AD Cru

CALCULATED · NOT AN OBSERVATION · CATALOGUED RADIUS · MEASURED TEMPERATURE · 5700 K · 1.17 L☉ · VARIABLE, MAG 10.64–11.38 · PERIOD 6.398 DAYS

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. 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 what is in the frame is that whole neighbourhood seen from outside it, piled into a knot around the Sun. The rest of the sky from here is not something this catalogue knows.

Where 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

12h 14m 25.2s

DECLINATION

−62° 14′ 46.0″

GRID TURNED SINCE J2000

13.4′

PROPER MOTION SINCE J2000

0.18″

Computed for 2026-08-27 00:00 UT. Two things separate it from the catalogued position above: AD Cru 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.

RANGE, AS SAMPLED

10.64 – 11.38

PERIOD

6.39789 days

PHASE

0.327 ± 0.0022

NEXT MAXIMUM

2026-08-31 07:23 UT---------- --:-- your time

Computed for 2026-08-27 00:00 UT. A phase of zero is maximum light, and AD Cru was last there 2.09 days before that. The ± is what the published elements can still promise: 2,803 cycles have gone by since the epoch they were measured at, and the last digit of the period compounds over every one of them — 20 min by now. It is the precision of the published figures rather than an error bar the catalogue supplied, so where that catalogue has marked a period doubtful the real spread is wider — and it does not contain the star. A binary with a third body in the system, or a pulsator whose period is slowly changing, walks away from a straight-line ephemeris by an amount only observation settles. Times are corrected for where the Earth is in its orbit, which is worth up to 8.3 minutes — the light of a star reaches us that much earlier in one season than the other, and an epoch measured a century ago has the same correction in it.

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, the period and the epoch are the General Catalogue of Variable Stars’s. The phase at any instant.