---
title: "V639 Cas"
url: "https://spacecatalog.org/object/hd-225094"
release: "DR1"
licence: "CC-BY-SA-4.0"
citation: "SpaceCatalog. V639 Cas [catalogue entry]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/hd-225094"
---

# V639 Cas

V639 Cas is a B2.9Iab blue-white supergiant in the constellation [Cassiopeia](https://spacecatalog.org/constellation/cassiopeia), 2490 ly from Earth, shining at apparent magnitude 6.24 (V). Other catalogues list it as HD 225094, HIP 274 and HR 9097.

## At a glance

- **WHAT IT IS:** Blue-white supergiant
- **HOW FAR:** 2490 ly — The light arriving now left it that long ago.
- **HOW BRIGHT (V):** 6.24 — Bright enough for the naked eye, under a sky dark enough.
- **WHERE TO LOOK:** [Cassiopeia](https://spacecatalog.org/constellation/cassiopeia) — The patch of sky it sits in, as seen from Earth.

## Properties

| Quantity | Value |
| --- | --- |
| CLASS | B2.9Iab blue-white supergiant |
| DISTANCE FROM EARTH | 2490 ly — by parallax |
| APPARENT MAGNITUDE (V) | 6.24 |
| ABSOLUTE MAGNITUDE (V) | −3.17 |
| CONSTELLATION | Cassiopeia |
| RIGHT ASCENSION (J2000) | 00h 03m 25.7s |
| DECLINATION (J2000) | +63° 38′ 25.9″ |

## Catalogue data

### WHAT KIND OF THING IT IS

What the object is in itself, rather than how it happens to look from here.

| Field | Value |
| --- | --- |
| Spectral type | B2.9Iab |
| Surface temperature | 20 450 K |
| Luminosity (visual) | 1620.32 L☉ |
| Surface gravity (log g) | 2.59 |
| Variability | Alpha Cygni pulsating supergiant |
| Variability type (GCVS) | ACYG |

### HOW BRIGHT IT IS

What the light adds up to, measured through one filter at a time. A magnitude is a brightness on a backwards scale — the smaller the number, the brighter the object.

| Field | Value |
| --- | --- |
| Colour index (B−V) | 0.332 |
| Variable magnitude, brightest | 6.21 |
| Variable magnitude, faintest | 6.29 |

### WHERE IT IS AND HOW IT MOVES

Position, motion across the sky and the size it covers on it. These are measurements of the object as seen from here, so every one of them depends on where here is.

| Field | Value |
| --- | --- |
| Proper motion (RA) | −3.27 mas/yr |
| Proper motion (Dec) | −1.83 mas/yr |
| Radial velocity | −43 km/s |

### OTHER NAMES AND NUMBERS

The identifiers other catalogues file this object under, for anyone joining this data to theirs.

| Field | Value |
| --- | --- |
| Variable-star designation | V639 Cas |

### WHERE THESE FIGURES CAME FROM

Which catalogue, paper or model each of the fields above was read from, where the source named one.

| Field | Value |
| --- | --- |
| Spectral type from | SIMBAD (1994BSAO...38..103B, quality C) |
| Stellar parameters from | Spectroscopic determinations compiled from the literature (PASTEL, Soubiran+ 2016) |

## Also known as

- HD: HD 225094
- HIP: HIP 274
- HR: HR 9097
- Variable star: V639 Cas

## Source

[HYG Database v4.1](https://github.com/astronexus/HYG-Database) — CC-BY-SA-4.0

The producer asks: HYG Database v4.1, Astronexus (github.com/astronexus/HYG-Database). Fields derived from it stay under CC BY-SA 4.0.

How this was made: https://spacecatalog.org/methods#source-hyg

## Cite this page

SpaceCatalog. V639 Cas \[catalogue entry\]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/hd-225094

```bibtex
@misc{spacecatalog_hd-225094,
  author       = {{SpaceCatalog}},
  title        = {{V639 Cas}},
  howpublished = {SpaceCatalog, data release DR1 (2026-08-21)},
  year         = {2026},
  url          = {https://spacecatalog.org/object/hd-225094},
  note         = {Catalogue entry, data release DR1 (2026-08-21). Values from HYG Database v4.1.}
}
```

HYG Database v4.1 — CC-BY-SA-4.0

Acknowledgement the producer asks for: HYG Database v4.1, Astronexus (github.com/astronexus/HYG-Database). Fields derived from it stay under CC BY-SA 4.0.

The page itself, with its pictures, the sky map and the observing tools: https://spacecatalog.org/object/hd-225094