---
title: "RZ Gem"
url: "https://spacecatalog.org/object/hd-250642"
release: "DR1"
licence: "CC-BY-SA-4.0"
citation: "SpaceCatalog. RZ Gem [catalogue entry]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/hd-250642"
---

# RZ Gem

RZ Gem is an F5 yellow-white [star](https://spacecatalog.org/stars) in the constellation [Gemini](https://spacecatalog.org/constellation/gemini), shining at apparent magnitude 9.90 (V). Other catalogues list it as HD 250642 and HIP 28625.

## At a glance

- **WHAT IT IS:** Yellow-white star
- **HOW BRIGHT (V):** 9.90 — A small telescope reaches it.
- **WHERE TO LOOK:** [Gemini](https://spacecatalog.org/constellation/gemini) — The patch of sky it sits in, as seen from Earth.

## Properties

| Quantity | Value |
| --- | --- |
| CLASS | F5 yellow-white star |
| APPARENT MAGNITUDE (V) | 9.90 |
| CONSTELLATION | Gemini |
| RIGHT ASCENSION (J2000) | 06h 02m 36.6s |
| DECLINATION (J2000) | +22° 14′ 02.9″ |

## 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 | F5 |
| Metallicity (\[Fe/H\]) | −0.16 ±0.03 |
| Variability | Classical Cepheid |
| Variability type (GCVS) | DCEP |
| Variability period | 5.529286 days |
| Reference epoch (HJD) | 2442714.9700 |

### 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) | 0.94 |
| Variable magnitude, brightest | 9.36 |
| Variable magnitude, faintest | 10.32 |

### 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) | −0.05 mas/yr |
| Proper motion (Dec) | −4.09 mas/yr |
| Radial velocity | 13.9 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 | RZ Gem |

### 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 (quality D) |
| Metallicity from | One spectroscopic determination, compiled from the literature (PASTEL, Soubiran+ 2016) |

## Also known as

- HD: HD 250642
- HIP: HIP 28625
- Variable star: RZ Gem

## 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. RZ Gem \[catalogue entry\]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/hd-250642

```bibtex
@misc{spacecatalog_hd-250642,
  author       = {{SpaceCatalog}},
  title        = {{RZ Gem}},
  howpublished = {SpaceCatalog, data release DR1 (2026-08-21)},
  year         = {2026},
  url          = {https://spacecatalog.org/object/hd-250642},
  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-250642