PSR B0943+10

PSR B0943+10 is a pulsar 2,000 light years from Earth^[2] in the direction of the constellation of Leo.^[4] It was discovered at Pushchino in December 1968, becoming the first pulsar discovered by Soviet astronomers.^[5][6] The original designation of this pulsar was PP 0943.^[1]

PSR B0943+10

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Leo
Right ascension	09h 46m 7.31s[1]
Declination	+09° 51′ 57.3″[1]
Astrometry
Distance	2,000 ly (630 ± 100[2] pc)
Characteristics
Spectral type	Neutron star
Variable type	Pulsar
Details
Mass	1.5[3] M☉
Luminosity	1.31×10−5[2] L☉
Temperature	3.1×106[a][2] K
Rotation	1.1 s[2]
Age	5[b][2] Myr
Database references
SIMBAD	data

Characteristics

The pulsar is estimated to be 5 million years old, which is relatively old for a pulsar.^[7] It has a rotational period of 1.1 seconds and emits both radio waves and X-rays.^[8] Ongoing research at the University of Vermont discovered that the pulsar was found to flip roughly every few hours between a radio bright mode with highly organized pulsations and a quieter mode with rather chaotic temporal structure.^[9][10]

Moreover, the observations of the pulsar performed simultaneously with the European Space Agency's XMM-Newton X-ray observatory and ground-based radio telescopes revealed that it exhibits variations in its X-ray emission that mimic in reverse the changes seen in radio waves – the pulsar has a weaker non-pulsing X-ray luminosity during the radio bright mode and is actually brighter during the radio quiet mode emitting distinct X-ray pulses.^[10] Such changes can only be explained if the pulsar's magnetosphere (which may extend up to 52,000 km from the surface) quickly switches between two extreme states.^[7] The change happens on a few seconds timescale, far faster than most pulsars. Despite being one of the first pulsars discovered, the mechanism for its unusual behavior is unknown.^[9]

In 2006, a research group from Peking University published a paper suggesting that the pulsar may actually be a low-mass quark star with mass around 0.02 M_☉.^[11]

Claimed planetary system

In May 2014, the detection of periodic timing variations was reported^[12] that could be explained by two gas giant planets orbiting PSR B0943+10.^[3][13] A more recent analysis from 2019 found instead a single, five-Earth mass planet with an orbital period of 12 years.^[14][15]

However, all proposed planets were found to be doubtful in a 2025 publication, which suggest the observed variations are due to magnetospheric phenomena and spin-down oscillations. The planets reported in 2014 are classified as "deprecated", while the planet reported in 2019 is a "questionable candidate".^[15]

Notes

1. Blackbody temperature of a small emitting area at the poles
2. Characteristic age