Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 1144
| Start | March 20, 1939 at 05:46 PM UTC |
|---|---|
| End | April 17, 1939 at 12:36 AM UTC |
| Length (days) | 27.28 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 1139 | November 4, 1938 at 02:31 AM UTC | December 1, 1938 at 09:58 AM UTC | 27.31 |
| 1140 | December 1, 1938 at 09:58 AM UTC | December 28, 1938 at 05:46 PM UTC | 27.33 |
| 1141 | December 28, 1938 at 05:46 PM UTC | January 25, 1939 at 01:54 AM UTC | 27.34 |
| 1142 | January 25, 1939 at 01:54 AM UTC | February 21, 1939 at 10:03 AM UTC | 27.34 |
| 1143 | February 21, 1939 at 10:03 AM UTC | March 20, 1939 at 05:46 PM UTC | 27.32 |
| 1144 | March 20, 1939 at 05:46 PM UTC | April 17, 1939 at 12:36 AM UTC | 27.28 |
| 1145 | April 17, 1939 at 12:36 AM UTC | May 14, 1939 at 06:23 AM UTC | 27.24 |
| 1146 | May 14, 1939 at 06:23 AM UTC | June 10, 1939 at 11:21 AM UTC | 27.21 |
| 1147 | June 10, 1939 at 11:21 AM UTC | July 7, 1939 at 04:05 PM UTC | 27.20 |
| 1148 | July 7, 1939 at 04:05 PM UTC | August 3, 1939 at 09:08 PM UTC | 27.21 |
| 1149 | August 3, 1939 at 09:08 PM UTC | August 31, 1939 at 02:52 AM UTC | 27.24 |
About this tool
A Carrington rotation is the time the Sun takes to turn once on its axis as seen from the Earth: 27.2753 days on average. The count was defined by the English astronomer Richard Carrington, who studied sunspots in the 1850s; rotation 1 began on 9 November 1853, and the numbering has run without interruption since.
Explorer computes the start of each rotation with the formula given by Jean Meeus in Astronomical Algorithms (chapter 29), implemented in its own astronomy library and checked against published dates. A rotation begins when the Carrington longitude L₀ of the central meridian passes through 0°; because the Earth moves along its orbit, the synodic period varies slightly around the mean, hence lengths of 27.2 to 27.3 days.
Observers use the rotation number as a calendar for the Sun: an active region that crosses the disc reappears about one rotation later, and the community activity heatmap shows one row per rotation so that returning regions line up. Enter a date to find its rotation, or a number to get the UTC start and end dates and the neighbouring rotations.