Goodbye summer, hello Jupiter.
Saturn and Mars hang low in the southwestern sky as evening twilight begins to fade. An hour after sunset, the ringed planet is a little more than 10 degrees up while Mars is only slightly higher. This week Mars approaches and then passes 2.4-magnitude star, Delta (δ) Scorpii. The two will be closest Wednesday evening (September 17) and separated by only ½ degree. Also having a stellar close encounter is distant Neptune, which lies roughly ½ degree north of the 4.8-magnitude star, Sigma Aquarii, all week. That should make finding the 7.8-magnitude planet a little easier. Sigma and Neptune are at their highest around midnight.
Meanwhile, the morning sky belongs to Jupiter, which adds extra lustre to a scene adorned with the bright stars of winter. Big Jup rises at around 3:20 a.m., local daylight time, and is 20 degrees high at the start of astronomical twilight. Last up is brilliant Venus, which clears the eastern horizon a little after 6 a.m. — less than an hour ahead of the Sun.
Last-quarter Moon occurs at 10:05 p.m., EDT, tonight. The Moon, however, won’t rise until around midnight. This is a good time of year to view this phase as the Moon rides high along the ecliptic in Taurus.
In the early morning hours, a thin crescent Moon lies below Jupiter in the dawn sky. The pair are less than six degrees apart and should make for a fine naked-eye sight. As a bonus, check for earthshine on the dark portion of the lunar disc.
The autumn equinox occurs today at 10:29 p.m., EDT (7:29 p.m., PDT), when the Sun crosses the celestial equator. Time to bid farewell to summer and welcome autumn. From this point onward, we’ll start to get more night than day. As a stargazer, I tend to regard this as a good thing.
Jupiter is often called the King of Planets, and at the moment it’s easily the finest telescopic planet in the sky. The September 19 – 21 weekend is really the first one that allows productive observing. Of course, the enemy of detailed views is atmospheric seeing — the image-blurring effect caused by the air above us. The nearer an object is to the horizon, generally the worse the seeing.
This weekend Jupiter is nearly 30 degrees up by the time the sky starts to noticably brighten. That’s high enough that steady seeing conditions are possible — and that means Jupiter could be a pleasing sight at medium- or high-magnifications. With its numerous belts, Great Red Spot, and four bright moons, Jupiter is arguably the most interesting telescopic planet. Set your alarm for an early morning wake-up call this weekend and have a look!
For more on what the plant has to offer, be sure to check out our Guide to Observing Jupiter.
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