61 Cygni

DISTANCE 11.36 light years

MASS A: 0.59 B: 0.5

LUMINOSITY A: 0.153 B: 0.085

RADIUS A: 0.72 B: 0.57

SURFACE TEMPERATURE A: 4,327 K B: 4,177 K

AGE A: 6.1 billion years B: 6.1 billion years

61 Cygni (also known as GJ 820 A/B, Struve 2758, ADS 14636, V1803 Cygni, GCTP 5077.00, and sometimes nicknamed Piazzi's Flying Star or Bessel's Star, but these terms have become obsolete) is located in the constellation Cygnus. It is an orange binary system consisting of a pair of K-type dwarf stars that orbit each other in a period of about 659 years and have a separation distance of about 12.7 billion kilometres of presumably empty space (famous last words). Both stars are quite old compared to our Sun, being either 6.1 or 20 billion years old. Either way, they still have plenty of life in them considering the stars are slightly smaller than our Sun (and thus using up less energy to maintain their nuclear fusion process at their cores). This binary system was first discovered by Giuseppe Piazzi in 1804, and its distance from Earth was first measured by Friedrich Bessel in 1838.

Yep, we were wrong about empty space. Two dark companions with unconfirmed masses of 0.01 and 0.008 relative to our Sun seem to orbit 61 Cygni A (spectral type K5) and 61 Cygni B (spectral type K7) respectively. Other than that, it would not be too surprising if there were up to two Earth-like worlds in the habitable zones of both stars. If this is true, we should expect to find highly intelligent and technologically advanced civilisations in this star system.

Worth a trip for future space travellers looking for surprises in this part of the cosmic neighbourhood.

Procyon

DISTANCE 11.46 light years

MASS A: 1.5 B: 0.602

LUMINOSITY A: 6.93 B: 0.00049

RADIUS A: 2.05 B: 0.12

SURFACE TEMPERATURE A: 6,474 K B: ?

AGE A: 1.87 billion years B: 1.37 billion years

Procyon is a binary star system in the constellation of Canis Minor. It consists of a bright yellow-white subgiant (spectral type F5 IV-V) and a faint white dwarf companion (slightly yellowish of spectral type DQZ) that is nearing the end of its stellar evolution. The two stars orbit each other in 40.84 years with an orbital eccentricity of 0.4, and are separated by 2.4 billion kilometres of again presumably empty space.

There is nothing special about this star system, including the fact that no planets have yet been discovered.

Epsilon Indi

DISTANCE 11.87 light years

MASS A: 0.762 B a: B b:

LUMINOSITY A: 0.22 B a: 0.00002037 B b: 0.00000597

RADIUS A: 0.711 B a: 0.080 B b: 0.083

SURFACE TEMPERATURE A: 4,649 K B a: 1,385 K B b: 1,011 K

Epsilon Indi is located in the southern constellation of Indus. Epsilon Indi A (spectral type K5V with an orange hue on its surface) is believed to have a stable planetary system, including a gas giant planet (currently named Epsilon Indi A b) discovered in 2018 with a mass of 2.96 or 3.25 times that of Jupiter. This large planet takes about 45.2 years to complete an orbit around its star at a distance of 11.55 astronomical units from its star. Looking further afield, we see what appears to be another star called Epsilon Indi B, which is about 11,600 astronomical units away from its stellar companion. On closer inspection, however, it looks as if we have two brown dwarfs (spectral types T1 and T6) orbiting each other, and probably taking 15 years to complete one orbit, although there is talk of the possibility that one of the brown dwarfs should actually be called a planet. A fairly complicated double solar system with many interesting planets and one that could be worth exploring one day.

STRUVE 2398

DISTANCE 11.491 light years

MASS A: 0.334 B: 0.248

LUMINOSITY A: 0.039 B: 0.021

RADIUS A: 0.35 B: 0.27

SURFACE TEMPERATURE A: 3,392 K B: 3,334 K

AGE A: 3 billion years B: 2.4 billion years

STRUVE 2398 is a binary star system located in the northern constellation of Draco. It is a binary red dwarf system (spectral types M4 and M5), both emitting low levels of visible light. They are also a source of variability in their luminosity due to flare ups, and their active surfaces are sources of x-ray emissions. Enough to make it difficult for intelligent and technically-advanced aliens struggle to gain a foothold on an unseen rocky planet. The prospects for life here are limited.

The two stars orbit each other with a period of about 295 years at a distance of about 56 astronomical units.