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The Delta Aquarids or Delta Aquariids is an annual meteor shower that takes place during July and August. It consists of two branches, the Northern Delta Aquariids and the Southern Delta Aquariids, of which the Southern Delta Aquariids is the stronger. This year's event takes place between July 12th and August 23rd, with peak activity occurring on July 29th when up to 16 meteors per hour can be expected (Zenithal Hourly Rate). In addition, the waxing crescent Moon sets around midnight local time leaving the pre-dawn hours free from its glare. This meteor shower is best seen from tropical and Southern Hemisphere locations.

The Northern Delta Aquariids stream is feeble in comparison. It peaks on August 7th with a maximum ZHR of 4.

Comet 96P/Machholz from HI-2 camera of STEREO-A spacecraft (credit:- NASA/ Johns Hopkins University)

Discovery and Parent Body

Lieutenant Colonel G. L. Tupman, a member of the Italian Meteoric Association, made the first detailed recordings of the Delta Aquariids between July 27 and August 6, 1870. Until then, the streams were unidentified, but by plotting data from 65 meteors he could to a reasonable degree of accuracy determine the general region of sky where the radiant is located.

Between 1926 and 1933, New Zealander Ronald McIntosh improved the radiant position. In 1938, Cuno Hoffmeister the founder of Sonneberg Observatory, along with German colleagues were the first to 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, is a possible candidate. Amateur astronomer Donald Machholz, using a pair of 130mm binoculars, discovered this Jupiter family comet in 1986. It has an orbital period of 5.2 years.

Radiants

The shower radiants are located in the faint zodiac constellation of Aquarius and southwest of the "Square of Pegasus". The southern radiant is 3 degrees west of 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 Piscis Austrinus. Fomalhaut is positioned 14 degrees south-southeast of the southern radiant.

Delta Aquariids Radiants and Star Chart (credit:- freestarcharts)

Delta Aquariids Radiants and Star Chart - pdf format (credit:- freestarcharts)

What to expect in 2017

The best time to observe the meteor shower is during the early hours on the morning of July 29/30. Observers in the Southern Hemisphere and tropics should see a good show with the radiant high in the sky. For those at northern temperate latitudes, the radiant is lower down and therefore fewer meteors will be visible.

The Aquariids travel at a slow to medium velocity (41 km/s). As with all meteor showers, the trails often streak across the sky quite a distance from the actual radiant point; in many cases in excess of 30 degrees. It's therefore a good idea not to look directly at the radiant itself, but to scan a large area of the sky surrounding it.

Southern Delta Aquariids Data Table 2017

Meteor shower nameSouthern Delta Aquariids
Radiant constellationAquarius
ActivityJuly 12th -> August 23rd
Peak DateJuly 29th
RA (J2000)22hr 40m
DEC (J2000)-16d
Speed (km/s)41
ZHR 16
RatingFaint
Parent bodyUncertain but possibly comet 96P/Machholz
NotesAlso referred to as the Southern Delta Aquarids meteor shower

Comet 96P/Machholz Data Table (at epoch February 17th, 1994)

Name96P/Machholz
TypeComet
ClassificationJupiter-family comet (NEO)
DiscovererDonald Machholz
Discovery dateMay 12th, 1986
Aphelion distance (AU)5.94321
Perihelion distance (AU)0.12378
Orbital period (years)5.28362
Last perihelionJuly 14th, 2012
Next perihelionOctober 26th, 2017
NotesAlso known as Comet Machholz or 96P/Machholz 1. Discovery made by amateur astronomer Donald Machholz using 130mm binoculars