02 Observing the Universe Free Online FlashCards

What can the light from a distant object reveal?

Its brightness, direction, wavelength, and changes over time reveal what distant objects are made of, how hot they are, and how they move.

What is the electromagnetic spectrum order from longest to shortest wavelength?

Radio, microwave, infrared, visible, ultraviolet, X-ray, and gamma-ray, from longest wavelength and lowest photon energy to shortest wavelength and highest energy.

What can infrared observations reveal?

Infrared can reveal relatively cool objects and radiation from dust.

Why does a telescope need a large collecting area?

A larger collecting area captures more photons, helping astronomers study faint objects.

What is one benefit and one limitation of interferometry?

Interferometry can improve resolution by combining observations from separated telescopes, but it does not provide the collecting area of a single dish spanning the same distance.

How do optical and infrared telescopes commonly focus light?

Optical and infrared telescopes commonly use mirrors to focus light.

How does a CCD turn light into digital data?

A CCD converts incoming photons into electrical charges in pixels; electronics read the charges and turn them into digital measurements.

What does a light curve show, and what might a repeating dip indicate?

A light curve records how a source’s brightness changes over time. A repeating dip can indicate that an orbiting planet passes in front of a star.

How do continuous, emission, and absorption spectra differ?

A continuous spectrum spans a broad range of wavelengths; an emission spectrum has bright lines; an absorption spectrum has dark lines where light was absorbed.

How can spectral lines reveal an object's chemical composition?

Each element and molecule produces a characteristic pattern of spectral lines, allowing astronomers to identify chemical composition.

What can a Doppler shift in spectral lines reveal?

A shift of spectral lines toward longer or shorter wavelengths can reveal motion along the line of sight through the Doppler effect.

How does Earth's atmosphere affect astronomical observations?

Earth’s atmosphere blocks or absorbs much incoming radiation. Most visible light and some radio waves reach the ground, while many ultraviolet, X-ray, and gamma-ray wavelengths do not.