IOTA PER (Iota Persei). The constellations are made largely of
truly luminous stars, those bright enough to be seen easily in our
nighttime sky even though very far away. Nearly all the stars you
see at night are more intrinsically luminous than the Sun, as
clearly noted from these Star of the Week pages. It's a fine
example of a "selection effect": nature readily shows us the big
and the obvious, whereas the small and dim must be looked for even
if there are more of the latter (as is the case for stars). But
looking brings rewards, as there are still a number of solar types
in the sky to admire, stars such as Alpha
Centauri (even though it is a double, and with Proxima, a
triple) and that best of all solar clones, 18
Scorpii. Here is another, albeit a bit brighter than the Sun, Iota Persei, one of the few solar types
that actually make up part of a constellation outline. This single
class G (G0) hydrogen-fusing dwarf shines to us from northern Perseus at mid-fourth magnitude (4.05) as a
result of its closeness, only 34.4 light years, just beyond the
boundary of the standard 32.6 light years that arbitrarily defines
the "nearest stars." With a temperature of 5945 Kelvin, it is just
barely warmer than our 5780 Kelvin Sun. Its luminosity of 2.2
times solar implies a mass perhaps 10 percent greater than our
star, though masses as high as 30 percent greater have been
suggested, its age measured at 3.4 billion years, a bit younger
than the 4.5 billion year old Sun. X-rays tell of a solar-type
corona. Iota Per is a high-velocity star, moving with respect to
the Sun at a speed of 92 kilometers per second, several times that
of most of the surrounding stars. Such stars are often old and
have a low metal content, having been born in the early days of the
Galaxy. Iota, however, perversely has an iron content 25 percent
greater (relative to hydrogen) than the Sun. The star has been
rigorously searched for planets (which would
cause periodic shifts in the star's velocity), but none is found
(even though stars with planets tend to be of the high-metal
variety). Though it is listed as having a binary companion, the
dim 12th magnitude neighbor (over two minutes of arc away) probably
just lies in the line of sight. Though Iota Per is also listed as
belonging to the Alpha Persei cluster
(featuring Mirfak), it does not so
belong. It's just a lonely solar-type star seemingly with no
companions at all (though Earth-like bodies are far from being
ruled out).