New Cepheid variable discoveries on the far side of the Galaxy


Source material from Scientific American: Astronomers have found five Cepheids (yellow dots at top) on the other side of the Galaxy. Credit: Spiral map: NASA/JPL-Caltech/R. Hurt, SSC-Caltech (base image); Ariel Weiss (Cepheid positions)

The Cepheids’ location initially suggested they had come from the nearby Sagittarius Dwarf Galaxy, which the Milky Way’s gravity is tearing apart. “We were quite surprised to find that these [stars] didn’t have the right velocities for that,” says Michael Feast, an astronomer at the University of Cape Town. Using the Southern African Large Telescope (SALT) the astronomers measured the stars’ Doppler shifts at infrared wavelengths, which penetrate dust in the galaxy’s disk. The velocities derived from the Doppler shifts indicated that all five Cepheids belong to our galaxy. The astronomers report their discovery in the May 15 issue of Nature (Scientific American is part of Nature Publishing Group).

[The newly discovered stars] serve as outstanding yardsticks, a feat which will divulge secrets about the Milky Way’s terra incognita. “It’s a beautiful piece of classic astronomy,” says Leo Blitz, an astronomer at the University of California, Berkeley, who was not involved in the discovery.

This picture of the nearby galaxy NGC 6744 was taken with the Wide Field Imager on the MPG/ESO 2.2-metre telescope at La Silla. The large spiral galaxy is similar to the Milky Way, making this image look like a picture postcard of our own galaxy sent from extragalactic space. Credit: ESO


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