Mostly Mute Monday: How young stars appear in old clusters
![](https://preprod.bigthink.com/wp-content/uploads/2015/12/1eZqK32igCO73RN3ZjCKzbQ.jpeg?w=480&h=270&crop=1)
These stars are too hot and blue for their age, and the leading theory just got a strike against it.
“Youth is the gift of nature, but age is a work of art.” –Stanislaw Jerzy Lec
If you want to know how old a star cluster is, all you have to do is measure the color and brightness of its members.
![](https://cdn-images-1.medium.com/max/800/0*RKqJ_-Pll38rw5-h.jpg)
The hottest, brightest and bluest stars burn through their fuel the fastest, and so as they disappear, you know your cluster is aging.
![](https://cdn-images-1.medium.com/max/800/0*OT4hCkrNTNPgpNNY.jpg)
In astronomy, we call this color-brightness relationship the Hertzsprung-Russell diagram, and the “turn-off point” tells you the cluster’s age.
![](https://cdn-images-1.medium.com/max/800/0*0veynedwE8CYbT4_.jpg)
But surprisingly, bluer, brighter, hotter stars often appear in these older clusters anyway!
![](https://cdn-images-1.medium.com/max/800/0*7wAy8X9Oxz5EF1iY.jpg)
Even in cases where there’s no evidence of a recent star-forming event, these blue straggler stars can frequently be found.
![](https://cdn-images-1.medium.com/max/800/0*pRRPhuC_O4_GrNKk.jpg)
For a long time, we thought the occasional merger of two low-mass stars gave rise to a heavier, blue star. But there’s an alternative.
![](https://cdn-images-1.medium.com/max/800/0*cgvGBKI-GyA6_sH2.jpg)
In binary star systems, a denser, heavier star can siphon mass off of its companion, stripping it into a white dwarf.
![](https://cdn-images-1.medium.com/max/800/0*cTI3kG2jeSeGptIX.jpg)
Recently, scientist Natalie Gosnell studied the old open cluster NGC 188. Out of 21 blue stragglers, 7 have white dwarf companions.
![](https://cdn-images-1.medium.com/max/800/0*QOZoYfWBwa8QkNnb.jpg)
Combined with an earlier study, this causes a complete rethink of blue stragglers.
![](https://cdn-images-1.medium.com/max/800/0*qrvEISkIl4ebREI_.jpeg)
Don’t be deceived: these young-looking stars are older than they appear!
Mostly Mute Monday tells the story of a single astronomical phenomenon or object in visuals, images, video and no more than 200 words.
Leave your comments on our forum, help Starts With A Bang! deliver more rewards on Patreon, and order our first book, Beyond The Galaxy, today!