week 11

A Herbig-Haro (HH) object is

A Herbig-Haro (HH) object is

The star now called Kepler-444 is 11 billion years old (much older than the Sun) and has five planets orbiting close to it. What has this system taught astronomers about the history of star formation or our Universe?

If such an old star has planets close to it, where it's really warm, those planets must be made of heavier elements. So heavier elements must have formed before the time this star formed.

Supposing we launched a very fast dart from the Space Shuttle, pointed in some direction away from any planet, so that it could travel beyond the solar system. What would it be most likely to hit first after traveling outward for a while?

an atom of interstellar gas

If an astronomer wants to find the distance to a star that is not variable and is located too far away for parallax measurements, she can:

find the star's luminosity class from its spectrum and read the luminosity from an H-R diagram

Which of the following statements about interstellar matter is FALSE?

if the matter were spread out evenly, it would be about as dense as the Earth's atmosphere

Which of the following is not a place where astronomers believe interstellar dust grains can form?

in HII regions

Astronomers must often know the distance to a star before they can fully understand its characteristics. Which of the following properties of a star typically requires a knowledge of distance before it can be determined?

luminosity

In figuring out the evolutionary tracks on the H-R diagram, astronomers

make model stars on a computer and then follow how their characteristics will change with time

Cosmic rays differ from other forms of interstellar matter by

moving much faster, at typical speeds of 90% the speed of light

The amount of interstellar matter present in our Galaxy is always changing. Which of the following processes is NOT a major contributor to that change?

some atoms of gas combine in dusty clouds to make more complex molecules

To establish the scale of the solar system, we need to measure the distance to one object orbiting the Sun. Venus was first used for this purpose, but in the 1930's astronomers organized an international campaign to measure the distance to:

the asteroid Eros

A star whose temperature is increasing but whose luminosity is roughly constant moves in what direction on the H-R diagram?

to the left

Astronomers identify the "birth" of a real star (as opposed to the activities of a protostar) with what activity in the star?

when nuclear fusion reactions begin inside its core

The luminosity class of a star tells an astronomer

whether the star is a supergiant, a giant, or a main-sequence star

Why is it so difficult for astronomers to see new stars in the process of birth?

you can't fool me, all of the reasons listed are correct