Look! Fast! Sprite lightning occurs only at high altitudes above thunderstorms, only last for a thousandth of a second and emit light in the red portion of the visible spectrum, so they are really difficult to see. But one of our favorite astrophotographers and timelapse artists, Randy Halverson captured sprites during a recent thunderstorm in South Dakota. But wait, there’s more!
In his timelapse video, above, you’ll also see some faint aurora as well as green airglow being rippled by gravity waves.
Or perhaps I should say “eine grosse Aurora!” ESA astronaut Alexander Gerst made this time-lapse of a “massive aurora” as seen from the Space Station on August 24. The entire video is beautiful, showing not just a view of the ghostly green aurora but also plenty of stars, airglow, the graceful rotation of the ISS’ solar arrays, and finally the blooming light of dawn – one of sixteen the crew of the Station get to witness every day.
Then again, I’m now wondering: what is the mass of an aurora? Hmm…
“Bangkok is the bright city. The green lights outside the city? No idea…” This was the description accompanying the photo above, perplexingly Tweeted by Expedition 40/41 astronaut Reid Wiseman on Aug. 18, 2014. And while we’ve all seen fascinating photos of our planet shared by ISS crew members over the years this one is quite interesting, to say the least. Yes, there’s the bright illumination of Bangkok’s city lights, along with some stars, moonlit cloud cover extending northeast and the fine line of airglow over the horizon, but what are those acid-green blotches scattered throughout the darkness of the Gulf of Thailand? Bioluminescent algal blooms? Secret gamma-ray test labs? Underwater alien bases?
The answer, it turns out, actually is quite fishy.
The offshore illumination comes from fishing boats, which use enormous arrays of bright green LED lights to attract squid and plankton to the surface.
According to an an Oct. 2013 article on NASA’s Earth Observatory site by Michael Carlowicz, “…fishermen from South America and Southeastern Asia light up the ocean with powerful lamps that attract the plankton and fish species that the squid feed on. The squid follow their prey toward the surface, where they are easier for fishermen to catch with jigging lines. Squid boats can carry more than a hundred of these lamps, generating as much as 300 kilowatts of light per boat.”
Seen from orbit, the lights from squid fishing fleets rival the glow of the big cities! What might this look like from sea level? According to photos shared by one travel blogger in 2013, this.
Watch a video time-lapse from an ISS pass over the same region on Jan. 30, 2014.
Emerald green, fainter than the zodiacal light and visible on dark nights everywhere on Earth, airglow pervades the night sky from equator to pole. Airglow turns up in our time exposure photographs of the night sky as ghostly ripples of aurora-like light about 10-15 degrees above the horizon. Its similarity to the aurora is no coincidence. Both form at around the same altitude of 60-65 miles (100 km) and involve excitation of atoms and molecules, in particular oxygen. But different mechanisms tease them to glow.
Auroras get their spark from high-speed electrons and protons in the solar wind that bombard oxygen and nitrogen atoms and molecules. As excited electrons within those atoms return to their rest states, they emit photons of green and red light that create shimmering, colorful curtains of northern lights.
Airglow’s subtle radiance arises from excitation of a different kind. Ultraviolet light from the daytime sun ionizes or knocks electrons off of oxygen and nitrogen atoms and molecules; at night the electrons recombine with their host atoms, releasing energy as light of different colors including green, red, yellow and blue. The brightest emission, the one responsible for creating the green streaks and bands visible from the ground and orbit, stems from excited oxygen atoms beaming light at 557.7 nanometers, smack in the middle of the yellow-green parcel of spectrum where our eyes are most sensitive.
That’s not saying airglow is easy to see! For years I suspected streaks of what I thought were high clouds from my dark sky observing site even when maps and forecasts indicated pristine skies. Photography finally taught me to trust my eyes. I started noticing green streaks near the horizon in long-exposure astrophotos. At first I brushed it off as camera noise. Then I noticed how the ghostly stuff would slowly shape-shift over minutes and hours and from night to night. Gravity waves created by jet stream shear, wind flowing over mountain ranges and even thunderstorms in the lower atmosphere propagate up to the thermosphere to fashion airglow’s ever-changing contours.
Last month, on a particularly dark night, I made a dedicated sweep of the sky after my eyes had fully adapted to the darkness. A large swath of airglow spread south of the Big and Little Dipper. To the east, Pegasus and Andromeda harbored hazy spots of varying intensity, while brilliant Mars beamed through a long smear in Virgo.
To prove what I saw was real, I made the photos you see in this article and found they exactly matched my visual sightings. Except for color. Airglow is typically too faint to fire up the cone cells in our retinas responsible for color vision. The vague streaks and patches were best seen by moving your head around to pick out the contrast between them and the darker, airglow-free sky. No matter what part of the sky I looked, airglow poked its tenuous head. Indeed, if you were to travel anywhere on Earth, airglow would be your constant companion on dark nights, unlike the aurora which keeps to the polar regions. Warning – once you start seeing it, you
Airglow comes in different colors – let’s take a closer look at what causes them:
* Red – I’ve never seen it, but long-exposure photos often reveal red/pink mingled with the more common green. Excited oxygen atoms much higher up at 90-185 miles (150-300 km) radiating light at a different energy state are responsible. Excited -OH (hydroxyl) radicals give off deep red light in a process called chemoluminescencewhen they react with oxygen and nitrogen. Another chemoluminescent reaction takes place when oxygen and nitrogen molecules are busted apart by ultraviolet light high in the atmosphere and recombine to form nitric oxide (NO).
* Yellow – From sodium atoms around 57 miles (92 km) high. Sodium arrives from the breakup and vaporization of minerals in meteoroids as they burn up in the atmosphere as meteors.
* Blue – Weak emission from excited oxygen molecules approximately 59 miles (95 km) high.
Airglow varies time of day and night and season, reaching peak brightness about 10 degrees, where our line of sight passes through more air compared to the zenith where the light reaches minimum brightness. Since airglow is brightest around the time of solar maximum (about now), now is an ideal time to watch for it. Even cosmic rays striking molecules in the upper atmosphere make a contribution.
See lots of airglow and aurora from orbit in this video made using images taken from the space station.
If you removed the stars, the band of the Milky Way and the zodiacal light, airglow would still provide enough illumination to see your hand in front of your face at night. Through recombination and chemoluminescence, atoms and molecules creates an astounding array of colored light phenomena. We can’t escape the sun even on the darkest of nights.
It’s actually remarkably beautiful, and well worth two minutes of your time.*
Assembled from actual photographs taken by astronauts aboard the Space Station, many of them by Don Pettit during Expedition 31 (Don took a lot of photos) this timelapse “The World Outside My Window” by David Peterson ramps up the artistic value by featuring super-duper high definition, smoothed frame transitions and a musical score by “Two Steps From Hell.” (Don’t worry, that sounds scarier than it is.) Even if you’ve seen some of these clips before, they’re worth another go.
After all, there’s no good reason not to be reminded of how beautiful our planet is from space. Enjoy!
*It’s actually two minutes and twenty-eight seconds but I don’t think you’ll mind.
Italian astronaut Luca Parmitano shares a lot of fantastic photos taken from his privileged position 260 miles up aboard the Space Station, orbiting the planet 16 times a day. This is his latest, a stunning view of nighttime city lights spread out beneath a glowing dome of ghostly airglow and shimmering aurorae, with a backdrop of brightly shining stars. The dark silhouette of a solar array is in the foreground at right.
And in case you were wondering, yes, astronauts certainly can see stars while in space. A lot of them, in fact. (Except up there, they don’t twinkle… but they’re no less beautiful!)
“Every time we look into the sky and we admire the same stars, we share the same experience with all those who still know how to dream.”
– Luca Parmitano
Luca Parmitano is the first of ESA’s new generation of astronauts to fly into space. The current mission, Volare, is ESA’s fifth long-duration Space Station mission. During his six-month-long stay aboard the ISS, Luca has been conducting research for ESA and international partners as well as taken many photographs of our planet, sharing them on Twitter, Flickr, and the Volare mission blog.
Look closely at this beautiful serene view taken by Miguel Claro from Portugal. Not only is it a stunning view of the skies over Lake Alqueva in the Dark Sky Alqueva Reserve in Portugal, but there are also several scientifically interesting features here. Of course, visible is the arc of the Milky Way, filled with colors and light. Seen here is the most central region of the Milky Way, located near the constellations of Scorpio and Sagittarius, where you might recognize many deep sky objects like the Lagoon Nebula (M8) and the Trifid Nebula (M20).
The “glow” seen here is not the aurora borealis, but instead it is airglow (atmospheric chemiluminescence), which is a photochemical reaction that occurs high in the atmosphere when various atoms get excited from the ultraviolet radiation from the Sun. Miguel explained via email that the yellow light is from emissions from sodium atoms in a layer at 92 km, and above it, is green light from oxygen atoms in a layer 90-100 km high. This emission layer is clearly visible from earth orbit, which we’ve seen in many images and videos taken from the ISS.
“Reflected in the peaceful lake and due to the polarization effect of water, we could clearly see the entire constellation of Scorpius with the real color of each star naturally saturated,” Miguel said via email, “due to this polarization and blurred effect, caused by the slowly movement of water during the long exposure. The orange color of the Red Supergiant Antares could be easily distinguished from the blue color of the Subgiant star, Shaula, in the end of tail.”
Miguel used a Canon 60Da – ISO 1600; 35mm lens at f/2; Exp. 15 secs. Mosaic of 23 images, taken on June 15, at 02:35 AM.
If you couldn’t tell, we love time-lapse videos… whether they’re made of photos looking up at the sky from Earth or looking down at Earth from the sky! This latest assembly by photographer Bruce W. Berry takes us on a tour around the planet from orbit, created from images taken by astronauts aboard the International Space Station and expertly de-noised, stabilized and smoothed to 24 frames per second. The result is — like several others before — simply stunning, a wonderful reminder of our place in space and the beauty of our living world.
A pair of images from NASA’s Cassini spacecraft show Titan glowing in the dark.
Titan never ceases to amaze. Saturn’s largest moon, it’s wrapped in a complex, multi-layered nitrogen-and-methane atmosphere ten times thicker than Earth’s. It has seasons and weather, as evidenced by the occasional formation of large bright clouds and, more recently, an area of open-cell convection forming over its south pole. Titan even boasts the distinction of being the only other world in the Solar System besides Earth with large amounts of liquid existing on its surface, although there in the form of exotic methane lakes and streams.
We have NASA’s Cassini spacecraft to thank for these discoveries, and now there’s one more for the ceaseless explorer to add to its list: Titan glows in the dark.
Seen above in two versions of the same calibrated raw image, acquired by Cassini on May 7, 2009, Titan hovers in front of a background field of stars which appear as blurred streaks due to the 560 seconds (about 9 1/2 minutes) exposure time and the relative motion of the spacecraft.
The image on the left shows Titan in visible light, receiving reflected sunlight off Saturn itself — “Saturnshine” — while the moon was on the ringed planet’s night side. The image on the right was processed to exclude this reflected light… and yet it still shines. (E pur si candeo?)
The hazy moon’s dim glow — measuring only around a millionth of a watt — comes from not only the top of its atmosphere (which was expected) but also from much deeper within, at altitudes of 300 km (190 miles).
The glow is created by chemical reactions within Titan’s atmosphere, sparked by interactions with charged particles from the Sun and Saturn’s magnetic field.
“It turns out that Titan glows in the dark – though very dimly,” said Robert West, the lead author of a recent study in the journal Geophysical Research Letters and a Cassini imaging team scientist at NASA’s Jet Propulsion Laboratory. “It’s a little like a neon sign, where electrons generated by electrical power bang into neon atoms and cause them to glow. Here we’re looking at light emitted when charged particles bang into nitrogen molecules in Titan’s atmosphere.”
The light is analogous to the airglow seen in Earth’s atmosphere, often photographed by astronauts aboard the ISS.
Still, even taking known sources of external radiation into account, Titan is glowing from within with an as-yet-unexplained light. More energetic cosmic rays may be to blame, penetrating deeper into the moon’s atmosphere, or there could be unexpected chemical reactions or phenomena at work — a little Titanic lightning, perhaps?
“This is exciting because we’ve never seen this at Titan before,” West said. “It tells us that we don’t know all there is to know about Titan and makes it even more mysterious.”
Tracing a bright star upon the Earth, the lights of Russia’s capital city blaze beyond the solar panels of the International Space Station in this photo, captured by the Expedition 30 crew on the night of March 28, 2012.
As an electric-blue dawn flares around Earth’s northeastern limb, the green and purple fire of the Aurora Borealis shimmers and stretches away to the northwest above a pale yellow line of airglow.
Traveling at 17,500 miles an hour (28,163 km/hr), the ISS was approximately 240 miles (386 km) above the Russian city of Volgograd (formerly Stalingrad) when this photo was taken.