Like a diamond in the sky…

Seth Jarvis

News organizations are reporting today that astronomers have found a planet made of diamond orbiting a Sun-like star not too far from here. Is this the beginning of a new scientific discipline, the study of Astro-Bling?

The planet everyone’s talking about goes by the name “55 Cancri e.”  The central star is called 55 Cancri, denoting a star in the constellation Cancer the Crab. Planets around stars other than our Sun are named using alphabetical suffixes to the star’s name in the order in which they were discovered. The “e” suffix for Cancri 55 e means it is the fifth planet discovered around the star 55 Cancri.

Some news articles claim that the star 55 Cancri is visible to the naked eye.  Well… it is, barely, if you live in the middle of nowhere with absolutely no light pollution, you have a crystal-clear moonless night sky, and you have 20/20 vision.

With that caveat in mind, if you want to gaze in the general direction of Cancri 55 look roughly midway between the constellations of Gemini and Leo.  In October that will involve looking towards the eastern sky at around 6 AM.

55 Cancri is a star in the constellation Cancer. Look to the east at about 6AM. Cancer lies between Gemini and Leo.


55 Cancri e is what astronomers refer to as a “Super Earth” in that it is not a ginormous Gas Giant planet like Jupiter or Saturn, but instead something bigger than Earth, but not by much.

Cancri 55 e is a "Super-Earth," a little bigger than Earth, but a lot smaller than Jupiter.


55 Cancri e is about twice the diameter of Earth and about eight times as massive. But here’s what has the newswires buzzing today – by refining what is known of this strange planet’s orbit and its interactions with its parent star, astronomers are coming to the conclusion that 55 Cancri e is, to a large degree, made of highly pure crystallized carbon, i.e., diamond.

So… there’s a diamond bigger than Earth 40 light years from us. What do we do about that?

Before you recommend that De Beers fund an expedition to 55 Cancri e to cash in on that enormous diamond, consider this: The 55 Cancri system is “only” about 40 light years away.  In terms of our 100,000 light year diameter galaxy, 55 Cancri is practically next door.  If our galaxy were the size of North America then at that scale the distance between our solar system and the 55 Cancri system would be less than two miles – an easy walk.

Don’t let that relative nearness fool you. The Milky Way is a big galaxy, and even “only” 40 light years is a mind-numbing distance. If you launched the fastest rocket ever launched by NASA (36,000 miles per hour) towards 55 Cancri then that journey, one-way, would take 800,000 years.

But let’s say you figure out a way to go much faster than the speed of light (no small trick) and you’re still keen to get at that huge diamond.  What next?

The planet 55 Cancri e orbits its parent star very, VERY close.  How close?  Look to our own solar system for a clue. Mercury is the closest planet to our Sun and it orbits the Sun in only 88 days. 55 Cancri e orbits its star in less than 18 hours.

55 Cancri e is 25 times closer to its star than Mercury is to our Sun. A "year" on 55 Cancri e is less than 18 hours long.

Orbiting that close to its star, 55 Cancri e gets hot. How hot?  Over 3,000 degrees Fahrenheit. It would be a rare spaceship that can visit 55 Cancri e for any length of time without vaporizing.  And that temperature is just at the planet’s cloud tops.

Yes, I said clouds.  Clouds of super-heated steam. Then there’s what lies below the clouds, separating you from the diamond, that you next have to worry about.  Near the surface of the planet is water so hot and under so much pressure it is referred to as a “supercritical” liquid. Supercritical water is sometimes created spontaneously by the operating temperatures and pressures found at the tips of steam turbine blades, which the supercritical water then promptly dissolves.

Supercritical fluids are fantastically effective as solvents. That means that you, the diamond-hunter, after your 40 light year journey to the 55 Cancri system on a quest for wealth beyond the dreams of avarice, now need to figure out how to get your spaceship through miles and miles of supercritical water that will do to your spaceship’s hull exactly what a pot of boiling water does to a sugar cube. Good luck with that.

Then there is the enormous layer of diamond, perhaps hundreds of miles thick. How exactly do you go about carving out a chunk of this stuff? What tools do you use to dig into a landscape of super-hot, super-pressurized solid diamond?

Isn’t it likely that long before we acquire the ability to travel dozens of light years in a reasonable amount of time, and survive an insanely hostile and ship-dissolving environment of extreme temperatures and pressure, we will have decided that we really don’t need to explore the galaxy in search of diamonds?  When we can travel 40 light years in less than one human lifetime then the odds are pretty good that diamonds will have to have become boring and commonplace for us.

If and when we begin to travel between the stars, we won’t be going in search of jewels; it will be in search of something far more valuable – the experience of exploration itself.


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