Appearance of Arcturus brings warm weather

Posted April 29, 2010, at 8:19 p.m.

Bootes the Herdsman also was known in antiquity as the “Driver of the Bear” because the constellation trails that of Ursa Major, the Great Bear. Its relatively undistinguished stars resemble a kite in form, but Bootes is one of the oldest known constellations due to one star, Arcturus. The appearance of Arcturus in late spring is a sure sign of warm weather to come. Arcturus is a red giant that is 20 times larger than the sun and, at 35 light-years distant, is the closest of any of the stellar giants to Earth making it the third-brightest star in the heavens. Arcturus was the first star, other than the sun, to be seen in full daylight. Jean Morin did this in 1635 with a telescope that revealed Arcturus against a deep blue sky. It has one other distinguishing feature in that, traveling at 95 miles per second, it is one of the fastest stars in our vicinity. In a 70-year period, Arcturus moves against the night sky by about one-tenth of the full moon’s diameter.

Focus on the planets

Mercury is all but invisible very low on the eastern horizon in the bright morning twilight. Viewers may spot it late in the month with the aid of binoculars.

Venus is the brightest object in the west after sunset. In spite of its brightness, Venus is small and gibbous, offering little detail for viewers with a telescope.

Mars rises in the west at dusk and remains up until after midnight. Mars is now about 130 million miles from Earth and offers little to see even by telescope. On May 19, Mars is just above a fat crescent moon and, on May 31, is situated close to the blue-white star Regulus.

Jupiter peeks above the eastern horizon around dawn early in the month but is up by 3 a.m. by month’s end. Look for the moons of Jupiter as bright spots on either side or in front of the planet if you possess a moderately strong telescope.

Saturn rises in the south at sunset, is highest around midnight, and sets well before dawn. Saturn’s rings are a disappointment, appearing as a narrow band bisecting the planet. The rings are at their minimum for the year in May, and one report says this will be the last opportunity for 15 years to see them this narrow.

Uranus is in the same binocular field as Jupiter but a small telescope will be needed to observe its small blue-green disk.

Neptune is low on the pre-dawn southeastern horizon where it can be spotted with powerful binoculars. On a historical note, Neptune is in the same spot in western Aquarius where Johann Galle discovered it on Sept. 23, 1846. It has made one orbit of the sun since Galle spotted it.

May events

1 Sunrise, 5:26 a.m.; sunset, 7:40 p.m. May Day or Beltane marking the midpoint between the spring equinox and summer solstice. Venus lies near orange Aldebaran low in the west during the early evening hours.

6 This is the peak night for the Eta Aquarid meteor shower. Originating from Aquarius, the moon will wash out the fainter meteorites leaving a density of about 20 meteors per hour. The best viewing time will be from 2 to 4 a.m. The moon is at apogee or farthest distance from Earth.

9 Look toward the eastern horizon at dawn for Jupiter with the moon directly above it.

14 New moon, 9:05 p.m. The sun enters Taurus on the ecliptic.

15 Venus is well up on the western horizon about an hour after sunset with the thin crescent moon to its lower right. Red Betelgeuse is far to the lower left of Venus.

20 Moon in first quarter, 7:43 p.m. The moon is at perigee or nearest approach to Earth today.

21 The sun enters the astrological sign of Gemini but astronomically is still in Taurus.

22 Saturn, resembling a bright golden star, is situated above the moon in the south at nightfall.

26 Scan low on the eastern horizon with binoculars about a half-hour before sunrise to spot Mercury resembling a bright star.

27 Full moon, 7:07 p.m. The full moon of May has several names including the Flower Moon, Milk Moon, Planting Moon and Grass Moon.

31 Sunrise, 4:53 a.m.; sunset, 8:13 p.m.

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