299 Thora
Thora (minor planet designation: 299 Thora) is a 17 km Main belt asteroid with a potentially long 274-hour rotation period. It was discovered by Johann Palisa on 6 October 1890 in Vienna. This object has a very low rate of spin, requiring  to complete a full rotation. References

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Background asteroids
Thora
Thora
Slow rotating minor planets
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