Sand and Stars

Barnard’s Star and Poniatowski’s Bull

Taurus P asterism
Poniatowski’s Bull asterism in Ophiuchus. IAU Ophiuchus chart

21 Jun 2017

My favourite asterism lies in Ophiuchus – the obsolete constellation, Taurus Poniatowski (Poniatowski’s Bull).

It’s a striking sight in a dark night sky – the V-shaped head of the little bull is outlined by the stars 66 Ophiuchi (mag 4.6), 67 (mag 4.0), 68 (mag 4.4) and 70 (mag 4.0), and fainter stars extend the V further north.

Naked eye, it really does resemble the real Taurus. And the little horned beast is a gorgeous sight in binoculars – its anchor stars are gloriously bright, and the background is splashed with  a multitude of fainter stars that straggle off the western edge of the Milky Way.

The constellation Taurus Poniatowski was placed in the skies in 1777 by the Polish-Lithuanian astronomer Marcin Poczobut (1728–1810), director of the Royal Observatory at Vilna (now Vilnius, Lithuania). He invented it to honour his king, Stanisław August Poniatowski, who was monarch of both Poland and Lithuania. The king was a noted patron of the arts and sciences, and the bull was a feature of his family’s coat of arms.

Poniatowski’s Bull pictured in the Uranographia of Johann Bode (1801)
Poniatowski’s Bull pictured in the Uranographia of Johann Bode (1801)

As the inimitable Admiral Smyth recorded in his famous book, Cycle of Celestial Objects, “It is between the shoulder of Ophiuchus and the Eagle, where some stars form the letter V, and from a fancied resemblance to the zodiac bull and the Hyades, became anouther Taurus. Poczobut was content with seven component stars, but Bode has scraped together no fewer than 80.”

But alas, like a lot of small, faint constellations created by 17th and 18th century astronomers, this little constellation did not survive. Along with such beguiling constellations as Cerberus, the three-headed monster who guarded the gates of Hades, Noctua, the Owl, and Globus Aerostaticus, the Hot-Air Balloon, the little bull was put out to pasture and its stars are now part of Ophiuchus and Serpens Cauda.

However, although Taurus Poniatowski was demolished as a constellation, the name of the little asterism remains. But whenever I look at it, I don’t see Poniatowski’s bull; I see that most enchanting of little bulls, Ferdinand.

Written by Munro Leaf and illustrated by Robert Lawson in 1936, Ferdinand the Bull is surely one of the most enchanting children’s books ever written…

“Once upon a time in Spain there was a little bull and his name was Ferdinand. All the other little bulls he lived with would run and jump and butt their heads together, but not Ferdinand. He liked to sit just quietly and smell the flowers. He had a favorite spot out in the pasture under a cork tree. It was his favorite tree and he would sit in its shade all day and smell the flowers….”

Ferdinand the Bull

To me, the celestial Ferdinand is doing just that, wandering serenely through the glittering star field towards his cork tree, and enjoying the gorgeous sprays of stars along the way…

…The vast loose open cluster Mel 186 which encompasses the little bull’s entire head, the dazzling open cluster, IC 4665, lying just one degree northeast of beta Ophiuchi; the double star, 70 Ophiuchi (which not only is one of the sky’s most gorgeously coloured doubles, but one whose stars revolve about their common center of gravity in just 88 years – making this one of the few double stars you can see move appreciably during your lifetime); the faint little globular cluster, NGC 6426; the lovely background field sprinkled with stars.

However, most wonderful of all the stars in Ferdinand’s beautiful field is one of the most famous stars in the sky – Barnard’s Star.

Barnard’s Star is classified as an M5 V main sequence star. Like all red dwarfs, it is intrinsically a very faint object, its absolute magnitude of +13.4 corresponding to a luminosity of a mere 1,2500 Sun. Thus this tiny dim and dull-red star (apparent magnitude +9.5) may not be much to look at… but it certainly invites scrutiny because it has the highest proper motion (or apparent motion across the sky) of any charted star in the heavens… not to mention it is also the second closest star to the Sun, lying about 6.0 light years away, about 1.7 light years further than Alpha Centauri (if you take Alpha Centauri as a single system).

The incomparable E.E. Barnard first noticed the star’s nature in 1916 when comparing plates made in 1894 and 1916. He found that its annual motion is 10.29 arcseconds in a direction almost due north – meaning that it covers a quarter degree, or half a full Moon diameter, in a human lifetime.

(Were I able to time travel back and give my younger self some advice it would be: “Plot Barnard’s Star’s movement across the sky for the duration of your life.” What a tremendous life-long project to watch this little star tear across the sky at the break-neck pace of 10 arcseconds per year!)

These two images of the same area of the sky, taken about 50 years apart show the proper motion of Barnard's Star (the bright star near the bottom of the left image, and the top of the right image). The left image was taken in the 1950s as part of the Palomar Observatory Sky Survey; the right image recently, as part of a second POSS. Image credit POSS1, POSS2, Digitized Sky Survey
Image credit POSS1, POSS2, Digitized Sky Survey

These two images of the same area of the sky, taken about 50 years apart show the proper motion of Barnard’s Star (the bright star near the bottom of the left image, and the top of the right image). The left image was taken in the 1950s as part of the Palomar Observatory Sky Survey; the right image recently, as part of a second POSS.

Last night, I examined this wonderful little star, after which I explored the star field through which the peaceable little bull Ferdinand is strolling.


16″ f/5 Dobs at magnifications of 70x, 150x, 228x, and 333x 

10×50 binoculars


Barnard’s Star (Gliese 699)

RA 08 10 11.9   Dec -49 14 00   Mag 4.7

Barnard’s star. DSS2 image

It is a superb observing experience to see this little star; a dim red droplet of stellar light lying in a beautiful field of stars. I sketched the star’s current position in relation to the nearby field stars as accurately as possible. Next year, I plan on returning to the field in order to sketch it again and hopefully if I sketched it accurately enough last night, see motion in just a year. And astronomy being all about patience, perseverance and time… I’ll return the following year.. and the following…

After all, Barnard’s dim little red dwarf presents us with something denied us in our short lives… the rare opportunity to witness the grand cycling of stars around the galaxy.

The it was off to look at a couple of the gorgeous doubles that make up his face:

70 Ophiuchi – Double Star

RA 08 10 11.9   Dec -49 14 0   PA 139°   Sep 4.7   m1 4.2  m2 6.2  

DSS image
70 Ophiuchi. DSS image

What a gorgeous sight! Certainly one of the most beautiful doubles. The primary is a glorious golden colour; its smaller companion an equally glorious coppery golden colour.  Absolutely stunning against the velvety black sky.

67 Ophiuchi – Double Star

RA 18 1.8    Dec -49 14 00   PA 142°   Sep 54.3   m1 4.0  m2 8.1  

DSS image
67 Ophiuchi. DSS image

Another beauty! The primary is a bright lemony-yellow star; its companion a small silvery-grey dot beside it.

IC 4665 – Open Cluster

RA 17 46 12.0    Dec +05 43 00   Mag 4.2   Size 70

DSS image
IC 4665. DSS image

Visible to the naked eyeas a hazy patch of starlight, the 10×50 binoculars show NGC 4665 as a conspicuous, loose cluster of a few brightish stars evenly spread over a roughly one degree circular area and embedded in the nebulous glow of unresolved starlight. The cluster stands out beautifully against the starry background. A very attractive sight! At very low magnification in the telescope, it pretty much loses its open cluster aspect but the centre of the cluster has a lovely chain of blue-white stars running across the field with a small arc of stars just below it. There are a few wide doubles and a nice Y-shaped asterism in the northwestern area of the cluster.

CR 350 – Open Cluster

RA 17 48 12.0   Dec +01 8 00   Mag 6.1   Size 40

DSS image
CR 350. DSS image

I couldn’t pick this cluster up in the 10×50 binoculars, and at very low power in the telescope, apart from a few brightish stars, it is so loose that it is impossible to tell which stars are members of the open cluster. The few brightish stars I suspect are members make a widely-spaced loopy curve in the sky.

Mel 186 – Open Cluster

RA 18 01 06.0   Dec +02 54 00   Mag 3.0   Size 240

The centre of the vast Mel 186 DSS image
The centre of the vast Mel 186. DSS image

The open cluster Mel 186 is enormous and is centered on 67 Ophiuchi, thus encompassing the whole of the little bull’s head. The cluster’s true nature is revealed in binoculars – mine showed a number of little sparklers sprinkled liberally across the field, and of course the lovely bright stars that outline the little bull’s head. For one tremendously exciting moment I thought that I had discovered a new open cluster…  to the northeast of 70 Oph is a nebulous glow with a few little stars scattered within it. But alas, not so: my Uranometeria All Sky charts the stars as being unrelated, although they are in the Mel 186 field.

NGC 6426 – Globular Cluster

RA 17 44 54.7    Dec +03 10 13    Mag 10.9   B * V m 15.2   HB V m 18.1   Size 4.2   

DSS image
NGC 6426. DSS image

Described by Charles Messier as a “nebula without stars”, that is exactly what this globular cluster looks at low power – a faint, nebulous, round smudge of dim grey light. At high power the nebulous glow becomes a hazy glow, but not a single stars is even close to being resolved. It shows diffuse edges and is weakly concentrated toward its centre.

A lovely little object on which to end this meander around this charming obsolete little bull.

Copyright © Susan Young 2017