Perseids suffer in the moonlight as Saturn reaches opposition
Author: Alan Pickup
The maps show the sky at midnight BST on the 1st, 23:00 on the 16th and 22:00 on the 31st. An arrow shows the motion of Mars as the month begins.
As we catch our breath after the release of the first striking images and spectra from the Webb Telescope, August sees Saturn at its best and the return of truly dark skies to Scotland’s nights. The annual and prolific Perseids meteor shower is also on show, albeit in bright moonlight around its predicted peak on the morning of the 13th, just a day after full moon.
Swift meteors from the shower diverge from a radiant point in Perseus which lies below the “W” of Cassiopeia in the middle of our north-eastern sky at our map times (see our north star map). In fact, early Perseids began to be seen in mid-July and the shower peters out by about 24 August. More than 80 meteors per hour might have been counted under an ideal dark sky near the peak but, since few are bright enough to punch through heavy moonlight, expect numbers to be well down this year
Jupiter and Saturn feature on our southern map, though each stands further to the east (left) than they did last August in keeping with their easterly orbits around the Sun. However, if we watch both giant planets carefully this month, we will see them edging westwards against the stars. This apparently contrary or retrograde motion is temporary and results from our changing vantage point as the faster-orbiting Earth passes between them and the Sun.
First to reach opposition, directly opposite the Sun in our sky, is the ringed planet Saturn on the 14th. It is then at its closest and brightest for the year, 1,325 million km and magnitude 0.3. Rising in the south-east as the Sun sets, and shining steadily without twinkling, it is prominent in the south-south-east by our map times and stands highest as it passes almost 19° high in the south as seen from Edinburgh another two hours later. Its retrograde motion carries it 2° or four Moon-breadths westwards above the star Nashira in Capricornus during August while it lies above-left of the full Moon on the 11th-12th.
Although slightly closer than it was last year, Saturn also a little fainter. The reason is that we are seeing less of the north face of the rings as its tilt has decreased from 18° to 14°. Saturn’s disk appears 19 arcseconds wide as viewed through a telescope while the rings span 42 by 10 arcseconds. It is always a beautiful sight through a telescope, but its southerly location and relatively low altitude means that sharp views are all-too-rare at present.
Jupiter, in a corner of the constellation Cetus the Whale, rises in the east some 70 minutes before the map times, and climbs to pass 36° high in the south during our morning twilight. Brighter than any star, it improves from magnitude -2.7 to -2.9 as it approaches from 654 million to 605 million km. Telescopes reveal its cloud-banded disk, 47 arcseconds wide at mid-month, and its four main moons as they swing from side to side. Catch our Moon to the right of Jupiter on the evening of the 14th and to the left a day later.
The Sun sinks 10° southwards during August as Edinburgh’s sunrise/sunset times change from 05:17/21:20 BST on the 1st to 06:15/20:10 on the 31st. The Moon is at first quarter on the 5th, while its upper limb extinguishes the star Delta Scorpii at 22:38 BST on the 6th as viewed from Edinburgh. The two stand less than 6° high in the south-west at the time, but, at magnitude 2.3, this is the brightest star to be occulted by the Moon in 2022. The Moon is full on the 12th, at last quarter on the 19th and new on the 27th.
Mars makes it onto our star maps this month as it rises in the east-north-east just before midnight at present. It lies in Aries as the month begins, 13° to the right of the Pleiades cluster in Taurus, but it speeds 18° eastwards to pass 3° south of the Pleiades on the 13th and end the period in line between the Pleiades and Taurus’ leading star, Aldebaran. Approaching from 169 million to 143 million km and brightening from magnitude 0.2 to -0.1, its reddish hue becomes more prominent as it climbs well up into the south-east before dawn. Look for it below and left of the last quarter Moon on the morning of the 19th when its ochre globe appears only 9 arcseconds wide through a telescope.
Venus, brilliant at magnitude -3.9, rises in the north-east about two hours before the Sun on the 1st and 90 minutes before sunrise on the 31st. The thin brightly-earthlit Moon should make a superb sight above Venus before dawn on the 25th but may be more of a challenge to Venus’ left on the next morning. Mercury stands furthest east of the Sun (27°) on the 27th but is submerged in our evening twilight.
Looming at its highest in the south at our star map times is the asterism of the Summer Triangle, formed by the bright stars Vega, Deneb and Altair, the leading stars in the constellations of Lyra, Cygnus and Aquila respectively. Sadly, the projection used to depict the sky on our two-dimensional maps distorts the Triangle whose side between Deneb and Vega is (or should be) shorter than its other two.
While the Triangle has been known by various guises for centuries, its more recent popularization as the Summer Triangle owes much to the late Sir Patrick Moore. In fact, its stars have key roles in a classic Chinese folk tale, the Cowherd and the Weaver Girl, from over 2,600 years ago. A key element of the myth is that the Milky Way flows through the Triangle and close to Deneb, separating the lovers represented by Altair and Vega. The story is still celebrated in China during the annual Qixi or Qiqiao Festival which falls this year on 4 August.
Diary for 2022 August
Times are BST
- 1st 10h Mars 1.4° S of Uranus
- 3rd 23h Moon 5° N of Spica
- 5th 12h First Quarter
- 6th 23h Moon occults Delta Scorpii
- 7th 10h Moon 2.7° N of Antares
- 7th 11h Venus 7° S of Pollux
- 12th 03h Full Moon
- 12th 05h Moon 4° S of Saturn
- 13th 02h Peak of Perseids meteor shower
- 14th 18h Saturn at opposition at distance of 1,325m km
- 15th 11h Moon 1.9° S of Jupiter
- 18th 03h Venus 0.6° S of Praesepe
- 18th 15h Mars 6° S of Pleiades
- 19th 06h Last Quarter
- 19th 12h Moon 3° S of Pleiades
- 19th 13h Moon 2.7°N of Mars
- 24th 02h Moon 2.1° S of Pollux
- 25th 03h Moon 4° N of Praesepe
- 25th 22h Moon 4° N of Venus
- 27th 09h New Moon
- 27th 17h Mercury furthest E of Sun (27°)
- 31st 04h Moon 4° N of Spica
This is an extended version, with added diary, of Alan’s article published in The Scotsman on 30 July 2022, with thanks to the newspaper for permission to republish here.