This Week’s Sky at a Glance, July 7 – 14 ~by Curt Nason
Saturn currently sits above the Teapot asterism of Sagittarius the Archer. Sagittarius is an old constellation of a centaur with a bow and arrow aiming toward Scorpius the Scorpion. If he tries to shoot Aquila the Eagle above, chances are the arrow will be deflected by a shield.
Scutum the Shield is a relatively new constellation, created by the Polish astronomer Johannes Hevelius in the late 17th century. It commemorates the Polish king John Sobieski III, who defended his country against the Turks. Originally named Scutum Sobiescianum (Sobieski’s Shield) it is generally just called the Shield. Seeing it can be difficult, for its main stars are dim and shielded within the Milky Way. One way to locate it is to find its most prominent deep sky object, the Wild Duck Cluster or M11.
Find the bright star Altair in the head of Aquila and then identify the wings and tail of the eagle. Binoculars will reveal a string of stars leading from the tail to M11 at the top of the shield. The rich Wild Duck Cluster looks good in binoculars and great in a scope, and an imaginative observer can see a V-shape or maybe two. A week ago the bottom of the shield drew the attention of astronomers with the appearance of a nova.
When an average size star like our Sun runs out of fuel it collapses to an earth-sized white dwarf star. If the white dwarf has a binary companion it can draw hydrogen gas – fuel for fusion reactions – away from the companion. If enough collects on the surface of the white dwarf the hydrogen can flash in a thermonuclear explosion thousands of times brighter than the Sun. Nova Scuti 2018 is bright enough to be seen in a backyard telescope.
This Week in the Solar System
Saturday’s sunrise in Moncton is at 5:35 am and sunset will occur at 9:11 pm, giving 15 hours, 36 minutes of daylight (5:44 am and 9:13 pm in Saint John). Next Saturday the Sun will rise at 5:41 am and set at 9:07 pm, giving 15 hours, 26 minutes of daylight (5:49 am and 9:09 pm in Saint John).
The Moon is new just before midnight Thursday evening and reaches perigee before sunrise on Friday, resulting in very high tides next weekend. The slender crescent passes just above Mercury next Saturday evening, about 15 degrees to the lower right of Venus. Venus is near Regulus this Monday, and Mercury reaches its greatest elongation from the Sun on Wednesday. Jupiter is stationary on Wednesday, resuming its normal eastward motion against the stars until next spring. Saturn continues to give great views of its rings in a telescope. Ever-brightening Mars rises by 10:30 pm late in the week and might look more like a pumpkin while it remains wrapped in a global dust storm.
The Saint John Astronomy Club meets in the Rockwood Park Interpretation Centre on Saturday, July 7 at 7 pm. All are welcome. The annual RASC NB star party at Mount Carleton Provincial Park occurs July 13-14, taking advantage of very dark and moonless skies.
Questions? Contact Curt Nason.