- 4282 - DISTANCE TO STARS? “Asteroseismology” is the study of stellar oscillations, to accurately measure the distance of stars. The countless bright spots in the nighttime sky all seem to be stars. But in fact, some of those spots are actually planets, or distant suns, or even entire galaxies located billions of light years away. Just what you're looking at depends on how far it is from Earth.
------------------------- 4282 - DISTANCE TO STARS?
- That's why
measuring the exact distance to celestial objects is such an important goal for
astronomers using asteroseismology. The
European Space Agency (ESA) launched the “Gaia mission” 10 years ago. Data
collected by the Gaia satellite are opening up a window into the near universe,
providing astronomic measurements as position, and distance from the Earth and movement for
nearly two billion stars.
-
- Gaia increased by a
factor of 10,000 the number of stars whose parallaxes are measured thanks to a
massive gain in accuracy. Scientists
use parallaxes to calculate the distance to stars. This method involves
measuring parallax angles, with the help of the satellite, through a form of
triangulation between Gaia's location in space, the sun and the star in
question. The farther away a star, the more difficult the measurement because
parallax angle gets smaller the larger the distance.
-
- Despite the
resounding success of Gaia, the measurement of parallax is complex, and there
remain small systematic effects that must be checked and corrected in order for
Gaia parallaxes to reach their full potential. Through calculations performed
on more than 12,000 oscillating red giant stars accuracy improved with the
biggest sample size and most accurate measurements to date.
-
- In the same way
that geologists study the Earth's structure using earthquakes, astronomers use
asteroseismology, and specifically stars' vibrations and oscillations, to glean
information about their physical properties. Stellar oscillations are measured
as tiny variations in light intensity and translated into sound waves, giving
rise to a frequency spectrum of these oscillations.
-
- The frequency
spectrum lets us determine how far away a star is, enabling us to obtain
astero-seismic parallaxes. Individual
sound waves propagate inside stars like the sun. Some propagate along the
surface layers, while others go right through the center of the star.
-
- Turning sounds
into distance measurements starts with a simple fact that the speed with which
sound waves propagate across space depends on the temperature and density of
the star's interior.
-
- By analyzing the
frequency spectrum of stellar oscillations, astronomers can estimate the size
of a star, much like you can identify the size of a musical instrument by the
kind of sound it makes.
-
- Having thus
calculated a star's size, the astronomers then determined its luminosity and
compared this figure to the luminosity perceived here on Earth. They coupled
this information with temperature and chemical-composition readings obtained
from spectroscopy and ran these data through analyses to calculate the distance
to the star. Finally, the astronomers compared the parallaxes obtained in this
process with those reported by Gaia in order to check the accuracy of the
satellite's measurements.
-
- Upcoming space
missions like TESS and PLATO intended to detect and survey exoplanets will
employ asteroseismology and deliver the required datasets across increasingly
large regions of the sky.
-
-
December 18, 2023
DISTANCE TO
STARS? 4279
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Thursday, December 21, 2023 ---------------------------------
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