Emission Spectrum and Absorption Spectroscopy

The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to an atom or molecule making a transition from a high energy state to a lower energy state.

For example, when an electron of Hydrogen transitions to a energy level of n = 3 to the base level of n = 2, it emits photons, which can be recorded as the emission spectrum.

Emission is the process by a higher energy particle converts to a lower one through emission of a photon, resulting in the production of light.

The emission spectra is produced when the electrons of the atom are excited and can change it's energy level. This produces a photon.

The emission spectrum allows us to understand the sources chemical composition, temperature, density, mass, distance, luminosity, and relative motion. These spectrum samples consists of absorption lines of celestial objects with emission spectra.

Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation such as visible light which radiates from stars and galaxies. Astronomical spectroscopy uses Doppler shift measurements as well, to determine a objects age and distance. Spectrum samples are also known to show spread shifts of celestial objects.

Absorption spectroscopy refers to spectroscopic techniques that measure the absorption of radiation. Absorption spectroscopy uses frequency or wavelength as a function. 

Absorption spectroscopy works when a sample absorbs energy (such as photons) from the radiating field and the intensity of the absorption varies as a function of frequency. This variation is the absorption spectrum. 

Absorption lines are Typically classified by the nature of the quantum mechanical change induced in the molecule or atom, 

Absorption spectrum samples are completely different from the emission spectrum, due to the different intensity pattern. Emission spectrum samples

Early Universe and Re-ionization

After the Big Bang, the known universe went through many phases or epochs. These epochs were characterized through certain actions that were occurring in the universe. Such actions included light characteristics, atomic and subatomic patterns and actions.

During the creation of the universe, early atoms formed, and the universe consisted of roughly 75% hydrogen and 25% helium. For about a billion years, the gas in the universe was going through two major phase changes. In the first phase change, gas atoms went through combination of electrons and protons to form neutral atoms. This rate of recombination was higher than the re-ionization rate. The Universe continued to become transparent as more electrons and protons combined to form neutral hydrogen. This was known as the dark ages, due to the absence of stars and their emission of light as well as the transparency of the universe. The universe was also dominated by mysterious "dark matter" which is still unable to be fully understood by modern Astrophysicists today. The second phase is when objects started to condense in the early universe, these objects had enough energy to ionize neutral hydrogen. These objects included early stars and galaxies. This is when the Universe went through the re-ionization epoch.

In order to understand the early universe we must understand the basic characteristics of early galaxies. In the beginning of the age of re-ionization, early stars began to mass and clump in clouds of dust, forming protogalactic clouds. In these clouds, gravity caused gas and dust to collapse and form stars. These young stars burned out quickly as gravity continued to collapse the clouds. As the clouds collapsed, they began to form galaxies, as gravity cased other nearby clouds to merge and collide forming larger galaxies. This plays an important part in the evolution of galaxies.

Some question many astrophysicists have is that when and how did re ionization occur? What sources caused re-ionization? What are the first galaxies? These questions also intrigue me, as I plan to look deeper and learn more about the early universe. 

In terms of myself, I really want to know more about the characteristics of these early galaxies, as well as understanding how these early galaxies could have affected the re-ionization of the universe.