Red, white and blue stars shine like a fluttering flare on a dark night in this new image from NASA’s Hubble Space Telescope. NASA released this image to celebrate America’s 250th anniversary, as the agency continues America’s legacy of exploration.

Located in the outer halo of our Milky Way galaxy, the globular cluster NGC 6426 is a spherical collection of stars bound together by their mutual gravity, one of 150 known globular clusters in our galaxy. These groups of stars are thought to form as a unit from the same collapsing gas cloud, and therefore the stars containing them are usually of similar ages. Stars in globular clusters tend to be old. At approximately 13 billion years old, NGC 6426 is one of the oldest globular clusters in the Milky Way and almost as old as the universe itself (13.7 billion years old).

In this image, blue indicates the shorter wavelengths of visible light, while red represents the longer wavelengths of visible light, as well as some near-infrared light. Colors in Hubble images are chosen based on standard image processing techniques to best represent the wavelengths of light passing through the filters used in the observation. Because the color and temperature of stars are directly related, we know that the blue stars in this image are hotter and the red stars are cooler.

The stars of NGC 6426 have low metallicity, meaning they have fewer elements heavier than hydrogen and helium. These conditions resemble those of the early universe, when matter was mainly helium and hydrogen and heavier elements were just beginning to form through nuclear fusion inside massive stars.

Researchers have found evidence of two chemically distinct populations of stars in NGC 6426, indicating that the slightly younger and more metallic stars were enriched with material from the explosive death of the cluster’s previous stars. Massive stars that explode as supernovae spew elements heavier than hydrogen and helium into the universe, seeding it with materials to build new stars and planets.

Hubble took this image as part of a study of globular clusters in the Milky Way’s halo aimed at determining their ages and shedding light on the formation and evolution of the galaxy. Over the past three decades in orbit, Hubble has fundamentally changed our understanding of the universe. Their discoveries are expanded upon and complemented by observations from other NASA missions, including the infrared-sensing James Webb Space Telescope and the Nancy Grace Roman Space Telescope, scheduled to launch in late summer.

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Media contact:

Claire Andreoli
from NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
claire.andreoli@nasa.gov