The Gamma Delphinids meteor shower
Key facts
- Peak
- 11 June (seen only in 1930)
- Active
- a single burst of about 30 minutes in 1930
- Rate at peak (ZHR)
- unknown; a short flurry in 1930
- Speed
- fast (not reliably measured)
- Radiant
- Delphinus (near the double star Gamma Delphini)
- Parent body
- Possibly an unknown long-period comet
Dates shift slightly from year to year. This year's peak is in the events calendar.
The Gamma Delphinids are a mystery shower: a single short burst of meteors reported once, in 1930, and never confirmed since. They show how outbursts from long-period comets can be both real and very hard to catch.
The 1930 report. On the evening of 11 June 1930, three members of the American Meteor Society observing in Maryland in the United States reported a flurry of meteors lasting about 30 minutes, between roughly 10.15 and 10.45 pm local time. The meteors appeared to come from near Gamma Delphini, a double star in the small constellation Delphinus, the Dolphin. A nearly full Moon was up at the time. No other reports came in, and nothing was seen from the radiant in later years, so many astronomers doubted that the event was real.
A modern idea. In the twenty-first century, the study of long-period comet outbursts, such as those of the Aurigids and Alpha Monocerotids, showed that a comet's narrow dust trail can produce a sharp burst lasting less than an hour, and then nothing for decades. Peter Jenniskens suggested that the Gamma Delphinids could be such an event, and predicted a possible return in the early hours of 11 June 2013. Some observers in the Americas reported fast meteors that may have come from Delphinus, but the results were inconclusive.
The parent. If the shower is real, its parent is probably a long-period comet that has not been discovered.
What to expect. Almost certainly nothing in any given year. The interest is historical and scientific.
Viewing. Delphinus is a compact, kite-shaped group of stars east of Altair in the summer sky. From the UK it is well placed in the second half of the night in June, though midsummer twilight hides faint meteors. It can be seen from both hemispheres.
Viewing tips
- Find Delphinus, a small kite of stars east of the bright star Altair.
- Look on 11 June if a forecast suggests a possible return.
- Run a camera during short June nights, when eyes miss faint meteors.
- Record exact times of any meteor from Delphinus.
- Treat the shower as a reminder to report unusual activity promptly.