On the Move with Barnard’s Star and 61 Cygni

Stars may appear static, but they're on the move. Put these two speed demons on your observing list this summer. When you return in a year or two, you'll be pleasantly surprised.

Little Red Corvette

Barnard's Star would be an undistinguished red dwarf in Ophiuchus were it not for its rapid motion across the sky. It measures 1.9 times Jupiter's diameter and lies only 6 light-years from Earth.
Wikimedia, with additions by the author

Last week we visited with mover-and-shaker star Arcturus in Boötes. Despite its great speed, it requires a minimum of a couple decades for us to see the orange giant shift against the more distant background stars in a telescope.

While that might make an excellent very-long-term observing project, most of us would prefer something a smidge more immediate. Fortunately, there are two stars visible this season to accommodate our wishes. The first, Barnard's Star, is a 9.5-magnitude red dwarf in Ophiuchus, just 6 light-years from Earth. That makes it the second closest star to Earth after the Alpha Centauri system.

Discovered by American astronomer E. E. Barnard in 1916, it scoots faster across the sky than any other star in the heavens. Moving at a rate of 10.3″ per year, Barnard's Star covers a quarter degree, or half a full Moon diameter, in a human lifetime.

Easy to find on summer nights

This map shows the sky facing southeast around 10:30 p.m. local time in early June. Barnard's Star is located 1° NW of the 4.8-magnitude star 66 Ophiuchi on the northern fringe of the loose open cluster Melotte 186.
Stellarium

That's plenty fast enough for anyone with a 4-inch or larger telescope to detect its northward movement in a year or two. Barnard's rises high enough for a clear view around 10-10:30 p.m. local time. To find it, first locate 66 Ophiuchi (mag. 4.8), then use a detailed map to star hop ~1° to the northwest, where you'll arrive at the dwarf. You can either photograph the star or pull out a pencil and make a sketch of its current position. Next June, when you return to the field, sketch it again.

Inching north by the year

Close-up map showing Barnard's Star's northward march every 5 years from 2015 to 2030. Your guide star, 66 Ophiuchi, is at lower left. Stars are numbered with magnitudes and a 15′ scale bar is at lower right. North is up. The line through the two 12th-magnitude stars will help you gauge Barnard's movement. Click for larger map.
Chris Marriott's SkyMap

Compare Barnard's position to the magnitude 11.9 and 11.5 stars or watch for it to form a straight line with a pair of 12th-magnitude stars to its northwest between now and 2020.

Our second featured star, 61 Cygni, is one of summer's best and brightest double stars —  a gorgeous pair of orange-red dwarfs (magnitudes 5.2 and 6.0) located 11.4 light-years away in Cygnus.

Got ya' cornered

61 Cygni shines with a combined magnitude of 6.2 and forms the fourth corner of a parallelogram made with Deneb, Gamma, and Epsilon Cygni. It rises into easy view around 11 p.m. in early June and 9 p.m. at the end of the month.
Sky & Telescope

61 Cygni has an equally colorful history. In 1792, Italian astronomer Giuseppe Piazzi observed the star and noticed it had moved against the starry background to the tune of more than 3′ from the position noted in observations made 40 years earlier. When word of this fleet star got out, astronomers nicknamed it "Piazzi's Flying Star." Nine years later, Piazzi would discover Ceres, the first asteroid and current focus of NASA's Dawn Mission.

61 Cygni parts company

Medium-magnification view of the double star 61 Cygni. The brighter component, 61 Cygni A, lies just 15″ from a 10.7-magnitude field star.
Sky & Telescope

By the 1830s, star positions could be measured with enough precision that astronomers began competing to be the first to measure a star's annual parallax or displacement against the distant background stars due to Earth's revolution around the Sun. Friedrich Bessel chose 61 Cygni, assuming it to be nearby due to its large proper motion of 5″ per year. Bingo! Working at his limit, he saw the star shift by a mere 0.314″, yielding a distance of 10.3 light-years, close to the current value of 11.4 light-years.

Star on the move

Detailed chart showing 61 Cygni's departure from the 10.7 magnitude star beginning August 2014 and continuing through August 2024. Use high power — 200x or more — to make your sketch. The higher the magnification, the easier motion will be to discern when you return.
Sky & Telescope

61 Cygni A, the brighter of the pair, happens to lie only 15″ from a 10.7 magnitude star this summer. Each year its distance from the star increases by an additional 5″ With high magnification you might be able to see it slide northeast in as little as year. The maps above will help you locate the star and track its motion over the next 9 years.

There are several other stars with high proper motion — Groombridge 1830 in Ursa Major (7″ per year), Kapteyn's Star in Pictor (8.7″ per year), and Lacaille 9352 in Piscis Austrinus (6.9″ a year). We'll pay them all a visit in future installments.

Seeing a star move in one's lifetime allows us to peer into the inner workings of the Milky Way galaxy. We experience firsthand the illusory nature of the "static" sky.  All is in flux as stars stream about the galactic core. Today's constellations will eventually slip away to be replaced by new ones created by distant descendants.


Looking for 61 Cygni? The Sky & Telescope Pocket Sky Atlas can help you with that!

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Bob King

About Bob King

Amateur astronomer since childhood and long-time member of the American Association of Variable Star Observers (AAVSO), Bob King also teaches community education astronomy and writes the blog Astro Bob. The universe invites us on an adventure every single night. All we need do is look up. Check out my forthcoming book "Night Sky with the Naked Eye" (on Amazon and BN) about all the great things you can see at night without any special equipment.

2 thoughts on “On the Move with Barnard’s Star and 61 Cygni

  1. Bob-dBouncier

    “The first, Barnard’s Star, is a 9.5-magnitude red dwarf in Ophiuchus, just 6 light-years from Earth. That makes it the second closest star to Earth after the Alpha Centauri system. ”

    Of course, you mean the THIRD closest star to earth, after Alpha Centauri and the Sun. 😉

    1. jsheff

      I think you’re forgetting that Alpha Centauri is a triple-star system. The Sun, Alpha Centauri A, Alpha Centauri B, and Alpha Centauri C (Proxima) are all closer to us than Barnard’s star. That puts the latter into 5th place. But, as Bob wrote, it’s the second closest after the Alpha Centauri system.

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