DELTA PAV (Delta Pavonis). It's always fascinating to see among the
stars one like the Sun, some kind of solar
clone, and then wonder if there are any earths like ours. It's also
fascinating to see one as bright as fourth magnitude (3.56, almost
third), one prominent enough to be part of its constellation outline
(Pavo, the Peacock), one deep in the
southern hemisphere, the star but 24 degrees from the South Celestial Pole. Like the Sun it's
a class G star, though cooler (G6-8, probably the latter), but unlike
the Sun it's classed spectrally as a subgiant, which at first
implies that it has just finished its career as a hydrogen-fusing
dwarf or at least will soon.
Of additional interest, it's not far from another star with solar
similarities, Gamma Pavonis, an F6
dwarf. To be so visually bright for its class, the star has to be
close to us, and at just 19.92 light years (with a probable error
of only 0.02 light years) it most certainly is. Delta Pav's
proximity also gives it a rapid motion across the sky relative
to the background stars, a whopping (it's all relative) 1.66 seconds
of arc per year, something that could be easily noted in a small
telescope over a lifetime of observing. From that, the distance,
and the velocity of 21.7 kilometers per second along the line of
sight, we calculate a total velocity of 52.6 kilometers per second
relative to the Sun, more than three times normal, suggesting that
the star is a visitor from some other place in the Galaxy, one not on a fairly
circular Galactic orbit as are we. With a surface temperature of
5548 Kelvin (vs. the Sun's 5780), Delta Pav is 26 percent more
luminous than our own star, which gives it a radius of 1.22 times
solar. Theory suggests a mass about that of the Sun, one study making
it seven percent higher, which with possible advanced age would
account for its higher luminosity. A projected equatorial rotation
speed of but 1.0 kilometers per second gives it a rotation period
that could be as long as 61 days (against the Sun's 25), also
suggesting age (a solar type star slowing down with age as a result
of magnetic activity coupled to its wind). The star has a metal
content (relative to hydrogen) of around double that of the Sun,
suggesting a visitation from the Galactic interior where metal
contents run higher (as a result of more supernovae dumping their
iron and whatnot into fertile stellar breeding grounds) and
consistent with the high velocity. Being so close and so "solar,"
Delta Pavonis is a target for science fiction stories and tales of
space aliens (see also Zeta Reticuli.)
Alas, there is no evidence for planets, nor even any
for dust excess or a debris disk
that might marginally suggest planets. If
there were anybody there, they would look back to see our Sun as a
fourth magnitude (3.76) "clone" practically on our Ursa Major-Camelopardalis border, and might perhaps be
wondering whether there is anybody here. (Thanks to Larry White,
who suggested this star.)
Written byJim Kaler 5/30/14. Return to STARS.