Podcaster: Richard Drumm
Title: Space Scoop: Is Earth Special?
Organization: 365 Days Of Astronomy
Description: Space scoop, news for children.
In an exciting discovery, water vapor has been found in the atmosphere of a distant exoplanet planet known as K2-18b, which is 110 light years from Earth in the constellation Leo.
Yet scientists have been flocking there for the last 8 years, because it’s one of the best places to go to answer a mystery: What shoots beams of tiny, almost undetectable particles at Earth?
Bio: Richard Drumm is President of the Charlottesville Astronomical Society and President of 3D – Drumm Digital Design, a video production company with clients such as Kodak, Xerox and GlaxoSmithKline Pharmaceuticals. He was an observer with the UVa Parallax Program at McCormick Observatory in 1981 & 1982. He has found that his greatest passion in life is public outreach astronomy and he pursues it at every opportunity.
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This is the 365 Days of Astronomy Podcast. Today we bring you a new episode in our Space Scoop series. This show is produced in collaboration with Universe Awareness, a program that strives to inspire every child with our wonderful cosmos.
Is Earth Special?
In an exciting discovery, water vapor has been found in the atmosphere of a distant exoplanet known as K2-18b, which is 124 light years from Earth in the constellation Leo.
Researchers from UCL, University College London, used the Hubble Space Telescope to peer inside the atmosphere of planet K2-18b. They found promising signs of water vapor, hydrogen and helium in the planet’s atmosphere.
The exoplanet crosses in front of its host star as seen from Earth. This is called a transit and the planet was first discovered by the Kepler Space Telescope.
This is how the astronomers were able to detect the atmosphere. As the planet transited the star, a small portion of the star’s light went through the planet’s atmosphere and was changed by the atoms & molecules it encountered there.
The spectroscope on Hubble was pushed to its limits and detected the tiny changes.
The exoplanet is approximately 8 times the mass of Earth, making it a so-called “Super Earth”.
This is an exciting find because these are some of the common elements that we find here on Earth.
Water’s H2O molecules had been found in interstellar gas clouds back in 1969 by radio astronomers, and this water vapor finding adds yet another example of water found in the galaxy.
So, is Earth special?
Well, Earth is special in that it has life. Intelligent life at that.
But the oceans of water we have here appear to be not all that uncommon. There are moons of Jupiter & Saturn that have liquid water oceans, albeit under kilometers of ice.
Water can exist on K2-18b because it orbits its star at the right distance to make it possible for liquid water to exist. Remember, though, water vapor was detected, not liquid water.
If the planet was too close to the star, the water would boil away, and it would freeze solid if the planet was too far from the heat of its star.
Even though this planet has water vapor in its atmosphere, K2-18b is likely not a place you’d want to live.
- At 8 Earth masses, this planet is much more massive, with crushing gravity,
- almost certainly it has a different atmosphere, with no oxygen, and
- it orbits a red dwarf star.
Red dwarf stars are the most common type of star in our galaxy, but are probably not very good stars for us to consider habitable. They spit out radiation and gigantic solar flares.
They do last a long time, though. They are fully convective, which means that they don’t have the same layers as our Sun. Just the one convective layer where the entire contents of the star are mixed thoroughly by convection currents.
As a result, they don’t accumulate helium, uh, “ash” so-to-speak in their cores. Almost all the hydrogen in them is available for fusion into helium.
A .1 solar mass red dwarf will support nuclear fusion for 10 trillion years. The host star here has almost 1/2 solar mass, so it’ll run out of fuel somewhat sooner.
It’ll go through the red giant stage, followed by the usual blue dwarf & white dwarf stages of development.
The exoplanet has a 33 day-long “year” so it’s probably tidally locked to its star, much like the Moon keeps one side facing Earth. This would mean that one side will be much hotter than the other.
The atmosphere, however, will moderate temperatures a bit, allowing some of the heat from the sunlit side to transfer to the dark side.
The planet’s equilibrium temperature is around 17*F or -8*C, but the presence of an atmosphere tells us that the actual surface temperature will likely be higher. The greenhouse effect, you know.
So if there’s enough water present on the planet, there may be liquid water on the surface of the sunlit side and ices or snow on the dark side.
The water vapor we detected in the atmosphere may well come from very hot pools of surface water on one side of the planet. The vapor would be carried by the winds and likely fall as snow on the other side of the world.
Or it might be dry on the rocky surface and the only water is the vapor in the atmosphere.
It might also be that it’s a gas covered mini-Neptune planet with no surface at all. We just don’t know. Maybe the JWST can show us more. IF it deploys properly, that is.
So, to recap:
The star is nothing like our Sun. Nothing at all.
The planet is nothing like our Earth. Nothing at all.
Cool to think about, though!
End of podcast:
365 Days of Astronomy
The 365 Days of Astronomy Podcast is produced by Planetary Science Institute. Audio post-production by Richard Drumm. Bandwidth donated by libsyn.com and wizzard media. You may reproduce and distribute this audio for non-commercial purposes. Please consider supporting the podcast with a few dollars (or Euros!). Visit us on the web at 365DaysOfAstronomy.org or email us at info@365DaysOfAstronomy.org. This year we will celebrates the Year of Everyday Astronomers as we embrace Amateur Astronomer contributions and the importance of citizen science. Join us and share your story. Until tomorrow! Goodbye!