Tools Used in Astronomy

Electromagnetic Spectrum

The complete range of all electromagnetic radiation in the universe.

Frequency

Number of wave cycles passing a point per second, measured in Hertz (Hz).

Wavelength

Distance between two consecutive wave peaks, measured in meters.

Relationship Between Frequency, Wavelength, and Energy

Higher frequency leads to shorter wavelength and higher energy, while lower frequency leads to longer wavelength and lower energy.

Visible Light

The part of the electromagnetic spectrum detectable by human eyes, with different wavelengths corresponding to different colors.

Chromatic Aberration

Different wavelengths bend differently through lenses, causing colored edges around objects.

Refracting Telescope

Uses lenses to collect, focus, and magnify light.

Reflecting Telescope

Uses mirrors to gather and redirect light, invented by Isaac Newton.

Inverse Square Law

Light intensity decreases with distance, represented by the formula I ∝ 1/d².

Light-Gathering Power

Ability of a telescope to collect light, larger objective diameter allows more light collection.

Resolving Power

Ability to distinguish fine details or separate close objects, larger diameter leads to better resolution.

Magnifying Power

Ratio between focal lengths of a telescope, M = fo/fe.

Observatories

Facilities containing telescopes and astronomical instruments used for observation.

Spectroscopy

Study of spectra to determine composition, temperature, motion, and physical properties.

Continuous Spectrum

Produced by dense hot objects, contains all wavelengths continuously.

Emission Spectrum

Bright lines on a dark background produced by hot low-density gases.

Absorption Spectrum

Dark lines on a bright background produced when continuous light passes through cooler gas.

Kirchhoff’s Laws

Three laws describing how black bodies and gases emit and absorb radiation.

Black Body

Ideal object that absorbs and re-emits all radiation.

Wien’s Law

Relates temperature and peak wavelength with the formula λmaxT = 2.898 × 10−3 m·K.

Doppler Effect

Change in observed wavelength due to the motion of an object.

Redshift

Increase in wavelength observed when an object is moving away.

Blueshift

Decrease in wavelength observed when an object is moving toward the observer.

Spectroscopy and Composition

Used to determine chemical composition, element abundance, and stellar atmospheres through unique spectral lines of each element.