Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 2185
| Start | December 14, 2016 at 01:16 AM UTC |
|---|---|
| End | January 10, 2017 at 09:14 AM UTC |
| Length (days) | 27.33 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 2180 | July 30, 2016 at 03:40 PM UTC | August 26, 2016 at 09:17 PM UTC | 27.23 |
| 2181 | August 26, 2016 at 09:17 PM UTC | September 23, 2016 at 03:35 AM UTC | 27.26 |
| 2182 | September 23, 2016 at 03:35 AM UTC | October 20, 2016 at 10:25 AM UTC | 27.29 |
| 2183 | October 20, 2016 at 10:25 AM UTC | November 16, 2016 at 05:40 PM UTC | 27.30 |
| 2184 | November 16, 2016 at 05:40 PM UTC | December 14, 2016 at 01:16 AM UTC | 27.32 |
| 2185 | December 14, 2016 at 01:16 AM UTC | January 10, 2017 at 09:14 AM UTC | 27.33 |
| 2186 | January 10, 2017 at 09:14 AM UTC | February 6, 2017 at 05:26 PM UTC | 27.34 |
| 2187 | February 6, 2017 at 05:26 PM UTC | March 6, 2017 at 01:27 AM UTC | 27.33 |
| 2188 | March 6, 2017 at 01:27 AM UTC | April 2, 2017 at 08:49 AM UTC | 27.31 |
| 2189 | April 2, 2017 at 08:49 AM UTC | April 29, 2017 at 03:10 PM UTC | 27.26 |
| 2190 | April 29, 2017 at 03:10 PM UTC | May 26, 2017 at 08:31 PM UTC | 27.22 |
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.