Sky & Telescope - September 2023 - 45

Evenings with the Stars by Fred Schaaf
Little Gem
Delphinus
The starry Dolphin frolics in
the shallows of the Summer
Milky Way.
T
he famous Summer Triangle formed
by Vega, Altair, and Deneb is at its
early-evening highest as summer ends.
Impressive as that big, bright asterism
is, I often find myself drawn to a pair of
small constellations that accompany the
Triangle across the sky: Delphinus, the
Dolphin, and Sagitta, the Arrow. This
time out, let's give the Dolphin its due.
Although Delphinus can be difficult
to see in light-polluted conditions,
this little gem of a constellation really
stands out in a clear, dark country sky.
And " gem " is an especially good descriptor
for Delphinus - its four main stars
are arranged in an elongated diamond
shape. The quartet of Alpha (α), Beta
(β), Gamma (γ), and Delta (δ) serves as
the Dolphin's body, while an extension
formed by Epsilon (ε) provides the tail.
These five stars shine at magnitudes 3.8,
3.6, 4.4, 4.4, and 4.0, respectively. You'll
note that less than a full magnitude
separates the brightest from the faintest
- something that, in my view, adds to
the constellation's charm.
Delphinus includes five additional
stars bearing Greek letters, but they
don't attract much attention because
they're relatively faint and aren't part of
the main Dolphin pattern. The quintet
of " bonus " stars are, Zeta (ζ), Eta (η),
Theta (θ), Iota (ι), and Kappa (κ). Brightest
of the bunch is 4.6-magnitude Zeta,
and 5.7-magnitude Theta is faintest.
But which of Delphinus's stars
stands out as the most interesting? My
pick is Gamma Delphini, the Dolphin's
northeast-pointing nose. However, you
need a telescope to see why: Gamma is
a beautiful double whose components at
pLEAPING DOLPHIN The little constellation of Delphinus lies just east of the bright swath of
Milky Way running through Aquila, north into Cygnus. During September, the entire region is well
placed for early-evening viewing. (North is to the upper-left in this photo.)
magnitudes 4.4 and 5.0 are 8.9″ apart.
In addition to " gem, " the other adjective
I used for Delphinus was " small. "
Of the 88 officially recognized constellations,
Delphinus ranks 69th in terms
of area. But even that placement slightly
flatters our aquatic friend - from nose
to tail it spans less than 6°. Thankfully,
the Dolphin is bracketed by the even
smaller figure of Sagitta and the tiny
(ranking #87!) and indistinct constellation
of Equuleus, the Little Horse.
Under good sky conditions, Delphinus
appears to be leaping out of the
dark waters east of the bright summer
Milky Way. The image of a frolicking
dolphin calls to mind the Greek
myth most commonly connected with
Delphinus. In this ancient story, the
great poet and musician Arion was
returning on a ship from a musical
competition with a small fortune in
winnings, which the crew plotted to get
their greedy hands on. As the sailors
approached him menacingly, Arion
pleaded to play one last song. While his
music enchanted nearby dolphins, it
didn't move the evil hearts of the crew,
and Arion threw himself into the sea
to escape their murderous clutches. The
thieves sailed onward to Arion's home
city, where they claimed the musician
had fallen overboard and drowned in
a tragic accident. What they didn't
realize was that one of the dolphins
listening to Arion's music had rescued
him and delivered him home ahead
of the thieves. It's fun to imagine the
looks of shock on their faces when they
saw Arion alive and well just before
they were carried off to face their just
punishment.
Only Alpha and Beta Delphini have
proper names. However - as moving
as the story of Arion and the dolphin
is - their names didn't originate in
myth or legend. Sualocin (Alpha) and
Rotanev (Beta) first started appearing
in 19th-century star atlases, but scholars
initially couldn't figure out their
meaning or derivation. It turns out that
the astronomer Giuseppe Piazzi had
mischievously created them by reversing
the letters of his assistant's first and last
name: Niccolò Cacciatore. In English
this translates to Nicholas Hunter,
which in Latin is Nicolaus Venator -
hence Sualocin and Rotanev.
¢ FRED SCHAAF's favorite view of Delphinus
came in 1976 when Comet West
visited the constellation.
sk yand tele scope .o r g * SEPTEMBER 2023 45
ALAN DYER

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