Krypton's core is made of uranium? (mathy types wanted)

[Captain Kal]

OK, guys, disregard my last muddled post on Krypton's uranium core and the adjustment to its radius.  I made the mistake of starting from the brown dwarf figure when I should just have used the vanilla calculations.

If we maintain the same proportionate density, then to double the gravity means eight times the mass with twice the radius.  Though the planet has 8 x more mass the distance to the core is doubled, and gravity obeys the inverse square law so the relative gravity is reduced by a factor of four.  8 / 4 gives us 2.

Following that same reasoning, a 35 G world with the same density as Earth would have 35 x the radius and 42,875 x the mass.  Clearly, this cannot be so since this would give a planet well beyond the brown dwarf range and it would be a small red dwarf star.  Hence, I adjusted my old figures based on the idea that a brown dwarf would be the max value for a planetary mass.

But we've specified a uranium core that suggests an overall density that's about 2.42 x greater than Earth's. (Uranium density = 19.1 g/cm^3 vs Iron density = 7.87 g/cm^3.)  That reduces the mass by that 2.42 factor to 17,666 x Earth's.

To achieve that 35 G gravity with that mass we divide 17,666 by 35 and take the square root of that.  That gives us a radius factor 22.46 x Earth's.  That's nearly 0.21 x the Sun's radius.

So, a uranium core implies a mass of 17,666 x Earth's, or 0.053 x the Sun's mass, and a radius 0.21 x the Sun's.

I knew intuitively the figures wouldn't be that different but it 's reassuring the math actually works out.

Hey, Gary, when you see this, do the double-check for me, please?  Thanks in advance.

[DakotaSmith]

Not to add another layer to what is already a complex problem, but ...

One of the things that jumped out at me in the Krypton Glossary is the fact that eighteen Kryptonian years is equal to 25 Earth years.  Basically, this means that by the time Earth has complete 25 orbits of the sun, Krypton had completed 18 of its primary.

All well and good, but when one takes into account the massive nature of the planet as calculated, one discovers that Krypton is screaming around its primary at a velocity unheard-of for a planet that massive.  By way of comparison, the massive planets of our own solar system orbit their primaries in periods better-measured by Earth decades.

This naturally brings to mind speculation about the distance between Krypton and its primary.  Krypton's primary must have been a red giant, after all -- meaning the star was far more massive than our own G-type yellow sun.  I don't know the math to check this, but I would have to assume that a planet that massive careening around its primary at that speed would have to be an inner planet, otherwise its velocity would overcome the gravitic pull of the primary and send it off into space.

Again, I don't know the math, but since you've calculated both the mass and size of Krypton, it might be interesting to know just how close it would have to be to the primary to keep from flying off into space.

The known factors in the equation are the mass of Krypton and its orbital period (one orbit of the primary every 1.3889 Earth years).  The unknown factor is the mass of Krypton's primary.  One could substitute the mass of a known red giant for Krypton's primary and see where the figures take you.

Dakota Smith

[Captain Kal]

Ah, DakotaSmith, you do know how to pose the tough questions, huh?

The figures would vary depending on the star Krypton was orbiting around.

If it were in our solar system, it would have to be 1.24 x as far from the sun than Earth is to have that orbital period.

The mass of the orbiting planet is largely irrelevant assuming the central star is the dominating gravitational partner.  Even for Jupiter and Krypton we can ignore their respective masses in the calculations.  What's important is the star mass and the orbital distance.

But we have to factor in the 'habitable zone' where liquid water could exist on a planet around a star.  I've already figured this out for Krypton in our solar system.  I'll have to ponder this some more for red dwarf and red giant stars to see what boundaries we can put on Krypton's orbit there.  It may be one or the other type of star may not be possible to both have that orbital period and be in the habitable zone.

I'll probably need a day or few days for this.

[llozymandias]

In the comics krypton's sun was a red giant.  It just strikes me as weird to think that the kryptonians would give their sun the same name as the "creator" of the universe.  I imagine this coming up when Lois (or any other reporter) interviews Kal.  Lois: What did the kryptonians name their sun?  Kal: Rao.  Lois:  Isn't Rao kryptonese for God?  Kal: It is.  Lois:  Why would your people name their sun after God?  Kal:  It's complicated.


     According to Maggin Kal's body has the density of white-dwarf-star-material.  Or something near that.  I imagine that the planet itself would be even denser.  Also keep in mind that super-matter seems to have anti-gravity properties.  Would a core of Uranium augment the heat krypton received from its sun?  If krypton were real, it would be interesting to see what it would really be like.

[Super Monkey]

It just strikes me as weird to think that the kryptonians would give their sun the same name as the "creator" of the universe.

No it's not, The Romans called Apollo "Phoebus".
Phoebus means Shining-one, it was also used by poets to describe the Sun.

[llozymandias]

In greco/roman mythology Apollo was not the "creator" of the universe.  Saying that something is weird, is not saying that it can't happen.  In reality people do weird things all the time.

[Super Monkey]

In greco/roman mythology Apollo was not the "creator" of the universe.  Saying that something is weird, is not saying that it can't happen.  In reality people do weird things all the time.

I never said he was, but both Apollo and Rao are Sun Gods.

Heck, most of the planets and moons in our very own solar system are named after Roman gods, least us not forgot!

So it would make sense to name their sun after their sun god.

[llozymandias]

Rao was only the name of a sun-god in ancient times.  When kryptonians became monotheistic Rao became their name for the creator of the universe; iow God.  In the silver-age (at least) krypton seemed a lot like an idealized Israel.  After Jaf-El's time Rao became kryptonese for God.


    Krypton should have had many civilizations & cultures coexisting.  At least in ancient times.  Kryptonians should have had many religions & mythologies.  Which means many pantheons of mythological gods.  Rao should have been only one of many sun-gods.  That kryptonian civilization would be so relatively homogenized almost from the beginning, weird.  Funny thing is the writers seemed to be of two minds about krypton's size.  On the one hand; they established that krypton's size was somewhere between 5xearth & jupiter. Otoh; most of their maps, geographies, & histories seem better suited for an earth-size planet. :roll:   That thing about 18 kryptonian years equalling 25 earth years also seems more suited for an earth-size planet.  Seems the writers (& editors) never imagined that krypton as a giant planet has more ramifications than just super-gravity. :twisted: