As night’s window envelopes the world, a bright point of light rises in the east. It appears a few hours after dark, shining extremely brightly and dominating the night sky for the rest of the night — but what is it?
Jupiter, the “King of Planets,” will soon reach its biggest, brightest and best. The largest planet in the solar system is currently shining a magnitude of -2.8 and is high in the eastern night sky soon after dark. Why?
Jupiter At Opposition
The giant planet is close to what astronomers call opposition. On Dec. 7, 2024, Jupiter will align with the sun and the Earth. Or, rather, Earth’s faster orbit will momentarily put it between the sun and Jupiter. Consequently, we’ll be able to see 100% of the disk of Jupiter, which will also be as close as it can ever be to Earth, at 380 million miles (612 million kilometers).
Since we’re now just a month away from Jupiter being in opposition, the planet is now becoming extremely bright. Although opposition is a specific date, a month on either side is the best time to look at the planet using even a small telescope or a pair of binoculars.
A ‘Full’ Jupiter
Opposition means a full Jupiter because its sun-facing side is fully illuminated by the sun. Looking away from the sun into the outer solar system at night, we on Earth see Jupiter’s sun-facing side. It’s much like a full moon; 50% of the moon is always lit by the sun. Only our perspective of it changes.
Another consequence of Jupiter being in opposition is that it rises earlier. This week, it’s rising about two hours after sunset, but soon, it will appear in the east as the sun sets in the west, and set in the west as the sun rises in the east. So, as well as being big and bright, it will dominate all night. It will be highest in the sky just after midnight.
Jupiter takes 12 Earth years to orbit the sun. It orbits about 484 million miles (779 million kilometers) from the sun. Earth orbits 93 miles (150 million kilometers) from the sun. So Jupiter comes to opposition — as seen from Earth — once every 13 months, as Earth, traveling 12 times faster, catches up with Jupiter and then overtakes it.
Observing Jupiter And Its Moons
For amateur planetary astronomers, it is one of the astronomical highlights of the year. Its currently moving through the constellation of Taurus, shining just to the left of the red supergiant star Aldebaran — the “eye of the bull” — with the pretty open cluster, the Pleiades, just above the pair.
Any small telescope will get you a look at majestic Jupiter — including its pinkish cloud bands — but all you need is any pair of binoculars to see its four large moons, which are also at their biggest, brightest and best close to Jupiter’s opposition. The so-called Galilean moons (because they were first seen by Galileo Galilei using the first telescope) are Io, Europa, Ganymede and Callisto, which orbit Jupiter in the same plane, so they will be seen on either side of the planet.
‘Wandering Stars’
Planets were called “wandering stars” by ancient astronomers because they don’t appear to move through the night sky together as stars do. That’s because all planets are found on the ecliptic, the path the sun takes through the daytime sky.
The solar system is flat, and all the planets orbit the sun on the same plane. Consequently, you’ll only ever see planets on this ecliptic. This line in the sky stretches between east and west, though it passes overhead only from the equator. Planets rise in the east, move across the ecliptic in the southern sky, then set in the west.
Jupiter’s opposition on Dec. 7 is just the beginning of a terrific few months for planet-watchers. On Jan. 16, 2025, it’s the turn of Mars, which by mid-December will join Jupiter in the post-sunset night sky as a bright, red light shining at magnitude -1.4. Exactly a month later, Venus will reach its brightest in the evening sky, shining at a brilliant magnitude of -4.5.
Wishing you clear skies and wide eyes.
