UNKNOWN - First issue, March 1939 (pulpmagazines.org)

Here you can download the first issue of UNKNOWN magazine, which contains the science fiction story Sinister Barrier.

excerpt

The size of this magazine exceeds 100 MB. We have chosen to split it into two parts in order to offer the best quality (better vision and direct view) without the user having to download it.

Galactic Center (Wikipedia) The Galactic Center is the rotational center, the barycenter, of the Milky Way galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a compact radio source which is almost exactly at the galactic rotational center. The Galactic Center is approximately 8 kiloparsecs (26,000 ly) away from Earth in the direction of the constellations Sagittarius, Ophiuchus, and Scorpius, where the Milky Way appears brightest, visually close to the Butterfly Cluster (M6) or the star Shaula, south to the Pipe Nebula.

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Sinister Barrier (Wikipedia) Sinister Barrier is an English-language science fiction novel by British writer Eric Frank Russell. The novel originally appeared in the magazine Unknown in 1939, the first novel to appear in its pages. It was first published in book form in 1943 by The World’s Work, Ltd. Russell revised and expanded the book for its first US publication by Fantasy Press in 1948. Most subsequent editions were based on the Fantasy Press version.