5 Million Years into the Milky Way

The article, “Can you imagine the sky in five million years?,” explains that since July 2014, ESA’s Gaia mission has been charting positions of stars in our galaxy and hope to create a 3-dimensional map of it. With such precise stellar positions comes something else: stellar motions. Thousands of years is but an eye blink in the lifetime of a galaxy, and the notion that stars don’t change positions is false. The stars do move in bulk as they rotate around the center of the Milky Way, but sometimes zip off in random directions. The closer a star is to us, the more it will appear to move. This perspective effect is also how Gaia measures stellar positions so accurately, using a technique called parallax that causes nearby stars to shift against the background as Earth orbits the Sun. ESA has released a video of 2,057,050 stars that is a fast forwarded trip through time that ends with the sky as it would appear from Earth in 5 million years. As a result, constellations will have changed, there will be new stars, and other stars will have lived out their lives.

Our objective was to be able to explain how astronomers study the properties of stars including: distance, size, and mass. This article relates to the objective because it discusses stellar parallax. The most direct way to measure a star’s distance is with stellar parallax, which is the small annual shifts in a star’s apparent position caused by Earth’s motion around the Sun. The article explains that the closer a star is to us, the more it will appear to move. This relates to what we did in class when we held our finger up to our face and closed one eye at a time and then did the same thing with our finger farther away. When our finger was closer it appeared to moved back and forth more than it did when it was farther away. We can calculate a star’s distance if we know the precise amount of the star’s annual shift due to parallax. This means measuring the angle which we call the star’s parallax angle. Based on the angles we drew in the lecture tutorial, “The Parsec,” we noticed that this angle would be much smaller if the star were further away, concluding that more distant stars have smaller parallax angles. By definition, the distance to an object with a parallax angle of 1 arcsecond is 1 parsec, which is equivalent to 3.26 light years. The formula d= 1/p is the formula for a star’s distance, where d is the star’s distance in parsecs and p is the parallax angle in arcseconds.

I enjoyed this article a lot because it had a lot of good information and it was very interesting as well. It gave just enough of a preview about parallax for the average reader to get an understanding of what the article is talking about. I never thought about the fact that the stars would appear very different millions of years from now, but it makes sense that they would. I wonder if any of the constellations we have now would be recognizable.


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