Lake Afton Public Observatory

A1. Jupiter's moon Io has active volcanoes! Venus has volcanoes that are active - nobody is really sure if they are active or not. Neptune's moon Triton has geysers of liquid nitrogen. Other solar system moons have had ice or water vulcanism. On these frigid moons water is the lava. You can learn more about all this hot stuff from the Nine Planets at:

A2. First off, you aren't going to find any interesting pictures of this asteroid. Since this asteroid has not been visited by a spacecraft it will look like a streak of light on a photo of a starry background. I found such a photo of this asteroid at

A3. Perhaps you know of something that I don't. I know of no discovery of liquid water on Titan. Titan is likely made up of about half frozen water and liquid water is quite unlikely since its surface temperature is thought to be -290 F.

The only moon that sounds anything like your description is Jupiter's moon Europa. Europa is thought to have a solid rocky core that is sourrounded with a liquid water ocean and an icy crust. Nobody knows how thick the icy crust is, but it seems that liquid water flows or erupts to the surface from time to time. If this ocean has been liquid since the formation of Europa it would seem to me that there is a chance of life there.

For more on Titan see:

A4. Venus isn't made of gas. It is a rock planet like our Earth. Venus does have a dense carbon dioxide atmosphere. Carbon dioxide is not a flammable gas.

The outer gas planets of Jupiter, Saturn, Uranus, and Neptune do have substantial amounts of hydrogen in their atmospheres. Hydrogen here on Earth is extremely flammable - explosive in fact. But there is no oxygen in the atmospheres of these worlds to combust with and so they can't explode.

A5. Hold up your right hand in the "thumb up position". If your thumb is pointing north the fingers curl around counterclockwise. This is the direction that our Earth rotates, the direction that the Moon orbits about our Earth and the direction that all the planets orbit about our Sun.

A7. Well, we really don't know what, if anything, was seen by the Hubble Space Telescope near Proxima Centauri. It is possible that they have directly imaged a large planet or possible a brown dwarf. Further observations are necessary to confirm or reject any possible finding. A nice article from New Scientist on this can be found at:

A7. The Sun is our star. Our Earth, and all the life on it, gets its heat and light from the Sun. Without the Sun Earth would be a dead, frozen world.

The Sun is also important because it is the closest of all the stars. Much of what we know about the stars comes from what we know about our own star - the Sun. By studying our Sun and then comparing it to the other stars we can learn about them as well.

A8. As for our own solar system, it is just the nine planets that everyone knows about. Years ago, people at various times observed what they took to be a planet closer to the Sun than Mercury which was called Vulcan. No observations of this were ever confirmed and it does not exist.

Lots of information on this can be found at

A9. The odds of a collison between Neptune and Pluto are zero. Yes, the orbits cross when viewed from above but if you look at them from the side you will see that they are really no where near each other at this point. The highly tilted orbit of Pluto carries it far out of the plane of the orbits of the other planets including Neptune.

A10. Asteroids are the rocky leftovers from the formation of the solar system. They are the solid debris that didn't from into planets. Our solar system contains many thousands of asteroids with more being discovered all the time. Most (but certainly not all) of them are scattered about between the orbits of Mars and Jupiter. As the solar system was formeing the gravitational pull of Jupiter helped to keep these bodies from pulling together to form a planet.

A11. Nobody is sure if there is water on the Moon or not. A space probe named Clementine found, in 1994, evidence of water ice at the Moon's dark shadowed south pole. One would only expect to find water ice on our Moon in areas like those at the poles that are always in shadow. The Moon has no air and it gets pretty hot during the day so water can't easily stay on the Moon.

If we wanted to live on the Moon it would be very helpful to find water ice already there as water is very heavy and expensive to lift off of Earth.

More recently (1998) a space probe called Lunar Prospector has confirmed the findings of water at the Moon's south pole and also found some at the Moon's north pole. All together Lunar Prospector found somewhere between 10 to 300 million tons of water ice scattered inside the craters of the lunar poles. To many's surprise, Prospector detected nearly 50% more water ice in the north than in the south.

Some Lunar Prospector scientists caution that direct confirmation of these findings is still needed.

A13. Yes it was called Luna by the Romans, Selene and Artemis by the Greeks, and many other names in other mythologies. But it seems that most of us, including me, just call it the Moon. Many folks don't capitalize the M in Moon though. You will find that many people also don't capitalize the E in Earth. It seems tom that these are their names so I always capitalize Moon, Earth, and Sun.

I don't really know why this is. People and thier rules for language can be strange, can't they?

A14. There are many ways of defining the size of the solar system. One way would be to use the size of Pluto's orbit. Another would be to use the location of the comet's within the Sun's Oort cloud. Careful orbital calculations done in 1950 by Jan Oort indicate that a huge spherical "cloud" (now called the Oort Cloud) of perhaps a trillion (1e12) or more comets orbit the Sun far beyond the orbit of Pluto from about 30,000 AU to a light-year or more. This would produce the two light year figure that you quoted above. Yet a third way would be to mark the edge of the Sun's influence on space. Here we are talking about where the Sun's solar wind (the charged particles that stream outward from the Sun) meets the stellar wind from nearby stars. We aren't sure just yet where that boundry lies.

A15. As you may know our orbit about the Sun isn't quite a perfect circle so some times we are a bit closer to the Sun and sometimes we are a bit farther from the Sun. Our closest approach to the Sun is known as perihelion and it occurs just a few days after New Year's Day. This year (1998) we were at perihelion on January 4th.