SN 1961V was an abnormal, supernova-like event that was a potential

supernova impostor Supernova impostors are stellar explosions that appear at first to be a supernova but do not destroy their progenitor stars. As such, they are a class of extra-powerful novae. They are also known as Type V supernovae, Eta Carinae analogs, and gia ...

. The potential impostor nature of SN 1961V was first identified by

Fritz Zwicky Fritz Zwicky (; ; February 14, 1898 – February 8, 1974) was a Swiss astronomer. He worked most of his life at the California Institute of Technology in the United States of America, where he made many important contributions in theoretical and ...

in 1964. SN 1961V occurred in galaxy

NGC 1058 NGC 1058 is a Seyfert galaxy, Seyfert Type 2 galaxy in the NGC 1023 Group, located in the Perseus (constellation), Perseus constellation. It is approximately 27.4 million light years from Earth and has an apparent magnitude of 11.82. It is rece ...

, about 9.3 Mpc away (about 30 million light years). Unlike many supernovae, the progenitor star is tentatively known: an extremely large, very bright blue star, similar to

Eta Carinae Eta Carinae (η Carinae, abbreviated to η Car), formerly known as Eta Argus, is a stellar system containing at least two stars with a combined luminosity greater than five million times that of the Sun, located around distant in t ...

. Mass estimates of the precursor star were as high as 2000 times the

mass of the sun The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

, but these are likely to be extreme overestimates. If SN 1961V was not a supernova then it was most likely an extremely large outburst by a

luminous blue variable Luminous blue variables (LBVs) are massive evolved stars that show unpredictable and sometimes dramatic variations in their spectra and brightness. They are also known as S Doradus variables after S Doradus, one of the brightest stars of the Larg ...

star. The remnant of SN 1961V's explosion is expanding at 2,000 km/s, which is much slower than the majority of supernovae. The profile of its light curve, with a gradual climb to maximum brightness, was unusual when compared to a supernova. This unusual light curve led to suspicion that it was some other event. If the star survived this would identify SN 1961V as an impostor supernova rather than a true supernova. Attempts to determine if the progenitor star is still present have been extensive and have included use of both the

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...

and the

Spitzer Space Telescope The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), was an infrared space telescope launched in 2003. Operations ended on 30 January 2020. Spitzer was the third space telescope dedicated to infrared astronomy, f ...

. These attempts have been hampered by the cloud of debris from the event, which have left the area obscured.

Christopher Kochanek Christopher Kochanek is an American astronomer. He works in the fields of cosmology, gravitational lensing, and supernovae. Kochanek currently is an Ohio Eminent Scholar at Ohio State University as well as an Elected Fellow of the American Associat ...

Ohio State University The Ohio State University, commonly called Ohio State or OSU, is a public land-grant research university in Columbus, Ohio. A member of the University System of Ohio, it has been ranked by major institutional rankings among the best publ ...

has compared the event to the confirmed supernova

SN 2005gl SN 2005gl was a supernova in the barred-spiral galaxy NGC 266. It was discovered using CCD frames taken October 5, 2005, from the 60 cm automated telescope at the Puckett Observatory in Georgia, US, and reported by Tim Puckett in collabora ...

and suggested that the low velocity of expansion can be explained by a pre-supernova mass loss event similar to that which was observed to occur in SN 2005gl. The analysis by Kochanek's group strongly suggests that SN 1961V was indeed a genuine supernova. Almost at the same moment, another team detected a highly luminous blue star, labeled Object 7, remaining at the site of the supernova, although they couldn't rule out this being a surviving companion of the exploded star.

References

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External links

Spectra
on th
Open Supernova Catalog
19610711 Supernovae Perseus (constellation)