September 7 – 20, 2015
Awareness of the cosmos beyond our sunlit Earth comes most easily when the broad, soft blue atmosphere of daytime goes dark. Astronomers sleep during daylight hours and open their observatory domes as skies darken and the lights from our solar system and outer space reach through our atmosphere. As we near the autumnal equinox, night meets day at times we might normally be awake.
Night prevails for around 11 hours today and more than 12 hours by month’s end. With sunset at 7:19 this evening and 6:56 on the 20th, children may now enjoy the stars of summer’s end in the west and autumn’s rising stars in the east before bedtime. For early risers, it’s disorienting to be greeted by dawn as late — and soon to be later — than 6 a.m.; sunrise not until around 6:30.
For a most inspiring way to begin the day, even from an east-facing window, set your eyes on phenomenally bright planet Venus from about 4:30 a.m. – 6 a.m. Venus is almost at its brightest for this Morning Star appearance. Tomorrow morning, the 8th, its magnitude is -4.48m, greater than at its most stunning as Evening Star in July. From the 16th – 26th the Morning Star’s magnitude will be -4.54. Sirius the Dog Star (-1.47m) twinkles to the right of Venus in the southeast. (Note that the larger the value of the number the less luminous the object.)
To see Mars, the red planet, to the left of Venus, best to look by 5:30, because Mars (1.78m) is dim by comparison and easily washed out by the dawning light of the approaching sun. On Thursday the 10th a thin crescent moon (-9.77m) will appear below Venus, between the Morning Star and Mars. On the 11th, a more delicate (-8.79m) waning crescent appears to the right of Regulus (1.34m), the heart star of Leo the Lion. On this morning, planet Jupiter (-1.7m) rises an hour before sunrise, and so should be visible above the eastern horizon by 6 a.m., depending on your skyline. Look below and to the left of Venus for Jupiter. Mars will most likely have vanished into the sunrise glow. Jupiter climbs higher, becoming more prominent, each successive morning.
New Moon occurs at 2:41 a.m. on the 13th.
Enjoy a visual lullaby, whenever your bedtime, by observing the three bright stars that form the Summer Triangle. At dusk, they appear overhead, towards the south, and then high in the southwest before setting in the west during the wee hours. Also, autumn’s Great Square is completely above the horizon in the east at nightfall. The Square delineates the body of Pegasus the Winged Horse; it can be seen following the Summer Triangle all night.
Best of all, through the long night in dark sky locations that are free of artificial light, trace the arch of starlight, the Milky Way, from north to south through the Summer Triangle. When stargazing, it makes all the difference to allow 20 minutes for our eyes to adjust to the darkness.
Resources:
https://www.nasa.gov/mission_pages/newhorizons/main/index.html
