Context :

Aims : The present study reports measurements of the rotation period of a young solar analogue , estimates of its surface coverage by photospheric starspots and of its chromospheric activity level , and derivations of its evolutionary status .
Detailed observations of many young solar-type stars , such as the one reported in the present paper , provide insight into rotation and magnetic properties that may have prevailed on the Sun in its early evolution .

Methods : Using a model based on the rotational modulation of the visibility of active regions , we analysed the high-accuracy CoRoT lightcurve of the active star CoRoT 102899501 .
Spectroscopic follow-up observations were used to derive its fundamental parameters .
We compared the chromospheric activity level of Corot 102899501 with the R _ { HK } ^ { { } ^ { \prime } } index distribution vs age established on a large sample of solar-type dwarfs in open clusters .
We also compared the chromospheric activity level of this young star with a model of chrosmospheric activity evolution established by combining relationships between the R _ { HK } ^ { { } ^ { \prime } } index and the Rossby number with a recent model of stellar rotation evolution on the main sequence .

Results : We measure the spot coverage of the stellar surface as a function of time , and find evidence for a tentative increase from 5-14 % at the beginning of the observing run to 13-29 % 35 days later .
A high level of magnetic activity on Corot 102899501 is corroborated by a strong emission in the Balmer and Ca ii H & K lines ( logR _ { HK } ^ { { } ^ { \prime } } \sim - 4 ) .
The starspots used as tracers of the star rotation constrain the rotation period to 1.625 \pm 0.002 days and do not show evidence for differential rotation . The effective temperature ( T _ { \mathrm { eff } } = 5180 \pm 80 K ) , surface gravity ( log g = 4.35 \pm 0.1 ) , and metallicity ( [ M / H ] = 0.05 \pm 0.07 dex ) indicate that the object is located near the evolutionary track of a 1.09 \pm 0.12 M _ { \odot } pre-main sequence star at an age of 23 \pm 10 Myrs .
This value is consistent with the “ gyro-age ” of about 8-25 Myrs , inferred using a parameterization of the stellar rotation period as a function of colour index and time established for the I -sequence of stars in stellar clusters .

Conclusions : We conclude that the high magnetic activity level and fast rotation of CoRoT 102899501 are manifestations of its stellar youth consistent with its estimated evolutionary status and with the detection of a strong Li i \lambda 6707.8 Å absorption line in its spectrum .
We argue that a magnetic activity level comparable to that observed on CoRot 102899501 could have been present on the Sun at the time of planet formation .