Editing 1990 in science (section)

==Astronomy and space exploration==
* January 24 – Japan launches the [[Hiten (spacecraft)|Hiten]] spacecraft, the first lunar probe launched by a country other than the Soviet Union or the United States.
* February 14 – The ''[[Pale Blue Dot]]'' photograph of [[Earth]] is sent back from the ''[[Voyager 1]]'' probe after completing its primary mission, from around 3.5 billion miles away.
* April 24 – The [[Space Shuttle Discovery|Space Shuttle ''Discovery'']] places the [[Hubble Space Telescope]] into orbit.<ref>{{cite web|url=http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/archives/sts-31.html|title=STS-31|work=Mission Archives|publisher=[[NASA]]|date=2006-10-14|access-date=2013-01-17}}</ref>
* August 16 – [[Steven Balbus]] makes his first discovery leading to elucidation of [[magnetorotational instability]].<ref>{{cite journal|last1=Balbus|first1=Steven A.|last2=Hawley|first2=John F.|author-link2=John F. Hawley|year=1991|title=A powerful local shear instability in weakly magnetized disks|journal=[[The Astrophysical Journal]]|volume=376|pages=214–233|bibcode=1991ApJ...376..214B|doi=10.1086/170270}}</ref>
* October 13 – [[Earth-grazing meteoroid of 13 October 1990]]: A 44 kilogram, 41.5&nbsp;km/s meteoroid passes above Czechoslovakia and Poland at 97.9&nbsp;km. It is the first time calculations of the orbit of such a body based on photographic records from two distant places is made.<ref>{{cite journal|author1=Spurný, P.|author2=Ceplecha, Z.|author3=Borovicka, J.|title=Earth-grazing fireball: Czechoslovakia, Poland, October 13, 1990, 03h27m16sUT|journal=WGN|year=1991 |volume=19|issue=1|page=13|bibcode=1991JIMO...19...13S}} Aphelion of its orbit changed from 2.80 AU to 1.80 AU.</ref>