Some stars produce dust. But unlike what’s under your TV cabinet, this dust plays a big role in the galaxy’s total brightness. In a new study, scientists used long-term observational data to see how interstellar dust correlates with star brightness.
Asymptotic giant branch (AGB) stars are usually slightly older and larger than the Sun. They are also major producers of cosmic dust, especially those dubbed “dusty AGB stars”. Because AGB stars are inflated red giants, their outer atmospheres are cold, and condensation and radiation pressure push dust outward.
Interstellar dust is a key factor in the formation of solids, including planets. Despite studies investigating how this dust is produced, the process is poorly understood. Some AGB stars are thought to control dust formation by expansion and contraction of their outer layers, a phenomenon called stellar pulsation that causes changes in the star’s luminosity.
Mid-infrared (IR) monitoring is required to investigate the relationship between stellar pulsations and dust formation. IR radiation is emitted by all objects that emit heat, so almost all celestial bodies emit some IR. The wavelength at which an object radiates most strongly depends on its temperature. In other words, there are IR wavelengths that are better suited for studying specific objects. Mid-infrared operates in the temperature range 10 to 140 Kelvin (-263 °C/-442 °F to -133 °C/-208 °F) and can detect planets, comets, asteroids and, importantly, starlight. dust warmed by
Researchers at the University of Tokyo used data from two infrared space telescopes used on the AKARI and WISE satellites to gain insight into the relationship between AGB star dust and its brightness. .
“We study stars, and infrared light from stars is an important source of information that helps unlock the secrets of stars,” said Kengo Tachibana, lead author of the study. “Until recently, most IR data came from very short-term surveys due to the lack of sophisticated dedicated platforms. investigation became possible. “
AKARI, which ended its operation in 2011, was Japan’s first satellite dedicated to infrared observation, surveying the sky using near-, mid-, and far-infrared rays. The Wide-Field Infrared Survey Explorer (WISE) was originally NASA’s IR space telescope launched in December 2009, entered hibernation mode in February 2011, and launched the Near-Earth Object Wide-Field Infrared Survey Explorer (Neo-Wise) in 2013. .
By combining the mid-infrared data collected by AKARI and WISE, researchers were able to generate long-term observational data. This study is the largest on the mid-infrared variability, a measure of the amount of dust produced by stars.
The researchers found a correlation between the light intensity of dusty AGB stars and variations in dust production.
“Thanks to long-term IR observations, we found that the light from the dusty AGB changes,” said Tachibana. “We also found that the spherical shells of dust produced and subsequently expelled by these stars have dust concentrations that change with changes in the star’s luminosity.” Of the many AGBs, the dust concentration around them agrees regardless of their fluctuation period, so we are confident that they are related.”
The study is just the beginning for researchers looking to investigate the mechanisms of interstellar dust formation using IR observations obtained at the University of Tokyo’s Atacama Observatory in Chile.
The study was published in a journal Publications of the Astronomical Society of Japan.
Source: University of Tokyo
