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A partial solar eclipse will begin just as the sun is setting Thursday afternoon. Derrick offers tips for safe viewing. Next total solar eclipse for us not until 2017. The discovery of a relatively nearby, relatively new galaxy has astronomers struggling to explain this anomaly.

October 20, 2014


[Dave Heller] Weather permitting, a partial solar eclipse is visible this week. Let’s set it up with Derrick Pitts, chief astronomer at the Franklin Institute. Derrick: where and when?

[Derrick Pitts] Fortunately in the sky, and during the day! This solar eclipse is going to be taking place Thursday this week. The interesting thing is that the eclipse actually begins for us as we see it just a few minutes before sunset. So with vantage of a clear view to the western horizon, and if you have the proper viewing equipment or you can put together an indirect viewer, you will be able to see these very early portions of this partial eclipse. Now because it’s a partial eclipse, that means only a portion of the sun’s disc will be obscured by the moon passing between the sun and the Earth. As far as visual effects are concerned, because not so much of the disc is going to be covered, it means that we actually won’t see very much change in the light of the sky. You really need to get up to about 80% of disc coverage to be able to see that kind of effect, and for us, that’s not what the case is going to be.

Now, review preferred “indirect viewing” methods.

Sure. Now most of them involve projecting the sun’s light someplace else you can observe it. Now one of my favorites is, you take a plain, flat mirror — like a mirror you’d find in a make-up compact — and you cover that with a piece of black paper, (that mirror with a piece of black paper), and you cut a small hole, oh, about half the size of the mirror into that black paper so that as you cover mirror, that small hole is exposed. Then you capture the light from the sun, and you reflect the beam over onto a shadowed wall. That means you’re not looking at the sun directly, but you’re looking at the reflection of the sun on that wall. Well that reflection will show you how the moon is covering just a part of the sun. The other way you could do it is create what’s called a pin-hole camera. And the pin-hole camera is a device where you take something like a shoebox. You cut a square out of the backend of the shoebox, and you cover that with a piece of aluminum foil. You take a very small nail and make a little hole, and then with the box completely in tact, you cut out the bottom of the box. And then what you do is you hold this so that the aluminum foil points toward the sun, you look in through the bottom of the box and up on the side of the box on the far wall, you see again an image of the sun. And you’ll be able to see how the moon is passing between the sun and the Earth. You’ll see a little bit of the sun’s curvature taken out by the moon. I like the mirror method because you can get a much larger size image that way, but either method works fine.

Northwest to southeast, but hopefully you don’t have to get all the way down to Key West to see it.

No, you won’t have to go all the way to Key West. In fact, the path of totality exits off the U.S. coast somewhere around South Carolina. And so that means if you’re on either side of that line — either to the northeast or the southwest — you’ll only see partiality of the eclipse. The closer you are to the eclipse line, the more closer to totality you’ll become. But even just outside that line, you’ll only see a partial eclipse.

Derrick, astronomers are scratching their heads with the discovery of a relatively new galaxy in proximity to us. Tell us about this youngin’.

Well that’s actually a great question: Is it a new galaxy, or not? Right now, all the indications that we have been studying make it look like it’s a very young galaxy. Now what’s unusual about that is that this young galaxy is not very far from us at all. But, you would assume that a very young galaxy would be observed at a much greater distance. So this galaxy is about 39 million light years away from us. Not all that far in galactic terms. But because of its appearance in terms of age, this is something that we would expect to be 10 billion light years away, 12 billion light years away. So we have a little issue to figure out, here. Is it that the characteristics that we see in this galaxy that make it appear young are actually unique characteristics of a very special type of galaxy? Or is there some other way to explain how a young galaxy would be so close to us. If we did a survey around our local group of 44 galaxies, we find that they’re all old. 10 billion years plus old. And if we look way out to the edge of the universe, we find examples of these younger galaxies. So we have to figure out: What’s going on with this galaxy that makes it look like a young one?

Specifically, are new galaxies being created?

No, new galaxies are not being created. In fact, some would argue that star production in the galaxies that exist now is on the decrease, is on the wane. So we’ve already sort of passed peak stellar production. This may not be entirely true, there is still some work to be done in that area. But some people have come across data that indicates that that’s the case.

And back to our local group which you describe as some 44 galaxies all about 10 billion years old, that’s in context with a universe that’s supposedly how old?

Depends how you want to count it. If you go out to the edge of the observable universe as we can see it, it’s a little over 13 billion light years out, or 13 billion years old.

That’s when the Big Bang supposedly took place?

As we see it in the observable universe part. But if you actually account for the kind of expansion that has taken place in the universe since that time, while the real edge of the universe is more likely something like 45 billion lightyears out.

And in dog years?

Oh, multiply by 7 and you’ve got it.

  • The Universe Nearby. Credit: 2MASS, T. H. Jarrett, J. Carpenter, & R. Hurt / NASA

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