Hubble’s N44 Superbubble Shows How Massive Stars Can Spark New Star Formation

NASA and ESA’s September 3 Hubble image of LHA 120-N44, usually called N44, is more than a striking nebula portrait. It captures the aftermath of feedback from massive stars: a vast, 210-by-140-light-year superbubble surrounded by dense gas and dust where another generation of stars is forming. N44 lies about 160,000 light-years away in the Large Magellanic Cloud, in the constellation Dorado. 1

What the central superbubble is

The dominant structure in N44 is a large central void bordered by a dense, dusty shell. Massive stars near its center pushed away their natal gas through powerful stellar winds and supernova explosions. Rather than simply dispersing the surrounding material, that feedback swept it up into the bright shell visible around the cavity. 1

This is why the region is called a superbubble: it is a large interstellar cavity shaped by the combined energy output of multiple massive stars, rather than a bubble created by one star alone.

Why the shell may be making new stars

As gas is piled into a shell, it can become denser and more likely to collapse under gravity. In N44, new stars are forming in that swept-up material, making the system a strong example of how one episode of star formation can influence the next. 1

Researchers have identified an age difference of up to roughly five million years between stars inside the superbubble and stars at its rim. That timing is consistent with a sequence in which an older central population cleared the cavity and compressed gas at the edge, followed by newer star formation in the shell. It is evidence for triggered star formation, but it does not establish that every young rim star formed through that exact mechanism. 1

A census of nearly half a million stars

The image data came from Hubble observing program 14689, led by Dimitrios Gouliermis. The survey cataloged nearly 500,000 stars in and around N44, including nearly 30,000 pre-main-sequence stars—young objects that have not yet begun fusing hydrogen into helium in their cores. 1

That large sample makes N44 particularly useful for comparing stars at different stages of development within a single connected complex. It also helps astronomers investigate the timing between the compression of cold gas and the emergence of young stars.

N44F: a smaller bubble with a different origin

N44 contains more than the central superbubble. Near the upper-right area of the Hubble image is N44F, a smaller bubble created by the stellar wind of a single hot, massive star. 1

The contrast is useful: N44F demonstrates how one powerful star can sculpt its local surroundings, while the much larger central cavity reflects the collective impact of a stellar cluster and its supernovae.

Why N44 is a valuable laboratory

N44 spans roughly 1,000 light-years and contains glowing hydrogen gas, dark dust lanes, massive stars, and stellar populations of different ages. It includes especially hot, intensely star-forming areas, allowing astronomers to study several phases of stellar evolution in one broad region. 1

The Large Magellanic Cloud also has a lower abundance of elements heavier than helium than the Milky Way. This low-metallicity setting resembles conditions in younger galaxies in the early universe, making N44 a nearby place to test how star formation and stellar feedback operate under those conditions. 1

The central lesson of the Hubble image is cyclical: massive stars can end one phase of a nebula’s life by clearing away gas, while simultaneously creating dense shells that may seed the next phase of star formation.