Pulsar
PSR B1957+20 (J1959+2048)
Millisecond pulsar · binary system
A millisecond pulsar spinning 622 times per second: an old neutron star spun up again (“recycled”) by matter transferred from a companion. It shares a 9.17 h orbit with a very-low-mass companion. Period, spin-down, distance and orbit come from the ATNF Pulsar Catalogue; the beam geometry is illustrative.
| Type | Pulsar |
|---|---|
| Constellation | Sagitta |
| Period | 1.607 ms (622 Hz) |
| Period derivative | 1.7×10⁻²⁰ s/s |
| Characteristic age | 1.5 billion years |
| Magnetic field | 1.7×10⁸ G |
| Spin-down luminosity | 1.6×10³⁵ erg/s |
| Dispersion measure | 29.1 pc/cm³ |
| Distance | 1,400 pc (4.6 thousand ly) |
| Companion | very-low-mass companion (estimated), ~0.025 M☉ |
| Orbital period | 9.17 h |
| Discovery | 1988 · ar3, FermiBlind, fast_gpps |
| Source | ATNF Pulsar Catalogue |
| Right ascension (J2000) | 19h 59m 36.8s |
| Declination (J2000) | +20° 48′ 15″ |
In the sky
Visible from the whole Northern Hemisphere and south to latitude 69° S. North of latitude 69° N it never sets. It stands highest at midnight in July, the best time to observe it.
Through a telescope from Earth
Light's journey
The light you see tonight set out 4,566 years ago. At that time the first farming villages were being founded; there was no writing yet. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 81 million years.