May Skies 2008

May: the second full month of Spring and the last month of the year in which the sun rises earlier each morning AND sets later each evening. Next month, June brings us summertime and, after June 21st, progressively shorter days once again.

April was unfortunately the last month to conveniently observe most Winter stars and constellations. However, on early May evenings we may still glimpse the most northerly Winter objects shortly after sunset. May is also the first month for convenient viewing of some summertime constellations and stars.

The Sun begins May in the Zodiac constellation of ARIES the Ram, where it remains until May 13th. On that date it enters TAURUS the Bull, where it remains until well into June.

May’s NEW MOON occurs on the morning of May 5th in ARIES. The 1st QUARTER MOON occurs before moonset the evening of May 11th – 12th in LEO.

May’s FULL MOON occurs at moonrise on the 19th. On that night, moonrise will be shortly after sunset and the moon rises in the head of the Zodiac constellation SCORPIUS.

Finally, the Moon reaches 3rd QUARTER phase late on the 27th in AQUARIUS.

The Evening Sky: Early May sunsets occur at about 7:05p.m., while sunset on the 31st is at 7:26p.m. Since morning sunrises also occur earlier each day, the duration of daylight progressively increases during May from 13hours, 43 minutes on May 1st to 14 hours, 5 minutes on May 31.

The Moon: The evening Moon will be seen near four naked-eye planets during May: MERCURY on the evening of the 6th. MARS on the evenings of the 9th& 10th. SATURN on the evening of the 12th, JUPITER overnight on May 23-24.

Moon & Prominent Stars: Very Thin Crescent Moon below the Pleiades star cluster (M45) in Taurus on the 5th.

Waxing Crescent Moon rises inside the Beehive star cluster (M44) in Cancer on the 10th. Waxing Moon is near Regulus in LEO the evening of the 12th. Waxing Moon is near Spica in VIRGO overnight May 16 – 17.

Recently Full Moon is near Antares in Scorpio overnight May 21 – 22. The day-old Moon will appear VERY low in the west after sunset on the 5th, setting at 7:55p.m. For a few minutes, observers with binoculars can see a rare alignment of the Moon, the Pleiades star cluster, and Mercury. Midway between Mercury and the Moon lie the Pleiades (the Seven Sisters cluster). On the next evening of the 6th, the Moon will stand above and slightly to the north (right) of Mercury.

Evening Planets: MERCURY, MARS, SATURN and JUPITER. VENUS remains near the Sun all month, and will not be visible during May. MERCURY begins May low in the Western sky after sunset and is found in TAURUS all month. For the first few days of May it lies very near the Pleiades star cluster. Mercury is usually very difficult to spot, but this month it stands highest above the horizon and also appears relatively very bright. We have often heard that stars twinkle, but planets do not. Because Mercury is very low in the sky, atmospheric dust and turbulence dim and bend its light back and forth, making the planet appear to twinkle like a star, and unlike our expectations for a planet!

Each evening until mid-month Mercury moves farther to the East away from the Sun and will appear higher in the sky. Binoculars will help you spot Mercury earliest after sunset for best viewing. As the stars become visible, Mercury will appear to also pass the Hyades star cluster and the 1st magnitude red giant star Aldebaran. By the 15th, Mercury will have nearly reached 2nd magnitude Alnath (aka Beta Tauri). After the 15th, the planet reverses course, rapidly approaches the Sun and will be effectively invisible by month end.

MARS begins May in GEMINI and moves into CANCER on the 5th, where it remains the rest of the month. The red planet which appeared so bright last December has faded significantly as its distance from Earth has increased. Now fainter than the nearby star POLLUX, Mars fades nearly to 2nd magnitude by month end.

Early in May Mars sets at 12:45a.m.. At month-end, Mars sets an hour earlier at 11:40p.m. The first few days of May, Mars lies a bit to the south along a line from Gemini’s two brightest stars Pollux (1st magnitude and the more southerly of the two) and Castor (the slightly fainter more northerly star).

Mars is easy to notice as it moves from evening to evening. By mid-month Mars is well into the zodiac constellation of Cancer, whose stars are much fainter than Gemini’s. Mars’ path carries it through the rich “Beehive” star cluster (M44) during May 21-23, making for superb binocular or telescope viewing!

The crescent Moon will be near Castor, Pollux and Mars on the evenings of May 9th (below Mars) and the 10th, (above the planet). SATURN remains in LEO all month, each night standing quite near the 1st magnitude star Regulus. The ringed planet has just finished its annual “retrograde” (westward) motion in the sky for 2008 and each night will slowly move eastward. On the 1st, Saturn sets later than 2:30a..m., while on the 31st, it will set just before 12:45a.m. This month there will be plenty of time to observe Saturn with a small telescope at home or at one of the Valley’s Public Star Parties (see below). Saturn’s rings, now tilted nearly in line with the Earth, make a fine sight in even small telescopes, and Saturn’s largest satellite, Titan, should be easily visible orbiting well outside the rings. If you catch a telescopic view, note the shadow of the planet clearly visible on the rings, and the shadow of the rings visible across the width of the planet!

On the evening of May 12th, the Moon forms a wide triangle below Saturn and Regulus. JUPITER begins the month as a Morning Planet, but rises before midnight by month end.
Remaining in Sagittarius all month, Jupiter is visible from its rise time until sunrise. A good pair of binoculars will show Jupiter’s four brightest satellites: Io, Europa, Ganymede, and Callisto when most distant from the planet. Even a very small telescope will show them any night!

These moons are also known as the “Galilean” satellites in honor of their discoverer, Galileo. Since Jupiter’s axis is not significantly tilted, its equatorial cloud bands and the famous Great Red Spot regions show distinctly each night. The newsstand magazines “Sky and Telescope” and “Astronomy” contain diagrams showing where the satellites are located each evening for easy identification. These magazines’ online websites also feature interactive simulations of the Galilean moons for any time of the year.

What Else to See? Winter’s prominent constellations of Orion, Canis Major, Canis Minor and Auriga are no longer visible in May. Even Leo the lion now appears in the Western sky in May. However, mid-Spring brings us excellent views of the Spring and early summer constellations of: Virgo, Corvus, Bootes, and Hercules in the Eastern sky at dusk. And Ursa Major (the familiar “Big Dipper”) which was low in the sky earlier in the year, now stands above the North Star Polaris and highest in the sky on May evenings.

After about 9:30p.m. if you look low in the East and Northeast, the distinctive Summer constellations Vega, Cygnus, and Aquila can be seen on the rise. Their bright stars Vega, Deneb, and Altair (which make up the “Summer Triangle” brightest stars of summertime) are the keys to finding these constellations. At this time low in the Southeast Scorpio is starting to rise, led by the scorpion’s three “head” stars and the bright red supergiant star Antares a bit below.

At midnight, these stars and constellations will all be high in the eastern sky to signal the approach of summer.

Observers with binoculars or small telescopes can watch the Moon either eclipse or approach very close to stars of 6th magnitude or brighter on the evenings of May 9th, 10th, and 19th. Approximate event times are given here.

The Morning Sky: The Sun rises at 5:42 on May 1st. On the 31st, sunrise occurs at 5:23a.m. The waning MOON appears in morning May skies through the 5th and again is easily visible during morning hours from about the 13th through the end of the month. The morning Moon is seen near: SATURN on the morning of May 12th. JUPITER on the morning of the 24th.
The Waning Gibbous Moon stands near Antares in SCORPIO on the mornings of the 20th & 21st. Morning Planets: VENUS and JUPITER. VENUS is on the far side of the Sun all month and too near the Sun to observe.

JUPITER is a Morning Planet for only part of May. After the first week of May, Jupiter rises before midnight and technically becomes an Evening Planet. However, Jupiter, now in Sagittarius, all month is best positioned for morning viewing.

What Else to See? Observers with binoculars or small telescopes can watch the Moon either eclipse or approach very close to stars of 6th magnitude or brighter on the mornings of May 13th, 17th, 24th and 26th. Specific times for these events are given on Lunar Occulations for May 2008.

Good Luck Observing!

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