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A team of astronomers used asteroseismology, or the study of stellar oscillations, to accurately measure the distance of stars from Earth. They examined thousands of stars and confirmed
A team of astronomers used asteroseismology, or the study of stellar oscillations, to accurately measure the distance of stars from Earth. They examined thousands of stars and confirmed the measurements taken during Gaia’s mission to study the nearby universe.
To most of us, the countless bright dots in the night sky look like stars. But in reality, some of these points are actually planets, distant suns, or even entire galaxies billions of light-years away. What you look at depends on how far away from Earth it is. This is why precisely measuring the distance to celestial objects is such an important goal for astronomers and one of the biggest challenges they currently face.
The European Space Agency (ESA) launched the Gaia mission ten years ago with this in mind. Data collected by the Gaia satellite provides a window into the nearby universe, providing astronomical measurements such as the position, distance from Earth, and motion of nearly two billion stars.
The Standard Candles and Distances research group at EPFL, led by Professor Richard Anderson, aims to measure the current expansion of the universe and sees Gaia as a valuable tool. “Gaia has increased the number of stars whose parallaxes have been measured by a factor of 10,000, a significant gain in accuracy compared to its predecessor, ESA’s Hipparcos mission,” he says. Today, scientists use parallaxes to calculate the distance to stars. This method involves measuring parallax angles with a satellite using the form of triangulation between Gaia’s position in space, the Sun, and the star in question. The further away the star is, the more difficult it is to measure as parallax becomes smaller as distance increases.
Despite Gaia’s stunning success, measuring parallax is challenging, and there are small systematic effects that need to be controlled and corrected for Gaia’s parallaxes to reach their full potential. This is what scientists from EPFL and the University of Bologna in Italy are working on; More than 12,000 oscillating red giants* were counted, the largest sample size and most precise measurements to date.
“We quantified Gaia’s errors by comparing satellite-derived parallaxes with parallaxes of the same stars that we determined using asteroseismology,” says Sania Khan, a scientist at the Anderson Research Group and lead author of the study published today in the journal Astronomy & Astrophysics. . .
Just as geologists study the structure of the Earth through earthquakes, astronomers use asteroseismology to learn about the physical properties of stars, specifically the wobbles and wobbles of stars. Stellar oscillations are measured as small fluctuations in light intensity and converted into sound waves, creating the frequency spectrum of these oscillations.
“The frequency spectrum allows us to determine how far away the star is and obtain asteroseismic parallaxes,” says Hahn. “In our study, we listened to the ‘music’ of many stars, some as far as 15,000 light-years away!”
To convert sounds into distance measurements, the research team started with a simple fact. The speed at which sound waves travel through space depends on the temperature and density of the star’s interior. “By analyzing the frequency spectrum of stars’ oscillations, we can estimate the size of the star, just as you can determine the size of a musical instrument by the sound it makes – think of the difference in pitch between a violin and a cello,” says Professor at the Department of Physics and Astronomy at the University of Bologna and the third author of the study. Written by Andrea Milio.
By calculating the size of the star in this way, astronomers determined the brightness of the star and compared this figure with the brightness experienced on Earth. They combined this information with measurements of temperature and chemical composition obtained through spectroscopy and put this data through a complex analysis to calculate the distance to the star. Finally, astronomers compared the parallaxes obtained in this process with those reported by Gaia to verify the accuracy of the satellite measurements.
“Asteroseismology is the only way to test the accuracy of Gaia’s parallax across the entire sky, that is, for both low-density and high-density stars,” says Anderson. As Khan stated, the future of this sector is bright:
“Future space missions such as TESS and PLATO, designed to detect and study exoplanets, will use asteroseismology and deliver the necessary data sets to larger regions of the sky. So methods like ours will play a critical role in improving parallax measurements of Gaia, which will help us determine our place in the universe.” “and will benefit many subfields of astronomy and astrophysics.”
Source: Port Altele
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