There were eight C flares on the Sun during the past 24 hours, released by NOAA AR 11928 and 11936. The brightest one was a C4.7 flare from NOAA AR 11928 peaking at 06:39 UT on December 25. In the next 48 hours, the probability for C flares is high (around 70%) and for M flares around 25%, mainly from NOAA AR 11928 and 11936.Solar wind speed as observed by ACE suddenly increased from about 290 to 320 km/s around 20:40 UT on December 24, accompanied by a rise in solar wind density. Since then, the magnitude of the Interplanetary Magnetic Field has gradually increased from about 3 to about 12 nT and its phi angle behaved chaotically until 4:00 UT on December 25, when it started increasing linearly over time. These measurements are consistent with the arrival of the flux robe of an unidentified CME around 4h UT on December 25, preceded by a shock which started around 20:40 UT on December 24. Though Bz is having extended periods of -10 nT, geomagnetic activity has remained quiet over the past 24 hours (NOAA Kp between 0 and 3). Due to the expected arrival of a coronal hole high speed stream, quiet to active geomagnetic conditions are expected in the second half of December 25 and on December 26, with a chance of minor storm excursions. Quiet to active conditions are likely on December 27. SIDC
Equipment: Coronado 90 + SBIG 8300s + LX75 Processing: Photoshop Date: 12/25/13 Time UT: 01:00 Exposure 0.8 sec.
Explanation: What does the Martian moon Phobos look like? To better visualize this unusual object, images from ESA’s Mars Express orbiter have been combined into a virtual rotation movie. The rotation is actually a digital illusion – tidally-locked Phobos always keeps the same face toward its home planet, as does Earth’s moon. The above video highlights Phobos’ chunky shape and an unusually dark surface covered with craters and grooves. What lies beneath the surface is a topic of research since the moon is not dense enough to be filled with solid rock. Phobos is losing about of centimeter of altitude a year and is expected to break up and crash onto Mars within the next 50 million years. To better understand this unusual world, Mars Express is on course to make the closest flyby ever on Sunday.
APOD NASA 25-dec-13
The brilliant, blue glow of young stars traces the graceful spiral arms of galaxy NGC 5584. Among the galaxy’s myriad stars are pulsating stars called Cepheid variables and one recent Type Ia supernova, a special class of exploding stars. Astronomers use Cepheid variables and Type Ia supernovae as reliable distance markers to measure the universe’s expansion rate. NGC 5584 was one of eight galaxies astronomers studied to measure the universe’s expansion rate.
NGC 281 is an H II region in the constellation of Cassiopeia and part of the Perseus Spiral Arm. It includes the open cluster IC 1590, the multiple star HD 5005, and several Bok globules. Colloquially, NGC 281 is also known as the Pacman Nebula for its resemblance to thevideo game character.