Stars | How They Change Over Time

Stars go through changes over the course of their existence. The rapidity and violence of those changes depends upon the mass of the star. Low mass stars are slow to change. High mass stars change quickly. Perhaps a case of Live Fast, Die Young.

This post is intended for those readers who have wondered what happens during the lifetime of a star. It is not intended to be an exhaustive description of the life-cycles of stars. Some of the numbers used here represent a range of values assumed for these events. Sources will differ some. There are many parts of star behavior that are complicated and not understood well by the experts. General concepts are presented here to make the processes more understandable.

All stars involve two types of processes that oppose each other. Gravity pulls the star components inward and tries to reduce the star’s volume. Nuclear fusion exerts outward forces and tries to increase the star’s volume. This interplay of opposing forces can create equilibrium. Change in strength of the processes will cause the star to either expand or contract in size. Since the mass of the star is quite constant, the inward pull of gravity is constant. The outward forces can change in strength as nuclear fusion processes change.

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Astro-Images | Pillars of Creation

I’ve created color composites from three grayscale images using the technique in this post. The colors assigned are not necessarily what the human eye would see, but are used to bring out details. Unless otherwise noted, all images used three original grayscales from the Hubble Legacy Archive. Visit the gallery of previous Astro-Images.

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NGC 6611 From ESO

The Eagle Nebula is about 7000 lt yrs distant in the constellation Serpens of the southern skies. The cluster of bright stars at the core was discovered by Jean-Philippe de Chéseaux in 1745-46. Images today show much more detail than Chéseaux was able to see. This image made from 3 greyscale components by the European Southern Observatory in 2009 shows those details. The very bright open cluster of stars barely right of center causes gases to glow and silhouettes of the dust regions. Those bright young stars formed 1-2 million yrs ago.

ESO | European Southern Observatory

 

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Pluto | Close-Up Views of Surface Details

New Horizons spacecraft coasted past Pluto on July 14, 2015. Twenty three minutes before closest approach, the spacecraft scanned the surface in high resolution from the northwest to the southeast limbs of Pluto. It gathered about three dozen sharp images each about 50 miles wide (80 km). Mission scientists have arranged those images into the mosaic below stretching more than 1000 miles long.

© 2016 The Johns Hopkins University Applied Physics Laboratory

 

The mosaic can be easily viewed with this movie. I suggest you watch full-screen more than once. Stop anytime and when new terrain appears highlighted by text at the left. It runs a bit too fast. You can slow down the speed by clicking the gear icon in the lower right after the movie starts.

 

You can also view the full high-resolution jpg image mosaic in higher quality than the movie by using this link. It is several megabytes so be patient if your connection is slow. It is worth it in my opinion.

Keep in mind the highest quality Hubble images of Pluto prior to this mission did not show much. This is a great age of discovery led by teams such as New Horizons.

Astro-Images | Four Nebulae

I’ve created color composites from three grayscale images using the technique in this post. The colors assigned are not necessarily what the human eye would see, but are used to bring out details. Unless otherwise noted, all images used three original grayscales from the Hubble Legacy Archive. Visit the gallery of previous Astro-Images.

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NGC 7009

The Saturn Nebula is in the constellation Aquarius. William Herschel found it 7 Sep 1782 using a telescope in his garden. The image he saw had a central bulge with narrow extensions on either side that made it look a bit like Saturn. Images today show more detail and make it look less like Saturn. The hot central star is emitting jets of debris to the upper left and lower right.

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Saturn Nebula

 

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Mercury Transit | In Case You Missed It

It was 100% cloudy and rainy all day for me. I had to watch online. Here is the complete 7 hrs condensed into about 17 sec. You might need to go full-screen to see Mercury. It is so tiny.

I am so glad to have the online resources available. Go to this SDO site for other video of the transit. Next Mercury transit is 11 Nov 2019.

Mercury | Rare Transit of the Sun

Mercury passes between the Sun and Earth during the day on 9 May 2016 allowing us to see it in silhouette for about 7 hours. It happens only 13 times per century. What is expected and how can it be viewed safely? Full details here for those knowledgeable in the technical bits. This NASA article is also very informative. For the rest who don’t feel technically savvy, follow me farther down below in this post.

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Astro-Images | Rectangle | Gem | Rings

I enjoy creating color images from three grayscale images. The post linked here will explain how to create color astronomical images. The colors assigned are not necessarily what the human eye would see, but are used to bring out details. Visit the gallery of previous Astro-Images. Unless otherwise noted, all images are made by me using three original grayscales from the Hubble Legacy Archive.

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NGC 6445

Can an exploding star create debris in the shape of a rectangular box? It appears that is what happened with the Red Rectangle nebula. It is found in the constellation Monoceros which is just to the left of Orion. The nebula was discovered in 1973 when scientists were using a rocket to search for infrared sources. The two stars at the center of the nebula were discovered in 1915.

NGC6445

 

Consider this model of the Red Rectangle. To make it, I put an image of a wine glass stem-to-stem with another and placed them horizontal. Two stars are in orbit where the stems join. One of the stars is nearing the end of its life cycle and is emitting large amounts of gases in two directions (left and right) along the axis of spin. The excited gases appear red. This model is not viewed exactly 90˚ to the axis. The actual image above is actually 90˚ to the axis of spin.

In the image above, there are variations in the cones emitted to the left and right. They are disruptions to the flow of gases from the source star caused by the other star in orbit around the source.

RectModel

 

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