The Xi Ursae Majorids meteor shower
Key facts
- Peak
- around 21 January
- Active
- about 17–26 January
- Rate at peak (ZHR)
- very low (detected mainly by video)
- Speed
- about 42 km/s
- Radiant
- Ursa Major (near the star Alula Australis, Xi Ursae Majoris, at the Great Bear's back foot)
- Parent body
- Unknown
Dates shift slightly from year to year. This year's peak is in the events calendar, and the meteor-shower planner shows how high the radiant climbs from where you live, night by night.
The Xi Ursae Majorids are a small January shower found by video cameras. They show how much modern camera networks have added to the list of known showers.
Discovery. In 2009 Takashi Kanamori, an amateur observer in Tokyo, analysed two years of recordings from video cameras at several sites in Japan. A meteor filmed from two places can be traced in three dimensions and its orbit around the Sun worked out. Kanamori found eleven groups of meteors with matching orbits that had not been listed before, and they were added to the international working list of showers. The Xi Ursae Majorids were one of them.
The radiant. The meteors seem to come from near Xi Ursae Majoris, also called Alula Australis, one of a pair of stars marking the back foot of the Great Bear, below the bowl of the Plough. This part of the sky is high in the north-east from the UK in the hours after midnight in January.
The parent. No parent body has been identified. The medium speed of the meteors, about 42 kilometres per second, and the shape of their orbits suggest a comet.
What to expect. Very few meteors: the shower is weak enough that it was only recognised by comparing hundreds of measured orbits. A visual observer would see at most an occasional member, mixed among sporadic meteors and the last Quadrantids and Gamma Ursae Minorids.
Why it matters. Many weak showers like this are confirmed or rejected only after several independent camera networks have looked for them. Each confirmed stream is evidence of a comet or asteroid, perhaps still undiscovered, whose debris crosses Earth's orbit.
Viewing. This is a northern shower. From the UK the radiant is well placed after midnight; from the southern hemisphere it stays low or never rises.
Viewing tips
- Find the Great Bear's back feet, two pairs of stars below the Plough's bowl.
- Watch after midnight, when Ursa Major is high in the north-east.
- Run a video camera, which is how this shower was found.
- Plot meteors carefully to tell them from other January showers.
- Dress for a cold January night.