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Among 5000 Known Exoplanets, There Are Some Really Strange Ones

Planets so strange that they prompt a rethink of the “planetary rulebook.”

PBS tells us that Hoth, the frozen planet in Star Wars, is not just imagination. It has a real-life counterpart among the exoplanets. Granted, astronomers call it OGLE-2005-BLG-390Lb but even they think of it as “Hoth.”

Here’s the video.

Such strange planets are prompting a rethink of the “planetary rulebook.” Another strange one:

Narrator: 51 Pegasi b is a gas giant, around half the mass of Jupiter, but so close to its star that part of its atmosphere may have been ripped away…

Hannah Wakeford: These planets are baked by their stars’ radiation, the temperatures are in the thousands. David Charbonneau: Many astronomers didn’t believe it, because the planet was in the wrong place. It was enormous. It was massive, and yet it was parked right next to its star …

Jayne Birkby: The discovery of 51 Peg meant that we had to tear up the rulebook.

Space &Flight, “Yes, There’s Really a Frozen Exoplanet named Hoth” at PBS (November 15, 2021)

Astronomers had expected to see solar systems like our own but instead they demonstrated that there are other types of solar systems out there. Whether these exoplanets could host what we think of as life is another question.

Here’s a list of ten of the strangest ones, including

HD 209458b: Osiris This planet boasts a number of first discoveries. Scientists have found that it is the only planet currently found outside of the solar system to have detectable oxygen and carbon in its atmosphere. Its parent star is 150 light years from Earth in the Pegasus constellation. Named after the Egyptian god who lost part of his body, Osiris revolves around its sun a mere 4 million miles away.

The scorched planet is evaporating at such a fast rate that scientists have begun to create a new classification of exoplanets called chthonian planets. This nomenclature comes from the infernal Greek deities and H.P. Lovecraft’s subsequent usage for his space monsters. It is most likely a dead core of a completely evaporated gas planet.

Mike Colagrossi, “10 of the strangest exoplanets in the universe” at Big Think (July 8, 2018)

But what about planets that might harbor life?

Kepler-16b: Tatooine Astronomer’s research once posited about the possibility of a circumbinary planet – that is, a planet that circles around two stars. In an homage to Luke Skywalker’s home planet in Star Wars, Kepler-16b is nicknamed Tatooine. Whereas Skywalker’s homeworld was habitable, this planet is cold, gaseous and most likely cannot harbor life.

It is 200 light years away from earth. The discovery of a circumbinary planet was hinted at and then confirmed with the observation of brightness of the dual star system being dimmed by a planet’s transit in front of it. While being in the habitable zone is ruled out for this planet, Kepler’s principal investigator William Borucki on the importance of this discovery stated:

“This discovery confirms a new class of planetary systems that could harbor life… Given that most stars in our galaxy are part of a binary system, this means the opportunities for life are much broader than if planets form only around single stars. This milestone discovery confirms a theory that scientists have had for decades but could not prove until now.”

Mike Colagrossi, “10 of the strangest exoplanets in the universe” at Big Think (July 8, 2018)

Sky at Night Magazine offers a different list. Their first choice is

HD 189773b – where it rains glass sideways

This nightmare world is only 64 lightyears away and the closest ‘hot Jupiter’ to Earth. It may look like a gorgeous deep-blue marble floating serenely in space, but if you had the misfortune to visit this massive gas giant, you’d soon regret it.

As well as being spun furiously by winds blowing at 8,700 km/h, you’d be cut to shreds by glass rain. The planet’s delightful blue colour is the reflection of silicate in its atmosphere – silicate that, when heated by the planet’s deathly 1300°C temperature, forms grains of glass.

Jane Williamson, “10 of the weirdest exoplanets in the Universe” at Sky at Night (February 25, 2022)

So how many exoplanets could host extraterrestrial civilizations? Williamson estimates that there are 300 million “potentially habitable worlds” in our galaxy — but they probably won’t be quite so bizarre.

Swedish researchers recently published an open-access paper identifying 45 exoplanets that could host something that we would recognize as life.

For their study, the researchers combed through existing exoplanet catalogs in search of distant worlds known to have hydrogen, oxygen, dinitrogen and carbon dioxide in their atmospheres. The researchers estimated how fast those four “atmospheric species” escape into space using the “kinetic theory of gases” (how gases move about the atmosphere).

The team found 17 exoplanets in one catalog that met their habitability criteria and another 28 exoplanets on the wider exoplanet list. These worlds, according to the researchers, can potentially retain gases essential to life in their atmospheres and may be able to maintain stable liquid water.

Virgilio Marin, “Researchers discover 45 potentially habitable exoplanets” at FuturescienceNews (November 9, 2020)

The nearest potentially habitable exoplanet to Earth is thought to be one that orbits Wolf 1061 at 14 light years away:

“It is a particularly exciting find because all three planets are of low enough mass to be potentially rocky and have a solid surface, and the middle planet, Wolf 1061c, sits within the ‘Goldilocks’ zone where it might be possible for liquid water – and maybe even life — to exist,” says lead study author UNSW’s Dr. Duncan Wright.

“It is fascinating to look out at the vastness of space and think a star so very close to us – a near neighbour – could host a habitable planet.

University of New South Wales Australia, “The nearest potentially habitable planet to Earth” at NASA Exoplanet Exploration (December 16, 2015)

The universe is fine-tuned for life and that would be an argument for life on exoplanets.

To sum up, whatever we see or read about planets in science fiction, something out there is likely stranger still.

And the James Webb Space Telescope continues the search for life on other planets.

About those 5000 exoplanets to date…

You may also wish to read: New study on why aliens never phone, never write, never visit. Planetary scientists suggest that civilizations follow a trajectory in which there is only a short window of time to look for intelligent extraterrestrial civilizations. If Wong and Bartlett are right, we may only have a short window of time ourselves.

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Among 5000 Known Exoplanets, There Are Some Really Strange Ones