Oh Little Star, I Know What You Are!

In an article from space.com, a few moths ago there was a very odd pairing in the sky of the Orion constellation. Two stars within this cluster of “related” stars show contrasting characteristics; For these stars within the same constellation, it seems natural to assume that they are similar in nature, but the universe has something else in store. Scientists discovered that in fact, these stars are in very different periods of their lifetimes and roughly only have the association with the constellation in common. This got me thinking about how scientists discover these characteristics and are able to compare and contrast stars from each other without physically receiving star matter.

Luckily, in recent lecture, we have learned that astronomer’s use light in order to measure chemical compositions, speed, and direction of an astronomical object’s motion through analyzing spectra and doppler shifts. First off, light is emitted from stars and can be measured by analyzing the wavelengths given off by that particular light. This analysis is called spectroscopy. Stars give off a continuous spectrum of light within their core, meaning they give off every color of the spectrum. However, when we observe their spectra through either an emissions or absorption line spectrum, we see that there are in fact lines that come up that emphasize specific colors on the spectrum. These lines give way to specific data that determine the chemical compositions of stars. You see, although light from stars is continuous at the core, the stars’ atmospheres contain a layer of gas through which the light must pass through in order to reach the camera that is studying the spectra. This is how the bands on emission and absorption line spectrum come to be. Scientists study these bands to determine the chemical composition of stars. Different gases cause for different spectral lines to be present, ultimately determining what a specific star is made of.Image result for spectroscopyWhen it comes to measuring speed and direction of a star, scientists also use spectroscopy. In a Lecture-Tutorial on the doppler shift, we observed that light emitted by an object appears to change its wavelength. Due to its motion toward or away from the observer, a light source that is coming closer to the observer seems to have smaller wavelengths, a light source moving away from an observer seems to have larger wavelengths, and a light that is moving side-to-side or is stationary shows no change in spectra. The movement away from an observer is defined as being red-shifted because the color red emits the largest wavelength on the visible light spectrum, while a light that is moving towards an observer is defined as blue-shifted because blue light emits the smallest wavelength on the visible light spectrum. Therefore, scientists compare multiple spectra from the same star over the course of time to determine how the star is moving. In conjunction, the rate at how abruptly these spectral lines change determines the speed and direction of the star. If at first the spectral lines show to be red-shifted, but upon next analysis appear to be all the way on the blue-shifted side, it can be determined that the star is moving towards you very quickly. Alternately, when observing a different star, the spectral lines only appear to move a few millimeters over, then that star is moving much slower.

Learning about about spectra and spectral lines helped pave my way to understanding many more physical attributes to stars besides just being limited to speed, direction, and composition. Knowing this crucial instrument broadens my horizons in astronomy because spectroscopy can be used to measure other characteristics that will be discussed in later conceptual objectives.

Source: space.com


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