an hour and a half before sunrise tomorrow morning July 16, 2014. The comet will be near the naked eye star Beta Tauri during the next week. Source: Stellarium

I don’t take getting up at dawn in summer lightly. After all, it means you’ve got to set the alarm for the ungodly hour of 4 a.m. (even earlier if you live in the northern U.S. or southern Canada.) But I wanted to alert you to the return of Comet C/2014 E2 Jacques.

Comet Jacques was taken on July 7, 2014 displays a small, condensed head or coma and two tails – a dust tail to the left and ion or gas tail to the right. Credit: Gerald Rhemann

Jacques disappeared in evening twilight a month ago, passed closest to the sun on July 2 and has recently returned to view low in the northeastern sky at dawn. Still stoked from its solar encounter, the comet shines at magnitude +6, the naked eye limit.

Don’t expect to see it yet without optical aid however. Jacques flirts with morning twilight and only climbs to around 10° (one fist held at arm’s length) the next couple mornings. Low haze and dust will make it look fainter, but not so much that a pair of 50mm binoculars might catch it.

Detailed map with stars shown to magnitude 7. Comet Jacques will be near a great ‘skymark’ this coming week, the star Beta Tauri. Use it and Venus to guide you there. Comet positions are marked every five days; Venus shown for July 16.  Click to enlarge and then print out a copy for outdoor use. Source: Chris Marriott’s SkyMap

We’re fortunate to have Venus and the star Beta Tauri to help guide us to the comet. The critical requirement for seeing Jacques, whether it be in binoculars or more likely in a small telescope, is an open view of the northeastern sky.

Timing is also important. In the northern U.S., the comet will be a little higher in the sky but observers will have to compete with earlier and longer twilights. The southern U.S. has the edge for the moment with the comet a little better placed in a darker sky.

Views will improve for everyone over the next few weeks as Jacques pulls away from the sun, buoyed along by the seasonal drift of the stars and its own westward motion.

Indications are that the comet will remain near the naked eye limit through early August, so we may really get a chance to see it without optical aid from rural skies. In any case, binoculars should reveal it as a small fuzzball rolling across Auriga and Perseus.

The thin crescent moon drops by the neighborhood on July 23, a great morning to seek out the comet. Source: Stellarium

By mid-August, Jacques will fade but remain visible in the evening sky through the remainder of the year. I hope you become fast friends with this blurry blob soon!

* UPDATE July 16, 2014 – Checked the comet this morning and although there were a few clouds, I wasn’t able to see it in 10×50 binoculars. Too much twilight here in the northern U.S. ! But the view in the telescope was excellent. Jacques was an obvious fuzzy glow with a bright center a couple degrees below Beta Tauri even in dawn light. I estimated magnitude 6.

Apollo revisited: Cosmic rays buzz Buzz Aldrin’s eyes

Buzz Aldrin, Apollo astronaut and second to walk on the moon, demonstrates the ALFMED device astronauts used to record the cosmic rays that flashed inside their eyeballs during their journeys to the moon and back. Credit: NASA

With the 45th anniversary of the Apollo 11 moon landing approaching this weekend, let’s look back at a peculiar discovery made while astronauts Buzz Aldrin and Neil Armstrong left the safety of Earth for the lunar unknown.

Earth’s atmosphere and magnetic field protects us from cosmic rays, which are high-speed protons and other atomic nuclei that shoot across the galaxy like so many submicroscopic billiard balls. They pack a punch. The most powerful contain the same energy as a baseball traveling at 56 mph. Scientists believe cosmic rays originate from exploding supernovae.

En route to the moon in 1969 Buzz Aldrin reported seeing flashes in his eyes in the darkened cabin of the command module. Neil Armstrong noticed them too. Back in 1952, physicist Cornelius Tobias predicted that cosmic rays could interact with light-sensing cells in astronauts’ eyeballs to generate the perception of flashing lights.

Flash patterns observed by Apollo astronauts.

After Aldrin and Armstrong reported their experience, NASA asked future astronauts to be on the lookout for the same and report anything unusual. Later missions even included a special device called the ALFMED (Apollo Light Flash Moving Emulsion Detector), a helmet the astronaut wore to dark-adapt the eyes to better see the flashes. It also held film that recorded cosmic ray hits that were later correlated with the times flashes were seen.

The device conclusively proved that the flashes, dashed lines and occasional glowing puffs the space travelers reported were clearly caused by cosmic rays.

While not every Apollo astronaut saw them, most did and described them as white or colorless spots, stripes, streaks, explosions and multiple tracks. They occurred on average once every 2.9 minutes. For some, the flashes were so frequent it made getting to sleep a challenge.

A cosmic ray hit on the sensor in a camera appears as a segmented line. Credit: NASA/Don Petit

You don’t have to go all the way to the moon to experience this ocular light show. Free from the protection of the atmosphere, International Space Station (ISS) astronaut Don Petit saw them from Earth orbit, describing the flashes poetically as ‘fairies’:

“In space I see things that are not there. Flashes in my eyes, like luminous dancing fairies, give a subtle display of light that is easy to overlook when I’m consumed by normal tasks. But in the dark confines of my sleep station, with the droopy eyelids of pending sleep, I see the flashing fairies.”

It’s thought that as a cosmic ray passes through the retina it causes rod and cone cells to fire, creating the perception of light. According to Petit, a straight-on ray looks like a fuzzy dot, a ray at an angle, a segmented line. Some tracks even have branches like lightning that resemble sparks. Cosmic rays contribute most of the radiation received by astronauts on board the ISS. To date, no one has reached the dosage limit and had to return to a desk job on Earth.

You might think the hull of the space station would keep away cosmic rays, but they’re so tiny and so energetic they pass right through. They can affect electronics too, locking up computers and destroying pixel elements on a camera’s sensor. Petit says you can reboot the computers, but the effect on the sensors is cumulative. Over time, pictures become dotted with pixelly white ‘snow’. Time for a new CCD.

Artistic impression of cosmic rays entering Earth’s atmosphere. Primary rays strike the upper air and create rich showers of less energetic particles. Credit: Asimmetrie/Infn

Studies of cosmic rays on the eyes and bodies of astronauts continues right up through the present with the Alteino-Sileye3 detector used to monitor the radiation environment and light flash phenomenon in the space station.

Cosmic ray flashes remind me of the unexpected benefits of taking a trip to a far-away place. No one considered the possibility (except theoretically), yet by going, we not only discovered a new phenomenon but opened up a lively field of study.