Vega, aka Alpha Lyrae, will be our next North Star
As children, you have often been fascinated by looking at the sky full of stars. You might have also seen the North Star, but ever wondered why is it called that? Well, this star is positioned above the Earth’s North Pole, along its rotational axis (an imaginary line around which the Earth rotates). This has earned it the title. Also called Polaris and Pole Star, it is the brightest star in the night sky.
You can see other stars as well that are as bright as the North Star. One such star is Alpha Lyrae, popularly known as Vega, the fifth brightest star. But did you know that Vega has gained significant popularity only in recent years? In addition to being extremely bright and easily visible in blue colour, the astronomy community has begun to regard it as our next North Star. Let’s unfold the reasons for this.
The secrets of the night sky
Not many of us know, but there was a Greek astronomer Hipparchus around the 129 BC. While compiling a star catalogue, he observed that the position of the stars systematically shifted every few thousand years. After extensive research, he discovered that it wasn’t the stars that shifted their position, instead, it was Earth that was in constant motion. This is why it seems that the stars are shifting.
The angle of our planet’s rotational axis undergoes a cyclic change once every 25,772 years. The Sun’s and Moon’s gravity acts on the planet’s equatorial bulge (difference between the equator and polar diameter). This causes the Earth to be in constant motion, also known as precession. Well, the effect is something out of the ordinary as the North and South Poles will interchange their position.
Even though Polaris is our North Star now, in around 12000 B.C., it was Vega. In the year 13,727, it will again become our North Star. While stars appear in a trail-like shape around Polaris, in the case of Vega, stars appear to be circling it.
Our Summer Triangle
Although Vega’s brightness fluctuates, you can see this star clearly in the summer sky of the Northern Hemisphere. In fact, it is part of the Summer Triangle in the sky, along with two more bright stars, Deneb and Altair. Vega is situated at the top of the triangle and forms a right angle between its two companions. Deneb is located to its left and Altair to its right. Astronomers locate Vega using its latitudinal angle of 38.47 degrees.
Sun shines, but Vega burns brighter!
Vega and the Sun are bright stars, but you can see the Sun during the day, while Vega is a night owl! Moreover, Vega is flat compared to the Sun, which is circular. This is because the occasional North Star has double the mass of the Sun and spins very rapidly. Scientists believe that if Vega spins even 10 per cent faster than usual, it will break apart!
Additionally, the colours of Vega and the Sun are significantly different. While Sun is reddish-yellow, the latter is bluish-white. In fact, Vega is almost 40 times brighter than the Sun, but it appears to be dimmer since it’s 25 light years away. Moreover, Vega’s life span is about a billion years, which is not even close to the Sun’s! At present, Vega is around 455 million years old. Around 500 years later, it will become a big red giant and eventually turn into white dwarf.