Hubble tracks M30's stars to investigate their past
· BehindLines newsroom
The portrait of the Messier 30 cluster published on 5 November brings together several Hubble observing campaigns. Beyond the image itself, repeated visits to the same region help compare stellar populations and their movements. NASA presents this as a way to read galactic history using data collected at different times.
M30 lies around 27,500 light years away in the constellation Capricornus. It is a globular cluster, an approximately spherical concentration of stars. Such groups are valuable witnesses to the Milky Way's past.
Observations that complement one another
An initial campaign studied many clusters in red and near infrared light using the ACS camera. Another added observations at bluer wavelengths with the WFC3 camera. These different filters help distinguish stellar populations and investigate particular objects, including stars known as blue stragglers.
A later campaign repeated observations to measure changes in position over a period of around 15 years. ESA/Hubble explains that the telescope's longevity and its ability to distinguish very fine details make this comparison possible. The new portrait combines these contributions rather than representing a single recent exposure.
Clues to the galaxy's assembly
A cluster's chemistry and movements can shed light on its origins. M30 follows an orbit opposite to the galaxy's direction of rotation, a clue consistent with an ancient capture by the Milky Way. That possibility remains an interpretation. The image alone does not definitively establish where the cluster came from.
For readers, the main lesson concerns the method: observing a familiar object again can produce information that was unavailable on the first visit. Publication of a portrait in November therefore means neither the discovery of a new cluster nor that all the data used were acquired at the same time.