During the growth of planetesimals to protoplanets, could the ...

[lidoalex]

During the growth of planetesimals to protoplanets, could the planetesimals have collided into one another? Why or why not?
 
  What will be an ideal response?

Question 2

Interstellar extinction and the reddening of light by the interstellar medium (ISM) are both caused by _____.
 
  a. atoms and molecules in the ISM
 b. only atoms in the ISM
 c. only molecules in the ISM
 d. only dust in the ISM
 e. dust, atoms and molecules of the ISM

[carlsona147]

Answer to Question 1

If planetesimals had collided at orbital velocities, they would have been unable to stick together. Typical orbital velocities in the Solar System are many kilometers per second. Head-on collisions at these speeds would vaporize the material. However, the planetesimals were all moving in the same direction in the nebular plane and didn't collide head-on. Instead, they merely rubbed shoulders, so to speak, at low relative velocities. Such gentle collisions would have been more likely to combine planetesimals than to shatter them.

Answer to Question 2

d

[lidoalex]

Excellent

[juliaf]

Gracias!