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Sky Report - June 2013

Dusk Planets Part, Earliest Sunrise, Summer Begins and Lowest Full Moon

At the start of June, three planets can be seen low in the 9:20 p.m. western dusk. Lowest is the bright planet Jupiter. A little further to the left is brilliant Venus. Above Venus is the planet Mercury, the dimmest of the trio. Jupiter is appearing a little lower each night and will disappear in the twilight by June 7th.

On June 14th, our area will have its earliest sunrise of the year at 5:48 a.m. The longest day of the year is the start of summer on June 21st when we have 15 hours of daylight. The latest sunset occurs on June 27th when the sun disappears at 8:49 p.m. The reason why these three events occur on three separate days is our reliance on the mean sun for our clock time. The mean sun moves at a constant rate along the celestial equator. The actual sun that we see moves at a different rate along its path, slowest in early July when we are farthest from the sun and fastest in early January when we are closest to the sun. The difference between the position of the mean sun and actual sun causes the actual sun to come up earliest in mid June, and to set latest in late June.

Summer officially begins about 1 a.m. Daylight on June 21st. This is the time when the sun's vertical rays reach farthest North of the Earth's equator, along the Tropic of Cancer. The Tropic of Cancer is latitude 23.5 degrees North. Places on the Earth along the Tropic of Cancer are Havana, Cuba, central Mexico, Southern Algeria, Southern Egypt, Central Saudi Arabia, Northern India, Hong Kong and Taiwan. These locales see the sun shining directly overhead on this day of the year. In our area, the sun reaches an altitude of 72.5 degrees, 80% of the way from the southern horizon to the top of the sky.

The moon is full on June 23rd, then appearing in the star group Ophiuchus (the Serpent Bearer). This full moon has the lowest sky track of any of 2013's full moons, reaching only 1/3 of the way up in the South in the middle of the night (about 1 a.m.) The full moon appears opposite the sun in the sky. So when the sun is at its highest, the full moon is at its lowest.

Early June Sights – The moon is fullest on the evening of June 3rd, appearing over the bright star Antares of the Scorpion. In the days following, the moon will make a rather rapid exit from the evening sky, rising more than an hour later each night. The low summer full moons often appear yellowish as they shine through haze. In the evening sky, the Summer Triangle is prominent in the East. Atop the Triangle is the very bright star Vega in the Northeast. The bright orange star Arcturus is nearly overhead. You can be sure of finding Arcturus by extending the handle of the Big Dipper outward.

Mid June Sights – By June 11th, the moon has shrunk to half full in the morning dawn sky. In June, yellowish Mars creeps from Leo into Virgo. The planet Saturn is to the left of Mars near Virgo's brightest star Spica. You can distinguish planets from bright stars by the planets steadier light. On moonless evenings, you can glimpse the Milky Way as a delicate glow, running from low in the North, through the Summer Triangle (in the East) and down into southeast. At 5 a.m. on June 17th, a very narrow crescent moon will appear close to the bright planet Jupiter low in the East Northeast. June 20th is the Summer Solstice. The word 'solstice' is from the Latin, meaning 'sun standing still'. On this day, the sun's rising and setting points reach their most northerly positions.

Late June Sights – The planet Mercury can be seen low in the Northwest to the left of the bright stars Pollux and Castor of Gemini. Look about 9:30 p.m. The crescent moon returns to the western dusk on June 22nd, appearing to the left of Mercury and Gemini's bright stars. On the evening of June 26th, the half full moon will appear below and to the left of the planet Mars. The next evening, the moon will appear below and to the right of the planet Saturn. On the last day of June, the moon will appear to the right of the Scorpion's claws.

We have an early full moon on the evening of June 3rd when the moon appears just over the head of the Scorpion. Below and to the left of the moon will be the bright pinkish star Antares (means 'rival of Mars'). In the early morning hours, the moon will crest about 1/3 of the way up in the South. Often the moon appears yellowish due to summer haze, possibly giving rise to the word 'honeymoon'. The star group Scorpius that lies below the moon resembles a letter 'J'.

The planet Venus will pass directly between the Earth and sun in the late afternoon of June 5th. Using special filters, observers can see a small black dot on the edge of the sun's upper northern area starting about 6:22 p.m. Weather permitting, there will be telescopes set up on the west side of Mountain Ridge High School to safely watch this unusual event, which will not recur until 2117. Viewing the sun through sunglasses then is extremely hazardous and may permanently damage your central vision. The sun then will be setting about 8:30 p.m. So the transit (or planetary eclipse of the sun) may be seen locally for 2 hours, weather permitting. In the past, these rare transits of Venus were used to refine the Earth-sun distance by using timed observations of the transits from different parts of the world. At the time of the June 5th transit, Venus will be 27 million miles away from the Earth. Our neighbor world will then appear to be about 1/33rd of the size of the sun. Venus, when it passes between the Earth and sun moves about a degree a day relative to the sun. By June 17th, Venus will be a striking object low in the southeastern dawn, best seen about 30 minutes before sunrise (look at 5:15 a.m.). By the end of June, Venus will be rising in the southeast about 4:05 a.m., about 90 minutes ahead of sunrise.

Summer officially begins in the late afternoon of June 20th, when the sun's direct rays reach farthest North along the Tropic of Cancer (latitude 23.5 degrees N, about the latitude of Havana, Cuba). On this day, the sun rises farthest to the North (of East), crests highest in mid day in the South and sets farthest to the North (of West). Daylight then lasts 15 hours. Summer is our longest season, lasting 93.6 days, (from June 20th to September 22nd). During the summer, the sun's rising and setting points shift about 30 degrees (towards the South) as daylight drops from 15 hours to 12 hours and 8 minutes.

Astronomy Club Meets – The Cumberland Astronomy Club will meet at 7:30 p.m. on June 15th, the third Friday of the month. Meetings are held in the community room of the LaVale Public Library, about a mile to the East of the State Police Barracks in LaVale. All interested sky gazers in the Tr-State area are welcome to attend.

By Dr. Bob Doyle

To contact Dr. Doyle, his mailing address is Planetarium, Frostburg State University, Frostburg, MD 21532 or by email at rdoyle@frostburg.edu.









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