Dr. Brian Keating
speaker
1,291 appearances
4 recordings
4 series
first heard Dec 2024
last heard Sep 2025
Dr. Brian Keating’s voice in public audio — every appearance, attributed to the second.
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You build it to use it. And it's about 10% of the construction cost to operate an instrument, a battleship, a telescope, whatever. It's a rule of thumb that project managers love to use. So that means in 10 years, it's going to double the price. And we hope that Hubble and Webb, and Hubble's already lasted 40 years on it. So it lasts a long time.
So whenever you hear this, but it's incredibly expensive. One kilogram used to cost like $10,000 to bring to orbit. And Elon keeps talking about how cheap it's going to be, but he has yet to launch a scientific instrument. I talked to him for 10 minutes on my podcast once, and I tried to get him to shut off these. Starlinks are amazing.
I have one in my house, but they have the property that they go through astronomical images and they leave a satellite trail behind them, which is ridiculous. It can be – you're taking a picture of a deep star, a deep galaxy or whatever and you see these streaks going through it. It ruins the image and you have to wait until they're gone.
But at least in optical astronomy, you can physically literally paint those satellites black and they will no longer reflect and so they won't obscure the image whatsoever.
They definitely are because while you can paint an optical satellite black and make it black, we're looking for heat. There's no way to stealth, you know, confuse or block out heat. Sorry, that's the law of thermodynamics. Anything that's above absolute zero will always give off heat.
And worst of all, the signals that he uses are in the exact microwave spectral range that we use to look at the CMB, the cosmic microwave background.
No, he said he would look into it, you know, nine months ago. Elon, I know you like the show, so please do reach out to me. But this would be just turning it off when it's over our telescope, basically. And the South Pole. So it's not a big deal.
There's no one at the South Pole. It's not like he's getting millions of dollars in ad revenue from people at the South Pole. They don't use them. So anyway, I'm asking Elon. It's a small ask. But anyway, so we want to be above the atmosphere, but it's millions and maybe billions of dollars to do that for a telescope like we're using or for an optical telescope here. on Earth.
So scientists became very convinced that there has to be a way to mitigate the effects of the atmosphere. Now, what is the main effect of the atmosphere? Well, you learned it when you were a kid. Twinkle, twinkle, little star, how I wonder what you are. What is that twinkling? It's called scintillation. Scintillation is the property of a point source
which is a star is so far away, even though they're enormous, they still only subtend a zero-dimensional, almost zero-dimensional dot of light on the sky. When it goes through the atmosphere, the atmosphere has macroscopic turbulence features. The atmosphere is a fluid. There's turbulence, there's roiling columns, there's cells of the atmosphere.
And if you've ever looked at a star, they jitter, looks like they're moving around. And that's the combination of the atmospheric cells. Each column of air that has slightly more density will refract light slightly different angles. Remember we talked about light when it goes through a lens, it refracts, it bends.
It's coming through, it's getting deflected slightly, and it's moving and it's landing on different retinal cells. and we're perceiving that as this motion or in a CCD array, it's also landing on different pixels. So you can't get away from it by using technology. It's still an effect. It's caused by these atmospheric turbulent cells.
And by the way, you can tell and you can identify a planet by the fact it does not It does not twinkle, twinkle. So Jupiter is visible tonight. I hope you'll see it with the telescope. We can see it after we're done recording. We keep going. We're about halfway done, I figure. We'll go outside. We'll look at it. And you'll see it's not stationary.
And I actually used that on the night I kissed my wife for the first time. But I'm not going to talk about that. When you look at the planet, you can identify them by their lack of scintillation. So it's a way to identify if it's a plane, a star, or a planet.
So astronomers, including a colleague of mine in UC system, Claire Max, and other people realized in the 1960s and 70s that if they had a fake star, It's actually called either a guide star or an artificial star. I'll explain how they make that in a minute.
Then if they knew the exact properties of that guide star, then they could measure just the guide star through the same optics of the telescope. And then they would take the light from that artificial star onto a flexible deformable mirror. So the mirror could actually wobble and wiggle And it would do so in an exactly compensatory way to nullify the atmospheric turbulence.
So it's basically what light does when it goes through a cell of the atmosphere. It traverses a slightly longer path difference. So they would shorten the path difference of the mirror. They make it a little bit closer in the direction of that cell and other places they'd make it farther away and vice versa. They compensate for it. And this was done by a combination of two technologies.
One was the deformable mirror that could flex 100 times per second. And the other was making these artificial stars. So how do they make an artificial star? They shoot a laser into the troposphere. That laser illuminates sodium.
Troposphere is a layer of the atmosphere. I used to know all the different layers. That's OK. OK, ionosphere is the farthest away.
Yeah, it's 40, 30, 40 kilometers above the Earth. It's not quite in space. Far enough away that the laser beam is still collimated. It makes a nice beam. And it can illuminate and then cause this sodium ions to Flores basically. So they start to get really stimulated. It looks just like a star. They know exactly how they produced it.
Showing 1041–1060 of 1,291 · page 53 of 65
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