The Daytime Sextantids meteor shower
Key facts
- Peak
- around 27 September to 1 October
- Active
- late September to early October
- Rate at peak (ZHR)
- about 5 by eye at best; radar rates equivalent to about 20
- Speed
- about 32 km/s
- Radiant
- Sextans (close to the Sun in the sky)
- Parent body
- Probably related to asteroid (155140) 2005 UD, and through it to 3200 Phaethon
Dates shift slightly from year to year. This year's peak is in the events calendar.
The Daytime Sextantids are an autumn daylight shower with a remarkable family connection: they appear to be relatives of the Geminids, the strongest annual shower of all.
Discovery. The shower was found in the 1950s by the Australian radio astronomer Allan Weiss, during a radar survey of meteors at Adelaide. Radar picks up the ionised trails of meteors by day as well as by night. A few years later, a southern hemisphere radar survey detected it again and first pointed out that its orbit resembled that of the Geminids.
The Phaethon family. The Geminids come from 3200 Phaethon, an unusual near-Earth asteroid that passes very close to the Sun. In 2005 a smaller asteroid, (155140) 2005 UD, was discovered on an orbit very similar to Phaethon's, and researchers soon matched it to the Daytime Sextantids. Phaethon and 2005 UD share an unusual bluish colour, and both may be pieces of a larger body that broke apart long ago. Recent studies suggest 2005 UD is not the shower's direct parent but a sibling, with the meteoroids and the asteroid both produced by the same break-up.
The radiant. The radiant lies in Sextans, the Sextant, a faint constellation south of Leo, only about 30 degrees from the Sun. It rises less than an hour before dawn, so the shower is almost entirely a daytime event.
What to expect. Radar shows a broad peak around 27 September to 1 October, with rates equivalent to about 20 meteors an hour. By eye, very few are seen: perhaps an occasional earthgrazer low in the east just before dawn.
Why it matters. The Japanese spacecraft DESTINY+ is planned to fly past Phaethon and possibly 2005 UD. Understanding the Daytime Sextantids helps scientists to work out how this family of objects formed and how they shed dust.
Viewing. Radio observing is the practical method, from any latitude.
Viewing tips
- Use radio or radar data to follow the shower; it is a daytime event.
- Look low in the east in the last half-hour before dawn for long earthgrazers.
- Stop observing before sunrise and never look towards the Sun.
- Compare late September radio counts with mid-September for the increase.
- Watch the Geminids in December: they are this shower's better-known relatives.
Its parent is thought to be Phaethon, an asteroid that may be a burned-out comet. See the other comets behind meteor showers.