On 3/13/2017 7:50 AM, Craig Markwardt wrote:
On Thursday, March 9, 2017 at 8:07:54 AM UTC-5, Yousuf Khan wrote:
One of the default assumptions about star clusters is that all of
the stars inside each of them are of nearly the same age as each
other. So a star cluster that is 10 billion years old, will have
stars that are all 10 billion years old. This is such a well
established astronomical rule, ...

It's more of an reasoned assumption than a rule. Given that there
are a only a handful of younger stars in the cluster that was
studied, it might be fairer to say that "a very tiny part of what we
know about star clusters might be wrong."

Well, they only studied the one cluster so far, and it took a lot of
detective work to figure out which ones were younger than the rest of
the group. They will now expand the finding out to more clusters, and
other groups will probably also join the search and find even more
within these clusters. It's a handful of stars right now, but it's only
now been discovered. More might come after more careful analysis, even
within this one cluster?

Yousuf Khan