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Pre-planetary nebula formation captured around the star LL-Pegasi

A team of astronomers has recently captured a stunning image of an unusual pre-planetary nebula, known as IRAS 23166+1655, using the Advanced Camera for Surveys on the NASA/ESA Hubble Space Telescope. The nebula is located around the star LL Pegasi (also known as AFGL 3068) in the constellation of Pegasus (the Winged Horse).

The striking picture shows what appears to be a thin spiral pattern of astonishing regularity winding around the star, which is itself hidden behind thick dust. According to the researchers, the spiral pattern suggests a regular periodic origin for the nebula’s shape.

The material forming the spiral is moving outwards a speed of about 50,000 km/hour. By combining this speed with the distance between layers, we calculate that the shells are each separated by about 800 years.

Binary system believed to cause the spiral formation

The astronomers believe that the spiral arises because LL Pegasi is a binary system, with the star that is losing material and a companion star orbiting each other.

The spacing between layers in the spiral is expected to directly reflect the orbital period of the binary, which is indeed estimated to be also about 800 years.

The creation and shaping of planetary nebulae is an exciting area of stellar evolution. Stars with masses from about half that of the Sun up to about eight times that of the Sun do not explode as supernovae at the ends of their lives.

Instead, a more regal end awaits them as their outer layers of gas are shed and drift into space, creating striking and intricate structures that to Earth-bound observers often look like dramatic watercolor paintings.

LL Pegasi: The enigmatic star behind the spiral nebula

As mentioned previously, LL Pegasi is the star at the center of the remarkable spiral nebula IRAS 23166+1655. This enigmatic star has captured the attention of astronomers worldwide, as it plays a crucial role in the formation of the stunning geometric structure that surrounds it.

Cool, pulsating giant

LL Pegasi is a type of star known as an asymptotic giant branch (AGB) star. These stars are in the late stages of their lives and have expanded to become cool, pulsating giants.

As they pulsate, they shed their outer layers of gas and dust into space, creating the building blocks for the intricate nebulae that will eventually surround them.

Binary connection

One of the most intriguing aspects of LL Pegasi is its suspected binary nature. Astronomers believe that the star is part of a binary system, where two stars orbit each other.

The presence of a companion star is thought to be the key factor in shaping the spectacular spiral structure of IRAS 23166+1655. As the stars orbit each other, they create a regular pattern of material ejection, leading to the formation of the evenly spaced shells that make up the spiral.

Evolution of LL Pegasi

As LL Pegasi continues to evolve, it will eventually shed its outer layers completely, exposing its hot core. This will mark the beginning of a new chapter in its life as a planetary nebula.

The material ejected during its AGB phase will be ionized by the intense radiation from the exposed core, creating a glowing shell of gas that will expand into space.

The spiral structure created during the binary interaction phase will likely persist, adding to the beauty and complexity of the resulting planetary nebula.

Central star yet to emerge from dust cocoon

IRAS 23166+1655 is just starting the process of creating a planetary nebula, and the central star has yet to emerge from the cocoon of enveloping dust.

The researchers used images from the Wide Field Channel of the Advanced Camera for Surveys on Hubble to create this picture. Images through a yellow filter (F606W, colored blue) were combined with images through a near-infrared filter (F804W, colored red).

The exposure times were 11 minutes and 22 minutes respectively, and the field of view spans about 80 arcseconds.

Ethereal jewel in LL-Pegasi

In summary, the discovery of the stunning spiral formation in the pre-planetary nebula IRAS 23166+1655 by the Hubble Space Telescope has opened a new window into the captivating realm of stellar evolution.

As astronomers continue to study this remarkable object, they will undoubtedly unravel more secrets about the intricate processes that shape the cosmos.

This celestial masterpiece serves as a testament to the power of human curiosity and the technological marvels that allow us to explore the vast expanse of the universe.

With each new finding, we inch closer to understanding the fundamental laws that govern the birth, life, and death of stars, and the fascinating structures they leave behind.


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