2014. október 1.
Have you ever been lucky enough to see a flock of ducks getting ready to fly to warmer climates for the winter? Sailing gracefully as a group, from one fascinating pattern to the next? Normally these ducks are spotted soaring 1000 feet above the ground (about the height of the Eiffel Tower!)
But if we look up much, much higher, above Earth’s atmosphere and far beyond, we can see another flock —the Wild Duck Cluster.
Unless you have the eyes of a hawk, you’ll need a telescope or pair of binoculars to see this cluster of stars. Or a photograph, like this one! This beautiful picture shows the Wild Duck Cluster, as seen using a large telescope in Chile.
When seen from a distance the star cluster forms a spearhead shape, similar to a ducks flying in formation. (Although, when you zoom in as we have for this photograph, the cluster loses its shape).
Unfortunately, the stars inside this type of cluster are held together quite loosely and it doesn’t take much to scatter them. Sometimes it will be one rowdy member of the group that kicks stars out, other times they may be pulled out by the gravity of a star outside the cluster passing by.
Eventually, every star cluster will be pulled, pushed and distorted so much that all the stars fly far away and the cluster vanishes. But the length of time that a cluster survives varies wildly, from just a few million years to hundreds of millions of years.
Their survival depends on how full the cluster is. Tightly packed clusters with many stars live the longest, which is lucky for the Wild Duck Cluster, because it contains over 3000 stars!
The oldest example of this type of cluster thus far discovered is called Berkeley 17; it's a whopping 10 to 13 billion years old!