You've probably noticed, if you've played Grand Theft Auto V, that the persistent virtual day–night cycle is just a little faster than our own. One hour in GTA V time is two minutes in real life. One year in GTA V is 17,520 minutes, or 292 hours, or a little over 12 days. That has some basic implications, like, say, if you take 35 hours or so to beat the game, you've played about a month and a half of "GTA time." A 25-year-old man like Franklin, with a life expectancy of 79 years, would have approximately 648 real-world days to live, or less than two real-world years. Nico Bellic, it goes without saying, is long dead. More broadly, that means that the planet on which GTA V takes place orbits the sun — or some star — every 12 days. That's more than seven times faster than the closest planet to the sun, Mercury, which circles the sun every 88 days. This got us to wondering: Where, exactly, would this mystery planet that orbits the sun be? What would it look like? Could planet GTA actually exist?

Caleb Scharf is the director of astrobiology at Columbia University. Here's what he told us about the location and composition of planet GTA, if planet GTA existed in our solar system: So, to orbit our Sun every 12 days means the planet would need to be about a 10th of the distance from the Sun as the Earth currently is (from Kepler's laws), or about 0.1 astronomical units in radius [1 Astronomical Unit = 92 955 807.3 miles].



This is inside the orbit of Mercury (whose orbit is roughly 0.39 astronomical units in radius). That's a brutal place to be. My very crude estimate of what the surface temperature would be (keeping everything else about Earth the same, like its absorbency of radiation): 1,200–1,300 Fahrenheit — pretty toasty. That's the melting point of aluminum and twice the melting point of lead (so much for bullets).



In terms of composition, there would be no surface water (obviously!), rock, and metal ores on the surface. If there was an atmosphere it'd be pretty nasty — I suspect a lot of evaporated minerals/metals, etc., and a very nasty radiation environment this close to the Sun.

Josh Peek is a postdoctoral Hubble fellow at Columbia, and he was kind enough to find a planet meeting this description in a map of exoplanets (planets outside our solar system) discovered by the Kepler space telescope. It has the awesome-sounding name of Kepler-29b, and here is what we know about it:

So, Kepler-29b orbits a sunlike star, and fits the orbital requirements for planet GTA. One problem: According to the Extrasolar Planet Encyclopedia, the surface temperature is approximately 1,000 degrees Fahrenheit, as Scharf predicted.

OK, so planet GTA, in our solar system, or a solar system like ours, would be a tough place to live. BUT! That's assuming the residents of planet GTA have not figured out a way to deal with the heat of the sun and terraformed the planet into a lovely place (classic assumption). Here was Scharf's best idea for cooling the surface: Well, you could construct some kind of orbital shade out of partially transparent material — e.g., quartz doesn't melt until 2500°F — but you've got to cut about 99% of the solar light to get back to Earth like heating! Those are some pretty heavy-duty sunglasses. Peek had few ideas too: The easiest way to solve this problem would be to make it orbit a much smaller (and therefore dimmer and redder star) which puts out much less energy. I am not sure how you would mitigate that kind of influx of energy — maybe paint the whole planet white to reflect most of the light? I am kinda at a loss — planets that close to sunlike (G-dwarf) stars are out of the "goldilocks" zone — they have ~100 times the energy input that we get from the Sun. So! Either a giant quartz orbital shade or painting the planet white or jogging planet GTA over to another star.

Let's work for the time being with that assumption, that planet GTA, an Earth-like planet with no galactic Ray-Bans, moved to another star, and maintained its 12-day year. What would this star look like? Caleb Scharf figured it out. This was tough to work out, but I think I've got it about right — the issue is that small mass stars are fainter, but since they're less massive, the 12-day orbital period location changes too. To maintain roughly Earth-like conditions, but have a 12 Earth-day-long year, you'd need your planet to orbit a star one-tenth the mass of the Sun (such things exist, they're called M-dwarf stars) at about 0.03 astronomical units, so roughly 33 times closer to the star than the Earth is to the Sun. And that star is overall about 1,000 times less luminous than the Sun, and also much redder, it would not look like the Sun. Much redder than our sun, eh? Well, wait just a minute!