So far, the planet that has dominated our morning sky has been bright Venus, which is visible in the low northeast sky at dawn — about 90 minutes before sunrise.
But before Venus rises, Jupiter dominates the sky from evening, dazzling more than anything but the moon.
This week, the king of the planets will rise around 9:45pm local time – speaking of the moon – and later on Sunday (August 14), if you face east shortly after 10:30pm, you’ll be A waning gibbous moon is seen, three days later, just over 5 degrees to the right of Jupiter.
Your clenched fist is about 10 degrees wider than the length of your arm, so on Sunday night, just over “half a fist” will separate Jupiter from the Moon.
related: Jupiter: A Guide to the Largest Planet in the Solar System
Jupiter and the moon will remain visible throughout the night, peaking south just before 4 a.m. at more than half the distance from the horizon to the point directly above (the zenith).
Also, there was a noticeable change in the direction the pair had previously taken; Jupiter appeared to glow directly above the moon as they crossed the southern meridian in the early hours of the morning. And the distance between them will also shrink to 3 degrees, and they will look closer.
The opposition, when it’s closest to Earth and in the sky all night – from sunset to sunrise – is just over six weeks away from September 26. Also on Sunday, Saturn will reach its own opposite. It is located 46 degrees west (right) of Jupiter. Since your clenched fist is roughly 10 degrees the length of your arm, Saturn and Jupiter are currently about 4.5 “fists” apart.
Dance of the Moon
Don’t forget Jupiter’s four main moons, which were discovered by Galileo 412 years ago. They are a constant pleasure for amateur astronomers and can be seen in any telescope or even binoculars. They orbit Jupiter so fast (1.68 days for Io and 16.7 days for Callisto) that they change their appearance hour by hour, night by night.
For example, if you train a telescope on Jupiter on a Sunday night, initially, you’ll see one moon (Io) on one side of Jupiter and two (Ganymede and Callisto) on the other. But at 11:28 p.m. ET (0328 GMT Monday, August 15), a fourth moon (Europa) will emerge from behind Jupiter’s disk, joining Ganymede and Callisto.
Then at 2:15 a.m. ET (0615 GMT) on Monday, Io will disappear as it is obscured by Jupiter’s shadow. Io will pass behind Jupiter shortly thereafter, but will reappear more than three hours later. Those in the central and western states where the sky is still dark will be able to see all four moons lined up on Jupiter’s side.
Size (and distance) matters
Finally, when you look at the Moon and Jupiter on Sunday night, try to be aware of the difference in their respective sizes and distances.
Of course, the Moon is more than 9 magnitudes brighter than Jupiter. The brightness ratio is 4,370 to 1.
But the Moon is also much smaller than Jupiter. In fact, our natural satellite is 2,158 miles (3,474 kilometers) in diameter, while Jupiter is 88,846 miles (142,984 kilometers) in diameter.
What makes the moon appear so huge and bright is its distance. On Sunday night, the moon was 232,300 miles (373,600 kilometers) from Earth. But Jupiter’s distance would be increased by a factor of 1,681: 390.6 million miles (628.5 million kilometers).
The fact that the Moon is so close to us compared to Jupiter means that it is moving through the sky much faster than the larger planet, at about its own apparent diameter per hour. So, that’s why when they rise in the southern sky before dawn, the moon will appear closer to Jupiter than when they rose in the east a few hours ago.
Joe Rao is a lecturer and guest lecturer at NYU Hayden Planetarium (opens in new tab). He writes about astronomy journal of natural history (opens in new tab)This Farmer’s Almanac (opens in new tab) and other publications.Follow us on Twitter @Spacedotcom (opens in new tab) and on Facebook (opens in new tab).