August means the Perseids: the annual taking pictures star spectacular reaches its peak to wow meteor fans with ample vivid occasions, writes Astronomy Now’s Evening Sky supervisor Mark Armstrong.
Down the many years, the Perseid meteor bathe has turn into a agency favorite on the observing calendar, with astronomical teams gearing as much as profit from the perennial show of taking pictures stars. The large meteor showers are among the many hottest occasions for astro-friends to return collectively, hoping to see meteor-a-minute charges, whether or not you might be in it for the science or simply to have some enjoyable.
The Perseids are famend for producing vivid occasions, interspersed by an occasional thrilling fireball to elevate flagging spirits within the small hours. This attribute of the Perseids will assist for this month’s present, as glare from a pesky Moon, in a waning gibbous part simply three to 4 days previous full, will drown out lots of the fainter meteors.
What are meteors?
Our late and far missed colleague Neil Bone was for a few years the director of the British Astronomical Affiliation’s Meteor part. Right here’s his tackle the place meteors come from: “Meteors are the short-lived (one- to two-tenths of a second) streaks of sunshine seen within the evening sky as ‘taking pictures stars’. They happen, sometimes, in a layer of ambiance between 80–100 kilometres altitude the place small incoming particles – meteoroids – are destroyed, basically by frictional heating, on their high-velocity (11–76km/s) entry. Most meteoroids are small, maybe simply 2–5mm in diameter for these producing meteors within the bare eye vary, and are of very low density.”
Perseids linked to Comet 109P/Swift–Tuttle
When comets wing their means via the inside Photo voltaic System, their surfaces are heated by the Solar they usually turn into extra lively. Some cometary materials is misplaced and particles ejected, which over time unfold out round alongside the comet’s orbit across the Solar. When Earth intersects this stream of particles then numerous them enter our higher ambiance, vaporising to type the streaks of sunshine we see as meteors.
Every meteor bathe is linked with a ‘guardian comet’, with periodic comet 109P/Swift–Tuttle being related to the Perseids. This comet has a 133-year interval and final returned to the inside Photo voltaic System in 1992. Enhanced Perseid charges have been seen within the early nineties, which corresponded with this return.
When and the place to look
Perseid exercise is generally confined between 17 July and 24 August, with this yr’s peak anticipated at about 20:00 UT on 12 August. Your finest likelihood to see meteors is on the nights of 11/12 and 12/13 August, and you ought to be ready to remain up previous midnight into and previous the small hours, if in any respect attainable.
The taking pictures stars belonging to the bathe (i.e, not sporadic or random meteors, which happen incessantly each evening) will be traced again to an space of sky referred to as the radiant. This place displays the intersection between Earth’s orbit and that of the meteoroid stream.
The Perseid radiant lies within the far north of Perseus (round 4° of the magnificent Double Cluster close to magnitude +4.6 eta Persei), a location near the boundary with Cassiopeia. This space of sky is circumpolar (by no means setting) from the UK, however lies low within the north-eastern sky as darkness falls. Though the radiant is now round 25 levels up from London at 10pm BST, that’s nonetheless fairly near the north-northeastern horizon. These Perseids bursting out 20° or extra beneath the radiant shall be laborious to identify or be missed fully beneath the horizon.
The radiant climbs to a good altitude of fifty levels or so by 2am BST, when the areas of the sky from the place Perseids usually tend to seem shall be a lot better positioned than previous to midnight.
Don’t peer intently on the spot within the sky the place the radiant lies, although this will likely appear counter-intuitive. Perseid meteor trails or streaks right here will seem brief and due to this fact more durable to see. You will note many extra taking pictures stars in case you observe an space of sky 30-40 levels from the radiant (from the place, meteor streaks could seem longer) and round 50 levels above the horizon.
What can I count on to see?
Beneath a haze-free sky at a dark-sky viewing website on a moon-free yr, observers can count on to see between 50 and 70 Perseid meteors every hour close to the height. In cities or cities, noticed charges should still be round ten per hour within the early-morning hours when the radiant is excessive. Owing to glare from the Moon, noticed charges of fainter Perseids shall be curtailed.
Good luck!
