What type of supernova is AT2021ilb and what kind of star exploded?
Astrophysics & Progenitor
AT2021ilb has not been spectroscopically classified. It was reported as an astronomical transient, which means an object was detected changing in brightness, but its nature is not yet established. Classification requires a spectrum: the presence or absence of hydrogen lines separates Type II from Type I, and Type Ia is identified by silicon absorption near 6150 Å combined with the absence of hydrogen. Until such a spectrum is published, claims about the progenitor star or explosion mechanism would be speculation. Check the sources below for follow-up spectroscopy.
What was the progenitor star doing in the millions of years leading up to AT2021ilb?
Astrophysics & Progenitor
The progenitor of AT2021ilb cannot be identified without a classification. Stellar evolutionary history depends entirely on the explosion type: a Type Ia event would require a carbon-oxygen white dwarf in a binary system, whereas a core-collapse event would require a massive star exhausting its fuel within tens of millions of years. These are mutually exclusive histories that produce different spectra and light curves. No progenitor or precursor has been reported for this transient in the available literature.
How far away is AT2021ilb from Earth and how old is the light reaching us?
Cosmic Distance & Time
AT2021ilb has a luminosity distance of approximately 47.5 Million Light-Years (redshift z = 0.00328, d_L = 14.55). Under a flat ΛCDM cosmology (H₀≈70 km/s/Mpc, Ωₘ≈0.3), the corresponding lookback time is ≈46 Myr — when the light set out 45.7 million years ago during the early Cenozoic era, following the extinction of the non-avian dinosaurs. Luminosity distance is larger than the light-travel distance because cosmic expansion stretches the path; the two must not be equated.
What does the cosmological redshift of AT2021ilb tell us about the expansion of space?
Cosmic Distance & Time
AT2021ilb exhibits a measured spectroscopic redshift of z = 0.0033. The cockpit reports a user-facing recession velocity of 981.7 km/s, computed as the redshift Doppler-equivalent v = c·((1+z)²−1)/((1+z)²+1). Cosmological redshift is not generally equivalent to special-relativistic motion through space; this number is a convenient velocity label for z, not a measured peculiar velocity and not supernova ejecta speed. Bare c·z (≈983 km/s) is a different low-z approximation and is not mixed here.
How bright did AT2021ilb become at its peak, and how many Suns does that equal?
Explosion Energetics
At peak brightness, AT2021ilb achieved an apparent magnitude of 16 around 2021/04/05. Corrected for cosmic distance and foreground interstellar dust, its intrinsic absolute magnitude was -14.81. At this peak, the exploding star radiated with the incandescent brilliance of approximately 71.8 million Suns combined, briefly outshining the cumulative starlight of entire dwarf galaxies!
How much total energy was released by AT2021ilb, and where did that energy go?
Explosion Energetics
The total energy released by AT2021ilb is unknown. Energy budgets differ by orders of magnitude depending on mechanism: a thermonuclear Type Ia liberates ~10⁵¹ ergs mostly as kinetic energy, while a core-collapse event liberates ~10⁵³ ergs of which ~99% escapes as neutrinos. Without a spectroscopic classification, neither figure applies to this transient.
How fast are the supernova ejecta and shockwave of AT2021ilb expanding through space?
Explosion Energetics
Spectroscopic line blueshifts imply an ejecta velocity of approximately 982 km/s (~0.3% of c) for AT2021ilb. This is distinct from cosmological recession velocity inferred from redshift.
What powers the prolonged glow of AT2021ilb weeks and months after detonation?
Radioactive Engine
The power source sustaining AT2021ilb cannot be identified without a classification. Classified supernovae are typically powered after peak by the radioactive decay of ⁵⁶Ni → ⁵⁶Co → ⁵⁶Fe, but nickel yields and whether a shock-breakout flash occurred depend on the explosion mechanism. No spectrum is published for this transient, so no ⁵⁶Ni mass or decay-powered light-curve narrative applies.
What chemical elements did AT2021ilb create and disperse into the universe?
Nucleosynthesis & Elements
The nucleosynthetic products of AT2021ilb are unknown because its type is unresolved. Element yields depend directly on the explosion mechanism: a thermonuclear Type Ia produces mostly iron-peak elements such as 56Ni and 56Fe, whereas a core-collapse event produces large quantities of oxygen, neon, magnesium and silicon from successive burning shells. No spectrum has been published for this transient, so which of these occurred is not established.
Did AT2021ilb leave behind a black hole, a neutron star, or nothing at all?
Cosmic Remnant
Whether AT2021ilb left a remnant is unknown. A thermonuclear Type Ia leaves no compact remnant (the white dwarf is fully disrupted), whereas a core-collapse event leaves a neutron star or black hole depending on progenitor mass. Without a spectroscopic classification, none of these outcomes can be asserted for this transient.
What will AT2021ilb's explosion site look like in 1,000 to 10,000 years?
Cosmic Remnant
Supernova remnants in general evolve through free-expansion, Sedov–Taylor, and radiative phases over centuries to millennia, sometimes becoming bright X-ray shells and occasionally compressing nearby molecular clouds. These are standard remnant-evolution models, not forecasts measured for AT2021ilb. Whether this site will trigger star formation, reach particular X-ray temperatures, or match Cassiopeia A depends on local density and magnetic field—none of which are constrained by the data shown here.
In which galaxy did AT2021ilb explode, and where is it located relative to the galactic center?
Galactic Environment
AT2021ilb is cataloged with host galaxy M61. No secure nuclear offset is published in this record.
Where is AT2021ilb located in the night sky and which constellation is it in?
Sky Coordinates
In the celestial sphere, AT2021ilb is located at Right Ascension 12:21:53.124 and Declination +04:28:08.70, situated in the constellation Virgo (The Maiden). Because its declination is +04:28:08.70, it is primarily placed in the Northern celestial hemisphere.
How much Milky Way interstellar dust obscures our view of AT2021ilb?
Interstellar Dust
Along this line of sight, the catalog records a Milky Way foreground color excess of E(B−V) = 0.0366 mag (source: Analytical Galactic Disk Model (IAU)), corresponding to roughly A_V ≈ 0.11 mag for R_V = 3.1. Band-specific corrections (e.g. A_r) differ from A_V and should be applied when available. Map-based values (IRSA / Schlafly & Finkbeiner 2011) must not be claimed unless that map was actually queried.
Across which photometric filter bands was AT2021ilb monitored?
Astronomical Observations
No calibrated photometry is published for AT2021ilb. Without multi-epoch flux measurements, neither a light curve nor a peak magnitude can be established. Follow-up imaging from survey alert streams would be required to map its brightness evolution.
What did astronomical spectroscopy reveal about AT2021ilb's chemical makeup?
Astronomical Observations
No spectrum has been published for AT2021ilb. Without spectroscopy, its chemical composition, expansion velocity, and physical classification cannot be established. Classification spectra from follow-up observatories would be required to identify diagnostic absorption and emission lines.
Who discovered AT2021ilb and how was it first detected?
Discovery & History
AT2021ilb was officially reported on 2021/04/05 by Lorenzo Siciliano. Discoveries are typically flagged by high-cadence robotic survey telescopes (such as ATLAS, ZTF, Pan-STARRS, ASAS-SN, or Gaia) and worldwide amateur astronomers scanning the night sky, followed by rapid spectroscopic classification by international observatories.
How many scientific publications and observatories have contributed data to AT2021ilb?
Scientific Research
Data for AT2021ilb are compiled from international astronomical notices, the IAU Transient Name Server (TNS), and peer-reviewed astrophysical journals.
How does AT2021ilb contribute to measuring the Hubble Constant and the scale of the cosmos?
Cosmology & Distance Ladder
AT2021ilb cannot currently be used for cosmological distance work because its classification is unresolved. The distance ladder relies on type-specific techniques: Type Ia supernovae use the Phillips relation between peak absolute magnitude and decline rate, while Type II events use the Expanding Photosphere Method or SCM-II. An unclassified transient fits neither, so no Hubble-constant constraint can be derived from it until a spectrum establishes its type.
Could gravitational waves or neutrinos from AT2021ilb be detected on Earth?
Multi-Messenger Astronomy
No neutrino or gravitational-wave counterpart has been reported for AT2021ilb, and none is expected to be identifiable without a classification. The multi-messenger signature differs sharply by type: core-collapse events emit a neutrino burst at shock breakout (detected once, for SN 1987A), while thermonuclear Type Ia events produce negligible neutrinos and gravitational waves. Searching for a counterpart before knowing which mechanism applies would be unfocused.
How does AT2021ilb compare to famous historical supernovae like SN 1987A or the Crab Supernova?
Historical Comparison
Compared to historical landmarks like SN 1987A in the Large Magellanic Cloud (168,000 light-years away, naked-eye peak m = 2.9) or the Crab Supernova of 1054 (6,500 light-years away), the distance to AT2021ilb is not established for a historical comparison (unclassified; redshift z = 0.00328 is published but no luminosity distance is derived). While historical naked-eye supernovae occurred within our Milky Way or its immediate satellites, modern discoveries like AT2021ilb allow astrophysicists to probe diverse galactic environments, metallicities, and stellar populations across the broader universe.
Can I see AT2021ilb tonight with a backyard telescope or binoculars?
Backyard Observation
Unknown — no measured brightness. AT2021ilb was discovered 2040 days ago (2021/04/05), but no calibrated photometry is published for it, so its current apparent magnitude cannot be stated. Without a magnitude there is no basis for a telescope-aperture recommendation. Use the coordinates and airmass chart above to plan a follow-up observation and report what you measure.
Does the radiation or shockwave from AT2021ilb pose any threat to Earth?
Planetary Safety
No, Earth is in zero danger. Supernovae are violent events emitting powerful gamma rays, X-rays, and cosmic rays; however, the astrophysical 'lethal kill zone' for our planet's protective ozone layer is estimated at 50 to 100 light-years. At a distance of 47.5 Million Light-Years, the inverse-square law dilutes the radiation by quintillions of times, making AT2021ilb completely harmless to our biosphere and purely a fascinating spectacle for human exploration.
