This is the Skywatch Line for Monday and Tuesday, August 8th and 9th.
The Sun sets at 8:06 PM; night falls at 9:58. Dawn breaks at 4:04 AM and ends with the Sun rising at 5:55.
The evening sky contains a brilliant Moon and five naked eye planets. The six-day-old Moon is already risen, and, by civil dusk, is high in the southwestern sky. In Virgo, Monday’s Moon blazes at minus 8.7 magnitude and appears a third illuminated; Tuesday, the Moon, in Libra, is brighter still and about 43 percent illuminated. On both nights, the Moon sets by 11:38 PM.
Venus, the brightest naked eye planet, is also the hardest to spot. It blazes at minus 4 magnitude and appears almost “full” in our binoculars and telescopes. However, it lies almost three degrees above the western horizon; the observer must have an unobstructed view. Venus sets at 8:56 PM. Easier Mercury shares Leo with Venus and is dimmer, at zero magnitude, and appears about two-thirds lit. But it is higher, about 5 degrees above the horizon, and nine degrees West of Venus and acts as guide. Mercury sets at 9:06 PM.
Jupiter, also in Leo, is much easier to find. It is about ten degrees above the western horizon and glows at minus 1.7 magnitude. It may be the first planet to appear amid the dimming sky. Binoculars and telescopes clearly show it as a planet, with tiny moons near it. However, it is becoming too low to observe any surface features. Jupiter sets at 9:38 PM.
But, all the action is not in the deepening western sky. The celestial triangle of Saturn, Mars and Antares continues to shrink and attract attention in the South. Mars, now in Scorpius, shines at minus 0.6 magnitude, is about 22 degrees above the horizon and appears about 86 percent illuminated in our telescopes. The Red Planet continues its eastward travels and is about eight-and-a-half degrees from Saturn. It is receding from our view and daily grows dimmer and smaller in our instruments. Mars sets after midnight.
Saturn, in Ophiuchus, glows at zero magnitude, but is still a stunning sight in our telescopes; some of its 62 satellites can be seen in backyard telescopes. The Ringed Planet continues to slowly retrograde – heading West. On August 23rd, Saturn, Mars and Antares will line up to form a dramatic conjunction, visible to the naked eye. Mars, Saturn and the red star Antares all set by 1 AM.
While everyone is looking at Mars and Saturn, Neptune was quietly rising in Aquarius at 9:03 PM, and remains up the rest of the night. This distant solar system member is at magnitude 7.8. These nights, it lies near the star Hydor (Lambda Aquarii) which shines at third magnitude. Detailed star charts help find this blue-green dot amid similar looking stars.
Uranus rises in Pisces at 11:34 PM and is best observed at 5:13 AM. It appears brighter at magnitude 5.8 and is 3.6 arc-seconds in size. It, too, is a blue-green dot amid similar stars and also requires a detailed star map.