The habitable zone is the region around a star where planets can maintain liquid water on their surface. It’s axiomatic that planets with liquid water are the best places to look for life, and astronomers focus their search on that zone. As far as we can tell, no water equals no life.
But new research suggests another delineation in solar systems that could influence habitability: The Soot Line.
Stars emit powerful flares that can be deadly for any burgeoning life on nearby planets. Images from spacecraft that monitor the Sun show these flares in glorious, horrifying detail. But the flares from the Sun are mere nuisances compared to some stars. Some stars produce catastrophic superflares, which can be tens of thousands of times more energetic than the Sun’s. That much energy can sterilize a planet’s surface.
But new research shows that a certain amount of flaring activity on the Sun could’ve been beneficial. It could’ve kick-started life on Earth.
Life on Earth has been around for a long time—at least 3.8 billion years. During that time, it evolved significantly. Why has biodiversity here changed so much? A new study proposes a startling idea. Some major diversity changes are linked to supernovae—the explosions of massive stars. If true, it shows that cosmic processes and astrophysical events can influence the evolution of life on our planet.
One of the most interesting questions we can ask is, “How did life form?”. To answer it, scientists go back to look at the basic chemical building blocks of life. Those are water, carbon-based organic molecules, silicates, and others. The James Webb Space Telescope offered a peek at the gases, ice particles, and dust surrounding a newborn star and found organic molecules exist there.
To date, 5,250 extrasolar planets have been confirmed in 3,921 systems, with another 9,208 candidates awaiting confirmation. Of these, 195 planets have been identified as “terrestrial” (or “Earth-like“), meaning that they are similar in size, mass, and composition to Earth. Interestingly, many of these planets have been found orbiting within the circumsolar habitable zones (aka. “Goldilocks zone”) of M-type red dwarf stars. Examples include the closest exoplanet to the Solar System (Proxima b) and the seven-planet system of TRAPPIST-1.
These discoveries have further fueled the debate of whether or not these planets could be “potentially-habitable,” with arguments emphasizing everything from tidal locking, flare activity, the presence of water, too much water (i.e., “water worlds“), and more. In a new study from the University of Padua, a team of astrobiologists simulated how photosynthetic organisms (cyanobacteria) would fare on a planet orbiting a red dwarf. Their results experimentally demonstrated that oxygen photosynthesis could occur under red suns, which is good news for those looking for life beyond Earth!
Life doesn’t appear from nothing. Its origins are wrapped up in the same long, arduous process that creates the elements, then stars, then planets. Then, if everything lines up just right, after billions of years, a simple, single-celled organism can appear, maybe in a puddle of water on a hospitable planet somewhere.
It takes time for the building blocks of stars and planets to assemble in space, and the building blocks of life are along for the ride. But there are significant gaps in our understanding of how all that works. A new study is filling in one of those gaps.
Future historians might look back on this time and call it the ‘exoplanet age.’ We’ve found over 5,000 exoplanets, and we’ll keep finding more. Next, we’ll move beyond just finding them, and we’ll turn our efforts to finding biosignatures, the special chemical fingerprints that living processes imprint on exoplanet atmospheres.
But there’s more to biosignatures than atmospheric chemistry. On a planet with lots of plant life, light can be a biosignature, too.
Here’s a thorny problem: What if life doesn’t always appear on planets that can support it? What if we find more and more exoplanets and determine that some of them are habitable? What if we also determine that life hasn’t appeared on them yet?
Could we send life-bringing comets to those planets and seed them with terrestrial life? And if we could do that, should we?