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.
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SLIGHT CHANCE OF FLARES: The Earthside of the sun is quiet. NOAA forecasters estimate a slim 1% chance of either M- or X-class solar flares on Nov. 27th. However, there is at least one active region on the farside of the sun which could target Comet ISON when it swings around the farside after Nov. 28th. Solar flare alerts: text, voice
COMET ISON, SO FAR SO GOOD: Comet ISON is hurtling toward the sun today at 240,000 mph and, despite the rising heat, the comet appears to be intact. Yesterday, reports of fading spectral lines from the comet's core raised concerns that the icy nucleus might be disintegrating. Current images from NASA and ESA spacecraft, however, show the comet still going strong. Comet ISON has just entered the field of view of the Solar and Heliospheric Observatory (SOHO):
The comet's entrance coincides with a bright CME racing away from the sun's southwestern limb. Astronomers have been wondering what might happen if a CME strikes Comet ISON. This CME, however, will probably miss. The source of the cloud is a farside active region, which is not directly facing the comet.
NASA's STEREO-A spacecraft is also monitoring the comet. Click to view a high-resolution movie (32 MB), which compresses 96 hours into less than 1 minute:
Credits: This movie was made by reader Rob Matson using data from STEREO-A.
The movie spans a 3+ day interval from Nov. 21 to Nov. 24 roughly centered on the period when astronomers at the IRAM telescope in Spain recorded fading emission lines from the comet's core. Zoom your movie-player to full screen: Although "puffs" of material can be seen billowing down the comet's tail, the comet itself does not appear to be disintegrating. So what caused the fade...?
"I will admit that I was pretty worried yesterday morning when reports of lower production rates came in," says Matthew Knight of the Lowell Observatory and NASA's Comet ISON Observation Campaign. "However, the STEREO-A brightness has increased steadily over the subsequent 36 hr, and I'm more optimistic again. My off-the-cuff thought is that there was an [outburst of dust, which dampened the emission lines] from roughly Nov 20-22, and it has returned to brightening again."
Astronomer Karl Battams of NASA's Comet ISON Observing Campaign urges readers to remember the following: "Comet ISON is a dynamically new sungrazing comet, fresh in from the Oort Cloud, and the last time we saw an object like this was never! Furthermore, a sungrazing comet just days from perihelion has never been studied in this kind of detail - we're breaking new ground! When we factor in your standard 'comets are unpredictable' disclaimer, what we have is a huge recipe for the unknown."
Stay tuned for updates.
Realtime Comet ISON Photo Gallery
WHICH SIDE OF THE SUN IS FACING COMET ISON? When Comet ISON sweeps through the sun's atmosphere on Nov. 28th, it will be in the 'hot zone' for CMEs. A strike by one of the massive storm clouds probably wouldn't destroy the comet, but it could have a dramatic effect on the comet's fragile tail. The odds of a strike depend on which side of the sun is facing the comet at the time of the flyby. This is something you can monitor using a NASA iPhone app called the Interplanetary 3D Sun:
The app displays an interactive 3D model of the entire sun photographed by extreme UV cameras onboard NASA's twin STEREO probes. The data are realtime and fully interactive (pinch, spin and zoom). As shown in this target list, you can view the sun from many locations around the solar system--including Comet ISON.
Active regions are color-coded by their potential for flares: Orange means "expect M-class solar flares," while red denotes sunspots capable of X-flares. In the screen shot above we see that, on Nov. 25th, Comet ISON was bearing down on an active region, AR1904, that posed a threat for M-class eruptions. What is targeting the comet today? Download the app and find out. Solar flare alerts: text, voice
Realtime Space Weather Photo Gallery
Realtime Aurora Photo Gallery
Every night, a network of NASA all-sky cameras
scans the skies above the United States for meteoritic fireballs. Automated software maintained by NASA's Meteoroid Environment Office calculates their orbits, velocity, penetration depth in Earth's atmosphere and many other characteristics. Daily results are presented here on Spaceweather.com.
On Nov. 27, 2013, the network reported 3 fireballs.
In this diagram of the inner solar system, all of the fireball orbits intersect at a single point--Earth. The orbits are color-coded by velocity, from slow (red) to fast (blue). [Larger image] [movies]
Potentially Hazardous Asteroids (PHAs
) are space rocks larger than approximately 100m that can come closer to Earth than 0.05 AU. None of the known PHAs is on a collision course with our planet, although astronomers are finding new ones
all the time.
On November 27, 2013 there were 1439 potentially hazardous asteroids. Notes: LD means "Lunar Distance." 1 LD = 384,401 km, the distance between Earth and the Moon. 1 LD also equals 0.00256 AU. MAG is the visual magnitude of the asteroid on the date of closest approach.
| ||The official U.S. government space weather bureau |
| ||The first place to look for information about sundogs, pillars, rainbows and related phenomena. |
| ||Researchers call it a "Hubble for the sun." SDO is the most advanced solar observatory ever. |
| ||3D views of the sun from NASA's Solar and Terrestrial Relations Observatory |
| ||Realtime and archival images of the Sun from SOHO. |
| ||from the NOAA Space Environment Center |
| ||the underlying science of space weather |