Here are some thought-provoking questions sent to Small Planet from net surfers interested in astronomy. Check them out and write back if you know the answers.

Puzzle #1

Alan Stewart writes: I am employed by the Canadian Coast Guard as an electronics technician. About eight years ago we supplied the platform, CCGS Narwhal, for a hydrographic survey in the eastern part of Hudson Bay just North of Kkujjuarapik. (Kkujjuarapik was previously known as Great Whale River.) The topography of the region was very unusual in that it was greatly fractured. At the time I thought it resembled a meteoroid crater. If it is, it would be one of the biggest in the world. Has anyone considered the area as a hit site?

Here's a more detailed description of the location: Draw a circle with the center just north and west of the Belcher Islands (80 deg. W, 48 deg. N) with a radius of approximately 140 mi. The easternmost point on the circle's circumference (75.5 deg. W, 48 deg. N) is on the shore of the Province of Quebec. Inside this circle the bay's bottom is very jagged, from a few feet to many feet deep in a very short distance. I understand, but have not witnessed, that the rest of the bay is relatively flat. On the shore of Quebec there is an arched coastline that rises from the water to several hundreds of feet and then drops off to a flatter area behind the arch. The ground around this arch comprises mostly a slag-type material. On shore and in the water there is very little vegetation or wildlife. North and south of the site there is a great abundance of wildlife.

Answers

From Don Moffatt, ScienceWeb Editor: This apparently was long suspected as a possible impact site on the basis of the outline of the bay, but there isn't conclusive evidence that it is. There is fairly extensive information on this in Meteorite Craters by Kathleen Mark, University Press, isbn 0-8165-1568-9 (paperback). The feature is known as the Nastapoka Arc, and has been compared to Mare Crisium on the Moon. There is "missing evidence," which suggests that it isn't an impact structure, however: "Negative results were . . . reached by R. S. Dietz and J. P. Barringer in 1973 in a search for evidence of impact in the region of the Hudson Bay arc. They found no shatter cones, no suevite or unusual melt rocks, no radial faults or fractures, and no metamorphic effects. They pointed out that these negative results did not disprove an impact origin for the arc, but they felt that such an origin appeared unlikely." (p. 228)

From Chris Aikman: The idea of Hudson Bay as a circular impact feature was suggested at least as far back as the 1950s. However, as far as I know, it has none of the geophysical features associated with impacts. It originates, I believe, from the depression of the earth caused by the weight of the glacial load on it during the ice ages.

Link to a related site: To learn more about meteorites and their impacts on Earth, visit the Lunar and Planetary Institute website.

Puzzle #2

Tihomir Marjanac writes: I remember, decades ago, a theory that asteroide belt originated from destruction of the hypothetic planet Phaeton. When was it last that anybody wrote about it, and who is to credit for this hypothesis, anyway? Thanks!

Answers

From Donovan Colbert: I was just reading that the combined mass of all the debris in the asteroid belt would constitute a "planet" less than 1000 miles in diameter, roughly half the size of our moon.

To learn more about asteroids, visit Asteroids Overview on the NASA website.

Puzzle #3

An amateur high-school astronomer writes: Hi, I am an amateur astronomer in high school and I have never clearly understood the concept of a black hole.

Does a singularity have an event horizon or is it just during the white dwarf stage that it has one?

And if it does, then does the event horizon of a singularity have the most gravitational force compared to the singularity itself?

These probably seem like easy questions to you but I would really appreciate it if you could clarify the concept of a black hole to me.

Thank you.

Answers

From John Rogers, amateur astronomer (future professional astronomer): This is a concept that we should all learn about the Universe in order to learn about black holes and how they are formed. As you probably already know, I hope, black holes are stars that are formed from gravity collapsing into itself causing it to suck in all objects in the "field," therefore causing a black hole.

From Evan Dagg of Thunder Bay, Ontario: To answer your question about black holes, I'll start from the beginning. The only stars that turn into black holes are the largest supergiants. These stars enlarge and explode, collapsing under their own gravitational pull. They shrink past the neutron star stage. Everything within a one light year radius gets sucked in. I hope this can help answer your question about black holes. Good-bye.

From an Iowa high school student: Black holes are neutron stars so condensed that it would be like a marble weighing 20,000,000,000 tons!!!! Therefore the mass is so huge that it sucks on matter and because it is so dense the escape velocity is over the speed of light when on earth it is around 25000 mph compared to the speed of light it is obvious that a black hole is many times more dense than the Earth.

To learn more about black holes, visit First Image of a Black Hole on the NASA website.

If you have answers to any of the puzzles above, write to Small Planet. We'll post any relevant information or answers we receive at this site.

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