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61 Cygni A
Details
61 Cygni A is a nearby orange dwarf star in one of the sky’s most famous binary systems. The 61 Cygni pair became the first stellar system with a measured parallax, and 61 Cygni A is also a standard reference star for the K5 V spectral class.
61 Cygni A matters because it belongs to one of the systems that changed astronomy from educated guessing into measurement. As part of the 61 Cygni pair, it was central to the first successful stellar parallax result, which meant that distance to another star could finally be determined directly rather than inferred through speculation. That historical role gives this otherwise modest-looking star an outsized importance.
What makes 61 Cygni A especially effective in that role is that it is not an extreme star. It is a nearby K-type dwarf: cooler, smaller, and dimmer than the Sun, but stable and close enough to become an excellent reference point. In that sense, 61 Cygni A helped astronomy not by being spectacular, but by being measurable. It turned nearby stellar space into something that could be mapped with confidence.
That is why 61 Cygni A matters on this scale. It reminds you that progress in astronomy does not come only from the strangest objects. Sometimes it comes from a nearby, physically ordinary star that lets the geometry of the universe become real. 61 Cygni A is important because it helped make stellar distance a fact instead of a guess.
343,571km
Visual creditscaleofspace.org / CC BY-NC 4.0
Key facts
- Category
- Stars
- Object class
- K-type main-sequence star
- Mass
- ~0.70 solar masses
- Temperature
- ~4,545 K surface
- Scale fact
- 925,000 kmdiameter
- Estimated age
- ~6 billion years
- Composition
- Hydrogen and helium
Scale context
Where 61 Cygni A sits on the full axis
By size on the journey, 61 Cygni A sits between Proxima Centauri and Epsilon Eridani. The band below compares 61 Cygni A with nearby K-type main-sequence star objects so the size jump stays easy to read.
Shared physical scale
669,500km
Together, these objects make the size change around 61 Cygni A easy to compare at a glance.
Between the smallest and the largest, perspective is everything.
About
Scale of Space is a scroll-based journey through the universe, placing objects on a single logarithmic scale so you can compare size across an unbroken range.
Guides turn parts of that scale into curated essays, while focused views let you explore the same range through specific groups of objects.