2026 March 10 - Sky Glows over Paranal Observatory

0:00Greetings and welcome to the Astronomy Picture of the Day podcast. Today's picture is titled Sky Glows Over Paranal Observatory. So what do we see here? Well, here we see looking out over the Paranal Observatory down in Chile. And we see the telescopes domes there, as well as lasers shooting out into the sky. Well, this isn't some kind of new defense system. It's actually a way of being able to improve astronomical observations. So what can be done is when you're looking through the telescope at a sky and something is being imaged. If there's a bright star in the region, you can use that to learn about the atmospheric effects and how that is affecting the telescope observations. But in some directions, you don't have bright stars there that can be used for this. So what do we do? We create an artificial star.

1:00And that's what's being done here with the laser, shooting the layers out into Earth's atmosphere, upper levels of Earth's atmosphere. Then allows the flexible mirrors to be adjusted. This is what is called adaptive optics. And we can then deform the mirrors, so instead of using a nice smooth mirror, which we usually want, we deform the shape of the mirror to take into account the observations made. And that is the effect, essentially, the atmosphere that we see. So the atmosphere disrupts the light coming from distant objects. And if we can adjust it by making an artificial star like this, then we can make that adjustment to the mirror. And when we're actually observing our other objects, we can then calculate the deformation and redo the images and get a much more high resolution images. And this is a way to get close to matching the resolutions that we get from space. Space telescopes do not have to look through the atmosphere.

2:01So the images tend to be much clearer and sharper, defined only by the limiting size of the telescope itself. However, telescopes on Earth have a limiting resolution defined by Earth's atmosphere. So being able to take out some, or at least minimize those effects, gives us much better resolution from even larger telescopes here on Earth. Now, it's not the only thing that we see here. We can also look past the telescopes up in the sky. And we can see various colors glowing off in the distance. We can see the arc of our own Milky Way galaxy stretching across the sky. And we can also see off to the left hand side, we can see the green air glow that occurs. And the two Magellanic clouds. And on the right we see red air glow. Now, air glow is caused by photons of light from the sun that then excite gases in the atmosphere.

3:03It's very similar to what we get with the aurora. However, in this case, instead of being caused by particles, it's being caused by actual photons of light. It's being caused by the light itself, giving us this glow that we see. So that was our picture of the day, titled Sky Glows Over Paranal Observatory. We'll be back again tomorrow for the next picture. So until then, have a great day everyone. And I will see you in class.