Sparks fly during the Perseid meteor shower this month as two lovers meet by a river of stars.
This year the Chinese festival of Qixi falls on August 14th which almost coincides with the Perseids reaching their maximum on the 12th.
Qixi celebrates the tale of the heavenly weaver girl and the cowherd and the one time during the year when they are reunited.
Their tryst is a changeable date and occurs on the seventh night of the seventh month in the Chinese lunar calendar.
The beloved folktale relates how a cowherd meets a celestial princess while she and her six sisters are on a break from their duties weaving cloth into clouds. She is the most beautiful of the siblings and elects to stay behind while the others return to the sky.
She is soon missed, and the sky gods order the weaver girl back to their abode. With great reluctance she complies, leaving behind her partner and a son and daughter on Earth.
The cowherd has an old ox though who explains that his hide is magical and grants the wearer an ability to fly up to the heavens. After the ox dies the cowherd gathers the kids, throws the hide over his shoulders, and ascends to meet his love. There, the family are reunited.
The weaver girl's latest absence from her loom does not go unnoticed either. In a fit of pique, the Jade Princess scores a line across the sky with her silver hairpin to form the Milky Way, keeping the young couple permanently apart.
You can see them still separated by the starry stream.
The weaver girl is the blue-white sun Vega while the cowherd is represented by the star Altair on the Milky Way’s opposite bank. The fainter stars either side of Altair are said to be the couple’s son and daughter.
The story has a happy conclusion though.
Moved by the tears of the weaver girl which fall to the Earth as rain, the sky gods agree she and her spouse can meet each year on the seventh night of the seventh month. All the magpies of the world then flock together to form a bridge for them to cross the Milky Way.
However, the lovers can only reunite if the weather is fair whereas any storms at this time of year mean feathers fly as the magpies struggle to hold formation in the gusts while spanning the stream.
Should you just happen to see a lone magpie on the 14th, don’t forget to chide it for shirking its duty.
The Perseid meteor shower
The Perseids are one of the year’s best known and more reliable meteor showers. They are associated with comet 109P/Swift-Tuttle and occur when we run into the densest clumps of dust in the comet’s orbit around August 12th.
Most meteors, or shooting stars, are caused by salt grain-sized particles rushing our atmosphere at high speed and being vaporised due to friction. The streak of light marks their final moments.
Pebble-sized pieces can give rise to bright fireballs and draw gasps of delight from observers. One spectacular event we saw last year left a smoke trail that persisted for many minutes as it drifted in the high winds of the upper atmosphere.
The Perseid peak is on August 12th this year and with moonset at 10.45pm it means conditions are excellent for the display. A few days before maximum will also yield results but the rates start dropping off dramatically after the 12th.
You should expect to see a meteor every couple of minutes or so away from lit-up areas and the numbers improve when the radiant source gets higher as the night wears on.
Be wary of rates of a hundred or more touted in some sources though as this is a theoretical value based on perfectly dark and clear skies, no meteors missed, and the radiant source overhead. The true number seen is almost always much lower.
Meteors in a shower appear to diverge from a particular point in the sky called the radiant. However, they travel in parallel, and the effect is solely due to perspective.
Paradoxically, the radiant is not always the best place to look.
Meteors generally only begin to become visible a short distance away their radiant. For the Perseids look in the direction of Andromeda and Pegasus early in the night or follow them passing through Cassiopeia and then on overhead. Plan a watch of 30 minutes or more to ensure you’ll catch some shooting stars.
Those that don’t appear to be Perseids are either members of some minor displays active at this time of year or sporadics, meteors that don’t seem to be associated with any shower.
That we got to see any Perseids at all in 2020 was a bonus. Weather prospects were not good for night of maximum, with Dublin blanketed by foggy conditions.
Antonio Martin-Carrillo of UCD had recommended studying the cloud forecast on windy.com which showed a potentially clear spell in parts of Wicklow. Both of us plumbed for the car park at Turlough Hill and the gamble paid off. The elevated site meant we were above the blanket of fog and had mostly clear skies to see a wonderful display.
If the forecast looks good this August 12th, then set up a recliner, sit back, and enjoy nature’s celestial fireworks.
Moon watching
New moon is on August 8th, first quarter on the 15th, full moon on August 22nd, and last quarter on the 30th. Full moon this month is a seasonal blue moon according to some definitions of the term. This is when the phase is the third of four full moons in an astronomical season.
The planets this month
Venus is the sole easily seen planet in the evening sky this month and can be found low above the western horizon. You’ll find its brilliance becomes a little more obvious as twilight deepens. Venus sets just before 10pm mid-month, or about an hour after the sun.
The slender crescent moon is a short distance to the right of Venus on the 10th and is to the planet’s upper left when closer on the evening of August 11th.
Mercury and Mars are also evening sky objects but are presently too deep in twilight to be seen from Ireland.
Jupiter and Saturn both come to opposition this month in the constellation Capricornus, with the latter reaching that point on August 2nd and Jupiter doing so on the 20th. It is when the two worlds are brightest, and their disks appear largest in the eyepiece.
Opposition occurs when the Earth lies directly between the sun and a planet or other solar system body outside our orbit. At such time the object rises in the eastern sky at sunset and is visible throughout the night.
Jupiter offers a lot to see and its annually improving position on the celestial sphere means better opportunities to come for northern hemisphere observers scrutinising detail in the gas giant’s turbulent atmosphere through a telescope.
The changing aspect of the four largest Jovian moons can also be followed from night-to-night in binoculars. An app such as Gas Giants (iOS) or Moons of Jupiter (Android) will allow you identify them.
Butterscotch-tinged Saturn does not show the same swirls and patterns in its atmosphere as Jupiter, but the magnificent ring system compensates.
Saturn appears elongated in 15-power binoculars while surrounding stars are pin sharp. A telescope or larger binoculars like my 25x100mm (which need to be tripod mounted due to their heft) will distinctly show the rings separate from the planet’s globe.
Saturn’s largest moon Titan can be seen in most binoculars as a faint “star” about four ring-widths from the planet, while a half dozen of Saturn’s biggest satellites are within reach of backyard amateur telescopes.
The nearly full moon is close to Saturn as the sky darkens on the 20th and lies near Jupiter on the next evening.
John Flannery is a long-time amateur astronomer with an interest in the history and lore of the sky along with astronomical phenomena observable with the unaided eye. He is a member of the Irish Astronomical Society