4C +37.11

{{Short description|Radio galaxy and elliptical galaxy in the constellation Perseus}}

{{Use dmy dates|date=December 2023}}

{{Infobox Galaxy

| image =

| name = 4C +37.11

| epoch = J2000

| type = Sy{{cite web

| title=NASA/IPAC Extragalactic Database

| work=Results for 0402+379

| url=http://nedwww.ipac.caltech.edu/

| access-date=26 November 2006 }}

| ra = {{RA|04|05|49.2}}

| dec = {{DEC|+38|03|32}}

| dist_ly = 750 Mly (230 Mpc) {{cite web|url=http://www.physorg.com/news65714406.html|title=Scientists Find Closest Pair of Supermassive Black Holes|access-date=15 March 2008|publisher=PhysOrg.com}}

| z = 16,500 ± 300 km/s

| appmag_v = 17.2

| size_v =

| constellation name = Perseus

| notes =

| names = GLXY J0405+380, B2 0402+37, 2MASX J04054928+3803320, RX J0405.8+3803, PGC 2820486

}}

4C +37.11 or Galaxy 0402+379 is a radio galaxy and elliptical galaxy featuring binary supermassive black holes with the least separation of any directly observed binaries, as of 2006. The separation between the two is 24 light-years or 7.3 parsecs, with an orbital period of 30,000 years. The two supermassive black holes, about 750 million light years from earth, have a combined mass of about 15 billion {{Solar mass|link=y}}.{{cite web

| url =http://www.astronomy.com/news/2017/06/orbiting-smbhs

| title =Astronomers spot a pair of orbiting supermassive black holes

| last =Klesman

| first =Alison

| date =29 June 2017

| publisher =Astronomy Magazine

}}

Other supermassive binary black hole candidates suggest the smaller separation distances expected as they eventually merge, but have not been confirmed. For example, quasar OJ 287 is inferred to have a binary supermassive black hole pair with an orbital period of 12 years, and thus be much closer together. However these have not been directly measured and additional observation, possibly over extended time periods, is needed.

The eventual collision of the pair, which should stay apart for at least a few million more years, would result in strong gravitational waves.