help with homework...Astroid Questions??

Question

Why were asteroids not discovered until the 19th century?

A.although asteroids are the same size as the planets, they are completely covered with dark dusty material, which means they reflect almost no light

B.several asteroids collided with each other in early 1801, calling them to the attention of astronomers

C.in their long looping orbits, it was not until the 19th century that an asteroid came close enough to the Earth to be detectable

D.only after Halley's work did astronomers think to look for the tails which allow us to spot an asteroid

E.asteroids are generally small compared to planets and require a
good telescope and patient searching to spot them

I'm almost postive it's A.

If there are at least a million asteroids, how did spacecraft like Galileo survive their trip through the asteroid belt?

Answer 1

The answer is E.

As for the asteroid belt, despite having millions of asteroids, those are all spread on on an orbital path around the sun greater than that of Mars. Thats a lot of space to fill up, even for millions of chunks of rock floating around.

Answer 2

You are correct, There are indeed thought to be more than a million asteroids. At the latest count, a month ago the total of known asteroids had surpassed 364,000. So it could not possibly be A (a mllion planet-size objects between Mars and Jupiter?) could it?

With such a plethora of asteroids, the answer has to be E. There are thought to be more than a million asteroids above 1 kilometer in diameter is the precise statement. There are barely 20 asteroids of 200 kilometre diameter or more. Ceres, the biggest, accounts for 32% of the mass of the entire asteroid belt, which is collectively a mere 4% of the mass of our Moon. And the next 6 most massive with Ceres, between them account for 54% of the mass of the entire belt.

However the true answer is more complicated than a multiple-choice question can get to grips with.

The point is that nobody thought to look until the discovery of Uranus by Herschel in 1781. The distance that Uranus was from the Sun was almost exactly that predicted by the Titius-Bode Law (see link).

This predcted that there was a missing planet betwen Mars and Jupiter and the credibility of the Law having been given a boost by Uranus fitting the pattern, Bode, the director of the Berlin Observatory, then urged astronomers to go looking for The Missing Planet. Several such teams then worked on the Hunt.

This is why the first 4 asteroids were found in quick succession from 1801-1807 (1 Ceres, 2 Pallas, 3 Juno and 4 Vesta).

They knew where to look and when Ceres was found it fitted the Law by being in almost exactly the place predicted for it.

They were all called planets initially. They had no other word for them if they were not moons of planets. By the 1850s there were 15 of them, and we had 23 planets (Neptune had meantime been discovered in 1846),

Herschel felt they were all disappointingly small in comparison to Uranus and in 1802 coined the name "asteroid" (meaning "star-like") but this did not become generally used until all 15 were demoted from planetary status in the 1860s.

So it is a little bit more complicated than E suggests!

Answer 3

Definately E.
They might be covered in dark material, depending on the asteroid, but they're definately not the size of planets. As for Galileo, the asteroids are very far apart, and they're in a ring; Galileo could have just gone between them, or gone over/under this ring.

Answer 4

E. They are most definitely not the size of planets.

There may be millions of them, but 'space' is huge. It's not like there is a solid wall of asteroids between Mars and Jupiter -- not even close. There is a LOT of space in between the asteroids -- even millions of them.

.

Answer 5

im pretty sure the answer to this question has to be C. remember, the 19th century really means the 1800's...before that, telescopes simply werent powerful enough to see anything beyond the solar system and all asteroids are outside that boundary...A. cannot be the correct answer because the vast, overwhelming majority of asteroids are no where near the size of planets.