Astro Bob: Aurora alert July 21-23, plus planet happenings
We have a fair chance of seeing northern lights the next few nights as multiple blasts arrive from the sun.
The sun's been dishing it out lately. Between coronal holes and several recent eruptions called coronal mass ejections (CMEs), a slew of electrons and protons have been racing toward our planet eager for a connection. Let's hope we can give it to them.
Specifically, they seek to link into Earth's magnetic field, where if successful, they'll be accelerated to 45 million miles an hour (72 million kilometers per hour) and slam into the thin upper atmosphere. Oxygen and nitrogen atoms struck at those speeds suddenly become energized and just as quickly release that energy in the form of green, pink and blue light. Voila — the aurora borealis!
On Thursday, July 21, we may experience the effects of a coronal hole, a high-speed stream of particles gushing from the sun like a water from a fire hose. The latest forecast predicts a possible G1 (minor) storm beginning during the afternoon and continuing into the early evening hours Central Daylight Time. We all know the aurora can be capricious, so the blast could arrive somewhat earlier (in which case North American observers would miss it) or later.
More excitement may be in the offing when a July 20-21 CME arrives Friday, July 22. That encounter could spark a minor to moderate (G2) geomagnetic storm with auroras possible from 10 p.m. until dawn Friday night, July 22, through Saturday morning, July 23. The waning crescent moon rises late and won't bother the show. Clear or cloudy, I'll update the status of the storm status on my Facebook page " Astronomy for Everyone ."
I don't mean to disparage the moon. For instance, the morning of Friday, July 22, it will guide observers to the planet Uranus, currently located between Mars and the Pleiades star cluster. If you're up early hunting northern lights, use the map and a pair of binoculars to track it down. Next week, we'll have an even better opportunity to spot the cloud-enshrouded seventh planet. Stay tuned!
Meanwhile, Saturn and Jupiter continue to push into the evening sky. Saturn's up and easy to see low in the southeast by 11 p.m. local time, with Jupiter arriving on the scene around midnight. You'll notice a fainter star just 1.5° below the ringed planet. That's 3rd magnitude Deneb Algedi in Capricornus, a white giant about twice as big as the sun located 39 light-years away.
Binoculars will show three additional fainter stars — 45, 44 and 42 Capricorni from bottom to top — that form an attractive arc just above Saturn. The planet is moving westward right now and will slowly distance itself from the tiny asterism in the coming nights.
Jupiter really grabs the eye. It's incredibly brilliant even when close to the horizon. I'm not used to seeing such a bright planet in the evening sky — truly a welcome addition. The gas giant shines at magnitude -2.6, the typical brightness of the International Space Station, and rises nearly due east in Pisces a full 45° to the left (east) of Saturn.
"Astro" Bob King is a freelance writer for the Duluth News Tribune.