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I am a planetary astrophysicist.

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(Cheers) (Applause)

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Thank you.

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But I will be the first to tell you[br]that I made that title up.

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(Laughter)

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You see, I had to make up a title[br]to describe what it is that I do.

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So I got my PhD in astrophysics

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because I look at the properties of stars[br]that are near to the Sun.

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But I also look at planets and how[br]those planets and stars interact.

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You see, up until about 25 years ago,[br]the term "planetary scientist"

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meant only people who studied the planets[br]within our own solar system.

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But it was in 1992 that the first planet[br]outside of our solar system,

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or exoplanet, was discovered.

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So, there's no name for somebody[br]who studies what I study,

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and today there are[br]3,593 known exoplanets.

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(Whoo!)

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It's a lot.

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So this field that I'm in,[br]it is very young.

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If it was a person, it would[br]barely be old enough to drink.

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(Laughter)

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Whereas astronomy in general,[br]which is the study of celestial bodies,

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has been around for thousands of years.

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It is the oldest of the natural sciences.

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So today we're only just learning

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about all the crazy possible planets[br]that can exist out there.

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There are some planets[br]that actually share a star,

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so they have two stars over the same one.

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And there are some,[br]like what you see on this picture,

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that are so close to their planet[br]that they have a period of ten hours.

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The Earth's period is 365 days.

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So that's pretty nuts.

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So we're only just now[br]really beginning to understand

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all the weird physical[br]and geometric properties

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that exist between a star and a planet.

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But I don't look at just how[br]a star and a planet move

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with respect to one another.

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I study how they chemically interact.

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But let me explain.

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From the Big Bang, the only elements[br]that we got were hydrogen and helium.

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So there is none of these[br]carbon or oxygen or iron.

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There's none of that.

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So what happened[br]was that the Big Bang went off,

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and there was hydrogen and helium[br]shot all over the universe.

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But it did so in an uneven way

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until it formed[br]these giant pockets of gas,

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which is sort of what you're[br]seeing in this video.

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Eventually this gas collapsed[br]in on itself and formed stars.

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But these stars were massive,[br]they were just absolutely huge.

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They were about a thousand times[br]bigger than the Sun.

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(Laughter)

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So this is like saying our Sun is a grape,[br]and these massive stars were as a cat.

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(Laughter)

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Except less furry.

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But it was within these first stars[br]that you were able to have

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high enough temperatures[br]and densities that you had fusion.

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So for the first time, elements were[br]slamming together, and they were sticking.

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So you have hydrogen,[br]which has one proton,

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and helium, which has two protons,

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and they slam together,[br]and suddenly you have lithium,

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and then beryllium, and then carbon.

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But these first stars,[br]they lived hard and died young,

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so they exploded out everywhere.

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But they took all of these new elements[br]that they created inside of them,

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and they shot them out,[br]also into the universe.

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So a second generation of stars was formed[br]mostly out of hydrogen and helium,

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but also with these seeds of carbon

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that they could continue[br]the process of fusion.

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Our Periodic Table[br]was compiled by looking at stars

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who lived and died at different times.

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This one here is color-coded and was done[br]by a colleague of mine, Jennifer Johnson,

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and what she did was she color-coded it

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to show the different ways[br]in which these elements could be formed.

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So you see that a few of them are blue[br]because they came from the Big Bang,

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but most of them come

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from either two stars circling[br]each other and then exploding,

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or just one exploding as a supernova.

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So, our Sun is created out of the original[br]hydrogen and helium from the Big Bang,

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but also out of many of these elements.

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And at the same time that the Sun[br]was formed, were also planets.

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So that's everything[br]from Mercury to Neptune,

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even the dwarf Pluto.

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But it was on the Earth[br]that life blossomed,

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and out of that life came humanity.

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But our humanity is really rooted[br]in the properties of our planet.

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So when you think about it,[br]people are made up of raw ingredients,

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these elements that are so basic to life,[br]which were created in stars.

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We are carbon-based beings,[br]the bones made of calcium.

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And we walk on iron silicates[br]on the ground,

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and we breathe oxygen,

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like right now, you're breathing,

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I could see it.

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(Laughter)

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That came from a star.

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So we're all stardust.

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Quite literally.

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But we can also do a thing[br]that is similar to other stars,

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in that we can create other elements.

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[Tennessine]

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(Applause) (Cheers)

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For example, tennessine,[br]which you may or may not have heard of.

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So this is Ts 117, and it was named[br]after the great state of Tennessee

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because a number of Vanderbilt scientists[br]were part of the discovery team.

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I'm often asked the question:

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"How can you look into outer space

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when there are so many[br]problems here on Earth?

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Doesn't it make you feel small?"

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And my answer to that[br]question is always no.

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It doesn't make me feel small,[br]it makes me feel empowered.

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Because I know all of the things,[br]all of the events

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that might have happened,

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and all of the events that did happen[br]in order to create life.

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You see, it's important for us as people[br]to know where we came from,

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whether it's our parents, our ancestors,[br]our planet, the birth star,

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or the stellar nursery.

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Knowing our root is a fundamental drive[br]that is so important to humanity.

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And it's by using the scientific method

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that we're able to come up[br]with a hypothesis

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that can explain how the solar system[br]got to be where it is today.

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So for example, it's currently thought[br]that a supernova must have gone off

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4.6 billion years ago[br]as the solar system was forming.

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We're then able to collect data[br]about nearby stars and planets

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such that we can understand[br]their basic properties.

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So now we've found that there[br]are specific elements in meteorites,

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and also at the bottom of the ocean,

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that could have only come[br]from a supernova.

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There, and with the help[br]of our peers reviewing our data,

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we're able to deduce the fact

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that this supernova[br]must have acted like a huge blender.

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So it took the gas, and the dust,[br]and all of these new elements,

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and it swirled it together[br]until it made something

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that was palatable[br]or habitable for life.

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It's by looking at thousands of planets

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and millions of stars

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that we're able to see what a unique[br]cocktail of basic elements was needed

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in order to create a planet[br]that could sustain life.

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Then there were even more unique[br]circumstances that were needed

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to create that life.

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In other words, we are[br]a mathematical anomaly,

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a rarity in the universe.

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And while there's probably[br]life in the universe,

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maybe even our Milky Way galaxy,

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that life is going to be inherently[br]different from our own

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because they were affected by events[br]that never happened for us.

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And it's going to take quite a lot[br]to actually detect that life

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because we need to be able to find,[br]fund and develop the new technologies.

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So thinking about the statistical[br]likelihood of our existence,

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it doesn't make me feel small,

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it reminds me of all the possibilities[br]that exist in outer space.

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When we were undergrads, we'd walk[br]at night from the library to the dorm,

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and we'd look up at stars.

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And I'd look up at Orion in particular.

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In our classes, we learned that two stars[br]that are shooting through space,

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they're probably never going to collide,[br]no matter the circumstances.

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And that the inside of a star[br]has a structure like an onion,

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it's like shells.

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So over time, I realize[br]that these constellations

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changed from being just these dots[br]in the sky to being distinct characters.

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I could see them, being[br]at different distances from us,

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and they shone in different colors,

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and they were rotating[br]at different speeds.

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Some of them had planets[br]that were so close to them

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that it was hard to fathom.

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And others shared their planet[br]with another star.

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When you look up in the sky,

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it's like zooming from the Earth[br]into outer space.

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Except, instead of seeing[br]data or pictures,

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you're seeing questions and possibilities.

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Regularly looking outside of our world

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gives you a perspective[br]that's so easy to forget.

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There were so many events[br]that had to happen

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in exactly the right sequence[br]in order for me to be with you today.

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If even one of those things was different,[br]say that the Earth was closer to the Sun,

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or that the Moon didn't exist,[br]then maybe life wouldn't have happened.

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Realizing the statistical odds[br]of our existence,

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it helps to have[br]all of the day-to-day drama,

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anxieties, and insecurities[br]just fall away.

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It reminds you who you are.

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A mathematical anomaly [br]in a sea of gas, stars and planets.

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And what I do is I study those stars[br]and planets in order to try to understand

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how they formed and how they evolved.

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And maybe, just maybe, to discover life.

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But you don't have to be[br]a planetary astrophysicist

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in order to feel inspired[br]or empowered by outer space.

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All you need to do is look up and remember[br]that there are so many things going on

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outside of the right here[br]and the right now.

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There's stars being born,

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planets colliding,

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galaxies rotating,

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all of which are beautiful[br]as you can see.

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And they have nothing to do with you.

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(Laughter)

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Or so you think.

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But these were the exact events[br]that had to happen

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in order for the Milky Way[br]galaxy to be formed,

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for a supernova to go off,

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for the Earth to rotate around the Sun,

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and for us to exist.

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Thank you.

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(Applause) (Cheers)