Yesterday I talked about how water can form on the Moon. It might seem a bit surprising that water exists on the Moon, but it doesn’t sound like a crazy idea. What does sound crazy is the idea that there is water on the Sun’s surface, and yet we know that there is.
Water from the Sun
The Moon is a dry, airless rock. At least that is how we imagine it. At basic level, that’s a pretty accurate description. It is drier than any desert on Earth, and its surface would be considered a hard vacuum. But at a more subtle level, that isn’t quite true. The Moon does have the faintest trace of atmosphere, consisting of elements such as argon, helium and hydrogen. The Moon also has traces of water on its surface, mostly locked up within minerals.
Water in the Sky
The transit method of exoplanet observation looks at the light from a star to observe dips in brightness. When a planet passes in front of a star (transits), it blocks some of the starlight, making the star appear slightly dimmer. Normally when we are looking for exoplanets we simply look for an overall dip in brightness, from which we can determine things such as the size of the planet relative to the star.
But once an exoplanet is known, you can begin to make more subtle observations, such as observing the dip at different wavelengths. This was done by a team recently to study the atmosphere of an exoplanet known as Gliese 1214 b. Their results were recently published in the Astrophysical Journal.
Cloudy with a Chance of Star
WISE J0855-0714 is a brown dwarf about 7 light years from us. Based upon its temperature, it is estimated to have a mass of about 10 Jupiters. The minimum mass to be considered a star is usually taken as 13 Jupiter masses, so this particular brown dwarf is either a very, very small star or (more likely) a very large Jupiter-type planet. That makes it either the 4th most distant star system or the closest known rogue planet. What we know for sure is that it is the coldest known brown dwarf, with a surface temperature of about 260 K (or 25 degrees below freezing for us Americans). It may also have a rather interesting atmosphere.
Land of Lakes
For the past week I’ve been in a remote part of northern Minnesota, vacationing at my Grandmother’s house. In that part of world you can pretty much throw a stick and hit a lake, which is part of the reason it is known as the Land of 10,000 lakes. Being in a region with so much water tends to give the impression that Earth is water-rich world.
War and Peace
When seen in the night sky, Mars is a burnt-reddish color. It’s sometimes brighter and sometimes dimmer as over the months and years it moves against the background stars. Sometimes it appears to stop along its starry path and reverse direction for a while, exhibiting what is known as retrograde motion. With its bloody color and strange motion through the sky, it is perhaps not surprising that it is named after the Roman god of war.
I’ll Drink to That
There’s a simple calculation that shows the average density of a black hole can be less than water.
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