Cygnus Loop
astronomy
group of bright nebulae (Lacework Nebula, Veil Nebula, and the nebulae NGC 6960, 6979, 6992, and 6995) in the constellation Cygnus, thought to be remnants of a supernova—i.e., of the explosion of a star probably 50,000 years ago. The Loop, a strong source of radio waves and X rays, is still expanding at about 100 kilometres (60 miles) per second. It lies several thousand light-years from the Earth.- John IV
- John IV Lascaris
- John IV Of Odzun
- John IV (or V)
- John, I Walter
- John IX
- John Jackson
- John Jacob Abel
- John Jacob Astor
- John Jacob Astor, 1st Baron Astor
- John Jacob Astor Astor, 1st Baron
- John Jacob Niles
- John Jakob Raskob
- John James Audubon
- John Jay
- John Jay Chapman
- John J(ay) McCloy
- John J. Crittenden
- John Jebb
- John Jenkins
- John Jeremiah Bigsby
- John Jewel
- John J. Flanagan
- John Joly
- John Jones