The bag is currently floating about 400km above Earth, but experts say it should be easy to spot because its white surface strongly reflects rays from the Sun.
Astronauts Jasmin Moghbeli and Loral O’Hara were carrying the tool bog during a spacewalk to fix a solar panel on the ISS when it floated away without them noticing.
The slip-up on November 1 was spotted by another astronaut – Japan’s Satoshi Furukawa, – who accidentally photographed it while taking a shot as the ISS passed over his country.
It is now orbiting our planet just ahead of the ISS with a visual magnitude that is marginally less bright than the planet Uranus, according to website EarthSky.
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That means it’s not quite enough to spot with just the eyes, but a telescope or binoclaurs should do the job.
The bag will now gradualy orbit the Earth for several months before eventually entering the planet’s atmosphere and breaking up.
It joins an estimated 100,000 pieces of space junk in our galaxy.
Some of these have been jettisoned accidentally by astronauts during space walks. They include a bolt, spring and washer, a 30cm spatula and a thermal cover.