NGC 6946

Ten supernovae have been observed in NGC 6946 in the 20th and early 21st century: SN 1917A, SN 1939C, SN 1948B, SN 1968D, SN 1969P, SN 1980K, SN 2002hh, SN 2004et, SN 2008S, and SN 2017eaw. For this reason, NGC 6946 has sometimes been referred to as the "Fireworks Galaxy". This is about ten times the rate observed in our Milky Way galaxy, even though the Milky Way has twice as many stars as NGC 6946.

On 27 September 2004, the Type II supernova SN 2004et was observed at magnitude 15.2 and rose to a maximum visual magnitude of 12.7. Images taken during the preceding days revealed that the supernova explosion occurred on 22 September. The progenitor of the supernova was identified on earlier images –– only the seventh time that such an event was directly identified with its host star. The red supergiant progenitor had an initial mass of about 15{{solar mass}} in an interacting binary system shared with a blue supergiant.

During 2009, a bright star within NGC 6946 flared up over several months to become over one million times as bright as the Sun. Shortly thereafter it faded rapidly. Observations with the Hubble Space Telescope suggest that the star did not survive, although there remains some infrared emission from its position. This is thought to come from debris falling onto a black hole that formed when the star died. This potential black hole-forming star is designated N6946-BH1. The progenitor is believed to have been a yellow hypergiant star.{{Cite journal|last=Humphreys|first=Roberta M.|date=31 October 2019|title=Comments on the Progenitor of NGC 6946-BH1|journal=Research Notes of the AAS|volume=3|issue=10|pages=164|doi=10.3847/2515-5172/ab5191|issn=2515-5172|arxiv=1911.02037|bibcode=2019RNAAS...3..164H|s2cid=207880492 |doi-access=free }}

In May 2017, supernova SN 2017eaw was detected in the northwest region of the galaxy, and light curves obtained over the next 600 days showed that it was a Type II-P.{{Cite journal|last1=Buta|first1=Ronald J|last2=Keel|first2=William C|date=21 July 2019|title=BVRI photometry of the classic Type II-P supernova 2017eaw in NGC 6946: d 3 to d 594|url=https://academic.oup.com/mnras/article/487/1/832/5487895|journal=Monthly Notices of the Royal Astronomical Society|language=en|volume=487|issue=1|pages=832–844|doi=10.1093/mnras/stz1291|doi-access=free |issn=0035-8711|arxiv=1905.03084|bibcode=2019MNRAS.487..832B|s2cid=147703978}} The progenitor was determined to have been a red supergiant, with a mass of around 15{{solar mass}}.{{Cite journal|last1=Szalai|first1=Tamás|last2=Vinkó|first2=József|last3=Könyves-Tóth|first3=Réka|last4=Nagy|first4=Andrea P.|last5=Bostroem|first5=K. Azalee|last6=Sárneczky|first6=Krisztián|last7=Brown|first7=Peter J.|last8=Pejcha|first8=Ondrej|last9=Bódi|first9=Attila|last10=Cseh|first10=Borbála|last11=Csörnyei|first11=Géza|date=29 April 2019|title=The Type II-P Supernova 2017eaw: From Explosion to the Nebular Phase|journal=The Astrophysical Journal|volume=876|issue=1|pages=19|doi=10.3847/1538-4357/ab12d0|arxiv=1903.09048|bibcode=2019ApJ...876...19S|s2cid=84842034|issn=1538-4357 |doi-access=free }}

As of 2017, more supernovae had been seen in NGC 6946 than in any other galaxy,{{Cite web|url=https://rochesterastronomy.org/sn2017/sn2017eaw.html|title=Supernova 2017eaw in NGC 6946|quote=This is our most prolific galaxy with now 10 confirmed supernovae discovered.|first=David|last=Bishop|date=14 May 2017|access-date=2023-09-29}} a record that has since been surpassed by NGC 3690.{{Cite web|url=https://rochesterastronomy.org/snimages/sndupe.html|title=The most prolific galaxies|first=David|last=Bishop|date=27 August 2023|access-date=2023-09-29}}

File:NGC 6946 (Kitt Peak National Observatory) (2023-115).png|This image from the Kitt Peak National Observatory contextualizes the locations of supernovae 2004et and 2017eaw within the galaxy.

File:NBO 2017eaw.png|Images of 2017eaw in NGC 6946, taken between May and November 2017, as the supernova was slowly fading

File:Giant star N6946-BH1 before and after it vanished out of sight by imploding to form a black hole.jpg|Pair of visible-light and near-infrared photos from the Hubble Space Telescope showing the giant star N6946-BH1 before and after it vanished out of sight by imploding to form a black hole

File:Dusty supernovae (MIRI, annotated) (dustysupernovae2).jpg|NASA/ESA/CSA James Webb Space Telescope image of NGC 6946, revealing large amounts of dust from the two supernovae SN 2004et and SN 2017eaw

• IC 342 – similar galaxy heavily obscured by Milky Way stars and dust.
• List of galaxies

{{Reflist|refs=

{{cite web

| title=NASA/IPAC Extragalactic Database

| work=Results for NGC 6946

| url=http://ned.ipac.caltech.edu/cgi-bin/objsearch?search_type=Obj_id&objid=48768&objname=1&img_stamp=YES&hconst=73.0&omegam=0.27&omegav=0.73&corr_z=1

| access-date=2022-10-29}}

{{cite book | bibcode=1991rc3..book.....D | year=1991 | title=Third Reference Catalogue of Bright Galaxies | last1=De Vaucouleurs | first1=Gerard | last2=De Vaucouleurs | first2=Antoinette | last3=Corwin | first3=Herold G. | last4=Buta | first4=Ronald J. | last5=Paturel | first5=Georges | last6=Fouque | first6=Pascal }}

{{cite book

|last1=Sandage|first1=A.

|last2=Bedke|first2=J.

|year=1994

|title=The Carnegie Atlas of Galaxies. Volume I

|publisher=Carnegie Institution of Washington

|bibcode=1994cag..book.....S}}

{{cite journal

|last1=Efremov|first1=Yu. N.

|title=Unusual Objects in the Spiral Galaxy NGC 6946

|journal=Open Astronomy

|year=2016

|volume=25

|issue=4

|pages=365–376

|bibcode=2016BaltA..25..369E|doi=10.1515/astro-2017-0255

|doi-access=free

}}

{{cite journal

|last1=Hodge|first1=P.W.

|title=A Possible "Super-Supernova" Remnant in NGC 6946

|journal=Open Astronomy

|year=1967

|volume=79

|issue=466

|pages=466–470

|bibcode=1967PASP...79...29H

|doi=10.1515/astro-2017-0255|doi-access=free

}}

{{cite journal

|last1=Li|first1=W.

|last2=Van Dyk|first2=S.D.

|last3=Filippenko|first3=A.V

|last4=Cuillandre|first4=J.C.

|title=On the Progenitor of the Type II Supernova 2004et in NGC 6946

|journal=Publications of the Astronomical Society of the Pacific

|year=2005

|volume=117|issue=828

|pages=121–131

|bibcode=2005PASP..117..121L

|doi=10.1086/428278|arxiv=astro-ph/0412487|s2cid=17585230

}}

{{Cite web|url=http://www.astronomerstelegram.org/?read=10372|title = ATel #10372: Confirmation of AT 2017eaw, a Probable Supernova in NGC 6946}}

{{Cite web|url=http://www.astronomerstelegram.org/?read=10376|title = ATel #10376: Spectroscopic Classification of SN 2017eaw in NGC 6946 as a Young Type IIP Supernova}}

{{cite web

|title=List of Supernovae

|publisher=Harvard-Smithsonian Center for Astrophysics (IAU)

|url=http://cbat.eps.harvard.edu/lists/Supernovae.html

|access-date=2010-07-12}}

{{Cite news|url=http://www.gemini.edu/node/116

|title=Gemini Observatory Welcomes 2005 with Release of Galactic Fireworks Image

|last=Michaud|first=Peter

|date=1 January 2015

|newspaper=NASA

|access-date=2017-10-15}}

{{Cite news|url=https://www.nasa.gov/mission_pages/chandra/multimedia/fireworks-galaxy-ngc6946.html

|title=NGC 6946: The 'Fireworks Galaxy'

|last=Boen|first=Brooke

|date=20 May 2015

|newspaper=NASA

|access-date=2016-12-08}}

{{citation

|title=Gemini Observatory Welcomes 2005 with Release of Galactic Fireworks Image

|date=1 January 2005

|work=Gemini Observatory

|url=http://www.gemini.edu/node/116

|access-date=2016-01-04}}

{{cite journal

|last1=Adams|first1=S. M.

|last2=Kochanek|first2=C. S.

|last3=Gerke|first3=J. R.

|last4=Stanek|first4=K. Z.

|last5=Dai|first5=X.

|title=The search for failed supernovae with the Large Binocular Telescope: conformation of a disappearing star

|year=2017

|journal=Monthly Notices of the Royal Astronomical Society

|volume=468

|issue=4

|pages=4968–4981

|doi=10.1093/mnras/stx816

|doi-access=free

|arxiv=1609.01283v1|bibcode=2017MNRAS.468.4968A|s2cid=12919545

}}

{{cite web

|title=NGC 6946

|publisher=SEDS

|url=http://www.messier.seds.org/xtra/ngc/n6946.html

|access-date=2017-11-20}}

{{cite journal

| last1 = Kilpatrick

| first1 = Charles

| last2 = Foley

| first2 = Ryan

| title = The Dusty Progenitor Star of the Type II Supernova 2017eaw

| date = 5 September 2018

| journal = Monthly Notices of the Royal Astronomical Society

| volume = 481

| issue = 2

| pages = 2536–2547

| doi = 10.1093/mnras/sty2435| doi-access = free

| arxiv = 1806.00348

}}

}}

{{commons category}}

• [http://messier.seds.org/xtra/ngc/n6946.html SEDS: Spiral Galaxy NGC 6946]
• [http://www.atlasoftheuniverse.com/galax200.html Atlas of the Universe]
• [http://astrobob.areavoices.com/2017/05/26/giant-star-becomes-a-black-hole-right-before-our-eyes N6946-BH1] Giant Star Becomes A Black Hole Right Before Our Eyes!
• {{WikiSky}}
• [https://rochesterastronomy.org/sn2017/sn2017eaw.html List of observations and images of supernova SN 2017eaw]

{{Astronomical catalogs|Arp=29|NGC=6946|C=12|UGC=11597|PGC=65001}}

{{Caldwell catalogue}}

{{NGC objects:6500-6999}}

{{Cygnus (constellation)}}

{{Portal bar|Astronomy|Stars|Outer space}}

{{Sky|20|34|52.3|+|60|09|14|18000000}}

{{DEFAULTSORT:Ngc 6946}}

Category:Cepheus (constellation)

Category:Cygnus (constellation)

Category:Intermediate spiral galaxies

6946

11597

65001

029

012b

17980909

Category:Virgo Supercluster