10Apr2016

Astronomy Makes My Head Hurt

Hurt

Considering just how far away the cosmos is, the numbers can get so mind-boggling, wrapping your brain around them could make your head explode!

Sometimes I have difficulty understanding exactly just how big the Universe is. Does anyone know exactly how big the Universe is? Is there anything beyond the fringe of “our” Universe? We are told the Universe is expanding. How fast is it expanding? Is it expanding any faster or slower? What is the Universe expanding into? The Big Bang Theory, primordial soup, quantum theory, time, space, black holes…. it’s all fascinating. The more we seek, the more we learn. There seems to be so many things beyond our knowledge.

To avoid making a mess of your mind, make use of some handy units of measurement designed for astronomy. First off, let me start with a unit we all know and love — the mile. To give you some perspective, the diameter of the Earth is about 8,000 miles and the circumference at the equator is just under 25,000 miles.

The closest celestial object in the heavens, be it human-made, is the International Space Station that circles our world once every 90 minutes at a height of around 250 miles. If it happens to be passing above Rochester, you can’t miss it. It’s so easy to see, no binoculars or telescopes needed.

I think a lot of folks mistake it for a high-flying aircraft. It resembles a super-bright star generally pushing from the west to east at various heights across the celestial dome. The best website, in my opinion, to keep up with space station’s comings and goings is www.heavensabove.com. Just set your location with the data base provided and you’re good to go. The next-closest celestial body is the moon, with an average distance of about 238,000 miles.

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Now, I can deal with hundreds of thousands of miles, but when it comes to millions of miles, the distance of the planets in our solar system, that’s when I need help. For example, the brightest planet in the night sky right now is Venus. It resembles a super-right star shining like a beacon in the eastern early morning sky.

Venus is about 130 million miles away right now. An easier way to express distances in our solar system is in astronomical units. They’re really simple. One astronomical unit (A.U.) equals 93 million miles, the average distance between the Earth and the sun. That would put Venus at about 1.4 A.U.’s away, which is fairly close by, as planets go.

Venus’ brilliance is not only due to its proximity to the Earth, but the fact that the planet, about the same size as our Earth, is completely swamped in a heavy atmosphere that’s very reflective of the sun’s light. By the way, if you’re considering travel to Venus anytime soon, I would reconsider. That thick atmosphere contains lovely things like carbon monoxide gas laced with acid rain.

Even If you got by all that and reached the surface, you’d be subjected to crushing atmospheric pressure exceeding 90 times that of Earth. You’d also be well-baked, with surface temperatures as high as 900 degrees. Talk about a pressure cooker.

Another planet in the early evening sky now is Saturn, high overhead and easy to spot . It’s not as bright as Venus but is distinctive because of its ‘yellowish’ star-like appearance.  It shines at us from 893 million miles, or 9.6 A.U.’s away. But even that far away, Saturn in so gigantic that even with a small telescope you can see the ring system and maybe even some of its moons.

For stellar distances it would absolutely silly to talk about them in miles. The next-closest star to our sun is Proxima Centauri. That star is nearly 25 trillion miles away — in longhand, that’s 25,000,000,000,000 miles. As humongous of a number that is, it’s celestial chickenfeed compared to distances of other stars, many of which we can see every night with just our eyes.

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I asked my science teacher at school this and he said,..”why you ask so many questions ?”

That’s why it’s best to express stellar distance in light years. A light year is defined as the distance a beam of light travels one year’s time. Using the speed of light, 186,300 miles per second, one light year computes out to be 5.8 trillion miles. That would put Proxima Centauri at about 4.3 light years away.

The next brightest star close to Saturn  is Spica. Spica is 263 light years away. You certainly wouldn’t want to express that in miles. Actually, though, there are some stars you can easily see just with your eyes that are thousands of light years away. In fact, there are whole other galaxies of stars that are more than 10 billion light years away!

Light years are cool because not only do they express distance, but time. Since a light year is the distance light travels in one year, then the light that you see from a star that’s 10 light years away takes 10 years to reach your eyes. The light you see from a star a 100 light years away would take a century to reach you. If a star is a 1,000 light years away, it would take a millennium for the light to reach you.

So when you’re stargazing on these cool winter nights, keep in mind that not only are you looking into incredibly faraway places, you’re peering way back in time. Don’t let your head explode!  Source: Post Bulletin

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