Astro Bob: Excitement at dawn as planets, moon pair up in conjunction
The dawn crescent meets Venus on Friday, May 27. Two days later, Mars and Jupiter get really close.
Get ready to set your alarm. We have a couple exciting sky events coming up. On Friday morning, May 27, the waning moon will shine a little more than 3 degrees to the lower left (east) of Venus low in the southeastern sky at dawn.
You'll see them best about an hour before sunrise . Just make sure you're somewhere that has an open view in that direction. Bring your phone, too. The sky will be bright enough to capture the pair in a scene.
For the Americas, the moon will have already passed Venus by the time the two rise into view. From the East Coast they'll stand about 3 degrees apart; from the West Coast, a little more than 4 degrees. In Europe and Africa, where dawn begins hours before it does in the U.S., observers will see the duo less than a degree apart.
Those lucky viewers will witness a conjunction because the alignment will be exact, and the two bodies will come as close together as they can for this particular event. In the Americas, they'll be close, but not closest, an event technically called an "appulse."
U.S. skyhounds will do better Sunday, May 29, when Mars slides under Jupiter at dawn. The two planets will be only a half-degree or one moon-diameter apart. That's a close one! Tight enough to see them both in the same field of view through a telescope.
If you have a scope, don't miss the opportunity to see three or four of Jupiter's brightest satellites, called the Galilean moons. All four will be in view up until 4:20 a.m. CDT. At that time, Io, the innermost moon, treads into Jupiter's shadow and disappears in eclipse.
Jupiter is by far the brighter orb, shining at magnitude -2.2, with Mars almost three magnitudes fainter at 0.7. You can enjoy the sight with just the naked eye or check out the view in binoculars. Should bad weather interfere, the two planets will hang close from May 27 through early June, so you'll have additional opportunities. But the best morning will be May 29, when they're squeaky tight.
Conjunctions and appulses occur because the planets orbit the sun like runners in an endless marathon. From our earthly perch, we get to watch their travels and cheer on our favorites.
Like the moon, planets travel to the east — left in the northern hemisphere. The rate at which a planet moves across the sky depends upon its distance: Closer ones move faster than farther ones. When Mars and Jupiter team up this weekend, we'll see a dramatic illustration of the concept.
Although it's tempting to picture the bigger, more "dominant" planet (Jupiter) approaching and overtaking Mars, just the opposite is true. Mars is much closer to us, so its motion across the sky is faster. The Red Planet will have no problem putting the tortoise-like giant in its rear view mirror. If you can soldier the effort to get up early several mornings in a row, you can watch the entire dance as Mars approaches and then passes Jupiter.
Every conjunction is an opportunity for skywatchers to get a "backstage tour" of the solar system inner workings. Seize it!
"Astro" Bob King is a freelance writer for the Duluth News Tribune.