SOLAR WIND, INCOMING: A wide hole is opening in the sun's atmosphere, and it is spewing a stream of solar wind toward Earth. G1-class geomagnetic storms are possible when the gaseous material arrives on April 19-20. Sky watchers between 50o and 60o N latitude should also be alert for STEVE, which tends to appear in that latitude range during springtime geomagnetic storms. Free: Aurora Alerts
SURPRISE ASTEROID FLYBY: With little warning, a relatively large asteroid flew through the Earth-Moon system on April 15th only 192,200 km (0.5 LD) from our planet. 2018 GE3 was discovered by the Catalina Sky Survey approaching Earth on April 14th. Hours later, amateur astronomer Michael Jäger of Weißenkirchen Austria video-recorded the space rock rushing through the southern constellation Serpens:
"According to wikipedia, 2018 GE3 is the largest known asteroid to pass that close to Earth in observational history," says Jäger. "It was shining like a 13th magnitude star at the time of my observations."
Based on the intensity of its reflected sunlight, 2018 GE3 must be 48 to 110 meters wide, according to NASA-JPL. This puts it into the same class as the 60-meter Tunguska impactor that leveled a forest in Siberia in 1908. A more recent point of comparison is the Chelyabinsk meteor--a ~20-meter asteroid that exploded in the atmosphere over Russia on Feb. 15, 2013, shattering windows and toppling onlookers as a fireball brighter than the sun blossomed in the blue morning Ural sky. 2018 GE3 could be 5 to 6 times wider than that object.
If 2018 GE3 had hit Earth, it would have caused regional, not global, damage, and might have disintegrated in the atmosphere before reaching the ground. Nevertheless, it is a significant asteroid, illustrating how even large space rocks can still take us by surprise. 2018 GE3 was found less than a day before before its closest approach.Based on an observational arc of only 1 day, 2018 GE3 appears to follow an elliptical orbit which stretches from the asteroid belt to deep inside the inner solar system. Every ~2.5 years the space rock crosses the orbits of Mercury, Venus, Earth, and Mars--although not necessarily making close approaches to the planets themselves. An interactive 3D orbit of the asteroid is available from JPL: explore it here!
COMPLEX ICE HALO DISPLAY: Many of us have seen a sun halo--a ring around the sun caused by ice crystals in clouds. The luminous rings are usually simple circles. On March 30th, however, things got complicated. "I saw an incredibly complex ice halo," reports Matthew Cook, who sends this picture from Ann Arbor, Michigan:
In Cook's photo, we see a complete parhelic circle, a circumscribed halo, a supralateral arc, a 22-degree halo, and a pair of sundogs. "It was a great display," he says.
Complex halos like this require not just one type of ice crystal, but many, with gem-like perfection and unusually precise crystal-to-crystal alignment. Clouds that contain such a rare ensemble of ice crystals are rare--but perhaps not as rare as you might suppose. Atmospheric optics expert Les Cowley discusses the odds of seeing such a display from your own backyard.
Realtime Space Weather Photo Gallery
MOTHER'S DAY IS LESS THAN 1 MONTH AWAY: Nothing says "I Love You" like a heart-shaped pendant from the edge of space. On Dec. 31, 2017, the students of Earth to Sky Calculus flew an array of cosmic ray sensors to the stratosphere onboard a giant helium balloon. This pendant went along for the ride:
You can have it for $119.95. The students are selling these pendants as a fund-raiser for their cosmic ray monitoring program--and they make great Mother's Day gifts. All proceeds support atmospheric radiation measurements and hands-on STEM education.
Each pendant comes with a greeting card showing the jewelry in flight and telling the story of its journey to the stratosphere and back again. Mom-satisfaction guaranteed.
Far Out Gifts: Earth to Sky Store
All proceeds support hands-on STEM education