So, a good friend of mine recently posted the following meme:

“According to astronomy, when you wish upon a star….
You’re actually a few million years late.
That star is dead.
Just like your dreams.”

It’s a really depressing thought, perhaps even more depressing than the Nietzsche/Kubrick mashup: “God is dead, and you are alone in an uncaring universe.”[1]

At least with an uncaring universe, something with persist after you are gone. If all the stars are dead before you can even see them, would there even be anything left after we are gone?

But extraordinarily depressing statements require extraordinary evidence. So let’s take this sentence apart and define some things.

First: “According to astronomy” means that we get to (and have to) use astronomy in our proof or disproof. It also likely refers to modern astronomy, as it did not specify a time/technology period. (It may be interesting to see if any answers would be different under astronomy from a different time period, but that will be a secondary investigation.)

Second: “when you wish upon a star….” has a few different readings. The phrase seems to come (at least most recently) from the song written for Disney’s Pinnochio. In that movie, Gepetto says the following:

”
Look! A wishing star!

Starlight, star bright, first star I see tonight…

I wish I may, I wish I might have the wish I make tonight.
”

This is an ‘English language nursery rhyme’ first published in the late 19thC (Wikipedia).

Interestingly, it seems to refer to ‘shooting or falling stars’, or meteors. These would certainly be ‘dead’ (as they are vaporizing in the atmosphere during the ‘wish’, but not for ‘millions of years'[2], as the distance from the viewer to the meteor can be measured in tens or hundreds of kilometers, an insignificant time light distance[3].

But going back to “When you wish upon a star, the meme-maker seems to be clearly referring to the 1940 Disney song and film. Looking at the occurrences of this song in the film:

At 0:34, you can see the image of Gepetto wishing upon the star:

https://www.youtube.com/watch?v=4cHsPCAZlP4

The star is clearly stationary, as can also be seen in the reprise at the end of the film, where Jiminy Cricket is looking upon the same star, still unmoving:

So, this restricts us to the realm of non-moving (or slowly-moving) celestial objects[4]. From the film, the star also seems significantly brighter than the surrounding stars, but the exact extent to which this is true could be dramatic license.

The rhyme mentions ‘first star I see tonight’, which also suggests that the celestial object seen is unusually bright.

So, non-moving (or slowly moving) celestial objects which are bright. This leaves us with comets, planets, and bright stars[4][5].

Comets are objects orbiting through the solar system, and unless they fall into the sun, impact another body, or otherwise breakup, they tend to go on ‘living’ after we see them. (Halley’s comet has been known since at least 240BC.)

Planets could easily look like stars, often like unusually bright stars. Venus was called the ‘evening star‘[6] since antiquity, and it would be bright enough (up to apparent magnitude -4.9) to be significantly brighter than anything else in the sky. Venus could be considered ‘dead’ because it may have once supported life before a runaway greenhouse effect millions of years ago, but this seems an unlikely metaphorical interpretation. Mercury (up to apparent magnitude -2.45) would also be significantly brighter than anything but Venus (and the moon and sun), but has never been ‘alive’, being too close to the Sun[7]. Mars (up to apparent magnitude -2.91) could have been alive at some point, in the same vein as Venus. One or more of the moons of Jupiter (up to apparent magnitude -1.61) or Saturn[8] (up to apparent magnitude 1.47) could have been home to life, under this same metaphorical definition. (The other planets and other bodies in the solar system are too dim to ever be a ‘bright star’.)

So, a planet could be a metaphorical source for this quote, but this seems unlikely, as the quote seems to be referring to the fact that the celestial object is no longer emitting the light itself.

This leaves us with bright stars. Looking at the brightest star in the night sky, Sirius (up to apparent magnitude -1.46), it[9] is only about 8.6 light years away, so we would know in less than a decade if something were to happen there.

The next 91[10] brightest stars are listed here:

https://en.wikipedia.org/wiki/List_of_brightest_stars

You will note that even the furthest among these, Deneb is still only 2600 light years away, much closer than the ‘few million years’ mentioned above.

Based on all this evidence, it would seem that the original meme:

“According to astronomy, when you wish upon a star….
You’re actually a few million years late.
That star is dead.
Just like your dreams.”

is false, which is good, because it would be super-depressing otherwise.

If you enjoyed this sojurn through astronomy, you may like the rest of my blog. Comment below with things you want me to talk about or investigate!

[1]If you have a better source for this, please let me know.

[2]If you want to be pedantic (and I know you do), you could say that meteors are the dead husks of possible (or tidally destroyed) planets, and their burning up in the atmosphere is hundreds of millions of years after they ‘died’.

[3]Much less than a second, even if you assume they impact the Earth’s atmosphere thousands of kilometers away.

[4]A close supernova might also qualify, as it could easily be brighter than anything else in the night sky, would last just long enough to be a ‘wishing star’, and would have been ‘dead’ for some time before it was seen by a human observer. This might indeed be source of this rhyme, where a ‘guest star‘ could inspire wishing and omens. However, looking at this list of supernovae, any supernova which would have been visible as a ‘bright star’ with the naked eye would be at most tens or hundreds of thousands of light years away, not qualifying for the ‘few million years’ mentioned above. I also personally see supernovae more as a seeding of the galaxy with heavier elements, and thus wishing upon one of these would be wishing that the spreading of heavier elements would inspire life to form elsewhere in the universe.

[5]I see no way that any reasonable person could confuse the Sun or Moon with a ‘wishing star’.

[6]Interestingly, the Babylonians had figured out that the ‘evening star’ and the ‘morning star’ were one and the same. It took the Greeks a significant amount of time to discover this themselves, calling them ‘Phosphorus’ and ‘Hesperus’. How many times have there been such dark ages, where knowledge needs to be rediscovered? Was there a Greek ‘renaissance’, or were the Babylonian star charts lost until modern archaeology? Did mere dregs survive to inspire subsequent scientific revolutions?

[7]…unless there was life along the terminator, at some point in the past…

[8]Or [spoiler alert]:

One of the planets themselves!

[9]They, really, as Sirius is a double star, but that is outside the scope of this post.

[10]93, including the Sun, Sirius and the next 91 of magnitude 2.5 or greater.