MARTIAN TRIANGLE: On the same night Curiosity lands on Mars, a "Martian Triangle" will appear in sunset skies of Earth. The first-magnitude apparition on August 5th gives space fans something to do while they wait for news from the Red Planet. [video] [story]

INCOMING CME, WEAK IMPACT EXPECTED: A coronal mass ejection (CME) produced by Saturday's M6-class flare is heading toward Earth. According to analysts at the Goddard Space Weather Lab, the cloud could deliver a glancing blow to our planet's magnetic field on July 31st around 1500 UT (+/- 7 hours). Click to view the animated forecast track:

This is a slow-moving CME. The cloud's low speed (382 km/s estimated) combined with its glancing trajectory suggests a weak impact is in the offing. Nevertheless, polar geomagnetic storms are possible when the cloud arrives. Aurora alerts: text, voice.

MARS LANDING SKY SHOW: On the same night Curiosity lands on Mars, a "Martian Triangle" will appear in sunset skies of Earth. The first-magnitude apparition on August 5th gives space fans something to do while they wait for news from the Red Planet. [video]

DELTA AQUARID METEOR SHOWER: This weekend, Earth is passing through a stream of debris from Comet 96P/Machholz, source of the annual delta Aquarid meteor shower. Forecasters expect as many as 15 meteors per hour when the shower peaks on July 28-29. The location of the shower's radiant below the celestial equator favors southern hemisphere observers. Nevertheless, northerners can see it too. For instance, David Hoffmann caught this early delta Aquarid flashing over Ashland, Oregon, on July 24th:

"A movie of the meteor may be found on my Youtube page," says Hoffman.

Although this is a minor shower, it is fraught with interest. Some researchers believe that the delta Aquarids' parent comet, 96P/Machholz, came from another star system. Every delta Aquarid that disintegrates in the night sky could be depositing material from across the galaxy into Earth's upper atmosphere.

LONG RANGE OUTLOOK: A stream of solar wind is heading for Earth, due to arrive on July 28-30. High-latitude sky watchers should be alert for auroras on those dates in case the impact sparks geomagnetic storms. Aurora alerts: text, voice.

MAGNETIC BRIDGE: Sunspots AR1528 and AR1529 appear to be far apart. More than 200,000 km of stellar surface separate the two. Nevertheless, they are connected by a tubular bridge of magnetism. NASA's Solar Dynamics Observatory (SDO) photographed the vast structure on July 24th:

This extreme ultraviolet image traces the bridge via the glow of hot plasma it contains. Material can flow back and forth inside the tube, allowing one sunspot to respond to what the other is doing.

NOT AURORAS: On some nights when the moon is new and city lights are far away, the sky turns green. But it's not the aurora borealis--it's airglow. Brian Larmay photographed the phenomenon on July 20th from the countryside near Beecher, Wisconsin:

"The airglow was intense enough to see visually," says Larmay. "I decided to create a brief animation of this phenomena with an 8mm fisheye lens which can be seen here."

Although airglow resembles the aurora borealis, its underlying physics is different. Airglow is caused by an assortment of chemical reactions in the upper atmosphere. During the day, ultraviolet radiation from the sun ionizes atoms and breaks apart molecules. At night, the atoms and molecules recombine, emitting photons as they return to normal. This process produces an aurora-like glow visible on very dark nights.

A TASTE OF SOLAR MAX: Forecasters say solar maximum is still a year away. Earlier this month sky watchers got a taste of things to come when a powerful flare sparked Northern Lights over the United States as far south as Arkansas, Colorado and California. [full story] [video]

AROUND THE BEND? The Earth-facing side of the sun is mostly blank and quiet. This could change in the days ahead as a new sunspot emerges over the sun's southeastern limb. NASA's Solar Dynamics Observatory can see the active region's magnetic canopy, which is towering over the limb in advance of the sunspot itself:

The core of the active region should show itself no later than Tuesday. Meanwhile, solar activity is low. NOAA forecasters estimate a mere 1% chance of M- or X-class solar flares. Aurora alerts: text, voice.