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Type LRN Supernova

The Story of Supernova AT2023uhx

An extraordinary stellar explosion that occurred 45.2 Million Light-Years away in deep space.

⏱️ ~6 min deep read 🔬 24 Astrophysical Q&As 🔭 Viewing Guide Included 🪐 Constellation Ursa Major
🔭 Deep Field (~2.1′ FOV) · DSS2 Optical (China-VO mirror)
● AT2023uhx Explosion Site

High-magnification deep optical view into AT2023uhx's host environment. Pan and scroll to explore the cosmic neighborhood where this star exploded.

⚡ Quick Observer Facts & Telemetry

IAU Transients DB
🌐 Distance to Earth
45.2 Million Light-Years
Lookback Cosmic Time
✨ Peak Brightness
Mag —
Research Scope
☀️ Peak Radiance
Hundreds of Millions of Suns
Combined Stellar Energy
🚀 Shock Velocity
Not measured
No spectral ejecta velocity
🌌 Host Galaxy
Field Transient Host
Center Coincident
🧭 Constellation
Ursa Major
The Great Bear
💥 Explosion Physics
Type LRN
Core-Collapse Supergiant
📅 Discovered On
2023/10/07
Koichi Itagaki
CHAPTER I

A Core-Collapse Class Transient

On 2023/10/07, astronomers scanning the heavens flagged a sudden, violent pinpoint of light that had flared into visibility. Designated AT2023uhx, it represents a catastrophic stellar explosion classified as a Type LRN supernova.

AT2023uhx is classified in a core-collapse spectroscopic family. Events of this class are generally linked to the death of a massive star after successive nuclear burning stages, but no unique progenitor mass, lifetime, or pre-explosion identification is established for this object. The narrative of onion-shell fusion ending in iron-core collapse describes the class model, not a measured biography of AT2023uhx.

Astrophysical Mechanism Summary
Type: Type LRN • Progenitor: Massive Red/Stripped Supergiant Star • Velocity: Not measured
CHAPTER II

A Message Across Deep Cosmic Time

AT2023uhx has a luminosity distance of approximately 45.2 Million Light-Years (redshift z = 0.003226). That figure is not the light-travel time: under flat ΛCDM the lookback time is ≈45 Myr, when the light set out 45.0 million years ago during the early Cenozoic era, following the extinction of the non-avian dinosaurs.

Luminosity distance incorporates cosmic expansion and exceeds the light-travel distance. The two quantities must be reported separately.

CHAPTER III

Brightness Record

No calibrated peak magnitude is published for AT2023uhx, so neither its apparent brightness nor an equivalent solar luminosity can be stated.

The total energy released by the cataclysm was on the order of 10⁵¹ to 10⁵³ ergs. Over 99% of this energy was emitted within the first 10 seconds as a dense burst of trillions of neutrinos, with only 1% driving the visible blast wave.

CHAPTER IV

The Radioactive Furnace: Why Supernovae Glow for Months

After peak, many supernovae are powered by the radioactive chain ⁵⁶Ni → ⁵⁶Co → ⁵⁶Fe. That is the standard model for Type LRN light curves; an object-specific nickel mass for AT2023uhx is not published here.

Nickel-56 decays to Cobalt-56 (half-life ≈6.1 days), then to stable Iron-56 (half-life ≈77.2 days), heating the ejecta from within. Typical class yields must not be quoted as measured values for this event.

CHAPTER V

Cosmic Kiln: Seeding the Elements of Life

Supernovae enrich galaxies with heavy elements. Events of AT2023uhx's class are associated with oxygen-group and intermediate-mass products (O, C, Ne, Mg, Si) in galactic chemical-evolution models. No measured elemental yields are published for AT2023uhx.

As Carl Sagan observed, "We are made of star-stuff" — a statement about nucleosynthesis in general, not a claim that atoms from this specific remnant are identified in the Solar System.

CHAPTER VI

Galactic Setting in Ursa Major

No host galaxy is identified for AT2023uhx in this catalog record . In our terrestrial sky, it resides in the constellation Ursa Major (The Great Bear) at Right Ascension 11:48:39.508 and Declination +48:41:31.07.

CHAPTER VII

The Scientific Surveillance Campaign

Following its discovery by Koichi Itagaki, observatories worldwide swung their lenses toward AT2023uhx. In the Open Supernova Catalog, AT2023uhx is documented across 0 photometric measurements and 0 spectroscopic epochs. These multi-wavelength observations allow astrophysicists to model the expanding photosphere, measure shock velocities, and probe circumstellar interactions.

CHAPTER VIII

Stargazer's Field Guide: Can You See It Tonight?

Can I see it tonight? Unknown — no measured brightness.

Discovered 3.1 years ago (2023/10/07). No reliable current brightness estimate — no photometry has been published.

Planetary Safety Note: Even though AT2023uhx was a titanic explosion, our planet sits safely outside the lethal 50–100 light-year kill zone. At a distance of 45.2 Million Light-Years, the blast poses zero physical hazard to Earth's biosphere.

🌌 Cosmic Neighbors & Contemporaries 105,768+ transients indexed

Cataloged transients closest to AT2023uhx in discovery time, spatial sky neighborhood, and cosmological redshift:

⏱️ Closest in Time
AT2023uiq Exploded same day
Type Nova 2023/10/07
SN2023uht Exploded same day
Type II 2023/10/07
SN2023uik Exploded same day
Type Ia 2023/10/07
🔭 Closest on the Sky
PS15ao 22.7′ away
Type Transient Discovered 2015/02/12
MLS180504:114823+481212 29.5′ away
Type Candidate Discovered 2018/05/04
SN2024abmk 33.7′ away
Type Ic Discovered 2024/11/14
🌌 Same Cosmic Era (Redshift)
SN2020ocz z = 0.003242
Type II ~44.4 Mly (approx.)
PSN J22060421+4715403 z = 0.003245
Type Transient ~44.5 Mly (approx.)
AT2019ejk z = 0.003206
Type Candidate ~43.9 Mly (approx.)

❓ Frequently Asked Questions About AT2023uhx

Scientific & observational Q&As indexed from astronomical databases & the Open Supernova Catalog
🔍 24 of 24
What type of supernova is AT2023uhx and what kind of star exploded? Astrophysics & Progenitor
AT2023uhx is cataloged as a Type LRN transient. Mechanism-specific claims (progenitor mass, nickel yield, remnant type) require more than this label and are not asserted here as object-specific measurements.
What was the progenitor star doing in the millions of years leading up to AT2023uhx? Astrophysics & Progenitor
The specific progenitor of AT2023uhx has not been observed. Events of this spectroscopic class are generally associated with massive-star core collapse after successive nuclear burning stages (hydrogen → helium → carbon → neon → oxygen → silicon → iron). Typical lifetimes of such progenitors are tens of millions of years, but that is a class expectation—not a measured age or evolutionary track for this star. No pre-explosion imaging identification is cited in the available record for AT2023uhx.
How far away is AT2023uhx from Earth and how old is the light reaching us? Cosmic Distance & Time
AT2023uhx has a luminosity distance of approximately 45.2 Million Light-Years (redshift z = 0.003226, d_L = 13.85). Under a flat ΛCDM cosmology (H₀≈70 km/s/Mpc, Ωₘ≈0.3), the corresponding lookback time is ≈45 Myr — when the light set out 45.0 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 AT2023uhx tell us about the expansion of space? Cosmic Distance & Time
AT2023uhx exhibits a measured spectroscopic redshift of z = 0.0032. The cockpit reports a user-facing recession velocity of 965.6 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 (≈967 km/s) is a different low-z approximation and is not mixed here.
How bright did AT2023uhx become at its peak, and how many Suns does that equal? Explosion Energetics
The peak brightness of AT2023uhx is not recorded. No peak apparent magnitude and no calibrated photometry are published for this transient, so neither its apparent brightness nor its intrinsic luminosity can be stated. Any figure quoted here would be an estimate from a template rather than a measurement of this object. Follow-up photometry would establish the light curve and the peak.
How much total energy was released by AT2023uhx, and where did that energy go? Explosion Energetics
Core-collapse events of this broad class are often discussed with a ~10⁵³ erg gravitational binding energy of which ~99% may escape as neutrinos—again a class scale, not a measured budget for AT2023uhx.
How fast are the supernova ejecta and shockwave of AT2023uhx expanding through space? Explosion Energetics
No ejecta velocity is measured for AT2023uhx. Blast-wave speed is obtained from Doppler shifts of spectral absorption features (e.g. Si II λ6355 for Type Ia), not from cosmological redshift. Any recession velocity derived from z describes Hubble flow, not the explosion debris.
What powers the prolonged glow of AT2023uhx weeks and months after detonation? Radioactive Engine
Classified core-collapse light curves are often sustained after peak by radioactive ⁵⁶Ni → ⁵⁶Co → ⁵⁶Fe decay, with typical nickel yields of order 0.05–0.15 solar masses—again a class scale, not a measured yield for AT2023uhx. Shock-breakout heating may dominate the earliest optical flash; without a published bolometric fit, neither nickel mass nor the dominant power source is established for this event.
What chemical elements did AT2023uhx create and disperse into the universe? Nucleosynthesis & Elements
The nucleosynthetic products of AT2023uhx 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 AT2023uhx leave behind a black hole, a neutron star, or nothing at all? Cosmic Remnant
A core-collapse explosion associated with AT2023uhx's class forges an ultra-dense compact stellar remnant at the center of the detonation. If the progenitor had an initial mass under ~20 solar masses, it left behind a neutron star (pulsar)—packing the mass of our entire Sun into a city-sized sphere barely 20 kilometers wide, spinning dozens or hundreds of times per second. If the progenitor exceeded ~25–30 solar masses, gravity overcame neutron degeneracy pressure, creating a permanent stellar-mass black hole.
What will AT2023uhx'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 AT2023uhx. 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 AT2023uhx explode, and where is it located relative to the galactic center? Galactic Environment
No host galaxy is identified for AT2023uhx in this catalog record. A blank host field means the association is unresolved here—it does not establish that the host is uncataloged, resolved in imaging, or securely linked by astrometry. Possible states (unidentified, hostless candidate, imaging detection without a catalog name, or a securely matched cataloged galaxy) require separate evidence that is not present in this field.
Where is AT2023uhx located in the night sky and which constellation is it in? Sky Coordinates
In the celestial sphere, AT2023uhx is located at Right Ascension 11:48:39.508 and Declination +48:41:31.07, situated in the constellation Ursa Major (The Great Bear). Because its declination is +48:41:31.07, it is primarily placed in the Northern celestial hemisphere.
How much Milky Way interstellar dust obscures our view of AT2023uhx? Interstellar Dust
Along this line of sight, the catalog records a Milky Way foreground color excess of E(B−V) = 0.0369 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 AT2023uhx monitored? Astronomical Observations
No calibrated photometry is published for AT2023uhx. 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 AT2023uhx's chemical makeup? Astronomical Observations
No spectrum has been published for AT2023uhx. 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 AT2023uhx and how was it first detected? Discovery & History
AT2023uhx was officially reported on 2023/10/07 by Koichi Itagaki. 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 AT2023uhx? Scientific Research
Data for AT2023uhx are compiled from international astronomical notices, the IAU Transient Name Server (TNS), and peer-reviewed astrophysical journals.
What other names and survey identifiers exist for AT2023uhx? Cross-Identifications
Throughout global alert streams and survey databases, AT2023uhx has also been designated as: 2023uhx, PS23mva, GOTO23bcx, SN2023uhx, AT 2023uhx, ATLAS23uwy, ZTF23aajlkxc. These cross-matched identifiers allow astronomers to cross-reference observations across the Zwicky Transient Facility (ZTF), the Asteroid Terrestrial-impact Last Alert System (ATLAS), Pan-STARRS, Gaia Photometric Science Alerts, and the IAU Transient Name Server (TNS).
How does AT2023uhx contribute to measuring the Hubble Constant and the scale of the cosmos? Cosmology & Distance Ladder
AT2023uhx 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 AT2023uhx be detected on Earth? Multi-Messenger Astronomy
No neutrino or gravitational-wave counterpart has been reported for AT2023uhx, 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 AT2023uhx 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), AT2023uhx occurred at a distance of 45.2 Million Light-Years. While historical naked-eye supernovae occurred within our Milky Way or its immediate satellites, modern discoveries like AT2023uhx allow astrophysicists to probe diverse galactic environments, metallicities, and stellar populations across the broader universe.
Can I see AT2023uhx tonight with a backyard telescope or binoculars? Backyard Observation
Unknown — no measured brightness. AT2023uhx was discovered 1125 days ago (2023/10/07), 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 AT2023uhx 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 45.2 Million Light-Years, the inverse-square law dilutes the radiation by quintillions of times, making AT2023uhx completely harmless to our biosphere and purely a fascinating spectacle for human exploration.
Data sourced from IAU TNS, ALeRCE, WISeREP, and the Open Supernova Catalog. View All General Astrophysics FAQs →
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