Most of us are
familiar with the Seven Sisters, but have you met their brothers?
Learn how to find more Pleiades than first meet the eye.
Pleiades star cluster is located in Taurus and dominated by
hot blue stars that formed within the past 100 million years.
(photo by Bob King)
They're called the Seven Sisters, but can you see all seven?
Better known as the Pleiades
star cluster, this lovely group in the shape of a miniature
Big Dipper enchants the eye on autumn nights. I love watching the
Pleiades. Theres nothing quite like it in the heavens. Most
stars are single and separate from each other, but the Pleiades
packs more than a handful into a compact bunch that stands apart
from nearly everything else in the sky.
The Pleiades is one of brightest star clusters in the sky. It
contains some 3,000 stars and lies about 444
light-years from Earth. Side to side the group spans 13 light-years,
or about halfway from Earth to the bright star Vega. Like a school
of fish, its members move together as a gravitationally-bound swarm
In late October the group clears the treetops around 9:30 p.m.
local time and remains visible the rest of the night.
Pleiades (upper left) rises for easy viewing around 9:30 p.m.
local time in late October. A distinctive knot of naked-eye
stars, the cluster catches our eye whenever it's in the sky.
(graphic by Bob King)
When asked how many stars they see in the cluster, beginning
observers will usually say five. That's what most of us see at a
glance, and it makes sense because the five brightest Pleiades
Alcyone, Atlas, Electra, Maia, and Merope range from magnitude
2.9 to 4.2, well within the grasp of most observers from a reasonably
dark sky site. But can we do better?
brighter of the Pleiades stars with names are shown along
with their magnitudes. After spotting the five easy ones,
try Taygeta and then Pleione to make seven. (photo by John
According to Agnes
Clerke, a late 19th-century/early 20th-century astronomer and
writer: "Carrington and Denning (British amateur astronomers)
counted fourteen." Robert Burnham, in his 3-volume Celestial
Handbook, writes that "there are at least 20 stars in the group
which might be glimpsed under the finest conditions."
Wow! Really? Let's start with the next two easier targets. Extend
a line from Alcyone through Maia to find Taygeta. Most amateur astronomers
can spot this one with ease. A touch of averted vision, a technique
of looking "around" the object of interest instead of
directly at it, should make this a snap. It's the next one, Pleione,
that gives many observers trouble. Not only is it dimmer, but the
star nestles against brighter Atlas. For me, seeing it requires
good dark adaption, patience, and a mix of averted and direct vision.
view shows the bright central cluster plus additional fainter
members and several unrelated but helpful guide stars nearby
along with their magnitudes. In addition to the core cluster,
stars circled in red are Pleiades members. Click to enlarge.
That's seven. Ready to move on to the challenge round? We now
go deep, pinging stars ranging from magnitude 5.4 to the inky sky
limit of 6.5. Fully dark-adapted eyes and a moonless, transparent
sky are musts. The dim Asterope duo and Celaeno beckon near the
Pleiades core, but that's the problem. They're so close to other
member stars, they're difficult to distinguish on their own.
I've caught tantalizing hints of both with averted vision when
the cluster's high in the sky. Asterope presents a special challenge
as the pair is separated by only 2.4 arc minutes more than
one arc minute closer than the famous Double-Double Epsilon
Lyrae, itself no easy split, and nearly two magnitudes fainter.
At best, you might see them as a single elongated star.
Once we move beyond the distraction of the central cluster,
hunting gets easier. The magnitude 5.4 star (HD 23753) below the
"dipper handle" is relatively easy, but the 6.0 (HD 23950)
will place greater demands on your visual cortex. 18 Tauri likewise
is relatively easy with averted vision, but beware of the 6.1 and
6.5 members south of Atlas. They'll push your vision to the limit.
But that's where you want to be, right? Limits tempt us to go that
the Pleiades cluster by facing east and looking 2-3 fists
above the eastern horizon in late October around 10 p.m. local
time. Source: Stellarium
By the way, I keep a pair of binoculars at my side to not only
verify Pleiades star sightings, but to help me know just where to
look if I'm having difficulty finding a star. They also provide
a splendid and visually refreshing look at the cluster after straining
to see its fainter members.
So let's add up our starry gems. The bright five plus two not-so-difficult
core cluster stars make seven. Add in seven more faint hanger-ons
(we'll count Asterope as one) and you've got 14. Not bad, not bad