Bad Astronomy: Misconceptions and Misuses Revealed, from ...

THE BRIGHTEST STAR 115
point of light, the same way that a pair of headlights on an automobile
might look like one light from far away.
Polaris is hundreds of light-years away, so the fact that it’s near
our NCP is simply a coincidence. Just to prove that point, the nearest
star to the south celestial pole is the barely visible star Sigma
Octans, which is something like the three-thousandth brightest star
in the sky. And note that these stars only work for the Earth; from
another planet, like Jupiter, Polaris is nowhere near its NCP.
Actually, it’s not even precisely on the NCP as seen here on
Earth. Currently, Polaris sits about a degree away from the NCP,
the equivalent to twice the diameter of the full Moon as seen from
the Earth. Still, compared to the whole sky, that’s pretty close.
But it’s more than just a coincidence in space; it’s a coincidence
in time as well.
Remember, Polaris is what it is because the Earth’s axis points
more or less toward it. However, the Earth’s axis isn’t perfectly
fixed in space. As we saw in chapter 5, “A Dash of Seasons,” the
Earth’s axis drifts slowly in space, making a circle roughly a quarter
of the sky across every 26,000 years or so. This precession of
the axis means that the Earth’s north pole changes its position relative
to the sky over time. So the fact that it’s near Polaris right now
is simply a coincidence. Over the years the Earth’s pole will move
slowly away from Polaris, leaving behind the relatively faint star, demoting
it to its proper place among the second-tier stars in the sky.
Worse, in 14,000 years or so, the star Vega will be near the
NCP. Vega is the fourth-brightest star in the sky, a shining, brilliantblue
gem in the northern summer sky, and very obvious even in
light-polluted skies. If people mistake the brightness of a star with
its importance now, with the dim Polaris sitting on the throne, then
the situation will be far worse when Vega occupies that position.
Until that time off in the distant future, we’ll still need Polaris
to tell us which way is north, and that’s enough to make Polaris
important. But it’s still not bright, which is why I think people
confuse its brilliance—or lack thereof—with its stellar status. Just
like people, stars can be important without being terribly bright.