Astro Bob: Cosmic tarantula caught in NASA's Webb
A Webb's-eye view of newborn suns in one of the largest stellar nurseries known.
Stars are born in dense clouds of gas and dust that hide them from view in ordinary telescopes. NASA's James Webb Space Telescope doesn't have those limitations because it can image stars by the heat they radiate in infrared light. Infrared is "redder" than red light and invisible to the human eye. Mosquitos and pythons can sense parts of the infrared spectrum that assist in finding and tracking prey, including us.
The Orion Nebula is one of the closest of those star nurseries, but the largest and brightest across the entire Local Group of galaxies resides in the Large Magellanic Cloud, a dwarf companion galaxy of the Milky Way 161,000 light-years away in the constellation Dorado. Astronomers dubbed it the Tarantula Nebula because its glowing filaments resembled the furry legs of a tarantula spider.
Protostars nestled deep within its billows of gas and dust are still gathering mass by dint of their ever-increasing gravitational pull. The more mass, the more pull, and the larger they grow. Stars of all sizes are popping up here — everything from teeny, Jupiter-sized brown dwarfs to heavyweight supergiants like the behemoth R136a1 . With a mass around 200 suns and a diameter 35 times solar, it's the most massive star known.
Recently, astronomers focused three of Webb’s high-resolution infrared instruments on the Tarantula. Viewed with Webb’s Near-Infrared Camera , the spidery legs morph into a tarantula's burrow lined with its silk. Blistering radiation from a cluster of massive young stars, sparkling pale blue in the image, has hollowed out a dark central cavity.
Brighter, denser regions around the hollow have so far resisted erosion by powerful stellar winds common to young stars. The curlicues that appear to point back toward the cluster contain forming protostars, which will eventually emerge from their dusty cocoons and take their turn shaping the nebula.
When Webb switches to a longer infrared wavelength (deeper infrared light) the hot stars fade, and the cooler gas and dust glow even more brightly. Within the nebula, points of light indicate embedded protostars still gaining mass. Longer, mid-infrared wavelengths penetrate that dust, revealing a previously unseen cosmic environment.
One of the reasons astronomers are targeting the Tarantula Nebula is that its chemical composition is similar to the gigantic star-forming regions observed in distant galaxies when the cosmos was only 2-3 billion year old and at the pinnacle of new star creation.
While the Milky Way galaxy still has plenty of star-forming regions, it's not producing suns at the rate it did during its youth After all, it's 13.6 billion years old — give the poor galaxy a break! Nor do those star-forming clouds have the same chemical composition as the more ancient material around during that cosmic heyday. This makes the Tarantula the closest and easiest-to-study example of what was happening in the universe when stars crackled like fireworks.