Composition and Motion of Stars

Articles “Radio Waves to Gamma Rays” and

I found an article about discovering a planet called Proxima b that astronomers found four light years away from us orbiting Proxima Centauri which is just a little red dwarf that happens to be the closest star to our sun. Apparently this spot seemed like a good place to look for their exoplanets and this is where they found what they were looking for. After the astronomers found the planet they were able to find a small wobble from exerting gravitational tugs on the star from the planet. This causes the star to also wobble around a center of mass. Also in the article the astronomers say that this would have not been possible without the capabilities of the Doppler effect. This is described as the change in frequency of a wave as an object moves toward or away from an observer. They were able to use this natural tool to gain the frequencies needed to prove there was a planet by that star. In years past they were unsuccessful but using the Doppler effect made this accomplishment happen. This article ties right into this unit on measuring through the Doppler effect, light, energy, composition, and motion of stars.

According to our in class lessons and backed by my article, we learned how we can discover the chemical composition, speed and direction of a star just by observing and studying its light. Light is something we live with on a daily basis. It shines from things such as light bulbs, candles, electronic devices, and our sun. Light has a large range represented by a scale that consists of types we can and can’t see called the Electromagnetic Spectrum. This includes different wavelengths (the distance between peaks on the scale) that are listed lower to higher frequencies such as radio waves, infrared, visible light, ultraviolet, x-rays, and gamma rays. Even though these frequencies (the number of times the waves move up and down) may be different between each one, the light always travels at the same speed.

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One of the laws we learned that goes along with energy and frequency is Planck’s law which describes the relationship between the two measurements. The formula for this law is E=h x v. E is for the energy, v is for frequency and h is for joules which is in fact the constant at 6.6 x 10 -34.

We also learned in class that light itself is not only just different wavelengths but is also made of particles called photons that can be counted individually and each holds its specific amount of energy. According to our book a photon is an individual particle of light, characterized by a wavelength and a frequency. The energy within this particle can in fact be measured through something called quantum. The last great area we covered in class and I read in the article for this conceptual objective, was the spectral shift in stars also known as the Doppler Effect and how to determine a stars temperature based on emanating wavelengths and group them. When classifying the star you will find that the cooler a star is the redder the light will be emanated and the hotter the star is the bluer the emanated light will be. The way that these spectral types are listed is by order of hottest to coolest with the letters O.B.A.F.G.K.M the counter parts that go along with these letters are numbers 9 the hottest down to 0 the coolest. By figuring out which spectral type a star fits into, you then can go on to find the chemical composition of the star. Stars that are further down the spectrum into the reds are not made of the same materials as higher energy stars that are in the blue area of the spectrum. Generally lower energy stars only have hydrogen and helium made up while the higher energy stars have mostly ionized metals like iron. This creates a good amount of difference between the two. Moving on to Doppler Effect this is the detecting of traveling a star does and finding its speed from the emanating light. We are able to tell if a star is moving away from us or towards us by the length of its wavelength. If it is shorter than the star is blue-shifted towards us and if the wavelength is longer then the star has red-shifted away from us. A great example of this that you can see and hear on Earth is when a train passes by on the tracks and blows its whistle. When the train is coming towards you (blue shift) the whistle sounds more high-pitched. Once it has passed you and moving away (red shift) the pitch gets lower and more drawn out.

Image result for doppler effect and light waves

According to the article the Doppler Effect also gives us a clue as to how fast or slow a star is moving and if that star is moving pretty quickly, it will go through a much more dramatic shift than the stars that are slower. If a star is moving faster than another star the effect will be that that fast stars wavelength will be longer than the slower star. This is similar to how meteorologists use their Doppler radar to detect storm clouds.

This unit taught me a lot about the different kinds of light and ways to measure it. I knew about most of the spectral types but I never knew exactly how the Doppler Effect worked till we learned this unit and I read this article that talked about it. It was definitely a great experience. I believe this unit will not only help with our next objective but also understanding exactly how we get our weather forecasts using the Doppler method which is useful in our everyday life. I thought this unit was interesting and can not wait to see what my next post will look like. This objective is in my top 5 for sure.



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