Skylights: June 2022

June gives us the nights with the fewest hours of darkness, but there is still much to see during these short nights.

Solstice occurs at 5:14 on the 21st, and late in the afternoon on the 21st, the Sun crosses from Taurus and into Gemini. Earliest sunrise occurs at 5:10am on June 14, and the latest sunset occurs at 8:24pm on June 27. With solstice comes the shortest night of the year, June 20-21. During this overnight period, we’re only in astronomical darkness (when the Sun is 18° or more below the horizon) for four hours and 23 minutes. Astronomical twilight ends at 10:35pm and begins at 2:58am. 

Most are familiar with the twelve zodiac constellations, and that the Sun crosses through 13, as it spends about 18 days in the non-zodiac constellation Ophiuchus in early December. Although the ecliptic, the apparent path on the sky of the center of the Sun as seen from the center of Earth, does not go through more than 13 constellations, the southern portion of the Sun’s disk actually spends a few hours in a 14th, Cetus, in late March.

If you look at a map of the constellations with the ecliptic plotted, you can almost see how the Sun is leaping over Orion, reaching its crest just as it passes over the hunder’s club, before beginning to descend once again.

For 3 ½ days in June, leading up to the solstice, the southern limb of the Sun is within ⅓ ° of the northernmost boundary of Orion, the section of the constellation representing the hunter’s club. 

June begins with the Moon going through its waxing crescent phase. On the 1st, the dwarf planet Ceres is just 1.5° to its west. On the 5th, the crescent Moon will be just 0.2° from 3rd magnitude Eta Leonis, and become part of Leo’s Sickle asterism for one night. The Moon reaches its first quarter phase in Leo on the 7th. 

The Moon occults Dschubba (Delta Scorpii) on the 12th. The dark limb of the Moon covers the 2nd magnitude star at 10:19pm, and it reappears from behind the sunlit limb, beyond Crater Petavius, at 11:23pm. Because Dschubba is a binary star, you may notice its magnitude 4.0 companion wink out a few seconds before the magnitude 2.4 primary.

The Full Strawberry Moon occurs on the night of the 13th-14th, and is the lowest Full Moon of the year, culminating at just 22° above the horizon at 12:25am.

From June 18th and onward until its New phase on the 28th, the waning Moon passes beneath the line of planets in the morning sky. Last quarter Moon occurs on the 20th.

The morning planet parade continues through June, when all five bright planets appear in the sky before sunrise. While the planets are more separated than they were earlier this year, their arrangement this month is notable for them appearing in order, from east to west, of their absolute distance from the Sun. We’ll start with the innermost, and look at each planet in this sequence.

Mercury spends June in the morning sky but will not attain sufficient altitude to be easily observed until the second week of the month. By the 13th, it rises a full hour before the Sun, and on the 16th, it attains its greatest elongation, 23° west of the Sun. It remains in a favorable position for viewing though the rest of the month. Through a telescope, Mercury shows a crescent phase until the 22nd, when it transitions past its half phase and into a gibbous. Over the course of the month, its apparent size shrinks from 11.3 to 6.1 arcseconds as its distance from Earth nearly doubles, from 0.6 to 1.1 AU.

Venus remains prominently visible in the morning sky, rising about 2 hours before the Sun. Being on the far side of the Sun from Earth, Venus shows a gibbous phase, and shrinks from 13.7 to 12.1 arcseconds throughout June, as its distance increases from 1.2 to 1.4 AU.

Watch the skies on the morning of the 26th, when Venus appears 6.5° directly below the Pleiades cluster, and the waning gibbous Moon is just 2° to the north of Venus.

June begins with Mars less than 2° east of Jupiter, in Aquarius, but continues moving eastward through Pisces, gaining significant distance from Jupiter. In early June, Mars rises at 2:30am. The distance to the Red Planet closes from 1.5 AU to 1.3 AU by the end of June, when it rises at about 1:30am, and becomes a 7.2 arcsecond gibbous globe in a telescope.

Jupiter begins the month in Pisces, rising just after 2:00am. It becomes a resident of Cetus, notably a non-zodiac constellation, on the 25th, and will spend the summer within the whale..

Saturn rises just after midnight, in Capricornus. If you recall a few weeks back how all of the morning planets were evenly spaced, close together, note their positions in early June, when Saturn, Jupiter, and Venus are evenly spaced, with about 39° separating each planet pair.

Uranus is still fairly low in the east at the onset of morning twilight in early June, but an encounter with Venus on the 12th makes a good opportunity to see it. Although Uranus is theoretically visible to the unaided eye under ideal conditions, it will be a bit washed out by twilight when it rises, and even if it were in a dark sky, its proximity to brilliant Venus would make it quite a challenge to spot, given that Venus is about 8,000 times as bright as Uranus. Binoculars, or even better, a small telescope with low magnification, will reveal the pair quite nicely. At this conjunction, Uranus is nearly 16 times farther away than Venus (20.528 and 1.293 AU, respectively). Our seventh planet will become easier to see as it rises higher before sunrise during the latter half of June.

Neptune can be found on the border of Pisces and Aquarius, by drawing a line from Iota to Lambda Piscium, the eastern north-south segment of the Circlet asterism, and continuing southward just a little more than the same distance, about 5° from Lambda, and about 1° WSW of magnitude 5.5 20 Piscium.

Dwarf planet Pluto, in the far eastern reaches of Sagittarius, is now high enough to observe well before the onset of twilight. It can be found just 1° southwest of globular cluster M75. Pluto will require a 12-inch or larger telescope to see. Also, asteroid 4 Vesta, which is moving eastward through Aquarius, is about 8° east of Saturn, shining at magnitude 7.3 and requiring only binoculars to see. 

In the evening sky, you will have noticed that Orion has now disappeared, but we still have the entire eastern portion of the Winter Hexagon visible well into darkness. Pollux and Castor have assumed an orientation nearly parallel with the horizon, and will be visible in the evening sky for about another month, finally disappearing from view around July 4. Capella, in Auriga, stays in our sky considerably longer than the other winter constellations because it is nearly circumpolar, only dipping out of view at our latitude for about 3 hours before rising again in the NNE. If Capella is not visible in the sky due to it being below the horizon, or obstructed, you can always “find” it using the bowl of the Big Dipper. Use the top 2 stars of the bowl as pointers, and extend the line to the dipper’s right, or past the end opposite of the handle. At a distance of about 6 times the length of the bowl (60°, since the top of the bowl is about 10°) will be Capella.

Most notably, June nights herald the emergence of the Milky Way into the evening sky. When seen from a dark sky, the rising of the summer Milky Way is one of the most stunning sights. Knowing that its blotches of glowing clouds consist of billions of stars is an irresistible invitation to take your binoculars or telescope on an aimless wander through the Backbone of Night. Observing away from artificial light on June nights, you may, in addition, often be greeted with one of nature’s Earthly illuminated spectacles, the fireflies.