AT2018bmu

AT2018bmu is cataloged as a Type removed transient. Mechanism-specific claims (progenitor mass, nickel yield, remnant type) require more than this label and are not asserted here as object-specific measurements.

The specific progenitor of AT2018bmu 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 AT2018bmu.

The distance to AT2018bmu has not been measured. No spectroscopic redshift or luminosity distance is published for this transient, so neither its distance from Earth nor its lookback time can be stated. A redshift requires a spectrum, and a photometric redshift requires multi-band imaging that has not been reported. Without a distance, its intrinsic luminosity and total energy release are also undetermined. Check the sources below for follow-up spectroscopy or host-galaxy identification.

No spectroscopic redshift has been measured for AT2018bmu. 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.

At peak brightness, AT2018bmu achieved an apparent magnitude of 19.5 around 2018/03/17.

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 AT2018bmu.

No ejecta velocity is measured for AT2018bmu. 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.

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 AT2018bmu. 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.

The nucleosynthetic products of AT2018bmu 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.

A core-collapse explosion associated with AT2018bmu'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.

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 AT2018bmu. 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.

AT2018bmu is associated with cataloged host 2MASX J13442456+5508142 at an angular/physical offset of 2.593 from the reported galactic center. That offset places the transient in the host's projected light distribution; it does not by itself prove which stellar population produced the progenitor.

In the celestial sphere, AT2018bmu is located at Right Ascension 13:44:24.590 and Declination +55:08:11.62, situated in the constellation Canes Venatici (The Hunting Dogs). Because its declination is +55:08:11.62, it is primarily placed in the Northern celestial hemisphere.

Along this line of sight, the catalog records a Milky Way foreground color excess of E(B−V) = 0.0080 mag (source: published extinction estimate), corresponding to roughly A_V ≈ 0.02 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.

No calibrated photometry is published for AT2018bmu. 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.

No spectrum has been published for AT2018bmu. 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.

AT2018bmu was officially reported on 2018/03/17 by ATLAS. 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.

Data for AT2018bmu are compiled from international astronomical notices, the IAU Transient Name Server (TNS), and peer-reviewed astrophysical journals.

Throughout global alert streams and survey databases, AT2018bmu has also been designated as: ATLAS18omv. 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).

AT2018bmu 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.

No neutrino or gravitational-wave counterpart has been reported for AT2018bmu, 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.

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 AT2018bmu is not measured, so no such comparison can be drawn. While historical naked-eye supernovae occurred within our Milky Way or its immediate satellites, modern discoveries like AT2018bmu allow astrophysicists to probe diverse galactic environments, metallicities, and stellar populations across the broader universe.

Unknown — no measured brightness. AT2018bmu was discovered 3155 days ago (2018/03/17), 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.

Earth is in no danger from AT2018bmu. The astrophysical 'lethal kill zone' for a supernova to damage our ozone layer is roughly 50 to 100 light-years. This transient is far outside the solar neighbourhood: it was discovered by a wide-field survey at a magnitude only reachable for an extragalactic object, and any transient in our own galaxy within that radius would have appeared far brighter than the ~18th magnitude reported here. Its exact distance is unmeasured, but the detection brightness alone rules out any nearby threat.