Tuesday, August 30, 2016

NEREID, THIRD LARGEST OF NEPTUNE’S MOONS (M18.69) Taken by Dennis Simmons on August 28, 2016 @ Brisbane, Qld, Australia

Using the NASA (JPL) Horizons system (http://ssd.jpl.nasa.gov/horizons.cgi), I generated an ephemeris for Nereid covering 27th to 28th August 2016 and plotted the calculated positions in The Sky X Pro, to determine the location of this faint mag 18.69 satellite of Neptune.

The attached images were taken using a Tak Mewlon 210, Tak x0.8 Reducer/Flattener and an ATIK 414 EX camera. I captured 75x60 sec frames on 27th Aug and 37x120 secs on 28th Aug. Images were calibrated, aligned and stacked using CCDStack2 and finished in CS6.

The full size originals have a FOV of 15.2 x 11.3 arcmin at 0.65 arcsec/pixel. The 1024x768 crops have a FOV of 13 x 9.7 arcmin.

Nereid is the third largest of Neptune’s moons, and the second to have been discovered. It was discovered on 1st May, 1949 by the Dutch American astronomer Gerard P. Kuiper (for whom the Kuiper Belt is named) using photographic plates from the McDonald Observatory in Fort Davis, Texas. It is named after the numerous daughters, called Nereids, of the sea god Nereus in Greek mythology.

Almost everything we know about Nereid comes from the images taken by Voyager 2 in 1989; its closest approach was approximately 4.7 million km.

Nereid has a diameter of about 340 km (210 miles). It revolves around Neptune with a period of just over 360 days in a highly elliptical orbit—the most eccentric of any known moon—that is inclined by more than 7° to the planet’s equator. Its mean distance from Neptune is 5,513,400 km (3,425,900 miles), which is about 15 times farther from Neptune than Triton. Nereid is exceedingly faint, making observations with even the largest Earth-based telescopes very difficult.

Neptune now has 14 recognized satellites, and in honour of their parent planet, all are named for minor water deities in Greek mythology.

I have also included a 800x600 pixel animation to reveal the orbital motions of Neptune, Triton and Nereid.



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