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Casey DreierDecember 24, 2013

Cosmos with Cosmos Episode 9: The Lives of the Stars

In which we are star stuff

Cosmos with Cosmos is a weekly series that encourages people to get together and watch Cosmos with a cosmo(politan) or drink of your choice. We're posting weekly episode recaps and discussion through February of 2014. This series is made possible by members of the Planetary Society. If you like what you're reading, please consider joining the Society or donating $10 to help support projects like this in the future. To learn more about this series and find out how to watch Cosmos, see our introduction.

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Stars are born. They mature. They die. Their seeming impermanence is a facade; they age just like us. They have lives that come to an end.

But they also create. In episode nine of Cosmos, The Lives of the Stars, we revel in the other big idea of the series: we are all of us interconnected. Everything: biology (episode two), humanity (episode seven), and worlds (episode five) foreshadowed the ultimate fact that the matter that makes up all of us and everything we know (save for hydrogen and some helium) were created in the fiery bellies of massive stars. Their deaths created the building blocks of our life.

Of course, it wasn't always like this. The stars used to be thought permanent, immutable. They were as remote in distance as they were in essence. Our ancient (human) ancestors may have thought the stars powerful beings in the sky. Later, others believed they were the light of heaven shining through holes in the dark cloak of night. People thought they were made of far different stuff than everyday matter on Earth. Aristotelian belief codified the stars as distinctly different, made of stuff later called quintessence (the fifth essence, as opposed to water, air, fire, and earth).

As science progressed, and as we saw in episode seven, humanity learned the true nature of the stars: that they were made out of matter like that found on Earth, but impossibly far away. Even as our understanding grew and the stars joined our pantheon of physical objects, they moved beyond our grasp.

But we are closer to the stars than we ever dreamt. We come from the stars. So do the plants. And the rocks. And the Earth. We are star stuff, reconstituted atoms forged in stars long gone. We share not just a common ancestor, but a common progenitor with every thing around us.

This is Sagan's ultimate answer to the why of astronomy: we are connected to the cosmos. The study of the cosmos is ultimately the study of ourselves. Those lights in the sky, so distant and so mysterious, not only are made of the same stuff as us, but created the stuff of us. It's a beautiful, unifying idea.

The episode itself begins very strong, with a delightful, self-mocking sequence tracing the origin of an apple pie. I found myself wanting Strauss' weighty "Also Sprach Zarathustra," famously used in "2001: A Space Odyssey," as the musical accompaniment. As the pie is served to Sagan, he speaks one of the truly great lines from Cosmos: "If you want to create an apple pie from scratch, you must first invent the universe." What a weird, wonderful line.

We progress to a quick review of atomic theory and exponential numbers, and I was again struck by how simple Cosmos is in its presentation. We have a nearly eight-minute segment of just Sagan speaking to the camera. There are no fancy visualizations, just Sagan with a slice of pie and a piece of paper explaining the concept of atoms. It takes an unusual amount of charisma and force of delivery to maintain the audience's focus for so long. The new Cosmos series, borne of an era rich in cheap computer graphics, probably won't go this route.

After a chemistry lesson and a review of the elements (notably absent: the periodic table) we track the lives of stars that created the 92 mixtures of protons and neutrons presented to us. We revisit the Orion Nebula, but then bring it home to us, tracking the life of our own star, our Sun, and the sad, inevitable destruction of Earth.

Supernovas are mentioned, but I wish that they were given more time in this episode. Elements beyond iron are generated within the massive amount of energy released in the supernova process itself, and supernovae are just plain awesome, in the very literal sense of that word. Type 1a supernovae (when a white dwarf accretes additional matter) are also used to measure absolute distances in astronomy, though I can't fault Cosmos for not mentioning this, as the technique wasn't developed until the 1990s. There are also some very impressive computer simulations that try to reproduce the behavior of supernovae, though the process is notoriously time intensive. These types of supernovae also led to the discovery of the accelerating universe, a topic that will surely be discussed in the new series. The deaths of stars serve not only to sow their matter throughout the cosmos, but also to light our way.

M1, the Crab Nebula, by the Very Large Telescope

European Southern Observatory

M1, the Crab Nebula, by the Very Large Telescope
The Crab Nebula, a supernova remnant, was imaged in 1999 by the Very Large Telescope. The resulting picture uses mapped color from three filters.

While the final lines of episode are poetic and very pretty, the discussion of globular clusters in high polar regions to the Milky Way seem shoehorned in. Maybe ending with a dying star was too depressing. I just couldn't see the connection beyond the fact that "we're talking about stars" -> "globular clusters have lots of stars" -> "globular clusters orbit the Milky Way in a cloud" -> "it would be cool to see the Milky Way galaxy rise from a star in a globular cluster." Would you ever get sunsets in a cluster like that, though? Wouldn't all the other stars in the cluster wash out the relatively dim light of the galaxy? I think back to Asimov's Nightfall here, and assume that everyone on that alien beach would go mad from the number of stars shining in the night sky on the once-in-an-eon total sunset.

The ending aside, this stands as one of Cosmos' strongest episodes. Along with the great The Backbone of Night, which explored the other big idea that the universe is ordered and knowable, The Lives of the Stars presents to us our deepest connection to this knowable cosmos. That all matter shares a common source, that the stars themselves are made of and make constituents of the physical world we experience today, is the ultimate repudiation of Aristotle. The mutable, ugly, imperfect Earth is not only made from the same material as the heavens, it is itself created by them.


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Episode 10: The Edge of Forever »

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Casey Dreier

Chief Advocate & Senior Space Policy Adviser for The Planetary Society
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