WPBT2's Star Gazers

Episode #12-23 "Measuring the Cosmos"
Air Dates June 4 - June 10, 2012

DEAN: Hey there star gazers. I'm Dean Regas, astronomer for the Cincinnati observatory.

JAMES: And i'm James Albury, director of the Kika Silva pla Planetarium in Gainesville, Florida. Far-out fellow Star Gazer, Marlene Hidalgo, will be joining us to help you find your way around the sky tonight. Hey Dean, humor me. If you want to describe your height, what units of measure would you use?

DEAN: Feet and inches.

JAMES: And if we want to measure the distance to the moon what do we use?

DEAN: I could use feet and inches but using miles makes more sense.

JAMES: How about the distance to stars?

DEAN: Ah, we use light years. Distances in space are so… well… astronomical that it’s hard to wrap our brains around them. So we created new units of measurement to take us around the solar system and through interstellar space.

JAMES: Let's take you to the moon, Saturn, and beyond!


JAMES: Okay we have our sky set up for the morning of Sunday June 10 at 5 a.m. facing southeast. The sun is about to rise in the east but the last quarter moon is still lighting up the pre-dawn sky. All this week the moon will be waning and only viewable in the morning.

DEAN: Every day the moon will shift farther to the east. Here is the moon on June 10…June 11… June 12… and June 13. Let's zoom in on the waning crescent moon and get our tape measure out.


DEAN: On average, the moon is about 239,000 miles from the earth. We can find out the precise distance to the moon any time by bouncing lasers off the reflectors set up by the Apollo astronauts. Neil Armstrong, Buzz Aldrin and company took three days to fly to the 239,000 miles to the moon - and three days to fly back.


JAMES: Our next stop is Saturn. The beautiful ringed planet is definitely a highlight this month. Now we have our sky set to any night this week at about 11 p.m. looking south. About halfway up in the sky you'll find two stars - one on top of the other.

DEAN: The upper star should be a little yellow in color and is no star at all. That's Saturn! To the naked eye, it doesn't jump out at you, but if we zoom in, Saturn is just the most amazing sight to see in a telescope. You can see the planet, the rings, the shadow of the rings, the moons…

JAMES: Calm down Dean… i know Saturn's your favorite planet but let's do some measuring here.



JAMES: This week Saturn is 855 million miles away. Now, that number is hard to picture, so when we're talking about distances in the solar system astronomers use a different unit of measure - the astronomical unit or a.u. One a.u. Is the average distance between the sun and earth, so we're about 1 a.u. From the sun. In miles, that's 93,000,000 miles.

DEAN: So since Saturn is 855 million miles away it is also about 9.2 a.u.s from us. A.u.'s work great within the solar system. For example, we could say Jupiter is about 5 a.u.'s from the sun, Neptune is about 30 a.u.'s from the sun and Voyager 1 -- our farthest flung spacecraft -- is a whopping 120 a.u.'s from the sun!



JAMES: Now what about that other star -- below Saturn in the south after dark? That's the star Spica in the constellation Virgo. Spica is bluer in color -- compared to yellow Saturn -- and is supposed to mark Virgo's hand holding a stalk of wheat. Marlene, take us to Spica.



MARLENE: Spica is about 1500 trillion miles from earth, or 16 million a.u.'s. We could measure the distance to Spica in millimeters if we wanted to, but those numbers lose all meaning. Astronomers use light years as their unit of choice for measuring interstellar space. A light year is the distance light travels in a year -- roughly 5.8 trillion miles. So a light year is a distance like a mile or an a.u.. And Spica is a whopping 260 light years from earth. It's by no means the farthest star you can see with the naked eye. That honor most likely goes to Deneb - the tail star of Cygnus the Swan - who you'll be learning more about this summer. Deneb is over 3000 light years away. That means the light you see from Deneb left it around 1000 BC and is only now getting to your eyes.


DEAN: So this week get outside to see the moon at 239,000 miles away.

JAMES: Saturn from 9.2 a.u.'s away.

DEAN: And Spica at 260 light years away.

ALL: Keep looking up!


Episode #12-23 "Measuring the Cosmos"
Air Dates June 4 - June 10, 2012

JAMES: How far are the moon, Saturn and Spica?

DEAN: Let's get our tape measures and head to the stars!


DEAN: The moon is, on average, about 239,000 miles from the earth. You'll be able to see the waning moon all week in the morning sky. Here it is on June 10th,. The 11th… the 12th…. And  13th.

JAMES: Now let's switch to the evening sky at 11 p.m. looking south. About halfway up in the sky you'll find two stars - one on top of the other. The upper star is really Saturn and this week it's 855 million miles away from us. It should look a little yellow to the naked eye.

DEAN: The star below Saturn is ice-blue Spica, the brightest star in Virgo. Spica is a whopping 1500 trillion miles from earth. If you think the moon and planets are far, each twinkle of every star you see at night has traveled trillions of miles to reach your eyes.

BOTH: Keep looking up!


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