What if our Sun were hotter?

Our Sun is a star that gives us warmth and light. But, be grateful that it isn’t even more luminous. So, what if our Sun were hotter?

A star’s temperature

Like other what-if articles, we need to talk about the background information first. Let’s memorize this pattern: For a main-sequence star, the hotter it is, the more massive, bluer, and brighter it is. We’ll explain this simple relationship a bit later.

First of all, don’t think red is the hottest, because it’s the coolest with the longest wavelength, carrying less energy. So, cool red dwarfs do not create enough energy to be as bright as the Sun. On the contrary, blue and violet stars are the hottest as they carry more energy than the rest. Therefore, hot stars emit enough light to be thousands of times brighter than our star. But what about the mass? Well, if we put more mass, the center of the star will be denser. Stars use their densities to initiate nuclear fusion, and that makes sense, right?

So, what if our Sun were hotter?

Now, we’ve talked about the simple mechanism, and as a result, the outcome is related too. But, if that happened, Earth would not be habitable. When a star gets hotter, the habitable zone — an area where the temperature supports liquid water, moves outward. Because Earth is in the inner edge of the habitable zone, once the Sun gets just a little bit hotter or bigger, Earth’s fate will be like Venus. If all oceans on Earth evaporate, there’s more greenhouse effect since water vapor is also a greenhouse gas.

Also, Earth would encounter some other problems too. Firstly, the lifetime of high-mass stars is only millions of years, so if Sun were that star initially, it had died long before. Moreover, hotter stars emit more ultraviolet rays, overwhelming the ozone layer, causing damage to ecosystems.

So, it’s no fun talking about that, but what if the high-mass star were our neighbors?

Curious Question: What if neighboring stars were high-mass?

It turns out that high-mass stars are quite harmful, even at a distance. In a Supernova, the electromagnetic radiation emitted is so powerful that it can negatively affect life 50 light years away! Lucky for us, the nearest supernova candidate is IK Pegasi B, which is a white dwarf 150 light years from us.

So, if one of the nearest stars are blue, hot stars, they will threaten life on Earth sooner or later because of supernovas. But, talking about changes, Earth’s Moon Exploding is a larger threat. Please be grateful that neither of these is on the way right now.

Credits

1. “Life Cycles of Stars”, Imagine the Universe!, https://imagine.gsfc.nasa.gov/educators/lifecycles/LC_main_p8.html
2. NASA’s Eyes, eyes.nasa.gov
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