NASA’s Hubble Spies Stellar Sparkler for July 4th

Red, white, and blue stars glitter like a sparkler being waved on a dark night in this new image from NASA’s Hubble Space Telescope. NASA released this image to celebrate the United States’ 250th anniversary, as the agency carries forward America’s legacy of exploration.

Located in the outer halo of our Milky Way galaxy, 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 cloud of gas, and thus the stars in them typically have similar ages. The stars in globular clusters tend to be ancient. At approximately 13 billion years old, NGC 6426 is one of the Milky Way’s oldest globular clusters and almost as old as the universe itself (13.7 billion years).

In this image, blue indicates the shorter wavelengths that are visible light, while red depicts 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 that pass 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, which means they have fewer elements that are heavier than hydrogen and helium. These conditions resemble those of the early universe, when matter was mostly helium and hydrogen and heavier elements were just beginning to form via nuclear fusion within massive stars.

Researchers have found evidence for 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 deaths of the cluster’s earlier stars. Massive stars that explode as supernovae fling 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 intended to determine their ages and shed 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. Its discoveries are expanded upon and complemented by observations from other NASA missions like the infrared-detecting James Webb Space Telescope and the Nancy Grace Roman Space Telescope, scheduled to launch in late summer.

Media Contact:

Claire AndreoliNASA's Goddard Space Flight Center, Greenbelt, MDclaire.andreoli@nasa.gov

Full text from nasa.gov (public domain).