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Object of the Week, September 4, 2016 - Barnard's Star
Barnard’s Star
Highest proper motion star
RA: 17 hours 57 minutes 48 seconds (approximately)
DEC: +4 degrees 42 minutes 36 seconds (approximately)
Magnitude: 9.5
It’s just a star, and a small one at that.
Barnard’s Star is a faint red dwarf in northeast Ophiuchus that's unremarkable except that it has the largest known proper motion across the sky. It takes just 351 years to move one degree across the sky. It’s only 5.96 light years away, making it the 5th closest star to Earth, which is another way of stating that after the Sun and the three stars that make up the Alpha Centauri system it’s the next closet. At least that we know of.
E. E. Barnard discovered it in 1916 by comparing photographs taken in 1894 and 1916, and then finding it on a photo taken by E. Pickering in 1888. The proper motion of Barnard’s star is a combination of its closeness and its intrinsic high velocity through space. In about 8000 years it will pass less than 4 light years from us.
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I made my first observation of this magnitude 9.5 star in 1983 soon after buying the three volume set of Burnham’s Celestial Handbook. Using a finder chart from Burnham’s I was able to track it down fairly easily and then noted its position on a line marking the stars’ proper motion from 1880 to 2040. That chart is on page 1252 of volume two, and page 1253 has a negative photo showing over a degree of sky around the star, making location that much easier. A distinctive “V” shaped asterism helps guide the way.
And then I didn’t make another observation for 20 years.
I thought about it from time to time though – it’s located less than a degree from 66 Ophiuchi, a magnitude 4.8 star, and well placed for most of the spring and summer – but somehow I didn’t swing my telescope over to track it down again until June 4, 2003. I sketched the field and couldn’t wait to compare it to my original observation to see how much it had moved in 20 years. And then I couldn’t find my notes. Argh!
A few days later I remembered that I’d marked its position on the Burnham’s chart, and finding that little 1983 mark was about as exciting as an original discovery. It was with surpassing pleasure that I marked my 2003 observation on the chart.
I was exhilarated - it had moved a good 12 mm on the scale of the page 1252 chart! Being able to chart the actual motion of a star through space over the course of 20 years gave me a strong sensation of the starry sky in motion. I’ve known intellectually that stars swirl through the Milky Way, but observing the proper motion of Barnard’s Star gave me a direct connection to this reality.
I soon found my original notes, which happened to be from June 4, 1983, exactly 20 years before my latest observation. How’s that for a nifty convergence?
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Above is a current scan of the Burnham’s Celestial Handbook chart (page 1252) where I’ve plotted my Barnard’s Star observations. Note the 2006, 2013 and 2016 (red arrow) marks. Interestingly, all but my 2006 observation was made on a June 4th.
These are deeply satisfying observations and I hope everyone reading this is motivated to keep track of Barnard’s for themselves. I put it on the 2016 Oregon Star Party advanced observing list just so I could encourage more people to start tracking it themselves.
Out of curiosity I looked up June 4, 2033, the 50th anniversary of my first observation - it’s on a Saturday. Even though I will have observed Barnard’s Star a few more times by then, I look forward to that fine and future night. With my 77 year old hands I’ll mark its position on page 1252 of Burnham’s, about 30 mm above the 1983 mark, noting one more tick of the Milky Way’s galactic clock.
