Sacred monuments

Innumerable medieval Christian sites were constructed to include both religious and astronomically significant events. Many churches were aligned in an east-west direction with the altar in the east and facing west into the rising sun, the direction from which it was commonly believed the Second Coming would occur. A number of churches, more than 300 in England alone, were aligned to the point of sunrise on the birthday of the saint to whom they were dedicated.

An ancient church, St. Piran’s in Cornwall, is aligned with an even earlier marker indicating the point of the sunrise on Aug. 15 in the seventh century, a date one source associates with the saint. Charlemagne built a chapel in Aachen, Germany, so that on the day of the summer solstice, a ray of light passed through a chapel window and illuminated a golden ball representing the heavenly Jerusalem. Not a modest man, Charlemagne also had the light from the summer solstice shine through another window, illuminating his crown and face as he sat on his throne! At Elm in Switzerland, a natural rock tunnel cuts 60 feet through the Tschingelhorn peak that towers over the town. Probably by chance, sunlight at the time of the spring equinox shines through the tunnel. Early Christians took full advantage of the fact and built their church so its tower is illuminated with sunlight from the tunnel on that important religious and astronomical date.

Focus on the planets

Mercury may be glimpsed very low in the east about a half-hour before sunrise during the first two weeks of May. The best opportunity comes on the morning of May 6 when Mercury lies just to the lower right of the thin crescent Moon.

Venus starts the month very low in the northwest and sets about a half-hour after sunset, affording little chance to view the planet. By month’s end, Venus’ altitude doubles and it remains in view for an hour and a half after sunset.

Mars rises in the southeast about 3 a.m. and may be viewed at morning twilight by means of a small telescope. Mars is growing in apparent size and brightness as the faster Earth catches up with it, but it won’t be until early fall before it yields up details of its surface.

Jupiter may be found high on the southeastern horizon about an hour after sunset and provides excellent viewing until after midnight. Telescopes will reveal surface features such as the equatorial bands and Great Red Spot, while the movements of the four major Jovian moons are sure to fascinate both seasoned and novice planet watchers.

Saturn is located about midway up on the western horizon at evening twilight. The twins Castor and Pollux are to the immediate upper right of the ringed planet.

Uranus is in the same neighborhood as Mars all month. The best opportunity to spot Uranus comes on May 15 when Uranus is less than two degrees directly above the Red Planet.

Neptune lies among the stars of Capricornus, far to the right of Uranus, in May. Next month Sky & Telescope will publish finder charts to help locate far distant and elusive Neptune and Uranus.

Pluto is essentially a lost cause except to experienced watchers with near-professional equipment.

May events

5 The Eta Aquarid meteor shower, which originates from the debris trail of Halley’s comet, peaks tonight. Look for an hourly rate of 35 to 60 swift moving meteors coming from the vicinity of Mars in the constellation of Aquarius. The waning crescent moon will not be a factor, so this should be a good year to see this major meteor shower.

8 New moon, 4:48 a.m. Venus lies to the moon’s far left while the Pleiades are situated immediately to its upper left.

13 The sun enters the constellation of Taurus the Bull on the ecliptic.

14 The moon is at apogee, or farthest distance from the Earth, today.

15 Whitsun, the seventh Sunday after Easter. Tonight is the best opportunity to spot Uranus as it lies directly above Mars during the early morning hours.

16 Moon in first quarter, 4:58 a.m.

19 The moon and Jupiter appear extremely close together tonight although Jupiter is 1,800 times more distant.

20 The sun enters the astrological sign of Gemini but astronomically is still in Taurus. Look for the star Spica to the immediate right of the moon an hour after sunset.

23 Full moon, 4:20 p.m. The full moon of May is called the Planting Moon, Flower Moon or Milk Moon.

24 The moon covers, or occults, the bright star Antares as seen from much of North America during the early morning hours.

26 Moon at perigee, or closest approach to Earth, today.

30 Moon in last quarter, 7:48 a.m. This is the second time for this lunar phase in May.

31 Mars hangs on the upper tip of the moon at dawn. The lone star to the moon’s far lower.

Clair Wood taught physics and chemistry for more than a decade at Eastern Maine Technical College in Bangor. Starting May 30, his monthly column and chart will run on Mondays.