Southern Delta Aquariids
A strong meteor shower peaking in late July.
Every year from mid-July to mid-August, the Southern Delta Aquariids put on a meteor shower that peaks around July 28 or 29. It’s a reliable display, averaging 15 to 20 meteors per hour, with a peak rate of 18. The shower’s name comes from its radiant—the point in the sky where the meteors seem to originate—which sits in the constellation Aquarius, near the bright star Delta Aquarii. The name follows a pattern: the Latin possessive “Aquarii” gets its ending swapped for “-ids,” resulting in the double-i spelling.
No one knows for sure which comet is the source, though Comet 96P/Machholz is a suspect. Earlier theories pointed to the Marsden and Kracht sungrazing comets. The shower has two branches: the Southern (the stronger one) and the Northern. The Southern branch’s average radiant is at right ascension 339°, declination –17°. The Northern branch is weaker, peaking later in mid-August with about 10 meteors per hour and a radiant at RA 340°, DEC –2°.
The history of observations goes back to 1870, when G. L. Tupman plotted 65 meteors seen between July 27 and August 6, noting the radiant’s start and end points. Ronald A. McIntosh later refined the path using data from 1926 to 1933. In 1938, Cuno Hoffmeister and his German team first recorded a Northern Aquariid radiant. In 1949, D. W. R. McKinley spotted both branches but didn’t link them. That connection came in 1952 from astronomer Mary Almond, who used a specialized radio technique to determine the velocity and orbit of the δ Aquariids, describing them as a broad “system of orbits” likely from one extended stream. The Harvard Meteor Project (1952–1954) confirmed this with photographic data and also found that Jupiter’s gravity influences the stream’s evolution.
For best viewing, look up in the pre-dawn hours away from city lights. The Southern Hemisphere gets a better show because the radiant sits higher in the sky during peak season. In the Northern Hemisphere, the radiant stays above the southern horizon, so meteors fan out mostly to the east, north, and west; only a few short ones near the radiant head southward.
Quick Facts
- Parent
- 96P/Machholz
- Constellation
- Aquarius
- Ra
- 23 · 20
- Dec
- -16
- Month
- July 12 – August 23
- Peak
- July 30
- Zhr
- 16
Facts from the source article.
Lore & Background
The Southern Delta Aquariids get their name because their radiant appears to lie in the constellation Aquarius, near one of the constellation's brightest stars, Delta Aquarii. The name derives from the Latin possessive form 'Aquarii', whereby the declension '-i' is replaced by '-ids' (hence Aquariids with two i's). There are two branches of the Delta Aquariid meteor shower: Southern and Northern. The Southern Delta Aquariids are considered a strong shower, with an average meteor observation rate of 15–20 per hour and a peak zenithal hourly rate of 18. The average radiant is at RA=339°, DEC=−17°. The Northern Delta Aquariids are a weaker shower, peaking later in mid August, with an average peak rate of 10 meteors per hour and an average radiant of RA=340°, DEC=−2°.
The comet of origin is not known with certainty. A suspected candidate is Comet 96P Machholz. Earlier, it was thought to have originated from the Marsden and Kracht Sungrazing comets.
Reader's Guide
The Southern Delta Aquariids are notable as a strong, reliable meteor shower visible each year from mid July to mid August. Their peak on 28 or 29 July offers observers a chance to see 15–20 meteors per hour under good conditions. The shower's radiant lies in the constellation Aquarius, near the star Delta Aquarii, which gives the shower its name. The comet responsible for the shower remains uncertain, with Comet 96P Machholz a suspected candidate; earlier theories pointed to the Marsden and Kracht Sungrazing comets. The shower is best viewed in the pre-dawn hours, away from city lights. Southern Hemisphere viewers typically get a better show because the radiant is higher in the sky during the peak season. For Northern Hemisphere viewers, the radiant is above the southern horizon, so meteors fan out east, north, and west, with few heading southward. The Southern Delta Aquariids are part of a larger stream that also includes the weaker Northern Delta Aquariids, which peak later in mid August.
Did You Know?
- The Southern Delta Aquariids peak on 28 or 29 July each year.
- The shower's average zenithal hourly rate is 18 meteors per hour.
- The comet of origin is not known with certainty; Comet 96P Machholz is a suspected candidate.
- The name 'Aquariids' comes from the Latin possessive 'Aquarii' with the ending changed to '-ids'.
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