V0391 Peg
ILLUSTRATION FROM MEASURED TEMPERATURE · 29 300 K
OVERVIEW
STARV0391 Peg is a sdBV blue-white main-sequence star in the constellation Pegasus, 3901 from Earth, shining at apparent magnitude 14.77 ().
- WHAT IT IS
- Blue-white main-sequence star
- HOW FAR
- 3901
- HOW BRIGHT (V)
The light arriving now left it that long ago.
Faint: it takes a large telescope.
THE MODEL
CATALOGUED RADIUSCALCULATED · NOT AN OBSERVATION · CATALOGUED RADIUS · MEASURED TEMPERATURE · 29 300 K · RADIATIVE ENVELOPE · NO SPOTS, FLARES OR CORONA
Drawn from the catalogued radius and from the same properties the picture at the top of this page uses, at the distance a flight to it would stop. The disc is darker and redder at its edge because a ray leaving at a slant escapes from a shallower, cooler layer of the atmosphere, and the mottling on it is convection. There is nothing else on it: a star this hot carries its energy out through the envelope by radiation rather than convection, and with no convection at the surface there is no dynamo, so no spots, no flares and no corona — which is also why stars above about six and a half thousand kelvin still spin as fast as they were born spinning. Drag it, or use the arrow keys, to look from another direction. The stars behind are the 498,631 this catalogue holds real distances for, drawn from where the camera actually is — but every one of them is within 170 parsecs of the Sun and this object is much further out, so from here that whole neighbourhood is a knot in one direction and the rest of the sky is empty. The view you land on looks the other way; turn back towards the Sun and the stars come with it. What the readout says is which of the two the frame is pointed at. The emptiness is not a missing backdrop — it is the edge of what this catalogue has measured.
OBSERVING
FROM WHERE YOU AREWhat it takes to see V0391 Peg for yourself. Everything in this part of the page is worked out for a real horizon, a real night and the equipment you say you have.
Say where you are, and this line says when V0391 Peg is worth going out for.
THROUGH AN EYEPIECE
150 MM TELESCOPE · 25 MM EYEPIECENear the faint end of this catalogue: a 300 mm telescope reaches it and a 150 mm one does not. It will be a point of light in anything: a star is far enough away that no aperture on Earth gives it a width, and all the equipment changes is how easily you find it.
- 48×
- 1.08
- 1.25
- 13.0
- APPARENT MAGNITUDE ()
- 14.77 · too faint for this
APPARENT PLACE
EQUINOX J2026.8Where a telescope has to be pointed today, which is not quite where the catalogue records the object: the coordinate grid itself has turned since the year 2000 the catalogue is referred to.
- RIGHT ASCENSION
- DECLINATION
- GRID TURNED SINCE
- 18.4
- PROPER MOTION SINCE
- none published
Computed for 2026-11-04 00:00 UT. No proper motion is published for V0391 Peg, so nothing here moves the object; what separates this from the catalogued position above is the coordinate grid turning under it — about fifty arcseconds a year of precession since 2000, and the small nodding of the Earth’s axis on top of that. The catalogue it came from publishes no error for that position, so nothing here says how far this arithmetic can be trusted — the digits above are as precise as the place they were computed from, and no more. Aberration, parallax and refraction are left out. Aberration swings every position by up to twenty arcseconds over a year; parallax stays under an arcsecond for all but the nearest stars; refraction is nothing overhead and about half a degree at the horizon, where it answers to the air, not the sky. The same figure for any date.
SPECTRUM
A SPECTRUM OF ITS TYPENo survey in this catalogue has measured V0391 Peg’s own spectrum: the one that reaches deepest saturates on the brightest stars, and no spectrograph has been pointed at the whole sky. What is drawn below is the average of several real stars of the same class, B5-B7 V. It shows what a star like this one shows, and every line named on it is a line of the type rather than a measurement of V0391 Peg.
A star gives out light at every wavelength at once. The dark gaps are atoms in the thin gas above its surface, each one removing the single colour it is able to absorb — which is how a list of ingredients is read off something nobody will ever touch.
Point at a labelled line — or an element above — to see which atom makes it and where it falls.
Pickles (1998) stellar spectral flux library. B5-B7 V — the average of several real stars of this type, not an observation of any one star. Sampled every 5 angstroms; 1,895 points rebinned onto 1,024 log-spaced display points and normalised to the median flux. Brightness is scaled to this spectrum’s own middle value, so the shape is the measurement and the height is not. The 6 lines named above are the ones that stand clear of the scatter and of the features around them; a spectrum at this sampling holds many more that it cannot separate. The samples themselves, as JSON, CSV or VOTable.
CATALOG DATA
7 FIELDSThe raw catalogue values, as the source published them, with the error bars where one was published — sorted by what each set of figures is about rather than by the order they happened to be stored in.
WHAT KIND OF THING IT IS
What the object is in itself, rather than how it happens to look from here.
- Spectral type
- Surface temperature
- 29 300
- Radius
- 0.23
- Mass
- 0.5
THE ORBIT
The shape of the path, where the object sits on it, and the instant those figures were true of. An orbit is a fit to observations and drifts away from the real one either side of its epoch.
- Stars in system
- 1
- Planets in system
- 1
WHERE THESE FIGURES CAME FROM
Which catalogue, paper or model each of the fields above was read from, where the source named one.
- Stellar parameters from
- NASA Exoplanet Archive composite parameters
LOOK IT UP ELSEWHERE
1 SERVICEEach link carries the identifier printed beside it. Nothing on this page is a measurement of our own, so a number that disagrees with one of these is worth reporting — and a service that has never catalogued this object under this name will say so plainly.
- VizieR5″ around 331.0504 +26.4188
Every published table with a row at this position, searched by coordinates rather than by name.
CITE THIS PAGE
DR1This page is live and its numbers move when an upstream refreshes, so the citation names the release the rows belong to rather than the day you read them. The release itself is frozen, republished as a bundle, and is what a data-availability statement should point at.
SpaceCatalog. V0391 Peg [catalogue entry]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/v0391-peg
@misc{spacecatalog_v0391-peg,
author = {{SpaceCatalog}},
title = {{V0391 Peg}},
howpublished = {SpaceCatalog, data release DR1 (2026-08-21)},
year = {2026},
url = {https://spacecatalog.org/object/v0391-peg},
note = {Catalogue entry, data release DR1 (2026-08-21). Values from NASA Exoplanet Archive (Planetary Systems Composite Parameters).}
}The values above were taken from NASA Exoplanet Archive (Planetary Systems Composite Parameters) — No licence stated; acknowledgement requested. Citing this page does not replace citing that catalogue.
That catalogue asks for this acknowledgement: This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. Cite Christiansen et al. (2025), Planetary Science Journal (doi:10.3847/PSJ/ade3c2), and the literature reference given with each value.