hello space fans there are two announcements coming out of the double AES this evening that I'd like to share with you and both of them have to do with the manner in which astronomers measure how far away things are in the universe now before I go into the press releases of the announcements themselves i thought I would give you a little bit of background first because it might help some of you understand the press releases a little bit better kind of give you a frame of reference so when it's strong essential to the idea of measuring how far away things are in the universe is this idea something called a standard candle and a standard candle is based on the idea that when you have something bright that is very it will be that's close by and then you move it far away it will be dimmer with distance and sort of illustrate that I actually have a candle here so here I have a candle it's burning it's bright and it's very close to me this is its intrinsic brightness this is how bright the candle really is i'm not going to be able to make a better measurement of how bright this candle is then I am right now right at the candle itself but if I move it a certain distance away like that well now the candle is dimmer and I know by because of something called the inverse square law that light gets dimmer according to the invert the the is related to its distance from me I can then take those two measurements I can look at the brightness intrinsically and I can look at the observed brightness over there on the mantel and I can figure out how far away something is now of course the problem with this in astronomy is that we have a hard time getting the intrinsic brightness we don't know how bright something actually is we only know how bright it is in our telescopes so in order to make this measurement we have to get its intrinsic brightness the brightness is if we were right there at it and there are several techniques for doing that one of them has to do with this idea of C Fiat variables this is one of our standard candles that are used in astronomy and as the name implies this is a star that's brightness varies with time so if you took a whole bunch of measurements of this of a sea Fiat variable over time you'd start to see a pattern like this develop and if you measured between the two peaks of these of this pattern it turns out that is directly related to its intrinsic brightness so by measuring this peak you're actually measuring how bright it actually is as if you were standing right there on the star so we don't have to go there we all we have to do is measure that that pit those two peaks and we have this intrinsic brightness so with that information plus the the brightness that we see through the telescope and our knowledge of the inverse square law we can figure out how far away that star is now this was the technique that Edwin Hubble used in 1924 when he looked at something called the Andromeda nebula and here's a picture of it here he looked at all the seafood variables within this nebula and he measured those light curves he got those peaks and when he saw those peaks and he did the math he discovered that wait a minute there's no way those stars are in our galaxy there this nebula cannot possibly be inside the Milky Way it was millions of light-years away I think he measured it almost two million two million light-years away so he was the first to discover that the Andromeda nebula wasn't a nebula at all it was a galaxy and that the Milky Way was not the only galaxies in the universe this was the first time someone had realized that so that's one standard candle another one is known as a type 1a supernova and they are based on the concept let me pull up something here here we have a red giant star and orbiting around it a a white I'm sorry a red giant star and orbiting around it is a white dwarf now this white dwarf is very heavy and it's pulling matter off of this red giant star and it's going to get to a point where it pulls so much material off that it's going to explode on top of the star the star is just going to blow up now because we know the mass of a white star of a white dwarf and this is very important because we know the white dwarfs mass based on how bright the supernova gets we can figure out its intrinsic brightness and every single type 1a supernova has a graph that looks very similar to this where there's a bright peak it gets very rapidly brighten and it falls off with time if we can figure out that peak we can figure out how far away a type 1a supernova is we don't even really need to know the peak we can measure it here we can measure here we can measure down here and just fit it to this big shape and we'll eventually we could get the peak anyway and it is this technique that helps us get the brightness of very very faraway galaxies much further than what see field variables can give us because we can't always resolve individual stars and galaxies here's another cartoon of what one looks like red giant white dwarf explosion that kind of thing but here is an actual one that actually occurred this is known as supernova 1994 d it's a beautiful galaxy in the background and in the foreground is this very bright explosion these explosions can be seen for very very far away much further away than a sea field variable can be measured in brightness as changes in brightness so this technique is very powerful for things that are far away and this was used to measure the not only that the universe was expanding but that it was accelerating it was measurements from type 1a supernovae that we were able to get us a handle for the first time we real is that the universe was accelerating as it expanded so this is a very important technique both of these are so the first press release that came out comes to us from the Spitzer guys and they and it has to do with seafood variables and they said wait a minute if you're going to use C Fiat variables to measure how far away things are you better be careful because these guys discovered that the seafood variables are losing mass and that's important because it changes our luminosity and it changes their period so you have to make a justment for the fact that these things are losing mass as they burned and so some of the measurements using C Fiat variables are probably off by some factor and we need to go back and remeasure some things the second press release comes from comes from Harvard and this has to do with type 1a supernovae they've discovered a better way to measure them so as good as it is for measuring distances whenever you look at a whole bunch of type 1a supernovae you see a lot of scatter in the plots there's all kinds of a noise in there and so the error bars can are kind of large and so our distances aren't known to as well as we would like well these guys have discovered a better way to do it now we're more we get more accurate measurements of type 1a supernovae so now we can do a better to a better degree of certainty how far away very very distant stars galaxies are and get also a better handle on the acceleration of the universe as well as sort of constraining this idea of dark energy which is believed to be associated with the expansion and acceleration of the universe ooh I can't believe I did that all in one take okay space fans well that's it for now thanks for watching and keep looking up