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CME IMPACT, GEOMAGNETIC STORM: An interplanetary shock wave, possibly the leading edge of a CME, hit Earth's magnetic field on October 8th at approximately 2015 UT (1:15 pm PDT). The impact has sparked a minor (G1-class) geomagnetic storm that could intensify in the hours ahead. High-latitude sky watchers should be alert for auroras. Aurora alerts: text, voice.
JUNO SPACECRAFT TO FLY BY EARTH: NASA's Juno spacecraft will slingshot past Earth on October 9th for a velocity boost en route to Jupiter. At closest approach the spacecraft will be only 347 miles above Earth's surface. This map shows the spacecraft's ground track:
During the flyby, Juno's science instruments will be activated to sample the Earth environment--a practice run for data-taking when the spacecraft reaches Jupiter in 2016. Despite the shutdown of the US government, "the flyby will continue as planned," says Juno principal investigator Scott Bolton of the Southwest Research Institute. "The commands associated with our instruments were already on board before the shutdown."
To celebrate this event, the Juno team invites amateur radio operators around the world to say "HI" to Juno in a coordinated Morse Code message. Juno's radio and plasma wave experiment, called Waves, should be able to detect the message if enough people participate. Please join in, and help spread the word to fellow amateur radio enthusiasts.
The spacecraft will not be visible to the unaided eye. Estimates of its maximum brightness range from magnitude +7.5 to +8.5. Such a faint object moving rapidly across the sky will be a challenge for even large backyard telescopes. There is a slim chance, however, that sky watchers could see a "Juno flare" if sunlight glints off the spacecraft's large solar arrays. Anyone who successfully photographs the spacecraft is encouraged to submit their images.
PS: If you want to see a really bright spacecraft, download our Satellite Tracker app and check out the International Space Station.
GIANT PROMINENCE, GONE: At the end of the day on Oct. 7th, reports of a giant prominence emerging over the sun's northeastern limb began to come in from around the world. "It was huge and easily visible in my Lunt 80mm solar scope," says Paul Haese, who sends this picture from Glenalta, South Australia:
By the morning of Oct. 8th, the prominence was gone. The structure's magnetic underpinnings became unstable and erupted, flinging part of itself into space. NASA's Solar Dynamics Observatory recorded the blast: movie. A coronal mass ejection is now emerging from the blast site, but Earth is not in the line of fire.
Realtime Space Weather Photo Gallery
SUNSET PLANETS: The crescent Moon is gliding by Venus, forming a pretty duo in the sunset sky. Last night, Brian Emfinger photographed the two bright bodies over Little Rock, Arkansas:
"The Moon and Venus provided a excellent backdrop to the Little Rock skyline," says Emfinger.
It's going to happen again tonight. Venus and the Moon are so bright, they pop out of the twilight long before the sunset sky fades to black. If you go out to look, be alert for Earthshine--a ghostly glow illuminating the crescent's dark terrain. Earthshine is sunlight reflected from our own planet onto the Moon. A crescent Moon with Earthshine framed by twilight blue is one of the most beautiful sights in the heavens. Sky maps: Oct. 7, 8.
Realtime Sunset Photo Gallery
COMET ISON IN COLOR: Comet ISON is brightening as it approaches the sun. Estimates by experienced observers put the comet between 10th and 11th magnitude. That's too dim to see with the unaided eye, but bright enough for color photography through mid-sized backyard telescopes. Michael Jäger of Weißenkirchen, Austria, observed the comet on Oct. 5th and found that it was green:
To image the comet, Jäger combined multiple exposures through red, green, blue, ultraviolet and infrared filters. Details may be found here.
ISON's green color comes from the gases surrounding its icy nucleus. Jets spewing from the comet's core probably contain cyanogen (CN: a poisonous gas found in many comets) and diatomic carbon (C2). Both substances glow green when illuminated by sunlight in the near-vacuum of space.
Finding Comet ISON is easy. It rises alongside Mars in the eastern sky just before dawn. Amateur astronomers, if you have a GOTO telescope, enter these coordinates. Special dates of interest include Oct. 13-15 when Mars, Comet ISON, and the first magnitude star Regulus will be clustered in a patch of sky less than 3o apart. Red Mars and blue Regulus will form a beautiful naked eye "double star" in the early morning sky. Sky maps: Oct. 8, 9, 10, 11, 12, 13, 14, 15.
Realtime Comet ISON Photo Gallery
Realtime Aurora Photo Gallery