James Cross
The search for meaning beyond our planet is an idea that has plagued humanity for as long as we’ve looked up at the night sky. Astronomy is one of the oldest sciences, with individuals using the stars and planets for navigation and meaning for thousands of years.
The Search for Understanding
This search for understanding of the night sky has led to stories around constellations, and mythology around planets. Storytelling is a primal human experience that helps us to understand things that are beyond our comprehension, and the stars and planets are no exception to this rule.
It’s only been in recent years that the stories and ideas that the night sky inspires have been able to be investigated with hard science. The space race began in the 40’s, and the search for bigger and better things beyond our solar system has been ongoing in the decades ever since.
Life on Other Planets
One of the biggest questions that scientists who study space are trying to answer, of course, is the question of life on other planets. It would be the height of arrogance to believe that humans on earth are the only form of life in the entire universe, and scientists have spent decades coming up with various formulas, theories, and ideas about what would make life possible on other planets.
First and foremost, of course, is the need for liquid water on a planet to sustain life. Of course, this operates on the idea that all forms of life in the galaxy would require water, but it’s a good metric to begin with, one that allows scientists to narrow down possibilities out of the limitless planets that are in the galaxy.
Life in the “Goldilocks Zone”
Until recently, scientists have been using a metric called the “Goldilocks Zone” to determine which planets could possibly have liquid water on them. This is a measurement that looks at the distance a planet is to its home star. Too close, and any liquid on the planet would evaporate; too far, and the water would freeze.
The Goldilocks Zone is the exact right distance for a planet to have liquid water, as well as the possibility of some sort of habitable atmosphere. This measure has worked well for scientists, who have been able to narrow down multiple planets that could possibly have life on, by factor of their distance from their star alone.
A Different Method of Determining Habitability
However, a new method to assess the potential habitability of a planet has recently been developed by scientists. This index goes beyond the traditional Goldilocks Zone metric.
The method, which was detailed in a paper published in the Astrophysical journal, incorporates a wider range of data points. These points include transit data, stellar properties, and previously reported limits on planetary emitted flux, according to the paper. This approach is more comprehensive, and aims to provide a more accurate assessment of a planet’s potential to sustain life.
Assigning Earth a Rating
A new method to measure habitability would be exciting enough, but the new metric has already begun to work. The new method assigns a habitability rating to planets based on collected data, and Earth received a score of 0.829.
Another planet, though, received a slightly higher rating on this scale. The planet, Kepler-442b, was rated 0.836, meaning that it’s even more habitable for human life than earth itself is.
Larger than Earth, But Not a Gas Giant
Kepler-442b is a super Earth exoplanet, meaning that it’s larger than the size of Earth, but not quite as large as the gas giant planets like Jupiter and Saturn. Its mass is 2.36 Earths, and it takes 112.3 days to complete one orbit of its star.
The discovery of Kepler-442b was announced in 2015, and it was discovered by NASA’s Kepler spacecraft using the transit method. This is a method in which the spacecraft measures the dimming effect that a planet causes as it crosses in front of its star.
Orbiting a K-Type Main Sequence Star
Kepler-442b is in the Goldilocks zone of its planet, meaning that by earlier measures, scientists would have determined that it was potentially habitable on the face of it. But the size of its star is an important factor as well.
Kepler-442, the star which the planet orbits, is a K-type main sequence star which is approximately 2.9 billion years old. For comparison, our own sun is 4.6 billions years old, and is significantly hotter than Kepler-442. K-type main sequence stars are smaller than our sun and live longer, potentially living for 18-34 billion years.
A Longer Potential for Life
This means that Kepler-442b could potentially have life on the planet for significantly longer than Earth. The size of its star could have drawbacks, though. Because of their high stellar activity at the beginning of their lives, K-type main sequence stars emit strong solar winds, which could impact the habitability of planets that orbit them.
However, the age of Kepler-442 is uncertain. It’s entirely possible that the star has already passed beyond this volatile early stage of life, increasing the habitability of the planets in its Goldilocks zone.
Further Observation is Needed
The rating of 442b with this new metric determined by scientists is promising, but there’s still a significant amount of research to be done before any true metrics of habitability can be determined.
Crucially, the composition of its atmosphere and the conditions on the surface of the planet remain mysteries. The Astrophysical Journal paper emphasized that a higher rating doesn’t automatically translate to a more suitable environment for life as we know it on Earth, it simply means that it’s possible that the planet would be suitable for life as we know it.
Challenges Facing Space Scientists
The vastness of the universe makes it difficult for scientists to do true research into these other planets to determine their viability for life. There’s nothing like getting your feet on the ground and looking at things with your own eyes, and this is a luxury that space scientists, unfortunately, are not afforded.
This is especially true in the case of Kepler 442b. The planet is approximately 1200 light-years away from earth, in the constellation of Lyra. A light year is approximately 5.88 trillion miles, meaning that it would take thousands of years for current technology to reach Kepler 442b.
Potential Details
There are many things that can be determined through current methods, though. The size of Kepler 442b, as well as the estimated planetary composition means that the surface gravity of the planet would be approximately 30% stronger than on Earth.
Additionally, because 442b is closer to its star than Earth is to the sun, it’s likely that the planet rotates much more slowly than Earth. Its day could be weeks or months long, compared to the 24 hour period of an Earth Day.
A Probably Lack of Seasons
The axial tilt of the planet is also telling about what potential life could be like. It is likely tiny, which means that the planet would not have tilt-induced seasons like Earth and Mars do.
Observations imply that the orbit of the planet is likely circular, compared to the oblong orbit of the Earth and other planets that circle our own Sun. This means that the planet would also lack eccentricity-induced seasonal changes like Mars. It’s likely that seasonality on the planet is very bland, given the thus-understood information, but nothing can be confirmed.
So Much Still to Learn
It’s an exciting day when a new planet is discovered that could possibly house life on it, and there is still so much to be learned. Astronomy and the study of stars is a long-game science, with many things far beyond our understanding with current technological advancements.
As technology grows and changes and advances, though, our understanding of the stars above us will grow as well. Learning about other planets that could potentially house life is one of the first steps to expanding our reach in the universe, and it’s an undertaking that scientists at NASA and other organizations have accepted proudly.
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