Sunrise and Sunset Times for June 2010

DAYLENGTH
Earliest sunrises for the year occur June 11-16. Latest sunsets are delayed until June 25-30. June 21 provides the longest period of daylight for the year--14hours, 52minutes from sunrise to sunset on the summer solstice. Twilight contributes even more light to the long, summer days. During the summer months both morning and evening twilight linger much longer than the rest of the year. Notice that darkness does not overtake the western sky until after 10:30pm. That’s nearly two hours of fading light after sunset. The long summer twilight begins to shorten by the end of June, but it will be mid-August before the skies darken before 10:00pm. (The time of sunrise and sunset assumes a flat horizon. Actual time may vary depending upon the landscape.)

MOON HAPPENINGS
June begins with a waning third quarter moon rising after midnight. A new moon occurs June 12. The waxing crescent moon reappears low in the western sky on the evening of June 14 (See Venus). The moon appears farther east each evening because it rises from 30-70 minutes later each day. On June 18 the first quarter moon is high in the sky at dusk with Mars and Regulus (Leo) to the west and Saturn above. On June 20 the moon appears near Spica (Virgo). On June 23 look for it low in the southern sky about three degrees from Antares (Scorpius). A full moon rises June 26 soon after nautical twilight begins. (The time of moonrise and moonset assumes a flat horizon. Actual time may vary depending upon the landscape.)

SUMMER SOLSTICE
The sun’s position in the sky continues to progress northward until 5:28am MDT on June 21. That date and time marks the summer solstice. Those in Todos Santos at the tip of Baja, in Mazatlan on the west coast of Mexico, and in Havana, Cuba, will see the sun overhead at noon on this day. These locations sit very near the Tropic of Cancer at 23.5 degrees North latitude. The angle of the earth’s tilt is 23.5 degrees which places the Tropic of Cancer directly under the sun’s rays at the summer solstice.

As the earth rounds the elliptical end of its orbit, its motion in space begins to parallel the apparent path of the sun across the sky (the ecliptic). The result is little change in the times of sunrise and sunset during June. Earth’s rotation explains why earliest sunrise and latest sunset do not occur on the solstice when the longest period of daylight occurs. The earth rotates on its axis towards the east which is the same direction it travels in its orbit around the sun. In a 24-hour day from sunrise to sunrise our line of longitude will arrive at the same point in space a little ahead of schedule. The result is earlier sunrises and sunsets before the solstice. After the solstice, the effect of earth’s eastward rotation produces later sunrises and sunsets. As the sun’s path across the sky drifts back towards the equator, the length of daylight shortens and the effect of later sunsets is no longer noticeable.

Another effect of the summer solstice is an extension of twilight to nearly two hours before sunrise and two hours after sunset. The northern hemisphere reaches its maximum tilt towards the sun at this time. As a result, the more northern latitudes receive longer periods of daylight as the circumference of the earth decreases towards the North Pole.

METEOR EVENTS
The Arietid Meteor Shower peaks on the night of June 7. The Arietids produce long, slow-moving trails which sometimes burst into fireballs. Fireballs are brilliant meteors that penetrate deep into the atmosphere. The constellation Aries is the radiant for this event. During June 10-21 watch for the Lyrid Meteor Shower radiating from the region of Lyra. It peaks June 15/16. The best time to view meteors is between midnight and 4:00am when the radiant constellation is overhead and when the moon does not interfere. The moon will not rise until after 3:00am on June 7 and sets before midnight on June 15.

LOCAL STAR COUNT
Join Red Rock Astronomers at Old City Park on Sunday, June 13, at 9:15pm for a tour of the night sky and telescope viewing. Meet at the southwest corner of the park below the bandstand and the duck pond. Bring a chair or blanket for viewing. Sponsored by WabiSabi and all ages are welcome. For information call 259-4743 or 259-3313.

Note: Hold your hand at arm’s length to measure apparent distances in the sky. Adjust for the size of your hand. The width of the little finger approximates 1.5 degrees. Middle, ring, and little finger touching represent about 5 degrees. The width of a fist is about 10 degrees. The hand stretched from thumb to little finger equals 20 degrees. The diameter of both the full moon and the sun spans only 0.5 degree.

VISIBLE PLANETS
Jupiter - The brilliant orb rising in the eastern sky during the middle of the night is Jupiter. It is high in the sky by early morning twilight. Jupiter is in Pisces, but the constellation is too faint to see in the morning twilight. (Magnitude -2.4)

Mars - Track Mars as it moves rapidly from west to east through Leo. On June 5/6 find it in the western sky less than one degree east of Regulus, the bright star below the mane of Leo. On June 7/8 look for it directly above Regulus. By month’s end Mars has moved halfway through Leo. Its red orb contrasts sharply with the yellow disk of Saturn to the east. Mars sets soon after midnight. (Magnitude +1.2)

Saturn - The bright yellow orb west of Spica (Virgo) is Saturn. Saturn’s position is fairly stationary in relationship with Virgo because of its distance from earth. This contrasts with the rapid west-to-east movement of Mars as it approaches Saturn’s position in the sky. (Magnitude +0.5)

Venus - The brilliant light cast by Venus is due to its dense atmosphere and its proximity to earth. It appears higher in the western sky each evening until mid-month when it reaches its highest declination (angle above the horizon) for the current year. On June 11 Venus forms a line with Pollux and Castor (twin stars of Gemini). Over the next few days Venus climbs to a position above the twin stars. On June 14 a thin crescent moon appears below Venus with Pollux and Castor to the north. (Magnitude -4.0)

Note: Apparent magnitude values range from -4 to +6 for most planets and visible stars. The lower the value the brighter the object. A decrease of 1.0 magnitude is 2.5 times brighter.

Primary Sources: USGS; U.S. Naval Observatory; Your Sky at http://www.fourmilab.ch/yoursky/

To find out when the space shuttle and International Space Station are visible from your location, go to: http://spaceflight.nasa.gov/realdata/sightings/index.html and click on Sighting Opportunities.

MAJOR CONSTELLATIONS this MONTH Overhead Bootes Corona Borealis Hercules Ophiucus Virgo Northward Cassiopeia Cepheus Draco Ursa Major Ursa Minor Eastward Aquila Cygnus Lyra Southward Corvus Libra Scorpius Westward Cancer Gemini Hydra Leo Locate the Big Dipper high overhead. Follow the arc of the handle to 0 magnitude Arcturus (Bootes). Continue the arc to 1st magnitude Spica (Virgo) in the southern sky. From Spica a line upward and to the right passes through 0 magnitude Saturn, 1st magnitude Regulus (Leo) and 1st magnitude Mars. Hold the star chart high above your head and match the compass directions to the direction you are facing. Adjust the star chart by orienting Ursa Major (Big Dipper) to match its position in the sky. The star chart approximates the night sky from astronomical twilight to midnight. As the night and the month progress, the constellations will shift toward the northwest.