Gl 618B
ILLUSTRATION FROM SPECTRAL TYPE M5 : · 3170 K · 0.000137 L☉
OVERVIEW
] STARGl 618B is an M5 : red star in the constellation Scorpius, 27.63 from Earth, shining at apparent magnitude 14.15 ().
- WHAT IT IS
- : red star
- HOW FAR
- 27.63
- HOW BRIGHT (V)
The light arriving now left it that long ago.
Faint: it takes a large telescope.
THE MODEL
] RADIUS FROM THE LUMINOSITY AND THE TEMPERATURECALCULATED · NOT AN OBSERVATION · RADIUS FROM THE LUMINOSITY AND THE TEMPERATURE · SPECTRAL TYPE M5 : · 3170 K · 0.000137 L☉
Drawn from the radius from the luminosity and the temperature and from the same properties the picture at the top of this page uses, at the distance a flight to it would stop. 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, at their real positions and drawn from where the camera actually is — so the constellations are wrong, and that is the point. This is the sky from there, not the sky from here.
OBSERVING
] FROM WHERE YOU AREWhat it takes to see Gl 618B 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 Gl 618B 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 ()
- 14.15 · too faint for this
APPARENT PLACE
] EQUINOX J2026.7Where 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
- 21.6
- PROPER MOTION SINCE
- 32.5
Computed for 2026-08-27 00:00 UT. Two things separate it from the catalogued position above: Gl 618B has moved under its own proper motion, and the coordinate grid has turned under it — about fifty arcseconds a year of precession since 2000, and the small nodding of the Earth’s axis on top of that. Aberration and refraction are not included, and neither is parallax; each is under an arcminute, which is also about as well as the catalogued position is known. The same figure for any date.
SPECTRUM
] A SPECTRUM OF ITS TYPENo survey in this catalogue has measured Gl 618B’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, M5 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 Gl 618B.
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. M5 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 2 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.
LIFE OF THIS STAR
] STAGE 2 OF 3Gl 618B is a red dwarf on the main sequence, and it will stay there for trillions of years — many times longer than the universe has so far existed — before fading to a white dwarf without ever becoming a giant.
- COLLAPSING CLOUDtook about five hundred million years
- MAIN SEQUENCEabout a trillion years in allNOW
- WHITE DWARFlong after the universe as it is now
NOW Hydrogen fuses to helium in the core, and the outward push of that exactly balances the star's own weight. This is the long, steady stretch — nine-tenths of a star's life — and it ends when the core's hydrogen is gone.
NEXT The bare core, about the size of the Earth, held up by nothing but the resistance of its own crushed electrons. No fusion, no fuel, nothing left to do but cool.
EVERY STAGE ON THIS TRACK
- COLLAPSING CLOUDtook about five hundred million years
- A cold clump of gas and dust falls in on itself and heats as it falls. It stops being a cloud and starts being a star at the moment its core is hot enough to fuse hydrogen.
- MAIN SEQUENCEabout a trillion years in allNOW
- Hydrogen fuses to helium in the core, and the outward push of that exactly balances the star's own weight. This is the long, steady stretch — nine-tenths of a star's life — and it ends when the core's hydrogen is gone.
- WHITE DWARFlong after the universe as it is now
- The bare core, about the size of the Earth, held up by nothing but the resistance of its own crushed electrons. No fusion, no fuel, nothing left to do but cool.
- HOW FIRM No luminosity class is recorded for this star — the catalogue gives its temperature class and stops there — so which stage it is in was read from how far its brightness sits above where a star of its temperature would sit on the main sequence. That is a best estimate rather than a classification.
- ALSO No mass has been measured for this star. The figure above is inferred from its temperature by way of the main-sequence relation between the two, which is tight enough to be worth stating and is still an inference.
Which stage Gl 618B is in was read from its catalogued class, its temperature and its total output at every wavelength — not from its brightness in visible light alone, which understates a cool star by a factor of several. The mass it started with is about a quarter of the Sun's mass, from its temperature, and that mass is what chooses the track. Every span of time here comes from the standard relation between a star’s mass and how long its fuel lasts, and is rounded to a single figure: they are orders of magnitude and none of them is a date.
CATALOG DATA
] 6 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
- Luminosity
- 0.000136773
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.
- Colour index (B−V)
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.
- Proper motion (RA)
- −708.46
- Proper motion (Dec)
- 993.22
- Radial velocity
- 0
ALSO KNOWN AS
] 1 DESIGNATIONS- Gliese Gl 618B
LOOK IT UP ELSEWHERE
] 3 SERVICESEach 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.
- SIMBADGl 618B
Cross-identifications, measured values and the reference behind each of them.
- ADSobject:"Gl 618B"
Papers indexed against this object rather than against the string, newest first.
- VizieR5″ around 245.0180 -37.5307
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. Gl 618B [catalogue entry]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/gliese-gl-618b
@misc{spacecatalog_gliese-gl-618b,
author = {{SpaceCatalog}},
title = {{Gl 618B}},
howpublished = {SpaceCatalog, data release DR1 (2026-08-21)},
year = {2026},
url = {https://spacecatalog.org/object/gliese-gl-618b},
note = {Catalogue entry, data release DR1 (2026-08-21). Values from HYG Database v4.1.}
}The values above were taken from HYG Database v4.1 — CC-BY-SA-4.0. Citing this page does not replace citing that catalogue, and its licence is share-alike: the terms reach whatever you build from these rows.