What was the nationality of Ignaz Semmelweis: Australian, Hungarian, Chinese or American?

What famous catalog of deep-sky objects, compiled by a French astronomer in the 1700s, contains 110 entries?

What type of coral does not rely on photosynthetic algae and must be fed directly?

What is the approximate diameter of the largest known star, UY Scuti, compared to our Sun?

What phenomenon causes stars to appear to twinkle when viewed from Earth's surface?

What type of filtration uses live rock and sand beds to naturally process waste in a marine aquarium?

What is the nitrogen cycle process called that must occur before adding fish to a new saltwater tank?