We are bounded in a nutshell of Infinite Space: Week 8: Reading #6: A
special kind of exoplanet
Within the realm of
extrasolar planets which have led to one of the greatest periods of extrasolar
discovery in recent time, there are a couple of key planet types which we, as
living beings who would be searching for a home soon enough (be it climate change
or ice ages or the Sun running out of fuel at the cause) would find very
interesting. These are the Super-Earths, planets found in the planetary search
the Kepler Space Telescope was commissioned to do, which have the unique
properties of being similar to Earth in some ways, but very different in
others. They are some of the only planets we have strong reason to believe they
have liquid water, while still being tremendously different to the Earth we’ve
inhabited for the past couple million years. These planets are incredibly close
to their star, so close that they usually have a steam-full, if not dominated,
atmosphere, partially the reason we are able to confirm they do have water, but
more on this in a second. Furthermore, the reason they are called Super-Earths
is how they are incredibly massive, more massive than Earth but less so than
gas giants like Saturn, as well as being made up of rock and gas. These Super
Earths are among NASA and JPL’s best guesses for habitable planets, considering
the new definitions of a habitable zone because of the existence of liquid
water on these planets. The habitable zone considers a certain distance from
the Sun at which liquid water can exist and be at a temperature we consider
“livable”, although this definition is rapidly changing with the onset of these
Super Earths and icy moons like Ganymede and Europa.
The means by which we are
now able to detect exoplanets is described by Maoz in chapter 2.2.4 of Astrophysics in a Nutshell, explaining
the process of taking the measurements of luminosities of a star to measure
whether the brightness dips at any point and thus indicates an obstruction, and
if this were sufficiently periodic and regular, there is a confirmation of the
planet’s existence. This technique in particular, although there are other
ones, allow us to measure the absorption and emission lines of the object
blocking the star, thus allowing us to understand its composition and possible
signs for compounds like water. This had led to discoveries like the Super
Earths, and most recently an Earth-like planet near a Sun-like star, the planet
being in the habitable zone. The NASA article reads:
July 23, 2015 -- NASA's Kepler mission has now confirmed the first
near-Earth-size planet in the “habitable zone” around a sun very similar to our
star. For more information about this latest discovery, visit: NASA’s Kepler
Mission Discovers Bigger, Older Cousin to Earth. NASA's Kepler Space Telescope,
astronomers have discovered the first Earth-size planet orbiting a star in the
"habitable zone" -- the range of distance from a star where liquid
water might pool on the surface of an orbiting planet. The discovery of
Kepler-186f confirms that planets the size of Earth exist in the habitable zone
of stars other than our sun. While planets have previously been found in the
habitable zone, they are all at least 40 percent larger in size than Earth and
understanding their makeup is challenging. Kepler-186f is more reminiscent of
Earth. "The discovery of Kepler-186f is a significant step toward finding
worlds like our planet Earth," said Paul Hertz, NASA's Astrophysics
Division director at the agency's headquarters in Washington.
Now all that’s left is to
visit these planets, someday.
References:
Maoz, D. (2007). Astrophysics in a Nutshell. Princeton: Princeton University Press.
http://www.nasa.gov/images/content/646920main_pia15622-43_946-710.jpg
http://ifa.hawaii.edu/~howard/ast241/exoplanet_properties.pdf
http://www.nasa.gov/ames/kepler/nasas-kepler-discovers-first-earth-size-planet-in-the-habitable-zone-of-another-star/
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