Skylights: June 2024

Sun

Our earliest sunrise of the year occurs at 5:10am EDT on the 14th, and our latest sunset is at 8:24pm EDT on the 26th. 

Solstice occurs at 4:51pm EDT on the 20th, when the Sun will be at its most northerly extent. Early during the following morning, the Sun crosses the galactic equator and enters Gemini.

Moon

June begins with the Moon in its waning crescent phase, passing 2.9° east of Neptune on the 1st.

On its way to new phase on the 6th, the waning crescent Moon passes 6.0° northwest of Mars on the 3rd. On the 5th, the 28-day, 1.6% illuminated crescent will be 3.6° northwest of Jupiter, and 4.6° west-northwest of Mercury. On the same morning, look for the Pleiades cluster just 0.5° north of the Moon.

New Moon occurs at 8:38am on the 6th, marking the beginning of Lunation 1255.

The stars of late winter and early spring are still with us in June, and they are notably visited by the waxing crescent Moon during the second week of the month.

On the 8th, the beautiful waxing crescent Moon lies 4° west-southwest of Pollux, and forms a right angle with the twin stars Pollux and Castor of Gemini until it sets at 10:54pm EDT. During the following evening, see the Moon 5.0° north west of M44, the Beehive Cluster, in Cancer, and on the 11th, it passes 2.7° north of Regulus, in Leo.

First quarter Moon occurs in Libra at 1:18am on the 14th. Early in the evening of the 16th, the waxing gibbous Moon appears 3.3° east-southeast of Spica, in Virgo.

The waxing gibbous Moon is near Antares, the red giant star in Scorpius, on the 20th, but unlike last month’s three arcminute separation, this month we miss the close approach, as the pair sets when they are separated by a full 3°.

The Moon is full at 9:21pm on the 21st. This full Moon, the Strawberry Moon, is the most southerly full Moon of the year, transiting at 12:57am EDT on the 22nd, at just 19° above the southern horizon.

The waning gibbous Moon is 6.0° southwest of Saturn just before morning twilight on the 27th. Although the sky brightens, you may still be able to see Saturn through a telescope well into daylight. At 10:00am, just over an hour before moonset, Saturn will be just 1.2° northeast (oriented at the 12 o-clock position) of the Moon. Use medium to high magnification on the largest telescope you have available, and try an orange or red filter to improve contrast.

After passing just 0.3° south of Neptune early on the 28th, the Moon reaches its last quarter phase, in Cetus, at 5:53pm EDT.

Mercury

After a less than favorable morning apparition, Mercury passes superior conjunction on the 16th, and enters the evening sky.

Venus

Venus is at superior conjunction on the 4th. This isn’t just a conjunction, but an occultation, as Venus passed directly behind the Sun, beginning at about 2:00pm EDT on the 3rd, and remaining occulted for the next 45 hours, unlike Venus transits, which take around 6-7 hours to pass in front of the Sun. Also unlike transits, occultations occur much more frequently, with the last occurrence in June 2016, and the next one in June 2032, whereas the last transit occurred in 2012, and there will not be another one until 2117.

After conjunction, Venus returns to the evening sky, but will be too close to the Sun and difficult to observe until July.

Mars

At the beginning of June, Mars rises at about 3:00am EDT in Pisces. On the 3rd, the 26-day waning crescent Moon lies 6° to the northeast. The Red Planet crosses into Aries on the 9th, and climbs more northerly along the ecliptic as the momth progresses. By month’s end, Mars rises just after 2:00am EDT, and the planet’s tiny 4.3 arcsecond globe lies at a distance of 1.739 au.

Jupiter

Jupiter, which passed through superior conjunction in mid-May, won’t be in favorable viewing position until mid-June, when it will rise about an hour before sunrise, and be positioned distinctly beneath the Pleiades cluster in Taurus, and 5.6° above the constellation’s brightest star, Aldebaran. For an observing challenge, Jupiter pairs with Mercury on the 4th, with the two planets appearing just 0.2° apart and rising at 4:34am EDT.

Saturn

On the 9th, Saturn reaches its point of western quadrature, 90° from the Sun. 

Saturn becomes an evening planet in late June, rising before midnight beginning on the 29th.

Saturn reaches its stationary point on the 30th, and will be in apparent retrograde motion through Capricornus through November 16th.

With Saturn well above the horizon during the early morning hours, and observing season for the ringed planet now underway, take note of the narrow ring plane angle. Now just 2.5° relative to Earth, Saturn’s equatorial plane takes on a linear appearance, not unlike that of Jupiter. Its satellites will now appear to cross in front of the planet, and with the Sun-relative plane at just 5.5°, some of the moons will cast shadows upon the planet. A sufficiently large telescope and steady seeing conditions will be needed to see even the shadow of the largest of Saturn’s moons, Titan, which will be just three quarters of an arcsecond in size when it crosses Saturn’s cloud tops once every 16 days.

What may be easier to observe is the moons being eclipsed by Saturn.

Uranus

Uranus is now in Taurus, and rises even with the Pleiades cluster. The planet will be difficult to observe in early June, with it rising during twilight, but during the s second half of the month, it can be spotted with binoculars just over 6° southwest of the cluster.

Neptune

Neptune is at western quadrature on the 20th, bringing our most distant planet into position for observability in the morning sky. Throughout June, it is located just over 10° east-northeast of Saturn, the line between the two planets paralleling the ecliptic, which lies just over 1° to their north.

While Neptune is just over 5° southeast of the Circlet asterism of Pisces, more specifically, its southeasternmost magnitude 4.5 star lambda, Neptune now lies closer to an asterism of 5th magnitude stars which will make an easy reference point for tracking the planet during the 2024-25 observing season.

Starting at Saturn, move 10° due east, just over one binocular field of view. From there, you will come across a quadrilateral of stars ranging from magnitude 4.4 to 5.1 which comprise a near-perfect rectangle defined by the stars, from north to south, 29, 27, 33, and 30 Piscium. The quadrilateral is a near-perfect rectangle, 3°x0.5° and oriented roughly north-northeast to south-southwest, with the northern pair of stars being slightly fainter than the southern pair. The northeastern vertex, defined by 29 Psc, the dimmest star of the quartet, forms the acute vertex, resulting in the eastern side of the quadrilateral being slightly longer than the western side.

Now that you are familiar with this asterism, use the eastern (long) side to draw a line from 33 and through 29. Continuing this line 1.7°, slightly more than three apparent diameters of the Moon, and you will arrive at Neptune.

Help in finding Neptune comes by way of the waning gibbous Moon on the morning of the 28th, when, just before 4:00am EDT, the distant planet will be just 0.3° of our satellite. The two objects will easily fit within the same telescopic field of view. During alignments like this it’s always fascinating to compare the objects in view for matter of perspective. In this instance, Neptune is 14 times the diameter of the Moon (measured at the polar axis). At 12,050 times the distance, light from Neptune takes 247.5 minutes to reach us, whereas the Moon is just 1.3 light seconds away.

Minor Planets

4 Vesta continues its easterly trek through Gemini during the first half of June, moving into Cancer on the 14th. Remaining at magnitude 8.4 from its distance of over 3 au, our sky’s brightest asteroid is becoming more difficult to observe as it slips into twilight.

Perhaps the month’s best night for observing Vesta comes on the 8th, when the 2.1-day, 7.4% illuminated crescent Moon lies 5.5° to its west-northwest. Although this is not a close passage by the Moon, an easy journey through Gemini with a small telescope at low magnification will lead you right to it. Starting at the Moon, move northeast just about 1.5° to find magnitude 4.1 upsilon Geminorum. From there, move directly to the left, 3.2° east-southeast to magnitude 3.4 kappa Geminorum. Vesta is just 1.6° southeast of this star. Be sure to distinguish it from magnitude 7.3 82 Geminorum, which is just 0.5° to its southwest.

Asteroid 2 Pallas is well-placed for observing during June, looping westward through Corona Borealis, its position well north of the ecliptic being a result of its highly inclined 35° orbit. On the 25th, it moves southwestward into Serpens.

From June 20-27, Pallas lies within 0.5° of T Coronae Borealis, a recurrent nova that is expected to undergo its once-per-80-year outburst sometime in 2024. The asteroid passes as close to 0.2° southeast of its location on the 23rd, and while the star is still quiescent, it will hover around magnitude 10.0, just slightly dimmer than Pallas. 

1 Ceres is moving west-southwestward through Sagittarius. Its southerly declination places it in its most favorable viewing position after 2:00am during June. The presence of bright moonlight will hamper observations of the magnitude 7.5 dwarf planet during the latter half of June, but on the 22nd, the Moon occults Ceres, beginning at 12:30am and ending at 1:49am. A medium-sized telescope with high magnification will be sufficient to observe the occultation.

Pluto, at a distance of 34.2 au in Capricornus, shines at a dim magnitude 14.4 and can be found 2.7° east-southeast of the globular cluster M75. 

June brings the shortest nights, and with the onset of astronomical darkness not arriving until well after 10:00pm, night sky observing opportunities can be seemingly scarce. 

This is the first time of the year when the Milky Way begins to appear soon after darkness. Scorpius and Sagittarius begin to dominate the southern sky, and Ursa Major has rounded its way west of the meridian.

High in the south, we turn our attention to a tight little constellation of moderately bright stars that is unfortunately overlooked due to its lack of notable deep sky objects that are accessible to small telescopes, although it does contain two notable double stars that are on the Astronomical League’s Double Star Observing Program: zeta and sigma Coronae Borealis. Asteroid hunters will be turning their attention to the Northern Crown constellation this month as the second-discovered asteroid, Pallas, is currently traversing it.

But what we will be looking for in Corona Borealis this year is a variable star known as T Coronae Borealis (CrB). T Crb is what is known as a recurrent nova. Nova, meaning “new,” is a type of variable star where an outburst results in a sudden but temporary brightening, usually by many magnitudes.

Before knowledge of modern astrophysics and without the possession of instruments to observe them, early astronomers noted when a “new” star would suddenly appear where there was no visible star previously.

T CrB is a recurrent nova, meaning that there is an astrophysical process in place that is cyclic, resulting in the “nova” occurring at regular intervals. In the case of T CrB, the cycle is about 80 years, with the last outburst observed in 1946.

The mechanism driving the cycle is a result of T CrB being a binary system composed of a white dwarf and a red giant star. A white dwarf is a dense, dormant remnant of a star that is no longer undergoing fusion at its core, Its only energy is the residual thermal energy left over from its main sequence phase. A red giant is a low-density, bloated cool star. The white dwarf seeps up some of the red giant’s outer material, and when enough of this material collects in a thin layer on the surface of the white dwarf, the pressure and temperature of this layer flashes in a runaway thermonuclear reaction, causing the nova.

When this happens, the star will rapidly brighten from its quiescent 10th magnitude up to an expected 2nd, placing it within naked-eye visibility and causing a notable change in the constellation. The brightening may last from several days to a few weeks.

The nova may occur any time between now and November 2024. An observing campaign is underway to catch T CrB in the earliest phases of its nova outburst, so be sure to keep watching it.

Once it fades out, the cycle begins anew, with the next outburst in the early 2100s.

Finally, one of the lesser-known meteor showers, the Bootids, is active during the closing days of June. Although not a very active shower, the radiant is well-placed high overhead during evening hours, and it is not uncommon to see a meteor or two during your sessions.