Jupiter is up shortly before 1 A.M. local time by the end of June and stands some 40° high an hour before dawn. It’s the planet with the most to offer telescopic observers: four bright moons that move in front of and behind its disk, plus a wealth of atmospheric details that change quickly, carried by its less-than-10-hour rotation period. Jupiter’s diameter grows from 37″ to 41″ during June. Its path carries it into the northwest corner of Cetus the Whale for the last six days of the month.
Frequent observers of Jupiter are aware that in recent years, the tilt of Callisto’s orbit relative to our line of sight takes the moon north and south of the planet, avoiding the disk. Earlier this year, Callisto began undergoing occultations, but that ends again this month. An intriguing event occurs early on June 5, when Callisto is partially hidden behind Jupiter’s northern limb. Observe between 4 A.M. and 5 A.M. EDT to watch Callisto skim the planet.
Following last month’s conjunction, the distance between Mars and Jupiter grows by more than 0.5° each morning. By June 3, Mars crosses into the northwest corner of Cetus, trekking through the Whale’s domain until June 9. The Red Planet continues eastward toward Omicron (ο) Piscium, ending the month 1.5° from the 4th-magnitude star.
Mars brightens from magnitude 0.6 to 0.4 during June. It remains challenging through a telescope. Its disk spans 7″ and is 86 percent lit. The small disk will be strongly affected by local atmospheric turbulence, so the best views will come in random occasional moments of good seeing. Telescopes larger than 10 inches will do best. We are only half a year away from the Red Planet’s opposition, so this will improve soon.
Venus starts June in Aries, rising before 4 A.M. local time all month. It crosses southern Aries before entering the brighter constellation Taurus midway through June. Through a telescope, Venus changes from a 78-percent-lit disk spanning 14″ on June 1 to 86 percent lit and 12″ wide on June 30. Its magnitude stays a constant –3.9.
Mercury joins Venus in mid-June. The pair provide dramatic photo opportunities. Mercury stands 8° due south of the Pleiades (M45) on June 13, glowing at magnitude 0.8. Venus is 11.5° farther west.
By the time Mercury reaches its greatest elongation west of the Sun (23°) on June 16, it forms an equilateral triangle with Venus and M45. The two planets continue their eastward drift and on June 22, Mercury stands at one tip of the Hyades, 3° northwest of Aldebaran. The planet has now brightened to magnitude 0.1. The faint stars of the Hyades will be hard to catch in the growing twilight. Venus stands 6° due south of the brighter Pleiades this morning.
On June 25 and 26, a waning crescent Moon joins in. The Hyades, Pleiades, Venus, Mercury, and the Moon sit above the eastern horizon an hour before sunrise. The Moon and M45 have been up since about 3 A.M. local time, followed by Venus around 3:40 A.M. By 4:30 A.M., the Hyades and Mercury are on view.
On June 26, Venus and the Moon stand less than 3° apart, with M45 6° above them. Directly below the Moon you’ll find Aldebaran, with Mercury 5.5° to the star’s left (northeast). Mercury is 2° high a full hour before sunrise.
Look for the waning Moon on the morning of June 27, with Mercury less than 4° to its lower right (southwest). Mercury continues dipping back toward the Sun and glows at magnitude –0.7 on June 30. That morning, Venus sits 1.2° north of Epsilon (ε) Tauri.