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GEOMAGNETIC STORM: A CME hit Earth's magnetic field on May 18th at around 0100 UT. Although it was just a glancing blow, the impact was enough to spark a G1-class geomagnetic storm. In the United States, Northern Lights descended as far south as Pawnee Buttes, Colorado:
"The aurora was not visible to the naked eye," says photographer Robert Arn. "Only with a 30 second exposure did I know it was there. As I started to collect data, I noticed an electrical storm in the distance. The juxtaposition of the electrical storm and aurora made for a spectacular image. (The moon near the horizon illuminated the landscape.)"
Elsewhere in the United States, faint auroras were sighted or photographed in, e.g., Washington, Vermont, and Iowa. Browse the aurora gallery for more...
Realtime Aurora Photo Gallery
ANOTHER INCOMING CME: As Earth's magnetic field reverberates from one CME strike, a second more potent CME is on the way. It was propelled in our direction by sunspot AR1748, which unleashed an M3-class solar flare on May 17th (0858 UT). Although this is not the strongest flare we've seen from AR1748, it could be the most geoeffective; the sunspot was almost-squarely facing Earth when the blast occurred. NOAA forecasters estimate a 75% chance of polar geomagnetic storms when the cloud arrives. Aurora alerts: text, voice.
The Solar and Heliospheric Observatory took this picture of the CME leaving the sun at 1500 km/s (3.4 million mph) on May 17th:
In the video, the CME appears to hit Mercury, but it does not. It is merely passing in front of the innermost planet. The planet in the line of fire is actually Earth.
Realtime Space Weather Photo Gallery
DISCONNECTION EVENT IN THE TAIL OF COMET LEMMON: Comet Lemmon (C/2012 F6), which is receding from the sun not far beyond the orbit of Earth, has just experienced a "disconnection event." A cloud of dusty plasma is propagating down the comet's tail, shown here in a photo taken by Paul Mortfield on May 15th:
"I was pretty surprised to see this disconnection event when I processed the images," says Mortfield. "The comet is a challenge to photograph because it is so low in the sky at the start of morning twilight."
Disconnection events can be caused by CME impacts. A famous example is that of Comet Encke in 2007. Comet Lemmon, however, is not on the same side of the sun as active sunspot AR1748. It's hard to see how the recent X-flares can be responsible. Nevertheless, solar activity is high, so now is a good time to monitor comet tails. They are very sensitive to stormy space weather.
Comet Lemmon is a pre-dawn object for observers in the northern hemisphere. It is currently gliding alongside the Great Square of Pegasus in the eastern sky before sunrise. The 7th-magnitude comet is too faint to see with the naked eye, but it is visible in medium-to-large backyard telescopes. Observers with computerized GOTO 'scopes should point their optics here.
More about Comet Lemmon: 3D orbit, ephemeris, light curves.
Realtime Comet Photo Gallery
Realtime Aurora Photo Gallery
Realtime Noctilucent Cloud Photo Gallery
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