The Southern Delta Aquariids is a strong and fairly consistent meteor shower that takes place from July 12th to August 23rd. This year, peak activity occurs on July 29th and is predicted to reach a maximum Zenithal Hourly Rate (ZHR) of 16 meteors per hour. The stream is generally regarded as producing faint meteors, void of fireballs which move across the sky at slow to medium velocity. The shower is best seen from the tropics and southern hemisphere, upon where the radiant appears higher in the sky, compared to northern temperate latitudes.
The Southern Delta Aquariids is the brighter part of the Delta Aquariid meteor shower; the Northern Delta Aquariids being the weaker stream. The period of activity of the northern shower is similar to that of its southern partner - from July 15th to August 25th (peak: August 6th) - although it's ZHR is a paltry 4 meteors per hour.
Discovery and Parent Body
Lieutenant Colonel G. L. Tupman, a member of the Italian Meteoric Association made the first detailed recordings of Delta Aquariids meteors between July 27th and August 6th, 1870. The streams were then unidentified, but by plotting data from 65 meteors, he was to a reasonable degree of accuracy able to determine the general area of the radiant.
Between 1926 and 1933, New Zealander Ronald McIntosh improved the position of the radiant based on a greater number of observations. A few years later in 1938, Cuno Hoffmeister founder of Sonneberg Observatory, along with his German colleagues were able to first record the northern part of the stream. It was astronomer Mary Almond, in 1952, who finally confirmed the presence of the two separate radiants.
The parent body of the Southern Delta Aquariids is uncertain. However, comet 96P/Machholz or comet Machholz as it's often referred to is a possible candidate. This Jupiter family comet was discovered in 1986 by amateur astronomer Donald Machholz using just a pair of 130mm binoculars. It has an orbital period of 5.2 years.
The shower radiants are located in the faint zodiac constellation of Aquarius, which is positioned about 30 degrees to the south and southwest of the "Square of Pegasus". The southern radiant is just over 3 degrees west of star Skat (δ Aqr - mag. 3.3), with the northern radiant a further 14 degrees to the north. The brightest star in the surrounding sky is first magnitude Fomalhaut (α PsA - mag. 1.2) in the constellation Piscis Austrinus. Fomalhaut is positioned about 14 degrees south-southeast of the southern radiant.
What to expect
The best time to observe the meteor shower is during the early hours of the morning and ideally from a dark site. At peak date on July 29th, 2013 the last quarter Moon will not significantly interfere. Observers in the southern hemisphere and tropics will get the better show; the radiant is higher in the sky from these latitudes. For those at northern temperate latitudes, the radiant appears low above the southern horizon and as a result few meteors will be seen heading southwards, unless they are fairly short and near to the radiant.
Although the meteors are often faint, a respectable 16 per hour may be seen at best. The meteors travel at a slow to medium velocity (41 km/s). As with all meteor showers the meteor trails often streak across the sky quite a distance from the actual radiant point, in many cases in excess of 30 degrees and therefore can effectively appear anywhere in the sky. It's therefore a good idea not to look directly at the radiant itself, but scan a large area of the sky around it.
Southern Delta Aquariids Data Table 2013
|Meteor shower name||Southern Delta Aquariids|
|Activity||July 12th -> August 23rd|
|Peak Date||July 29th|
|RA (J2000)||22hr 40m|
|Parent body||Uncertain but possibly comet 96P/Machholz|
|Notes||Also referred to as the Southern Delta Aquarids meteor shower|
Comet 96P/Machholz Data Table (at epoch February 17th, 1994)
|Classification||Jupiter-family comet (NEO)|
|Discovery date||May 12th, 1986|
|Aphelion distance (AU)||5.94321|
|Perihelion distance (AU)||0.12378|
|Orbital period (years)||5.28362|
|Last perihelion||July 14th, 2012|
|Next perihelion||October 26th, 2017|
|Notes||Also known as Comet Machholz or 96P/Machholz 1. Discovery made by amateur astronomer Donald Machholz using 130mm binoculars|