Ice Planets Moving Within Their Star's Habitable Zone Will Skip Habitability

It's bad news for Arthur C. Clarke today. Computer models now suggest that moons or planets composed mainly of ice that warm up as their star becomes more luminous with age will not become nice places to live.

It made a lot of sense, really. Oh, warm up the giant ice cube, then you've got a bunch of water. Unfortunately, it takes more energy to melt a planet covered in ice than what the Earth receives, and by the time the ice does melt, the combo of reduced surface albedo (how reflective the surface is), increased solar radiation, and water vapor's status as a potent greenhouse gas would lead to a very quick runaway greenhouse effect. You'd go from Europa to Venus in no time at all.

So for any monoliths hanging around, don't go transforming Jupiter into a star to help out that native Europan life. Turns out, they're better off as they are.

In completely unrelated news, my review for Atlantic City Country Club is coming along nicely, and it'll be done before the end of the month. Here's a little teaser of the sort of course we're dealing with.

Even if I hadn't been playing from the back tees, I would have on that hole.

Anyway, I'm going to make a commitment to doing a golf course review once a month from now on. I enjoy playing new golf courses, I enjoy taking pictures of golf courses, and I enjoy writing about them. Maintaining that schedule might get dicey over the winter, so hopefully I can build up a backlog so I don't have to go roaming for warm weather on the last weekend in January.

Exoplanets Around TRAPPIST-1

Yeah, you've probably heard the news already. It's been everywhere. Recently, scientists announced the discovery of a seven planet system orbiting the red dwarf TRAPPIST-1, all of which are Earth sized and likely made of rock, and three of which are solidly in the habitable zone. What makes this system especially inviting for future study is the dimness of the star. TRAPPIST-1 is tiny and incredibly faint, the midday sky on the orbiting worlds would only be as bright as the sky at sunset on Earth. Most of the heat comes in infrared, and any plants on the surface would be black instead of green. There may very well be habitable planets, but they won't be like Earth.

Anyway, a dim star makes it much, much easier to study the orbiting planets. Planets glow, but not by much, and they pale in comparison to their stars normally. It's like trying to study a firefly floating next to a floodlight from a mile away. It's difficult. But here, instead of a floodlight, we have a 60 watt bulb. It makes life that much easier.

Anyway, I'm sure we'll be hearing more about the TRAPPIST-1 system in the future, especially when the James Webb Telescope goes up in 2018. But for now, we'll just have to imagine what standing on some of those worlds would be like.

Big News for Exoplanet Enthusiasts

It's one thing whenever Kepler finds a potentially habitable exoplanet around a star several hundred light years away. That's cool, but there's nothing we can realistically do about it. The technology to move things fast enough to get that far in human amounts of time doesn't exist, won't exist anywhere in the near future, and is barely even theoretically possible outside of your crazier fringe physics. Those planets will most likely remain mere curiosities for the rest of our lives. It's another thing entirely when we find a potentially habitable exoplanet orbiting the star Proxima Centauri, which if you couldn't deduce it from the name, is the Sun's closest stellar neighbor.

Credit: ESO/M. Kornmesser

Now, this is no slam dunk, "oh, it's definitely Earth 2.0" moment. The habitability of planets orbiting red dwarfs has always been in dispute, and the Proxima Centauri system features many of the red dwarf flaws. Proxima Centauri b orbits just 4.7 million miles from its star, which is okay since Proxima Centauri is a wet match compared to the Sun's 60 watt bulb, but it does mean that the planet will be tidally locked, either showing only 1 side to its sun or, if we're lucky, in a 3:2 resonance like Mercury (3 planetary rotations for every 2 orbits). If Proxima Centauri b is tidally locked in a 1:1 resonance like the Moon is, it means that one side of the planet will be constantly in the sun, and the other will never see sunlight. An atmosphere mitigates most of the vast temperature differential this situation causes, but we're not sure a planet formed in these conditions can maintain an atmosphere, which brings us to our second problem.

Many red dwarfs have issues with solar flares. They shoot off big, powerful flares at a much higher rate then the Sun does. Proxima Centauri has this issue, and as a result, Proxima Centauri b currently experiences high level radiation 100 times more intense then Earth currently does. A powerful magnetic field would protect the planet, but we don't know if it has one, or if the solar flares were even more intense earlier in the star's history. It's possible intense solar radiation stripped the planet of any atmosphere when the the planet was young, and there's nothing there now but barren rock.

So, what should you take away from this? First, anyone who says we found a new Earth right next door are wrong. We don't know what this is, and even if it does turn out to be habitable, it won't be anything like Earth. Habitable doesn't necessarily mean pleasant, and I can pretty much guarantee that life on Proxima Centauri b would be hard, for us or for native life. Plant life would be black instead of green, since most available light would be in the infrared rather then risible spectrum, and high winds would constantly blow from where the sun is directly overhead towards the night side. But you know what? If Proxima Centauri b does turn out to be this hard-scrabble, bleak world where life has to struggle to get by, it would still be the discovery of the century. I hope it works out, I really do, but let's wait until we get more information before we start planning a trip out there.