The North Star has spots!
Click for original image.
Astronomers using an array of six ground-based telescopes have obtained best new data of Polaris, the North Star, including the first rough image of its surface, and discovered sunspots on its surface.
You can read the paper here [pdf]. The image to the right, taken from figure 4 of the paper, shows the surface as seen by the telescopes over two nights in April 2021. Polaris is what astronomers call a Cepheid variable star, which changes brightness on a very precise schedule as its diameter grows and shrinks. In the case of Polaris, that variation is four days long. The star’s brightness itself varies only slightly, and over the decades has even at times appeared to cease its variations.
As the true brightness of Cepheids is very predictable based on their pulse rate, these stars are one of the main tools astronomers use to determine distances to other galaxies. Knowing more about them thus has great importance to cosmological research.
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. “The CHARA images revealed large bright and dark spots on the surface of Polaris that changed over time,” said Gail Schaefer, director of the CHARA Array. The presence of spots and the rotation of the star might be linked to a 120-day variation in measured velocity.
The researchers plan to take regular images again of Polaris to better track the changes to its surface.
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Click for original image.
Astronomers using an array of six ground-based telescopes have obtained best new data of Polaris, the North Star, including the first rough image of its surface, and discovered sunspots on its surface.
You can read the paper here [pdf]. The image to the right, taken from figure 4 of the paper, shows the surface as seen by the telescopes over two nights in April 2021. Polaris is what astronomers call a Cepheid variable star, which changes brightness on a very precise schedule as its diameter grows and shrinks. In the case of Polaris, that variation is four days long. The star’s brightness itself varies only slightly, and over the decades has even at times appeared to cease its variations.
As the true brightness of Cepheids is very predictable based on their pulse rate, these stars are one of the main tools astronomers use to determine distances to other galaxies. Knowing more about them thus has great importance to cosmological research.
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. “The CHARA images revealed large bright and dark spots on the surface of Polaris that changed over time,” said Gail Schaefer, director of the CHARA Array. The presence of spots and the rotation of the star might be linked to a 120-day variation in measured velocity.
The researchers plan to take regular images again of Polaris to better track the changes to its surface.
Readers!
Please consider supporting my work here at Behind the Black. Your support allows me the freedom and ability to analyze objectively the ongoing renaissance in space, as well as the cultural changes -- for good or ill -- that are happening across America. Fourteen years ago I wrote that SLS and Orion were a bad ideas, a waste of money, would be years behind schedule, and better replaced by commercial private enterprise. Only now does it appear that Washington might finally recognize this reality.
In 2020 when the world panicked over COVID I wrote that the panic was unnecessary, that the virus was apparently simply a variation of the flu, that masks were not simply pointless but if worn incorrectly were a health threat, that the lockdowns were a disaster and did nothing to stop the spread of COVID. Only in the past year have some of our so-called experts in the health field have begun to recognize these facts.
Your help allows me to do this kind of intelligent analysis. I take no advertising or sponsors, so my reporting isn't influenced by donations by established space or drug companies. Instead, I rely entirely on donations and subscriptions from my readers, which gives me the freedom to write what I think, unencumbered by outside influences.
You can support me either by giving a one-time contribution or a regular subscription. There are four ways of doing so:
1. Zelle: This is the only internet method that charges no fees. All you have to do is use the Zelle link at your internet bank and give my name and email address (zimmerman at nasw dot org). What you donate is what I get.
2. Patreon: Go to my website there and pick one of five monthly subscription amounts, or by making a one-time donation.
3. A Paypal Donation or subscription:
4. Donate by check, payable to Robert Zimmerman and mailed to
Behind The Black
c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652
You can also support me by buying one of my books, as noted in the boxes interspersed throughout the webpage or shown in the menu above.
What I didn’t know: Polaris A is a binary. Semimajor 6.2 AU = 29 times the stellar radius, Ab eccentricity = 0.635. Period ~29.4 years. This certainly helps gauge the mass-ratio.
Or maybe triple star system? from linked article, “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.
All this time it was a Cepheid variable and I had no idea :(
John wrote, “All this time it was a Cepheid variable and I had no idea.”
One of the first magazine articles I ever got published, in March 1995 for Astronomy, was specifically on Polaris and its variable star nature. I too was astonished then to discover it was a Cepheid that varied in brightness.
“But I am constant as the Northern Star,
Of whose true fixed and resting quality
There is no fellow in the firmament.
The skies are painted with unnumbered sparks;
They are all fire, and every one doth shine;
But there’s but one in all doth hold his place”
‘Julius Caesar’ Act III Scene I The Bard 1599
While I agree with McCoy’s assessment of Gen. Chang’s delivery, it was still core.