The Delta Cancrids meteor shower
Key facts
- Peak
- around 17 January (historically listed)
- Active
- about 1–24 January
- Rate at peak (ZHR)
- about 3–4
- Speed
- 28 km/s
- Radiant
- Cancer (near the star Asellus Australis, Delta Cancri, close to the Beehive Cluster)
- Parent body
- No single parent; part of the Antihelion Source
Dates shift slightly from year to year. This year's peak is in the events calendar.
The Delta Cancrids were for many years listed as a January shower of slow meteors from Cancer, the Crab. Today they are recognised as the January stretch of the Antihelion Source, and their story explains how that idea came about.
Why Cancer in January? Many meteoroids orbit the Sun in the same direction as the planets, on orbits that are only slightly tilted to Earth's and that reach inside Earth's orbit. Earth meets them from the direction roughly opposite the Sun, called the antihelion direction. As Earth moves round its orbit, that direction moves through the zodiac by about one constellation a month. In January it lies in Cancer, so the meteors seem to come from there.
The old list. Observers in the twentieth century gave the January activity its own name, the Delta Cancrids, after Delta Cancri (Asellus Australis, the Southern Donkey), a star beside the Beehive star cluster. Similar names were given in other months: Delta Leonids in February, Virginids in spring, Scorpiids and Sagittariids in summer. Careful plotting and later video orbits showed that these were not separate streams but the same broad source seen at different times. In the mid-2000s meteor observers combined them all as the Antihelion Source.
What to expect. Three or four slow meteors an hour, coming from a broad area around Cancer rather than a sharp point. Because the antihelion direction is opposite the Sun, the radiant is highest around local midnight.
Viewing from the UK. Cancer is high in the south around midnight in January. It is a faint constellation, but the Beehive Cluster is easy to find on a dark night as a misty patch between the bright stars of Gemini and Leo.
Viewing worldwide. The radiant is north of the celestial equator but visible from almost everywhere, high in the north for southern observers.
Slow meteors from Cancer on a January night are a reminder that the sky is never quite empty of meteors, even between the named showers.
Viewing tips
- Watch around midnight, when Cancer is highest in the south.
- Find the Beehive Cluster, a misty patch between Castor and Regulus.
- Look for slow meteors from that general area rather than a precise point.
- Expect a few meteors an hour on a dark, moonless January night.
- Combine a watch with the end of the Quadrantid season.