Question

critical thinking

1. apply concepts. when we look at the night sky, are we seeing the universe exactly as it is?

how can scientists learn about stars from their light?
light takes time to travel through space. stars are so far away that their light takes millions of years to travel to earth! when scientists look through telescopes, it is as if they are looking back in time. the light we see from stars today was made millions of years ago. some stars that we see might have already burned out. however, we can still see them because their light is just reaching earth.

what can scientists learn from a stars light?
scientists use the light from stars to find out what the stars are made of. when you look at white light through a glass prism, you can see a rainbow of colors. this rainbow is called a spectrum (plural, spectra). millions of colors make up a spectrum, including red, orange, yellow, green, blue, indigo, and violet. scientists use a machine called a spectrograph to break up a stars light into a spectrum.
each element has a particular pattern of lines that appear in an emission spectrum. the emission spectrum shows scientists what elements are in the star.

take a look

1. compare which emission spectrum contains more colors of visible light, hydrogen or helium?

how do scientists classify stars?
stars can be classified in several ways. scientists classify stars most commonly by temperature and brightness.

temperature
in the past, scientists classified stars by the elements they contained. today, stars are classified by temperature. each group of stars is named with a letter of the alphabet. the table on the next page shows the features of different groups of stars.

Explanation:

1. We are not seeing the universe exactly as it is. Light from stars takes a long - time to reach Earth, so we see stars as they were in the past.
2. By comparing the given emission spectra images, helium's emission spectrum contains more colors of visible light as it has more lines.

Answer:

1. No, we are seeing the stars as they were in the past because of the time - delay of light.
2. Helium