I built a more accurate Galactic GPS for aliens to find us!
In the 1970s, the Pioneer and Voyager spacecraft were launched into deep space - each carrying a message from Earth in the form of plaques and golden records. These included a now-famous diagram: the pulsar map, originally proposed by Carl Sagan, Linda Salzman Sagan, and Frank Drake.
It uses the positions and spin periods of 14 pulsars to show where we are in the galaxy, effectively a cosmic return address.
But there’s a catch: the original map used canonical pulsars, which we now know can glitch and show timing instabilities. Back then, millisecond pulsars hadn’t yet been discovered (they came in the early '80s), so they weren’t included.
As someone studying millisecond pulsars and their long-term timing stability for my PhD, I decided to write some code to rebuild this iconic map - with a little upgrade.
Enter: the Millisecond Pulsar Map.
This version features:
- A top-down view of the Galaxy, with a central measuring bar showing our distance (8 kiloparsecs) from the Galactic Centre.
- Radial lines showing the distance to each millisecond pulsar. These can be measured against the central measuring bar to work out this distance
- Binary encodings for each pulsar's spin period and spin-down rate. These parameters will remain much more stable over the long term.
- A decoding scale to interpret the binary inscriptions.
With 40+ years of high-precision timing data, millisecond pulsars are far more stable than their slower cousins - making them ideal for building a map that could stand the test of cosmic time.
This also highlights how millisecond pulsars could be used as an intergalactic GPS network (because these stable pulsars are like cosmic clocks distributed across the sky). This might be an application for future spacecraft to navigate around the Solar System. Have a read of this article for how we are already building this technology now: https://www.spaceaustralia.com/feature/breaking-free-shackles-terrestrial-time
So, if some distant civilisation stumbles upon this new pulsar map ... well, they’ll know exactly where to find us.
The question is: do we really want to leave our full galactic home address out there?!
