readyvef.blogg.se - Absorption spectra example

Greater the density of a star, the broader its absorption lines become.UV-Visible Spectroscopy Visible and Ultraviolet SpectroscopyĪn obvious difference between certain compounds is their color. The combined effect of these changes results in broader absorption lines. When the energy state decreases, the absorption line becomes longer in wavelength (less energy). When the energy state of an orbit increases, the absorption line becomes shorter in wavelength (more energy). These collisions result in electrostatic interaction between orbits of different atoms, leading to changes in the energy level of affect orbits. In higher density stars, the increased gas pressure produces more rapid collision between atoms. Width of absorption spectral lines also reveal information about the density of stars.ĭensity and pressure, at the surface of a star can also broaden spectral lines, but the intensity varies across the line in different way from the effect of rotation. The combined effect of these three phenomena results in broadened absorption lines in the stellar spectra. Wave emitted from the ‘middle’ of a start (region that has no relative rotation to an observer on Earth) has no change in wavelength.Wave emitted from the side of a star that is rotating away from us has longer wavelength (red-shifted).Wave emitted from the side of a star that is rotating towards us has shorter wavelength (blue-shifted).This effect can also be used to determine the rotational motion of stars. When stars move towards us, spectral lines of certain elements would be shifted towards shorter wavelengths (blue-shift) compared with a reference.hydrogen would be shifted towards longer wavelengths (red-shift) compared with a reference. When stars move away from us, spectral lines of certain elements e.g.The shifting effect is apparent when stellar spectra are compared with absorption spectra obtained by exciting elements on Earth.

The movement of stars, whether towards or away from Earth, is demonstrated by red and blue shift effects in their spectra. The following three spectra are for a hydrogen atom. Red and blue shifts observed in stellar spectra are caused by the Doppler’s Effect.

If the emitter or source of wave is moving away from the observe, the resultant wave has longer wavelength and lower frequency.

If the emitter or source of wave is moving towards the observer, the resultant wave has shorter wavelength and greater frequency.

The wavelength or frequency of a wave is influenced by the wave’s relatively velocity to the observer.

As such, the relative position and number of absorption lines can be compared to those of elements on Earth to identify the exact elemental composition of the star. As a result, the pattern of absorption lines of every star's spectrum is unique. Stars are composed of different elements in the form of atoms and ions. The absorption spectral lines represent the energy that has been absorbed by these electrons. This occurs when the energy matches exactly the excitation energy of electrons in the ground state of these elements. When light is emitted by the star, some of its energy absorbed by atoms in the outer layers of its atmosphere. Stellar absorption lines are caused by atoms present in gaseous layers of stars. However, knowledge will be covered and required in Module 8. For reference only, in-depth knowledge is not required for Module 7. Table: stars vary in colour, surface temperature and elemental composition.

Stars with shorter peak wavelengths have higher surface temperatures. Wien’s displacement law quantitatively describes this relationship: We can use this information to compare the relative surface temperature between stars. The peak wavelength refers to the wavelength with the highest intensity. Each wavelength of radiation has a different intensity. The spectra of stars consist of a wide range of wavelengths. This is referred to as the absorption spectrum or stellar spectrum.

Instead of seeing a continuous spectrum, the stellar spectra of the Sun contain absent wavelengths (absorption lines) within the spectrum. For example, the Sun emits white light that can be captured and observed on a spectrometer. Stars emit radiation which includes visible light (400-700 nm).