A Giant Palm Tree Sprite in Texas

June 21, 2019: Last night in Texas, a flurry of red sprites exploded from the top of a powerful thunderstorm. One of the the red forms was so tall and bright, people saw it 200 miles away in Oklahoma. “My boys and I saw it with our unaided eyes,” reports Paul Smith, who photographed the event from the shores of Lake Thunderbird, OK. This may be the first time that a sprite’s reflection has been captured in water:

Naked-eye sightings of sprites are rare, mainly because they are so fleeting. But this one left an impression. “My eleven-year-old son Thomas described it as a ‘huge orange-y-brown flash of lines high in the sky,'” says Smith. “My seven-year-old James just exclaimed ‘what the heck was that?'”

At first glance, Smith’s capture resembles a Gigantic Jet–that is, a type of “sprite on steroids.” But lightning expert Oscar van der Velde of the Universitat Politècnica de Catalunya thinks it may be something else:

“In early days of sprite research, they were called ‘palm trees’ by researchers from the University of Alaska,” van der Velde explains. “It is, basically, a bushy group of red sprites on top, with a secondary purple discharge hanging below. These types of events are quite rare. You need a big, active mesoscale convective system to produce them.”

Palm tree sprites are a topic of cutting edge research. “We haven’t even been able to confirm that they indeed originate from the thundercloud,” says van der Velde.

“Last night was so much fun,” adds Smith. “In addition to the sprites, my son Thomas photographed Jupiter and our Moon with the Nikon coolpix 80x zoom camera. We also saw a nice bolide exploding over the storms. The kid’s reactions were priceless.”

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Mysterious Moisture in the Mesosphere

June 19, 2019: The 2019 season for noctilucent clouds (NLCs) has been remarkable, maybe the best ever, with NLCs appearing as far south as Los Angeles CA and Albuquerque NM. What’s going on? Researchers aren’t sure, but Lynn Harvey of the University of Colorado’s Laboratory for Atmospheric and Space Physics has just found an important clue.

“The mesosphere is quite wet,” she says. “Water vapor concentrations are at their highest levels for the past 12 years.”

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Noctilucent clouds over Piwnice, Poland, on June 18th. Credit: Piotr Majewski

Noctilucent clouds form when summertime wisps of water vapor rise to the top of the atmosphere. Water molecules stick to specks of meteor smoke, gathering into icy clouds that glow electric blue when they are hit by high altitude sunlight.

When noctilucent clouds began appearing at unusually low latitudes in early June, Harvey took a look at data from NASA’s Microwave Limb Sounder–a satellite-based sensor that can measure water in the upper atmosphere. Her results are shown in the animated plot below.

“The red line is 2019, while other colors trace previous years,” explains Harvey. “The plot cycles from low to high latitudes,” showing a wave of moisture in the mesosphere.

It’s a veritable tidal wave. Water vapor concentrations at lower latitudes (35 to 45 N) have nearly doubled their normal values, providing a surplus of H2O molecules for noctilucent clouds. Researchers aren’t sure where the water is coming from, though.

Planetary wave activity could be transporting cold air and high water vapor to the ‘noctilucent zone,'” speculates James Russell of Hampton University’s Center for Atmospheric Sciences. “We’ve seen this happen before during mid-latitude outbreaks of noctilucent clouds.”

The solar cycle may be helping, too. Right now a deep Solar Minimum is underway. Ultraviolet radiation that would normally destroy water in the mesosphere is at low ebb.

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Noctilucent clouds over Riga, Latvia,on June 18th. Credit: Ivo Dinsbergs

The wave appears to be breaking. “As we enter the 3rd week of June, the water has stopped increasing,” notes Harvey. “Poleward of 70N the water content has been dropping for a few weeks, and right around the north pole it’s getting quite dry. At mid-latitudes (35-65N), water content is still high, but it’s leveling off.”

No one knows what will happen next. Another wave could bring renewed sightings of NLCs at low latitudes. Or conditions could return to normal, restoring the clouds to their usual habitat near the Arctic Circle.  Says Russell, “this all points to mysteries of the atmosphere that have not been solved.” Stay tuned!

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Low Latitude Noctilucent Clouds

June 15, 2019: If you’ve never seen a cloud of frosted meteor smoke, now is the time to look. 2019 is shaping up to be the best year for noctilucent clouds (NLCs) … maybe ever. Normally confined to near-Arctic latitudes, NLCs have been seen this month in most US states. On Friday morning, June 14th, Don Davis saw them, astonishingly, from the city of Joshua Tree not far from Los Angeles CA:

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“They were dim but distinct,” says Davis. “I photographed them easily using a 4 second exposure at ISO 400.”

Davis’s sighting at +34.1 degrees sets the record for low-latitude observations of NLCs, breaking the previous record set only five days earlier by Brian Guyer at the National Weather Service in Albuquerque, New Mexico (+35.1 degrees).

“I’m shocked to report that I saw the noctilucent clouds while venturing outdoors for a weather observation shortly after sunset,” says Guyer, who is a senior meteorologist. “When I noticed the faint blue wavy tendrils far off to the north, I asked myself, ‘am I really seeing noctilucent clouds from here?’ I’m happy to see that other folks are also seeing these beautiful spectacles of nature at lower latitudes.”

Noctilucent clouds form every year when wisps of summertime water vapor rise to the top of Earth’s atmosphere and crystallize around specks of meteor smoke. The season typically starts in late May, peaks in July, and peters out in August. If NLCs are being seen in California and New Mexico in June, the season’s peak in early July could be very special indeed.

Noctilucent clouds have been creeping south for years–a possible result of climate change and/or the solar cycle. 2019 has broken all the old records for southern sightings, bringing the clouds into the mainstream of mid- to low-latitude sky watching. Now everyone should be alert for NLCs.

Observing tips: Look west 30 to 60 minutes after sunset (or before sunrise) when the sun is just below the horizon. If you see luminous blue-white tendrils spreading across the sky, you may have spotted a noctilucent cloud.

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Halobacteria Change Color When They Touch Space

June 13, 2019: Picture this: An astronaut climbs aboard his spacecraft and blasts off from Earth. At the apex of the flight, he experiences something strange. Weightlessness? Space sickness? No. He changes color! This doesn’t happen to human astronauts, but it does happen to halobacteria, an extreme-loving microbe from Earth that might be able to live on Mars.

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In recent weeks, Spaceweather.com and the students of Earth to Sky Calculus have been flying halobacteria to the stratosphere. Why? To see if the salt-loving microbes might be able to survive on the Red Planet. The stratosphere is a good place to find out because conditions in Earth’s stratosphere are remarkably similar to conditions on the surface of Mars.

The quick answer is YES. Halobacteria do survive–for brief trips, at least. Halobacteria that we launch into the stratosphere come back alive a few hours later, and we can easily culture them in an incubator.

But they don’t come back unchanged. We find that halobacteria color-shift during their trip to the edge of space. On Earth, they’re pink. When they reach the stratosphere, they turn yellow–and they remain yellow even after they return to the ground. Just by looking at the color of a sample, we can tell if it has been to the stratosphere.

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The many colors of halobacteria. The yellow varieties have all flown to the stratosphere. The pinkest forms are descendents of the yellows.

Back in the lab, something even more interesting happens. When we culture the “space-traveling” yellow halobacteria, allowing them to feed and multiply, their descendants turn pink again! The descendants undo the effects of the balloon flight, resetting themselves for another trip.

What’s happening? The answer involves bacteriorhodopsin.

Bacteriorhodopsin is a protein used by halobacteria to help feed themselves When food sources become scarce, halobacteria photosynthesize sunlight for energy. Unlike plants, however, they don’t use green chlorophyll. Halobacteria use purple bacteriorhodopsin.

0_yellowpinkBacteriorhodopsin has two stable forms–a purple form and a yellow form, each with a different shape. During photosynthesis, bacteriorhodopsin toggles back and forth between these forms, blinking yellow and purple. Because of this color-shifting ability, technologists have long been interested in using bacteriorhodopsin as a kind of “electronic ink” in tablets and smart phones.

When we launch halobacteria to the stratosphere, the microbes turn yellow–and stay yellow. They stop cycling back to their purple state as they would normally do during photosynthesis. Perhaps UV rays in the stratosphere denature the bacteriorhodopsin proteins. Denaturing means they lose their shape, permanently changing their color.

Whatever causes the color change, the descendants of flown halobacteria put their proteins back together again–ready for more trips to space.

We’re preparing to fly a batch of the descendants to see if they are even tougher than their predecessors. Stay tuned

 

Record-Setting Noctilucent Clouds

June 11, 2019: On June 8th and 9th, many people who have never previously heard of “noctilucent clouds” (NLCs) found themselves eagerly taking pictures of them–from moving cars, through city lights, using cell phones and iPads. “I have never seen clouds like this before!” says Tucker Shannon, who took this picture from Corvallis, Oregon:

“I heard that they may have been seeded by meteoroids,” says Shannon.

That’s correct. NLCs are Earth’s highest clouds. Seeded by meteoroids, they float at the edge of space more than 80 km above the planet’s surface. The clouds are very cold and filled with tiny ice crystals. When sunbeams hit those crystals, they glow electric-blue.

Noctilucent clouds used to be a polar phenomenon. In recent years, however, researchers have noticed their electric-blue forms creeping south. Is it climate change? Or the solar cycle? No one knows for sure.

This past weekend, even veteran observers were stunned by the clouds’ intensity and southern reach. At one point, they were visible in Freedom, Oklahoma (latitude +36.7 N). As far as we know, that is the lowest latitude sighting ever. Other notable low-latitude sightings include San Francisco, California, and the Cedar Breaks National Monument in Utah.

Still images of NLCs capture only a fraction of their magic. These small videos recorded by Keven Lapp outside Edmonton, Alberta, show their hypnotic fine-structured rippling motions:

“This was one of the largest NLCs that I’ve ever seen,” says Lapp. “The time lapse was taken between 2:40 AM and 3:24 AM local time.”

At present, no one can predict exactly when these noctilucent clouds will re-appear. Recent events suggest that even mid-latitude observers should be alert. Observing tips: Look west 30 to 60 minutes after sunset when the sun has dipped below the horizon. If you see luminous blue-white tendrils spreading across the sky, you may have spotted a noctilucent cloud.

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June is the Best Month for Daytime Meteor Showers

June 5, 2019: On June 30, 1908, in broad daylight, a meteoroid hurtled out of the blue sky over Russia’s Tunguska river and exploded, leveling a forest. The event, which researchers are still studying today, kickstarting a new field of astronomy: Daytime meteor showers1.

Most people don’t know it, but some of the strongest meteor showers of the year happen when the sun is up. In fact, one of them is underway now. Today’s sky map from Canada’s Meteor Orbit Radar (CMOR) in western Ontario shows a hot spot in the constellation Aries only 20 degrees from the sun.

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Yes, this picture is real. It shows a daylight fireball over the Tetons behind Jackson Lake, Wyoming, in the summer of 1972.  Credit & Copyright: James M. Baker

“These are Arietid meteors, and they peak every year in early June as Earth passes through a debris stream linked to the unusual comet 96P/Machholz,” says professor Peter Brown of the University of Western Ontario. “At their peak on June 7th, we expect our radar to detect one Arietid every 20 seconds. This makes them the 5th strongest radar shower of the year.”

In fact, people can see daylight meteors–a few at least. The trick is to look just before dawn when the shower’s radiant is barely above the horizon and the sun is barely below.

“The Arietids an observer would see before dawn are quite impressive as they are all Earthgrazers, skimming the atmosphere almost horizontally overhead,” notes Brown. “Earthgrazers tend to be slow and very bright.”

arietid_skymap

It turns out that June is the best month of the year for daytime meteor showers. When the Arietids subside, another daytime shower will take over: The zeta Perseids peak on June 13th. And then another: The beta Taurids on June 29th.

The beta Taurids are particularly interesting because researchers suspect it may be responsible for the Tunguska explosion of 1908. This June the Taurid debris swarm will make its closest approach to Earth since 1975. Many astronomers, including Brown, will use large telescopes to search for signs of hazardous objects as the swarm passes by.

Stay tuned for updates.

End note: (1) Tunguska was a dramatic example of a daytime meteor. It took 30+ years after the explosion, however, for the field of daytime meteor studies to gain its footing. Brown explains: “The first daytime showers were observed and recognized by  astronomers at Jodrell Bank shortly after World War II, really kickstarting the field. As early as 1940, studies of the orbit of the nighttime Taurids suggested the stream should intersect the Earth during the day in June. At that time, predictions were made by Fred Whipple of a daytime component to the Taurid stream in June (the Beta Taurids/Zeta Perseids). In the 1970s, the peak date for the Beta Taurids (about June 30) and the radiant location were matched by Lubor Kresak to the Tunguska fireball–at which time he posited a link between the Beta Taurids and Tunguska.”

Huge Blue Cloud Circles the North Pole

May 31, 2019: A huge blue cloud of frosted meteor smoke is pinwheeling around the Arctic Circle. NASA’s AIM spacecraft spotted its formation on May 20th, and it has since circled the North Pole one and a half times, expanding in size more than 200-fold.

“These are noctilucent clouds,” says Cora Randall of the AIM science team at the University of Colorado. “And they are going strong.”

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Noctilucent clouds (NLCs) in May are nothing unusual. They form every year around this time when the first wisps of summertime water vapor rise to the top of Earth’s atmosphere. Molecules of H2O adhere to specks of meteor smoke, forming ice crystals 80 km above Earth’s surface. When sunbeams hit those crystals, they glow electric-blue.

But these NLCs are different. They’re unusually strong and congregated in a coherent spinning mass, instead of spreading as usual all across the polar cap.

“This is most likely a sign of planetary wave activity,” says Randall.

Planetary waves are enormous ripples of temperature and pressure that form in Earth’s atmosphere in response to Coriolis forces. They are responsible in part for undulations in the jet stream and can have a major influence on global weather. All rotating planets with atmospheres have these kind of waves.

Data from NASA’s Microwave Limb Sounder (MLS)  instruments show that, indeed, a planetary wave is circling the North Pole:

mls_bigstrip

“The region of coldest temperatures migrates clockwise around the hemisphere, making one complete lap in about 5 days,” notes Lynn Harvey of the AIM science team who processed the data. “This is where the NLCs are forming.”

Because of planetary wave activity, the 2019 season is shaping up to be unusually good. The clouds have already made an appearance in the USA–something that usually doesn’t happen until late June or July.

“Last night, I took my dog out an hour and twenty minutes after sunset and was happily surprised to see these noctilucent clouds,” reports Shelley Johnson of Anacortes, Washington, who took this picture  on May 30th:

nlc_strip

NLCs have also been sighted in Europe–highlighted by a bright display in Germany. “This is my earliest observation of noctilucent clouds and, considering the fact that it’s only May, they were exceptionally bright and well structured,” reports Laura Kranich of Kiel, Germany. “Seems like this is going to become a great season!”

If the 2019 NLC season continues to develop this quickly, even mid-latitude observers may soon be seeing this polar phenomenon. Observing tips: Look west 30 to 60 minutes after sunset when the sun has dipped below the horizon. If you see luminous blue-white tendrils spreading across the sky, you may have spotted a noctilucent cloud.

Realtime Noctilucent Cloud Photo Gallery

 

Starlink Satellite Flares (Part 2)

May 29, 2019: SpaceX’s Starlink satellites are flaring, creating flashes of light in the night sky that can rival the brightest stars. Veteran observer Tristan Cools of Bruges, Belgium, reports: “Yesterday evening almost all the objects from the Starlink launch between the leading and trailing satellites were flaring, some very brightly around magnitude 0.”


Flat surfaces on the bottom of the Starlink satellites are reflecting sunlight down to Earth.

Marco Langbroek of the Netherlands, famous for recording the first video of the Starlink train, saw last night’s flares, too.

“The flaring behaviour was interesting,” he says. “There was a series of brief naked eye flares, one after the other. I did not count but I think I saw at least 15 or so do this within a time span of 1 to 2 minutes. The flares were magnitude +1.5 to +2”–that is, only a little dimmer than 1st magnitude stars.

SpaceX launched 60 satellites on May 23rd–the first installment of a Starlink “mega-constellation” that could number 12,000 by the time the project is complete. Starlink aims to surround Earth with satellites and provide broadband internet to every corner of the globe. Astronomers won’t be happy, however, until SpaceX finds a way to dim these flares. A globe-circling swarm of flashing satellites could wreak havoc with the type of deep-sky observations crucial to modern research.

Ready to see the Starlink satellites with your own eyes? Visit Heavens-Above.com and click on “Starlink (leader)” for local flyby predictions. A dynamic display of the satellites’ current location is also available.

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Starlink Satellite Flares (Part 1)

May 28, 2019:  SpaceX has an idea: Surround the Earth with 12,000 satellites and provide broadband internet to every corner of the globe. The project is called Starlink–and it’s getting started. The first 60 Starlink satellites were launched on May 23rd, creating a train of bright lights in the night sky. “It was one of the most spectacular things I have every seen,” reports Marco Langbroek of Leiden, the Netherlands, who made this video the night after the launch:

thetrain_strip

“I could see the entire train of satellites with the unaided eye,” he says.

Since then, sky watchers have been catching the “Starlink Train” — often by accident. “I saw it last night around 9:30 pm in Piseco, New York,” reports Christopher Hayes. “I just happened to look up at the right moment. Thanks to Spaceweather.com I knew what it was, but anyone who didn’t know would have been in for quite a surprise. It was such an amazing sight!”

The Train no longer looks as it did on the first night. Individual satellites are fading in brightness as they move out into their operational orbits. A typical urban sighting now consists of only 4 to 6 naked-eye objects interleaved by dozens of fainter satellites best seen through binoculars.

The Train is still worth catching, however, because the satellites are flaring. Sunlight is glinting off flat surfaces on the satellites’ bodies, creating flashes of light that can briefly rival the brightest stars in the sky. Here are two flares photographed on May 26th by Bill Keel, an astronomy professor at the University of Alabama:

“I saw a pass of the Starlink Train about 15 degrees from zenith over Tuscaloosa,” says Keel. “Some of them showed very systematic flaring, flashing brightly at nearly the same location in the sky. The brightest flares reached a magnitude of -2 for about 5 seconds.” For reference, that’s 50% brighter than Sirius, the brightest star in the sky.

On May 27th, George Varros photographed a cluster of 4 flares over Mt. Airy, Maryland. “I could see them despite horrible conditions–clouds, humidity, airplanes everywhere. This was a real treat visually!”

The flares are pretty, but some astronomers are concerned. Will 12,000 artificial stars criss-crossing the night sky, sometimes flaring, make deep-sky observing impossible? It’s an important question. Keel speculates that the regularity of the flares he observed might mean they’re predictable, in which case, big telescopes could learn to avoid them. We’ll find out soon enough as SpaceX plans to launch at least two more trains this year.

Ready to see the Starlink Train with your own eyes? Visit Heavens-Above.com and click on “Starlink (leader)” for local flyby predictions. A dynamic display of the satellites’ current location is also available.

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Close Encounters with the Taurid Swarm

May 24, 2019: In November 2032, Earth will pass through the Taurid Swarm, a cloud of debris from Comet 2P/Encke that makes brilliant fireballs when its gravelly particles occasionally hit Earth’s atmosphere. Previous encounters with the Swarm in 2005 and 2015 produced showers of bright meteors observed around the world; in 1975 the Swarm contacted the Moon, making Apollo seismic sensors ring with evidence of objects hitting the lunar surface. If forecasters are correct, we’re in for similar activity 13 years from now.

Some researchers are beginning to wonder if there might be more to the Taurid Swarm than the pebble-sized particles that make fireballs–something, say, that could level a forest. On June 30, 1908, a forest in Siberia did fall down when a 100-meter object fell out of the sky and exploded just above the Tunguska River. Back-tracking the trajectory of the impactor suggests it may have come from the Taurid Swarm.

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Above: Trees felled by the Tunguska explosion. Credit: the Leonid Kulik Expedition

Why would the Swarm contain such big rocks? After all, comet debris is normally no bigger than specks of dust. The most popular theory holds that 10 or 20 thousand years ago, a giant 100-km wide comet fragmented in the inner solar system. The breakup produced a mixture of dust and asteroid-sized bodies that are still present today. Comet 2P/Encke itself may be just one of the fragments.

If the Taurid Swarm does indeed contain Tunguska-class impactors, the people of Earth need to know. A team of astronomers from the University of Western Ontario (UWO) suggests that this summer is a great time to find out.

“In June 2019 the Earth will approach within [0.06 AU or 9 million km] of the center of the Taurid swarm, its closest post-perihelion encounter with Earth since 1975,” write UWO astronomers David Clark, Paul Wiegert and Peter Brown in a paper just accepted for publication in the Monthly Notices of the Royal Astronomical Society. “This will be the best viewing geometry to detect and place limits on the number of Near-Earth Objects proposed to reside at the swarm center until the early 2030s.”

To be clear, the team won’t be looking for fireballs disintegrating in Earth’s atmosphere. Instead, they want to point powerful telescopes at the Swarm, peering deep inside it to see if they can find big, dangerous pieces of rock gliding among the pebbles.

“Seeing anything in the Taurid Swarm will be tough,” says Wiegert. “It’s faint, it’s spread across a lot of sky, and it’s moving fast. A fair dash of serendipity will be needed to catch a glimpse of it. But we have to try to strike when the iron is hot, and that’s now.”

“We’ve applied for 10 hours of time on the Canada-France-Hawaii Telescope atop Mauna Kea,” he adds. “And we’re hoping other big telescopes will join the search as well.”

To learn more about this year’s close encounter with the Taurid Swarm, read the original research at https://arxiv.org/pdf/1905.01260.pdf