Tuesday, August 25 at 17:58 GMT – First quarter Moon
After the Moon has completed the first quarter of its orbit around Earth, the relative positions of the Earth, Sun and Moon cause us to see it half-illuminated on its eastern side. A first quarter Moon always rises around noon and sets around midnight, so it is also visible in the afternoon daytime sky. The evenings surrounding first quarter are the best times to see the lunar terrain when it is dramatically lit by low-angled sunlight.
Friday, August 28 evening – Waxing Moon close to Jupiter
In the southern sky on the evening of Friday, August 28, the waxing gibbous Moon will take up a position just two finger widths below (or 2 degrees to the celestial south of) the bright planet Jupiter with Saturn to their left. Both objects will fit within the field of view of binoculars (red circle). During the night, the diurnal rotation of the sky will lift the Moon to Jupiter’s left by the time they set at about 2:30 a.m. local time.
Friday, August 28 all night – Ceres at opposition
On Friday, August 28, the dwarf planet (formerly asteroid) Ceres will reach opposition, its closest approach to Earth for the year. Its path over several months is indicated in red, with dates. On the nights around opposition, Ceres will shine with a peak visual magnitude of 7.2, well within reach of binoculars and backyard telescopes. As a bonus, Ceres will be situated only palm’s width above (or 6 degrees to the north of) the bright naked-eye star Fomalhaut. Both objects will easily fit within the field of view of binoculars (red circle). Ceres will already be climbing the southeastern sky after dusk. It will reach its highest elevation, and peak visibility, over the southern horizon after 1 a.m. local time.
Saturday, August 29 evening – Bright Moon passes Saturn
The Moon’s monthly visit with the gas giant planets continues on Saturday, August 29. After 24 hours of orbital motion, the Moon will hop east to sit a palm’s width to the lower left (or 5.5 degrees to the celestial southeast) of Saturn. Both objects will fit within the field of view of binoculars (red circle). During the night, the diurnal rotation of the sky will lift the Moon higher than Saturn.
Sunday, August 30 all night – Sinus Iridum’s Golden Handle
On Sunday night, August 30, the terminator on the waxing gibbous Moon will fall just west of Sinus Iridum, the Bay of Rainbows. The circular 155-mile (249-kilometre) diameter feature is a large impact crater that was flooded by the same basalts that filled the much larger Mare Imbrium to its east, forming a rounded handle-shape on the western edge of that mare. The “Golden Handle” effect is produced by way the slanted sunlight brightly illuminates the eastern side of the prominent Montes Jura mountain range surrounding the bay on the north and west, and by a pair of protruding promontories named Heraclides and Laplace to the south and north, respectively. Sinus Iridum is almost craterless, but hosts a set of northeast-oriented dorsae or “wrinkle ridges” that are revealed at this phase.
Chris Vaughan is a science writer, geophysicist, astronomer, planetary scientist and an “outreach RASCal.” He writes Astronomy Skylights, and you can follow him on Twitter at @astrogeoguy. He can also bring his Digital Starlab portable inflatable planetarium to your school or other daytime or evening event. Contact him through AstroGeo.ca to tour the universe together.