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I am Brandon I'm going to be the session

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chair for TA molecules he'll might need

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how might we blow them up and so your

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molecule was blown up how to put cap the

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pieces and put Humpty Dumpty back

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together again so these are the two

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sides of astrochemistry we blow stuff up

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and then we put it back together and

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I'll give you a little introduction into

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how we do all that so first this is our

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lab so we start astrochemistry starts

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when a star explodes this is a hard

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reset to the chemistry you kind of blow

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everything up you atomized it and you

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start from scratch eventually things

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condense back into a cloud of gas and

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dust these are usually sort of a few to

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hundreds of light-years across very big

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eventually we heard a lot about this

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yesterday but they start condensing down

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into smaller and smaller cores for the

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high mass star forming regions you get

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many of these like hundreds of these in

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a single cloud will condense down into

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protostars with disks around them then

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they condense even further they form

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little planets and planetesimals the big

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ones govern but the little ones they

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create all of the matter that was left

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over and if you're lucky for some places

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you get life and for an astrobiology

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conference this is what we're really

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interested in is which ones of these

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systems actually end up with life and

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what can astrochemistry add to that

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picture

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and so astrochemistry isn't really about

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any one of these places it's not about

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you know supernovae or gas clouds it's

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about the process that happens through

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this because once you blow this up you

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have to start from scratch building

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bigger and more complex molecules all

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the way through and that's what we study

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is how you get from there to about here

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once we get to here Astro chemistry's

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out this is planetary science or

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biology's problem and yeah and so for

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the most part today we're going to hear

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talks at focus sort of on this area

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mostly because these are the most easily

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observable eye places where chemistry

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happens in the universe and so one of

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the really cool things I think

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for astrochemistry and what it can tell

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you about astrobiology is this if you

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look at things like the Murchison

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meteorite or comets you see this really

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awesome mix of stuff

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things like long-chain fatty acids

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purines pyrimidines amino acids even

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some light sugars that are all just you

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just grind this up and extract it and

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it's there and this is a meteorite that

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fell to earth and you know successfully

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delivered this without destroying all of

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it and this is kind of a small-scale

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example we know comets can do this too

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and we know we kind of heard a little

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bit about this yesterday that the earth

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accreted a pretty sizable amount of

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water and other organics as it was

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forming through stuff like this the

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really cool thing is this is a pristine

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record of the solar system at its

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earliest point this is chemistry that

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this is molecules that were around

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before the earth even formed and so the

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question is from an astro chemical

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perspective how did you make that how do

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you get that there how typical is it

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what are the inventories you think

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you're going to be working with on a

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planet that's forming and you know what

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can that do for forming life and how

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does that happen it's not aliens it's

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chemistry it's the same chemistry you

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learned about in Gen chem class it's

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just applied to a really weird system so

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to start with this is our periodic table

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so this everything is scaled by size to

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the abundance of a molecule in space so

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hydrogen is far and away the most

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abundant thing you have to work with

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next is helium and oxygen carbon

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nitrogen all the interesting stuff is

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like 1% by number so almost everything

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you're dealing with is hydrogen helium

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and for stuff we'll hear about later the

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dust and ice that is you know one of the

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big powerhouses of making more complex

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molecules is only about a percent of the

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total mass for the beaker

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these are usually massive star forming

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regions once the clouds of gas and dust

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condense that that's where you can

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actually start to form molecules these

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have masses of you know tens of

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thousands to millions of solar masses

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these are huge associations once you get

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down to the protoplanetary disks they're

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pretty tiny but for the

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Eggar clouds there hundreds of

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light-years across these are enormous

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things the densities can start off at

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100 molecules per cubic centimeter and

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they get higher and higher for reference

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the air you're breathing is like 10 to

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the 19 molecules per cubic centimeter so

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in space especially in the diffuser is

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molecules can go months between

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colliding with other molecules they are

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very lonely they just ping around and

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eventually bump into something the

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temperatures can get up to a thousand

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Kelvin for most places it will start

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down at 10 Kelvin as things condense and

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eventually warm up to 300 which is

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toasty warm for the interstellar medium

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and the chemistry looks kind of weird I

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mean everybody's taking gen chem so if

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you had some equilibrium with these

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molecules you'd expect it to end up on

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the right here but you have to get

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through some intermediate and in space

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that's not always so easy so you you

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can't describe things by simple

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Boltzmann statistics there's barriers in

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the way and so the good news is the

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history matters so the state of your

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system when you see it get a cloud of

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gas and dust it depends on the detailed

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history of what happened before it so

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you can sort of measure you can actually

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use this to tell you something about

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what happened the bad news is is that

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history matters because the details of

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you know what's the difference in energy

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what's the barrier what are the rates

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for all of these things are incredibly

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important and if you want to figure out

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what the hell's going on you have to

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know all of the details that went into

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making this to figure it out and that's

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millions and millions of parameters

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you'd have to know so it turns out to be

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really tough and that's a lot of what

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we're going to hear about today is

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actually figuring out the details of

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this so we can actually understand

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something about the chemistry that we

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see happening in space because it aronia

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cleef or something for a field where you

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study things that are absolutely

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enormous most of the most of the stuff

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that comes down to the details knowing

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these tiny atomistic details so the two

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flavors of chemistry we really work on

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studying our gas phase chemistry so in

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these big clouds of gas and dust you get

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weird chemistry it's driven by ions like

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h 3 plus and CH 3 plus and you just

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chain things

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together in simple bump-bump-bump

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reactions but if you want to understand

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this you actually need to know something

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about all of the rates for everything on

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this page and this is one of the simpler

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reaction schemes you can think of the

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other one will hear a lot about is grain

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surface chemistry or ice chemistry so

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once things cool down everything

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condenses out into these fluffy grains

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of usually silicon and carbon and so

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cools off things accrete another

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molecule creates or atom treats and you

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may roam around and get together and

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react this actually turns out to be how

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you make most of the more complex

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molecules in the universe

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this concentrates everything down so if

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you're going a month between colliding

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with things it takes a long time to

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build up anything more complex than say

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methanol but if you you put everything

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down on a tiny little grain of gas and

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dust and let them roam around together

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it concentrates them it catalyzes

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reactions and you can build much bigger

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and more complex things so we'll hear a

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lot about both of these today

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to give you an idea of sort of the state

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of the field this is I think as of a few

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months ago pretty accurate this is every

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molecule we've ever found in space

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there's only about 200 of them if you'll

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notice it's really heavily weighted to

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you know really light stuff it turns out

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that seeing molecules you know twenty

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and thirty light years away or further

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is really difficult and so the bigger

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they are the harder they are to detect

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not just to make but to detect and and

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so what you see is yeah diatomics are

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pretty easy try tommix but as you get up

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to and this is what we would call

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complex anything over six atoms it gets

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very difficult and the the numbers start

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dropping off quick and so anybody that's

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reading really quickly will notice

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glycines not on here a lie seems like

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there are no sugars on here there are no

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amino acids on here the really basic

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interesting stuff you would like us to

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be able to tell you about we still can't

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find which is a little tough but it

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means that we have to lean more heavily

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on things that we can do like simulate

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the chemistry that makes everything here

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and use that too and for

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abundances we can't see but this is kind

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of state-of-the-art so just to give you

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sort of a brief overview of what

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astrochemistry ends up doing i so

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laboratory astrophysics astro chemical

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modeling and observational astronomy are

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the three sort of pillars of

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astrochemistry i will here talks mostly

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today in these two sections so

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laboratory astrophysics that's where you

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you measure spectra that lets you

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interpret your results it gives you all

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the parameters or hopefully a lot of the

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parameters for your chemical models

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kinetics thermodynamics cross-sections

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things like that astro chemical modeling

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is generally how you would interpret a

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lot of the results you model the

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observations you see you model them

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forward in time to figure out what's

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going on you can use them to think about

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what are the likely abundances of things

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you can't detect so far and then

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observational astronomy is sort of the

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stupid check on all of this what's

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actually there how much of it's there

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and where is it so a lot of the front of

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progress has been made in the last

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couple years with things like Alma we've

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heard about and so a lot of what we're

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going to be hearing about today is

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trying to figure out interpret a lot of

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the observational results that already

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exist today and so yeah this is pretty

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much how we do astrochemistry alright so

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that's that's it that's all i've got i

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just want to hurry up and get out of the

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[Applause]

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questions about astrochemistry uh why

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bigger molecules are harder to detect

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two things one so I mean even on a grain

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surface it takes a while for stuff to

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find each other and in the gas phase

274
00:10:54,679 --> 00:10:52,170
collisions are slow

275
00:10:56,720 --> 00:10:54,689
so basically statistically it just takes

276
00:10:58,340 --> 00:10:56,730
a while to build stuff up also if it

277
00:11:00,259 --> 00:10:58,350
takes a while to build stuff up it's

278
00:11:01,369 --> 00:11:00,269
much easier to tear it down so a lot of

279
00:11:06,350 --> 00:11:01,379
well we'll hear about today's photo

280
00:11:07,730 --> 00:11:06,360
destruction and bigger stuff just if it

281
00:11:09,920 --> 00:11:07,740
takes a while to build it up it gets

282
00:11:12,290 --> 00:11:09,930
blasted apart faster or not faster but

283
00:11:14,139 --> 00:11:12,300
it gets blasted apart fast compared to

284
00:11:17,360 --> 00:11:14,149
how long it takes to make it also

285
00:11:18,679 --> 00:11:17,370
heavier stuff is just the signal gets

286
00:11:22,189 --> 00:11:18,689
weaker because instead of just having

287
00:11:24,619 --> 00:11:22,199
like two states that are occupied for a

288
00:11:26,240 --> 00:11:24,629
rotational transition you get like two

289
00:11:28,309 --> 00:11:26,250
thousand states that are occupied and

290
00:11:30,079 --> 00:11:28,319
you have you know less molecules spread

291
00:11:34,730 --> 00:11:30,089
over more states it's tough to detect a

292
00:11:35,900 --> 00:11:34,740
single one so yeah big is bad but big is

293
00:11:41,259 --> 00:11:35,910
good because that's where all the

294
00:11:46,490 --> 00:11:41,269
complex stuff is any more questions