Why are red supergiant stars dancing

(ORDO NEWS) — It would be easier to create a 3D map of our galaxy if some of the stars were long enough that we could calculate their distances.

However, red supergiants are the quickest guys when it comes to pinpointing their exact location. This is because they seem to be dancing, which makes it difficult to determine their place in space.

This wobble is a feature, not a fault, of these massive old stars, and scientists want to understand its cause.

So, as with other complex objects in the galaxy, astronomers turned to computer models to find out why. In addition, they use position measurements taken by the Gaia mission to understand why red supergiants dance.

The red supergiant population shares several characteristics. These are stars whose mass is at least eight times the mass of the Sun – they are huge.

The diameter of a typical star is 700-1000 times larger than the sun. They also change their brightness, which (for some of them) may be due to dance-like vibrations.

So we have a population of stars that have expanded so much that they end up with very low surface gravity.

Because of this, their convective cells (structures that carry heat from the inside to the surface) become quite large. One cell covers up to 20-30% of the star’s radius. This actually “interrupts” its brightness.

Convection not only transports heat from the inside out, but also helps the star eject material into nearby space. And we are not talking about small pieces of gas and plasma.

A red supergiant can throw a billion times more mass into space than the Sun. All of these actions make the star look frothy, as if its surface is boiling insanely. Essentially, this causes the position of the star to dance in the sky.

Astronomers want to trace the total mass that these aging stars are throwing out into space. They also measure the speed of the stellar wind and calculate the geometry of the cloud of stellar matter that envelops the red supergiant.

One way scientists use to determine the exact position of a star is through its “photocenter.” This is the center of the star’s light.

If the star’s brightness changes (for whatever reason), the photocenter shifts. It will not coincide with the barycenter (this is the common center of gravity between a star and the rest of its system.

It is a component when measuring distances). In combination with the action of huge convective cells, the star seems to be dancing in space.

The problem of red supergiant dynamics attracted Andrea Chiavassa (Lagrange Laboratory and Max Planck Institute for Astrophysics).

She, along with astronomer Rolf Kudricki (University Observatory Munich) and a scientific team, created a simulation of the boiling surfaces and brightness variability of red supergiants.

“Synthetic maps show extremely heterogeneous surfaces, where the largest structures develop on time scales of months or even years, while smaller structures develop over weeks,” Chiavassa said. “This means that the position of the star is expected to change over time.”

The team compared their model to stars in the Chi Persei cluster. This cluster was measured by the Gaia satellite, so the position of most of its stars is very accurate. All but red supergiants.

This change in the observed position provides a solution for understanding the position shift of the red supergiants.

But, in turn, it creates difficulties in measuring the exact distances to many of these stars. The current model also provides clues for the evolution of these objects.

But knowing what makes the stars dance opens the way to solving the problem of calculating their distances.

Future models will help astronomers refine these distances and gain more insight into what happens to stars as they age.


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