Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 2171
| Start | November 28, 2015 at 04:08 AM UTC |
|---|---|
| End | December 25, 2015 at 11:54 AM UTC |
| Length (days) | 27.32 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 2166 | July 14, 2015 at 08:07 PM UTC | August 11, 2015 at 01:19 AM UTC | 27.22 |
| 2167 | August 11, 2015 at 01:19 AM UTC | September 7, 2015 at 07:13 AM UTC | 27.25 |
| 2168 | September 7, 2015 at 07:13 AM UTC | October 4, 2015 at 01:45 PM UTC | 27.27 |
| 2169 | October 4, 2015 at 01:45 PM UTC | October 31, 2015 at 08:45 PM UTC | 27.29 |
| 2170 | October 31, 2015 at 08:45 PM UTC | November 28, 2015 at 04:08 AM UTC | 27.31 |
| 2171 | November 28, 2015 at 04:08 AM UTC | December 25, 2015 at 11:54 AM UTC | 27.32 |
| 2172 | December 25, 2015 at 11:54 AM UTC | January 21, 2016 at 07:59 PM UTC | 27.34 |
| 2173 | January 21, 2016 at 07:59 PM UTC | February 18, 2016 at 04:09 AM UTC | 27.34 |
| 2174 | February 18, 2016 at 04:09 AM UTC | March 16, 2016 at 11:59 AM UTC | 27.33 |
| 2175 | March 16, 2016 at 11:59 AM UTC | April 12, 2016 at 06:58 PM UTC | 27.29 |
| 2176 | April 12, 2016 at 06:58 PM UTC | May 10, 2016 at 12:54 AM UTC | 27.25 |
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.