CHARA Array false-color image of Polaris from April 2021 that reveals large bright and dark spots on the surface. Polaris appears about 600,000 times smaller than the Full Moon in the sky.Credit: Georgia State University / CHARA Array
Posted on 08/22/2024 7:28:15 PM PDT by SunkenCiv
Earth's North Pole points to a direction in space marked by the North Star. Polaris is both a navigation aid and a remarkable star in its own right. It is the brightest member of a triple-star system and is a pulsating variable star. Polaris gets brighter and fainter periodically as the star’s diameter grows and shrinks over a four-day cycle.
Polaris is a kind of star known as a Cepheid variable. Astronomers use these stars as "standard candles" because their true brightness depends on their period of pulsation: Brighter stars pulsate slower than fainter stars. How bright a star appears in the sky depends on the star’s true brightness and the distance to the star. Because we know the true brightness of a Cepheid based on its pulsational period, astronomers can use it to measure the distances to their host galaxies and to infer the expansion rate of the universe...
A team of astronomers led by Nancy Evans at the Center for Astrophysics | Harvard & Smithsonian observed Polaris using the CHARA optical interferometric array of six telescopes at Mount Wilson, Calif. The goal of the investigation was to map the orbit of the close, faint companion that orbits Polaris every 30 years...
The team successfully tracked the orbit of the close companion and measured changes in the size of the Cepheid as it pulsated. The orbital motion showed that Polaris has a mass five times larger than that of the Sun. The images of Polaris showed that it has a diameter 46 times the size of the Sun.
The biggest surprise was the appearance of Polaris in close-up images. The CHARA observations provided the first glimpse of what the surface of a Cepheid variable looks like.
(Excerpt) Read more at scitechdaily.com ...
CHARA Array false-color image of Polaris from April 2021 that reveals large bright and dark spots on the surface. Polaris appears about 600,000 times smaller than the Full Moon in the sky.Credit: Georgia State University / CHARA Array
The team successfully tracked the orbit of the close companion...
Thanks Red Badger, nice twofer!
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Wow. Interesting. I can’t wait for more sophisticated optics to show us even more detail .
If it were our Sun, it would be as large as half of Venus’ orbit..............
“Polaris has a mass five times larger than that of the Sun.
Polaris has a diameter 46 times the size of the Sun.”
That is astonishing. 46^3 = 97,336.
If Polaris and the Sun had the same density, Polaris should have about 100,000 times the mass of the sun. Yet its mass is only five times that of the sun. That suggests its density would be 1/20,000 of the Sun’s density.
That sounds like a giant gas planet rather than a star. Could you even have a star with such a low density?
Time to suspect the science
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