Aurora Alert Tonight Dec. 17 / Review: Cosmic-Watch App

The sun is spotless today. Solar activity’s been low lately, but you don’t necessarily need spots to have solar storms and auroras. Large holes in the sun’s corona allow high speed streams of electrons and protons to stream toward Earth. Sometimes they find a way past the planet’s magnetic defenses and spark a display of northern lights. NASA/SDO

Particles streaming from solar blowhole and the side-effects of a Dec. 15 blast will combine to up our chances of seeing the northern lights the next two nights. Spaceweather experts predict minor storming (Kp=5) starting this evening around (updated) 6 p.m. Central Time and continuing through about midnight.

“Minor” usually means that observers in the northern states will see an arc and a few modest rays poke up across the northern sky. The solar disturbance will reverberate through at least Monday night with a possibility of auroras from roughly 9 p.m. that evening till almost dawn Tuesday. The sun is currently spotless as we approach the minimum of the solar cycle in 2019-2020. While big-time auroras are less likely during minimum, they still happen from time to time thanks to coronal holes, fluctuating particle-wind speeds and outbursts of material (coronal mass ejections) caused by magnetic instabilities. The sun can play the wild card anytime it likes.

Cosmic-Watch in Clock mode, centered on Duluth, Minn. (beacon at top). The white “hour hand” points to 10 a.m. In the live version, clicking the “three dot icon” at top right lets you choose modes. You can zoom in and view the Earth and sky from any angle using your fingers; movements are subtle and fluid, almost tactile. Celestial Dynamics AG

Who says the Earth isn’t the center of the universe? I’ve been playing with a new app for iPhone and iPad ($4.99) and Android ($4.49) called the Cosmic-Watch. This graphically-beautiful app displays the globe of the Earth (day or night) “orbited” by a clock face and set against the backdrop of constellations and planets. The current time is the default, but you can pick any time up to 1,000 years in the past or future. To set location (from a database of 15,000 cities), click the magnifying glass icon and type in your city.

The app has four basic modes. To activate any of them, select from the row of icons in the side menu:

    • Clock mode (default): Shows the Earth globe, day-night terminator, your location and celestial sphere (with sun, 7 planets, etc.) for the current time
    • Astronomy mode: Earth globe surrounded by the constellations, planets, moon and sun. You can use this mode to find out where the planets are in your local sky. In Settings, you can advance time (or run it backwards) to find out the rising and setting times for the planets.
    • Astrology mode: Shows planet symbols and positions in the zodiac constellations.
    • Solar system mode: I really like this feature. Shows a wide view of the solar system with the planets’ current positions. Great for understanding at a glance why some planets appear close to the sun (near conjunction) and others appear opposite the sun in the night sky. Select the Connections mode to see sight lines from Earth to each of the planets. Online manual at
The app in Astronomy mode shows the constellations as viewed from the outside looking back at Earth. Celestial Dynamics AG

The app’s strengths are its accuracy, ease of of use, gorgeous graphics and many options. Click the gear wheel, select a mode and you can change the globe’s appearance, add the horizon, compass, hi-res Earth views, a deeper, richer starry backdrop and much more. My only criticism is the constellations. In astronomy mode — especially on a small phone display — they get scrunched and make for a busy screen. The stars in the figures are also connected in non-traditional ways and may be confusing for some, so I’d recommend using them as a general guide. Others have complained that the flashing beacon marking your location is too big, but I had no problem with it.

See where the planets are in relation to each other any time of day or night in Solar System mode. Celestial Dynamics AG

One of the toughest things about astronomy is visualizing how the sun, moon and planets move in relation to the Earth and to each other. Cosmic-Watch shows these relations in a pleasing and intuitive way that will enlighten beginners and delight more experienced observers.