Kapteyn’s Star is an ancient red dwarf in Pictor, a visitor from the Galaxy’s halo passing through the disc, and the second-fastest star across our sky.
At a glance
| type | red dwarf (class M) |
|---|---|
| distance from the Sun | 12.8 light-years (3.93 pc) |
| its light left it | 12.8 years ago |
| luminosity | 0.0119 × the Sun |
| radius | 0.29 × the Sun |
| surface temperature | 3,570 K |
Read off the piece’s own catalogue, the same values it draws with.
About Kapteyn's Star
Kapteyn’s Star is a red dwarf, too faint for the naked eye but within reach of binoculars. Jacobus Kapteyn noticed its large motion while working on a great photographic catalogue of the southern sky, and only Barnard’s Star crosses the sky faster.
That motion has a deeper cause. The star is very old and poor in heavy elements, and it orbits the Galaxy on a path quite unlike the Sun’s, travelling against the rotation of the disc. It belongs to the halo, the old population of stars that swarms around the Milky Way, and is only passing through our neighbourhood.
What you see in the piece
Fly to it and you find an orange-red disc, with the planets still listed for it in planet catalogues drawn on their orbits, disputed as they are. In HUMAN EYE nothing shows in this part of Pictor.
Measured or modelled
One proposal links it to the stars of Omega Centauri, possibly the remains of a dwarf galaxy; planets once announced around it are now widely attributed to the star’s own activity.
Questions
Why does Kapteyn’s Star move so fast?
It is a halo star on an orbit that runs against the Galaxy’s rotation, and it is close, 12.8 light-years (3.93 pc) away.