SKY REPORTER: May 2012
by Steve Beyer on
Tuesday May first, sunrise is at 5:54 a.m. That evening the Sun located in the constellation Aries sets at 7:52.
On May 15th sunrise is at 5:38 and sunset occurs at 8:06 p.m.
The last day of the month the Sun is in Taurus, rising at 5:27 a.m. and setting at 8:20 that evening. During May the length of time the Sun is above the horizon each day increases by 54 minutes. The altitude of the Sun at solar noon, its highest daily elevation, ascends during May from 65 degrees of arc to 71 degrees.
Average overnight temperatures in Central Park rise from 49 degrees Fahrenheit on the first to 59 degrees on the last day of May.
Principal Phases of the Moon are:
|Full Moon||May 5|
|Last Quarter||May 12|
|New Moon||May 20|
|First Quarter||May 28|
During May Mercury is too close to the Sun’s direction for convenient observations.
On the other hand Venus is a brilliant sight in the western evening sky during most of the month. At the start of May it has visual magnitude -4.5, and angular separation from the Sun of 39 degrees of arc. Separation decreases rapidly from night to night. As the month progresses Venus will be lower in the west as it approaches the Sun’s direction. On June 5 it will be between Earth and Sun and observers using proper filters may see Venus appear as a black dot crossing the solar disk. This transit event has been long anticipated and a similar passage will not occur until December of the year 2117. Extreme care must be used during any direct solar observation to prevent blindness. Only those experienced in the use of high grade solar filters, or capable of safely projecting the Sun’s image onto a surface to view the transit indirectly, should make the attempt. Otherwise, it is advised to follow the event via internet or television.
During May, as Venus appears to move in the Sun’s direction, a telescope shows the Venusian crescent lengthening as the planet’s distance from us decreases from 41 million to 27 million miles. Venus’ apparent size thereby increases from 38 to 57 seconds of arc by the end of May.
Watching these changes can give a sense of that planet’s orbital motion. The apparent drop of Venus and its lengthening crescent are manifestations of harmony between gravity pulling Venus toward the Sun and orbital motion ensuring that planet maintains a safe solar distance. Orbital motion in our direction is evident as we see Venus appearing increasingly larger this month. On June 5th when that planet crosses in front of the solar disk, its distance from Earth will be at a minimum. In following weeks Venus will move away from the Sun’s direction and become visible in our pre-dawn skies.
Mars is in Leo during May, beginning the month near the waxing Moon, six degrees east of first magnitude Regulus. On May first the Red Planet is 87 million miles from earth with a visual magnitude of 0.0. Mars is in Leo throughout May and at month’s end will be 109 million miles from Earth, with slightly diminished brightness and a disk diameter of just eight arcseconds, too small to reveal surface details through a small telescope.
Jupiter sets at 8:31 p.m. at the start of May, 39 minutes after sunset. It will be hidden in the glow of evening twilight through this month, and on May 13 passes less than one degree of arc south of the solar disk. At the end of May the big planet rises 39 minutes before sunrise.
Saturn is in Virgo this month near first magnitude Spica, a white star that contrasts with Saturn’s slightly yellowish hue. The planet with the solar system’s most magnificent set of rings shines at magnitude 0.31, slightly brighter than Spica.
If you have never observed sixth magnitude Uranus or eighth magnitude Neptune, you’ll need binoculars or a telescope and look for them from a dark sky site. During May both planets are visible during several hours before dawn, with Uranus about 13 degrees south of second magnitude Algenib in Pegasus. Neptune is 34 degrees west of Uranus, in Aquarius about 10 degrees south of that constellation’s “Water Jar” asterism
The night of May fourth, the Moon is in Virgo forming a small triangle with Saturn and Spica.
Traditional names for May’s Full Moon, located in the constellation Libra on Saturday the fifth, include Full Flower Moon and Full Corn Planting Moon.
Our view into intergalactic space is blocked over a large swath of sky by vast clouds of dust permeating the Galaxy’s disk, a region highlighted by the Band of the Milky Way. However dust interference is at a minimum in a zone around the Galaxy’s poles, one of which is near the meridian high in our southern sky during spring evenings. As a result, under dark skies some members of the Virgo Supercluster may be seen even with binoculars, in Virgo and neighboring Leo. Edwin Hubble called this part of the sky the “Realm of the Nebulae”. Thanks in large part to his research the word nebulae, meaning mist in Latin, is no longer applied to what are now called galaxies, and is reserved for relatively small clouds of dust and gas within the spiral galaxies.
During early evening of Tuesday May 22 in fading twilight, a very thin crescent Moon is five degrees to the lower left of Venus. At 9:15 p.m. the Moon is five degrees above our west-northwest horizon.
On Monday May 28 the first quarter Moon is near Mars in Leo.
When the north pole of the Milky Way is near the meridian the Galactic equator nearly coincides with our horizon. Star light and glowing gas in the Band of the Milky Way then encircles us with a faint undulating glow extending about ten degrees above the horizon. To view this phenomenon you must be at a very dark site with an unobstructed horizon.
Cultures around the world tell many stories about the Milky Way. The name comes from a Greek legend about Hera goddess Queen of Olympus nursing the infant Hercules while she was asleep. Startled upon wakening, she pushed him aside with a resulting spray of milk that rose to create the Milky Way’s Band.
Khoisan people of Africa’s Kalahari have a legend about a time long ago, before stars had existed, when a young girl threw glowing embers from a fire into the sky to guide her way on a night trek to visit distant villages.
A Cherokee tale tells of a dog running off with a sack of cornmeal, spilling it along the way thereby forming stars of the Milky Way.
Oriental stories describe the Milky Way as the celestial barrier keeping a beautiful princess separated from her lover, a humble shepherd.
Under dark skies, binoculars and small telescopes can show a number of galaxies in the Virgo Supercluster, centered about 60 million light years from us. However to detect even a few galaxies in more remote superclusters, telescopes at least ten inches in diameter are usually needed. Several impressive galaxy clusters considerably more distant than those in Virgo are now in our evening sky.
The Coma Supercluster, 300 million light years from us, extends over a spherical region about 20 million light years in diameter and containing several thousand individual galaxies each with many billions of stars. This vast assembly is moving away from us at 4,100 miles per second and is within boundaries of the faint constellation Coma Berenices, just south of the Big Dipper’s handle.
Observations showed galaxies in the Coma Supercluster orbiting their mutual center much faster than expected. These extraordinary speeds revealed the presence of a mysterious essence called Dark Matter that permeates areas of galaxy clusters and induces their members to have such rapid orbital motion. It is believed Dark Matter occupies about 26% of the universe, with the visible galaxies of stars accounting for just four percent of everything now known to exist, with the remainder consisting of Dark Energy.
In constellation lore Coma Berenices represents long beautiful hair clipped and offered by Queen Berenices of Egypt as a sacrifice to the gods to insure her pharaoh husband’s safe return from battle.
Further east, in Corona Borealis several members of the Corona Supercluster of galaxies, may be glimpsed in moderate sized telescopes at a distance of one billion light years from the Milky Way Galaxy. This huge group with thousands of members was discovered by Edwin Hubble during the 1930’s. Speeds of recession from us were measured by his colleague at Mt. Wilson Observatory Milton Humason and are currently listed at about 13,300 miles per second. These astronomers provided vital evidence of the link between velocity and distance of galaxies, the basis of Hubble’s law that led to development of the Big Bang concept.
The constellation Corona Borealis features a small but attractive semi-circle of stars the brightest of which is second magnitude Alphecca. Corona has mythological association with the “Crown of Ariadne”, presented when she became queen of Naxos after being taken there by Theseus, whom she had helped escape from the labyrinth on Crete.