The Solstice starts Northern Summer, the old Moon visits Morning Venus and Occults Aldebaran in Daylight, and a Great Double Shadow Transit!
The Solstice starts the Northern Summer
The beginning of summer for the northern hemisphere, known as the Summer Solstice, occurs on Wednesday, June 21 at 12:24 am Eastern Daylight Time. At that moment, the northern end of the Earth’s axis of rotation will be leaning directly towards the sun. As a result, the Sun will reach its highest noonday position in our sky for the year, shine with the most intensity on the northern hemisphere, and deliver the longest amount of daylight. More hours of concentrated, direct sunlight translates to more solar energy and warmer days! It is NOT the case, as some people think, that we are warmer because we are closer to the Sun — that event, called perihelion, actually happens in early January every year! Instead, the Earth is only two weeks from its farthest distance from the sun. Aphelion occurs on Monday, July 3, as it does every year.
For our friends in the southern hemisphere, this solstice signals the sun’s lowest noon-time height for the year, and marks the start of their winter. The summer solstice is good news for astronomers — after Wednesday, the days will slowly start to get shorter while the nights lengthen.
The Moon and Planets
For most of this week, the moon will swing towards the sun. During the next few mornings, it will appear in the eastern pre-dawn sky as it wanes daily to a slim old crescent. While the moon swings eastwards, it will visit Venus on Tuesday and Wednesday, hopping over the bright planet from one morning to the next. On Wednesday and Thursday morning, look east for the moon shining prettily just before sunrise. At new moon, which occurs Friday night, the moon becomes invisible next to the sun, and leaves the night sky dark for summer stargazing. Finally, on Saturday and Sunday evenings, it re-appears as another pretty crescent sitting low in the western sky after sunset.
Bright stars can be seen in a telescope in daylight! Thursday morning, June 22 brings a chance to see the old crescent moon pass in front of (or occult) the bright star Aldebaran in the daytime. Observers with telescopes in the continental USA and Canada can watch the bright leading edge of the moon cover the star first. About 70 minutes later Aldebaran will emerge from the opposite darkened limb of the moon. (Note: Care must be taken to avoid pointing a telescope anywhere near the sun.) Times and duration vary by region, so observers should begin to watch before 9:30 am EDT. In the GTA, the event will start about 9:42 am EDT and end about 10:54 am. It’s a challenging observation. Let me know if you see it!
Mercury has been lost near the sun’s glow but, starting Friday, it re-enters the western evening sky for a very good extended appearance for northern hemisphere observers. Over the next few weeks, I’ll point out the best times to look for it.
Extremely bright Venus is rises in the eastern sky about 3:15 am local time and remains easily visible until dawn. 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.
After last week’s opposition, Saturn is still looking its brightest and largest for the year. Once the evening sky darkens, look for yellowish Saturn low in the southeastern sky. It passes the south at its highest elevation (24°) at 1 am local time, and then sets in the west about dawn. The planet is experiencing its own northern solstice, when its north pole tilts directly towards the sun, so the rings appear at their widest open as viewed from Earth.
Jupiter is the very bright star-like object in the southwestern evening sky, and it sets about 2 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 Monday, June 19 from 10:04 to 10:37 pm EDT, the shadows of Io and Europa will briefly cross Jupiter simultaneously. Io’s shadow will already be more than halfway across when Europa’s shadow appears at the opposite limb.
The Great Red Spot is visible on Jupiter for about three hours centred on Sunday, June 18 at 10:26 pm, Wednesday, June 21 at 12:06 am, Friday, June 23 at 9:37 pm (in twilight), and Sunday June 25 at 11:15 pm.
Finally, the icy giant planets Uranus and Neptune are well-placed for viewing in the pre-dawn sky. Uranus, in Pisces (the Fishes) rises about 2:15 am local time, and is 1.5 fist widths to the upper right of Venus. Neptune, rising about 1 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).
Binocular Comet Update
The absent moon this week greatly helps when 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 1:30 am local time. It has peaked in brightness, but is still in reach of binoculars. This week, look in the southeastern evening sky about 2.5 fist widths to the upper right of the bright star Altair, and the same distance to the upper left of Saturn.
Comet C/2015 ER61 (PANSTARRS) is a pre-dawn binocular comet that has recently passed peak brightness. This week it travels parallel to Aries (the Ram), about a palm’s width below the line of stars. It’s slowly moving in the direction of the Sun, staying above 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 3:30 am local time. This week, it moves downward through the legs of Virgo while veering eastwards (to the left) of Spica (which is near Jupiter).
Stargazing News for this week (from June 18th) by Chris Vaughan.