LL Pegasi (AFGL 3068) is a

Mira variable Mira variables (named for the prototype star Mira) are a class of pulsating stars characterized by very red colours, pulsation periods longer than 100 days, and amplitudes greater than one magnitude in infrared and 2.5 magnitude at visual wavelen ...

star surrounded by a pinwheel-shaped nebula, IRAS 23166+1655, thought to be a preplanetary nebula. It is a

binary system A binary system is a system of two astronomical bodies which are close enough that their gravitational attraction causes them to orbit each other around a barycenter ''(also see animated examples)''. More restrictive definitions require that thi ...

that includes an extreme

carbon star A carbon star (C-type star) is typically an asymptotic giant branch star, a luminous red giant, whose atmosphere contains more carbon than oxygen. The two elements combine in the upper layers of the star, forming carbon monoxide, which consumes mos ...

. The pair is hidden by the

dust cloud Fugitive dust is an environmental air quality term for very small particles suspended in the air, primarily mineral dust that is sourced from the soil of Earth's pedosphere. A significant volume of fugitive dust that is visible from a distance i ...

ejected from the carbon star and is only visible in

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

light.

Variability

LL Pegasi is obscured at visual wavelengths, but is strongly variable in brightness at

wavelengths. It is classified as a Mira variable and has a period of about 696 days.

Nebula

The

nebula A nebula ('cloud' or 'fog' in Latin; pl. nebulae, nebulæ or nebulas) is a distinct luminescent part of interstellar medium, which can consist of ionized, neutral or molecular hydrogen and also cosmic dust. Nebulae are often star-forming regio ...

displays an unusual

Archimedean spiral The Archimedean spiral (also known as the arithmetic spiral) is a spiral named after the 3rd-century BC Greek mathematician Archimedes. It is the locus corresponding to the locations over time of a point moving away from a fixed point with a con ...

shape. The shape is thought to be formed through the interaction between the stellar companion and the carbon star, as has been seen in other

binary Binary may refer to: Science and technology Mathematics * Binary number, a representation of numbers using only two digits (0 and 1) * Binary function, a function that takes two arguments * Binary operation, a mathematical operation that t ...

systems, although not with such a precise geometric form. The distance between the spiral arms and their rate of expansion is consistent with estimates of the pair's 810 year orbital period based on their apparent angular separation.

Gallery

3D view of LL Pegasi.webm, Observed structure surrounding the binary star system. Pre-planetary nebula, IRAS 23166+1655.jpg,

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...

image of IRAS 23166+1655, taken in the near-infrared. The bright object to the right is a star much closer to Earth. It was used as a

guide star In astronomy, a guide star is a reference star used to accurately maintain the tracking by a telescope of a celestial body, whose apparent motion through the sky is primarily due to Earth's rotation. Accurate telescope pointing and tracking i ...

for

adaptive optics Adaptive optics (AO) is a technology used to improve the performance of optical systems by reducing the effect of incoming wavefront distortions by deforming a mirror in order to compensate for the distortion. It is used in astronomical tele ...

corrections that allowed the

Keck II The W. M. Keck Observatory is an astronomical observatory with two telescopes at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes have aperture primary mirrors, and when comp ...

telescope to resolve the LL Pegasi binary pair.

References

External links

3D view of LL PegasiCelestial spiral with a twistAn Extraordinary Celestial SpiralCelestial spiral goes viral
APOD {{DEFAULTSORT:LL Pegasi Protoplanetary nebulae IRAS catalogue objects Pegasi, LL Pegasus (constellation) Carbon stars Mira variables J23191260+1711331 TIC objects

Variability

Nebula

Gallery

See also

References

External links