Most massive (not biggest) star discovered
The story:
Astronomers discovered a huge star in a nearby galaxy last week. R136a1, part of the Large Magellanic Cloud, is estimated to have a mass 265 times more than the sun and to shine around a million times more brightly.
Now, let’s clear up a bit of scientific jargon here as some people have got very upset over the fact that the star has been reported by some journalists as being the ‘biggest’ star ever to be discovered. It is, in fact, the most ‘massive’ as many stars have been discovered that have a larger diameter (see video weblink below) but R136a1 is the star with the biggest mass. How astronomers can calculate the mass of a star a mere 165,000 light years away though is beyond me.
Previously, astronomers didn’t think that they would find any stars more massive than the pistol star which is 150 times more massive than the Sun as it was thought that this was the upper limit of how massive stars could get. The star was discovered by using the Very Large Telescope in Chile (which can be referred to as big, massive or large without causing distress).
Teaching idea:
Most secondary school students find it difficult to comprehend just how massive objects in the Universe are (I once was asked by a 14 year-old student if the moon was bigger than the classroom). The video in the weblinks below shows how the sizes of several planets and stars compare with each other to give them a really good idea of just how big things can get. The biggest star shown here is VY Canis Majoris which has a radius around 1800-2100 times bigger than our Sun but it is not the most massive star. This is because it is a red supergiant, so is near the end of its life having shed most of its mass. (for comparison – R136a1 is thought to have a radious around 30 times bigger than the Sun).
This story will fit nicely into a lesson on stellar evolution. The area of the galaxy that R136a1 was discovered is called the Tarantula nebula. This could introduce the start of a star’s life cycle.
The star is thought to be middle-aged, much like our Sun. But, unlike our Sun is not going to last very long. Massive stars like R136a1 so not live very long lives and as they age they lose mass. It is thought that the star is around a million years old, and at the start of its life it could have been nearer 320 times more massive than the Sun. GCSE students who have studied how stars produce their energy could theorise why R136a1 has shrunk so significantly, and why VY Canis Majoris still holds the record for the biggest star but is not the most massive. they could also predict how they think R136a1 will end its live: Supernova and black hole perhaps?
Finally, the Very Large Telescope could be looked at as an example of a how telescopes can greatly improve our understanding of the universe.
These are some of the amazing images taken of the Tarantula nebula by the VLT. On the left is a visible-light image along with a zoomed-in visible-light image in the centre. The image on the right is taken with a near-infrared instrument. The bright cluster of stars on the far-right contains R136a1.
As you can see, these high-resolution images of objects so far away mean that the VLT will surely be used to uncover yet more secrets of the Universe.
Anything to add?
Whilst writing this post, it’s always a possibility that I missed some other great information or teaching ideas. Feel free to share your thoughts.
Weblinks
News-story about the discover of R136a1.
Great video that compares the sizes of the planets in the Solar System, our Sun and then some really big stars.
Information on the Very large Telecsope (VLT).
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