Are we alone?

     

Bigger, better, more suited for biology: let"s not overlook superhabitable planets with potential.

Bạn đang xem: Are we alone?


*

An artist"s depiction of a rocky, Earth-size exoplanet. We haven"t found any planets exactly as habitable as Earth, but some planets might be even better for life than ours: superhabitable worlds.(Image credit: NASA Ames/SETI Institute/JPL-Caltech)
A superhabitable planet is a world that might have an even better chance at hosting life than our own home, Earth.


Because Earth is the only known inhabited planet & its life depends on liquid water, efforts lớn identify exoplanets that could host life focus on Earth-like worlds. But some researchers think there are other types of planets that could offer conditions for life as good as — or even better than — Earth. In fact, some scientists argue that focusing only on Earth-like worlds might be too "anthropocentric & geocentric," blinding us lớn the possibilities of exobiology.

"We are so over-focused on finding a mirror image of Earth that we may overlook a planet that is even more well-suited for life," Dirk Schulze-Makuch, an astrobiologist at Washington State University & the Technical University of Berlin, told thietkewebshop.vn.


To tìm kiếm for potentially superhabitable exoplanets, Schulze-Makuch and his team investigated the Kepler Object of Interest Exoplanet Archive, focusing on 4,500 planetary systems that likely possessed rocky planets within their stars" habitable zones, where liquid water can persist. The researchers published their findings in a 2020 paper in the journal Astrobiology (opens in new tab).

In addition to looking at planetary systems with yellow dwarf stars lượt thích our sun, the scientists also looked at orange dwarf stars, which are cooler, dimmer and less massive than our sun.


"Our sun is actually not the best kind of star for hosting a planet with lots of life on it," Schulze-Makuch told thietkewebshop.vn.

Orange dwarf stars are about 1/2 more common than yellow dwarfs in the Milky Way. Whereas our sun has a lifetime estimated at less than 10 billion years, orange dwarfs have lifetimes of 20 billion to lớn 70 billion years. Since complex life took about 3.5 billion years to appear on Earth, the longer lifetimes of orange dwarf stars could give planets within their habitable zones more time lớn develop life and accrue biodiversity.

Earth is about 4.5 billion years old, so the researchers speculated the sweet spot for life would be a planet between 5 billion lớn 8 billion years old.

Xem thêm: Bộ Đề Tinh Túy Ôn Thi Đại Học 2017 Chất Lượng Cao, Tài Liệu Ôn Thi Thpt Quốc Gia 2017


The kích cỡ and mass of a planet can also influence how well it can support life, the researchers wrote. A rocky planet that is larger than Earth would have more habitable surface area, và potentially a thicker, more stable atmosphere. A planet with about 1.5 times Earth"s mass would likely retain its interior heat longer, which in turn would help keep its vi xử lý core molten và its protective magnetic field active for a greater timespan in which life might have the chance to lớn arise & evolve.

Worlds that are slightly warmer than Earth by about 8 degrees Fahrenheit (5 degrees Celsius) might be superhabitable, since they could have larger tropical zones which on Earth foster more biodiversity. However, warmer planets might also need more moisture, since greater heat could expand deserts.

In addition, planets with the same amount of land area as Earth but broken up into smaller continents might be more habitable. When continents become particularly large (such as Earth"s past continent Gondwana, about 500 million years ago), their centers are far from oceans, often rendering the interiors of large continents vast, inhospitable deserts. Moreover, Earth"s shallow waters have a greater biodiversity than its deep oceans, so scientists speculate that planets with shallower waters could tư vấn more life.

What are some superhabitable planets?


All in all, Schulze-Makuch and team identified 24 potentially superhabitable planets. None of these worlds met all the criteria the researchers drew up for superhabitable planets, but one did meet at least two — KOI 5715.01.

KOI (Kepler Object of Interest) 5725.01 is a planet about 5.5 billion years old and 1.8 to lớn 2.4 times Earth"s diameter orbiting an orange dwarf about 2,965 light-years away. It might have an average surface temperature about 4.3 degrees F (2.4 degrees C) cooler than that of Earth, but if it has more greenhouse gases than Earth khổng lồ trap heat, it might be superhabitable, the researchers wrote.

Schulze-Makuch"s own favorite potentially superhabitable world from these 24 was KOI 5554.01. This planet is about 6.5 billion years old, with a diameter 0.72 khổng lồ 1.29 times that of Earth, orbiting a yellow dwarf about 700 light-years from Earth.

"I really liked the average surface temperature — about 27 degrees C <80 degrees F>," Schulze-Makuch said. "And it"s probably about Earth"s size, & a little bit older than Earth."


All 24 of these potentially superhabitable planets are more than 100 light-years from Earth. This makes them too far for NASA"s Transiting Exoplanet Survey Satellite (TESS) thietkewebshop.vncraft to lớn capture high-quality images from to learn more about them.

Still, Schulze-Makuch noted that future thietkewebshop.vncraft, such as the newly launched James Webb thietkewebshop.vn Telescope, NASA"s LUVOIR thietkewebshop.vn observatory mission concept và the European thietkewebshop.vn Agency"s PLATO thietkewebshop.vn telescope, could shed light on these worlds.

Xem thêm: Tài Liệu Ôn Thi Thpt Quốc Gia 2022 Môn Hóa Học, Tài Liệu Ôn Thi Thpt Quốc Gia Môn Hóa Học

"We caution that while we search for superhabitable planets, that doesn"t mean that they necessarily contain life," Schulze-Makuch said. "A planet can be habitable or superhabitable but uninhabited."

Additional resources and reading

If you"re thrilled by the idea of exoplanets, poke around the NASA Exoplanet Archive (opens in new tab) yourself! If you want to read more about how different & bizarre other planets might be, dive in to astronomer Michael Summers và physicist James Trefil"s 2017 book "Exoplanets: đá quí Worlds, Super Earths, Pulsar Planets, & the New tìm kiếm for Life beyond Our Solar System (opens in new tab)." and for anyone looking to lớn dream about living on another world, get lost in this TED playlist (opens in new tab) about becoming — and thriving as — an extraterrestrial.

Bibliography


Join our thietkewebshop.vn Forums lớn keep talking thietkewebshop.vn on the latest missions, night sky & more! và if you have a news tip, correction or comment, let us know at: community

*

Charles Q. Choi is a contributing writer for thietkewebshop.vn và Live Science. He covers all things human origins & astronomy as well as physics, animals và general science topics. Charles has a Master of Arts degree from the University of Missouri-Columbia, School of Journalism & a Bachelor of Arts degree from the University of South Florida. Charles has visited every continent on Earth, drinking rancid yak butter tea in Lhasa, snorkeling with sea lions in the Galapagos và even climbing an iceberg in Antarctica. Visit him at http://www.sciwriter.us