Astronomy: Top 10 Questions

December 2009

Thanks to Dr. Kenneth Carpenter, Hubble Space Telescope Operations Project scientist for the answers.

1: Who made the Hubble Telescope?

The making of the Hubble Telescope took the collaborative efforts of many people. The Goddard Space Flight Center and the Marshall Space Flight Center (both parts of NASA) helped put the telescope together originally and managed the program of building it. Numerous astronomers/scientists from around the world defined the requirements for the telescope, and then there were aerospace corporations from across the United States that came together to build, assemble, and test the hardware. Then they launched the Hubble Telescope into orbit. (From Faith in Mrs. Childers' class at Hayden Meadows Elementary School in Hayden Lake)

2: Why isn't there any gravity in space?

Actually, there is some gravity in space. When you are right on the surface of a planet, like earth, the gravity feels pretty strong. The further away you are from the surface, the weaker it gets. Halfway to the moon, gravity will actually pull you toward the surface of the earth, but it does it very slowly and it feels like there is no gravity. You are actually in a free-fall where you are moving toward the earth, but there is nothing to stand on so you don't feel any force of gravity. (From Hannah who is homeschooled in Pocatello)

3: How fast does a star go?

Different stars move at different velocities depending on where they are. Our own sun is part of the Milky Way Galaxy, which is a collection of many hundreds of billions of stars that form a shape similar to a saucer. Think of a plate with the stars spread all over the plate. We are about one-third of the way out from the center of the plate, and we move in a big circle around the center of the galaxy. Most stars orbit around the galaxy in that way, but there are also high velocity stars that move up and down in different directions out of the plane of the galaxy. So, you have some stars that move very slowly at maybe tens of miles per hour and others that move at hundreds of miles per hour. (From A.J. in Ms. Brando's class at the Northwest Children's Home Education Center in Lewiston)

4: Why is there no oxygen in space so people cannot breathe?

When you get off the surface of planets, the concentration of elements, like oxygen, is very low. There is oxygen in space, but it is so thin and so rare that there is not enough for us to breathe. When we look at light that comes from stars in the distance down to earth, we can see the signature of atoms like oxygen because the oxygen absorbs a certain color of light. If that color is missing, it means there is oxygen there. It's just in very, very small amounts and not enough to keep us breathing and healthy. (From Leif in Mrs. McCoy's class at Donnelly Elementary School in Donnelly)

5: How hot is the sun?

The sun's temperature at the surface is almost 6,000 degrees, but it warms up as you go to the interior of the sun. At the very center of the sun, the temperature is hundreds of millions of degrees! It is so hot that hydrogen atoms actually fuse together and release energy. This is what powers the sun. This energy trickles out through layers of material until it gets to the surface where the temperature is about 5,800 degrees. (From Christina in Ms. Brando's class at the Northwest Children's Home Education Center in Lewiston)

6: What are stars made out of?

The universe started out with hydrogen and helium and that is what most stars are made out of, but stars that came later manufacture the heavier elements. This is what you, I, and earth are made out of. (From Alex in Mrs. McCamish's fourth grade class at Cynthia Mann Elementary School in Boise)

7: When was the first telescope invented?

In the early 1600s, Galileo invented the first telescope that was actually used for astronomy. Before that, a number of people used pieces of glass to magnify their views of things on the ground. Galileo heard about that and made some adaptations so he could look at things in the sky. Galileo invented the first astronomical telescope, but there were several Dutch people who invented telescopes for using on the ground. (From Claire in Mrs. Miller's class at Caldwell Adventist Elementary School in Caldwell)

8: Why was Pluto dropped as a planet?

Pluto is very small compared to the other planets. It doesn't really dominate the region of space that it orbits through and you sort of need that to be a planet. When we look out there now, we see smaller and fainter objects in the outer regions of our solar system. We call these dwarf planets and they are the size of Pluto. Right now, we know of about five dwarf planets, but the number could easily go up to 50 in the next couple of years and some people even believe there could be two to three hundred of them. (From Allyson in Mrs. Hunt's class at Cynthia Mann Elementary School in Bosise (and many other kids with the same question))

9: Why do they call it the Milky Way?

The name comes from the Greeks long before people could use a telescope. When they looked at the sky on a dark night with just their eyes, instead of seeing individual stars, they saw a milky kind of cloud structure that looked like a milky river going across the sky. So, it was named the Milky Way. (From Caitlin in Mrs. Tanner's class at Hayden Meadows Elementary School in Hayden Lake)

10: What is the big red spot on Jupiter?

We have known that this red spots exists ever since Galileo saw it in 1609, but we don't really know what it is. We think it is most likely a huge storm in Jupiter's atmosphere. It's like a hurricane on earth except that instead of lasting for a few days or weeks, it has been going on for 400 years or more. We believe it is a massive storm on Jupiter. (From Hannah in Mrs. Hudson's class at Dalton Elementary School in Coeur d'Alene)

September 2006

1: What are planets made out of?

We normally split the planets into a couple of different groups. The inner four — Mercury, Venus, Earth, and Mars — are rocky planets. What they're mostly made of is rock and metal. The next four out — Jupiter, Saturn, Uranus, and Neptune — are gas giants. So they're made mostly of lighter elements of gasses and liquids. Uranus and Neptune probably actually have liquid surfaces. Then when you get farther out, you get to the Kuiper Belt, which contains Pluto and similar objects that are made of mostly ice. (From Andrew in Boise)

2: Is it true that if the earth was one inch closer to the sun or one inch farther away, it would burn up or freeze?

It would take quite a bit more than an inch, I think. If the earth were a lot closer to the sun, like Venus, it could make a really big difference. The planet Mars is about twice as far from the sun as we are, and very roughly speaking, it has a very cold surface. So if the earth were as far out as Mars is, it would be a lot colder. But an inch probably wouldn't make much of a difference. (From Ester in Boise)

3: What are stars made of?

Most normal stars, like our sun, are made mostly of two kinds of the lightest elements: hydrogen gasses and helium gasses. They're about 75% hydrogen, and the rest is helium. Almost all normal stars are made mainly of those two types of elements. (From Marissa in Mrs. Kerr's class in Boise)

4: What different kinds of galaxies are there?

A galaxy is a loose collection of stars. Our galaxy is called the Milky Way. It is a spiral galaxy. It has a center mass of stars and then arms wrap around the center. There are different kinds of spiral galaxies where the arms are wrapped tighter or more loosely. Sometimes they are like a bar of stars in the middle, around the center, which is called the nucleus of the galaxy. And some galaxies are just elliptical or irregular, so they're sort of oval blobs or even irregular blobs of stars. (From Mrs. Chettergreen's class)

5: How does the sun go up and down each day?

That's an important question. We call it the rising and setting of the sun, but the way we talk about it is a little misleading, because the sun isn't really moving much. It is the earth that is spinning around in the sun. If you just looked at something in your classroom, looked straight at it, and then you started to turn your body, it would appear that the object was moving when actually it's you that's moving. That is why it only appears the sun is moving, the sun is fixed and the earth moves around it. (From Daniel in Idaho Falls)

6: How are black holes created?

Black holes are some of the most interesting objects in the sky. It takes a very special kind of environment to create a black hole. The basic idea of a black hole is that if you can put enough matter in a small enough space, then gravity becomes by far the strongest force that exists there. Normally, gravity is a pretty weak force, even though it's the most important force of astronomy. But if you can put together enough mass, gravity becomes dominant. That's why light won't escape from the black hole. (From Nicole in Mrs. Hunt's class in Boise)

7: What is a supernova and what makes them?

Stars are converting hydrogen and helium to heavier elements in their cores, and that's what makes them shine. It's what makes them burn and produces the light and heat we get from the sun. Eventually a star will run out of hydrogen and helium and the other elements in its core. At that point, the star will collapse. If the star is massive enough, the collapse will compress it until it rebounds in this big explosion, which is what we call a supernova. What's left at the core of that can be called a neutron star or even a black hole. (From Justin in Mrs. Hunt's class in Boise)

8: Are there any other dwarf planets?

There's one other dwarf planet, and it was just named Eris. (From Sam in Mrs. Kerr's class in Boise)

9: Does Pluto have a moon?

Pluto is known to have three moons right now. It has one large one that's called Charon. And they just recently discovered two smaller moons, so it's possible there are more. (From Becky at Cynthia Mann Elementary in Boise)

10: Why was Pluto made a dwarf planet?

Pluto is a lot different from the major planets, the first eight planets that we have always known about in our solar system. Pluto is much smaller and a sort of icier place. Over time it became known that Pluto had a lot more in common with other small, rocky, icy objects far out in our solar system. People started to think that Pluto was more like these things.

When scientists found some of these objects that were actually bigger than Pluto, they started to think, "Well, if Pluto is a planet, why shouldn't these larger ones be planets, too?" And so that's why the whole question of whether Pluto was a planet or not came to the forefront and they decided Pluto had more in common with these other objects than with normal planets. So they voted to reclassify Pluto as a dwarf planet. (From Emily in Idaho Falls)

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