Jupiter & Mercury Conjunction

This weekend one can observe Mercury and Jupiter conjunction, Mars, Saturn and the ice giant planets Uranus and Neptune. Read on to learn when to view each planet.

Mercury will still be visible this week, but it will be tough to see it from the Northern Hemisphere because it will be barely above the west-south western horizon after sunset. The elusive planet will set at about 7 pm local time — 45 minutes after the sun. Because Mercury is on the far side of the sun right now, its appearance in a telescope will be a nearly fully illuminated disk. For eye safety, be sure to wait until the sun has vanished completely before using binoculars or a telescope on Mercury.

For an added bonus, and some help to find Mercury, the bright planet Jupiter will pass near Mercury later this week. On Saturday, October 27, Jupiter will sit only 3.5 finger widths directly above Mercury. The two planets will be slightly closer together on Sunday evening, and then start drawing apart next week. Jupiter will set in the west-southwest before 7:30 pm local time. After this week, we’ll have to wait until next May before the mighty planet will return to the evening sky.

Reddish Mars and dimmer, yellow-tinted Saturn will remain visible in the southern evening sky this week. As soon as the sky becomes dark enough to reveal them, both planets will be located about two fist diameters above the horizon, with Mars located 35° to the left of Saturn. Mars will set in the west at about 1:15 am local time. It’s still well worth looking at, even in a small telescope. Try to see a small white oval near the top of its disk.

Saturn will set before 10 pm local time. Once the sky darkens, even a small telescope should be able to show you some of Saturn’s largest moons, especially its largest satellite, Titan. Using a clock’s dial analogy, Titan will move counter-clockwise over the course of this week — starting from a position at 9 o’clock to the left of Saturn tonight, and ending next Sunday at 4 o’clock to the lower right of Saturn. Remember that your telescope might flip and/or invert the view. Use the moon to find out how your telescope changes things and keep a note of it, since that will always be the case.

This autumn presents an ideal time to peruse the ice giant planets Uranus and Neptune because they will be conveniently placed for evening observing and also bigger and brighter than normal because Earth is roughly between them and the sun right now, minimizing our distance from those planets.

Distant Neptune continues to be visible from evening until about 3 am local time. Using a decent quality telescope you can see the very blue, magnitude 7.8 planet among the dim stars of Aquarius  — sitting roughly midway between the modestly bright star Phi (φ) Aquarii and the brighter star Hydor (Lambda Aquarii). Neptune will highest in the sky and best viewing conditions at about 10 pm local time. The bright moonlight will make seeing the planet harder this week.

On Tuesday, the blue-green planet Uranus will reach opposition. At that time, it will be visible all night and at its peak brightness (magnitude 5.7) and size for this year. You can see it without optical aid under very dark skies, but binoculars and telescopes will work better. After mid-evening, Uranus will be high enough in the eastern sky to see it clearly. Uranus is so far from Earth all the time that its appearance at opposition is little better than it is on evenings within a month of opposition. The planet will be 2.8 trillion km from us this week. Its reflected sunlight will require more than 2.5 hours to reach our eyes on Earth!

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