Astronomer explains the possibility that the star you wished upon may already be dead
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When you wish upon a star, is it already dead? An astronomer crunches the numbers
https://theconversation.com/when-you-wish-upon-a-star-is-it-already-dead-an-astronomer-crunches-the-numbers-244915
Many of the claims made on TikTok and elsewhere that the star you wished on is already dead are based on the fact that those stars are millions of light years away, and by the time the light from a star that's millions of light years away reaches us, millions of years have passed since it emitted its light, so the star may no longer exist.
@robbnwa ♬ original sound - mother of heathens
However, according to Driessen, the stars that humans can see with the naked eye are limited to those in the Milky Way galaxy.
The diameter of the Milky Way galaxy is about 100,000 light years, and our solar system is about 26,000 light years away from the center of the galaxy. This means that even the most distant stars on the edge of the galaxy are only about 74,000 light years away, which is far from the 'millions of light years' that are commonly mentioned.
Whether or not you can actually see it depends on the brightness of the star, so the limit is even stricter. Even if you have good eyesight and you are looking at it on a dark, moonless night, the faintest star you can see with the naked eye has a magnitude of about 6.5.
To summarize, the lowest visible star brightness is magnitude 6.5, and we can only see stars that are about 10,000 light years away from Earth. If a star is 10,000 light years away, that means the light it emits takes 10,000 years to reach our eyes.
And if we assume that wishes travel at the speed of light, then it would take 20,000 years for a wish to reach the farthest star visible to the naked eye. In other words, a star's lifespan of 20,000 years is enough.
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About 40% of the stars in the catalog are giants, and the more massive a star is, the shorter its lifespan is. However, in the world of astronomy, even a 'short' lifespan still means at least hundreds of thousands of years. In addition to giants, main sequence stars and subgiants, which are stars that can be seen with the naked eye, have lifespans of more than billions of years.
Taking these points into account, Driessen concluded, 'As an astronomer, I can tell you that the stars you see in the night sky are much closer and much longer-lived than you might think, so it's unlikely that you'd accidentally wish upon a star that's already dead.'
One of the stars that astronomers say is perfect for making wishes on is Alpha Centauri, the fourth brightest star in the sky. This triple star system is only about four light years away from Earth, and eight light years round trip, so it will most likely continue to exist until your wish is granted.
The brightest star, Sirius, is 8.6 light years away, and the Sun-like star Epsilon Eridanus is 10 light years away. Both could burn for millions, or even billions, of years.
If you don't care about the night sky, the safest star to make a wish on is the Sun. It is only eight light minutes away from Earth, and will continue to exist as a main sequence star for another 5 billion years.
'When you wish upon a star, that star is closer than 10,000 light years away and will live for at least hundreds of thousands of years, and likely millions or billions of years - just like the dream you made,' Driessen concluded.
in Science, Posted by log1l_ks