AT2025mh: What Happened, Distance & Viewing Guide

Q: What type of supernova is AT2025mh and what kind of star exploded?

AT2025mh is cataloged as a Type Varstar transient. Mechanism-specific claims (progenitor mass, nickel yield, remnant type) require more than this label and are not asserted here as object-specific measurements.

Q: What was the progenitor star doing in the millions of years leading up to AT2025mh?

The specific progenitor of AT2025mh 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 AT2025mh.

Q: How far away is AT2025mh from Earth and how old is the light reaching us?

AT2025mh has a luminosity distance of approximately 0 Light-Years (redshift z = 0, d_L = 0.00). A lookback time is not computed here without a usable redshift; do not interpret the luminosity-distance light-year figure as travel time.

Q: What does the cosmological redshift of AT2025mh tell us about the expansion of space?

No spectroscopic redshift has been measured for AT2025mh. Without a published z, its place in the Hubble flow, recession velocity, and lookback time cannot be stated. A redshift requires a spectrum (or a well-calibrated photometric redshift from multi-band imaging). Check the sources below for follow-up spectroscopy.

Q: How bright did AT2025mh become at its peak, and how many Suns does that equal?

Observed (single-epoch) magnitude of AT2025mh is 16.88 (orange) on 2025/01/15 (MJD 60690.3). A single calibrated detection is not evidence of a peak; no rise, decline, or light curve can be established from one point.

Q: How fast are the supernova ejecta and shockwave of AT2025mh expanding through space?

No ejecta velocity is measured for AT2025mh. 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.

          🔭 Deep Field (~2.1′ FOV) · DSS2 Optical (China-VO mirror)
        

● AT2025mh Explosion Site

High-magnification deep optical view into AT2025mh'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

0 Light-Years

Lookback Cosmic Time

✨ Peak Brightness

Mag 16.88 (orange)

Astro Camera (CCD)

☀️ 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

Centaurus

The Centaur

💥 Explosion Physics

Type Varstar

Core-Collapse Supergiant

📅 Discovered On

2025/01/15

J. Tonry, L. Denneau, H. Weiland, R. Siverd (IfA, University of Hawaii), N. Erasmus, W. Koorts (South African Astronomical Observatory), A. Jordan, V. Suc (UAI, Obstech), S. J. Smartt, K. W. Smith (Oxford/QUB), D. R. Young, M. Nicholl, M. Fulton, M. McCollum, T. Moore, J. Weston, X. Sheng, C. R. Angus, A. Wilson, A. Aamer, D. Magill (QUB), P. Ramsden (Birmingham/QUB), L. Shingles (GSI/QUB), S. Srivastav, J. H. Gillanders, H. Stevance, A. J. Cooper, F. Stoppa (Oxford), L. Rhodes (TSI/McGill), A. Rest (STScI), T.-W. Chen (NCU), C. Stubbs (Harvard), J. S. Sommer (LMU), B. P. Schmidt (ANU)

CHAPTER I

A Core-Collapse Class Transient

On 2025/01/15, astronomers scanning the heavens flagged a sudden, violent pinpoint of light that had flared into visibility. Designated AT2025mh, it represents a catastrophic stellar explosion classified as a Type Varstar supernova.

AT2025mh 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 AT2025mh.

Astrophysical Mechanism Summary

Type: Type Varstar • Progenitor: Massive Red/Stripped Supergiant Star • Velocity: Not measured

CHAPTER II

A Message Across Deep Cosmic Time

AT2025mh has a luminosity distance of approximately 0 Light-Years (redshift z = 0). Lookback time is unavailable without a usable redshift; do not equate luminosity distance with travel time.

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

CHAPTER III

Brightness Record

An observed magnitude of 16.88 (orange) is on record around 2025/01/15 (MJD 60690.3). A single detection is not evidence of a peak.

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 Varstar light curves; an object-specific nickel mass for AT2025mh 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 AT2025mh'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 AT2025mh.

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 Centaurus

No host galaxy is identified for AT2025mh in this catalog record . In our terrestrial sky, it resides in the constellation Centaurus (The Centaur) at Right Ascension 13:39:45.576 and Declination -31:42:06.39.

CHAPTER VII

The Scientific Surveillance Campaign

Following its discovery by J. Tonry, L. Denneau, H. Weiland, R. Siverd (IfA, University of Hawaii), N. Erasmus, W. Koorts (South African Astronomical Observatory), A. Jordan, V. Suc (UAI, Obstech), S. J. Smartt, K. W. Smith (Oxford/QUB), D. R. Young, M. Nicholl, M. Fulton, M. McCollum, T. Moore, J. Weston, X. Sheng, C. R. Angus, A. Wilson, A. Aamer, D. Magill (QUB), P. Ramsden (Birmingham/QUB), L. Shingles (GSI/QUB), S. Srivastav, J. H. Gillanders, H. Stevance, A. J. Cooper, F. Stoppa (Oxford), L. Rhodes (TSI/McGill), A. Rest (STScI), T.-W. Chen (NCU), C. Stubbs (Harvard), J. S. Sommer (LMU), B. P. Schmidt (ANU), observatories worldwide swung their lenses toward AT2025mh. In the sne.space, AT2025mh is documented across 1 photometric measurements in passbands such as orange 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 — single-epoch observation only.

Discovered 668 days ago (2025/01/15). Observed magnitude m = 16.88 on 2025/01/15 (MJD 60690.3). A single photometry point is not evidence of a peak, rise, or decline.

Current brightness: No reliable current brightness estimate.

Instrument Class & Aperture	Sensitivity Limit	Observed Single-Epoch Detection (m=16.88 on 2025/01/15 (MJD 60690.3))	Current Brightness Tonight
Naked Eye Dark sky site (Bortle 1–3) with no optical aid	m ≤ 6.0	Requires larger aperture (limit m ≤ 6.0)	No reliable estimate
Binoculars (50mm) Standard 7x50 or 10x50 handheld binoculars	m ≤ 9.5	Requires larger aperture (limit m ≤ 9.5)	No reliable estimate
Small Backyard Scope (4" / 100mm) Entry 4-inch (100mm) refractor / reflector	m ≤ 12.0	Requires larger aperture (limit m ≤ 12.0)	No reliable estimate
Medium Amateur Scope (8"–12") 8-inch to 12-inch Dobsonian or Schmidt-Cassegrain	m ≤ 14.5	Requires larger aperture (limit m ≤ 14.5)	No reliable estimate
Amateur CMOS Rig Cooled monochrome/color CMOS camera with multi-hour stack	m ≤ 19.5	✅ Reachable	No reliable estimate
2m–3m Research Telescope University or regional observatory (e.g. Palomar 60", Calar Alto)	m ≤ 22.0	✅ Reachable	No reliable estimate
Giant 8m–10m Observatories Keck (10m), VLT (8.2m), Gemini, Subaru optical imaging	m ≤ 25.0	✅ Reachable	No reliable estimate
Space Observatories Only Hubble Space Telescope (WFC3) / JWST (NIRCam deep stack)	m ≤ 30.0	✅ Reachable	No reliable estimate

Planetary Safety Note: Even though AT2025mh was a titanic explosion, our planet sits safely outside the lethal 50–100 light-year kill zone. At a distance of 0 Light-Years, the blast poses zero physical hazard to Earth's biosphere.

🌌 Cosmic Neighbors & Contemporaries 105,868+ transients indexed

Cataloged transients closest to AT2025mh in discovery time, spatial sky neighborhood, and cosmological redshift:

⏱️ Closest in Time

AT2025qw Exploded same day

Type AGN 2025/01/15

SN2025ack Exploded same day

Type Ia 2025/01/15

SN2025mb Exploded same day

Type IIb 2025/01/15

🔭 Closest on the Sky

SN1972E 2.5′ away

Type Ia Discovered 1972/05/06

SN1895B 4.2′ away

Type Ia Discovered 1895/07/07

SN2012ag 28.1′ away

Type Ia Discovered 2012/02/16

🌌 Same Cosmic Era (Redshift)

No redshift match available (target z missing or no comparable redshifts in index).

❓ Frequently Asked Questions About AT2025mh

Scientific & observational Q&As indexed from astronomical databases & the sne.space

What type of supernova is AT2025mh and what kind of star exploded? Astrophysics & Progenitor

AT2025mh is cataloged as a Type Varstar 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 AT2025mh? Astrophysics & Progenitor

The specific progenitor of AT2025mh 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 AT2025mh.

How far away is AT2025mh from Earth and how old is the light reaching us? Cosmic Distance & Time

AT2025mh has a luminosity distance of approximately 0 Light-Years (redshift z = 0, d_L = 0.00). A lookback time is not computed here without a usable redshift; do not interpret the luminosity-distance light-year figure as travel time.

What does the cosmological redshift of AT2025mh tell us about the expansion of space? Cosmic Distance & Time

No spectroscopic redshift has been measured for AT2025mh. Without a published z, its place in the Hubble flow, recession velocity, and lookback time cannot be stated. A redshift requires a spectrum (or a well-calibrated photometric redshift from multi-band imaging). Check the sources below for follow-up spectroscopy.

How bright did AT2025mh become at its peak, and how many Suns does that equal? Explosion Energetics

Observed (single-epoch) magnitude of AT2025mh is 16.88 (orange) on 2025/01/15 (MJD 60690.3). A single calibrated detection is not evidence of a peak; no rise, decline, or light curve can be established from one point.

How much total energy was released by AT2025mh, 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 AT2025mh.

How fast are the supernova ejecta and shockwave of AT2025mh expanding through space? Explosion Energetics

No ejecta velocity is measured for AT2025mh. 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 AT2025mh 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 AT2025mh. 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 AT2025mh create and disperse into the universe? Nucleosynthesis & Elements

The nucleosynthetic products of AT2025mh 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 AT2025mh leave behind a black hole, a neutron star, or nothing at all? Cosmic Remnant

A core-collapse explosion associated with AT2025mh'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 AT2025mh'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 AT2025mh. 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 AT2025mh explode, and where is it located relative to the galactic center? Galactic Environment

No host galaxy is identified for AT2025mh 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 AT2025mh located in the night sky and which constellation is it in? Sky Coordinates

In the celestial sphere, AT2025mh is located at Right Ascension 13:39:45.576 and Declination -31:42:06.39, situated in the constellation Centaurus (The Centaur). Because its declination is -31:42:06.39, it is favorably placed for Southern Hemisphere observatories.

How much Milky Way interstellar dust obscures our view of AT2025mh? Interstellar Dust

Along this line of sight, the catalog records a Milky Way foreground color excess of E(B−V) = 0.0647 mag (source: Analytical Galactic Disk Model (IAU)), corresponding to roughly A_V ≈ 0.20 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 AT2025mh monitored? Astronomical Observations

AT2025mh has 1 calibrated photometric detection on record in orange from ATLAS. A single point is not a light curve: no rise, peak, or decline rate can be measured until additional epochs are published.

What did astronomical spectroscopy reveal about AT2025mh's chemical makeup? Astronomical Observations

No spectrum has been published for AT2025mh. 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 AT2025mh and how was it first detected? Discovery & History

AT2025mh was officially reported on 2025/01/15 by J. Tonry, L. Denneau, H. Weiland, R. Siverd (IfA, University of Hawaii), N. Erasmus, W. Koorts (South African Astronomical Observatory), A. Jordan, V. Suc (UAI, Obstech), S. J. Smartt, K. W. Smith (Oxford/QUB), D. R. Young, M. Nicholl, M. Fulton, M. McCollum, T. Moore, J. Weston, X. Sheng, C. R. Angus, A. Wilson, A. Aamer, D. Magill (QUB), P. Ramsden (Birmingham/QUB), L. Shingles (GSI/QUB), S. Srivastav, J. H. Gillanders, H. Stevance, A. J. Cooper, F. Stoppa (Oxford), L. Rhodes (TSI/McGill), A. Rest (STScI), T.-W. Chen (NCU), C. Stubbs (Harvard), J. S. Sommer (LMU), B. P. Schmidt (ANU). 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 AT2025mh? Scientific Research

AT2025mh is documented across 3 scientific references and archival data sources in the sne.space. These include discovery circulars and research datasets from Transient Name Server, 2025TNSTR.191....1T, The Open Supernova Catalog. All raw photometry and spectroscopy points are cross-indexed to their original bibliographic records for peer-reviewed verification.

What other names and survey identifiers exist for AT2025mh? Cross-Identifications

Throughout global alert streams and survey databases, AT2025mh has also been designated as: 2025mh, SN2025mh, AT 2025mh, ATLAS25akn. 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 AT2025mh contribute to measuring the Hubble Constant and the scale of the cosmos? Cosmology & Distance Ladder

AT2025mh 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 AT2025mh be detected on Earth? Multi-Messenger Astronomy

No neutrino or gravitational-wave counterpart has been reported for AT2025mh, 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 AT2025mh 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), AT2025mh occurred at a distance of 0 Light-Years. While historical naked-eye supernovae occurred within our Milky Way or its immediate satellites, modern discoveries like AT2025mh allow astrophysicists to probe diverse galactic environments, metallicities, and stellar populations across the broader universe.

Can I see AT2025mh tonight with a backyard telescope or binoculars? Backyard Observation

Unknown — no measured brightness. AT2025mh was discovered 668 days ago (2025/01/15), 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 AT2025mh 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 0 Light-Years, the inverse-square law dilutes the radiation by quintillions of times, making AT2025mh completely harmless to our biosphere and purely a fascinating spectacle for human exploration.

Data sourced from IAU TNS, ALeRCE, WISeREP, and the sne.space. View All General Astrophysics FAQs →

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The Story of Supernova AT2025mh