Thursday Throughput: Arrakis, New Caprica, and Us

Fictional Solar System diagram of the Arrakis Star System as depicted in the American novel Dune. The diagram is done in the style of traditional High School text books. Photo by D A R C 12345 via Wikimedia Commmons

[ThTh1] So last week, Will suggested I start a new feature on the Throughput called “Ask An Astronomer”. I’ve done something like this before as a graduate student. The notion is that you guys would post questions and I would answer one I found interesting each Throughput. The first question was provided by Will but if you have a question you’d like answered — and not just on astronomy but on science in general — post it here, DM me on Twitter, send up smoke signals. Whatever you like.

The question this week:

In Battlestar Galactica, the refugees find a semi-habitable planet they call New Caprica. It’s only habitable along its equator, though, and even there it is evidently cold. On Planet Earth we have large swaths of land that are not habitable due to low temperatures and nothing that is not habitable due solely to high temperatures. So my question is whether or not there are reasons why this would need to be the case. Could a planet develop life at the polls and be uninhabitable in between? How high would the temperature have to be to be uninhabitably warm? What would it look like? Extra-barren desert?

We don’t know a lot about planets. Well, we know a lot about our planet but not a lot about others. However, New Caprica crosses me as reasonable. Earth has gone through long ice ages where the northern climes were entirely buried in thousands of feet of ice and the only inhabitable regions were near the equator. If Earth were currently a little further out or the Sun were a little colder or our atmosphere had less carbon dioxide, we would be in that state right now.

As for the opposite situation, this is basis of the book Dune. The planet Arrakis is only inhabitable at the poles because the rest of the planet is scorching desert. Frank Herbert was an avid ecologist and his planet was set up to reflect a realistic idea of what a desert planet might be like. Nothing in it crosses me as unreasonable. If the Earth were a little closer to the Sun, that could raise temperatures so that the equatorial regions became deserts and Antarctica became prime real estate (you might remember that I joked about this a few weeks ago when talking about Trump’s plan to buy Greenland). Indeed, some science fiction writers thought Venus might be like that until we explored it and found out that its thick carbon dioxide atmosphere makes the entire planet a scorching desert.

In the decades to come, we’re going to learn a lot about alien planets. It would not surprise me at all if we found ones like New Caprica or Arrakis.

[ThTh2] And since this is the debut of this feature, I’ll answer Will’s other question:

Could you have two planets orbiting the sun at a relatively similar distance from it? Apart from some physics reason that wouldn’t happen naturally, the most important thing I assume is that they don’t get too close to each other for gravitational forces to set in (which would happen eventually if they were orbiting at different speeds). So what would need to be the case for them to orbit the sun at the same speed? Similar size? Luck? Thrusters and alien engineering?

You can. There are five points in a planet’s orbit called Lagrange Points where the gravitational force of the Sun and the planet balance perfectly. Jupiter’s L5 and L4 points — called the Trojan points — are host to over a million asteroids that sit in that balance point. You could, in theory, have three planets in the exact same orbit separated by 60 degrees.

Planets that are near in orbit but not identical might be a more complicated situation. The could potentially alter each other’s orbits and even kick one of the planets out of the system, depending on how things work out. But we know this happens in nature. The TRAPPIST 1 system has seven planets in the “habitable zone” between 1.7 and 9 millions kilometers from the primary star.

[ThTh3] And speaking of planets … a new paper has analyzed the results of the recent planet searches and concluded that planets are extremely common in our Galaxy.

[ThTh4] The equinox was this week, which means we’ve officially moved from summer to winter. And no, balancing an egg doesn’t get any easier on the equinox than any other day.

[ThTh5] A new summary concludes that the oceans are warming faster and rising faster than previously thought, with sea level rise projected to reach 17-33 inches by the year 2100. I’ll have a post soon on why I think trying to panic people about global warming is irresponsible. But “we need to look at this realistically” works both ways. We shouldn’t panic-monger; but we shouldn’t deny either. This is a big challenge. And even under the best-case scenarios, we are going to need some adaptation to protect people from flooding.

[ThTh6] Who knew that bird migrations were so beautiful?

Incredible visualisation: Birds migrating across Europe, tracked by GPS. pic.twitter.com/PjUS07M5z4

— Steve Stewart-Williams (@SteveStuWill) September 21, 2019

[ThTh7] One bit of research I was involved in was the exploration of Tabby’s Star. This star showed unusual drops in its light output and got a lot of attention when there was some speculation that this would be consistent with what one might see from an alien mega-civilization. Sorry for the awkward phrasing, but it’s hard to convey what actually happened which was that an astronomer who does serious work on how we might actually detect aliens noted that the behavior of Tabby’s star was similar to what we might see. Which led the press to claiming we’d detected aliens. In the end, the most likely explanation is a dust ring encircling the star. If this result — claiming to have found a number of Tabby’s stars — is confirmed, that would lend a lot more credence to the dust ring scenario.

There is a lot of debate about the search for alien life in astronomy circles and I think Tabby’s Star, while it turned out not to be aliens, is an indication of the way forward. Figure out how stars or galaxies with alien civilizations might look different from ordinary stars and galaxies; comb databases for objects that resemble that; study them carefully because, even if you don’t find aliens, you’ve found something unusual and interesting. Tabby’s Star wasn’t aliens. But it was something cool and interesting. And as a result of studying it, we know more about the Universe than we did before.

[ThTh8] [Update] Decided to add this post-publication. The headlines are screaming “Galaxies are dying!”. But you can read here what the real story is. Galaxies in clusters are having their star formation “quenched”, abruptly ended by either ram-pressure stripping or being deprived of gas. This doesn’t mean the Galaxy is “dead” — the stars that are there will continue to shine. But it won’t form new stars. We’ve known about this for some time but a new project is trying to figure out exactly ho this works.