Batty Aurora

Foraging bats during aurora

This morning's geomagnetic storm was just a dull green arc until about 2 a.m., then colors and shimmering ramped up for about an hour. Meanwhile, I was entranced by the sound of wing beats from 10-20 bats foraging over the water close to me. These images are a combination of several frames of long exposures for the aurora with a flash pop for the bats at the beginning of each exposure. A calm night at Island Lake in northwestern Montana.

Fiery Dust From a Famous Snowball

Orionid meteor and northern lights this morning over the Livingston Mountain Range, in Glacier National Park

Orionid meteor flying through its namesake constellation

Every time I climb in the truck and circle into town, I leave a few miles of gravely dust between home and the highway pavement.

Comets sorta' do the same thing.

Every time Halley's Comet makes its 76-year loop around the Sun, it leaves a trail of dust along the inner part of its elliptical orbit. As the comet reaches our inner solar system, the Sun heats and degrades this big, dirty snowball, causing it to drop debris along its path.

And every time the Earth makes its annual lap around the Sun, it flies through this narrow trail of comet dust in late October. Right now in fact. Some of the dust burns up in our atmosphere, causing the "falling stars" that we call the Orionid meteor shower. It should be called the "Halley's meteor shower," but it's called Orionid instead because most of these meteors appear to originate from the vicinity of the constellation Orion. These mostly-tiny particles hit the upper atmosphere about 60 miles above ground and burn up at a blazing 418 miles per hour.

One calculation I found estimates that Halley's Comet might loose an astonishing 6,283,174,472 tons each time it loops around the Sun. At this rate, with a 76-year orbit, Halley's Comet would make 95 laps over 7,220 years before completely disintegrating.

Halley's Comet last passed through the neighborhood in 1986 and won't return until July of 2061. But the comet's dusty trail is also the source of falling stars during the Eta Aquariids meteor shower, which takes place every May. Twice a year, Halley serves up two heavenly reminders of how amazing our little solar system really is - when we stop to look.

Great infographic on how comets and meteor showers are connected
A 500-pound meteorite from Halley's Comet fell on Texas in 1910

Or, another possible source for that beautiful shooting star you saw

Northwestern Lights

Northern lights over Kintla Lake, in Glacier National Park

A pair of coronal mass ejections (CME) from the sun earlier this week set off three nights of weak to moderate northern lights that were visible from most northern states, including Montana. The first CME burst forth on August 22nd and 23rd, reaching Earth on the 26th and 27th. The second CME sent a glancing blow across our night skies on the 29th, but clouds interfered with that one. The clearest skies occurred on the first night, when a small group of campers gathered on the shores of Kintla Lake to enjoy the late-night lights.

Ladies and Gentlemen, You Are Now Free to Unbuckle Your Seatbelts and Move About the Planet

Northern lights this morning over Lake McDonald, in Glacier National Park

While most of us slept through the wee hours this morning, a silent storm sparkled and raged across the night sky. Not like the sky above your home, more like the atmosphere above your home planet. But the only visible signs of this 15-hour storm were the waves of northern lights that washed across most of the northern hemisphere for just a few hours.

Night owls enjoyed the silent aurora borealis as far south as Colorado, including here in cloudy Montana. I made it to Lake McDonald about 30 minutes past midnight, just in time to enjoy the last half hour of northern lights before low fog and high clouds smothered the colors. Most of what I saw were green shimmering waves, but higher up there were also a few magenta lights that made a brief appearance just as the clouds moved in.

Typically, northern lights are set off when a sunspot - a humongous belch of the sun's plasma - occurs on the side of the sun that's facing Earth (the sun also rotates). The electromagnetic storm reaches Earth a couple of days later. This year is supposed to see a peak of sunspot activity, which runs in 11-year cycles. (There are several northern lights forecast links over in the right hand column.)

But last night's solar storm was not typical. Instead of a sunspot, the electrical storm that swept across our little planet was was caused by an unexpected, interplanetary shock wave. Last night's turbulence was thought to originate from ripples in the solar winds.

We fly through the solar winds every day, here on the third rock from the sun. As the sun makes one complete rotation every 27 Earth-days, it flings highly-charged electrons and protons off into space. This solar wind blows continuously, filling our solar system and then some. It's been compared to a flowing skirt around a spinning dancer. The ripples are caused by winds of different speeds spinning away from the sun.

The so-called slow solar winds leave the sun at only 248 miles per second, while the fast winds leave at 466 miles per second. Where fast and slow rub together, turbulence occurs. Today we flew through one of these invisible pockets of solar turbulence. And as we fly around our solar system, the Earth also sweeps up an estimated 40,000 tons of interplanetary dust every year.

By the way, all this flinging of electrons and protons means that our star, the Sun, is loosing mass at the rate of roughly 4.4 to 6.6 billion tons every hour. But relax. It's only lost about 0.01% of its mass to the solar winds, so don't let the thought keep you up at night - unless they are predicting northern lights.