The sky has been deceptively quiet of late, but things are brewing. Tomorrow morning a thin crescent moon parks just shy of a fist to the right of the planet Venus. The best time to see the pair will be around 40 minutes before sunup low in the southeastern sky.
During the evening hours you can watch the bright asteroid Pallas ply the heavens with nothing more than a small telescope or pair of 50mm binoculars. 2 Pallas, the second asteroid discovered after Ceres, was found by German astronomer Heinrich Olbers on March 28, 1802. As far as asteroids go, it’s big — at 318 miles (512 km) across, Pallas ranks as third largest. It orbits in the main belt between Mars and Jupiter and makes one orbit of the sun every 4.6 years.
Just like a planet, it’s closest to Earth and brightest at opposition, when asteroid, Earth and sun line up in that order. That happens on April 6, making the entire month ideal for following its track among the stars. Pallas shines at magnitude 7.9 which puts it within binocular range for suburban and rural skywatchers. If light pollution brightens your sky then you’ll need a small telescope. And I do mean small. Even a spotting scope will pop it into view.
Pallas and all the other asteroids look exactly like stars because they’re all too small to show a disk like the planets do. That’s why astronomers settled on the name asteroid in the first place, after the Greek “aster” and “oides” for star-like. Other names considered but rejected included planetkin, planeret, planetling or even stellula. I’m kind of sweet on planetkin but that train left the station long ago. Originally, Pallas and friends were called planets, but so many were discovered, and they were all tiny and occupied the same zone between Mars and Jupiter, astronomers came to realize they were in a category all their own.
To find Pallas you only need to find Arcturus. It’s that unmistakably bright, twinkling orange star that glimmers low in the northeastern sky below the handle of the Big Dipper. If you have a clear view east you can see it as early as 8:30 p.m. but better to wait till around 10 o’clock when it climbs to a convenient height.
The fun part of Pallas-watching is first in finding the asteroid (congratulations in advance!) and then watching it slowly move night to night against the background of the distant stars. Some observers like to sketch the star field on paper and then plot the asteroid’s position on clear nights. Right now, Pallas shines just about 5° southwest of Arcturus and will remain within 5° of the star through the 11th. Why is 5 a happy number? Because that’s about the field of view of a typical pair of binoculars. So if you can find Arcturus, Pallas will be close by.
The map shows the position of Pallas each night around 10 p.m. Central Time. It moves only a very small distance in several hours time, so the positions shown will work for all time zones across the continental U.S., Canada, Central and South America. For other locations just interpolate between the dates. On the evening of the 10th, the asteroid passes very close to Muphrid — too close for binoculars but a telescope will show it, and if you’re patient, you can watch it move in relation to the star in just an hour or two.
We may learn much more about Pallas soon plus get a bounty of close-up photos. NASA is considering funding a small satellite called Athena that would piggyback on the Psyche Mission to the metal-rich asteroid 16 Psyche. After launching in August 2022, the two spacecraft would part ways, with Athena getting a gravity assist from Mars to fling it onward to Pallas for a 2024 flyby.
You needn’t wait till 2024 to get to know Pallas. Just poke your head out the next clear night.