Old and new stars paint a different picture of the Triangular Galaxy

A. Smercina/MJ Durbin/J. Dalcanton/BF Williams/University of Washington/NASA/ESA

This gigantic image of the Triangular Galaxy, also known as Messier 33, is a composite of 54 different views taken by Hubble’s Advanced Camera.

A team led by scientists from the University of Washington and the Center for Computational Astrophysics will present the results using the panchromatic survey at the 241st meeting of the American Astronomical Society in Seattle on January 11. Hubble Andromeda Extended Area of the Treasure Triangle (PHATTER). The effort gave astrophysicists their first in-depth look at the population. Star This forms a triangular constellation.

satellite constellation It is a close companion to the much larger Andromeda galaxy. The researchers found that it has two different structures depending on the age of the stars.

“The youngest and oldest stars in the Triangular Galaxy are arranged so differently that we can separate them using the Hubble Space Telescope’s dual-wavelength filter,” said Adam Smerzina, a postdoctoral researcher at the UW. “This is amazing. For many galaxies, such as the Milky Way and Andromeda, the stars are continuously distributed regardless of age. Not so for the Triad.”

A composite image of the Triangular Galaxy created by overlaying individual images taken by the Hubble Space Telescope as part of the PHATTER survey.

At about 61,000 light-years across, Triangulum is the third-largest galaxy in our Local Group, after Andromeda and our own Milky Way. In low-resolution images, it has a “flocculant” structure: numerous small spiral arms emanating from a well-defined nucleus.

For the PHATTER survey, the Hubble Space Telescope took hundreds of high-resolution images of different regions of the Triangulum galaxy in 108 orbits over a year. The team stitched together images of these small sections to create detailed, high-resolution data for triangulation. For the first time, it shows the individual stars of the galaxy in a large area at its center.

Thanks to Hubble’s filter circuitry, the researchers were also able to separate the stars by age. The distribution of the youngest massive stars, those less than a billion years old, roughly matches the “flocculent” shape for which the triangle is best known. But the older, redder stars are scattered in a very different pattern: two spiral arms radiating outward from the rectangular band at the center of the galaxy.

“This is a largely unknown and hidden feature of the Triangular Galaxy that is very difficult to see without this kind of detailed study,” Smerzina said.