Enjoy Asteroid Juno, Mercury at Dusk, and Evening Gas Giants, plus a Jeweled Scimitar on the Moon!
See Asteroid Juno
On Sunday, July 2 at 9 a.m. EDT, the large asteroid Juno will be in opposition to the sun, making it the closest to Earth and brightest for the year. Visible in small telescopes at magnitude 9.8, it will be located within the Milky Way at the northern end of Scutum (the Shield).
The Moon and Planets
Feel cooler lately? Tomorrow, the Earth reaches aphelion (from the Greek word for Sun, helios) its farthest distance from the sun for this year — about 5 million km farther than where we were on January 4, at perihelion.
The moon reached First Quarter last Friday evening, so the next few evenings are excellent for looking at it. It sits in the evening sky at sunset and sets in the wee hours while it waxes through its gibbous (more than half illuminated) phases.
The Golden Handle or Jeweled Scimitar is a large bright C-shaped semi-circle formed when the Jura Mountains, which partially encircle Mare Iridum, are shallowly illuminated by sunlight. Look for the feature overnight on Tuesday, July 4. It will be along the terminator (the dividing line between the lit and dark sections of the moon), towards the moon’s Northwest (our upper left) edge.
Overnight on Thursday, the nearly full moon will sit only two degrees above yellowish Saturn. The moon will actually look full on Saturday evening, but the July full moon, known as the “Buck Moon”, “Thunder Moon”, or “Hay Moon” occurs in the wee hours of Sunday, July 9. Full moons always rise around sunset and set around sunrise.
Mercury is visible for northern hemisphere observers this week. It sets about 10 pm local time, but the best time to look for it is 9:15 to 9:30 pm. It will be less than a few finger widths above the western horizon, south of where the sun went down, and will be the only visible object in that area of sky.
Extremely bright Venus is rises in the eastern sky about 3 am local time and remains easily visible until dawn. Viewed in a telescope around now, the planet presents a more than half illuminated phase that is slowly waxing fuller and shrinking in diameter as it heads beyond the Sun. Nevertheless, it will be in the morning sky for a few more months while becoming easier and easier to view.
Saturn is the bright yellowish object visible low in the southeastern sky after the evening sky darkens. It crosses due south (at its highest elevation of 24°) at midnight local time, and then sets in the west about dawn.
Jupiter is the extremely bright object in the southwestern evening sky this week. It sets about 1 am local time. The planet’s four large Galilean moons are easily visible in a small telescope. A larger telescope will also show the round black shadows they cast when they cross (or transit) the planet — and the Great Red Spot. Here are the best events in Eastern Daylight Savings Time. (Simply add or subtract the appropriate hours to convert them to your time zone.)
On Tuesday, July 4, from 12:18 am until the planet sets, Io’s shadow will transit. The Great Red Spot is visible on Jupiter for about three hours centred on Monday, July 3 at 12:04 am, Wednesday, July 5 at 9:35 pm (starting in twilight), and Friday, July 7 at 11:14 pm.
The icy giant planets Uranus and Neptune are well-placed for viewing in the pre-dawn sky. Uranus, in Pisces (the Fishes) rises about 1:30 am local time. Neptune, rising about midnight local time, is in the southeastern sky about two finger widths to the lower left of the medium-bright star Hydor in Aquarius (the Water-Bearer).
Distant Pluto, which resides among the stars of Sagittarius (the Archer), reaches maximum visibility for the year on Sunday, July 9. But at magnitude 14, it’s out of reach of all but the largest telescopes. The nearby full moon won’t help matters, but here’s a diagram.
Binocular Comet Update
The late-setting waxing moon this week spoils the sky a bit when looking for comets. I posted finder charts for the paths of two visible ones during June/July here. In binoculars and low power telescopes, expect the comets to appear as faint greenish blobs (quite different from a star). If a comet develops a tail, it will point roughly away from the Sun. If you find one in a telescope, watch for 15 minutes or so — you’ll see it moving with respect to the stars nearby.
Comet C/2015 ER61 (PANSTARRS) is a pre-dawn binocular comet that has been dropping in brightness. It rises about 1:40 am local time, and is travelling parallel to Aries (the Ram), about a palm’s width below the line of stars. Tomorrow morning (Monday), it will be about a palm’s width below the modest star Hamal in Aries, to the upper right of Venus.
Comet C/2015 V2 (Johnson) is a binocular comet that is still brightening. It’s visible in the evening southeastern sky as soon as it’s fully dark, and sets about 2 am local time. Tonight (Sunday), it is one finger width below the moon. For the rest of this week, it continues to move downward, about a fist’s width to the left of Spica (which is near Jupiter).
Stargazing News for this week by Chris Vaughan.