11/20/2018 – Ephemeris – Barnard’s Star has a planet

Ephemeris for Tuesday, November 20th. The Sun will rise at 7:46. It’ll be up for 9 hours and 23 minutes, setting at 5:10. The Moon, 3 days before full, will set at 5:37 tomorrow morning.

One of the most fascinating stars in the sky is Barnard’s Runaway Star. That’s how I first knew it. It’s now simply Barnard’s Star. It has the largest motion of any star across the sky (proper motion) of 10.3 arcseconds per year. That’s about the current width of Mars right now in telescopes. The Sun and Moon are about eighteen hundred arcseconds in diameter. It was announced last week, that a planet has been discovered orbiting that star. The planet designated with a lower case b orbits the red dwarf star at a distance comparable to Mercury in our solar system with a period of 233 days. It is three and a quarter times the Earth’s mass. It was found because it changes the velocity of the stars’ approach by the human walking speed in those 233 days.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Barnard Star’s proper motion from 1985 to 2005. Credit Steve Quirk.

I recall back in the 1960’s astronomer Peter van de Kamp announced the discovery of a planet around Barnard’s Star.  His technique was to spot little wiggles in the star’s path through the sky.  Current methods to detect wiggles of the star use the Doppler method  detecting the tiny change in the star’s radial velocity towards or away from us.  Barnard’s Star b does not fit what van de Camp thought he detected.

The star gets its name from Edward Emerson Barnard ( 1857-1923) who discovered the star’s rapid proper motion. 

On a local note Barnard’s great photographic work A Photographic Atlas of Selected Regions of the Milky Way was republished by my friend Gerold O. Dobek, Professor of Astronomy, Northwestern Michigan College and Director of its Joseph H. Rogers Observatory.