Astronomers have discovered 208 RR Lyrae variable stars in our galaxy

(ORDO NEWS) — Astronomers have discovered more than 200 distant RR Lyrae variables in the Milky Way’s stellar halo. The most distant of them is more than a million light years from Earth.

The characteristic pulsations and brightness of RR Lyrae variables make them excellent standard candles for measuring galactic distances. These new observations have allowed researchers to trace the outer limits of the Milky Way’s halo.

“This study rethinks what makes up the outer limits of our galaxy,” said Raja Guhathakurta, a professor at the University of California. “Our galaxy and Andromeda are so large that there is almost no space between these two galaxies.”

Guhatakurta explained that the Milky Way’s stellar halo is much larger than the disk, which is about 100,000 light years in diameter. The solar system is located in one of the spiral arms of the disk.

In the middle of the disk is a central bulge, and around it is a halo that contains the oldest stars in the galaxy and extends hundreds of thousands of light-years in all directions.

In previous studies, scientists have calculated using simulations that the stellar halo should extend about 300 kiloparsecs, or 1 million light-years, from the center of the galaxy. The 208 RR Lyrae variables were located at a distance of about 20 to 320 kiloparsecs.

“We were able to use these variable stars as reliable indicators to determine distances,” said Yuting Feng, who led the study. “Our observations confirm the theoretical estimates of halo size, so this is an important result.”

The findings are based on data from the Next Generation Virgo Cluster Survey (NGVS), a program that uses the Canadian-French-Hawaiian Telescope (CFHT) to study the Virgo Cluster, which lies far beyond the Milky Way.

The Virgo Cluster is a large cluster of galaxies that includes the giant elliptical galaxy M87.

“In order to get a deeper image of M87 and its surrounding galaxies, the telescope also captured foreground stars in the same field, so the data we used is sort of a by-product of this study,” Feng explained.

According to Guhatakurta, the excellent quality of the NGVS data has enabled the team to obtain the most reliable and accurate characterization of RR Lyrae stars.

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