What If the Sun Was a Blue Star?

Billions of years in the future, the Sun will begin to die. And this is what our planet would look like. But what if we turn things up a notch or two right now? Let’s upgrade our star from yellow to blue. How different would the world look? Could your body handle the increased heat? Or would all life on Earth die?

Like any visible light, sunlight contains all the colors of the rainbow. But how we see a star or any planet depends on how hot the star is. The coolest stars in the Universe have temperatures of about 1,750 °C (3,200 °F) and emit more red light, while the hottest stars have temperatures over 40,000 °C (72,000 °F) and look bluer.

Our Sun has a surface temperature of 6,000 °C (10,800 °F). So it emits almost equal amounts of blue and red wavelengths. If you could see the Sun from space, it would appear whiteish. Hang on a second. The Sun isn’t yellow? That’s right. The Sun only appears yellow to you because of Earth’s nitrogen-rich atmosphere. Red light and yellow light have longer wavelengths and can reach your eyes easier.

Blue light has a shorter wavelength and scatters more, giving the sky its blue color. But if our Sun was a blue star, you’d never get to see a spectacular orange sunset again. And you’d also get fried instantly. Before making our Sun blue, let’s take a look at a couple of bright blue stars that we know of. On the cooler end of the blue star spectrum is Rigel, the brightest in the Orion constellation.

Its surface temperature is about 11,000 °C (20,000 °F). While it’s almost twice as hot as our Sun, Rigel emits at least 40,000 times more energy. And Rigel’s diameter is 79 times larger than our star. If our Sun was that large, it would swallow Mercury. And temperatures on Earth would increase immensely. But why stop there? You could turn the dial up even further.

If we imagine the Sun on the higher end of the blue star spectrum, it could be like Eta Carinae. With surface temperatures at 40,000 °C (72,000 °F), this star is over six times hotter than the Sun. But what’s staggering is that Eta Carinae emits 1 million times more energy than our Sun. If our Sun was that hot, it would be five million times brighter than it is today.

Violent ejections of plasma would scorch our planet regularly. And the Sun would drench us in lethal amounts of UV radiation. There’s no way you could survive the heat. If you stepped outside for just one second, it would be like stepping in an oven, only hotter. The blue Sun would instantly burn all the tissues in your body to ashes, and maybe even your bones.

It would be game over for you. Just kidding. I wouldn’t let you off the hook so easily. Let’s imagine that your body was super resistant to this extreme heat. There would still be that enormous amount of UV radiation to deal with. It would wreak all kinds of havoc on your body, causing your skin to wrinkle, age, and get cancer.

Your vision would suffer immensely too. You’d get something like a sunburn in your eyes. The UV radiation would make your vision blurry, and your eyes would hurt like hell. It would be like snow blindness, but be caused by the Sun’s radiation. In addition to losing your sight, the blue light would mess with your beauty sleep. Blue light suppresses your melatonin levels.

With so much more blue light and so much less of this hormone, sleeping would be tough. Poor sleep could lead to high blood pressure, diabetes and even heart failure. The blue light would affect a lot more than just us humans. Outdoor plants would grow smaller, thicker and have darker leaves. High-intensity blue light would promote flowering in long-day plants that usually need at least 12 hours of sunshine a day to thrive.

All the other plants that don’t like as much sunlight would die. Well, you’d still likely have long-day garden vegetables like lettuce, spinach and potatoes. But if our Sun became as massive as Eta Carinae, you’d have heavier problems than what to eat in your new diet. The Sun’s new, incredibly intense gravitational pull would disrupt the Solar System.

You’d see Earth and the other planets get swallowed up by it. Instead of getting engulfed by this massive Sun, you’d be lucky if Earth went a little sideways and got shot off into space. Then we’d live on a rogue planet that’s not held by a star’s gravity and roaming the Universe. We’d likely freeze up pretty quickly and die anyway.

If there’s one benefit, it’s that all this chaos and destruction wouldn’t last forever. Instead, it would end quite quickly. A star like Eta Carinae has a live fast, die young lifestyle. At its young age of about 3 million years, it is already nearing the end of its fuel supply. It could explode into a supernova sometime within the next 100,000 years.

Our Sun is about 4.5 billion years old, and scientists expect it to keep burning for another 7 billion years. So if we turned up the Sun’s heat, we’d be dooming our star and our planet to premature death. Not that many life-forms would survive to see that day. The earliest life on our planet dates back to about 3.7 billion years ago. At that point, our Sun was already 800 million years old.

Back then, if the Sun burned as hot and bright as Eta Carinae, it would have exploded as a supernova hundreds of millions of years before there was life anywhere nearby. So our lives seem better with the Sun burning at its current temperature.