Astronomers have captured a remarkable view of a dying star’s remains being broken apart and mixed into the space between stars.
The discovery offers a rare look at one of the universe’s great recycling processes—the return of material from old stars that may eventually help form new stars, planets and other objects.
The discovery was made while scientists were observing the Helix Nebula, a famous planetary nebula about 650 light-years from Earth. The research, led by Yale University astronomer Pieter van Dokkum, was published in Nature.
The Helix Nebula formed when a Sun-like star reached the final stages of its life. The dying star expelled much of its outer material into space, leaving behind a small, dense stellar remnant known as a white dwarf.
The expelled gas created the nebula’s well-known bright ring.
But the new observations revealed something much farther from the center.
The scientists were actually using the Helix Nebula to calibrate a new telescope called MOTHRA, or the Modular Optical Telephoto Hyperspectral Robotic Array. The telescope is being built at the El Sauce Observatory in Chile and is designed to detect extremely faint gas in space.
Instead of simply getting a calibration image, the researchers discovered a network of previously overlooked structures in the faint outer regions of the nebula.
On the eastern side of the Helix Nebula, they identified 22 complete or partial structures known as “bow shocks.” A bow shock is similar to the curved wave that forms in front of a boat as it moves through water.
In this case, mostly invisible clumps of material expelled by the dying star are moving rapidly through the thin gas between stars. As these fragments crash into the surrounding gas, they create glowing, curved structures that astronomers can detect.
The shapes of these bow shocks provided an important clue about what happens to material after a star releases it.
Closer to the central star, the structures are large, thin and clearly defined. Farther away, they become smaller, fuzzier and increasingly broken apart. Researchers believe this pattern shows the stellar fragments gradually being destroyed as they travel through space.
The team estimates that an individual clump can remain intact for only about 10,000 years after it becomes exposed to the surrounding gas. Eventually, it is shredded and its material becomes mixed into interstellar space.
This process is an important part of the life cycle of matter in the universe. Material released by dying stars can later become part of new generations of stars and planets. Billions of years from now, our own Sun is expected to go through a similar transformation, returning much of its material to the galaxy.
The discovery may also demonstrate the potential of MOTHRA. When completed, the unusual telescope will use 1,140 telephoto lenses, along with specialized filters and powerful computing systems, to search for some of the faintest structures in the universe.
For astronomers, the Helix Nebula has now provided more than a beautiful picture. It has offered a rare opportunity to watch cosmic recycling actually happening.
Source: Yale.
