Last week, NASA revealed to the world that a red dwarf star called Trappist-1 has 7 exoplanets orbiting it, of which 3 lie in the potential habitable zone. They are all Earth-like in size and will be major targets for studies in the coming years. New research and recently completed studies indicate that volcanism on the surface of these planets may increase the habitable zone by up to 60%.
Cornell University astronomers have noticed that a planet harboring active volcanos on frozen worlds might increase the chances of detecting life in some form, as the habitable zone would be increased and liquid water could have formed. The increase in distance could be increased by as much as 60%. Active volcanoes assist in warming the planet’s atmosphere and might create conditions on the surface that would be suitable for liquid water and life to develop. This would create biosignatures and astronomers are currently hard at work developing ways and methods to test for this.
“On frozen planets, any potential life would be buried under layers of ice, which would make it really hard to spot with telescopes,” said Ramses Ramirez, a research associate at Cornell’s Carl Sagan Institute and the lead author of the study. “But if the surface is warm enough, thanks to volcanic hydrogen and atmospheric warming – you could have life on the surface, generating a slew of detectable signatures.”
Greenhouse gases, such as hydrogen, oxygen, and carbon dioxide, generated by a planets volcanic activity could extend a star’s habitable zone from 30 to 60 percent. This increases the amount of potentially habitable exoplanets found so far, some that have been dismissed as probably barren, and changes the parameters of how we are searching for Earth 2.0 and alien life.
At a hydrogen concentration of 50%, the effective stellar flux required to support the outer edge decreases by ~35% to 60% for M to A stars. The corresponding orbital distances increase by ~30% to 60%. The inner edge of this HZ only moves out by ~0.1 to 4% relative to the classical HZ because H2 warming is reduced in dense H2O atmospheres. The atmospheric scale heights of such volcanic H2 atmospheres near the outer edge of the HZ also increase, facilitating remote detection of atmospheric signatures.
“We just increased the width of the habitable zone by about half, adding a lot more planets to our ‘search here’ target list. Adding hydrogen to the air of an exoplanet is a good thing if you’re an astronomer trying to observe potential life from a telescope or a space mission. It increases your signal, making it easier to spot the makeup of the atmosphere as compared to planets without hydrogen.”
Potential biosignatures could become easier to detect as they would show as hydrogen increases. A planet can only hold the hydrogen for a few million years, but active volcanoes would keep the amount topped up for far longer.
“Where we thought you would only find icy wastelands, planets can be nice and warm– as long as volcanoes are in view,” said Lisa Kaltenegger, Cornell professor of astronomy and director of the Carl Sagan Institute.
The new research suggests that the fourth Trappist planet now lies within the potential habitable zone of the star. Even more encouraging for the fourth Trappist planet is the fact that it has a reduced chance of being tidally locked and would receive less radiation from Trappist. Everything depends on volcanoes.
Kaltenegger noted that the discovery of multiple worlds in the habitable zone “is a great discovery because it means that there can be even more potentially habitable planets per star than we thought. Finding more rocky planets in the habitable zone — per star — increases our odds of finding life. Although uncertainties with the orbit of the outermost Trappist-1 planet ‘h’ means that we’ll have to wait and see on that one.”
Neil deGrasse Tyson was quick to point out that young red dwarf stars like Trappist-1 are often volatile and spew out solar winds very often. This could have killed off any atmosphere on some or all of the Trappist planets making life unlikely.
“Because the star is a dwarf — it’s small — it’s still generating energy and the like, but it’s not as hot as the Sun is. Red dwarf stars a hugely turbulent on their surface and they are spewing forth plasma particles at high speeds.”
Increasing the habitable zone increases the potential for finding life, which seems to be NASA’s main mission at the moment and many experts believe that 2017 will be the year we find it. Not only does the new research increase the probability of finding life in the Trappist system, but also in other systems around the galaxy. It is an exciting time to be an astronomer.