Thursday, 1 September 2016

Jupiter’s moon Amalthea

Jupiter’s moon Amalthea

Helena Puumala’s SF Romance series features a planet with seven moons.  This rather unusual setting gives me the opportunity to talk about some of the remarkable moons in our solar system, as I test different moons for the cover of book 2 of the series.

But, more on that at the end of the blog.  Basically, the book gives me the opportunity to do a mini-tour of some of the major moons of our solar system.

This blog is about Amalthea, one of smaller inner moons, which is to say, inside the orbits of the four big Galilean moons (Io, Europa, Ganymede, and Callisto).  Of course, when you are in between giant Jupiter and its dramatic large moons, you are bound to be overlooked.  So, let’s give little Amalthea a bit of attention.

Here are a few facts about Amalthea, courtesy of Wiki:

  • It was discovered in 1892 by Edward Barnard (of Barnard’s star, among other achievements), and was the last satellite to be discovered by purely visual observations (i.e. not photographic analysis).
  • It's the biggest of the inner moons, at 250 km by 146 km by 128 km.  That’s far smaller than the Galilean moons, which are in the 1500-2500 km range (radius).  It is the largest of the inner satellites, though.
  • As you can see by the dimensions noted above, it is too small to have “collapsed” under its own gravity, and thus is not spherical.
  • It is very close to Jupiter, at only 181000 km.  Jupiter would be huge in the sky there, subtending over 45 degrees of arc.  That would be about one-quarter of the visible sky, assuming that you were on the Jupiter side, of course.
  • Naturally, Jupiter would appear bright, though no brighter than  our moon, in brightness per surface area.  However, it would be about 900 times bigger, so even when it was night-time on Amalthea’s sub-Jupiter point, the sky would be pretty bright.  I think you could easily read a newspaper, in the short time you had before the radiation levels caused by being so close to Jupiter would kill you.
  • It has a greater eccentricity and inclination to its orbit, than is expected for a close-in object (those usually circularize) – this is a result of gravitational interactions with the Galilean moons. 
  • It is reddish in colour, as the first Voyager photos, from 1979, showed.  It is not known for sure what causes this colour, though sulphur is a likely candidate.
  • It is tidally locked, so that one side always points to Jupiter (the long side of the ellipsoid).
  • It was first assumed to be quite rigid, but measurements by Galileo indicates that it is actually less dense than water.  So, it is thought that it must be made up of ices, and is probably quite porous.  It may also contain organic materials (i.e. carbon).
  • This would indicate that it formed far from Jupiter and was captured and/or migrated to the current close-in orbit (else the heat of Jupiter’s formation would have melted it).
  • It may have tiny moonlets orbiting it.
  • Voyager 1 and 2 took pictures in 1979, as well as other measurments.  Galileo also studied it.
  • A 2005 article said (I hope it is still true):
    It is possible that the imager may also be able to provide images of some of Jupiter's closest moons, including Io and Amalthea.”

Here's a picture of Amalthea, taken by the NASA Voyager 1 probe.

This is colour representation of Amalthea.  Quite red, perhaps embarrassed by all the attention.


And here’s a simulated view of Jupiter, from Amalthea, by “Planetuser” on Wiki:

Some more views from Galileo:



And here’s the most recent (Aug 29, 2016) photo of Jupiter, from the Juno probe as it nears the planet, on its very elliptical orbit.  Amalthea is down there somewhere:



The moon Amalethea and Love and Intrigue Under the Seven Moves of Kordea

Helena Puumala's SF Romance series features the planet Kordea, home to a race of beautiful and powerful psychic aliens, known as the Witches of Kordea.  The planet has seven moons, an extraordinary arrangement for a terrestrial sized planet in its star's habitable zone.

In fact, the moons of Kordea are a central element in Book 2.  The cover below actually borrows the moon Amalthea, one of the moons of Jupiter 

The Witches’ Stones Series

The Witches' Stones, Book 1 - Rescue from the Planet of the Amartos

Young Earth woman and spaceship mechanic, Sarah Mackenzie, has unwittingly triggered a vast source of energy, the Witches' Stones,  via her psychic abilities, of which she was unaware.  She becomes the focal point of a desperate contest between the authoritarian galactic power, known as The Organization, and the democratic Earth-based galactic power, known as The Terran Confederation.  The Organization wants to capture her, and utilize her powers to create a super-weapon; the Terra Confederation wants to prevent that at all costs.  The mysterious psychic aliens, the Witches of Kordea also become involved, as they see her as a possible threat, or a possible ally, for the safety of their own world.

A small but fast scout-ship, with its pilot and an agent of the Terra Confederation, Coryn Leigh, are sent to rescue her from a distant planet at the very edge of the galaxy, near space claimed by The Organization.  Battles, physical and mental, whirl around the young woman, as the agent and pilot strive at all costs to keep her from the clutches of the Organization.

The Witches' Stones, Book 2 - Love and Intrigue, Under the Seven Moons of Kordea

Sarah has taken refuge on the planet of Kordea, where she is also learning how to control her psychic abilities, through the tutelage of the Witches of Kordea.  Coryn Leigh has now taken up the position of Confederation diplomat to the Kordeans, but he is also charged with keeping the Mackenzie girl safe at all costs.  During their time on the planet, an attraction between them grows, though they try to deny it, to themselves and each other.
But The Organization has plans of its own, including threatening the destruction of the planet Kordea, via destabilizing the orbit of Lina, one of its many moons.  The Organization proves that its threats are in deadly earnest, so, ultimately Sarah, Coryn and the Witches of Kordea must take the fight to the enemy.  Thus is borne a dangerous mission, to  a planet where their foe has based the weapon that threatens Kordea, and ultimately, the balance of power throughout the galaxy.  Sarah and Coryn agree that the machine must be destroyed, even at the possible cost of their own lives and growing love.

The Witches' Stones, Book 3 - Revenge of the Catspaw

Sarah and Coryn have become married, under the traditions of the Witches of Kordea.  But the marriage is performed by the Eldest of the most important coven, a rare honour, that comes with a blessing and a curse.  The slow working out of this blessing and curse forms the backdrop to the story.

Having come so close to their goal of enhancing their weaponry via Witches' Stone power, The Organization will not give up.  In order to lure Sarah into their trap, and thus have her become their Catspaw (someone who is forced into helping another, against their will) they need bait, and Coryn becomes the bait.  He also comes under the domination of a particularly nasty Elite of The Organization, one "Evil Evilla" Copoz.

Sarah, and a picked group of companions, must re-enter The Organization space, this time to the very heart of the empire, to rescue her husband, as he has done for her in the past.  They do so at great peril, but nothing can stop the terrible Revenge of the Catspaw.

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