” Shaping the envelope of the asymptotic giant branch star W43A with a collimated fast jet” is an astronomical paper on a discovery made by ALMA. The Astrophysical Journal Letters published the on February 13, 2020. The Atacama Large Millimeter/submillimeter Array (ALMA) captured terrific images of W43A, a star that is in the early stages of becoming a bipolar nebula, a process that will take several thousand years.
The star ejects a rainbow look-alike bipolar jets that are affecting the environment. The jets seem to 60 years old and go from the blue color of the high-velocity jets from the star’s center to the green color of the low-velocity outflow and end in an orange cloud of dust.
W43A or IRAS 18450-0148 is a late-type star with a magnetically collimated jet (a protoplanetary nebula). A protoplanetary nebula is an astronomical object which is at the short-lived episode during a star’s rapid evolution between the late asymptotic giant branch phase and the subsequent planetary nebula phase. It emits strongly in infrared radiation and is a kind of reflection nebula.
W34A Star Is Transforming Into A Bipolar Nebula
W34A has two small bipolar jets with a velocity of 175 km per second. So far, it emitted diffuse spherical gas. The bipolar jets are just beginning to form, and they are less than 60 years. The star seems to be on its way to develop into a bipolar-shaped planetary nebula.
A bipolar nebula is a type of nebula characterized by two lobes either side of a central star. About 10-20% of planetary nebulae are bipolar. A bipolar jet comprises two continuous flows of gas from the poles of a star. Bipolar outflows may be associated with protostars (young, forming stars), or with evolved post-AGB stars (often in the form of bipolar nebulae). W34A fits in the second category.
The origin of these jets is the presence of a binary companion, where mass-transfer and accretion onto one of the stars lead to the creation of an accretion disk, from which matter is ejected. The presence of a magnetic field causes the eventual ejection and collimation of the matter, forming a bipolar outflow or jet.
W34A shows radio emissions from water molecules. This makes it one of the 15 water fountain objects identified so far in the Milky Way. We suppose that spots of these water emissions indicate the interface region between the jets and the surrounding material. We named them water fountains, and it could be a sign that the central source is a binarity system launching a new jet,” says Hiroshi Imai at Kagoshima University, Japan.
