Almanac · Meteor showers
Perseids 2027
The Perseids peak on Fri 13 Aug 2027 at 08:04 UTC, when the Earth crosses the thick of the dust from Comet Swift-Tuttle. The Moon will be waxing gibbous, 86% lit.
- Peak Solar longitude 140°
- Moon at peak 86% lit Waxing Gibbous
- Radiant 03h 04m, +58° 00′ Never rises south of 32°S
- Best rate ZHR 100 About 60 an hour at best, from 45°N
Latitude by latitude, the night of 12–13 Aug
The best hour of the night nearest the peak at each latitude: when the radiant gives the most meteors while the sky is dark, how high it stands then, and how many an hour you would count from a suburban sky (Bortle 5) with that hour’s Moon; a dark site shows more. Times are local solar time; north of 32°N the radiant never sets.
| Latitude | Best hour | Radiant | Moon | Meteors an hour |
|---|---|---|---|---|
| 60°N | 01:45 | 61° up | Down | About 59 an hour, in twilight that never ends |
| 45°N | 02:58 | 62° up | Down | About 60 an hour |
| 30°N | 03:50 | 56° up | Down | About 56 an hour |
| 15°N | 04:29 | 45° up | Down | About 48 an hour |
| 0° | 04:49 | 31° up | Down | About 35 an hour |
| 15°S | 04:55 | 16° up | Down | About 19 an hour |
| 30°S | 05:04 | 2° up | Down | Hardly any: about 1.9 an hour at best |
| 45°S | — | — | Up, 84% lit | The radiant never rises |
Meteor shower The shower
- Zenithal hourly rate at the peak: 100. That is the count for one observer under a perfect sky with the radiant overhead; the table above is what the sky actually gives.
- Parent body: Comet Swift-Tuttle.
- Meteors meet the air at 59 km/s.
- Population index 2.2: each magnitude fainter holds that many times more meteors, which is what moonlight and city light take away.
How we worked it out: the peak is the instant the Sun reaches solar longitude 140° (J2000), the shower’s maximum in the International Meteor Organization’s Meteor Shower Calendar, found from Meeus’s solar theory; maxima are broad and wander by hours from year to year. The Moon is Meeus’s lunar theory, the one the map draws, checked against the U.S. Naval Observatory. Each latitude is worked at Greenwich’s longitude for the night nearest the peak, sampled every 10 minutes, and the rate is the IMO’s ZHR turned back into what one observer counts: ZHR × sin(radiant altitude) × r(limiting magnitude − 6.5), with the limiting magnitude the map’s own for that sky and Moon.
- International Meteor Organization, Meteor Shower Calendar (J. Rendtel): each maximum’s solar longitude, ZHR, population index and radiant
- J. Meeus, Astronomical Algorithms, ch. 25 (the Sun) and ch. 47–48 (the Moon), as the map draws them
- U.S. Naval Observatory, Astronomical Applications: the Moon’s illuminated fraction, which the tests hold these to