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Researchers discover thin void on stellar family portrait



The Gaia mission of the European Space Agency has created the richest star chart in our galaxy to this day. Credit: Satellite: Gaia Copyright: ESA / Gaia / DPAC

On the Hertzsprung-Russell diagram (HRD), the most basic of all maps of stellar astronomy, a thin gap was discovered that provides new information about the interior, according to a study , conducted by astronomers at Georgia State University, identifies low mass stars in the Milky Way galaxy.

Just as a graphic can be created by people of different heights and weights, astronomers compare stars based on their brightness and temperature. The HRD is a "family portrait" of the stars in the galaxy, where stars like the Sun, Altair, Alpha Centauri, Beteigeuze, the Northern Star Polaris and Sirius can be compared. The newly discovered gap cuts diagonally across the HRD and indicates where a significant internal change in the structures of stars occurs. The gap outlines where stars of large and mostly convective with a thin layer of radiation become too small and completely convective.

Radiation and convection are two ways to transfer energy from a star to its surface. Radiation transfers energy through space, and convection is the transfer of energy from one place to another through the movement of fluid.

The researchers estimate that stars above the gap contain more than about one-third of the mass of the sun below have less mass. Since different types of stars have different masses, this feature shows where different types of inner structures are on the HRD. The gap is in the middle of the region of the "red dwarf" stars, which are much smaller and cooler than the sun, but make up three out of four stars in the solar neighborhood. The findings are published in the journal The Astrophysical Journal Letters .

"We were quite excited to see this result, and it gives us new insights into the structures and evolution of stars," Dr. Wei-Chun Jao, lead author of the study and astrophysicist at the Department of Physics and Astronomy at Georgia State.

In 201

3, the European Space Agency (ESA) launched the space probe Gaia to perform a star census in the US Milky Way and to create a three-dimensional map. In April 2018, the ESA released results of this mission, revealing an unprecedented map of more than a billion stars in the galaxy, a 10,000-fold increase in the number of stars at exact ranges. The research team led by Georgia State planned nearly 250,000 of the nearest stars in the Gaia data on the HRD to uncover the gap. Georgia State researchers have been studying the distance to neighboring stars for years, allowing them to interpret the results and to pinpoint this tiny gap.

The team is now working to find out why the gap exists. Using results from a theoretical computer model that simulates activity within the stars, the gap appears to be caused by a slight reduction when a star is consistently convective.

To read the study, visit http: // iopscience iop. org / Article / 10. 3847 / 2041-8213 / aacdf6 / meta.


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