This regular change in brightness is caused by pulsations, as Cepheids alternately expand and contract. Cepheid variables are giant and supergiant stars that vary with regular periods anywhere from a few days to about two months. More specifically, Polaris is a Cepheid variable, an important class of variable stars. Polaris is a variable star, meaning that its brightness changes.
![polaris star polaris star](https://cdn2.vectorstock.com/i/1000x1000/44/51/star-polaris-sharp-white-flat-style-lights-twinkle-vector-6744451.jpg)
Yet another misconception is that Polaris has constant brightness. That would will make Vega a pole star of note. In about 12,000 years, precession of the equinoxes will bring Vega within four degrees of the north celestial pole. Vega, the fifth brightest star in the sky, is a case in point. Many people think that the North Star is the brightest star in the sky, so they are surprised when Polaris is pointed out to them, and they readily see that there are brighter stars.
![polaris star polaris star](https://st4.depositphotos.com/1001521/21068/v/1600/depositphotos_210683590-stock-illustration-finding-north-star-polaris-night.jpg)
This brings up another pole star misconception. But at many times in the past there was not any noticeable star close enough the north celestial pole to qualify as “the North Star.” Indeed, the star we now call the North Star gained this status only during the Middle Ages (hence Shakespeare’s use during the time of Julius Caesar is an example of an anachronism). At the time of the conventional date of construction of the Great Pyramid of Giza, the pole star was Thuban, the brightest star in the Constellation Draco (Thuban is 25 degrees away from the north celestial pole now). Hence, over time Polaris and other stars are at varying distances from the north celestial pole, and there will be different pole stars. This motion is very slow, taking 25,900 years to complete one cycle. Precession of the equinoxes causes the celestial poles to move along large circles in the sky. Due to the gravitation of the sun and moon, the earth’s rotation axis undergoes precession of the equinoxes. But since there is no bright star near the south celestial pole, there is no “South Star.” The star we now call the North Star gained this status only during the Middle Ages.Īnother misconception is that Polaris always has been the pole star. South of the equator, all the stars appear to spin around the south celestial pole. The south celestial pole is the projection of the earth’s rotation axis onto the sky in the direction opposite the north celestial pole. But south of the equator the south celestial pole is above the horizon. Nor is the north celestial pole above the horizon south of the equator. This is why we call Polaris the North Star-its location so close to the north celestial pole fixes its position within ¾ degree of true north above the horizon.įor those of you wondering about the Southern Hemisphere, Polaris is not visible in locations more than one degree south of the equator. However, a telescope will reveal that Polaris goes through a tiny circle each sidereal day (a sidereal day is about four minutes shorter than a solar day). Polaris lies within ¾ of a degree of the north celestial pole, so to the naked eye Polaris appears to remain fixed. The north celestial pole is a projection of the earth’s rotation axis onto the sky.
![polaris star polaris star](https://cdp.azureedge.net/products/USA/PO/2020/UTILVEH/USXS/RANGER_CREW_XP_1000_NORTHSTAR_ULTIMATE/50/SAND_METALLIC/2000000001.jpg)
Consequently, the stars appear to spin around a point in the sky that we call the north celestial pole. After sunset, that rotation doesn’t stop (or else the sun wouldn’t rise tomorrow morning). This is due to the earth’s rotation, which also causes the sun to rise, move across the sky, and set each day. Each night in the Northern Hemisphere, the sky appears to spin around Polaris. To the naked eye, Polaris certainly does seem to remain fixed.
![polaris star polaris star](https://cdn.w600.comps.canstockphoto.com/the-polaris-star-picture_csp19256516.jpg)
The company said Friday it has moved the Star Polaris to Daewoo Mangalia shipyard in Romania for permanent repairs, which Star Bulk expects to finish in about 30 days.In Act III, Scene I of Shakespeare’s play Julius Caesar, Caesar says, “I am constant as the northern star.” This seems to be the source of the common misconception that Polaris (aka the North Star) perpetually remains motionless and steady. The company had benefited from cost-cutting and modest revenue growth before posting losses caused by renewed macroeconomic headwinds that swept the shipping sector last year. The ship's damage is the latest setback for Star Bulk, which returned to the red in its latest two quarters after a straight year of profits. The shipping company, which transports iron ore, coal and grain, said it is investigating the incident and hinted it could blame the port for unsafe conditions. The company said its Star Polaris vessel suffered bottom damage entering port at Eregli, Turkey. (SBLK) said one of its ships suffered hull damage entering a Turkish port, forcing the company to declare the vessel off-hire to potential charterers for at least a month.