Vega: The Once and Future North Star
Vega is a bright star located just 25 light-years from Earth, visible in the summer sky of the Northern Hemisphere. The star is part of the constellation Lyra and, with the stars Deneb and Altair, forms an asterism known as the Summer Triangle.
The star is only about 450 million years old, which makes it a youngster compared to our own solar system (which is 4.6 billion years old). Studies of Vega help astronomers learn more about solar systems that are in the early stages of their formation.
Because the Earth’s axis wobbles, our perception of north gradually shifts to different stars over a 26,000-year cycle. Vega was the North Star several thousand years ago, and it will regain that status in about 12,000 years.
Vega is almost directly overhead at midnorthern latitudes on midsummer nights. Vega sinks below the horizon for only 7 hours a day and can be seen on any night of the year.
Farther south, Vega lies below the horizon for a longer period, but in Alaska, northern Canada and much of Europe, Vega never sets. The star’s location is:
- Right ascension: 18h 36m 56.3s.
- Declination: 38 degrees 47 minutes 01 second.
Because Vega’s blue-white light is so bright — the star has an apparent magnitude of 0.03 — it features prominently in ancient cultures, ranging from the Chinese to the Polynesians to the Hindus. Vega’s name comes from the Arabic word “waqi,” which means “falling” or “swooping.”
“This is a reference to the time when people regarded the constellation Lyra as a swooping vulture rather than a lyre,” wrote Michael Anissimov on the website Wisegeek.
The name of Vega and those of other astronomical targets honor the traditional importance of astronomy in Islam, noted one researcher. Following the stars allowed believers to mark the times of prayer and festivals, as well as to find the holy city of Mecca.
To find the star Vega in the constellation Lyra, look directly overhead. North lies at the top of the sky map. (Image credit: Starry Night Software)
“Thus, hundreds of stars and constellations have Arabic names, such as Altair, Deneb, Vega and Rigel,” wrote Nidhal Guessoum, an astrophysicist at the American University of Sharjah in the United Arab Emirates, in a 2013 article published in the journal Nature.
In modern times, Vega was the first star to be photographed, other than the sun. Astronomers captured the image through the daguerreotype process at Harvard College Observatory, using a 15-inch (38 centimeters) refractor, on July 16-17, 1850.
The star was also chosen for the first spectrographic image, in 1872. amateur astronomer Henry Draper was the first to break down Vega’s light to reveal the various elements that make up the star.
Vega in recent years
Vega rose to prominence in popular culture in the late 1990s after Carl Sagan’s novel “Contact” (1985, Simon & Schuster) was adapted into a Hollywood movie. Starring Jodie Foster, the movie followed an astronomer working on the search for extraterrestrial intelligence (SETI) who discovers a signal appearing to emanate from Vega.
Telescopic observations in 2006 revealed that Vega is whipping around so quickly that its poles are several thousand degrees warmer than its equator. The star, which rotates every 12.5 hours, is at 90 percent of its critical rotation speed, or the velocity at which the object would tear itself apart.
In early 2013, astronomers announced that they had discovered an asteroid belt surrounding Vega, suggesting the possibility of planets within the rocks’ midst. The layout (which resembled that found near the star Fomalhaut) suggests that there are two areas: an outer region with icy asteroids and a region closer to the star, where warmer space rocks reside.
Scientists are examining bright stars like Vega more closely using NASA’s TESS (Transiting Exoplanet Survey Satellite) mission, which launched in 2018 to conduct an all-sky survey. While the primary mission of TESS is to search for exoplanets, the satellite will also search for signs of star variability. TESS’s examination of Vega and similar stars will help scientists learn more about the early stages of star evolution.
Finding and Understanding the North Star
What’s the first star that comes to mind when you are asked to name one? Chances are you thought of the North Star. But do you really know it?
Star trail around the North Star, above the Pavillon de Vignes de Macheron, near Lugny, France. Long exposure photo taken in the moonlight.
Photo: Didier Auberget
Quiz: True or False?
1. The North Star is the brightest star in our sky.
2. The North Star is also called the Morning Star.
3. The north indicated by the North Star is the same north indicated by a compass.
Find the answers at the bottom of the page!
Where is the North Star?
The North Star can be seen every night of the year from the Northern Hemisphere. And it is easy to find! Just pinpoint the most renowned constellation of all, the Big Dipper. The Big Dipper’s “bowl” is made up by its four main stars. Locate the two stars at the end of the Big Dipper (away from the handle). From there, imagine a line that extends about five times beyond them, and you’ll come across the North Star. The North Star is the brightest star in the constellation Ursa Minor (also known as the Little Dipper, or Little Bear).
The North Star (and the direction of due north) is found by imagining a line from the stars that make up the end of the Big Dipper and then extending it five times up.
The North Star got its name because it is just about inside the north celestial pole, which is in line with the Earth’s rotational axis to the north. As our planet rotates on its axis (taking about 24 hours to make a full round), the stars around the north celestial pole seem to move with it, while the north celestial pole itself appears to stay put. Because the North Star is in this area, it also looks like it is motionless in the sky. Because of this, the North Star plays an important role:
- all the other stars seem to turn around it;
- it indicates the north!
French explorer Paul-Émile Victor placed the North Star at the center of his exploration expedition’s emblem on board the Commandant Charcot in 1948. This plate can be seen at the National Navy Museum in Brest, France.
The North Star Throughout History
The North Star is extremely helpful in determining direction and has throughout the years carried a great deal of symbolic meaning. For the Yakuts, it was considered “the navel of the sky,” and for the Sámi people, it was known as the hub of the heavens.
The Assyrians of ancient Mesopotamia called it “Stella Maris” (the star of the sea) since it was essential for celestial navigation at sea.
Generations of sailors from various civilizations depended heavily on the North Star to help guide their ships up until the invention of modern instruments like the compass, making this celestial object quite symbolic for seafarers all around the world.
Alaska’s state flag. DR
The North Star is also found on Alaska’s state flag, next to the Big Dipper. The state adopted this flag in 1927 after 13-year-old Benny Benson won the state competition calling for an original design. He explained his choice by saying, “The North Star is for the future state of Alaska, the most northerly in the Union.”
It goes without saying that the North Star has been held in high regard from ancient times to present day.
One Name, Many Stars
However, this star that has guided us for centuries may in fact have led us astray… Since, in reality, it’s not always the same one! But don’t worry, this change does not happen within a human lifetime. In fact, it takes several centuries for this to take place.
Though they may appear to stay put, the celestial poles (corresponding to the two directions of the Earth’s axis of rotation), actually move in the sky. What does this mean? Well, to understand the science behind it, we must understand that the Earth is slightly flat and has what is called an equatorial bulge. Because our planet’s axis of rotation is tilted, the equatorial bulge is not aligned with the plane of Earth’s orbit around the Sun (also known as ecliptic plane). However, the Sun and Moon’s gravitational pull act along this bulge to bring it back into the ecliptic plane. The result? The Earth’s axis of rotation moves about in a strange way, looking very much like a slowly spinning top, turning round and round against its backdrop of stars. This movement is called precession and takes about 26,000 years to complete a full circuit. During this time, several stars will replace the role of our beloved North Star.
Precession is the circular movement referring to the Earth’s axis of rotation, which completes its round about every 26,000 years around an axis located on the plane.
This role has changed hands a few times over the past millennia. It was first taken on by Thuban (Alpha Draconis) in 3000 BC, and then Kochab (which means “North Star” in Arabic and is today known as Beta Ursae Minoris) from 1500 BC to AD 500. Alpha Ursae Minoris, the brightest start in the constellation Ursa Minor (Little Dipper, Little Bear), currently holds this important role. In 2,000 years, Errai (Gamma Cephei) will take over for the role of the North Star and then it will be brilliant Vega’s (Alpha Lyrae) turn in about 12,000 years.
We are lucky, because our North Star is currently very close to the north celestial pole. In 2017, the angular distance between the two was measured at around 0° 40′. This will continue to decrease until the year 2102, when it reaches 0° 27′ 30”. This distance cannot be seen with the naked eye, but you’ll be able to locate due north whenever you spot the North Star. However, if a more precise location is needed, you’ll require something a bit more powerful. For example, astrophotographers must take this distance into account when they are aligning their telescopes. This can be done with a specific star diagonal which indicates Alpha Ursae Minoris’ placement from year to year.
A long exposure photo taken of the north celestial pole is enough to demonstrate that the North Star is not exactly in its center.
What about from the Southern Hemisphere?
The North Star cannot be seen from the Southern Hemisphere. Star gazers in this part of the world actually turn towards the other celestial pole (the south celestial pole) to observe the sky. Unfortunately, there are currently no bright stars near it! However, the stars of the famous Southern Cross constellation can be used to find celestial and due south.
A Stellar Portrait
The Hubble Space Telescope was used to study the North Star in depth in 2005 and revealed that it is a triple star system.
Credit: NASA, ESA, N. Evans (Harvard-Smithsonian CfA), and H. Bond (STScI)
The North Star (“Polaris” in Latin) is a supergiant! In fact, it is eight times the mass of our Sun and 2,000 times brighter—but because it is 430 light years away from the Earth, its magnitude is only 2. Its white-yellow color indicates a surface temperature around 6,800°C (12,272°F!).
And, like many other stars in the Universe, we now know that the North Star is a multiple star system! Its first companion star was discovered by British astronomer William Herschel in 1780. This star is known as Polaris B and can be found using a simple telescope with a decent diameter. It has a magnitude of 9 and is 18.4’’ away from the primary star, Polaris A. And in 2005, scientists found through the Hubble Space Telescope yet another companion close to Polaris A. This star is much smaller and is known as Polaris Ab.
Unfortunately, these partner stars cannot be seen with a simple telescope. But anyone with a pair of binoculars can still marvel at the gorgeous asterism known as the Engagement Ring, of which the North Star is the diamond!
Another thing to add to the North Star’s appeal? This star (Polaris A) also varies in brightness by a few percent across its 3.97-day cycle. When this variation in brightness was discovered in 1899, it was greater than 0.1 magnitude. But this star continues to surprise us… Unlike any other star, its brightness also changes with time! In 1983, it only had a magnitude of 0.05. In 1992, this increased to 0.01, and then again in the 2000s. The North Star continues to keep us on our toes, beginner star gazers and scientists alike!
1. FALSE. The North Star is only the 48th brightest star in our sky! First place goes to… the Sun, which lights up our days. And, at night, the star Sirius in the constellation Canis Major is the brightest of them all. But take note! Venus and Jupiter can also steal the show with their brightness, which can overtake that of Sirius.
2. FALSE. The Morning Star is actually… the planet Venus! Visible towards the west in the evening or towards the east in the morning, Venus is always close to the ecliptic plane and therefore always far from the celestial poles.
3. NOT QUITE TRUE. The North Star is used as a landmark to find the geographic North Pole. A compass’ needle is aligned with the magnetic poles of the Earth—though they aren’t to be confused with the geographic poles! In 2017, the North Magnetic Pole is about 330 kilometers (205 miles) away from the Geographic North Pole and is moving at a speed of about 55 kilometers (34 miles) per year towards Siberia.
Author: Carine Souplet
Illustrations by the author unless otherwise stated.
Translated by Natalie Worden
Sky Tellers – Polaris
SkyTellers Polaris activities for young children
How Do I Find Polaris?
Polaris is located in the constellation Ursa Minor, which contains the group of stars that make up the “Little Dipper.” Polaris is the star in the end of the Little Dipper handle. Often, however, the Little Dipper is not very bright and can be challenging to find. Polaris is easiest to find by locating the seven stars of the Big Dipper in the constellation Ursa Major, or Big Bear. These stars form a small bowl with a long handle. Follow the stars of the Big Dipper from the handle to the side of the bowl, to the bowl bottom, and up the other side; the two stars forming the second side, Dubhe and Merak, point to Polaris. Take the distance between Dubhe and Merak; Polaris is the bright star that sits about five times that distance away.
Polaris actually is part of a binary (two) star system. Of the stars nearest to our Sun, about half are known to be in multiple systems (two or more stars). Between 5 and 10 percent of the stars we can observe are “visible binaries” — the star companions can be observed with a telescope. These systems reveal a great deal of information. Because of their interactions, astronomers can determine the gravitational pull exerted by the companions and calculate the mass of the individual stars. Polaris is helpful to astronomers in another way; it is a variable star. 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. As the Earth spins on its axis, it also “spins around” the 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.
This picture of the night sky above Hawaii was taken by leaving the camera shutter open for a long time. The picture captures the apparent movement of the stars caused by Earth’s rotation on its axis. Polaris is the star in the center of the star field; it shows essentially no movement. Earth’s axis points almost directly to Polaris, so this star is observed to show the least movement. The other stars appear to trace arcs of movement because of Earth’s spin on its axis.
Photograph by Richard J. Wainscoat
Polaris is Our Pole Star… for Now
Stargazers are familiar with the concept of the “pole star”. In particular, they know about the north star, with its formal name of Polaris. For observers in the northern hemisphere and parts of the southern hemisphere, Polaris (formally known as α Ursae Minoris because it’s the brightest star in the constellation), is an important navigational aid. Once they locate Polaris, they know they’re looking north. That’s because the north pole of our planet appears to “point” at Polaris. There is no such pole star for the southern celestial pole, however.
What’s the Next North Pole Star?
An artist’s concept of how the Polaris system looks. Based on HST observations.
NASA/ESA/HST, G. Bacon (STScI)
Polaris is one of the most searched-out stars in the northern hemisphere sky. It turns out that there’s more than one star at Polaris. It’s really a triple star system that lies around 440 light-years away from Earth. The brightest is what we call Polaris. Sailors and travelers have used it for navigational purposes for centuries because of its constant-seeming position in the sky.
Because Polaris is located very close to the point where our north polar axis points, it appears motionless in the sky. All the other stars appear to circle around it. This is an illusion caused by Earth’s spinning motion, but if you’ve ever seen a time-lapse image of the sky with an unmoving Polaris at the center, it’s easy to understand why early navigators gave this star so much attention. It has often been referred to as a “star to steer by”, particularly by early sailors who traveled the uncharted oceans and needed celestial objects to help them find their way.
Why We Have a Changing Pole Star
Precessional movement of Earth’s pole. Earth turns on its axis once a day (shown by the white arrows). The axis is indicated by the red lines coming out the top and bottom poles. The white line is the imaginary line the pole traces out as Earth wobbles on its axis.
NASA Earth Observatory adaptation
Polaris hasn’t always been our north pole star. Thousands of years ago, the bright star Thuban (in the constellation Draco), was the “north star”. It would have been shining over the Egyptians as they began building their early pyramids. Over the centuries the sky slowly appeared to shift and so did the pole star. That continues today and will do so into the future.
Around the year 3000 AD, the star Gamma Cephei (fourth-brightest star in Cepheus) will be closest to the north celestial pole. It will be our North Star until about the year 5200 AD, when Iota Cephei steps into the limelight. In 10000 AD, the familiar star Deneb (the tail of Cygnus the Swan) will be the North Pole star, and then in 27,800 AD, Polaris will take up the mantle again.
Why do our pole stars change? It happens because our planet is wibbly-wobbly. It spins like a gyroscope or a top that wobbles as it goes. That causes each pole to point at different parts of the sky during the 26,000 years it takes to make one complete wobble. The actual name for this phenomenon is “procession of Earth’s rotational axis”.
How to Find Polaris
How to find Polaris using the Big Dipper’s stars as a guide.
Carolyn Collins Petersen
To locate Polaris, find the Big Dipper (in the constellation Ursa Major). The two end stars in its cup are called the Pointer Stars. Draw a line between the two and then extend it out about three fist-widths to get to a not-too-bright star in the middle of a relatively dark area of sky. This is Polaris. It’s at the end of the handle of the Little Dipper, a star pattern also known as Ursa Minor.
An interesting note about the name of this star. It’s actually a shortened version of the words “stella polaris,” which is a Latin term for “polar star. ” The names of stars are often about the myths associated with them, or, as with Polaris, are given to illustrate their practicality.
Changes in Latitude…Polaris Helps Us Figure Them Out
This illustrates Polaris at an angle 40 degrees up from the horizon of the observer, who is looking from an observing site located at 40 degrees latitude on Earth.
Carolyn Collins Petersen
There’s an interesting thing about Polaris — it helps people determine their latitude (unless they are too far south to see it) without needing to consult fancy equipment. This is why it has been so useful to travelers, particularly in the days before GPS units and other modern navigational aids. Amateur astronomers can use Polaris to “polar align” their telescopes (if needed).
After Polaris is found, it’s easy to do a quick measurement to see how far above the horizon it is. Most people use their hands to do it. Hold a fist out at arm’s length and align the bottom of the fist (where the little finger is curled up) with the horizon. One fist-width equals 10 degrees. Then, measure how many fist-widths it takes to get to the North Star. Four fist-widths means 40 degrees north latitude. Five indicates fifth degrees north latitude, and so on. And, an added bonus: when people find the north star, they know they’re looking north.
What about the south pole? Don’t the southern hemisphere folks get a “south star”? It turns out that it does. Right now there is NO bright star at the south celestial pole, but over the next few thousand years, the pole will point at the stars Gamma Chamaeleontis (the third-brightest star in Chamaeleon, and several stars in the constellation Carina (the Ship’s Keel), before moving on to Vela (the Ship’s Sail). More than 12,000 years from now, the south pole will point toward Canopus (the brightest star in the constellation Carina) and the North Pole will point very close to Vega (the brightest star in the constellation Lyra the Harp).
How to navigate using the Stars
Latest News: The new online course – The Beginner’s Guide to Natural Navigation – includes a video tutorial on how to use the stars to navigate.
Lots of people love the idea of finding direction and navigating using the stars, but are put off because they fear it is complicated. It does not need to be complicated at all, it is something you can learn to do in minutes. In fact finding direction using the stars is much quicker and easier than using a compass. It is also a lot more fun.
To navigate using the stars all we need do is find a star that is directly above the place we want to get to and it will point exactly the right direction for us, from quarter of the globe away.
If you called a friend on the telephone who was in another country a few thousand miles away, and you asked them to name the star that was directly over their head, you could then find that star in the night sky and the point on the horizon directly below that would be their exact direction from you at that moment.
Unfortunately, a few minutes later that star would have moved and so you would need a new one. It would take a lot of phone calls to use this method with most stars! Fortunately there is one star in the night sky that does not appear to move. It is called Polaris, or the North Star. It is directly overhead the North Pole. This means that whenever we point towards the spot on the horizon directly below the North Star, we must be pointing north.
The easiest method for finding the North Star is by finding the ‘Big Dipper’, an easy to identify group of seven stars. It is known as the ‘Plough’ in the UK and the ‘saucepan’ to many others. Next you find the ‘pointer’ stars, these are the two stars that a liquid would run off if you tipped up your ‘saucepan’. The North Star will always be five times the distance between these two pointers in the direction that they point (up away from the pan). True north lies directly under this star. See the animated illustration above.
The ‘Big Dipper’ rotates anti-clockwise about the North Star, so it will sometimes appear on its side or even upside down. However its relationship with the North Star never changes and it will always dependably point the way to it.
The reason the North Star is so important for natural navigation is that it sits directly over the North Pole. Something that people often forget is that whenever you are trying to find true north, you are actually trying to find the direction of the North Pole from wherever you are – even if you are only heading a few hundred metres on a gentle walk – ‘north’ is still just an abbreviation for ‘towards the North Pole’.
The constellation, Cassiopeia, is also very helpful in finding the North Star as it will always be on the opposite side of the North Star from the Plough and therefore often high in the sky, when the Plough is low or obscured.
Having found the North Star, there is something about its height above the horizon that is well worth knowing. Wherever you are in the northern hemisphere, the North Star will be the same angle above the horizon as your latitude. This can be measured accurately using a sextant, but an estimate can be made using an outstretched fist. We are all different shapes and sizes, but we share proportions. An outstretched fist makes an angle of close to 10 degrees for most people. In an under a minute and with just your bare hands you can now find north and estimate your latitude.
The constellation, Orion, rises in the east and sets in the west. Orion’s belt, the only three bright stars that form a short straight line in the whole night sky rise very close to due east and set very close to due west. If you want to be really accurate then the first star in the belt to rise and set, called Mintaka, will always rise and set within one degree of true east and west wherever you are in the world.
Lots more information about these methods and lots of others can be found in my books.
They also contains lots of information on using the sun, moon, plants and animals to help you find your way, on land or at sea or even in the city.
For a video tutorial on how to use these methods, please see the online course, The Beginner’s Guide to Natural Navigation.
Why Is the North Star So Stellarly Important?
If you ever looked at the night sky in the Northern Hemisphere, you’ve noticed that gleaming object that the rest of the heavens appears to move around. What you’re seeing is Polaris, also known as the North Star, which is approximately 430 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 Doesn’t Rise and It Doesn’t Set
“So, if you were to stand at the North Pole — latitude 90 degrees north — at night and look straight up, you’d see Polaris directly overhead,” Fienberg says via email. “From other latitudes in the Northern Hemisphere, if you face due north at night and look the same angle above the horizon as your latitude (for example, look about halfway up – 45 degrees – if you live in Portland, Oregon, at latitude 45 degrees north), you’ll see Polaris shining there.”
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 2,500 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 First Found the North Star?
Who discovered the North Star? That’s a complicated question. Ancient Egyptian astronomers in the Old Kingdom, between 4,700 and 4,100 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.” But it wasn’t Polaris.
That’s because what humans perceive as the North Star changed over time. “If you picture a line connecting Earth’s North and South Poles as the axis around which Earth rotates, that axis is slowly moving in its own circle,” explains Christopher Palma, a former teaching professor in astronomy who currently is associate dean of the Eberly College of Science at Penn State University, in an email. “Often, this is compared to what happens when a top or a spinning coin start to ‘wobble’ before falling over on their side. 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 26,000 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. “So thousands of years ago, people on Earth saw the star Thuban in [the constellation] Draco appear due north, instead of Polaris.”
The North Star in Navigation
Polaris seems to have been first charted by the astronomer Claudius Ptolemy, who lived from about 85 to 165 B.C.E. The star’s location close to the celestial North Pole eventually became useful to navigators.
“At night, in the Northern Hemisphere, if you can see Polaris you can always tell which way is north (and, by extension, which ways are south, east and west),” Fienberg says. “It’s true now, it’s been true for hundreds of years (including during the Age of Exploration in the 15th through 17th centuries), and it’ll be true for hundreds more years. 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.”
Additionally, a navigator using Polaris has to take into account that the star isn’t precisely over the North Pole but instead has an offset of 39 arc-minutes, explains Rich Schuler, a lab manager and adjunct faculty member who teaches astronomy at the University of St. Thomas in St. Paul, Minnesota, in an email interview. (He’s author of this 2002 primer on the North Star in Scientific American.) That corresponds to an error of 44.7 miles (72 kilometers), he says.
Here’s Why the North Star Twinkles
One of the other things that’s intriguing about Polaris is that it’s what astronomers refer to as a Cepheid Variable star. “This star pulsates because it is in a state that is unstable,” says Palma. “It will swell up, and when it does, an outer layer of the star becomes transparent, which then makes the star cool off. As a result of it cooling off, it will shrink until it becomes opaque again, which causes it to heat up and swell again. It will do this over and over again, pulsating in and out, which causes its brightness to fluctuate.”
And although you can’t tell when you gaze at Polaris in the night sky, it’s actually part of a triple star system. “The two fainter stars (Polaris Ab and B) do not vary in brightness because they are on the ‘main sequence,’ or are generating energy by fusing hydrogen nuclei into helium nuclei only in the core of the star,” Schuler explains.
Polaris won’t be the North Star forever. “If you look at the 14,000 C.E. point, you’ll see a star that’s much, much brighter than Polaris but farther from the circle,” Fienberg says. “That’s Vega, which our descendants some 12,000 years from now (if humans are still around) will consider their North Star. “
Originally Published: Nov 20, 2019
Looking Up: The wonder of the North Star – News – Monroe News – Monroe, Michigan
One of the most famous stars in the night sky, as seen from the Northern Hemisphere, is Polaris, the North Star. Technically known as Alpha Ursae Minoris, as it is the brightest star in Ursa Minor the Little Bear, its other names are fitting only temporarily.
Before we get into this further, here’s how to find the North Star: It is not the brightest star in the sky despite its distinction, nor is it otherwise remarkable, but it is a faithful guide for anyone needing to know their way in the night – assuming the sky is clear! Prior to satellite telemetry, ship captains and airplane pilots would navigate by the stars, and the North Star was invaluable.
It is the one easily visible star that never seems to go anywhere. As the world turns (no, not the soap opera), the constellations of stars appear to rise in the east and set in the west, in the same way the sun makes its daily trek in the daytime sky (ever see the sun in the night sky?). Constellations and stars that never set are referred to as “circumpolar.” They circle a point in the northern sky known as the north celestial pole, right next to Polaris.
Your latitude on the globe is easily determined by noting how high above the north horizon the North Star shines. On the ocean from the Earth’s equator, the North Star would be right on the horizon; at the North Pole, it would shine straight overhead.
To find the North Star, look due north (opposite where the nun is at noon), and look not quite halfway up in the sky (assuming you live in mid-northern latitudes). On a late September evening, you will see the familiar Big Dipper riding low in the northwest. The two stars in the front of the Dipper’s “bowl” appear to point right at the North Star.
Polaris just happens to be very close to the north celestial pole, making it seem to be a pivot for the rest of the sky to circle around. It wasn’t always so. The earth’s axis of rotation has an extremely slow wobble, making a circle on the sky every 25,800 years. An immense amount of time by human standards, it makes a difference only when looking back or forward at least hundreds of years. The earth’s axis changes where it is pointing in a circle 47 degrees wide. If you go back 3,000 years, the north celestial pole lay very near the star Thuban in the constellation Draco the Dragon. Thuban is easily seen though a bit dimmer than today’s North Star. Thuban was the North Star when the Egyptians were building the pyramids, and in fact built the pyramids to align with Thuban.
Through the ages, the north celestial pole spends great lengths nowhere close to any star easily visible to the unaided eyes. We are fortunate to live in an age when we do have a bright star to mark the north. In the past 500 years, when seafarers were exploring the globe, Polaris was reasonably near the north celestial pole, just in time to aid their navigation when mankind needed it the most.
The slow wobble of the earth’s axis is caused by gravitational tugs from the sun and moon, pulling on the earth’s uneven shape (it is a bit wider at the equator). The wobble, known as the “Precession of the Equinoxes,” was first realized by Greek astronomer Hipparchus around 130 B.C.
The same situation happens “Down Under” as well. Southern Hemisphere residents, however, do not have a bright “South Star” during this epoch. The closest naked eye star to the South Celestial Pole is Sigma Octantis. This star is magnitude 5-1/2, just visible without optical aid, in a dark sky. Polaris is second magnitude.
Measurements made by the Gaia spacecraft in 2018 gave a distance of 445.3 light years for the North Star.
Polaris is also a nice double star, visible in telescopes of three inch aperture or more.
Last quarter-moon is on Sept. 21 and new moon is on Sept. 28.
Keep looking up!
Peter Becker is Managing Editor at The News Eagle in Hawley, PA. Notes are welcome at [email protected] Please mention in what newspaper or web site you read this column.
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90,000 TEC of the Cherdyn City District met with the editor-in-chief of the newspaper “Severnaya Zvezda”
TEC of the Cherdyn City District held a meeting with the editor-in-chief of the newspaper “Severnaya Zvezda” – Territorial Election Commission of the Perm Municipal District
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Chairman of the TEC of the Cherdynsky urban district Tatyana Bessonova held a meeting with the editor-in-chief of the newspaper “Severnaya Zvezda”.During the meeting, the head of the commission informed the head of the newspaper about the competition among the media for the best publication, coverage of the electoral process. The competition was announced by the Election Commission of the Perm Territory, the purpose of which is to attract the media to comprehensive and objective coverage of elections, electoral legislation, as well as to increase confidence in the institution of elections (referendums) in the Perm Territory.
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