T Cae
ILLUSTRATION FROM SPECTRAL TYPE C-N4IV: · 3000 K · LUMINOSITY CLASS · VARIABLE, MAG 7.52–7.80 · PERIOD 158 DAYS · PULSE COMPRESSED
OBSERVING
] FROM WHERE YOU AREWhat it takes to see T Cae 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 T Cae is worth going out for.
THROUGH AN EYEPIECE
] 150 MM TELESCOPE · 25 MM EYEPIECEToo faint for your eyes alone. Binoculars reach it. 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 ()
- 7.66 · within reach
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
- 12.0
- PROPER MOTION SINCE
- 0.18
Computed for 2026-08-28 00:00 UT. Two things separate it from the catalogued position above: T Cae 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.
VARIABILITY
] SEMIREGULAR PULSATING GIANT (POORLY DEFINED PERIODICITY)- RANGE, AS SAMPLED
- 7.52 – 7.80
- PERIOD
- 158 days
For this class the published period is a mean cycle time rather than an ephemeris: the star repeats on that timescale without keeping to it, so counting cycles from a past event would predict a date the star has no obligation to meet.
The range is the spread the Hipparcos satellite measured, converted to the visual scale. It is approximate: the satellite sampled the star on a schedule of its own, and where a star spends little of its cycle at an extreme — the floor of an eclipse, most obviously — the sampling can miss it altogether. The classification and the period are the General Catalogue of Variable Stars’s. These elements as data.
LIFE OF THIS STAR
] STAGE 2 OF 3T Cae is a subgiant: it has used up the hydrogen in its core, it has begun to swell and cool, and it is on its way off the main sequence. In about thirty billion years it will swell into a supergiant, and end by exploding as a supernova and leaving a neutron star.
- COLLAPSING CLOUDtook about five hundred million years
- MAIN SEQUENCEat the end of itNOW
- 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. This star is at the very end of that: its spectrum is classed as a subgiant, which is what a star is called in the short crossing between running out of core hydrogen and swelling into a giant.
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 SEQUENCEat the end of itNOW
- 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 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.
- ALSO A subgiant is the hardest kind of star to place. It is between two stages rather than in one of them, it is the shortest stretch of a star's life, and the mass it started with is what decides how long the crossing takes — so the timing above is the least firm figure in this section.
- ALSO Its class is one only an evolved star can have: the carbon on its surface was made in its own interior and dredged up, which is a thing that happens on the asymptotic giant branch and nowhere earlier.
Which stage T Cae 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, rounded to a single figure. They are orders of magnitude and none of them is a date.
CATALOG DATA
] 12 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
- Variability
- Semiregular pulsating giant (poorly defined periodicity)
- Variability type ()
- SRB
- Variability period
- 158
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)
- Variable magnitude, brightest
- Variable magnitude, faintest
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)
- −0.29
- Proper motion (Dec)
- 6.63
- Radial velocity
- −1
OTHER NAMES AND NUMBERS
The identifiers other catalogues file this object under, for anyone joining this data to theirs.
- Variable-star designation
- T Cae
WHERE THESE FIGURES CAME FROM
Which catalogue, paper or model each of the fields above was read from, where the source named one.
- Spectral type from
- SIMBAD (1993PASP..105..905K, quality B)
ALSO KNOWN AS
] 3 DESIGNATIONS- HD HD 30593
- HIP HIP 22247
- Variable star T Cae
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.
- SIMBADHD 30593
Cross-identifications, measured values and the reference behind each of them.
- ADSobject:"HD 30593"
Papers indexed against this object rather than against the string, newest first.
- VizieR5″ around 71.8289 -36.2093
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. T Cae [catalogue entry]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/hd-30593
@misc{spacecatalog_hd-30593,
author = {{SpaceCatalog}},
title = {{T Cae}},
howpublished = {SpaceCatalog, data release DR1 (2026-08-21)},
year = {2026},
url = {https://spacecatalog.org/object/hd-30593},
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.