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Astronomers from the University of Warsaw discovered a Cepheid with a record pulsation period in the Milky Way

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Astronomers from the University of Warsaw Astronomical Observatory have identified the brightest and probably the youngest Cepheid known in the Milky Way. As highlighted, it has a record long pulsation period among stars of this type in our galaxy, and this discovery shows that the Milky Way is no exception in this respect.

Classical Cepheids are variable stars, pulsating giants that regularly change their brightness. They have found extremely important astrophysical applications. In 1924, American astronomer Edwin Hubble used the period-luminosity relationship fulfilled by Cepheids to prove that the Universe consists of an innumerable number of galaxies and not, as previously thought, only the Milky Way. A few years later, Cepheids observed in neighboring galaxies helped Hubble discover the fact that the Universe was expanding, which soon led to the formulation of the Big Bang theory.

Today, classical Cepheids are widely used to measure intergalactic distances and to study the structure of galaxies. Among other things, Cepheids are the basis for the most accurate measurement of the Hubble constant, a quantity that determines the rate of expansion of the Universe.

Astronomers from the University of Warsaw discovered a Cepheid

The newly identified star received the catalog name OGLE-GD-CEP-1884. It pulsates with a period of 78.14 days, which is almost 10 days longer than the pulsation period of the previous record holder, the Cepheid S Vulpeculae – the Astronomical Observatory of the University of Warsaw said in a statement on Thursday.

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The discovery was made by scientists working as part of the OGLE project conducted at the Observatory. The star was selected by Professor Igor Soszyński, a world leader in research on variable stars.

“So far, not a single ULPC-type object has been known in our galaxy, although most of the studied galaxies contain several Cepheids of this type. The star OGLE-GD-CEP-1884, although it is over 25,000 times brighter than the Sun, has not been correctly classified before. as a Cepheid because it is located behind a thick layer of interstellar material that absorbs light coming from the object, especially in the blue part of the spectrum,” we read in the release. Many years of photometric observations of this star, conducted in red light by the OGLE team, combined with radial velocity measurements made by the Gaia space telescope, allowed us to clearly demonstrate that it is a classical Cepheid.

The brightest and perhaps the youngest

“The discovery of this object indicates that the Milky Way is not unique among other galaxies in terms of the occurrence of long-period Cepheids, and the current lack of observations of this type of stars in our galaxy is probably due to the fact that ULPCs are obscured by dense clouds of interstellar dust,” the scientists conclude. OGLE-GD-CEP-1884 is not only the brightest, but also probably the youngest known classical Cepheid in the Milky Way. The age of this star was estimated at 22 million years.

According to the researchers, by using the period-luminosity relationship for Cepheids, it was possible to measure the distance to OGLE-GD-CEP-1884 and mark its location on the map of our galaxy. This star is located 14,500 light-years away in the Carboniferous Spiral Arm among other relatively young classical Cepheids. The discovery of OGLE-GD-CEP-1884 will contribute to a more accurate calibration of the period-luminosity relationship for Cepheids and to a better understanding of the evolution of massive stars.

The newly discovered star OGLE-GD-CEP-1884 belongs to a small group of Cepheids with extremely long pulsation periods. ultra-long-period Cepheids, abbreviated as ULPC). A feature of this type of objects – as explained by astronomers from the University of Warsaw – is their high brightness, which is used to measure the distance to galaxies located up to 300 million light years from us.

Other successes of Warsaw astronomers

The OGLE research team, led by prof. Andrzej Udalski, has extensive experience in discovering and studying pulsating stars. Approximately half of all classical Cepheids currently known in the Milky Way were discovered by astronomers from the University of Warsaw – recalled in the release.

A few years ago, researchers led by prof. Dorota Skowron published a three-dimensional map of our galaxy, obtained on the basis of the spatial distribution of Cepheids discovered by the OGLE team. This map clearly showed that the disk of the Milky Way is not flat, but bends into an S-shape.

Main photo source: Shutterstock

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