---
title: "RT TrA"
url: "https://spacecatalog.org/object/hip-81157"
release: "DR1"
licence: "CC-BY-SA-4.0"
citation: "SpaceCatalog. RT TrA [catalogue entry]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/hip-81157"
---

# RT TrA

RT TrA is a G2Ib-II: yellow supergiant in the constellation [Triangulum Australe](https://spacecatalog.org/constellation/triangulum-australe), 2589 ly from Earth, shining at apparent magnitude 9.70 (V). Other catalogues list it as HIP 81157.

## At a glance

- **WHAT IT IS:** Yellow supergiant
- **HOW FAR:** 2589 ly — The light arriving now left it that long ago.
- **HOW BRIGHT (V):** 9.70 — A small telescope reaches it.
- **WHERE TO LOOK:** [Triangulum Australe](https://spacecatalog.org/constellation/triangulum-australe) — The patch of sky it sits in, as seen from Earth.

## Properties

| Quantity | Value |
| --- | --- |
| CLASS | G2Ib-II: yellow supergiant |
| MASS | 2.88 M☉ — Gaia DR3 model fit (GSP-Phot, FLAME; RUWE ≤ 1.4) |
| DISTANCE FROM EARTH | 2589 ly — by parallax |
| APPARENT MAGNITUDE (V) | 9.70 |
| ABSOLUTE MAGNITUDE (V) | 0.20 |
| CONSTELLATION | Triangulum Australe |
| RIGHT ASCENSION (J2000) | 16h 34m 30.9s |
| DECLINATION (J2000) | −63° 08′ 00.8″ |

## 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 | G2Ib-II: |
| Surface temperature | 5638 K |
| Luminosity | 72.3103 L☉ |
| Luminosity (bolometric) | 89.2459 L☉ |
| Radius | 10.203 R☉ |
| Mass | 2.88 M☉ |
| Surface gravity (log g) | 2.871 |
| Age | 4.14×10⁸ years |
| Variability | W Virginis Cepheid (period under 8 days) |
| Variability type (GCVS) | CWB |
| Variability period | 1.9461124 days |
| Reference epoch (HJD) | 2441922.5400 |

### 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) | 0.76 |
| Variable magnitude, brightest | 9.43 |
| Variable magnitude, faintest | 10.16 |

### 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) | −3.8 mas/yr |
| Proper motion (Dec) | −12.99 mas/yr |
| Radial velocity | 0 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 | RT TrA |

### 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 C) |
| Stellar parameters from | Gaia DR3 model fit (GSP-Phot, FLAME; RUWE ≤ 1.4) |

## Also known as

- HIP: HIP 81157
- Variable star: RT TrA

## 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. RT TrA \[catalogue entry\]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/hip-81157

```bibtex
@misc{spacecatalog_hip-81157,
  author       = {{SpaceCatalog}},
  title        = {{RT TrA}},
  howpublished = {SpaceCatalog, data release DR1 (2026-08-21)},
  year         = {2026},
  url          = {https://spacecatalog.org/object/hip-81157},
  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/hip-81157