MASYM (Lambda Herculis). Rather oddly, few of the brighter stars
of Hercules carry classical proper names. After the luminary, third
magnitude Kornephoros (Beta
Herculis) and Rasalgethi (Alpha Her),
we must drop to fifth magnitude Marsic
(Kappa) and then just along the Greek
letter progression to somewhat brighter fourth magnitude (4.41)
Masym (Lambda), a name (from Allen) saddled with six different
spellings (Maasym, Maasim, etc.) And even that assignment is a
mistake. Out of Arabic meaning "the wrist," the name was
originally applied to Omicron Herculis,
but later given by Bayer in error to his Lambda star. As seen
below, it's an ironic "twist of the wrist." But first, this class
K (K5) giant star is in an
interesting part of its evolution, though we are not sure just
which interesting part it is. With a temperature of 4215 Kelvin,
it shines from a distance of 369 light years (give or take 9;
second Hipparcos reduction) with the power
(including infrared radiation) of 345 Suns,
from which we calculate a radius of 35 times solar. A projected
equatorial rotation speed of 6.2 kilometers per second then gives
a rotation period less than 281 days. The numbers make us uneasy,
however, since direct measure of angular diameter yields a much
larger radius of 56 times that of the Sun, sixty percent larger.
Something is either radically wrong or the star just looks bigger
in the far red part of the spectrum where the measure was made
(which seems unlikely). Leaving the problem aside (no choice),
Masym's mass comes in at about three times that of the Sun. Theory
shows it brightening as a giant, either with a dead helium core
(350 or so million years old, prior to helium ignition into carbon
and oxygen), or with a post-helium-fusion dead carbon and oxygen
core 430 million years old, in which case it is soon going to get
a LOT brighter, reaching more than 3000 thousand times as luminous
as the Sun, over a dozen times its current luminosity, before it
begins to pulse as a Mira-type variable
prior to losing its outer envelope. Starting life as a rather
ordinary class B8 dwarf, the star has a chemical composition quite
similar to that of the Sun. All stars orbit the center of the Galaxy, though on slightly
different paths, which causes them to move through the local Galaxy
relative to the Sun. We see them moving both along and across the
line of sight, motions that over the very long term -- millions of
years -- will ultimately destroy the constellation patterns (new ones of course
taking their place). Our own Sun must have its own motion among
the stars of the local swarm. The first to calculate the "solar
motion" was William Herschel, the discoverer of Uranus, who
measured the direction toward none other than our Masym, Lambda
Herculis. Much more modern calculations, however, have it moving
at about 20 kilometers per second not toward Lambda, but more to
the southeast toward, you guessed it, Omicron Her, from which
Lambda stole the proper name, perhaps something of a fair trade.
(Thanks to Joseph Jarrell, who recommended this star.)
Written by Jim Kaler 11/21/08. Return to STARS.