Polaris pulsates, a change we detect as a pattern of dimming and brightening. This pulsation helps astronomers calculate celestial distances. Why Doesn't Polaris Move? Polaris is very distant from Earth, and located in a position very near Earth's north celestial pole. Earth rotates once a day on its axis, an imaginary line that passes through Earth from its north pole to its south pole.
If that imaginary line — the axis — is projected into space above the north pole, it points to Earth's north celestial pole. Polaris, located almost exactly at the north celestial pole, the center of spin, stays in the same place, while stars farther away from the north celestial pole can be seen to move in a wider circle around Polaris as viewed from Earth during its daily rotation.
Polaris actually lies just a short distance away from where Earth's axis points. Polaris is located about 1 degree off to the side of the north celestial pole, so Polaris does move a little, tracing a very small arc in the night sky, around which the other visible stars make wider circles.
Polaris is a Cepheid variable, meaning that it has a regular cycle of brightening and dimming, similar to other stars of its type. However, it has been getting brighter during the past couple of decades, for reasons that are still poorly understood.
While the star is still relatively dim, as of a group of scientists estimated that Polaris could be about 4. A minor meteor shower known as the Camelopardalids — which streaks from a location near Polaris — occasionally produces good shows.
While the first show ended up being a bust, a relatively strong meteor shower was reported in Polaris is located in the constellation of Ursa Minor, the Little Bear. It sometimes also goes by the name " Stella Polaris. Polaris, the North Star, lies at the end of the handle of the Little Dipper, whose stars are rather faint. Its four faintest stars can be blotted out with very little moonlight or street lighting.
The best way to find your way to Polaris is to use the so-called "Pointer" stars in the bowl of the Big Dipper , Dubhe and Merak. Just draw a line between these two stars and extend it out about 5 times, and you eventually will arrive in the vicinity of Polaris.
Interestingly, the Big and Little Dippers are arranged so that when one is upright, the other is upside down. In addition, their handles appear to extend in opposite directions. Of course, the Big Dipper is by far the brighter of the two, appearing as a long-handled pan, while the Little Dipper resembles a dim ladle. Polaris is located at a distance of light-years from Earth and has luminosity nearly 4, times that of our sun. Polaris shines at 2nd magnitude.
On this astronomers' scale, smaller numbers represent brighter objects, with the brightest stars and planets in the night sky at around magnitude zero or even negative magnitudes. The North Star it is a "pulsing" star, a Cepheid variable , which appears to vary in brightness ever so slightly — only one tenth of a magnitude — over a time frame of just under four days.
If you have a small telescope and train it on Polaris, you just might notice a tiny companion star called Polaris B shining at 9th magnitude with a pale bluish tint. What you're seeing is Polaris , also known as the North Star, which is approximately light years away from Earth and is part of the constellation Ursa Minor. The North Star is called that because its location in the night sky is almost directly over the North Pole, according to Rick Fienberg , a Harvard-trained astronomer who now is press officer of the American Astronomical Society.
Polaris is attention-getting, because unlike all the other stars in the sky, Polaris is in the same location every night from dusk to dawn, neither rising nor setting, according to Fienberg. Its looming presence leads some people to think of it, mistakenly, as the brightest star in the sky it's actually the 48th brightest. Even so, it's about 2, times as luminous as our sun, because it's a massive supergiant with a diameter nearly 40 times larger than the sun and five times the mass.
But Polaris also happens to be far away for a star that's visible with the naked eye, which reduces its brightness. Who discovered the North Star? That's a complicated question. Ancient Egyptian astronomers in the Old Kingdom, between 4, and 4, years ago, had a North Star, which they symbolically represented with a female hippopotamus, according to Giulio Magli's book " Architecture, Astronomy and Sacred Landscape in Ancient Egypt.
That's because what humans perceive as the North Star changed over time. We say that Earth's North Pole is 'precessing,' that is, the line that goes from the North Pole to the South Pole traces out a circle with a period of 26, years. As a result, "over very long time periods more than a few thousand years , the North Pole moves with respect to the stars," Palma continues. Polaris seems to have been first charted by the astronomer Claudius Ptolemy , who lived from about 85 to B.
The star's location close to the celestial North Pole eventually became useful to navigators. You can also tell your latitude, since the angle from the horizon to Polaris is the same as your latitude to within a degree, anyway. Once you travel south of the equator, though, Polaris drops below the horizon, so it's no longer useful as a navigation aid.
0コメント