The Gamma Ursae Minorids meteor shower
Key facts
- Peak
- around 18–20 January
- Active
- about 10–22 January
- Rate at peak (ZHR)
- about 3
- Speed
- 31 km/s
- Radiant
- Ursa Minor (near the star Pherkad, Gamma Ursae Minoris)
- Parent body
- Unknown
Dates shift slightly from year to year. This year's peak is in the events calendar.
The Gamma Ursae Minorids are a small January shower that shows how modern cameras and radar have changed meteor science. For most of history nobody knew they existed. They were first picked out by radar, which can detect meteors far too faint for the eye, and were added to the international list of showers as number 404.
On the night of 20–21 January 2010, six Finnish observers running wide-angle video cameras caught a small burst of bright meteors from the far north of the sky. When two of the cameras recorded the same meteor from different places, its path through the air could be worked out in three dimensions, and from that its orbit around the Sun. The orbit matched the Gamma Ursae Minorids. The meteors in that burst were brighter on average than the shower's usual radar meteors, which suggested Earth had brushed through a clump of larger grains.
The radiant. The meteors seem to come from Ursa Minor, the Little Bear, close to Pherkad, one of the two stars at the end of the Little Dipper's bowl. Pherkad and its brighter neighbour Kochab are sometimes called the Guardians of the Pole because they circle Polaris through the night. Because the radiant is so far north, it never sets from the UK or most of Europe and North America.
The parent. No comet or asteroid has yet been firmly linked to the stream. The orbit is tilted steeply to Earth's and reaches out towards the asteroid belt, which hints at a comet, but the source remains unidentified.
What to expect. Rates are low: a dark sky might give only two or three meteors an hour, and the shower is easily mistaken for the end of the Ursids or a stray Quadrantid. It suits patient observers, photographers and video cameras rather than casual watchers. Its medium speed means meteors that are neither the long, lazy trails of the slowest showers nor the quick flashes of the fastest.
Viewing. Northern observers are best placed. The radiant is highest in the hours before dawn. From the southern hemisphere it never rises.
Viewing tips
- Watch in the hours before dawn, when the Little Bear is high in the north.
- Find Kochab and Pherkad, the two stars at the end of the Little Dipper, to locate the radiant.
- Trace any meteor backwards: a Gamma Ursae Minorid points back to the far north.
- Leave a camera running on a tripod, because rates are too low to reward short sessions.
- Dress for a January night, with a hat, gloves and a blanket over your legs.