We now leave the
world of the impossible (DX Cancri) and the infuriatingly frustrating (Wolf
359), and come to a target that will neither cause anyone to tear his hair out,
nor tempt the more gullible among us to buy just one more ridiculously
expensive eyepiece (yes, I’ve done that!), having convinced themselves that
“this is all that is lacking” in the quest for observational nirvana. Seeing Barnard’s Star should not prove
beyond the means of anyone possessing a decently-sized telescope. Recognizing it amongst the many stars in
one’s field of view will of course be another matter entirely.
The
first great advantage we possess in tracking down Barnard’s Star is its
surroundings. There are easily identifiable markers in the immediate vicinity
that will make at least the first stages of our search relatively easy. Off to
the right, the bright, naked eye stars Beta and Gamma Ophiuchi (magnitudes 2.7
and 3.7, respectively) point us to the relevant area of the sky. These two
stars could hardly be more different from each other. Beta Ophiuchi (also known
by the Arabic name Cebalrai, meaning “Shepherd Dog”) is a star only slightly
more massive than our own Sun, yet has nevertheless raced through its early
stages of stellar evolution, and at age 3.8 billion years old is in the process
of converting itself into a red giant. It currently shines out with a
luminosity of 63 Suns. Meanwhile, its visually close neighbor (and they
actually are quite close to each other, being only about 15 ly apart), Gamma
Ophiuchi, is practically a newborn, being less than 200 million years old. But
with three times the mass of the Sun, it will likely catch up with and overtake
its more mature neighbor. This might lead one to imagine the pleasant prospect
of future astronomers being treated to side-by-side planetary nebulas as the
two stars simultaneously blow off their gaseous outer layers, but alas, their
differing orbits about the galactic center will have pulled them far apart by
such time.
And speaking of young stars, a mere field
of view away (using a wide field eyepiece) to the northwest from Beta Ophiuchi
is the lovely open star cluster IC 4665. The components of this must-see object
were born from interstellar gas and dust less than 40 million years ago! When
you view IC 4665, you are seeing a true stellar nursery.
So much for the right hand side of our
initial search area.
Off to the left is an asterism known as
Poniatowski’s Bull.
This distinctive grouping, bearing a striking resemblance
to the only slightly larger Hyades, was once a constellation in its own right.
The Polish-Lithuanian astronomer and Jesuit priest Marcin Odlanicki Poczobutt
created the constellation Taurus Poniatovii in 1777 out of leftovers from the
defunct constellation “Tigris River” in honor of the then King of Poland,
Stanislaus Poniatowski.
But in a case of celestial irony, Poszobutt’s creation
scarcely outlived the nation of its honoree. For just as the Kingdom of Poland
was being ruthlessly partitioned in the late 18th Century between its more
powerful neighbors Russia, Austria-Hungary, and Prussia, Taurus Poniatovii was
in like manner being hacked apart and divvied up between Ophiuchus, Aquila, and
Serpens Cauda.
So far, we’ve had it easy. Under dark,
moonless skies, all the stars so far mentioned are naked eye. And even from
light polluted suburban Maryland, binoculars at most would have sufficed to
this point. But “Here is where one must put aside all division of spirit, and
gather your soul against all cowardice” (Dante, Divine comedy, Canto III,
14-15). For in truth, Barnard’s Star has more readily recognizable signposts pointing
toward it than for any star we’ve yet encountered.
The easiest way I know of to spot
Barnard’s Star is to put 66 Ophiuchi at one edge of your field of view, and
look for three approximately 7th magnitude stars arranged in a rough line
pointing straight at that bright star (see above image). They form the shaft of
an imaginary arrow with 66 Ophiuchi as the tip of the arrowhead. Focus your
attention on those three stars, and look somewhat closer to 66 Ophiuchi and a
bit to one side (see image), and voila! There is Barnard’s Star.
(Note: final two images are as mirror-imaged, to match the view one would see using a refractor with a diagonal.)
Keep in mind as you observe this astonishingly faint object, that you are looking at the closest thing you'll ever see outside of our own Solar System! It never ceases to amaze me that all the brighter stars up there are so much further away.
No comments:
Post a Comment