Space is Big. I say this often, but it is so vast we can’t even comprehend the emptiness of it. We see Billions upon Billions of stars, all taunting us with their shine, seemingly close but completely unreachable.
How do we know which stars we should spend our time looking at? We don’t really have the time to scan through each star in detail, so what are the criteria for taking a closer look?
Generally we look at a population of stars to gain an understanding of each life stage, and then we look at the oldest and youngest to determine their lifespan. We look at stars with a range of masses to see how they behave and evolve differently, and then we look at the biggest and brightest stars to learn about the formation of extreme objects such as Pulsars and Black Holes and the supernovae that lead to them.
But when it comes to looking for planets, how do we say that one star is better than another? We’ve found planets around stars of all sizes and in all environments. How do we choose? Ultimately we want to find habitable planets, which means looking for worlds in the ‘Goldilocks’ zone of a star, basically the range of orbital distances around the star that can host liquid water. It’s different for every star and depends on the star’s Luminosity and Size.
For Earth-sized planets, we want to be able to actually see them. A bright star will block out the light from a small planet and a massive star will diminish the gravitational effects of an Earth-Sized world.
Astronomers from Cornell University’s Institute for Pale Blue Dots (Yes that’s a real institution name) have found that searching for Baby-Earths is easier than we expected. When looking at young stars, they realized that the habitable zone is further from the stars than previously thought. This extra distance makes it that much easier for future generations of telescopes to see the planets, since they are less likely to be obscured in the light of their home star.
The researchers also found that different planets could host life at different stages of their evolution. As a star ages and its luminosity changes, some planets could move into the shifting habitable zone. This is a double-edged sword though, as some planets in the habitable zone could move out of it. Still, life is very resilient, and perhaps developed life on a habitable-zone planet could find a way to survive a zone shift, especially since these changes are gradual. Life may have the time to adapt.
Over the next 20 years, we are going to find many amazing surprises in the search for habitable worlds outside our own. Sometime soon we may find a place humans can live, or maybe that place is already occupied.