Last July, our view of Pluto changed forever. The nimble, piano-sized New Horizons spacecraft sped past the distant world then and has spent the year since returning stunning images and scientific data. On July 7, Pluto reaches its first opposition since this historic flyby. The dwarf planet won’t be easy to spot (after all, it glows at magnitude 14.1), but its proximity to 3rd-magnitude Pi (π) Sagittarii makes this a realistic challenge. For complete instructions and detailed finder charts, see “The quest for distant Pluto” on p. 64.
Neptune rises shortly before midnight July 1 and two hours earlier by month’s close. It has a convenient guide star in 4th-magnitude Lambda (λ) Aquarii. Once you locate this star with binoculars, magnitude 7.8 Neptune will be in view as well. The planet begins the month 29' (about a Full Moon’s diameter) southeast of Lambda and tracks slowly southwest. It passes 31' due south of the star July 24/25. A telescope shows Neptune’s 2.3"-diameter disk and distinct blue-gray color.
On the night of July 22/23, the waning gibbous Moon passes in front of (occults) Neptune for those in most of eastern North America. The faint planet will be hard to see when it disappears behind our satellite’s bright limb, but much easier when it reappears next to the dark limb. For locations south and east of northern New Mexico, the Moon also occults Lambda Aquarii. Exact times depend on your location. For specifics, go to
www.lunar-occultations.com.
Uranus rises about 90 minutes after Neptune, so by July’s final week, it pokes above the horizon before midnight and completes our tally of eight evening worlds. Uranus resides among the background stars of Pisces the Fish, southeast of the Great Square of Pegasus.
To find the planet through binoculars, first center magnitude 4.8 Mu (μ) Piscium in the field of view. Some 2° to 3° north of Mu lies a group of four 6th-magnitude objects. Magnitude 5.8 Uranus is the brightest and northernmost of this quartet. The planet doesn’t move much relative to the background stars during July, remaining some 2.7° north of Mu. To confirm a sighting, point your telescope at what you think is Uranus. Only the planet will show a distinctive blue-green disk spanning 3.5".
The last major event this month occurs the morning of July 29 when the waning crescent Moon occults Aldebaran. With the Moon just 23 percent lit and the star shining at 1st magnitude, even Aldebaran’s disappearance behind Luna’s bright limb should be easy to view. Observers south of a line running from southern New Mexico to northern Maine should see the event while those to the north will see the Moon and star just miss.