Could a Goldilocks Zone Galaxy Exist? | Unveiled

Could a “Goldilocks Zone Galaxy” Exist?

Earth is able to support life because it exists within the “Goldilocks zone” relative to our sun. If it were further away, it would be frigid and icy; too close and it would be another Mercury or Venus. As is, it’s at the perfect range to have temperatures that sustain liquid water, and thus, life. But is there a habitable zone not only for stars, but for galaxies as well?

This is Unveiled and today we’re answering the extraordinary question: Could a Goldilocks Zone Galaxy Exist?

We use the term “Goldilocks zone” to describe areas in space that are more likely to produce life. Usually, this is applied to planets and their distance from the star they orbit. This habitable zone varies with different types of stars. The term “Goldilocks zone” comes from the children’s fairytale about a presumptuous young girl named Goldilocks who breaks into the home of a family of bears, eating their porridge and sleeping in their beds until finding one that’s juuust right.

It turns out that not only is there a habitable zone around a star, there might be a habitable zone within galaxies as well. This is because many areas of a galaxy are dangerous to possible life. Take the center of a galaxy, for example; astronomers believe that a supermassive black hole lies at the heart of every major galaxy, and being near it would be extremely hazardous. Supermassive black holes release large amounts of radiation in the form of gamma rays, X-rays, and cosmic rays, which would kill all but the simplest life forms. The gravitational pull would also be extremely powerful and mess with stellar and planetary orbits. In our own solar system, the proximity of so much mass could send comets from our Oort cloud careening towards Earth more frequently, all but ensuring our doom.

Galactic centres are not the only dangerous areas in galaxies. So too are the spiral arms at the outer edges. New stars are constantly being recycled there, birthing and dying in supernova explosions. The gravitational pull is nearly as destructive as at the center, and our solar system would be in big trouble if were ever got caught up in one of these arms. Luckily, our sun orbits the centre of the galaxy at just the right speed so that it doesn’t pass through them. The circularity of this orbit is also fortunate; if the sun had a more elliptical path around the galactic centre, we’d intersect an arm at some point, and we might not survive the radiation or gravitational gauntlet.

The likely existence of a galactic habitable zone further emphasizes the improbability of our existence. The ideal zone for life inside of our own Milky Way is between about 13,000 to 33,000 light years from the galaxy’s center. Fortunately, we’re in a great spot at 27,000 light-years from the center. It’s possible that life exists outside of this zone - but it’s probably very simple. Advanced, complex life doesn’t adapt to hazardous environments as well as simple organisms such as bacteria.

If there’s a goldilocks zone for the right kinds of galaxies in the universe as well, it would limit the possibility of alien life even further. That’s what we mean by “goldilocks zone galaxies”. In order to have the ideal conditions for life, a planet would have to not only exist within the habitable zone of its own star, but also within the habitable zone of its own galaxy - and that galaxy too would have to be in a habitable zone in the universe. According to astronomer Guillermo Gonzalez at the University of Washington, at most 5% of stars in the Milky Way lie within our galaxy’s habitable zone. So our sun may be one of the few stars in our own galaxy able to support life. If there’s also a habitable zone in the universe for galaxies where stars and planets suitable for life are likely to form, we might never encounter alien life. There are just too many conditions that need to be met. Expecting one of these extremely rare occurrences to happen next door to us may be wishful thinking.

But what reason could there be to support the idea that there’s a goldilocks zone within the universe itself? It might be the concentration of “metals”, which for astronomers are any elements heavier than hydrogen or helium. We already know that older stars are far less likely to have terrestrial planets around them. This is because they were formed long ago, in a relatively young universe. During that time, there was mainly hydrogen, helium, and lithium floating around, as heavier elements hadn’t been formed yet by supernovae. Once enough stars had lived their lives and exploded, they produced the heavier metals that spread throughout the universe and allowed for the formation of terrestrial planets. Our sun itself is strange in the fact that it possesses an unusually high metal concentration. This may be because it formed in another part of the galaxy, in a more metal-rich area, and somehow ended up here. Some parts of the universe could be much denser in metal than others, allowing for the formation of planets able to harbor life. Galaxies in this zone would have an extreme advantage compared to galaxies where the concentration of metals was lower.

Regardless of the reason, how would the existence of Goldilocks zone galaxies change our understanding of the universe? Well, the ideal conditions of Earth would be even more miraculous. This might be used by religions to encourage belief in a God who oversaw creation. Our uniqueness would bolster the claim that we were made in God’s image. Had other, very different intelligent beings been discovered, that notion would become more difficult to maintain.

On top of all that, there might even be a sweet spot in time for life existing. There are explosions called gamma ray bursters that are among the most powerful in the universe - so much so that even if they occurred in a distant part of our own galaxy, they very well might end life on Earth. A strong one could even disrupt an entire galaxy! And these bursts were likely more common in the early universe, along with a scarcity of heavy metals to form planets. It’s thought that these gamma ray bursts happen as frequently as every 100 million years in our own Milky Way. If that’s the case, we could exist in a goldilocks zone in space and time. It may also be that these cosmic events are more likely to occur in certain parts of the universe, giving merit to the idea that there are certain Goldilocks zones where galaxies are more likely to avoid such destruction.

And that’s why a goldilocks zone could exist.