"For you Howard my love...The beautiful Polaris,the North Star,the brightest in the Little Dipper.And if you want to see shooting stars(meteor show) it starts tonight thru January 6th..com....a must see for star lovers." ~
Polaris – The North Star
All of us at some point in our lives have at least heard of the North Star and those of us who live in the Northern Hemisphere may have even seen the North Star if you know what you’re looking for. Polaris is at the tip of the tail or Ursa Minor, or tip of the handle of the Little Dipper depending on what you’re talking about and is the Alpha star of the constellation, the brightest star. Polaris is not the brightest star in the sky by far, that’s not its claim to fame. Polaris is the 50th brightest. But, seeing how there are millions upon millions of stars in the sky, this stars luminosity isn’t anything to sneeze at.
For a long time now, we have known that this single point was a binary star, Polaris A and B. The main star that we see is a yellow-white giant star about six times heavier than our Sun, 2.5 times larger and 2500 times brighter. Polaris B is a white star a little heavier than the Sun, a little brighter, and a little hotter. Polaris B orbits around the main star at 240 billion miles. Seeing how the Earth orbits the Sun at 93 million miles, you can tell this is a large orbit. Being bright enough and far enough from the great brightness of the main star, any decently powered telescope can see this star around Polaris.
Unfortunately, that’s not all that makes up this star system. For about 50 years, astronomers have known about a third star in orbit around Polaris but were unable to find it, until recently. Using the Hubble Space Telescope and all of the focus it could muster, a third star was found. This star has been so hard to see because it is so small, a white dwarf, and it just isn’t very bright, and its light gets lost in the light from Polaris A. Designated as Polaris Ab, this star orbits around Polaris A at a distance of 2 billion miles.
The Polaris system has been a much needed star since the birth of navigation, when the first person in history looked up at night and noticed that this star doesn’t move in the sky. Fast forward a few thousand years (most likely) and we have civilizations sailing the open seas where it was very easy to get lost, this star was a concrete reference for mariners to find their way. Even today it’s used as a much needed tool for navigation from sailors, both civilian and military, or people camping in the woods. This unique position directly above the Earth gives it the title of the North Star, meaning if you look at this star, you are looking exactly North.
This title has not always been given to Polaris. The Earth is tilted on its axis by 23.5°. On this tilt, the Earth spins like a top, making one circle around this spin every 26,000 years. Currently, the Earth’s tilt is pointed right at Polaris, but it hasn’t always. Around 3,000 BCE when the Egyptians were constructing the pyramids, the North Star was a star called Thuban in the constellation Draco. As the years ticked by, Thuban shifted farther and farther from the celestial pole. Around the birth of Christ, there was no North Star, until a thousand years or so later when Polaris was close enough to be named the North Star.
Every year, Polaris is actually getting closer and closer to exactly north. Currently Polaris is about 41.6 arcminutes ( 0.693333…° ) away from the exact celestial pole, and will be at its closest on 24 March 2100 CE and will be 27.09 arcminutes ( 0.4525° ) from the exact celestial pole. A few hundred more years, Polaris will be too far from the celestial pole to be considered the North Star and we will have to wait until around 4000 CE until Errai, a star in the constellation Cepheus will be the new North Star.
~Owen
Sources and Additional Reading
“Polaris Star”
http://www.universetoday.com/
“There’s More to the North Star Than Meets the Eye”
http://www.nasa.gov/home/
“Polaris is the North Star”
http://earthsky.org/
“Star Errai: The Future North Star”
http://earthsky.org/
Image courtesy of:
http://www.spacetelescope.org/
All of us at some point in our lives have at least heard of the North Star and those of us who live in the Northern Hemisphere may have even seen the North Star if you know what you’re looking for. Polaris is at the tip of the tail or Ursa Minor, or tip of the handle of the Little Dipper depending on what you’re talking about and is the Alpha star of the constellation, the brightest star. Polaris is not the brightest star in the sky by far, that’s not its claim to fame. Polaris is the 50th brightest. But, seeing how there are millions upon millions of stars in the sky, this stars luminosity isn’t anything to sneeze at.
For a long time now, we have known that this single point was a binary star, Polaris A and B. The main star that we see is a yellow-white giant star about six times heavier than our Sun, 2.5 times larger and 2500 times brighter. Polaris B is a white star a little heavier than the Sun, a little brighter, and a little hotter. Polaris B orbits around the main star at 240 billion miles. Seeing how the Earth orbits the Sun at 93 million miles, you can tell this is a large orbit. Being bright enough and far enough from the great brightness of the main star, any decently powered telescope can see this star around Polaris.
Unfortunately, that’s not all that makes up this star system. For about 50 years, astronomers have known about a third star in orbit around Polaris but were unable to find it, until recently. Using the Hubble Space Telescope and all of the focus it could muster, a third star was found. This star has been so hard to see because it is so small, a white dwarf, and it just isn’t very bright, and its light gets lost in the light from Polaris A. Designated as Polaris Ab, this star orbits around Polaris A at a distance of 2 billion miles.
The Polaris system has been a much needed star since the birth of navigation, when the first person in history looked up at night and noticed that this star doesn’t move in the sky. Fast forward a few thousand years (most likely) and we have civilizations sailing the open seas where it was very easy to get lost, this star was a concrete reference for mariners to find their way. Even today it’s used as a much needed tool for navigation from sailors, both civilian and military, or people camping in the woods. This unique position directly above the Earth gives it the title of the North Star, meaning if you look at this star, you are looking exactly North.
This title has not always been given to Polaris. The Earth is tilted on its axis by 23.5°. On this tilt, the Earth spins like a top, making one circle around this spin every 26,000 years. Currently, the Earth’s tilt is pointed right at Polaris, but it hasn’t always. Around 3,000 BCE when the Egyptians were constructing the pyramids, the North Star was a star called Thuban in the constellation Draco. As the years ticked by, Thuban shifted farther and farther from the celestial pole. Around the birth of Christ, there was no North Star, until a thousand years or so later when Polaris was close enough to be named the North Star.
Every year, Polaris is actually getting closer and closer to exactly north. Currently Polaris is about 41.6 arcminutes ( 0.693333…° ) away from the exact celestial pole, and will be at its closest on 24 March 2100 CE and will be 27.09 arcminutes ( 0.4525° ) from the exact celestial pole. A few hundred more years, Polaris will be too far from the celestial pole to be considered the North Star and we will have to wait until around 4000 CE until Errai, a star in the constellation Cepheus will be the new North Star.
~Owen
Sources and Additional Reading
“Polaris Star”
http://www.universetoday.com/
“There’s More to the North Star Than Meets the Eye”
http://www.nasa.gov/home/
“Polaris is the North Star”
http://earthsky.org/
“Star Errai: The Future North Star”
http://earthsky.org/
Image courtesy of:
http://www.spacetelescope.org/
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