Heart of the Valley Astronomers Questions and Answers

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One of my favorite jests is that Oregon astronomers spend three months of the year looking at the sky and the remaining nine reading about looking at the sky. It's a wild exaggeration, of course. But its during the long rainy months when astronomers will be poring over the books or web pages in the eveningtime, hoping for a clear break. During our outreach programs, kid's inquisitiveness compel us to address astronomy in ways requiring a great deal of preparation mentally. To put it bluntly, you can't be lazy when going about answering them. Which is why we often end up learning as much as the schoolkids when we pay a visit to class. Here is a sample (only a sample) of recent questions from local fourth-graders - along with the answers given:

What are Saturn's rings made of and how were they made?

In the early history of the Solar System, a moon strayed too close to Saturn and got torn apart by Saturn's tidal forces -- a lot stronger than the tidal forces that our Moon has on the oceans. Those rings are what's left of that moon, tiny pieces of ice, dust, and rock. (If this were an adult asking, you would consider Saturn's rings to be the cosmic equivalent of that shiny patina of broken glass and metal on the road after a fender bender.)

Why does Hawaii have a lot of telescopes?

The mountain of Mauna Kea on Hawaii has a lot of very large telescopes mounted on the top of it. In fact it has the largest telescope in the world, the Keck telescope, which measures over 30 feet across. Mauna Kea is used as an astronomy site because it's dark (no stray light). There is plenty of room for telescopes. But most importantly, the height is enough to have the scopes above the layers of smog and water vapor which harm good astronomical viewing.

Do stars have paths? And if so, what kind of paths?

Yes. The stars we see are generally following an orbit around the center of the Milky Way Galaxy, there are a few that move differently. If you keep track of stars over years or decades, you'll find that virtually all stars change their position in the sky. This movement is called a star's proper motion. All things equal, the closer the star is to us, the more readily we'll see its proper motion.

Why is the North Star called Polaris?

The name comes from Old English words meaning polar star. It's fitting because Polaris marks the Earth's north pole.

Is Pluto still considered a planet?

Yes, though some suggest otherwise because it is so small. What is interesting about Pluto is that it measures a little over 1,431 miles across while it's moon, Charon, is about 800 miles across. In other words, they are closer to each other size than any other planet-moon relation in the solar system. This has led some astronomers to consider Pluto-Charon to be a double planet system. For the time being though, Pluto is a planet. Charon a moon.

When is the next total solar eclipse?

The next solar eclipse is set for August 21,2017, the path of totality passes right through Oregon. In fact this Eclipse is being called the Great American Eclipse because the path of totality only passes through the lower 48 United States. You can learn more about eclipses by clicking here

Do you know how many stars are in the sky?

Wow, that's a tough question to answer precisely but look at it this way: there are millions of galaxies in our Universe. Each of those galaxies contains at least several dozen billion stars. The comparison of there being more stars than grains of sand on (Earth) beaches is probably correct. In our own sky at night we can only see about several thousand of them.

Have you ever seen Mercury?

Yes! I remember the first time I saw it. It was on a St. Patrick's Day several years back and I was so excited about seeing it that I dragged the whole family away from the dinner table to view it. Come to think of it, they haven't forgotten that episode as well.

Have you ever seen an alien? And have you dissected an alien?

No, I'm afraid I haven't seen an alien. And my only experience with dissecting was on a worm in high school biology class.

Why is Pluto cold?

Because its so far away from the Sun and its heat. If you could stand on Pluto and look back at the Sun, you would only see just a bright star about the brightness of the full Moon. We don't get much heat from the Moon.

Why is the Sun yellow?

The color of the Sun comes from its temperature. The coolest stars have a red color, while the hottest ones have a blue (really!) color. Stars that have their temperature in between, like our Sun, have a yellow, orange, or white color.

If you got to go to any planet, which one would you go to?

Well, I rather like Earth. But If I could visit another, I'd pick Jupiter. I love looking at the beautiful cloud bands on Jupiter's face through a telescope. Up close, you could spend years enjoying every colorful, intricate detail of them. There are dozens of them. Each band is a weather system that makes the hurricanes on Earth seem puny. And I'd love to see the moons orbiting Jupiter. They're such a neat collection; volcanic Io, the weird terrain on Ganymede, to the frozen oceans on Europa. My favorite times to watch the moons are when they're making a shadow on Jupiter itself.

Do you know if there is a tenth planet?

I would prefer to say that that is still an open question. We haven't found any, but it is also very difficult to find things beyond Pluto - because they would be very dim. We are aware that there is a lot of debris out there. It is possible that there may be a very distant planet in that debris as well.

Why do we study this?

It depends on the individual person, there really isn't one right way to study the stars. Speaking for myself, one reason is that I like looking at what the sky has to offer - there are a lot of beautiful things to see and imagine about. For other people, it's a way to better understand Nature and the world they live in. Others find it relaxing to think about the stars always being there to see amidst our hectic world. Those who aren't terribly interested in the skies' worlds can still find it a useful reminder about the smallness of Earth and the need to take care of it.

How come we can't feel it when the Earth rotates?

Because we're moving along with its rotation - traveling at the same speed as a result. When you're in a car moving steadily at 60mph, you don't really feel how fast you are going. But that changes when the car slows down or accelerates. It's the same way with Earth - except that it doesn't change speed like a car would.

If there was another planet that we might be able to live on, which would it be?

Our best bet is Mars. It doesn't get too cold. There's a surface we can get to without having to deal with high gravity, making it easy to land or leave. Any weather we find there is going to be much easier to deal with than Earth's. Those are just three reasons that come right to mind. Keep in mind though, we'll have to wear spacesuits while we're there - or live in a completely sealed area.

How many constellations are there that people know of?

If you got to both the Northern and Southern hemispheres of the world, you' be able to see 88 constellations.

Why isn't the Sun a planet?

The basic reason is that it's way too big. Besides a vast size and mass difference, the big difference between a star like the Sun and a planet is that a star makes its own heat through nuclear fusion. How? A star is basically a huge ball of (mostly) hydrogen gas. Anything with mass, like gas or dust, has gravity. There is so much gas that its gravity is extremely intense, causing an immense concentration of pressure and temperature with the gas in the center. It is intense enough to cause that gas to begin a nuclear reaction - which is how it gets the heat and light that we see. Planets don't have nearly enough stuff to do this.

One night I saw something in the sky moving very, very, very slow and it was very bright. What was it?

You probably saw a satellite. Even the smaller ones can get remarkably bright if the sunlight hits its body at the right angle. Satellites will move at different speeds, depending on how high up in orbit it is. Satellites in very low orbit will move across the sky very quickly, while ones higher up will move much more slowly.

How many Jupiters can fill the Sun?

You could fit a little over 922 Jupiters in there.

Have scientists discovered another planet beyond Pluto?

No. But I'm not going to completely rule out there being another planet - there is a lot of debris beyond Pluto's orbit. And unless we were looking in the right spot with something like the Hubble Space Telescope, we wouldn't be able to see it.

What are comets and asteroids made of?

A comet can be described as a dirty snowball. It has a lot of ice with a little bit of rock and other material mixed in. An asteroid is just the opposite. They're mainly rock with some metal (usually iron). If an asteroid is far from the Sun, it can also have a little ice on it, too.

Why do planets have to revolve around the Sun?

The planets started as just loose clumps forming from a disc of debris orbiting around the Sun, held by the Sun's gravity. As these clumps formed into planets, they still had the momentum from their beginnings. Since there has been nothing to disrupt that momentum, the planets still have that movement.

Are there planets in the Clouds of Magellan? Note: The Clouds of Magellan are neighboring galaxies seen in the Southern hemisphere.

So far, we're still limited to finding planets around nearby stars. That means we can't find planets as far out as you're asking. But there's no reason why they couldn't exist there. By the way, if you want to learn more about planets around other stars, ask your teacher or parents to look up the Extrasolar Planets Encyclopaedia. It's pretty neat web site at to see what we know, so far, about these worlds.

How can Mercury be so hot on one side and cold on the other?

Because it has no atmosphere, Mercury doesn't transfer heat around it's body. For the same reason, it doesn't retain heat very well either. For the side facing the Sun, it gets very hot - Mercury is very close to the Sun. Once it's not facing the Sun, it cools rapidly to the point that the temperature is like that of Jupiter's moons. That cold.

Mercury is the closest planet to the Sun, but why is Venus hotter?

Mercury is very hot because it's so close to the Sun. But it doesn't have a way of trapping that heat and keeping it on the planet the way that Venus does. Venus has a carbon dioxide atmosphere that's remarkably good at trapping heat energy. This trapping of heat is known as the greenhouse effect.

Which planet is bigger, Mercury or Pluto?

Mercury is larger. It's about 3,050 miles wide (or in diameter), while Pluto measures only a little over 2,100 miles. Pluto also has a moon, Charon.

How hot does Venus get?

About 850 degrees Fahrenheit, hot enough to melt lead.

What exactly is a launch pad?

It's just a concrete and steel base to support a rocket prior to liftoff. It contains piping to transfer fuel and other fluids to the rocket. You'll also see elevators and walkways for people to get at the rocket - either to service or supply the vehicle. A distinguishing feature of the Space Shuttle launch pads are huge white towers at the top of the pad. They are giant lightning rods intended to protect the shuttle. Did you know that Apollo 12 got struck by lightning (twice) as it went off to the Moon? Fortunately, none of the astronauts were hurt and the spacecraft made a successful trip to the Moon.

What is the main difference between an asteroid and meteorite?

Location. An asteroid is a large chunk of rock (a meteoroid is a small piece) that is in space. Hasn't hit Earth, in other words. A meteorite refers to any piece of rock that has entered the atmosphere and actually hit the ground. We can hold a meteorite, but not an asteroid or meteoroid. Yet.

Some of those, needless to say, took some time in tracking down an answer for. If you have any comments or questions for us please tell us. We'll address them in future columns if you like.