We like to think that our Sun is an ordinary yellow dwarf star, just one of billions of solar type stars in our Milky Way Galaxy. But only in the last few decades have astronomers been able to do comparative asteroseismology of stars much like our own. Asteroseismology, the study of seismic stellar oscillations, is a necessary key to understanding our Sun and potentially billions of other solar systems within the galaxy.
Later this decade, the European Space Agency’s PLATO mission will observe hundreds of thousands of stars much like ours. PLATO, the PLAnetary Transits and Oscillation of stars mission, is charged with finding an Earth analog, but its measurements of stellar brightnesses over time will help theorists better understand stars that harbor planets like ours.
During a recent visit to Italy’s Catania Astrophysical Observatory, on the island of Sicily, I spoke with two researchers who are eagerly awaiting data that PLATO will provide. I asked them both why understanding stellar physics of solar type stars is important.
Stars are the basic bricks of our galaxy, Enrico Corsaro, a staff scientist at Catania Astrophysical Observatory and a PLATO science team member, told me at the observatory. If we want a better understanding of our galaxy, we first need to understand stars that look like the Sun, he says. And if we want a better understanding of whether our solar system is unique or not, we first need to understand the whole planetary system, says Corsaro.
PLATO Will Offer A New Understanding Of The Galaxy
Among other things, PLATO will significantly improve our understanding of internal dynamical processes in solar-type stars, Sylvain Breton, a postdoctoral researcher at the Catania Astrophysical Observatory and a PLATO science team member, told me at the observatory. And it will characterize with great accuracy the masses, radii and ages of solar-type stars, especially those hosting planets, he says.
PLATO will house the largest combined digital camera ever flown in space, says ESA. And it will receive light from 26 small telescopes all mounted on a single satellite platform, ESA notes.
During its nominal four-year mission, which likely will be extended to eight years, PLATO will have an extremely wide field of view covering a total area of the sky of approximately 2,250 degrees. That’s some 2000 times that of a full moon.
How important are observations of the Sun in interpreting asteroseismology?
They have been crucial; the Sun was our primary laboratory for testing and understanding variability in stellar luminosity, says Breton. By refining the models, we can apply that to stars like the Sun, he says. And if we can very precisely measure the age of the stars, then we can also measure the ages of the planets in a similar way, says Breton.
Our main goals are to improve our understanding of how stars work, how stars are constituted in the interior and how they evolve over time, says Corsaro.
To characterize exoplanets, I strongly believe that we really need to know the stars, says Corsaro.
Stars Before Planets
To understand the story of a planet, first, we have to get a good understanding of the star, says Breton. You want to monitor the luminosity variation of the star for the longest time possible, he says.
Oscillations and fluctuations in the level of the light from the star are subject to variations over time, says Corsaro. This tells us something about how the composition of the star’s interior, he says.
The main characteristic of the star that we are going to look at is the convective envelope, which is roughly between 10 to 40 percent of the star’s total radius, says Breton. At the star’s core, nuclear reactions that fuse hydrogen into helium produce energy, and over long timescales, what is produced at the core is transported to its surface, says Breton.
By analyzing how a star’s acoustic waves propagate on its surface, researchers can learn much about its interior.
Is there something special about our Sun?
There is a plethora of stars that have the same properties as our Sun.
But just due to our star’s proximity, we know the Sun in a way that we will never be able to know any other star, says Corsaro. Maybe a hundred years from now, that will change, he says.
