PSR J0437-4715 is a pulsar

Pulsar

A pulsar is a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. The radiation can only be observed when the beam of emission is pointing towards the Earth. This is called the lighthouse effect and gives rise to the pulsed nature that gives pulsars their name...

. Discovered in the Parkes 70 cm survey, it remains the closest and brightest millisecond pulsar

Millisecond pulsar

A millisecond pulsar is a pulsar with a rotational period in the range of about 1-10 milliseconds. Millisecond pulsars have been detected in the radio, X-ray, and gamma ray portions of the electromagnetic spectrum. The origin of millisecond pulsars is still unknown...

 (MSP) known. The pulsar rotates about its axis 173.7 times per second and therefore completes a rotation every 5.75 milliseconds. It emits a searchlight-like radio beam that sweeps past the Earth each time it rotates. Currently the most precisely located object outside of our Solar System, PSR J0437-4715 is 156.3 parsecs or 509.8 light years

Light Years

Light Years is the seventh studio album by Australian recording artist Kylie Minogue. It was released on 25 September 2000 by Parlophone and Mushroom Records. The album's style was indicative of her return to "mainstream pop dance tunes"....

 distant.

This pulsar is distinguished by being the most stable natural clock known and is debatably more stable than man-made atomic clocks. Its stability is about one part in 10¹⁵. Two other pulsars, PSR B1855+09 and PSR B1937+21

PSR B1937+21

PSR B1937+21 is a pulsar located in the constellation Vulpecula a few degrees in the sky away from the first discovered pulsar, PSR B1919+21. The name PSR B1937+21 is derived from the word "pulsar" and the declination and right ascension at which it is located, with the "B" indicating that the...

 are known to be comparable in stability to atomic clocks, or about 3 parts in 10¹⁴.

PSR J0437-4715 is the first MSP to have its X-ray emission detected and studied in detail. It is also the first of only two pulsars to have the full three-dimensional orientation of its orbit determined.

Optical observations indicate that the binary companion of PSR J0437-4715 is most likely a low-mass helium white dwarf

White dwarf

A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...

.
The pulsar is about 1.8 solar mass

Solar mass

The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...

and the companion is about 0.25 solar masses. The pair revolve around each other every 5.75 days in nearly perfect circular orbits.