The heavens above Mauna Kea – Tales from Hawaii: Part 2

Mauna Kea is an enormous, exinct volcano on Hawaii’s Big Island, and one of the best places on Earth to do astronomy (if you ask them, the best one). In fact, the summit of the mountain hosts one of the world’s most renowned observatories. What makes it so special, other than that it looks like this?

Three of the telescopes on Mauna Kea’s summit. In the background, beyond the clouds is Maui (more than 100km away). CC-BY-NC-SA Carmen Romano

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Jazz and the atmosphere of exoplanets

The atmosphere of a planet holds the keys to make it habitable, so we need to look at them to figure if exoplanets are habitable. They are too far to send probes to measure them directly like we do with Mars or Jupiter’s moons, but scientists can study them from right here, looking at how they block light.

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What makes a planet habitable

A couple of days ago, NASA announced the discovery of seven-count-them-seven rocky planets orbiting a small star called TRAPPIST1. Three of them seem to even be in the “habitable zone”. So, have we found the aliens’ home?

Nope. However, words are a bit confusing, so let’s review what it takes for a planet to be habitable.

On planets too close to the star it’s too hot and water evaporates, on the far ones it freezes. Only those in the sweet spot stay just the right amount of wet. credit: NASA/JPL/Caltech

The key is liquid water. All life we know—from bacteria to cats, from carrots to Lionel Messi—hinges on chemical reaction that only take place in water. No water, no life.

The habitable zone of a star is the space around it where planets can have sustained liquid water on their surface. Closer, and the heat from the star will fry the planet with all the water (think Mercury), farther and the surface will freeze (think Pluto).

Now we need a surface to collect this water on. That’s why rocky planets are interesting: no rocky surface, no place for water. And again, no water, no life.

Location isn’t everything, though: the atmosphere is key too. Earth’s atmosphere keeps water on the surface, and temperatures friendly (for planetary standards). Less of it and we’d risk turning into Mars, which is in the habitable zone, but is a frozen desert, where water is more like a killer sludge. More atmosphere, and we might become Venus (also in the habitable zone), which is effectively hell, molten lead lakes and deadly acid rains included. Winds in the atmosphere also favor habitability on some exoplanets.

Then you must hold on to your atmosphere. Earth has a cozy magnetic field that deflects part of the Sun’s radiation. Mars probably had an atmosphere, when it also had oceans, but has no magnetic field. Atom by atom, the constant barraging of energy and particles from the Sun eroded it. With the atmosphere gone, so was the water. No water, no life.

How Google’s doodle portrayed the discovery

The planet discovered around TRAPPIST1 are important not because they might be habitable (though some are promising), but because TRAPPIST1 is the first star of its kind we study, and it immediately delivered several promising planets. That means it should be relatively easy to find interesting planets around that kind of star, which multiplies the chances of finding actually habitable ones.

Moreover, they are close to Earth (“just” 40 light years), so we can study their atmospheres with existing telescopes, or with the James Webb space telescope slated to launch next year. We’ll train on these for the multitude of planets we are about to find.

For now, as usual, no aliens.

If you want more
  • Do you remember what a fuss was made that time NASA found the first Earth-sized planet in a habitable zone? This time they were three at once.
  • NASA put together an impressive amount of information, graphics, and even an app. You can find everything here
  • The real star of the bunch is this phenomenal 360 video (fullscreen highly recommended!) of the view standing on TRAPPIST1d

Cover photo: CC0 David Mark/pixabay.com

No country for plasma TVs

There’s a beautiful country, with forests and deserts, vast salt lakes and tall mountains. A country where driving can be mortally dangerous. A country where your new plasma TV won’t last very long.

¡Bienvenidos a Bolivia!

A plasma screen is basically a bunch of small neon lamps. They work by passing an electric current through a container full of gas (like, you guessed it, neon!): the current excites the electrons and gets them to emit UV rays. The container is coated in fluorescent materials, which means that they convert UV light in visible ones.

Neon lights only need white light, whereas each tiny pixel in a plasma screen has a blue, a green and a red light, to form all the images of your favorite TV show.

Since we all like our high definition screens flat, the “lamps” inside them must be tiny gas cans, thin and rather fragile.

So, if the external pressure becomes too low, the gas expands and bends the walls of the can, making it harder for current to pass through. So the television has to work a lot harder, and the cooling system pays the biggest toll. The result is a very loud TV that ages really fast.

Normally it’s not a problem, since atmospheric pressure is basically always the same… at sea level.

But going up in altitude, pressure goes down. And many of the main Bolivian cities are so high up that plasma TVs don’t work properly.

 

Foto: Jungle and Mountains – Coroico, Bolivia, CC-BY-NC-ND Geee Kay, via Flickr. Some rights reserved