The Moon and Planets
After last Friday’s Full Moon, the moon spends this week waning and rising in the middle of the night to linger in the early morning daytime sky. Its Last Quarter phase occurs Saturday morning, when it will appear half illuminated on the sunward side.
In the wee hours of Friday, June 16, and before dawn breaks, use your telescope to look low in the southeastern sky for tiny blue Neptune sitting less than 3 degrees to the left of the waning gibbous moon. Parts of Western Antarctica and the southern Pacific Ocean will see the moon pass in front of, or occult, the planet before dawn.
Mercury is lost in the dawn’s glow but extremely bright Venus is still shining in the pre-dawn eastern sky after it rises about 3:20 am local time. Viewed in a telescope around now, the planet presents a 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, becoming easier and easier to view.
On Thursday, June 15 at 6 a.m. EDT, the Earth’s orbit will carry us between Saturn and the Sun, also known as opposition. Then sitting opposite the sun in the sky, Saturn will rise at sunset and be closest to the Earth (75 light-minutes or 9.04 Astronomical Units away), and brightest, for this year. Around that date, the rings will appear 42 seconds of arc across (about the width Jupiter appears), and the disk of the planet will be about 18 arc-seconds. This year’s opposition coincides with Saturn’s northern solstice, when its north pole tilts directly towards the sun, so the rings will appear at their widest open as viewed from Earth.
Don’t fret if you miss seeing Saturn on Thursday. All the dates around June 15 will be nearly as good for viewing. After sunset, look for the yellowish planet low in the southeastern sky. It crosses the sky during the night and lands low in the southwestern sky at dawn.
Jupiter is the very bright star-like object in the southwestern evening sky, and it sets about 2:15 am local time. Jupiter’s four large Galilean moons are easily visible in a small telescope. A larger telescope will also show the Great Red Spot and the round black shadows cast by Jupiter’s moons when they cross (or transit) the planet. Here are the best events in Eastern Daylight Savings Time. (Simply add or subtract the appropriate hours to convert them to your time zone.)
The Great Red Spot is visible on Jupiter for about three hours centred on Sunday, June 11 at 9:38 pm (in twilight), Tuesday, June 13 at 11:17 pm, Friday, June 9 at 12:08 am, and Sunday June 18 at 10:27 pm.
Finally, the icy giant planets Uranus and Neptune are well-placed for viewing in the pre-dawn sky. Uranus, rising about 3 am local time, is a palm’s width to the upper right of Venus, and Neptune, rising about 1:30 am 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).
The Treats of Böotes and Coma Berenices
If you missed last week’s write-up about the constellations Böotes (the Herdsman or Plowman) and Coma Berenices (“Berenice’s Hair”), I posted it here.
Binocular Comet Update
The waning moon this week helps for looking for comets. I posted finder charts for the paths of several visible ones during June 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 41P/Tuttle-Giacobini-Kresak is visible all night, but it’s highest in the sky about 2 am local time. It has peaked in brightness, but is still in reach of binoculars. This week, look in the eastern evening sky about midway along the line joining Vega and Saturn, in eastern Ophiuchus.
Comet C/2015 ER61 (PANSTARRS) is a pre-dawn binocular comet that has recently reached peak brightness. This week it departs Pisces (the Fishes), above Uranus and Venus, and moves into Aries. It’s slowly moving in the direction of the Sun, following Venus.
Comet C/2015 V2 (Johnson) is an all-night binocular comet that is still brightening — visible in the southeastern sky as soon as it’s fully dark. This week, it moves out of southern Bootes (the Herdsman), heading down and to the left away from that constellation’s brightest star, Arcturus. On Thursday, it enters Virgo, heading roughly towards Spica (which is near Jupiter).
Stargazing News for this week (from June 11th) by Chris Vaughan.