Planets in August

Planets in August

(1976)

Located in the constellation Taurus, the largest planet raises shortly before midnight during most of August. Its diameter increases from 35.2 to 38.5 seconds of arc, while its distance from Earth changes from 485 million miles on August 1 to 443 million miles by month’s end.

For any observer, beginning or experienced, Jupiter’s moon rank among the most fascinating phenomena of any of the sky. One reason for this is that the line-up of satellites changes from night to night, giving telescopic observers an excellent chance to actually watch astronomy in motion. In addition to the motion of four major moons, an added attraction is provided by the satellite’s shadows which frequently cross the Jovian disk. The combination of a satellite’s motion and Jupiter’s own rotation will show the shadow creeping across the cloud bands. This month Astronomy resumes its “Satellites of Jupiter” and “Satellite Shadows” charts, both of which can be found in Sky Almanac.

Jupiter will shine near magnitude-2 throughout August. Watch Jupiter and the last quarter moon on the night of August 17-18; the moon will slowly creep up on the planet, and the two will be separated by only one degree of arc at 5 a.m. EDT. Those watching the event from southern South America will see an occultation.

Space Lady. Illustration by Elena

Mercury

The difficulties inherent in seeing Mercury are well-known to potential observers, many of whom have probably failed to glimpse the little planet even when conditions seemed excellent. The situation is not helped by circumstances such as those that prevail this month, when Mercury, despite its being at greatest eastern elongation on the 26th, will remain beyond the reach of all but the most efficient planet watchers. Because the ecliptic is very low above the western horizon in August. Mercury does not stand high enough to be easily glimpsed: it can easily be blotted out by horizon haze or obscuring trees or buildings. A much better opportunity for observing Mercury will come at October’s greatest western elongation.

Venus

During August, Venus won’t get much higher above the horizon than Mercury will – only about eight degrees. Setting within an hour of the sun, Venus should be easier to see than its tiny inner neighbor, since its magnitude is – 3.3. For the rest of this year, the planet will remain an evening star, slowly brightening and gradually becoming more dominant in the western sky.

Mars

Observation of the red planet in 1976 has effectively ended, for Mars is now so faint (magnitude + 1.9) and low in the West at sunset that it is hard to spot. Its distance from Earth increases from 218 to 228 million miles; the planet moves from Leo to Virgo on August 12. Lack of a prominent guide star will make identification difficult for those who are unsure of their constellations. Mars’ visual appearance is, in fact, in direct inverse proportion to the interest evoked by the Viking mission to that planet.

Saturn

Too close to the sun to be observed for most of the month, Saturn might be glimpsed be determined observers during the last mornings of August when, located in Cancer, it rises shortly before the Sun.