From CYG group, Varna, Bulgaria. Please reply by email to: astro@ms3.tu-varna.acad.bg.

A. Quizzes for young amateur astronomers

• 1. What is the direction of a comet's tail with respect to the Sun? Why?
• 2. Is it possible two meteor showers, active in different times of the year, to be caused by one meteor stream? Name an example.
• 3. What caused the shrinking of the cosmic cloud of which our solar system was formed?
• 4. Is the Hubble's constant really a constant? Why?
• 5. Why the inner planets contain so much heavy elements, while the outer planets consist mostly of gases?
• 6. Which are the three stars closest to us?
• 7. Which of the asteroids can be observed by the naked eye?
• 8. Who made the first reflector telescope?

B. Questions addressed to professional astronomers

Please answer to the email above! We shall be thankful for your replies! After a few days, we will write the answers and publish them in the Astronomy On-Line Newspaper.

I. Questions asked by Galin Genchev, 17 years old:

• 1. How the parallax of a star is measured in order to determine the distance to the star?
• 2. How astronomers measure the luminosity of the stars?
• 3. It is known that the trajectory of the Sun around the galactic centre is not flat, the Sun plunges and emerges above the galactic plane like a dolphin with a period of about 25 million years. How far from the galactic plane does it go?

II. Questions asked by Denis Mehmedov and Elena Sarbinska, 12 years old:

• 1. Do the black holes emit radio signals?
• 2. How would the starry sky look like on a planet orbiting the farthest star from the centre of our Galaxy?
• 3. How will the orbital motion of the planets change when the Sun becomes a red giant? What will happen then to the life on the Earth?
• 4. Is there in the Universe a kind of matter that resists the gravity?
• 5. Have the asteroids gravity?
• 6. Why men still haven't visited Mars?
• 7. Who created the largest (10 m) optical telescope? Which was the first object observed by it?

Place and Date: Astronomical Observatory & Planetarium "N. Copernicus", Varna (Bulgaria) - 12 November 1996.