Hubble’s view of NGC 6440

The stars of globular cluster NGC 6440 shine brightly in this 2022 NASA/ESA Hubble Space Telescope image.

Globular clusters like NGC 6440 are roughly spherical, tightly packed, collections of old stars bound together by gravity. They can be found throughout galaxies, but often live on the outskirts. They hold hundreds of thousands to millions of stars that are on average about one light-year apart, but they can be as close together as the size of our Solar System.

The data used to create this image came from five different Hubble observing programmes, four of which focused on the properties of pulsars. A pulsar is a highly magnetised, rotating neutron star that emits a beam of electromagnetic radiation from its magnetic poles. To us, that beam appears as a short burst or pulse as the star rotates. Pulsars spin extremely fast. Astronomers have clocked the fastest pulsars at more than 716 rotations per second, but a pulsar could theoretically rotate as fast as 1500 rotations per second before slowly losing energy or breaking apart.