Science

Astronomers can determine the chemical composition of stars by observing which of the following?

• Speed of rotation of the star at its equator
• Wavelengths of light emitted by the star
• Time the star takes to move through the night sky
• The season of the year in which the star is seen

The wavelengths of light emitted by a star can provide information on all of the following characteristics of a star EXCEPT -

• temperature of the star
• direction of movement of the star
• chemical composition of the star
• number of planets orbiting the star

A nebula is a cloud of dust in space that does not emit any light. How can astronomers use spectral analysis to determine the composition of a nebula?

• Sending high energy light waves to the nebula that reflect back to Earth
• Analyzing the light from stars behind the nebula which passes through.
• Using the composition of cloud in Earth's atmosphere as a model
• Collecting samples of a nebula that happen to reach our solar system

The image provided is a star chart. It shows background stars that are very distant from Earth (smaller circles), as well as four stars that appear to shift positions when seen from Earth at different times of the year. Which of the four stars, based on the observations shown in the star chart, is closest to Earth? Which of the four stars, based on the observations shown in the star chart, is closest to Earth?

• Star W
• Star X
• Star Y
• Star Z

The spectrum for visible wavelengths emitted by Star X is compared to the emission spectra of four different elements. According to the spectral analysis data, which element is present in Star X?

• Hydrogen
• Carbon
• Neon
• Magnesium

All observable objects outside our galaxy, when viewed from Earth, have their spectra shifted to slightly longer wavelengths. Astronomers have concluded that this is evidence that all objects in the universe are -

• hotter than our Sun.
• moving away from each other.
• older than our solar system.
• absorbing radiation from stars.

Which of the following characteristics of elements is used by astronomers to determine the chemical composition of distant stars? All elements -

• are composed of smaller particles, such as protons.
• can be found on the Periodic Table of Elements.
• emit certain wavelengths of light when heated.
• are able to combine with others to form compounds.

The diagram provided gives information that relates the strength of the spectral lines of various elements, which may be detected in a star and used to predict the surface temperature of the star. Which of the following would be a reasonable prediction for the surface temperature of a star whose emission spectrum had strong silicon (Si) and magnesium (Mg) lines?

• 20,000 degrees Kelvin
• 30,000 degrees Kelvin
• 5,000 degrees Kelvin
• 2,500 degrees Kelvin

By comparing the actual brightness of a star to its apparent brightness astronomers can determine a star's 

• distance from earth
• diameter in kilometers
• age compared to the Sun
• mass to the nearest kilogram

The image provided is a star chart. It shows background stars that are very distant from Earth (smaller circles), as well as four stars that appear to shift positions when seen from Earth at different times of the year. Which of the four stars, based on these observations, is farthest from Earth?

• Star X
• Star W
• Star Y
• Star Z