October 18, 2017

Astro-Event: An Early Morning Planetary Ballet.

The month of July features something worth waking up early for. Remember those great pairings of Venus and Jupiter in the evening skies earlier this year? Well, they’re about to be replicated, with a few other objects to boot in the early morning skies.

Already, brilliant Venus has been dominating the view. Fresh off of its last transit of the Sun last month until 2117, the closest planet to Earth will now undergo a reversal of phases. Currently at a crescent phase 25% illuminated on July 10th, Venus will shrink from 38.3” in diameter down to 28” in size but 41% illumination by month’s end. In fact, Venus also reaches its greatest brilliancy for this current dawn apparition on July 10th, just a day before aphelion. At greatest illuminated extent on July 12th, this combines to have Venus shine at -4.7, bright enough to cast a shadow under dark skies. Venus is just one degree north of the +0.8 magnitude star Alpha Tauri (otherwise known as Aldebaran) and appears to be a Hyades star cluster imposter. In fact, the star Aldebaran is a “Hyades-fraud” as well, being 65 light years distant to the cluster’s 153.

Looking East at 4:30AM local on July 15th from mid-northern latitudes.

Just above the pair is the largest planet in our solar system, -2.0 magnitude Jupiter. All 3 lie within a 6 degree circle on the morning of the 11th, with the Pleiades star cluster riding high above. The waning crescent Moon will thread the gap between the Moon and the Pleiades on July 14th, and lie 4° degrees north of Venus on the 15th. The Moon will actually occult Jupiter for central Europe, northern Asia and the Far East centered on July 15th at 03:00 UTC; the rest of us will see a near miss. Can you see Jupiter near the Moon in the daytime? How ‘bout Venus? Use binocs to help with these feats of daytime planet observing. Another neat trick is to start tracking them into the daytime before sunrise with a telescope; just make sure that you have the Sun physically blocked from your telescopic vantage point!

All of these objects are well placed for northern hemisphere viewers and rise around 4 AM local time. Jupiter also has three interesting “double shadow transits” of the Jovian moons that are worth watching out for; one on July 14th at ~4:54AM EDT, one on July 21st ~6:53AM EDT, and another on July 28th at ~7:45AM EDT. Curiously (and conveniently!) these all occur on a Saturday morning and are well placed for North American observers; east coasters may have to utilize the aforementioned track “Jupiter into daylight” trick. Follow us on Twitter as these dates approach for all of the specifics.

After making a photogenic pass of the early morning planets, New Moon for July occurs on July 19th at 00:24UT. Sighting the Moon 20 to 16 hours before New may just be possible the morning for North American observers… the reverse will be true the evening of July 19th, when observers in the southern hemisphere may get their first look at a razor thin Moon for this lunation. This sighting also heralds the beginning of the Muslim month of Ramadan, which will start for 2012 either on July 19th, or 20th. The fasting month of Ramadan moves back by about 10-11 days every year on our Gregorian calendar, meaning that it’s been and will continue to occur in the heat of northern hemisphere summer for the next few years.

Finally, a fun possibility occurs any time the two brightest planets get together. If a bright pass of the International Space Station occurs just right, it’s possible to do a time exposure of the ISS and the two bright planets resembling an “emoticon” or :/ ! To our knowledge, such a creative shot has never been done… any takers?

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