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 named 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. This 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 having a separation distance of about 12.7 billion kilometres. Both stars are quite old compared to our Sun at 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. This binary system was first discovered by Giuseppe Piazzi in 1804, and its distance from Earth was first measured by Friedrich Bessel in 1838.

Two dark companions of unconfirmed masses 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 up to two Earth-like worlds exist in the habitable zones of both stars. If this is true, we should expect highly intelligent and technically advanced civilisations to be present in this star system.

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 located 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 in colour, spectral type DQZ) that is nearing the end of its stellar evolution. The two stars orbit each other in 40.84 years with orbital eccentricity of 0.4, and are separated by 2.4 billion kilometres of presumably empty space.

Nothing special to note about this star system, including the fact that no planets have been detected so far.

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 displaying 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 of mass 2.96 or 3.25 times that of Jupiter and takes 45.2 years to complete one orbit of its star at a distance of 11.55 astronomical units from its star. Looking further afield, we see what appears to be another star named Epsilon Indi B having a separation distance from its companion of approximately 11,600 astronomical units. However, on closer examination it is looking like we have two brown dwarfs (spectral type 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 really be called a planet.

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. This 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 caused by flare ups, and their active surfaces are sources of x-ray emissions. Enough to make intelligent and technically-advanced aliens struggle to take a foothold on an unseen rocky planet. Prospects of life here are limited.

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