Starlight Dreams: The Science Behind Wishing Upon Stars

Since ancient times, people have wondered what the twinkling spots in the sky are. Stars, with their distant and seemingly eternal presence, became symbols of the universe’s mystery and humanity’s dreams and aspirations. It is likely that from this sense of wonder the tradition of making a wish upon a star emerged.

Even now, despite our advanced technologies and extensive knowledge of astrophysics, we still look up in the sky and make wishes upon stars. However, a recent idea that has gone viral on social media challenges this sentimental tradition, offering a sobering perspective.

“According to astronomy, when you wish upon a star you’re a million years too late. The star is dead, just like your dreams.”

But is the star we see really dead?

We have some good news for all those who enjoy making wishes upon stars.

A Long Journey Through Light and Time

Distances in space are enormous, and using kilometres or miles becomes impractical. The distance to stars is measured by light years. The light from the star takes years, decades, or even millennia to reach Earth. A light year is the distance that light travels in one year in a vacuum (empty space). For example, instead of saying “50 trillion kilometres,” astronomers say “about 5 light years.” Light years also gives a sense of time. Looking at an object 1,000 light years away means you’re seeing it as it was 1,000 years ago. 

Light travels at a speed of approximately 299,792 kilometres per second (186,282 miles per second) in a vacuum. Thus, in one year, light travels about 9.46 trillion kilometres (5.88 trillion miles).

So, when we look at a star, we are looking into the past.

Are The Stars We See Still Alive?

According to the viral video, “you’re a million years too late”. Meaning the light from the star has been travelling for millions of years to reach your eyes, so by now the star is millions of years older and most likely dead. However, most stars visible to the naked eye are relatively close in cosmic terms and are likely still alive.

All the stars we can see are inside our galaxy, the Milky Way. The Milky Way is approximately 100,000 light years across. It sounds very far away, but not “millions of years”, though.

The Death Of Stars

Stars are giant spheres of hot gas – primarily hydrogen, with some helium and small amounts of other elements. Each star has its own life cycle, ranging from a few million to trillions of years.

As a star approaches the end of its life, its core runs out of hydrogen fuel to convert into helium. The energy produced by fusion creates internal pressure that balances gravity’s tendency to maintain the star’s structure, so the core starts to collapse. The intense compression raises the core’s temperature and pressure, causing the outer layers of the star to gradually expand and puff up.

However, the mass of the star determines the specific details of the final stages of the star’s life cycle.

Link to image

Small stars expand into red giants. For the medium-sized stars, the outer layers are shed into space, creating a stunning planetary nebula. The remaining core becomes a white dwarf, a dense, Earth-sized remnant that gradually cools over billions of years. Eventually, the white dwarf fades into a black dwarf – a theoretical stellar remnant that has yet to form since the universe isn’t old enough for black dwarfs to exist.

When massive stars run out of fuel, they explode as supernovae – powerful and luminous events, leaving behind a neutron star or a black hole.

Most of the stars visible to the naked eye are massive stars with relatively short lifespans of a few million years. This means there is a really high probability that the star you’re wishing upon is still alive.

The Safest Options For Your Wishes

If you still have doubts or feel uneasy about wishing upon stars that might no longer exist, here are a few safer alternatives for you:

• Alpha Centauri – the nearest star system. It is approximately 4.37 light years away. If you wish upon a star, and that star is Alpha Centauri, it started its journey over four years ago
• Sirius – the brightest star in the sky. It is 8.6 light years away
• Epsilon Eridani – a star that is approximately ten light years away from our planet. It is a young star, a little under a billion years old. 
• And of course the Sun – only about eight light minutes away, meaning sunlight takes approximately eight minutes to reach Earth. The safest option ever!

When we wish upon a star, we are looking into the past, making a wish upon light that began its journey long ago. Yet, that doesn’t mean our wishes cannot come true. So, keep dreaming and stargazing!