: A comet. Now I didn't even know that it was happening up until a few weeks ago.
Joining me to talk about it is Derrick Pitts. He is chief astronomer at the Fels Planetarium. And that's at the Franklin Institute Science Museum in Philadelphia.
Welcome back to the program, Dr. Pitts.
DERRICK PITTS: Thank you very much, Ira. I appreciate it.
: This sort of caught us by surprise, at least most of us, I think.
PITTS: You're right, it did. Particularly in the idea that it's visible in the evening skies, you know, almost with the naked eye.
Some astronomers have been aware of this comet since August, when it was first discovered. But it brightened so slowly at first that it really didn't seem as if it was going to become the, you know, wonderful sky piece that it has over the last five days or so.
It really zoomed up in brightness and then really became easily visible in the evening sky right after sunset. And that was the big surprise, was that we really had no warning about that.
: Let's go through the five Ws. What's it called?
PITTS: This comet is called Comet McNaught. It's the 31st comet discovered by an observer, an astronomer, out in Siding Spring Observatory in Coonabarabaran, New South Wales in Australia. And this particular one turns out to be easily visible for us.
: And where can you see it?
PITTS: You can see it in the southwestern sky almost right after sunset. Sunset these days is running right around five o'clock. It's 4:56 for those of us around 40 degrees north latitude here.
And you'll be able to see it, though, for only about 30 minutes right after sunset. And there's a real battle here, Ira, between sunset and when the comet sets. The race is between the sky getting dark enough to see it and the comet hitting the horizon. That's how close the gap is.
So that's one opportunity. And the other opportunity is in the morning just around - just before sunrise over in the eastern sky. And you can see it there also.
But the trick for both is that the comet is very, very low. So in order for someone to see it you need a really clear view of the western horizon, unobstructed by trees, buildings, anything like that. And the next clear sky you have, give it a shot. You only have today and tomorrow.
: Oh that's too bad. Talking with Derrick Pitts at the Franklin Institute Science Museum on the TALK OF THE NATION: SCIENCE FRIDAY from NPR News.
Yeah, I tried to see it last night. And, you know, we had clouds in the way here in the east. And you really have to get down to a low area.
PITTS: You're right.
: But it's quite visible, isn't it? You can see it with the naked eye.
PITTS: Yes. It is naked eye visibility. Although I would hesitate to say that it is - you know, if you had a really clear sky with nothing in the way, it probably would catch your attention. But if you weren't aware of it, you might not immediately - it wouldn't pull your eye to it directly.
: You might think it's a planet or a star.
PITTS: You might think it's a jet contrail or something of that sort. But there's a really interesting aspect to this, Ira. And that is that you can see the images of this comet not only online from images contributed by other people but it has now come into the view of certain satellites that regularly observe the sun. And you can go to those Web sites and see the comet's progress as it orbits around the sun.
: Wow. And so it's seeable just for the next two nights, the next two evenings?
PITTS: Yes. It's tonight and maybe tomorrow night if somebody has a really clear view of the horizon. Again, it'll be quite low. But that'll essentially be it.
: And that - when it comes back around, you know, because it's so close to the sun coming around again.
PITTS: That's right. When it comes back around it will actually become visible to observers in the Southern Hemisphere. So if you're heading down towards South America or out towards Australia, you'll have an opportunity to see this comet.
For those of us in the Northern Hemisphere, though, we're done until the next comet becomes visible to us.
: Do we know when that is?
PITTS: Well there are a number of comets that are already in the evening sky. In fact, there are about 67 currently visible. But let me clarify that they are way, way below visibility for the naked eye, something like 25,000 times dimmer than we can see at least. So we just have to hope that we have something bright that comes at us pretty soon.
: Is it actually possible to take a picture of this comet?
PITTS: Yes, it is. If you have a digital camera and you have a clear view, you can get out and take a photograph of it without too much trouble.
: And what would the satellites be looking for if they - the satellites focused on the sun, what would they care about the comet? What are they looking for?
PITTS: Well here's how it works. One of the satellites - one of the best- known satellites that's viewing the sun is one called the SOHO satellite. And that stands for Solar and Heliospheric Observatory, SOHO.
This satellite is set up to view the sun 24 hours a day to look for all sorts of solar disturbances like flares and prominences and eruptions and things like that.
Well because the satellite is directly looking at the sun - it has a field of view that only looks directly at the sun - when a comet comes into make its path around the sun, the comet will show up in the field of view of the SOHO satellite. So now what astronomers can do is use the SOHO images to study both the trajectory, the path, the orbit, and some about the nucleus and the coma, as well as the tail of the comet, as it makes its way around the sun heading out on the other side of the solar system.
: Terrific. Well, Derrick, I wish you good viewing. I hope you're going to get a shot of it there in Philadelphia.
PITTS: I wish we would but, Ira, it's not looking the best right now.
PITTS: But conditions are a little bit better than they were yesterday at least.
: All right. Maybe in the morning may be the better time to get...
PITTS: Yes. And good luck to you, too. And hopefully some of our listeners out there will be able to catch it where they are.
: Yeah. Send us your pictures. Derrickk Pitts, chief astronomer at the Fels Planetarium at the Franklin Institute in Philly. Thanks again.
We're going to take a short break, switch gears, and come back and talk about the green cars, or at least one green car. And what is the future of green automotive business at the Detroit auto show, the North American Auto show.
So stay with us. We'll be right back after this short break.
TALK OF THE NATION: SCIENCE FRIDAY from NPR News.
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