Astronomy Quick Facts – Ananke

Ananke is a small retrograde moon of Jupiter, and is a member of the Ananke group of moons. This group consists of retrograde irregular moons that orbit at a high inclination. Ananke’s also known as Jupiter XII. It was discovered in 1951 by Seth Barnes Nicholson at Mount Wilson Observatory.

Image copyright OHP/CNRS/IMCCE. Used under Creative Commons license from Wikimedia.


  • Mean radius: 14 km
  • Mass: 3.0×1016 kg
  • Density: 2.6 g/cm3 (estimated)
  • Surface gravity: 0.010 m/s2 (0.001 g)
  • Albedo: 0.04 (estimated)
  • Temperature: 124 K (-149°C)
  • Mean orbital radius: 21,280,000 km
  • Orbital period: 610.45 d
  • Inclination: 149.9° (to Jupiter’s equator)
  • Eccentricity: 0.24

Name Origin

Ananke was the personification of destiny, necessity, and fate. She is the mother of the Fates, whose father is Zeus. She’s a rather powerful figure in Greek mythology, being in total control of fate.

5 Interesting Facts

1. Ananke got its name in 1975. However, it was known as Adrastea from 1955 to 1975, which is the name of another moon of Jupiter.

2. Ananke is the largest member of the Ananke group, which may have been formed from the breakup of a larger moon.

3. It appears to be light red in the visible spectrum.

4. The infrared spectrum indicates it possibly has water (ice).

5. With a surface area of approximately 2,500 km2, it’s about the same size as Luxembourg.

This is a rather small satellite, and Galileo wasn’t able to get a picture of it. It’s a very minor target anyway, and orbits quite far from Jupiter.

Solstice – Summer Goals

It’s June 21st, which means it’s the Summer Solstice! First day of summer. It’s also my last summer in Japan. Summer is going to mean a few things, and I have some goals.


I am currently reading a couple books that will take far too long to finish. I would like to find more time to read, preferably at home, maybe at night after everyone else has gone to bed.  That means I need to streamline my blog posting process.  However, my best posting times are at night, as I have more time to write the posts. But that’s for another section of this post. I’ll try as much as I can to read during breaks at work, as well as on the train to and from work, and make time to read at night.


I’ve been able to keep up with my two posts a day commitment. Not one day has been missed so far this year. I will continue with that for the rest of the year, not only summer.  I’m also going to start up a new blog about architecture and urban photography. Other things to look forward to are more worldbuilding posts. I also plan to get started on Quick Facts, which is basically a renamed Encyclopedia Entries. I’ll get the astronomy section organised, as well as start up the geography and palaeontology sections.


After a successful A to Z Challenge in April, I slacked off. Mainly due to visa sponsorship application forms and things like that. I must get back into writing, at least 15 minutes a day. More on days I’m home alone.

Other things

Prepare for my sister’s visit in October. I won’t take any time off at Obon in August, so I’ll try find shifts in other schools that are open for this holiday period. I want to save up my paid holidays for my sister’s visit. I also want to go out quite a bit with my daughter, such as the beach and more splash parks. She needs to get fully diaper trained. She knows what to do, she just doesn’t let us know she needs to use the toilet. Got to work on that.  I’d like to install The Sims 3 on my computer, as I haven’t actually played any games on it since my old computer decided to die on me. My favourite game, SimCity 4, is difficult to install thanks to my daughter, who got her grubby, sticky, slimy hands on the CD and made it very difficult clean off.

What are your summer plans (or winter, if you’re in the southern hemisphere)?