SN 2020oi was a

supernova A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion ...

event in the

grand design spiral galaxy A grand design spiral galaxy is a spiral galaxy with prominent and well-defined continuous spiral arms, as opposed to multi-arm, patchy and flocculent spirals which have subtler structural features. The spiral arms of a grand design galaxy exten ...

known as

Messier 100 Messier 100 (also known as NGC 4321 or the Mirror Galaxy) is a grand design spiral galaxy, grand design intermediate spiral galaxy in the southern part of the mildly celestial hemisphere, northern Coma Berenices. It is one of the brightest and l ...

, or NGC 4321. It was discovered January 7, 2020 at an

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

of 17.28 by F. Forster and associates using the

Zwicky Transient Facility The Zwicky Transient Facility (ZTF, List of observatory codes, obs. code: IAU code#I41, I41) is a wide-field sky astronomical survey using a new camera attached to the Samuel Oschin Telescope at Palomar Observatory in San Diego County, Californi ...

. The position places it north of the

galactic nucleus An active galactic nucleus (AGN) is a compact region at the center of a galaxy that emits a significant amount of energy across the electromagnetic spectrum, with characteristics indicating that this luminosity is not produced by the stars. Such e ...

. The supernova was not detected on an observation made three days before the discovery, and thus it must have begun during that brief period. The

light curve In astronomy, a light curve is a graph (discrete mathematics), graph of the Radiance, light intensity of a celestial object or region as a function of time, typically with the magnitude (astronomy), magnitude of light received on the ''y''-axis ...

peaked around January 13–18, depending on the

wavelength In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same ''phase (waves ...

, then declined rapidly over a period of 25 days before flattening into a more gradual decline. Observations of the

spectrum A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...

made with the

SOAR telescope The Southern Astrophysical Research (SOAR) telescope is a modern optical and near-infrared telescope located on Cerro Pachón, Chile at elevation. It was commissioned in 2003, and is operated by a consortium including the countries of Brazil a ...

showed this to be a

type Ic supernova Type Ib and Type Ic supernovae are categories of supernovae that are caused by the stellar core collapse of massive stars. These stars have shed or been stripped of their outer envelope of hydrogen, and, when compared to the spectrum ...

, with the progenitor being a massive star that had its outer envelope stripped. The initial velocity of the expanding

photosphere The photosphere is a star's outer shell from which light is radiated. It extends into a star's surface until the plasma becomes opaque, equivalent to an optical depth of approximately , or equivalently, a depth from which 50% of light will esc ...

was . Models of the event give an initial (

zero age main sequence In astronomy, the main sequence is a classification of stars which appear on plots of stellar color versus brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or dwarf stars, and positions of star ...

) estimated mass of or for the progenitor. It was a member of a

binary star A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...

system and lost its outer envelope of hydrogen and helium due to interaction with its companion. The resulting helium-poor star was primarily made of carbon and oxygen with a mass of about . The supernova explosion was the result of a collapse of an inert iron

core Core or cores may refer to: Science and technology * Core (anatomy), everything except the appendages * Core (laboratory), a highly specialized shared research resource * Core (manufacturing), used in casting and molding * Core (optical fiber ...

. The event ejected of material and left behind a

neutron star A neutron star is the gravitationally collapsed Stellar core, core of a massive supergiant star. It results from the supernova explosion of a stellar evolution#Massive star, massive star—combined with gravitational collapse—that compresses ...

remnant with a presumed mass of . The explosion released about of energy, of which 60% was expended on

kinetic energy In physics, the kinetic energy of an object is the form of energy that it possesses due to its motion. In classical mechanics, the kinetic energy of a non-rotating object of mass ''m'' traveling at a speed ''v'' is \fracmv^2.Resnick, Rober ...

. This is one of the few type Ic supernovae for which

radio Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connec ...

emission has been detected. Based on this data, the

shock wave In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a me ...

from the explosion advanced through the surrounding interstellar matter with a velocity of 3−. In order to produce the observed emission, the progenitor star underwent mass loss at an average rate of ·yr⁻¹ at a typical wind velocity of . Images of the location taken prior to the event using the

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

show a stellar cluster at that location.

References

Further reading