When is the best time to see auroras? Where is the best place to go? And how do you photograph them? These questions and more are answered in a new book, Northern Lights - a Guide, by Pal Brekke & Fredrik Broms.
| || |
JUNO SPACECRAFT PHOTOGRAPHED: Yesterday, NASA's Juno spacecraft buzzed Earth only 347 miles above our planet's surface. It was a slingshot maneuver designed to gain velocity for Juno's long trip to Jupiter (ETA: 2016). Although the spacecraft was very faint, several amateur astronomers managed to photograph it: image gallery. The spacecraft is now hurtling away from Earth at 23,500 mph. Bon voyage, Juno!
SUNDIVING COMET: Comet ISON is not the only comet diving toward the sun. Another smaller comet is feeling the heat today. Using a coronagraph to block the sun's glare, the Solar and Heliospheric Observatory (SOHO) is monitoring the comet's death plunge:
This comet is a member of the Kreutz family. Seen falling into the sun dozens of times each year, Kreutz sungrazers are fragments from the breakup of a single giant comet many centuries ago. They get their name from 19th century German astronomer Heinrich Kreutz, who studied them in detail.
Today's sungrazer is probably doomed. The vast majority of Kreutz comets are small (no more than ~10 m wide) and they evaporate completely as they approach the sun. Comet ISON, on the other hand, is large (~0.5 km wide) and widely expected to survive its brush with the sun on Nov. 28th. It's a tale of two comets!
Update: A new movie from SOHO shows the comet making its final closest approach to the sun.
Realtime Space Weather Photo Gallery
RADIO-ACTIVE SUN: Radio amateurs, have you heard any strange roaring sounds coming from the loudspeakers of your shortwave radios this week? It might have been the sun. "The Sun has been generating Type III solar radio bursts and they appear to be intensifying," reports amateur radio astronomer Thomas Ashcraft of New Mexico. "The strongest burst so far came at 2155 UTC on October 9th." Here it is as recorded on two radios at 28 MHz and 21 MHz:
Ashcraft recommends listening to the audio using stereo headphones. "Type III bursts drift downward in frequency," he explains. "In stereo you can hear the burst pass through 28 MHz first on one speaker and then flow through 21 MHz on the other sound speaker."
Type III solar radio bursts are produced by electrons accelerated to high energies (1 to 100 keV) by solar flares. As the electrons stream outward from the sun, they excite plasma oscillations and radio waves in the sun's atmosphere. When these radio waves head in the direction of Earth, they make themselves heard in the loudspeakers of shortwave radios around the dayside of the planet.
More radio bursts could be in the offing. NOAA forecasters estimate a 25% chance of M-class flares and a 5% chance of X-class flares during the next 24 hours. Stay tuned! Solar flare alerts: text, voice.
Realtime Space Weather Photo Gallery
GREEN COMET ISON: Comet ISON is brightening as it approaches the sun. At the moment it is glowing like a 10th magnitude star, too dim for naked eye viewing but an easy target for many telescopes on Earth. "This is what the comet looked like on Oct. 8th using the 0.8m (32 inch) Schulman Telescope," reports Adam Block from the University of Arizona Skycenter atop Mount Lemmon:
ISON's green color comes from the gases surrounding its icy nucleus. Jets spewing from the comet's core contain diatomic carbon (C2) and cyanogen (CN: a poisonous gas found in many comets). Both substances glow green when illuminated by sunlight in the near-vacuum of space.
"I am certain more images of Comet ISON will be coming out shortly as it increases in brightness during its dive towards the Sun," adds Block. "Here is hoping it survives that rendezvous on Nov. 28th and emerges as something spectacular on the other side!"
Although the comet is very faint, finding it is easy. Comet ISON 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. 10, 11, 12, 13, 14, 15.
Realtime Comet ISON Photo Gallery
Realtime Aurora Photo Gallery