Hubble Reveals a 'Superbubble' Carved by Young Stars in a Nearby Galaxy

The European Space Agency (ESA) and NASA's Hubble Space Telescope have released a new Picture of the Month showing the nebula LHA 120-N44, or N44 for short — a giant cloud of gas and dust where new stars often form. N44 sits in the Large Magellanic Cloud (LMC), the largest of the small galaxies orbiting the Milky Way, about 160,000 light-years away in the constellation Dorado.

N44's appearance is dominated by two features: a vast central void and a surrounding shell of dense, dusty gas. The void is a 'superbubble' — a cavity carved out by young, massive stars — spanning roughly 210 by 140 light-years. Through powerful stellar winds and supernova explosions, the central stars expelled much of their birth gas, and that gas piled up into the shell, where new stars are now forming.

N44 has become a key site for astronomers timing star formation, from the collapse of cold gas clouds into dense knots to the moment nuclear fusion ignites inside a newborn star. Using Hubble, researchers catalogued nearly 500,000 stars in and around the N44 cluster, including nearly 30,000 pre-main-sequence stars — young stars yet to begin fusing hydrogen into helium. Finding so many faint young stars in this crowded field required Hubble's high sensitivity and fine resolution.

The gas shell glows because ultraviolet radiation from massive stars energises it, revealing distinct features that astronomer Karl Henize catalogued in the 1950s. One, a smaller bubble called N44F near the image's upper-right corner, was blown by the intense stellar winds of a single hot, massive star. A previous Hubble close-up of N44F showed those winds and radiation sculpting the bubble and carving pillars of dusty gas.

The observations come from Hubble programme #14689, with Gouliermis as principal investigator, aimed at probing N44's stars that have not yet begun fusing hydrogen into heavier elements — to determine how long star formation takes and what masses newborn stars typically reach.