61 Cygni A is an orange dwarf in Cygnus, and with its companion the first star system whose distance was ever measured, by Friedrich Bessel.
At a glance
| type | orange star (class K) |
|---|---|
| distance from the Sun | 11.4 light-years (3.5 pc) |
| its light left it | 11.4 years ago |
| luminosity | 0.153 × the Sun |
| radius | 0.67 × the Sun |
| surface temperature | 4,530 K |
Read off the piece’s own catalogue, the same values it draws with.
About 61 Cygni A
61 Cygni A is an orange dwarf, smaller and cooler than the Sun, paired with 61 Cygni B, a slightly fainter orange dwarf, on a wide orbit that takes many human lifetimes to complete. Under dark skies the pair can just be seen with the naked eye as a single faint star in Cygnus; a small telescope splits it.
It earned its place in history because it moves quickly across the sky. Giuseppe Piazzi noticed that motion and called it the flying star, and a large motion suggested a close star. Friedrich Bessel chose it for that reason and, by measuring its tiny yearly shift against more distant stars, obtained the first reliable distance to any star. It showed for the first time how vast the gulfs between stars are.
Both stars show cycles of magnetic activity much like the Sun’s spot cycle, and they have been followed for long enough that those cycles are well recorded. They are among the nearest stars to which the Sun can be compared in this way, star against star.
What you see in the piece
Fly to it and you find an orange disc. In HUMAN EYE it is a faint point in Cygnus, at the edge of what the eye can see from a dark site.
Questions
Which star’s distance was measured first?
61 Cygni A and 61 Cygni B: Friedrich Bessel measured their parallax, the first reliable distance to a star. They lie 11.4 light-years (3.5 pc) from the Sun.
Can you see 61 Cygni A with the naked eye?
Only under dark skies. It is an orange star (class K) with a luminosity of 0.153 × the Sun.