Webb Telescope Counts 16.5 Million Stars in the Cigar Galaxy

NASA's James Webb Space Telescope has resolved millions of individual stars inside a furious starburst galaxy 12 million light-years from Earth.

A dense field of stars, illustrating the kind of stellar density Webb resolved in the Cigar Galaxy.

Astronomers have just released the most detailed stellar census ever taken of a galaxy outside our immediate cosmic neighborhood. Using 65 hours of observation time, the James Webb Space Telescope individually resolved roughly 16.5 million stars inside the Cigar Galaxy, also known as M82, a compact starburst galaxy located 12 million light-years from Earth.

A Galaxy Forging Stars at Breakneck Speed

M82 earned its nickname from its cigar-shaped silhouette when viewed edge-on from Earth. What makes it scientifically remarkable is the pace at which it manufactures new stars: astronomers estimate the galaxy forms stars roughly ten times faster than the Milky Way. That intense activity, called a starburst, is thought to have been triggered by a past gravitational interaction or merger with a neighboring galaxy, which compressed vast clouds of gas and ignited widespread star formation.

Starburst galaxies like M82 produce new stars far faster than typical spiral galaxies such as the Milky Way.

Why Infrared Vision Was Essential

Earlier observations, including those from the Hubble Space Telescope, struggled to see deep into M82 because thick clouds of dust and gas scatter and absorb visible light. Webb's Near-Infrared Camera, or NIRCam, instrument is built to detect longer infrared wavelengths that pass through that obscuring material largely unimpeded. By staring at the galaxy for 65 hours, Webb's team was able to pick out individual points of starlight that previous instruments recorded only as a single blurred glow, revealing the galaxy's underlying disk structure in unprecedented detail.

Sixteen Million Stars Is Still Just a Fraction

Researchers are careful to note that the 16.5 million stars Webb resolved represent only the brightest, most distinguishable points of light in the galaxy. The true stellar population of M82 is thought to number in the tens of billions, with the vast majority of stars too faint or too crowded together for even Webb's sharp optics to separate. Scientists describe the new image as a sample large enough to map how star formation is distributed across the galaxy's bar-shaped core and outer disk, rather than a complete inventory.

Webb's NIRCam instrument resolved individual stars that earlier telescopes recorded only as a diffuse glow.

A Short-Lived Cosmic Event, and What Comes Next

Astronomers estimate that M82's starburst phase, though dramatic by galactic standards, is a relatively brief event: it is expected to last only a few hundred million years in total before the galaxy's gas supply is exhausted or blown away by stellar winds and supernovae. Because nearby starburst galaxies are rare, M82 serves as a crucial nearby laboratory for understanding how galaxies behaved in the distant, early universe, when starburst activity is believed to have been far more common. Researchers plan to combine the new Webb data with existing Hubble observations to study how radiation and outflows from these young, massive stars shape the surrounding interstellar gas.

Ground- and space-based telescopes continue to combine data to build a fuller picture of distant galaxies.