# Why does the Sagan-Drake pulsar map have a circle (negative/blank) near the center?

(click to enlarge, source: WikiMedia)

If you look carefully near the center, each of the pulsar line segments have a gap at a specific radius. I can't find any mention of the meaning of this. Any ideas?

• In case your hot-link breaks: here's an imgur of original i.stack.imgur.com/6HFFB.jpg at en.wikipedia.org/wiki/File:Pioneer10-plaque.jpg
– uhoh
Oct 24 '20 at 13:52
• @Glorfindel I voted to reject your edit. The reason I left the post alone is that I figured the OP left it out intentionally. If they want to include it the link is available in my comment, but in this case I think it's their decision.
– uhoh
Oct 24 '20 at 16:16

It is explained in the original paper from Sagan:

A Message from Earth
Author(s): Carl Sagan, Linda Salzman Sagan and Frank Drake
Source: Science, New Series, Vol. 175, No. 4024 (Feb. 25, 1972), pp. 881-884


I found a copy on the website of Swarthmore College: link to PDF

On page 2, it is explained:

Those radial lines for which the earth-pulsar distance is not accurately known are shown with breaks.

It's clearly not an artefact of the SVG vectorised file on Wikipedia. A photograph of the Voyager Golden record (which features the same map), shows the same gap.

Using this to decode the pulsar map, the distance of the most similar pulsar can be established (280 parsecs)