Pack your bags! Astroboffins spot 24 'superhabitable' exoplanets better than Earth at supporting complex life
- Reference: 1601969590
- News link: https://www.theregister.co.uk/2020/10/06/superhabitable_exoplanets_found/
- Source link:
A team led by Dirk Schulze-Makuch, a professor at the planetary habitability and astrobiology at the Technical University Berlin, devised a checklist of requirements that an alien world must meet in order to be classed as a “superhabitable” planet, capable of supporting complex, oxygen-based lifeforms as seen here on Earth. After going through the records on 4,000 exoplanets, the team identified 24 candidates that tick the boxes, though bear in mind all of them are at least 100 light years away.
Complex life is defined as organisms that are “macroscopic and multicellular,” Schulze-Makuch, also an adjunct professor at Washington State University in the US, told The Register . ”On a superhabitable planet, we would expect this type of life in addition to microbial life as well as animal-like and plant-like life.
“It’s sometimes difficult to convey this principle of superhabitable planets because we think we have the best planet. We have a great number of complex and diverse lifeforms, and many that can survive in extreme environments. It is good to have adaptable life, but that doesn’t mean that we have the best of everything.”
[1]
Better than Earth? An illustration of an alien world. Credit: NASA Ames/SETI Institute/JPL-Caltech
For example, Earth's G-type sun will only last about 10 billion years, but K-type main-sequence stars are smaller and dimmer and can last up to 70 billion years. Schulze-Makuch said an exoplanet orbiting one of these stars will have more time for life to evolve, improve, thrive, and survive than here on Earth.
Size also matters. Planets that are larger and heavier will have more habitable land, and stronger gravity to retain an atmosphere. A higher average surface temperature would also lead to a warmer humid climate that supports higher levels of biodiversity, according to the team's paper, [2]published in the journal Astrobiology, which details these superhabitable planets.
PACK YOUR BAGS! Boffins spot Earth-size planet most likeliest yet to harbor alien life [3]READ MORE
Superhabitable planets also share many properties with Earth, including having an atmosphere containing oxygen, land covered in water, plate tectonics, a relatively large moon, and a protective magnetic field to shield it from harmful solar radiation.
There are no exoplanets that have every single box ticked on the checklist, however. Schulze-Makuch told El Reg the best option is exoplanet KOI 5554.01. Located 701 light-years away, it’s estimated to be 6.5 billion years old (give or take a couple of billion), up to 1.29 times larger than Earth, and with a moderate average surface temperature of 26.17 degrees Celsius.
“With the next space telescopes coming up, we will get more information, so it is important to select some targets,” [4]said Schulze-Makuch in a statement. “We have to focus on certain planets that have the most promising conditions for complex life. However, we have to be careful to not get stuck looking for a second Earth because there could be planets that might be more suitable for life than ours.” ®
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[1] https://regmedia.co.uk/2020/10/05/exoplanet.jpg
[2] https://www.liebertpub.com/doi/10.1089/ast.2019.2161
[3] https://www.theregister.com/2017/04/19/exoplanet_life/
[4] https://news.wsu.edu/2020/10/05/planets-may-better-life-earth/
[5] https://whitepapers.theregister.com/
an atmosphere containing oxygen
It's a long time since I was at school - but wouldn't an atmosphere containing significant amounts of oxygen be considered an actual indicator of life? What with oxygen being so reactive, I vaguely remember that if you don't have something actively replenishing it in the atmosphere it rapidly ends up locked into metals on the crust.
On Earth, photosynthesis is that process, courtesy lots of plants on land and sea. But maybe I'm being needlessly carbon-hydrogen-oxygen chauvinistic here, and there are non-life mechanisms that can maintain a large oxygen atmosphere?
Re: an atmosphere containing oxygen
Oxygen is rather reactive. There is a good chance that other life in the Universe would find our atmosphere poisonous ...
Re: an atmosphere containing oxygen
Well indeed. Cyanobacteria here didn't find it too friendly. But the article made the point that oxygen atmospheres were what the search was looking for.
Parenthetically - while it is possible that oxygen-based metabolisms aren't the only ones out there, it is one that we know for certain can maintain a macro-biology.
Re: an atmosphere containing oxygen
Venus?
Re: an atmosphere containing oxygen
The question raised is I think whether oxygen-emitting life-forms are the only known mechanism to sustain an oxygen-rich atmosphere.
Anyone?
KOI 5554.01 sounds like paradise with its average temperature of 26.17 degrees Celsius (how the heck do they measure that so accurately from so far away anyway?)
I'm still astonished that we've one from detecting an exoplanet in [1]1995 to chucking out dozens in a press release about their composition and suitability for life in just 25 years. Bonkers.
Bring on FTL travel, I say. I want to go touring!
[1] https://exoplanets.nasa.gov/what-is-an-exoplanet/about-exoplanets/
With a very very long thermometer.
26.17. plus/minus 4.27.
Warmer.
OK, you have a warm planet, with a thicker atmosphere, but then some brainboxes evolve and make the temperature go even higher, right? Nah, fake news!
Anyway, you probably need a planet with a very large moon to keep its rotation stable, and also huge great gas giants in the system to stop comets slamming into it on a regular basis. That Drake equation is more complicated than he made out!
Re: Warmer.
Rotational stability is probably important for land-based life, but oceanic life probably doesn't care too much, so it probably comes down to how much water there is on the planet in question.
We get the benefit of Jupiter protecting us from occasional visitors from the Oort cloud, but do we know that other solar systems have Oort Clouds?
These are things that help make Earth suitable for complex life, but it's a bit hubristic to assume they are requirements.
Formerly habitable planets
might be found by checking for the presence of plastic. These can be removed from the list.