Jupiter's moons are putting on an amazing show this month. The orbital path of the moons is tilting edge-ON to the Earth and the sun. This lineup makes it possible to watch the moons pass in front of each other.
What's Up for January. Jupiter.
Hello and welcome. I'm Jane Houston Jones from NASA's Jet Propulsion Laboratory in Pasadena, California.
Jupiter's moons are putting on an amazing show this month. The orbital path of the moons is tilting edge-ON to the Earth and the sun. This lineup makes it possible to watch the moons pass in front of each other, an occultation, or pass through another moon's shadow, an eclipse, and even cast tiny black shadows onto Jupiter!
Jupiter rises by 10:30 p.m. at the beginning of the month and by 8:30 at the end of the month. Even through the smallest telescope or binoculars you should be able to see the two prominent belts on either side of Jupiter's equator and the four Galilean moons: Io, Europa, Ganymede and Callisto.
Jupiter's Great Red Spot is challenging to spot now and it has actually shrunk to less than half the size of historical observations. It was 25,500 miles in diameter in the late 1800's. The Voyager spacecraft measured it to be 14,500 miles across in 1979. And recent Hubble telescope observations have found it to be 10,250 miles across. And it's shrinking by 580 miles per year.
On the night of January 23 and the morning of the 24th, three moons and their shadows cross the disk of Jupiter. If you want to try to see their shadows, you'll want to start looking through telescopes at 10 p.m. Eastern time. At 10:11 p.m. the first shadow--of Callisto-appears, followed by Io's shadow at 11:35 and Europa's at 1:27 a.m. Then for 25 minutes, until 1:52 a.m., the three black shadows will appear on the planet's disk at the same time. This triple shadow transit won't happen again until 2032.
There's one more treat in store for Jupiter observers this same morning. Io is eclipsed by Calisto's shadow, beginning at 12:41 a.m. Eagle-eyed observers will see Io dim in brightness about 10 minutes later, then resume its brightness in another 10 minutes.
You can learn more about all the bodies of our solar system and discoveries we've made there at: solarsystem.nasa.gov.
And you can learn about all of NASA's missions at: www.nasa.gov.
That's all for this month. I'm Jane Houston Jones.