Astro Bob: Spot Comet K2 PanSTARRS as we tilt into summer
As we celebrate the new season a brightening comet beckons.
DULUTH — When someone leans in toward you and speaks, you sit up and pay attention. Tuesday, the Earth leans into the sun as far it can go, and I'm hearing SUMMER loud and clear. Here in northern Minnesota, the new season arrived in full force with a heat wave followed by overnight thunderstorms.
Summer in the northern hemisphere began officially at 4:13 a.m. Central Daylight Time on Tuesday morning, June 21. At that moment, the sun reached its highest point in the sky for the year. For 16 hours or more it will blaze over mountains, cities and plains, marking the longest day of the year.
Since the Dec. 21 winter solstice, the sun has been slowly moving northward (up) in the sky. Now at its pinnacle it rises early and sets late. Increased daylight as well as the steeper angle at which sunlight strikes the Earth intensify the summer heat. In winter, the sun is closer to the horizon, so its rays (energy) are spread out over a larger area and therefore weaker. Short days also reduce how much energy and light we receive, increasing the chances of icicles hanging off our noses.
All the extra light and energy that drive the season's long days and at times insufferable heat boil down to a simple happenstance — the tilt of Earth's axis. Earth orbits the sun in a slouching posture, its axis angled 23.5°.
On the summer solstice, Earth's northern hemisphere fully tilts toward the sun, elevating it to its highest point in the sky. Six months later, we're tipped away, and the sun's altitude drops to its minimum. In between, at spring and fall, the sun appears midway between both extremes, and temperatures moderate.
June's late-setting sun means you have to stay up till 10:30 p.m. or even 11:30 p.m. before the sky gets dark. I hope that doesn't put you off because we have a little comet you might like to see called PanSTARRS (C/2017 K2) or just "K2." Currently at magnitude 9, it's faintly visible from rural skies in a small, 4.5-inch telescope. From a more light-polluted location you'll probably need a 6-inch.
Discovered in May 2017 by the University of Hawaii's PanSTARRS telescopic survey , it hails from the remote Oort Cloud, a gigantic, roughly spherical cloud of comets 2,000 to 200,000 times Earth's distance from the sun. Like moths around a streetlight the comets orbit the sun until a disturbance, such as a passing star, gives them a gravitational nudge, sending them falling toward the inner solar system.
I've been tracking "K2" for a couple years now, patiently watching it brighten incrementally and grow a short tail. I'm hopeful you'll be able to see it, too. Larger instruments will show the tail; in smaller scopes expect to see a small, fuzzy blob with a brighter center. One of the cool things about comets is watching them move night to night. K2 is currently traveling southwest across the big, bell-shaped constellation Ophiuchus, chugging along at not quite a full moon diameter (1/2°) per night.
For the next several nights, it will be near the naked-eye star Beta Ophiuchi. We're going to take advantage of that bit of good fortune. The wide-view map will help you locate the star. Once you've centered it in your telescope's eyepiece, use the more detailed map to work your way to the comet. The detailed map shows the comet's position around 11 p.m. CDT. Don't worry if you observe it up to a few hours before or after — K2 will still be close to the positions marked.
If you don't see it now, no worries. It will brighten by at least a magnitude in the coming weeks and get easier to see. I'll have another map for you to use then. Happy solstice!
"Astro" Bob King is a freelance writer for the Duluth News Tribune.