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. | | |
SPACECRAFT GOES INTO LUNAR ORBIT: Mission controllers flying NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft are among the select few at the space agency who have exemptions allowing them to work during the government shutdown. On the morning of Oct. 6th, they fired LADEE's main engine in a braking maneuver. This slowed the spacecraft enough for it to be captured by the Moon's gravity. The insertion burn went flawlessly and LADEE is now in lunar orbit. Two more main engine burns, on Oct. 9th and 12th, will adjust LADEE's trajectory, settling it into its commissioning orbit. LADEE is on a mission to study the exotic and diaphanous lunar atmosphere, which is mightily affected by space weather.
SUNSET PLANETS: When the sun goes down tonight, step outside and look southwest. The crescent Moon and Venus are gathering for a wide but beautiful conjunction. Denis Crute sends this picture from Parkes, NSW, Australia:
"What a nice view just after sunset," says Crute."This picture is a 2 second exposure @ ISO 1600."
Tonight and tomorrow, the crescent Moon will pass by Venus, forming a bright duo visible long before the sky fades to black. Also, 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. Don't miss it! 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
FARSIDE CORONAL MASS EJECTION: The Earthside of the sun is quiet, but the farside of the sun is not. During the early hours of Oct. 5th, NASA's STEREO-A probe, stationed over the farside, recorded the eruption of a southern hemisphere sunspot. Shortly after 07:30 UT, a coronal mass ejection (CME) flew over the sun's southeastern limb (credit: SOHO):
Radio emissions from shock waves in the CME suggest an expansion velocity of about 700 km/s (1.6 million mph), which is fairly typical of CME speeds. If Earth were in the line of fire, we would probably observe bright polar auroras in a few days. However, this CME is heading away from, not toward our planet.
The active region that produced the blast will rotate onto the Earthside of the sun in about 4 days. If it remains potent, geoeffective solar activity could increase later this week. Solar flare alerts: text, voice.
Realtime Space Weather Photo Gallery
Realtime Aurora Photo Gallery