Astronomical anniversaries in the month of April

Each Month Elizabeth Cocking writes about poignant moments in the incredibly rich history of astronomy and birthdays of astronomers past and present.

26th April 1920

The Great Debate is held at the Smithsonian Museum of Natural History between American astronomers Harlow Shapley and Heber Curtis.

The debate concerned spiral nebulae and the size of the universe. Shapley believed these nebulae were relatively small and lay within the outskirts of the Milky Way galaxy (then thought to be the entire universe), while Curtis maintained they were in fact independent galaxies, implying that they were exceedingly large and distant. The two scientists first presented independent technical papers about "The Scale of the Universe" during the day and then took part in the joint discussion that evening.

In the aftermath of the public debate, scientists have been able to verify individual pieces of evidence from both astronomers, but on the main point of the existence of other galaxies, Curtis has been proven correct. Image above courtesy NASA/JPL/Caltech demonstrates the two views about the actual size of the Milky Way which over 100 years later we have more data on which to base our knowledge. 'ly' = light years

11th April 1970

Apollo 13 is launched from Kennedy Space Centre.

It was the third Apollo mission meant to land on the Moon however two days into the mission a routine stir caused an explosion in both oxygen tanks losing life essential oxygen and dashing any hopes of a lunar landing. The crew instead looped around the Moon and returned safely to Earth on 17th April 1970. The mission was commanded by Jim Lovell, with Jack Swigert as Command Module pilot and Fred Haise as Lunar Module pilot.

“”…Houston we’ve had a problem …”” , first uttered by Jack Swigert to alert Mission Control of the situation, is one of the most famous and oft quoted phrases during times of trouble. Image below shows the crew after splashdown and recovery on April 17, 1970 (l to r) Fred Haise, James Lovell and John Swigert. (Image credit: NASA/JSC).

5th April 1991

The Compton Gamma Ray Observatory is launched on board the Space Shuttle Atlantis from Kennedy Space Centre.

Named in honour of Nobel Prize winner, Dr. Arthur Holly Compton, the Observatory was the second of NASA’s “Great Observatories” following the Hubble Space Telescope and was at the time of launch the heaviest astrophysical payload ever flown on board the Space Shuttle.

The purpose of the Observatory was to use its collection of four primary instruments to detect and study gamma rays, the most energetic form of electromagnetic radiation.

After nine years and four months of operations the Observatory was de-orbited in June 2000 after one of its three gyroscopes failed. Image credit: NASA/MSFC

BORN

4th April 1892

Karl Wilhelm Reinmuth.

German astronomer who was a prolific discoverer of 395 minor planets. He took more than 12,500 precise measurements of minor planets positions on photographic plates, an enormous accomplishment before computer-based assistance existed.

The main-belt asteroid 5535 Annefrank, which he discovered in 1942 was later visited by the Stardust spacecraft in 2002. Reinmuth also discovered two periodic comets 30P/Reinmuth and 44P/Reinmuth.

The outer main-belt asteroid 1111 Reinmuthia, which he discovered in 1912 is named in his honour.