Question

State three properties of any visible object in the universe that one can determine by spectroscopy

Answer 1

Spectroscopy in astronomy allows us to determine the composition, temperature, and motion of celestial objects.

Step-by-step explanation:

Spectroscopy is a powerful tool used in astronomy to study celestial objects. By analyzing the light emitted or absorbed by an object, we can determine several properties. Three properties that can be determined by spectroscopy are:

1. Composition: Spectroscopy can reveal the elements present in an object. Each element has a unique set of energy levels, so when the electrons in the atoms or molecules transition between energy levels, they emit or absorb light at specific wavelengths. By analyzing these wavelengths, astronomers can identify the elements present.
2. Temperature: Spectroscopy can provide information about the temperature of an object. The intensity of certain spectral lines varies with temperature. For example, the intensity of hydrogen spectral lines decreases as the temperature increases. By comparing the observed intensities with known temperature dependency, astronomers can estimate the temperature of the object.
3. Motion: Spectroscopy can also reveal the motion of an object. When an object is moving, the observed wavelengths of the spectral lines are shifted either towards the blue end (if moving towards us) or towards the red end (if moving away from us) of the spectrum. This shift is known as the Doppler effect and can be used to determine the speed and direction of motion.

Answer 2

1. Temperature.

2. Velocity.

3. Chemical composition.

Step-by-step explanation:

1. Temperature.

The effective temperature can be known by means of the Wien's displacement law

`T = (2.898x10^(-3) m. K)/(\lambda max)` (1)

Therefore, (
`\lambda_(max)`) is the maximum peak of emission in the continuum of the spectrum of the object (see the image below) and T is the temperature.

2. Velocity.

Spectral lines will be shifted to the blue part of the spectrum if the source of the observed light is moving toward the observer, or to the red part of the spectrum when is moving away from the observer (that is known as the Doppler effect).

Then, by using that shift in the spectral lines the velocity of the source can be determined.

`v = c(\Delta \lambda)/(\lambda_(0))` (2)

Where
`\Delta \lambda` is the wavelength shift,
`\lambda_(0)` is the wavelength at rest, v is the velocity of the source and c is the speed of light.

3. Chemical composition.

The absorption lines and emission lines give information of the chemical composition of the source, since those lines are produced when a photon coming from the source is absorbed by an electron (of an atom in the same source) and goes to a higher state, then when the electron comes back to a lower state it will emit a photon with the same energy of the difference between the two states. If the photon does not follow the same direction of the incident photon an absorption line will be created in the spectrum of the source.