Science Communication | Ray Garner

Charting the Heavens

Fri, 21 Jul 2023 00:00:00 +0000

Over the last several years, whenever I had some spare time, I worked on a little project to chart the 88 constellations in Python. I was heavily inspired by several different people online. Most of the impetus came from the work of two different people: and . Those two existing projects (the latter being on an indefinite hiatus) really helped me out, both with their code and their knowledge of existing databases. –>

I have also always been interested in the mythology and history of the constellations, and I wanted some way to incorporate that. I decided that these charts could be the impetus for writing up an “Observer’s Guide” to the constellations, complete with information about the history/mythos, meteor showers, stars, and deep sky objects for each constellation. This part of the project probably took the longest, but eventually I got it done!

Below is a small gallery of a few constellations so you can get an idea of what the charts look like. I tried to emulate the Sky & Telescope charts that are found on the Wikipedia pages for each constellation. The full Python code, databases used, and all the discussion can be found on . The “Observer’s Guide” can also be found there as a PDF. Let me know if you have any questions or suggestions!

Astronomy 101

Mon, 18 Oct 2021 00:00:00 +0000

In the spring of 2020, The Event happened. With everyone stuck at home and not being able to see anyone, online resources boomed. In an effort to keep myself sane, and to share my love of astronomy, I started offer (mostly) weekly public talks about various astronomy-related things. I talked about the life and death of the Universe, about my research project, about where life is in the Universe, what the Star of Bethlehem could’ve been, and some more complex things, like an introduction to dark matter, spiral galaxies, and a tour of the solar system.

However, while those presentations were good, they were sometimes aimed a little too high for my audience. Essentially, I was giving talks I would’ve given to a class of astronomy majors rather than the general public. The astronomy talks went on hiatus during the winter holidays so that everyone could spend safe, socially distant time with their families and so that I could recuperate from having to come up with a talk every week.

The astronomy talks have now returned in the Spring of 2021, nearly a year after The Event. This time, my goal is to rectify some of the mistakes I made the previous year. To do that, I’m calling these talks “Astronomy 101.” As the name suggests, I’m starting everything from a more basic level, spending time walking through basic mechanics, the nature of light and matter, and then moving on to the solar system and diving into stars and galaxies. Basically, I’m walking through the textbook The Cosmic Perspective.

Furthermore, in an effort to be considerate of people’s time, if someone is unable to attend the in-person virtual ecture (what a weird combination of words), I have pre-recorded each lecture and posted them to YouTube for people to watch at their leisure. This will be a landing page for those videos, keeping them updated with a summary of each (roughly) hour-long video.

The first in the lecture series is titled "Introduction to the Universe." In this talk, we cover the size and scale of the Universe, in both space and time dimensions. We also talk about the various motions the Earth goes through: rotating on its axis, orbiting the Sun, the Sun orbiting the center of the Milky Way, as well as moving randomly with respect to the local stars, and the Milky Way moving in an expanding Universe. We end with a brief discussion of the human adventure of astronomy. (Presented on February 28, 2021)

The second in the series is titled "The Night Sky." Here, we talk about how we understand the things we see in the night sky given our understanding of the Universe. We talk about the celestial sphere, why stars change depending on the time of year, and how the seasons work. We also go into detail about the phases of the Moon and how both lunar and solar eclipses work. We end by mentioning the weird apparent retrograde motion the planets go through and hint at what the Greeks attempt to solve in next week's talk. (Presented on March 7, 2021)

Any good astronomy teacher will tell you that eventually we have to talk history. In this "The Science of Astronomy" lecture, we delve into the ancient Greek origins of astronomy, talking about the geocentric model of the Universe. Then we delve into the Copernican revolution and talk about the personalities of Copernicus, Tycho, and Kepler. Especially important are Kepler's Laws of Planetary Motion! We end with a discussion of what makes science science. (Presented on March 14, 2021)

To talk about the goings-on in the Universe, it is necessary to have an understanding of "Motion, Energy, and Gravity." Here, we talk about just that! We spend some time getting our definitions straight, before moving on to the man of the hour, Isaac Newton, and his laws of motion. We explore the deeper truths that are the conservations laws and how to apply them. Then we talk about gravity and explain how gravity works to create orbits, the tides, and Galileo's Leaning Tower of Pisa experiement. (Presented on March 21, 2021)

Except for a few objects, astronomers can't go to an object and physical measure its properties. That's why its important to understand how "Light and Matter" interact and how we can deduce the nature of an object from the light it emits or reflects. We talk just about that in this lecture, covering the types of spectra, and how we can tell the composition, temperature, and motion of an object from its light. (Presented on March 28, 2021)

Last week we talked about all of the information we can learn from light, now we need to talk about how to collect that light and that means "Telescopes!" Essentially astronomers want telescopes to be the biggest they can be to maximize light-collecting area and to minimize the angular resolution. We talk about how astronomers use those telescopes to do imaging observatiions, spectroscopic observations, and timing observations. We also explain the three main reasons why ground-based observing is limited and explore the wide variety of telescopes we put in space to observe the entire electromagnetic spectrum. (Presented on April 4, 2021)

We've finally done it! We've finished with the basic physics lessons and we can move on to give an "Introduction to the Solar System!" Here, we introduce the idea of comparative planetology and use it to describe the four types of basic patterns we see in the solar system. In order to do that, we go through a brief tour of the planets, the first and last time we will do that in this series. We end by describing the types of spacecraft that we use to learn about the planets and other objects in the solar system. (Presented on April 11, 2021)

We sort of ended last week on a cliffhanger, having talked about all of these large-scale patterns that we see in the solar system without explaining how they came to be. We attempt to do just that by explaining the "Formation of the Solar System." We cover the nebular theory and how it accounts for those patterns very well. We show the pieces of evidence, both observational and computational, that suport the theory as well as explaining that this wasn't all "planetary destiny." We end with a brief talk on radiometric dating and the age of the solar system. (Presented on April 18, 2021)

In this talk, we make our first attempt at comparative planetology by discussing the general geological processes that have shaped the "Planetary Geology" of each terrestrial world and then diving into how those processes explain the features we see on each world individually. We find that Mercury and the Moon are both heavily cratered worlds with no geologic activity as of late, that Mars is slowing down in its geologic activity, and Venus and the Earth should both still be geologically active! (Presented on April 25, 2021)

After having discussed the surfaces of the terrestrial worlds, we now move to a discussion of their "Planetary Atmospheres." Using the Earth as a template to our understanding, we discuss the basic atmospheric processes occurring on Venus, Earth, and Mars. We learn that the greenhouse effect isn't all bad and is actually necessary for liquid water to exist on the surface of the Earth. We end our discussion with a brief introduction to human-caused climate change and the consequences of inaction. (Presented on May 2, 2021)

We are now done with the terrestrial planets and we can finally move to the outer solar system and "The Jovian Planets." This time we use Jupiter as a template to discuss the internal structures and atmospheres of each of these gas giants. Since they don't have surfaces for us to geologize, we instead turn our attention to the plethora of moons that encircle each planet. We end with a brief discussion on their ring systems. (Presented on May 9, 2021)

This is the last talk about our solar system! We finally catch up with all of the smaller things we've been sidestepping along the way, the "Asteroids, Comets, and Dwarf Planets!" After giving a brief history of those terms, we talk about the asteroids and comets in detail, covering both their physical properties and orbital properties. Then, we talk about the only dwarf planet we really know tons of information about, Pluto! Hopefully, I've illustrated just how much information New Horizons gave us when it flew by Pluto in 2015. We end by talking about impacts by asteroids and comets, including two relatively recent ones, both in Russia. (Presented on May 16, 2021)

Rounding up our large section on solar systems is all of the other "Exoplanets" in the Galaxy! The main problem with finding exoplanets is exactly that: finding them. There are three big methods that astronomers use and we talk about all three here and the biases inherent in these detection methods. We also compare the known exoplanets to the planets of our solar system and find that there are a wider variety of exoplanets than what we have in our solar system. Do we have to rethink our nebular theory of solar system formation? (Presented on May 23, 2021)

Now that we've ended our journey through the solar system, we're taking a quick break from astronomy to brush up on our relativity! In "Space and Time" we talk about how Einstein's Theory of Special Relativity says that all motion is relative, but that the speed of light in an absolute. We explore these concepts by using thought experiments, where, with two key assumptions, the results of time dilation, length contraction, and mass increase follow logically. (Presented on May 30, 2021)

Just as Einstein did after discovering special relativity, we will also generalize it to general relativity. In "Spacetime and Gravity" we leave the thought experiments behind and discuss the equivalence principle and the multidimensional nature of spacetime. Obviously this new view of the Universe has some profound effects on our understanding of it, and we see how general relativity leads naturally to the idea of black holes, gravitational time dilation, and redshift. But don't take my word for it, there are several easy-to-understand experiments that verify general relativity as well! We'll discuss them all. (Presented on June 6, 2021)

Now that we're done talking about the really big stuff à la relativity, let's move to the subatomic world and talk about "The Building Blocks of the Universe." Here, we give a brief introduction to the world of particle physics with its quarks, leptons, and bosons all wrapped up nicely in the Standard Model. Then we describe the two big laws of quantum mechanics: Heisenberg's Uncertainty Principle and Pauli's Exclusion Principle. But we're not just talking about this stuff for fun! There are astronomical implications to consider as well: stellar lifetimes, quantum tunneling, and black hole evaporation! (Presented on June 13, 2021)

To begin our broader discussion on stars, let's start by talking about the star we know the most about "Our Star, the Sun." We cover why the Sun shines and how its interior is organized into different zones. We take a journey to the core to see how hydrogen is fused into helium and then follow that energy outwards to talk about the solar cycle of sunspots and flares. Hopefully this will give everyone a good starting point to the terminology of stars! (Presented on June 20, 2021)

We started with the Sun, but the Sun is just one star. Let's talk about how astronomers "Survey[ing] the Stars." We answer three questions: how do we measure stellar brightness, how do we measure stellar temperature, and how do we measure stellar masses? Next, what happens when we arrange stars by their intrinsic brightness (their luminosity) and their temperature? We get an HR diagram and the stars arrange themselves into several groups. Finally, we end our discussion by talking about star clusters and how useful they are. The stuff in this talk will become very important for the coming weeks, so make sure you understand this stuff! (Presented on June 27, 2021)

Now that we've got some stellar basics out of the way, we're going to start a three-part mini-series on stars. The natural place to begin is "Star Birth!" Space isn't just an empty vacuum, there's gas and ust everywhere (to much annoyance). Some of that gas and dust is cold enough and dense enough for gravity to take over and collapse the entire gas cloud into a family of stars. We talk about how stars form, starting from gas clouds to protostars and on to true stars with their hydrogen-fusing cores. We also brielfy discuss the wide range of stellar masses we find in the Galaxy. Tune in next week for the remainder of a star's lifetime! (Presented on July 11, 2021)

What do stars do with the rest of their lives once they're formed? The answer ot that question is "Star Stuff!" Mass is not only an important property of a star, but it is also the most defining characteristic of a star. It determines how long the star will live and how it will evolve! Low-mass stars will only ever get hot enough to fuse hydrogen into elements like carbon and oxygen. Meanwhile, high-mass stars will fuse elements all the way up to iron. What happens after iron is quite explosive! (Presented on July 18, 2021)

Once stars are done fusing as many elements as they can, their bodies litter "The Stellar Graveyard." Stellar remnants come in three types. The low-mass stars will eventually shed their outer layers, leaving behind their exposed core as a white dwarf. Some stars will be so massive that instead of electrons, they'll leave behind a ball of neutrons known as a neutron star. And even more massive objects will skip all of that and end up as a black hole. All of these objects are weird in their own right and are the subject of many a science fiction novel. Learn the truth behind the fiction here! (Presented on August 1, 2021)

Now that we're done with stars, let's look at the giant groups of them known as galaxies. And what better place to start our galactic discussion than with "Our Galaxy, the Milky Way!" The Milky Way has a lot to offer us: an understanding of galactic structure; of galactic recycling, wherein stars scatter their enriched guts across the Galaxy, only to have those guts reformed in a new generation of stars; and galactic evolution, as we look at the differences between disk and halo stars. Finally, we see how nicely our observations match our theory as we briefly talk about minor galactic mergers. All of this information will be expanded upon and generalized when we talk about galaxies in general next week. Stay tuned! (Presented on August 8, 2021)

If we're going to talk about galaxies in general, we've got to talk about cosmology a bit too, so in "Galaxies and the Foundations of Modern Cosmology" that's exactly what we do! There are three broad categories of galaxies: ellipticals, spirals, and irregulars. Patterns exist between these broad types where ellipticals are generally more massive, brighter, and redder than the blue, star-forming spirals. Spirals also often exist in isolation or in small groups, whereas ellipticals exist in large groups and clusters of galaxies that number in the thousands. But to truly understand galaxies and their evolution, we need to introduce distance measurements to the furthest reaches of the Universe. We do so by talking about the Cosmic Distance Ladder, measurements of different objects that build and rely on each other. (Presented on August 15, 2021)

We can only understand "Galaxy Evolution by looking at snapshots of many different galaxies throughout the entire Universe. When we do hat, we get a basic model of galaxy formation. The growth of a galaxy might depend on its initial conditions, whether the protogalactic gas cloud was rotating or dense. It might also depend on galaxy mergers, where two (or more) galaxies crash into each other in a cosmic collision. After a galaxy has grown, it might go through a starburst phase, rapidly forming stars in just a few hundred million years, becoming incredibly luminous. Some galaxies are even active! Their supermassive black holes are spewing out radiation and shutting down star formation throughout the galaxy! Learn all that and more here. (Presented on August 22, 2021)

Now we're moving on to even bigger things that galaxies when we talk about "The Birth of the Universe." In the very early Universe, the conditions were radically different from the Universe we know of today. Matter and antimatter were spontaneously created and annihilated; the four forces that exist were likely combined into one "theory of everything"; and fusion happened not just in the cores of stars, but across the entire Universe! All that sounds nice, but what's the evidence? The two big pieces of evidence we have for the Big Bang are the cosmic microwave background and the abundance of helium in the Universe. Finally, we answer some outstanding questions from the previous talk, so you'll definitely want to check it out. (Presented on August 29, 2021)

We've talked about a lot of different objects in this series, but what would you say if I told you that everything we've talked about only makes up about 5% of the Universe? The rest of it is "Dark Matter, Dark Energy, and the Fate of the Universe." We spend most of the talk talking about the few things we know about dark matter: it flattens out the orbital speeds of stars in galaxies, it binds galaxies together in clusters, and it even supports large-scale structure formation throughout the Universe. What could it be, you ask? We don't really know. But despite all those unanswered questions, we know even less about dark energy. And that's a problem because the amount of dark energy in the Universe has a huge impact on the eventual fate of the Universe. Find out what that is here! (Presented on September 5, 2021)

To end this Astronomy 101 series, we take a stroll through “An Astronomer’s Perspective” of the Universe. This talk is less about introducing new scientific ideas, and more about thinking back to everything we’ve talked about and putting it together. We wax poetic about the size of the Universe in both space and time. We tell the story of three amazing women who helped us understand the stars. And then you hear directly from me, what I think of when I look up at the night sky. There’s no video for this talk, but you can read the talk in this blog post. Thanks for coming along for the ride. (Presented on September 12, 2021)

An Astronomer's Perspective

Tue, 21 Sep 2021 00:00:00 +0000

This post was the script to the final talk in my Astronomy 101 lecture series originally presented on September 12, 2021. Although there is no video of thet alk and I don’t plan on making one available, here is the script that I put together for that night. Parts of it were heavily borrowed from Neil deGrasse Tyson’s “Cosmos: A Spacetime Odyssey” and I acknowledge that here. I claim no rights to those parts.

Over these past few weeks, we have discussed some big ideas. We’ve explored to the furthest reaches of the Universe and through the vast eons of time. That often leaves people feeling tiny and insignificant, even small. Well, in the context of the cosmos, we are small!

But the thing is, we may just be little guys living on a speck of dust, afloat in a staggering immensity, but we sure don’t think small. In all our lives, there comes a time when we first realize that we aren’t the center of the Universe, that we belong to something much greater than ourselves. It’s part of growing up. And as it happens to each of us, so it began to happen to our civilization in the sixteenth century.

Imagine a world before telescopes, when the Universe was only what you could see with the naked eye. It was obvious that the Earth was motionless and that everything in the heavens—the Sun, the Moon, the planets, the stars—revolved around us. But then a Polish astronomer and priest named Nicolaus Copernicus made a radical proposal: the Earth was not at the center. It was just one of the planets, and, like them, it revolved around the Sun.

Many religious figures, like the Protestant reformer Martin Luther, took this idea as a scandalous affront to Scripture. They were horrified! But for one man, Copernicus didn’t go far enough. His name was Giordano Bruno. He longed to bust out of that cramped little universe. Even as a young Dominican monk in Naples, he was a rebel. Bruno hungered to know everything about God’s creation. He dared to read books banned by the Church and that was his undoing. In one of them, an ancient Roman, a man already dead for more than 1500 years, whispered to him of a universe far greater, one as boundless as his idea of God.

Lucretius, in his book “On the Nature of Things,” asked the reader to imagine standing at the edge of the universe and shooting an arrow outward. If the arrow keeps going, then clearly the universe extends beyond what you thought was the edge. But if the arrow doesn’t keep going and hits a wall instead, then that wall must lie beyond what you thought was the edge of the universe. Now if you stand on that wall and shoot another arrow, there are only the same two possible outcomes: it either flies forever out into space or it hits some boundary where you can just stand and shoot yet another arrow.

Either way, the Universe is unbounded. The cosmos must be infinite. This made perfect sense to Bruno. The God he worshiped was infinite, so how, he reasoned, could Creation be anything less? These heretical ideas were his undoing. When he learned an indictment was being prepared against him by his monastery in Naples, he fled the city. That would be the last steady job he ever had.

And then, when he was only 30, he had the vision that sealed his fate. In his dream, he awakened to a world enclosed inside a confining bowl of stars. This was the cosmos of Bruno’s time. As he walked to the edge of this universe, Bruno experienced a sickening moment of fear, as if the bottom of everything was falling away beneath his feet.

But he summoned up his courage.

“I cleave the heavens and soar to the infinite. And while I rise from my own globe to others And penetrate ever further through the eternal field, That which others saw from afar, I leave far behind me."
–Giordano Bruno, “On the Infinite Universe and Worlds”, 1584

L'Atmosphere: Météorologie Populaire by Camille Flammarion. The illustration is of a dome of stars with a landscape underneath it. A man has his head stuck out of the dome looking up at the universe beyond." style="width:350px;height:auto"/>

Camille Flammarion, L'Atmosphere: Météorologie Populaire (Paris, 1888), p. 163. Colorized by Susanna J. Magruder. Courtesy History of Science Collections, University of Oklahoma Libraries.

The revelation of this immensity was like falling in love. Bruno became an evangelist, spreading the gospel of infinity throughout Europe. He assumed that other lovers of God would naturally embrace this grander and more glorious view of Creation.

Instead, he was excommunicated by the Roman Catholic Church in his homeland, expelled by the Calvinists in Switzerland and by the Lutherans in Germany. Eventually, Bruno found a brief lectureship at Oxford University where he could freely spread his view on infinity. However, even there his views were controversial. George Abbot, then Vice-Chancellor of the University and later Archbishop of Canterbury, mocked Bruno for supporting “the opinion of Copernicus that the Earth did go round, and the heavens did stand still; whereas in truth it was his own head which rather did run round, and his brains did not stand still.” A wiser man would have learned his lesson, but Bruno was not such a man.

He couldn’t keep his soaring vision of the cosmos to himself, despite the fact that the penalty for doing so in his world was the most vicious form of cruel and unusual punishment. Giordano Bruno lived at a time when there was no such thing as the separation of church and state or the notion that freedom of speech was a sacred right of every individual.

Recklessly, Bruno returned to Italy. Maybe he was homesick, but still, he must have known that his homeland was one of the most dangerous places in Europe he could possibly go. It wasn’t long before Bruno fell into the clutches of the Catholic Church. This wanderer, who worshiped an infinite universe, languished in confinement for eight years. Through relentless interrogations, he stubbornly refused to renounce his views.

Why was the Church willing to go to such lengths to torment Bruno? What were they afraid of? If Bruno was right, then the sacred books and the authority of the Church would be open to question.

Finally, the charges were brought. Among them were: holding opinions contrary to the Catholic faith about the Trinity and divinity of Christ; regarding the virginity of Mary, mother of Jesus; pertaining to Jesus as Christ; and claiming the existence of a plurality of worlds and their eternity. Once again, Bruno refused to recant his claims.

On January 20, 1600, Pope Clement VIII declared Bruno a heretic and the Inquisition sentenced him to death. “Perhaps you pronounce this sentence against me with greater fear than I receive it,” Bruno responded.

Ten years after Bruno’s martyrdom, Galileo first looked through a telescope, realizing that Bruno had been right all along. The Milky Way was made of countless stars invisible to the naked eye, and some of those lights in the sky were actually other worlds.

Bruno was no scientist. His vision of the cosmos was a lucky guess because he had no evidence to support it. Like most guesses, it would well have turned out to be wrong. But once the idea was in the air, it gave others a target to aim at.

And over the past several weeks, we too have soared through the infinite. We have left the Earth for the furthest reaches of space. Our nearest neighbor, the Moon, has no sky, no ocean, no life. Just the scars of cosmic impacts. Our star, the Sun, powers all the wind, waves, and life on the surface of our little world. It also holds all the worlds of the solar system in its gravitational embrace, starting with hot and fast-footed Mercury to cloud-covered Venus, where a runaway greenhouse effect has turned it into a kind of hell.

The red planet Mars is a world that has interested humanity for centuries. And despite it being the most explored planet, it still holds mysteries for us. A belt of rocky asteroids circles the Sun between the orbits of Mars and Jupiter. It is also host to the dwarf planet Ceres, the only spherical body in the belt, but still only 7% the size of Earth.

With its four giant moons and dozens of smaller ones, Jupiter is like its own little solar system. Its Great Red Spot is a hurricane three times the size of our whole planet that’s been raging for centuries. The crown jewel of the solar system, Saturn, is ringed by freeways of countless orbiting and slowly tumbling snowballs. Uranus and Neptune, the outermost planets, were unknown to the ancients and only discovered after the invention of the telescope. Beyond the outermost planet, there is a swarm of tens of thousands of frozen worlds, and Pluto is one of them.

The deepest waters of the vast cosmic ocean and their numberless worlds lie ahead. From out here, the Sun may look like just another star. How many stars? How many worlds? We live in the Milky Way Galaxy in a trailing outer arm about 30,000 lightyears from the center of our grand spiral. Our galaxy is part of a few dozen in our Local Group, including our nearest neighbor the Andromeda Galaxy. But even then, we are just one of thousands of galaxies in the Virgo supercluster. Each galaxy contains billions of suns and countless worlds. Yet the entire Virgo superlcuster itself forms a tiny fraction of our Universe.

But the Universe is not only immense in size, it is also staggeringly immense in time. How can we humans, who rarely live as long as a century, hope to grasp the 13.8 billion year history of the cosmos?

Let’s compress it into a single calendar year. The Cosmic Calendar begins on January 1st with the birth of our Universe and ends with the present day on December 31st. On this scale every month represents about a billion years and every day about 40 million years.

Let’s go to January 1st, the Big Bang. Our entire Universe came into being from a point smaller than a single atom. Space itself exploded in a cosmic fire, launching the expansion of the Universe and giving birth to all the matter and energy we know today. Recently, I showed you the strong observational evidence to support the Big Bang: the amount of helium and deuterium in the cosmos and the glow of the cosmic microwave background radiation.

As it expanded, the Universe cooled, and there was darkness for about 200 million years. Gravity was pulling together clumps of gas and heating them until the first stars burst into light on January 10th. On January 13th, these stars coalesced into the first small galaxies. These galaxies merged to form still larger ones, including our own Milky Way, which formed about 11 billion years ago on March 15th of the cosmic year.

As these galaxies formed, stars flashed each time they ran out of fuel in a supernova. These supernovae would disturb nearby clouds of gas and star would start condensing out of them like raindrops. Stars get so hot that the nuclei of atoms fuse together deep within them to make the oxygen we breathe, the carbon in our muscles, the calcium in our bones, and iron in our blood; all of it was cooked in the fiery hearts of long-vanished stars. You, me, everyone and everything, is made of star stuff. This star stuff is recycled and enriched, again and again, through succeeding generations of stars.

How much longer until the birth of the Sun? A long time. It won’t begin to shine for another six billion years. Our Sun’s birthday is August 31st on the Cosmic Calendar, about 4.5 billion years ago. As with the other worlds of the solar system, Earth was formed from a disk of gas and dust orbiting the newborn Sun. Repeated collisions produced a growing ball of debris. The Earth took one hell of a beating in its first billion years. Fragments of orbiting debris collided and coalesced until they snowballed to form the Moon; a souvenir of that violent epoch.

As the Earth cooled, seas began to form. Life began here, on September 21st, 3.5 billion years ago on our little world. We still don’t know how life got stared. The origin of life is one of the greatest unsolved mysteries of science. Regardless of how it started, on November 9th, life was breathing, moving, eating, responding to its environment.

December 17th was quite a day. Life in the sea really took off, exploding with a diversity of larger plants and animals. Forests, dinosaurs, birds, insects, they all evolved in the final week of December. The first flower bloomed on December 28th. As these ancient forests grew and died and sank beneath the surface, their remains transformed into coal, which we use to power and imperil our civilization.

Then at 6:24 AM on December 30th, an asteroid collided with what would later be Mexico and wiped out the dinosaurs, the lords of the Earth. Still no signs of us.

In the vast ocean of time that this calendar represents, we humans have only evolved within the last hour of the last day of the cosmic year. All of recorded history occupies only the last 14 seconds, and every person you’ve ever heard of lived somewhere in there. All those kings and battles, migrations and inventions, wars and loves, everything in the history books happened here.

It’s 9:45 on New Year’s Eve. Three and half million years ago, our ancestors stood up on two feet and suddenly our eyes were no longer fixed on the ground. Now we were free to look up and wonder. We’re so young on the timescale of the Universe that we didn’t start painting our first pictures until the last 60 seconds of the cosmic year, a mere 30,000 years ago. This is when we invented astronomy. In fact, we’re all descended from astronomers. Our survival depended on knowing how to read the stars in order to predict the coming of the winter and the migration of the wild beasts.

And then, around 10,000 years ago, there began a revolution in the way we lived. Our ancestors learned how to shape their environment, taming wild plants and animals, cultivating land and settling down.

This changed everything. For the first time in history, we had more stuff than we could carry. We needed a way to keep track of it. At 14 seconds to midnight, or about 6,000 years ago, we invented writing. Writing allowed us to save our thoughts and send them much further in space and time. Tiny markings on a clay tablet became a means for us to vanquish mortality. It shook the world.

Moses was born 7 seconds ago; Buddha, 6 seconds ago; Jesus, 5 seconds ago; Mohammad, 3 seconds ago. It was not even 2 seconds ago that, for better or worse, the two halves of the Earth discovered each other. And it was only in the very last second of the Cosmic Calendar that we began to use science to reveal nature’s secrets and her laws. The scientific method is so powerful that in a mere four centuries, it has taken us from Galileo’s first look through a telescope at another world to leaving our footprints on the Moon. It allowed us to look out across space and time to discover where and when we are in the cosmos. We are a way for the cosmos to know itself.

And we have come to know it well not only as a scientific endeavor, but as a human endeavor too. A long time ago, in a world lit only by fire, our relationship with the stars was far more personal. Night after night, we watched the stars. In a time when our imaginations were the only stage where stories came to life, before there were movies or TVs or electronic devices of any kind, every human culture connected the dots to form their own pictures.

These images became the illustrations of a storybook that, on a deeper level, was also a survival manual. The names and personalities of the gods, heroes, farm animals, or familiar objects varied from culture to culture. But there was one particularly gorgeous group of stars known to the ancient Greeks and to us today as the Pleiades, a star cluster that formed about 100 million years ago (2.5 days on the Cosmic Calendar). Each of the stars in the Pleiades is some 40 times brighter than our Sun, and the brightest, Alcyone, outshines our Sun 1,000 times.

The Pleiades in Taurus
Digitized Sky Survey, 2004

For ages, the Pleiades have been used as an eye test for people all over the world. If you could see six of them, you were considered normal. If you saw more than seven, you were an ideal candidate for a warrior or scout.

Among the ancient Celts and druids of the British Isles, the Pleiades were believed to have a haunting significance. On the night of the year that they reach the highest point in the sky at midnight, the spirits of the dead were thought to wander the Earth. This is believed to be the origin of the holiday once known as Samhain, now called Halloween.

All over the Earth, our ancestors told wonderful stories to explain how the Pleiades came to be in the sky. For the Kiowa people of North America, it happened something like this.

Long, long ago, some young women snuck away from camp one night to dance freely beneath the stars. It wasn’t long before some bears discovered them and chased them through the wilderness. Eventually, the girls found a tall rock and climbed it. The girls begged the spirits in the rock to save them. The rock heard their cries and grew taller until it became what is today known as Devils Tower. The maidens were transformed into the stars of the Pleiades, which may be seen hanging above the tower in mid-winter.

The ancient Greeks also saw those seven jewels as seven maidens, the seven daughters of Atlas, pursued not by bears, but by Orion the hunter, who spied them while out walking one day. Orion became mad with desire and chased them relentlessly. Exhausted, the maidens prayed to Zeus for deliverance. Zeus felt sorry for them and transformed those seven maidens into the Pleiades. But the gods are, if anything, capricious. When Orion was killed by the sting of a scorpion, Zeus placed him the sky where he could resume his pursuit of the seven gorgeous sisters.

Our ancestors wove brilliantly imaginative stories, but they can bring us no closer to the stars than our dreams. It took yet another few thousand years until three scientists unlocked the true lives of stars.

In 1901, Harvard University was a man’s world, but astronomer Edward Pickering broke that rule. He assembled a team of women to map and classify the types of stars. One of them provided the key to our understanding of the substance of the stars. And another devised a way for us to calculate the size of the Universe. Outside of these talks, you’ve probably never heard of them. Wonder why.

The leader of the team was Annie Jump Cannon. Before she was through, she cataloged a quarter of a million stars. Cannon was also deaf; she lost her hearing during a bout of scarlet fever when she was a young woman. Another teammate was Henrietta Swan Leavitt who was also deaf. She discovered a law we’ve talked about that astronomers still use more than a century later to measure the distances to the stars and the size of the cosmos itself.

Annie Jump Cannon sent out a Christmas card in 1915 explaining what she and her teammates were doing:

“The light from the star is allowed to fall through a prism placed in the telescope and, thus magnified, is split up into a band showing its component colors, the red rays going to one end, and the violet to the other. This is the spectrum of the star. The photograph does not show the colors, but, what is more important, it does show the presence of fine dark lines, few in some spectra and numerous in others. These wonderful dark lines have become a veritable happy hunting ground for the modern astronomer. By comparing them with lines given by glowing substances in his own laboratory, he can also determine that the same elements familiar to us on the earth also exist in the outermost star.”
–Annie Jump Cannon, 1915

It took Cannon decades to classify the spectral character of hundreds of thousands of stars according to the scheme that she devised. Cannon discovered that the stars fell into a continuous sequence of seven broad categories according to their spectral line patterns, OBAFGKM. But the spectral lines of two stars in the same class could differ in subtle ways, minute variations that Cannon learned to recognize from memory. To distinguish these spectra from one another, she assigned ten numerical subcategories for each class, 0-9. Our Sun is a G2 star. Annie Jump Cannon organized the stars, but it would fall to another scientist to decipher the hidden meaning of her work.

In the England of 1923, women were forbidden from pursuing advanced degrees in science. But Cecilia Payne had attended a lecture in London by the astronomer Sir Arthur Eddington, the first scientist to provide evidence that Einstein’s Theory of General Relativity was correct. From that moment on, she knew that nothing would deter her from pursuing her big dreams. She resolved to emigrate to America where women had already gained the freedom to study the stars. Payne applied to and was accepted to Harvard. What she would discover there would challenge one of the central beliefs of astronomy and be the start of modern astrophysics.

As the decades passed, Annie Jump Cannon and her team kept sifting the stars, checking each one’s spectral signature with a fleeting glance and then dropping them into one of several categories. They became hundreds of thousands of dots in a larger picture which no one could understand.

Into this community of women came Cecilia Payne and she experienced kindness in a setting that is often unkind to women. The sisterhood generously shared the fruits of their labor with her, and she turned their observations into a radical new understanding of the stars. Cannon taught Payne everything she had learned about stellar spectra, and Payne began to analyze Cannon’s data to see if she could determine the actual chemical and physical state of the stars. She brought to this work her expertise in theoretical and atomic physics.

The most prominent features in the spectra of stars showed the presence of heavy elements such as calcium and iron, which are among the most abundant elements in the Earth. Astronomers naturally concluded that the stars were made of the same elements as the Earth and in roughly the same proportions. Among these astronomers was Henry Norris Russell who was also Payne’s thesis advisor.

When Payne was working on her thesis, she realized that Cannon’s classification scheme was actually telling her what temperature the star is. Furthermore, she discovered that stars are made almost entirely of hydrogen and helium. There’s a million times more hydrogen and helium than the metals in the stars. Payne said as much in her thesis which she handed in to Russell.

Russell felt sorry for Payne. Her thesis appeared to him to be fundamentally flawed. It is clearly impossible that hydrogen should be a million times more abundance than the metals. Her carefully gathered evidence flew in the face of conventional scientific wisdom. Despite her confidence in the quality of her research, she caved and added a sentence to her thesis that undermined its greatest insight:

“The outstanding discrepancies between the astrophysical and terrestrial abundances are displayed for hydrogen and helium. The enormous abundance derived for these elements in the stellar atmosphere is almost certainly not real.”
–Cecilia Payne, “Stellar Atmospheres,” 1925

It would be four years before Russell realized that Payne was right. To his credit, as soon as he did, he acknowledged that it was her discovery. Payne’s thesis is widely regarded as the most brilliant PhD thesis ever written in astronomy. It became the standard text in its field. Cecilia Payne’s interpretation of Annie Jump Cannon’s sequence of stellar spectra made it possible for us to read the life stories of the stars and to trace the story of life itself back to its beginnings in their fiery deaths.

Now, I tell you that story because I want to illustrate my view of the Universe, what I see when I look up into the night sky. There’s that semi-famous quote from Neil deGrasse Tyson, “I look up at the night sky, and I know that, yes, we are part of this Universe, we are in this Universe, but perhaps more important than both of those facts is that the Universe is in us. When I reflect on that fact, I look up—many people feel small, because they’re small and the Universe is big, but I feel big, because my atoms came from those stars.” That is a great thought to have and it certainly helps with settling some existential fears people might have.

However, I take a different approach, a more humanistic approach. When I look up at the night sky, I see the constellations, the planets, the stars, but I also see the many men and women who have worked to uncover the truths of those objects. I see Annie Jump Cannon at her desk at Harvard pouring over thousands of photographic plates to bring a sense of order to the countless stars. I see Cecilia Payne tirelessly working on a thesis she knows is right but one that flies in the face of conventional wisdom.

And I didn’t have to tell you their stories tonight. There are hundreds of other stories like theirs that I see. I see Ptolemy working in vain to make the planets orbit on perfect circles. I see Kepler figuring out for the first time that those orbits are actually ellipses. I see Shapley and Curtis arguing over the nature of spiral nebulae and Hubble coming along and telling us that not only is the Universe bigger than we believed, it is weirder than we believed. I see Vera Rubin discovering dark matter, I see Jocelyn Bell Burnell discovering pulsars. Einstein, Newton, Galileo, Halley, Chandrasekhar, Eddington, Herschel, Leavitt, and countless nameless others. “If I have seen further it is by standing on the shoulders of giants.”

I can see further because these people, each with their own stories, have longed to make sense of the Universe, to make sense of objects they can never touch, taste, smell, or hear but only look up at and dream. And in return, they have given us their knowledge, yes, but have also given us their dreams and stories. So when I look up at the night sky, I feel big because I see the countless thousands of people who have come before me and wondered the very same things than I wonder.

And although we have been concerned with the science these past several weeks, I hope that I have instilled in each of you that astronomy isn’t just a branch of science, it is also a way to tell the human story.

Tonight, I want to end by telling you one last story. The longest odyssey of all history was launched back in 1977, NASA’s Voyager 1 and 2 missions. They gave us our first close-up look at Jupiter’s Great Red Spot, and discovered the first active volcano on another world, on the moon Io, and an ocean beneath the icy surface of the moon Europa with at least twice as much water as we have here on Earth. The Voyagers dared to fly across Saturn’s rings and revealed that they were made of hundreds of thin bands of orbiting snowballs. Voyager 2 gave us our first portrait of the outermost planet, Neptune, where winds roar at 1000 miles per hour. Voyager successfully completed its mission of discovery to the outer planets, but its odyssey was just beginning as they breached the uncharted waters of interstellar space.

Twenty-six centuries ago, the Assyrian king Esarhaddon wrote

“I had monuments made of bronze and inscriptions of baked clay. I left them in the foundations for future times.”
–Esarhaddon, 7th century BCE

Carl Sagan similarly recognized that the Voyager mission offered two free tickets to something approaching eternity. He assembled a small team to create a message to any civilization that might, one day, encounter the derelict spacecraft.

And what did they come up with? A golden record with a projected shelf life of a billion years. Become an extraterrestrial archaeologist for a few moments. An artifact has been fished out of the interstellar ocean. It was made by beings that lived about a billion years ago. What would you make of them and their world? They’ve sent us their music and greetings in 59 human languages. And one whale language. And a sound essay that includes a Saturn V rocket launch, a mother’s first words to her newborn baby, and the sound of a pulsar.

In and amongst the usual suspects of Bach, Beethoven, and Mozart is an odd little tune, recorded in 1927 by a Texan preacher and street-corner blues singer, Blind Willie Johnson. Born in 1897, he knew from a young age that he wanted to be a preacher. He did not falter in his devotion to God and what he felt was his calling, despite being blinded when his stepmother threw lye in his face for his father’s infidelities.

Johnson made money playing music on the street and was eventually found by a field unit of Columbia Records. Between 1927 and 1930, Johnson recorded 30 titles for Columbia for which he was probably paid $25-$30 per song. Although he was successful for a time, when the Great Depression hit, Johnson found himself playing music on the street for money again. He did in 1945 at the age of 48 from pneumonia which he got from sleeping in the wet remains of his burned down home.

That song that Sagan and his team picked? A hymn, a wordless melody consisting only of Johnson’s slide guitar and his resonant, gospelly, moaning hum. Sagan picked it because “Johnson’s song concerns a situation he, and humanity, have faced many times: nightfall with no place to sleep.”

What can we say about the far off future the Voyager spacecraft will find themselves in? The only thing we can say is that something of who we were and the music that represents us, that we made in that long ago spring, will live on. And the human story will live on through the song of a blind man who could only dream of laying down at night and looking up at the stars.

Life on Venus?

Tue, 22 Sep 2020 00:00:00 +0000

This year, about the detection of phosphine in the cloud decks of Venus. Immediately, science news writers were screaming, “LIFE DETECTED ON VENUS!!!!” I promise you, that was not the case, but it is definitely interesting in and of itself and might point towards more observations required for us to definitively say that we’ve detected life on Venus. Let’s talk about that.

A Refresher on Venus

First, let’s bring everyone up to speed about Venus. Venus, named after the Roman goddess of beauty and nicknamed “Earth’s twin,” is the second planet from the Sun. It resides at an average distance of 0.72 AU (an AU, or astronomical unit, is the average distance between the Earth and the Sun, about 93,000,000 miles) and completes an orbit every ~225 days. It has the most circular orbit of all the planets.

However, that’s probably the most normal thing about it. Most planets orbit the Sun in a counterclockwise direction if you are looking at them from above the Earth’s North Pole. And Venus does that! Furthermore, most planets also rotate on their axis in the same counterclockwise direction. There are two major exceptions to that rule: Uranus, which is tilted more than 90 degrees on its side, so it looks like it tumbles around the Sun, and, you guessed it, Venus. Long ago during the formation of the Solar System, scientists think that Venus was smacked by a large body, causing Venus to flip over entirely. Since then, Venus has rotated clockwise, opposite to its orbit direction. What’s more is that it rotates so slow (~243 days) that its day is longer than its year!

The surface of Venus is also very weird. It is obscured by constant cloud cover, so the only information we have about the surface came from the few minutes artificial landers have survived and radar imaging from orbit. Most of Venus is covered in “deposition plains,” giant flat plains of lava rock. This is broken up here and there by a few craters. However, when you compare the number and age of the craters on Venus to other places in the Solar System, like the Moon or Mars, Venus has very few craters. It looks like the thick atmosphere burns up all the small meteorites before they reach the ground, but what about the large meteorites?

Scientists were confused about that too, but they came up with a theory. They hypothesize that Venus goes through periodic “global resurfacing events.” In this event, pressure from magma and trapped gases builds up underneath the surface. This happens on Earth too, but the Earth has cracks in its crust in the form of fault lines between tectonic plates for the pressure to escape through. But Venus has no tectonic activity, so no fault lines to let out that pressure. The pressure builds up, builds up, builds up until the surface can’t hold back anymore and the entire surface explodes, covering itself in lava. This erases the presence of any old craters, making the surface look young again.

As if that wasn’t enough, let’s look at the atmosphere now. The thick atmosphere of Venus is primarily carbon dioxide with some nitrogen and other trace gases. Those trace gases include fun compounds like hydrochloric acid, hydrofluoric acid, carbon monoxide, sulfuric acid, hydrogen sulfide, phosphorous acid, and phosphoric acid. Fun stuff!

Near the surface, the weight of all that atmosphere above it makes the surface pressure equivalent to 92 times that the Earth’s surface! To experience that on Earth, you’d have to be 5.5 miles deep in the ocean.

Adding to the crushing pressures is the excruciatingly hot temperatures. Thanks to all that carbon dioxide and sulfur dioxide in the atmosphere, Venus has a runaway greenhouse effect. This raises the temperature at the surface to a scorching 873°F! This makes it hotter than Mercury, the closest planet to the Sun. If you were on Venus and held a frozen pizza outside in your hand, it would cook in three minutes. Admittedly, it would also melt from the raining sulfuric acid, but it’d be cooked!

The Detection

And yet, among all that hell, there exists a part of its atmosphere that is just right. This Goldilocks zone is 30-37 miles above the surface at a balmy temperature of 140°F and a pressure of about 1 Earth atmosphere. A little too hot for humans, but there are plenty of microbes on Earth that can survive that sort of temperature and pressure.

A schematic of Venus' atmosphere. Note the temperate zone at an altitude of 48-60 km (30-37 miles), temperature of ~60°C (140°F), and pressure of ~1 bar (1 Earth atmosphere). Fig 1 of Bains et al. (2020)

This is where we join the story of the detection of phosphine on Venus. Jane S. Greaves (Cardiff University) and her collaborators had the goal of using Venus as a benchmark for other studies. They hadn’t set out to specifically detect phosphine, yet, when they looked at it through their telescopes, they found something!

They originally used the , a submillimeter telescope, to probe the atmosphere of Venus. When you hear the word “telescope” here, don’t think of a tube used by Galileo or Hubble or pirates. Think more along the lines of a giant radio dish. This Hawai’i-based telescope has been designed to see light in the infrared, specifically light with a wavelength between a few 100 micrometers to a millimeter.

When they analyzed the data they got from the JCMT, they found the signature of phosphine in their data! However, their signal was weak and they needed to confirm that it was actually phosphine and not some random noise or some other molecule pretending to be what its not.

They used their initial detection to get some time on the , a much better telescope for the job. Once again, this is not a telescope in the traditional sense, but actually 50 40ft radio dishes high up in the Atacama Desert in Chile.

When they peered through the 50 eyes of ALMA, they got an even stronger detection of phosphine! This was no coincidence! Furthermore, it was detected right in the temperate zone of Venus’ atmosphere, about 33-38 miles up!

Now, what is this phosphine? Phosphine is a molecule, a single phosphorus atom that has three hydrogen atoms attached to it. It is an odorless, colorless, and, like everything else on Venus, highly toxic gas. It easily burns with oxygen to produce phosphoric acid, highly corrosive in large quantities, but safe enough in small quantities to find it in your toothpaste and soaps.

We have found phosphine in three places in the Solar System: Jupiter, Saturn, and Earth. On Jupiter and Saturn, the chemical compositions, as well as the temperatures and pressures, are just right that phosphine is naturally produced in abundance. It is energetically favored to be produced. Meanwhile, on Earth, we know of only two things that produce phosphine: microbes and human industrial activity. For that reason, it has often been listed as a biosignature, a chemical that is a good indicator for the presence of life on other planets.

Ruling Out the Implausible

It was now up to the authors of this paper to show whether or not this phosphine could be produced naturally on Venus or required the presence of life to be produced. Abundance modelling showed that phosphine was present in 20 parts per billion (ppb) amounts. Now, what can produce that amount?

The authors of this paper were very thorough. They looked at every possible angle. Could energy of the Sun produce phosphine in the upper layers of the atmosphere? Nope, it would be destroyed too fast by that same solar energy. Maybe under certain conditions (temperatures, pressures, concentrations, etc.) phosphine could be spontaneously created? Turns out, its chemically unfavorable to do so; Venus would much rather form phosphoric acid and the like.

The researchers looked at even more absurd ideas. Was phosphine delivered to Venus by meteorites? Nope, Venus is accreting the right type of meteorite about 100 million times too slow. It requires energy to make phosphine, right? What if Venusian lightning delivered that energy! It would take a solid year of lightning, with no destruction, to create measurable abundances, and even then, its 10 million times too low. They looked at more things like giant meteor impacts (nope), Venus-quakes (how?), volcanic eruptions (not happening), and on and on.

Eventually, they came to the conclusion that either there is some sort of unknown chemistry happening on Venus or life is producing phosphine in measurable amounts.

I personally want to stress that this does not mean that the scientists who wrote these papers and did the observations are saying they found proof of life existing in the clouds of Venus. They are very adamant that more research needs to be done. There is still plenty of information we are missing about the Venusian environment; to plummet through the clouds and touch the surface of this alien world was in 1985. We also don’t know enough about phosphine and how it reacts biologically. More chemical research needs to be done as well.

But, what if there was?

All that being said, let’s play the imaginative game and pretend there’s life on Venus. How could it survive?

There are a few things we know it would have to do. First, it would have to survive in liquid droplets in the clouds; it could not survive just free-floating in the air. A free-floating cell would lose water until it matches the outside environment and on Venus, that environment is 10 times drier than the driest place on Earth. Bad news for a cell that needs water to survive!

These cells would also have to evolve some way of dealing with all the sulfuric acid in the clouds. Some researchers have seen how extremophiles here on Earth can survive in very acidic, high temperature, low water environments and said, “Yeah, that could happen on Venus too!” I cannot stress this enough that that assumption is incorrect.

The has acidic pools of water at 225°F, that is hypersaline, containing hydrothermal vents as well as the lowest pH ever recorded: -1.7. The pH scale normally only goes down to zero; its not meant to go down to negative numbers. Here on Earth, this highly acidic environment has sulfuric acid dissolved in water. On Venus, the clouds are water dissolved in sulfuric acid, making it 100 billion times more acidic than the most acidic place on Earth. Life would have to find a way to survive that.

The Venusian atmosphere is also extremely arid. The most arid place on Earth is Death Valley. On average, it has a humidity of about 2%. The Venusian atmosphere is equivalent to a humidity of ~0.07% at room temperature. This makes it extremely hard for cells to hold onto water.

Microbes exist in the Earth’s atmosphere too. But they don’t live up there. They can rely on the fact that at some point, they will fall back to the ground to gain nutrients and reproduce. The surface of Venus is uninhabitable, even by microbes. They have to spend their entire life cycles up in the air, making gaining nutrients very hard.

Gaining energy will be very hard too, but thankfully light is in abundance in the atmosphere. Most likely, Venusian life will have to be photosynthetic.

A proposed life cycle for Venusian life. (1) Dessicated spores persist in the lower atmosphere. (2) An updraft of spores transports them to the habitable layer. (3) Spores accumulate a liquid environment and become active. (4) Active microbes grow and reproduce. (5) Droplets rain out, while the microbes transform into spores again, resting in the lower atmosphere. Fig 1 of Seager et al. (2021)

All that said, there is still the possibility of life on Venus. If Venusian life exists as a microbe that is able to reproduce in the clouds, and survive the extreme environment, then life is likely. One such suggestion by researchers is that life will take the form of a bacteria-like species that reproduces in the clouds, and, upon dropping to lower layers, transforms into spores that can survive down there until an updraft of wind brings them back into the temperate zone. But that’s just a theory.

Only Time Will Tell

Does life exist on Venus? Right now, we’re uncertain. We’ve certainly found an interesting detection in this phosphine measurement, but we really won’t know until NASA or some other space agency (I’m looking at you, Russians) sends a new mission there. This is an exciting time to be studying the planets of our solar system, so be sure to keep an eye out for more news from our sister planet!

This is a recording of the "Public Astronomy Talks with Ray" that I led about the discussion of life on Venus and the results from this paper on September 20, 2020.

I was also interviewed by the Case Western Observer about this topic. If you’d like to read that article, click here.