Image de l’amas globulaire Liller 1 prise par le télescope spatial Hubble. Crédit : ESA/Hubble & ; NASA, F. Ferraro
Les tons rouges de l’amas globulaire Liller 1 sont partiellement masqués sur cette image par un éparpillement dense d’étoiles d’un bleu intense. En fait, c’est grâce à la caméra à grand champ 3 (WFC3) de Hubble que nous pouvons voir Liller 1 si clairement sur cette image, car la WFC3 est sensible aux longueurs d’onde de la lumière que l’œil humain ne peut pas voir.
Liller 1 se trouve à seulement 30 000 années-lumière de la Terre, ce qui en fait une voisine relativement proche en termes astronomiques, mais elle se trouve dans la Milky Way’s ‘bulge’, the dense and dusty region at our galaxy’s center. Because of that, Liller 1 is heavily obscured from view by interstellar dust, which scatters visible light (particularly blue light) very effectively. Fortunately, some infrared and red visible light is able to pass through these dusty regions. Hubble’s WFC3 is sensitive to both visible and near-infrared (infrared that is close to the visible) wavelengths, allowing us to see through the obscuring clouds of dust, and providing this magnificent view of Liller 1.
Liller 1 is a particularly interesting globular cluster, because unlike most of its kind, it contains a mix of very young and very old stars. Globular clusters typically house only old stars, some nearly as old as the Universe itself. Liller1 instead contains at least two distinct stellar populations with remarkably different ages: the oldest one is 12 billion years old and the youngest component is just 1-2 billion years old. This led astronomers to conclude that this stellar system was able to form stars over an extraordinarily long period of time.
