Extraordinary Spiral

Credit: ESA/NASA & R. Sahai

Some­times we view NASA Hub­ble Space Tele­scope images and see things we just don’t believe. This strik­ing spi­ral is thought to be cre­ated by mate­r­ial spin­ning out of LL Pegasi.

LL Pegasi, like most stars in the galaxy, is a binary star; two stars orbit­ing each other. One of the stars is los­ing mate­r­ial, while another star orbits it. From our lucky van­tage point on Earth, we are look­ing at the star from above. So we see the expand­ing pin­wheel spi­ral pat­tern look­ing like a spin­ning water sprin­kler. The reg­u­lar spac­ing between lay­ers in the spiral

Astronomers believe that LL Pegasi is in the first stages of form­ing a plan­e­tary neb­ula. Plan­e­tary neb­u­lae have noth­ing to do with plan­ets. Planet hunters of the 17th and 18th cen­turies saw many objects in their tele­scopes that resem­bled the gas giants Jupiter, Sat­urn and Uranus. We now know that these objects are far out­side the solar sys­tem. Plan­e­tary neb­u­lae form dur­ing the final stages of life for stars like our Sun. Once they run out of hydro­gen fuel, they start to burn heav­ier ele­ments, such as helium. They swell, engulf­ing their inner plan­ets, and the outer lay­ers are puffed off into space. Huge expand­ing bub­bles and rings of mate­r­ial form the plan­e­tary neb­u­lae we see. Radi­a­tion from the hot and dead core of the star causes atoms within the cloud to glow like a neon sign.

The mate­r­ial mak­ing up the spi­ral is mov­ing away from the star at about 50,000 kilo­me­ters per hour, or 30,000 miles per hour. While we can see the mate­r­ial being spewed from the cen­tral star, a thick cocoon of dust blocks it from our view. Know­ing the speed the mate­r­ial is being ejected, astronomers can mea­sure the reg­u­lar spac­ing between the spi­rals. They find that the orbital period of the com­pan­ion star and the dis­tance between the spi­rals is about 800 years.

LL Pegasi, or AFGL 3068, is found more than 3,000 light-years away from Earth toward the con­stel­la­tion of Pega­sus, the Winged Horse.