That Bright Star In The East Isn't A Star At All

Has something bright in the Eastern sky before dawn caught your eye? Recently, has it been shining brighter, rising a couple of hours after dark, and remaining visible until sunrise? You might think it's a star at first glance, but after watching a while, you can see that it doesn't twinkle nor move in a fixed position like stars are known to do. Instead, this bright phenomenon is Jupiter as its orbit and Earth's orbit around the Sun bring the planets closer together.

One of the characteristics of the planet Jupiter is that it takes much longer than Earth to complete one orbit around the Sun — 12 Earth years, in fact. As a result, the "king of planets" reaches the point of opposition every 13 months. Astronomers use the term "opposition" to describe the moment at which an outer planet aligns with the Sun as Earth moves directly in between them. From our ground view, the outer planet appears to be on the opposite side of the sky as the Sun. When this happens with Jupiter, the side of the planet facing the Sun is completely illuminated, which is why it appears so bright in the evening and early morning skies. Plus, the opposition allows us to see all of that side of the planet — kind of like a full moon.

Since Jupiter is the largest planet in our solar system — 11 times the size of Earth — you should be able to see it well with a decent-sized telescope, including its Great Red Spot, which is actually a storm that has been raging on the planet for centuries. It only takes about 10 hours for the planet to complete a turn on its axis, so even if you can't see the spot early in the night, you'll be able to see it at some point with some patience. If you only have a small telescope or a pair of binoculars, you should still be able to see the cloudy, dark belts that wrap around the planet and straddle its equator, as well as some of its moons.

Of the planets known to have satellites, Jupiter has more than you think — 95 have officially been recognized so far. During the planet's opposition, though, you'll be able to see its four largest moons, which are called the Galilean moons because they were discoveries of Galileo Galilei in 1610. Through binoculars or a small telescope, they look like four dots of light that extend beyond Jupiter in a diagonal line — as if they are bisecting the planet. Sometimes, though, only three of them are visible. When that happens, the fourth satellite could be hidden behind the massive ball of gas. On the other hand, it might be passing in front of Jupiter, where it's too tiny to notice. In that case, you might get lucky and see its shadow on the planet during this transit if your equipment is good enough.