StarWatch: Moravian College Astronomy

StarWatch for the greater Lehigh Valley

JUNE 2015

JUNE STAR MAP | MOON PHASE CALENDAR | STARWATCH INDEX | NIGHT SKY NOTEBOOK

Print Large Sky Charts For 10 p.m. EDT: NORTH | EAST | SOUTH | WEST | ZENITH

Current Solar X-rays:

Current Geomagnetic Field:

981 JUNE 7, 2015: How the Crow Got His Caw: One of my favorite springtime star patterns is Corvus the Crow, and the instructive mythology associated with it. To find Corvus, start with the Big Dipper about an hour after sundown. The bowl will be high in the north and upside-down. Observe how the handle arcs, and follow this curve across the sky to orangey Arcturus. Continuing southward, the arc swoops lower, reaching blue supergiant Spica which is the alpha star of Virgo the Virgin. You are almost there. Lower and to Spica’s right is the quadrilateral of four faint stars which outlines the crow’s body. There is an additional luminary directly below the lower right hand star and one above the upper left star of the main grouping which completes the pattern. “A crow you say. No way,” but the curvature of the stars mimics the hunched back of a crow. Sipping a glass of wine may help, but using binoculars will be a little more persuasive in revealing all six stars. In the past, crows were light feathered and sang melodiously, but that all changed with Corvus, who was Apollo’s most trusted messenger. One hot, summer’s day, Corvus was dispatched to bring his master a cup of cool water from Apollo’s favorite spring. At once Corvus flew off to complete his appointed task, but upon arriving by the water, he noticed some ripening figs, his favorite food. Dallying by the spring for several days, he gorged himself on the figs, and then flew back to Apollo with the water. Troubled by the delay, Apollo demanded an excuse, and Corvus insisted that a water snake had prevented him from retrieving his drink in a timely manner. Apollo quickly realized that the crow was lying, for as Corvus spoke, pieces of regurgitated fig leaves fell from his beak. Enraged by the crow’s deceit, Apollo darkened his feathers and changed Corvus’ voice to a caw, then banished him to the sky to be placed on a slithering water snake (Hydra) with his back to a cup (Crater) of clear, cool water just beyond his reach. And that’s no crow!

982 JUNE 14, 2015: Christmas in July—Almost!: “Do you see what I see? A star, a star, dancing in the night, with a tail as big as a kite.” Yes, it’s just six more months until Christmas, but sky actors are positioning themselves for perhaps the best celestial holiday-like show of the year. Whatever the Star of Bethlehem was in actuality, it probably had more astrological than astronomical significance, and it certainly was not just a one night affair, but probably evolved over many weeks or months. This pageant, however, involves another set of players—Luna, Venus, and Jupiter, different than what was thought to have been the real characters in the Star of Bethlehem drama—Jupiter, Saturn, and eventually, Mars. The spectacle unfolds in the west after sundown. Venus (brighter) and Jupiter have been moving closer together for many months, but in the last few weeks, it appears as if the pace of this jousting exercise has quickened. Before they lock horns on the evening of June 30, a crescent-shaped moon will swing by and join the pair in a beautiful triple conjunction. Look for a seven percent lit moon in the west, well below Venus and Jupiter, on Thursday, June 18. The following twilight, a 13 percent illuminated crescent will be found directly under Venus to form a wide triangle along with Jupiter. Saturday, June 20 finds the triangle tightened with the 20 percent lit moon favoring Jupiter’s side. Summer solstice, the longest day of the year, June 21, catches the thickening crescent “trucking” eastward, away from the closing planets which by this point will have nudged to within five degrees of each other. During the following week, Jupiter and Venus continue to converge until Tuesday, June 30 when they will appear to be nearly on top of each other, only about 1/3-degree apart. During July, they will appear to separate slowly because of their orbital geometry and still be in the sky relatively close to each other right through mid-July and another encounter with Luna. Merry Christmas in July—almost!

983 JUNE 21, 2015: Finally, It's Summer: We have finally made it to the summer solstice. Yes, spring may have been a little too cool at the start and a little too warm and muggy near the end, but at least we know what to expect for the next three months before the frosty chill of a mid-October morning awakens us to the realization that big changes are in the forecast. The sun has been climbing steadily in the sky since December 21 after reaching its lowest position beneath the celestial equator, shining directly over the Southern Hemisphere’s Tropic of Capricorn. Sol’s change is a result of Earth’s 23.5 degree axial tilt to the perpendicular of its orbital plane (the ecliptic), causing Earth’s equator to be tilted 23.5 degrees to its orbit. As Earth traces its yearly track around Sol, the sun reflects this motion by tracing a path along the ecliptic, a journey which shifts it above the equator for half of the year and below the equator for the other half. The Northern Hemisphere is favored between the vernal and autumnal equinoxes, allowing Sol to be visible for a longer duration of time and be positioned higher in the sky for a greater portion of each day. The outcome is more direct energy and greater absorption resulting in warmer conditions. However, we all know that the hottest stretch of the year does not occur at the time of the summer solstice. Beyond the solstice the Northern Hemisphere still experiences a net energy gain, and average temperatures continue to climb, reaching a maximum near late July for the Mid-Atlantic region. Drier locations have less of a seasonal lag while areas like the Caribbean, under the influence of large bodies of water, have an increased lag in the seasons. This greater lag for the subtropics is reflected in the Atlantic hurricane season which starts on June 1 and continues through November 30, a result of water’s insatiable ability to absorb and retain heat. The transitional months for us are May and November. Happy summer! It’s finally here, but not to stay.

984 JUNE 28, 2015: Venus to Embrace Jupiter: Keep looking west during evening twilight for the next several days because you’ll see unfolding one of the best celestial events of the year. Venus (brighter) and Jupiter have been on the march towards one another for the last several months, and on Tuesday, June 30, they will embrace, approaching each other to within 1/3rd of a degree after sundown (20 minutes, 36 seconds of arc distant). It’s much less than the angular diameter of the full moon, which on Tuesday will be 31 minutes, 34 seconds of arc. There are 60 minutes of arc in a degree and 360 degrees in a circle. The waxing gibbous moon will be seen at the same time low in the southeast trailing behind the planet Saturn. Venus and Jupiter will easily fit within the same field of view in large and small telescopes alike. One of the interesting effects of viewing this conjunction will be how the unaided eye responds to Venus and Jupiter in such close proximity. When the eye views bright objects under high contrast conditions (bright against dark), it tends to flare the object making it appear larger. Prove this to yourself by viewing Venus 15 minutes after sundown. It will appear like a pinpoint, small against the bright turquoise sky; but as conditions darken, Venus will appear to have rays of light emanating from it. The amount of flaring is dependent upon visual acuity, age, and the size of the opening of the iris—how much light the eye is collecting. The effects of glare increase the perception of size, and will make Venus and Jupiter appear larger and even closer together than they actually are. Through a properly focused telescope, Venus will appear to be crescent-shaped (less than half lit), but bland while Jupiter will have at least three of its four Galilean satellites visible. Io and Europa will be so close together during the East Coast dusk that they will probably appear as one satellite through most scopes. In time zones farther west, they should have changed positions enough to be easily visible. Clear skies!

[June Star Map]

[June Moon Phase Calendar]