Title: Lights in the Night Sky

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Brian Lehrer: Brian Lehrer on WNYC. To end the show today, we'll turn to the sky. Over the weekend, a rare aurora borealis made an appearance over New York City. Did you see it? The splashes of pink and yellow and green were actually the result of a powerful solar storm that slammed into earth. Joining us now to discuss how auroras happen and to preview some other celestial events to look forward to this season is Jackie Faherty, astrophysicist and science educator at the American Museum of Natural History. Jackie, thanks for joining us. Welcome to WNYC.

Jackie Faherty: I am so thrilled to be here, Brian.

Brian Lehrer: Listeners, we can take some of your calls. Calling all aurora chasers and novice star gazers. What did you experience over the weekend if you saw it? 212433. WNYC 212-433-9692, whether it's your first aurora or you travel the world to go see them, what did you see? 212433, WNYC-433 9692. You can also ask a question of our guests about celestial viewings. 212-433-9692, call or text. What's an aurora, Jackie?

Jackie Faherty: Oh, what is an Aurora? That word, it's such a beautiful word. People name their children that word. It's such a nice one. It means that you get a celestial light show. For us, it really means that the sun has sent over some charged particles, some protons, electrons, our way, and they get caught up in our magnetic field, and then they interact with our atmosphere. When we say the aurora, we're really talking about the part that you see with your eye, which is the colorful light show, but it's actually a process as well that we're getting where the earth's atmosphere is interacting with a solar storm.

Brian Lehrer: What does the word borealis mean? Why do we say, "This is the aurora borealis"?

Jackie Faherty: Oh, I'm not sure how borealis got attached to it. There are a lot of constellations in the sky that also have borealis in them, and so I'm sure it has Latin origin somewhere.

Brian Lehrer: We also call the aurora borealis the northern lights, and they're often visible in places much further north, like Canada or Norway or Iceland. My one aurora borealis experience was lying on my back on the grass up in the Adirondacks one year in the summer, and seeing this light show that was better than anything I ever saw in a concert hall. News reports say tens of millions in the United States saw this. How unusual is it to see them this far south? We can call New York City south.

Jackie Faherty: Yes. This was a really good one. It's so hard to predict when these things are going to happen, but they definitely happen more than not, because the-- borealis means north by the way, I just got a text from a colleague to make sure that I knew that.

Brian Lehrer: Northern lights, there you go.

Jackie Faherty: I would say that the sun goes through these periods of active and inactive times. The active periods, it happens about 11 years and we're close to a solar maximum in activity right now, which is why we're getting a higher chance of having a storm, but you need a good storm. When we get these auroral storms or these solar storms, the sun is ejecting billions of tons of material our direction, and you got to be in the right spot. Sometimes the sun has this active moment and it's not facing us, and so you're not going get anything from that, or at least you'll get a very minor amount depending on where you were.

In this case, the earth was in a good position. It was a really strong storm. It comes at us, it interacts with our magnetic field, but if it's strong enough, it can cascade farther and farther south. That's why New York got washed over by the material because it was a strong enough storm this time around. It can happen at any time. It's far more likely when the sun's in the active period, and that's where we're at right now.

Brian Lehrer: Let's take a call. Martin in the Bronx, you're on WNYC. Hi, Martin.

Martin: Hi. I'm an everyday listener.

Brian Lehrer: Thank you.

Martin: Last week I was 50 miles north of the city in, like Monroe area, Central Valley. So far, nobody has mentioned that you can't really see it with the naked eye. Unless I don't get it. I was with a friend, we were out at night. We couldn't see anything with the naked eye, but we start clicking away with our cell phones. After we took the shots, we went indoors, and in the sky, we see these beautiful hues of pink and green, like a beautiful sunset. We couldn't believe it that we couldn't see it, but our cameras picked it up. Anyway, do you have to have a cam? I don't know. Are people seeing it with their naked eye?

Jackie Faherty: Yes. I can answer that one for you because I am with you. There was a lot of people that posted tremendously gorgeous pictures across New York City, New Jersey, our Metro area. I can always tell when we got a nice long exposure, and that's not necessarily what the eye saw. This was a naked eye aurora. You could see this one with your eye. It wasn't blastingly gorgeous the way that you'll see that if you traveled to the northern Lights highway, if you go to Tromso, Norway, or parts of Sweden, the north where it really gets the heart of the auroral interaction, that shows you ribbons of light cascading and it moves around like a wave, and the colors are gorgeous.

That kind of thing, we didn't have on Thursday when we got hit by the storm here in New York, but it was enough that I wouldn't-- I think we should all be excited that we got to see it with our naked eye. That's what I'll say. It was definitely naked eye.

Brian Lehrer: Martin, thank you. Call us again. Is there a reason-- by the way, on the terminology here, I think the term "Blastingly gorgeous" should definitely take its place as a scientific term. Is there a reason that our cell phone cameras would pick up more of the colors than our naked eye in some cases?

Jackie Faherty: It's the same thing as long exposure photography. You're leaving the aperture open on your-- Your camera phone's got a pretty nice detector on it, and it's taking a longer exposure than what your eye can do. Those colors are visible to your eye, but they're just too faint. It's not that it's bringing up the colors, it's just letting in more light. You need something to have your eye open for a longer period of time.

I'm an astronomer. I go to telescopes all the time. The reason why we go to telescopes is because we use them to reach a depth that our eye can't manage. I do long exposures at telescopes so I can see things that are way, way farther away than anything the eye could detect. Your camera phone is doing that for you in our atmosphere at the times that people are noticing these gorgeous pictures of the aurora.

Brian Lehrer: Listener writes, "We live in northern New Jersey, Bergen county, and our town is one of a few that borders New York state, the Piermont/Nyack area. We stepped outside to say goodbye to my sister and witnessed the most magical colors right outside our door, we had fuchsia pinks. A block away, my sister's home had purples. Such an amazing sight for our young son, who we've been wanting to take up to Canada to possibly see the northern lights. That's really great."

Jackie Faherty: One thing I would say on this too, the colors that people are noting, they mean something. The greens or the purples, it's just the same as when fireworks go off, like the Macy's Fireworks Show that we get here in New York. The different colors are different chemicals that are being used by the pyro geniuses that put that stuff together. What's happening in the aurora is that you're seeing either a different element like oxygen or nitrogen, that are getting excited by the interaction with the charged particles from the sun, and that'll be the different colors.

Oxygen will look very green, and it depends on where you're getting the oxygen and what part of the atmosphere that you'll see it at a different color. Just remember, when you see the colors, they also mean something very specific scientific, and you can learn more about chemistry in the earth's atmosphere by looking at an aurora.

Brian Lehrer: Sydney in Scarsdale, you're on WNYC. Hello.

Sydney: Hi. I just wanted to ask about the comet, the comet that's passing, if that's related to any of this.

Brian Lehrer: Thank you. Not one, but two comets, Jackie, right? Currently projected to be visible in the night sky soon?

Jackie Faherty: Well, the one we have right now, I'll tell you, is good. I want to encourage everybody that listens to the Brian Lehrer Show to please go outside and look for it because it's there and it's naked eye in New York City. I was watching it on Saturday night, and then I looked for it yesterday. It was a little bit cloudy on the horizon, so you couldn't see it. It is a comet. A naked-eye comet, Brian, is not something that happens very many times in your lifetime. I take that as a sparing statement. There's a lot of people that use the-- It's rare in astronomy, a lot for things, and a lot of things happen many times over your lifetime, and so no.

Naked-eye comets are hard to predict. They are not necessarily going to happen that many times over your lifetime, so go outside and look at this one. You have to go right at sunset so the sun will set. You can find Venus. Venus is bright and brilliant right now in the western sky. There's another star called Arcturus that you could use as well to navigate you. Another bright star, easy to see from New York City, and it's kind of orange. Then let your eyes adjust. Go up somewhere high, and you'll start to see this blurry thing come out and then you'll see the tail. The tail is gorgeous.

Brian Lehrer: Do you need to be in a certain place that doesn't have too many streetlights and stuff like that around sunset?

Jackie Faherty: Ideally, you're somewhere where bright lights aren't in your eye. I was at a building where the George Washington Bridge and all of the traffic was in my view, but I was able to keep my eyes low enough so that I could block those. You really do want to-- Don't do this from Times Square. You're not going to see it. Go to the water. The water is one place I recommend, or rooftop access. You have a building and you can get to your roof. Usually you can get above enough of the lights.

Brian Lehrer: Tonight and for how many nights?

Jackie Faherty: That's hard for me to say because every night it's getting farther and farther away from the sun, so it's getting fainter and fainter, but it's higher in your sky. It should be still visible with the naked eye from New York for the next, I want to say like a week or so you'll probably have it, but then you might need to switch to binoculars.

Brian Lehrer: Just to sneak this in, another one you told us about is that there is another something in the sky, the northern crown, a horseshoe shaped curve of stars west of the Hercules constellation. Literally 10 seconds for you to describe that.

Jackie Faherty: Oh, the corona borealis. Corona borealis is a constellation in the sky. It's considered a crown constellation. It's not hugely bright, but have I seen it--

Brian Lehrer: When?

Jackie Faherty: It's good. Go look for it. It's a beautiful little clump of stars.

Brian Lehrer: All right. Thank you so much. Jackie Faherty from the American Museum of Natural History, astrophysicist.

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