Pulsar
PSR B1939+17 (J1942+1743)
Radio pulsar
A neutron star spinning once every 0.696 seconds; the beams from its magnetic poles sweep across Earth on every turn. Period, spin-down, distance and orbit come from the ATNF Pulsar Catalogue; the beam geometry is illustrative.
| Type | Pulsar |
|---|---|
| Constellation | Sagitta |
| Period | 696.3 ms |
| Period derivative | 1.0×10⁻¹⁶ s/s |
| Characteristic age | 109 million years |
| Magnetic field | 2.7×10¹¹ G |
| Spin-down luminosity | 1.2×10³¹ erg/s |
| Dispersion measure | 190.0 pc/cm³ |
| Distance | 4,915 pc (16.0 thousand ly) |
| Discovery | 1975 · ar1, ar3 |
| Source | ATNF Pulsar Catalogue |
| Right ascension (J2000) | 19h 42m 01.0s |
| Declination (J2000) | +17° 43′ 28″ |
In the sky
Visible from the whole Northern Hemisphere and south to latitude 72° S. North of latitude 72° 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 16 thousand years ago. At that time Homo sapiens was spreading out of Africa; there was no farming yet. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 284 million years.