Saturday, April 11, 2020

Weird Stars

Astronomers have finally found something they have spent decades searching for: a teardrop-shaped star that pulsates on only one side. Citizen scientists helped the discovery team find the strangely lopsided star, which is known as HD74423, in data gathered by NASA's Transiting Exoplanet Survey Satellite (TESS). The star is about 1.7 times the mass of Earth's sun, and scientists determined that HD74423's weird pulsing is caused by a second, smaller star.

"I've been looking for a star like this for nearly 40 years, and now we have finally found one," study co-author Don Kurtz, an astronomer at the University of Central Lancashire in the U.K., said in a statement released by the University of Sydney, where Kurtz is temporarily based. (Read more.)

From Live Science:
Something's up with the North Star. People have watched the North Star for centuries. The bright star, also known as Polaris, is almost directly above Earth's North Pole and serves as a landmark in the sky for travelers without a compass. It's also Earth's closest cepheid, a type of star that pulses regularly in diameter and brightness. And Polaris is part of a binary system; it's got a dimmer sister, known as Polaris B, that we can watch circling it from Earth.

"However, as we learn more, it is becoming clear that we understand less" about Polaris, wrote the authors of a new paper on the famous star.

The problem with Polaris is that no one can agree on how big or distant it is. Astrophysicists have a few ways to calculate the mass, age and distance of a star like Polaris. One method is a stellar evolution model, said new study co-author Hilding R. Neilson, an astrophysicist at the University of Toronto. Researchers can study the brightness, color and rate of pulsation of the star and use that data to figure out how big and bright it is and what stage of life it's in. Once those details are worked out, Neilson told Live Science, it's not hard to figure out how far away the star is; it's fairly simple math once you know how bright the star really is and how dim it looks from Earth.

These models are especially precise for cepheids, because their rate of pulsing is directly related to their luminosity, or brightness. That makes it easy to calculate the distance to any of these stars. Astronomers are so sure they understand that relationship that cepheids have become critical tools for measuring distances all across the universe. (Read more.)


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