[이광식의 천문학+] The story of the North Star, where three stars are seen as one

▲ The Integrative Flux Nebula (IFN) that surrounds Polaris and its surrounding sky. Photo courtesy of Javier Zayaz

An unusual astronomical photograph of Polaris and its surroundings is attracting attention as it was published in the April 11 issue of ‘Astronomical Picture of the Day (APOD)’ operated by NASA. An unusual nebula called the ‘Integrated Flux Nebula’ (IFN) surrounds the North Star as if it were surrounding it.

First of all, to briefly explain Polaris, Polaris, the alpha star of Ursa Minor, is a second-magnitude star that meets when the earth’s axis of rotation extends north. Therefore, when the earth rotates, the stars seem to rotate around the North Star, but the North Star itself always stays in the same north direction, so it was called the North Star, but strictly speaking, it is not a proper name but a common noun. In English, it is called Polaris, and our old name is Gujindaeseong.

So what is the South Pole? does not exist. There is currently no bright South Pole star because there are no bright stars near Earth’s southern axis. Earth’s axis of rotation pointed in a slightly different direction, so Vega was the North Star.

5,000 years ago, Tuban, the alpha star of Draco, was the North Star. This is because the earth’s axis of rotation is slightly shifted due to the precession of the earth. The Earth’s axis of rotation is not firmly fixed in outer space, and rotates in a small circle every 26,000 years. Now, Polaris is also moving away from the Celestial North Pole little by little, and it is said that in regarding 12,000 years, Vega, the alpha star of Lyra, will become the North Star.

Things to learn when you find the North Star

Polaris is not the brightest star in the sky, but if you extend the line between Merak and Dube, the two stars of the Big Dipper, by a factor of five, it will reach Polaris. If you take a look at the true face of Polaris, don’t be surprised, it is a supergiant with a brightness 2000 times that of the Sun and a Cepheid variable star with two companion stars. So the three stars look like one.

▲ Polaris is a triple star system composed of three stars.

The brightest host star, Polaris Aa, is a supergiant star and has companions Polaris B and Polaris Ab. Away from them are the companions Polaris C and Polaris D, both discovered by William Herschel in 1780.

Cepheid variable stars, whose brightness changes by repeating contraction and expansion like the North Star, are standard light sources that allow us to determine the distance from the Earth to the corresponding object. The distance to the North Star is regarding 430 light years. The starlight of the North Star you see tonight is the light that started around the time of the Japanese invasion of Korea in 1592.

another one. The angle from which you now look up at the North Star is the north latitude of where you are standing. If the angle of elevation of the North Star seen from Seoul is regarding 38 degrees, it means that Seoul is 38 degrees north latitude. So just because you can find the North Star means you can know your bearing and latitude no matter where you are on the planet. People in the past realized that the earth was spherical when they saw the North Star rising higher towards the north.

The featured image is a digital composite of hundreds of exposures of Polaris, spanning 8 degrees, the equivalent of 16 full moons. Faint gas and dust from the integrated flux nebula IFN spans the frame, while globular cluster NGC 188 is visible towards the far left end.

INF is a relatively recently identified astronomical phenomenon. Unlike typical gaseous nebulae within the plane of our galaxy, IFNs are nebulae beyond the galactic body, so named because they are glowing with energy from the combined flux of all stars in the galaxy. An important component of the galactic interstellar medium, the nebula is composed of dust grains, hydrogen, carbon monoxide and other elements.

The Beatles’ ‘Beyond Space’ by NASA

On February 4, 2008, NASA sent the Beatles’ hit song “Across the Universe” toward the North Star in Ursa Minor to celebrate its 50th anniversary. The song, written by John Lennon of The Beatles, was launched simultaneously through three huge antennas of NASA’s International Space Network (DSN).

▲ A star keeper pointing to the Big Dipper and the Polaris. Taken in Portugal’s Alqueva Dark Sky Reserve. Photo courtesy of Miguel Claro.

This song, which contains John Lennon’s wish, ‘Sage, give me true enlightenment’, will fly to the North Star at the speed of light. It was 14 years ago, so by now, regarding 3% of the total itinerary must have flown away.

If there are extraterrestrials living near the North Star and sending back songs to that song, we will be able to hear their music in regarding 1000 years. Now, let’s go out to the yard tonight and look for the North Star in the northern night sky. In a big city like Seoul, which is covered with soot and light, the North Star starlight will not come running to you, but if you are a little out of town, it will easily reveal its face in the Bukcheon star field. And, it will give you the latitude and bearing of where you are standing. What you don’t know is whether that star will be the light of life for you when you are shipwrecked somewhere in the desert or deep in the mountains.

Lee Kwang-shik, columnist [email protected]