However, as scientists discover an increasing number of exoplanets throughout the universe, many new candidates to be an ideal Earth 2.0 have emerged.
For example, in February 2022 Newsweek reported that astronomers have spotted two miniature Neptune exoplanets, which, when they lose their bloated atmosphere, are likely to turn into what’s called a “super-Earth.”
But have we already found any exoplanets we can live on, and if so, how can we find out from so far away?
A post on Reddit claiming that Earth’s “distant twin,” Kepler-442b, is actually more habitable than Earth made it to the site’s front page this week with more than 42,000 upvotes.
Kepler-442b is a rocky exoplanet 1,206 light-years away from Earth that orbits it. [in] The habitable zone of its star, it has a rating of 0.836. Earth at 0.829″, the post states.
The image of the planet has been named “Kepler-422b,” which appears to be a typo.
The publication refers to the Planetary Habitability Index first published in Astrophysical Journal in 2015, which uses various data about an exoplanet and its orbit to determine its habitability.
Kepler-442b is a rocky planet found orbiting the star Kepler-442, which accounts for about 40 percent of the mass of our sun and has been dubbed a “super-Earth” by NASA.
While Kepler-442b is rated higher in this index than Earth, that does not mean that it is more habitable than our home planet and therefore may not necessarily be able to host life.
The classification is based on the planets passing through our observing perspective (that is, those systems in which planets cross in front of their star and block their light). The classification is based on whether the planet is rocky, receives enough starlight, or how “non-circular” the planet is. (eccentric),” Ravi Kubarapu, an extrasolar habitability expert at NASA’s Goddard Space Flight Center, said. Newsweek.
For Kepler 442b, based on the amount of starlight the planet receives and the other factors I mentioned above, it turns out that this planet has a higher index than possible Earth-sized planet around a Sun-like star. Or perhaps a more accurate way of saying it, better conditions for habitability. Instead of saying “more habitable,” which is a vague phrase.
He added, “It says nothing about whether a planet can be ‘inhabited’. Just because a planet is habitable doesn’t mean it has to be inhabited.”
While exoplanets were previously only assessed based on their position relative to their star, and if they were in the “Goldilocks” or habitable zone (where water can exist in liquid form), this updated index takes into account a wide range of factors that determine what If life will survive.
“The new habitability score … adds information about the stability of the climate, given what is known about the orbit of the planets and the type of star they orbit,” said Andrew Cole, professor of astrophysics at the University of Tasmania. Newsweek.
“Climate stability is very important for a planet’s long-term suitability for complex, multicellular life. (Bacteria are much more robust, and can probably survive under much more hostile conditions.)
“There are two important points though: The first is that we don’t actually know the conditions on the planets, without analyzing the composition of the atmosphere and surface; we can only make our best guess from the available information.
“The current state of the climate on Earth shows us that things can vary very dramatically in a way that is truly undetectable from outside the solar system to an alien observer.
“The second important point is that no known current or future technology can allow us to escape to any secondary homeworld of humanity — the distances involved are too great.”
From such a great distance, it is very difficult to gather much information about conditions on an exoplanet, so estimates of habitability must be drawn from available basic data. Other factors not measured in the index may make the planet more habitable, such as a strong magnetic field or lunar satellite.
“The hallmarks of a highly habitable planet would be a super-Earth with a water content greater than that of Earth, a near-circular orbit, and an atmosphere much denser and more insulating than our own,” says Chris Imby, a professor of astronomy at the University of Arizona. Tucson said Newsweek.
“We’ve found near-Earth ‘clones’, but as this research shows, we can do better than Earth for Planet B. But the catch is that it’s probably 100 light-years or more away, and the energy costs of going there, even With small spacecraft, it’s prohibitive. Much cheaper to take care of Planet A.”
While Kepler-442b is ranked higher in the habitability index than Earth, this index is based on very broad and fundamental properties of the planet’s orbit around its star that can be observed from thousands of light-years away.
Other factors that we cannot measure about Kepler-442b, such as its atmosphere content, the presence of water, or surface pressure, might make it less habitable than Earth, but they are not included in this catalog.
Fact-check by Newsweek
Barnes, R et al. Comparative habitability of transiting exoplanets. The Astrophysical Journal, 814 (2015). http://dx.doi.org/10.1088/0004-637X/814/2/91