August 14 – Three new Neptunian Moons (2002)

Neptune’s moons Neso, Halimede and Sau were all discovered on this day, in 2002. As with Laomedeia (see yesterday’s post), they were all named after the Nereids of Greek mythology. Their discovery pushed the number of known Neptunian satellites up to 13, but it’s now at 14 with the spotting of Psamathe the following year.
Neso is abount 60 km in diameter, and is the outermost of Neptune’s irregular satellites. Neso is thought to be the remnant of a larger body.

Halimede is a grey moon, 62 km across, and possibly a remnant from a collision involving the moon Nereid.

Sau is smaller, at about 42 km in diameter, and has a very inclined orbit.

Neptune from Voyager 2 (image: NASA)

Unlike most recent moon discoveries, today’s trio were found using the combined resources of two Earth-based telescopes: the 4 metre Blanco in Chile, and the 3. 6 metre Canada-France-Hawaii telescope on Mauna Kea, Hawaii. And because their discoveries centred on following tiny specs of light across the sky, I won’t be including any photographs. Instead, today’s picture is one taken of Neptune by Voyager 2 (which missed out on finding these three moons), showing cirrus-like clouds high above the beautiful windy planet.

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ALSO TODAY

Asteroid 111 Ate was discovered by C H F Peters on August 14th 1870. It is a main-belt asteroid, named after the Greek goddess of mischief and destruction. Being a Port Vale supporter I am familiar with her work. Ate is a C-type asteroid, and at an estimated 143 km in diameter, it is one of the larger.

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