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For those of you who like to listen to your stories, click below to hear Susan Trishel Monsøn reading Chris Vaughan’s summary of the planets movements this month.
During the opening few days of June, magnitude 3.15 Mercury might be glimpsed sitting very low in the west-northwestern sky after sunset; it will be especially visible for observers located at southerly latitudes. But the speedy planet will soon become unobservable from anywhere while it heads to solar conjunction, between Earth and the Sun, on June 10. For Northern Hemisphere observers, the very southerly declination of Mercury’s orbit during June will prevent the planet from rising very long before the Sun, even though its western elongation will be increasing. During the final third of June, Mercury will be visible in the east-northeastern pre-dawn sky from both hemispheres. Mercury will reach greatest western elongation 22 degrees from the pre-dawn Sun and peak visibility on July 4. Viewed in a telescope during that time, the brightening planet will exhibit a waxing crescent phase and a shrinking apparent disk size.
Extremely bright (magnitude -3.85) Venus will slowly continue to increase its angle east of the Sun during June, but it won’t climb high enough to see in a dark sky after sunset until the end of the month. If you have an unobstructed view of the west-northwestern horizon, look for Venus sitting low in the sky. It will set at about 9:45 p.m. local time on June 1 and about 10:10 p.m. on June 30. Viewed through a telescope during June, Venus will exhibit a 90-per-cent illuminated phase and an apparent disk diameter of around 11 arc-seconds. (As always, ensure that the Sun has completely disappeared below the horizon before using binoculars or telescopes to view Venus.) Our neighbouring planet will be travelling eastward through the stars of Gemini from June 2-24. Then it will pass into Cancer, where it will rendezvous with Mars on July 12-13. On June 11, the very young crescent Moon will be positioned several finger widths to the lower right (or three degrees to the celestial west) of Venus, allowing both objects to appear together in binoculars, and offering a nice photo opportunity.
After spending several months parked halfway up the western evening sky, Mars will rapidly descend into the post-sunset twilight during June. On the first days of the month, the magnitude 1.75 red planet will be shining a palm’s width to the lower left (or five degrees to the celestial south) of Gemini’s easterly bright star Pollux, and Mars will set at about 11:30 p.m. local time. On June 8, Mars will move into Cancer where, on June 23, its orbital motion will carry it directly through the large open star cluster known as the Beehive or Messier 44. That passage will be a terrific sight in a backyard telescope or binoculars. Mars will be telescope-close to the “bees” on the surrounding evenings. Telescope views of Mars during June will show a shrinking, four arcsecond-wide disk. At the end of June, Mars will be setting at 10:30 p.m. local time. Much brighter Venus, positioned about a palm’s width to Mars’ lower right, will already be closing in for their conjunction on July 12-13. Watch for the waxing crescent Moon to hop past Mars on June 12-13.
Throughout June, bright, white, magnitude -2.4 Jupiter will shine among the modest stars of western Aquarius and about two fist diameters to the left (or celestial east) of fainter Saturn. On June 1, Jupiter will rise at about 1 a.m. local time and will remain visible until almost sunrise. Around June 20, Jupiter will begin to rise before midnight. The following day Jupiter will temporarily cease its regular eastward motion and then commence a retrograde loop that will last until mid-October. At the end of June, Jupiter will be rising at about 11:15 p.m. local time, and it will have brightened to magnitude -2.64. Unfortunately, the low summertime ecliptic will prevent the planet from climbing very high before the sky brightens. Telescope views of Jupiter during June will show that its large, banded disk is increasing in apparent diameter from 41.1 to 45.2 arc-seconds. The Great Red Spot will be visible crossing Jupiter’s disk every second or third night. Single transits across Jupiter’s disk by the round, black shadows of its Galilean moons will be commonplace. Double shadow transits will be visible from different parts of the world on June 5, 12, and 26. The waning Moon will sit six degrees below Jupiter on June 1 and will return to hop past Jupiter on June 28-29.
During May, yellow-tinted Saturn will be located in the southeastern sky, travelling retrograde westward among the stars of Capricornus. The magnitude 0.57 planet will rise at about 12:20 a.m. local time on June 1 and then begin rising before midnight starting a week later. At the end of June Saturn will have brightened to magnitude 0.38 and will then rise at about 10:20 p.m. local time; however, the low summer ecliptic will keep the ringed planet from ever climbing more than one-third of the way up the southern sky. When viewed through a backyard telescope during June, Saturn will exhibit its majestic rings, a number of moons, and an apparent disk size that grows from 17.6 to 18.3 arc-seconds. Saturn’s separation west of Jupiter will increase from 18 to 19.5 degrees during the month, and the waning moon will pass five degrees below Saturn on June 27.
Even though blue-green Uranus will be steadily increasing its elongation west of the Sun throughout June, the shallowly dipping morning ecliptic will prevent the magnitude 5.9 planet, and the stars of southern Aries surrounding it, from climbing very high before the dawn sky begins to brighten. Uranus will rise at 4 a.m. local time on June 1, and two hours earlier at month end. The old crescent Moon will pass several finger widths below (or three degrees to the celestial south) of Uranus on June 7.
During June the distant and slow-moving planet Neptune will be located in the lower part of the southeastern sky in eastern Aquarius. That’s a palm’s width below (or to the celestial south of) the ring of stars that form western Pisces and about two fist diameters to the left (or celestial east) of much brighter Jupiter. On June 26, Neptune will temporarily cease its regular eastward motion and commence a retrograde loop that will last until early December. The blue, magnitude 7.9 planet will become observable in backyard telescopes starting an hour or two after it rises, which will be at about 1 a.m. local time on the June 1 and at midnight at month’s end.
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.