ASTEROID FLYBY TODAY: Approaching from the direction of the sun, mountain-sized asteroid 2014 JO25 is flying past Earth today, April 19th, approximately 1.8 million km away. NASA says there is no danger of a collision, but it is close enough for amateur astronomers to photograph in backyard telescopes. It looks like a fast-moving speck of light (magnitude +11) zipping among the stars. Canadian astrophotographer Mario Hebert used a 10-inch telescope at the Parc national de la Mauricie in Quebec to capture this movie of 2014 JO25 nearing Earth on April 18th. Got an image? Submit it here.
SPECTACULAR CME: Old sunspot AR2644 has returned--and it is still active. On April 18th at approximately 2000 UT, the sunspot's magnetic canopy exploded and hurled a bright coronal mass ejection (CME) into space. The ESA/NASA Solar and Heliophysics Observatory caught the cloud as it raced away from the sun:
This CME will probably miss Earth. The explosion's epicenter was too far off the Sun-Earth line for a direct hit. NOAA analysts are still evaluating the possibility of a glancing blow, however, so stay tuned for updates.
More CMEs may be in the offing. In early April this sunspot produced a series of strong M-class flares and shortwave radio blackouts on Earth. Geoeffective activity stopped only when the sunspot went into hiding on the farside of the sun. Two weeks later it's back, and it is turning toward Earth for a new round of solar activity.
Note: By longstanding tradition, sunspots that travel around the backside of the sun and re-appear are renumbered. AR2644 therefore has a new designation: AR2651. We will use both names in our coverage of this active region in the days ahead.
SCINTILLATING SIRIUS: Sirius is the brightest star in the sky. It is also, arguably, the most colorful. On any given evening of northern Spring, sky watchers can behold a spray of rainbow colors emanating from the Dog Star as it sets low in the southwestern sky. Tom Wagner of Waterloo, Iowa, has developed a beautiful way to display the star's hue. "Decades ago I discovered that by wiggling my binoculars while looking at Sirius, I could easily see the colors of the rainbow flash by in rapid succession." On April 16th he took this picture through the eyepiece:
"This is a 2 second exposure," he says. "The colors were spectacular!"
Astronomers call this phenomenon "scintillation." Also known as "twinkling," the phenomenon is caused by thermal irregularities in Earth's atmosphere. As packets of relatively warm and cool air drift in front of a star, the star's light is refracted. The prismatic action of these air packets produce rainbow colors--especially near the horizon where starlight must pass through many turbulent irregularities to reach the observer.
All stars scintillate, but Sirius does so most flamboyantly because of its extreme brightness. See for yourself. Step outside this evening after sunset and look southwest for Sirius near the feet or Orion. The lower it gets, the more it twinkles. Enjoy the show!
Realtime Space Weather Photo Gallery