JUNE  1997

040    JUNE 1, 1997:   Moon near Sun

Follow the thin waning crescent moon in the dawn sky as it heads for new moon early Thursday morning. You must have an unobstructed eastern horizon. Observe with binoculars just before 5 a.m. On Monday the moon will be to the left of Saturn, and on Tuesday, it will be just to the right of Mercury. By Wednesday morning, the moon will be too close to the sun to be seen. However, on Friday evening look for a very thin waxing crescent moon two fist widths above the WNW horizon. The moon will be only 46 hours old. If you see a bright starlike object below the moon, you have also caught your first glimpse of Venus, making its summer debut. More about Venus in next week’s StarWatch. On Sunday, June 8th, join members of the Lehigh Valley Amateur Astronomical Society at the Bethlehem Rose Garden Children’s Festival, 1-5 p.m. as they observe the sun. The Bethlehem Rose Garden is located at Eighth Avenue and Broad Street, across from Nitschmann Middle School. Comet Hale-Bopp photo packets from the ASD Planetarium will also be available for purchase.

041    JUNE 8, 1997:   Venus Debuts in the Evening

This week marks the return of Venus, goddess of love, to the evening sky. The third brightest object in the heavens, Venus’s thick carbon dioxide atmosphere, sulfuric acid clouds, and searing 1000 degree F. temperature would make it anything but pleasant for life. Observing Venus at first may also prove challenging, but once you have made your initial sighting, successive views will become much easier. During this week the sun sets about 8:30 p.m. You should be at your observation site no later than 8:45 p.m. Apartment dwellers who live in upper floors or high rises with a clear view of the setting sun may actually be at an advantage because of their extra elevation. The prime ingredients are a very clear sky and a good western exposure. Note the location of the setting sun. You can begin observing as soon as the sun has set. Binoculars will prove useful if not mandatory even though Venus is exceedingly bright. At arm’s length, view one clenched fist width to the left of the sunset position and about one fist above the horizon at 8:45 p.m. As the months of summer progress, Venus will become a much easier target to spot. Clear skies!

042    JUNE 15, 1997:   Low Moon, High Sun

The bright moon starts the week to the left of Mars and continues moving eastward among the stars becoming full early Friday evening. You may have noticed that the full moons in winter appear high in the sky while the full moons of summer seem to hug the southern horizon. Part of the explanation lies in the fact that the orbital planes of the moon and Earth are similar. The difference is only 5 degrees. When the moon is full, it is opposite to the sun, and the hemisphere that we view is completely in daylight. In summer the sun is high in the sky, while the full moon must be low. The reverse is true for winter. The tilt of the Earth’s axis causes the seasonal extremes which result in a high summer sun and a low sun for winter. The sun is at its highest position in the sky on Saturday, making June 21 the longest day of the year and the beginning of summer. In Australia and other places in the southern hemisphere, June 21 marks the first day of winter. Skiing anyone?

043    JUNE 22, 1997:   More Light, More Color

This week about 10 p.m., look for orangy Mars in the southwest, about three fist heights above the horizon. To Mars’ left will be blue-white Spica, the brightest star of Virgo, the Virgin. Spica should appear just a tad bit fainter than Mars. The pair makes for an interesting contrast in colors which will be suitably enhanced with the aid of binoculars. The reason that binoculars accentuate color is because they gather more light onto the eye’s fovea (cones) where visual acuity and color perception are most heightened. In contrast, the eye’s peripheral vision is dominated by rods which are more sensitive to low light levels, but do not resolve well or distinguish colors at all. The secret to seeing color in astronomical objects lies in the quantity of light which is gathered. Look south to observe a waning gibbous moon above Jupiter in the predawn hours on Tuesday.

044    JUNE 29, 1997:   Reasons for the Seasons

Mid-afternoon on Friday, the Earth reaches aphelion, its farthest position from the sun. The sun’s distance will be about 94.5 million miles. In early January this distance shrinks to a minimum of 91.4 million miles as Earth passes its perihelion position. Confused? Don’t be! The seasons are not the result of Earth’s changing distance from the sun, but rather its axial tilt to its orbital (ecliptic) plane. If earth’s axis were vertical to the ecliptic, there would be no seasons. But because our axis is tilted 23-1/2 degrees from the vertical, our northern hemisphere leans in towards the sun during summer. The sun is higher in the sky and visible for a longer period of the day. This provides us with more energy and warmer weather, despite our greater distance from the sun. Go to Astronomy links, then to Misconceptions, and finally to Earth on the web page below to find out more about the seasons.