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Type — Supernova

The Story of Supernova RLC11Ale

An extraordinary stellar explosion that occurred 6.94 Billion Light-Years away in deep space.

⏱️ ~6 min deep read 🔬 24 Astrophysical Q&As 🔭 Viewing Guide Included 🪐 Constellation Leo
🔭 Deep Field (~2.1′ FOV) · DSS2 Optical (China-VO mirror)
● RLC11Ale Explosion Site

High-magnification deep optical view into RLC11Ale'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
6.94 Billion Light-Years
Lookback Cosmic Time
✨ Peak Brightness
Mag —
Research Scope
☀️ Peak Radiance
Hundreds of Millions of Suns
Combined Stellar Energy
🚀 Shock Velocity
~93,900 km/s
~31.3% Speed of Light
🌌 Host Galaxy
MACSJ0949.8+1708
Center Coincident
🧭 Constellation
Leo
The Lion
💥 Explosion Physics
Type —
Core-Collapse Supergiant
📅 Discovered On
2011/04/23
HST
CHAPTER I

An Unclassified Astronomical Transient

On 2011/04/23, astronomers scanning the heavens flagged a sudden, violent pinpoint of light that had flared into visibility. Designated RLC11Ale, it is an unclassified astronomical transient whose physical nature is not yet established.

RLC11Ale was reported as a changing source associated with MACSJ0949.8+1708, but it has not been spectroscopically classified. Without a spectrum, the progenitor cannot be identified: a thermonuclear white-dwarf detonation and a core-collapse of a massive star are mutually exclusive histories that produce different spectra and light curves. No progenitor, explosion mechanism, or remnant outcome is established for this object.

Astrophysical Mechanism Summary
Type: Unclassified (no spectrum) • Progenitor: Unknown • Velocity: ~93,900 km/s (~31.3% c)
CHAPTER II

A Message Across Deep Cosmic Time

RLC11Ale has a luminosity distance of approximately 6.94 Billion Light-Years (redshift z = 0.383). That figure is not the light-travel time: under flat ΛCDM the lookback time is ≈4143 Myr, when the light set out 4142.9 million years ago in deep Precambrian time, well before multicellular animals dominated Earth.

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 RLC11Ale, so neither its apparent brightness nor an equivalent solar luminosity can be stated.

The total energy release is unknown without a spectroscopic classification.

CHAPTER IV

The Radioactive Furnace: Why Supernovae Glow for Months

Without a classification, the power source of RLC11Ale cannot be identified; radioactive ⁵⁶Ni decay powers many supernovae but is not established for this transient.

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 RLC11Ale'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 RLC11Ale.

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 Leo

RLC11Ale is associated with cataloged host MACSJ0949.8+1708 . In our terrestrial sky, it resides in the constellation Leo (The Lion) at Right Ascension 09:49:48.07 and Declination +17:07:24.0.

CHAPTER VII

The Scientific Surveillance Campaign

Following its discovery by HST, observatories worldwide swung their lenses toward RLC11Ale. In the sne.space, RLC11Ale 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 15.6 years ago (2011/04/23). No reliable current brightness estimate — no photometry has been published.

Planetary Safety Note: Even though RLC11Ale was a titanic explosion, our planet sits safely outside the lethal 50–100 light-year kill zone. At a distance of 6.94 Billion Light-Years, the blast poses zero physical hazard to Earth's biosphere.

🌌 Cosmic Neighbors & Contemporaries 105,868+ transients indexed

Cataloged transients closest to RLC11Ale in discovery time, spatial sky neighborhood, and cosmological redshift:

⏱️ Closest in Time
PSc150500 Exploded same day
Type Ia 2011/04/23 · Mag 21.83
RLC11Ele Exploded same day
Type Transient 2011/04/23
PSc150740 Exploded same day
Type Ia 2011/04/23 · Mag 21.82
🔭 Closest on the Sky
RLC15Ant 0.0′ away
Type Transient Discovered 2015/10/09
RLC11Ele 0.0′ away
Type Transient Discovered 2011/04/23
AT2020zuv 26.6′ away
Type Candidate Discovered 2020/10/23
🌌 Same Cosmic Era (Redshift)
SDSS-II SN 17191 z = 0.383
Type Ia ~5285.4 Mly (approx.)
SDSS-II SN 9632 z = 0.383
Type Ia ~5285.4 Mly (approx.)
SDSS-II SN 4044 z = 0.383
Type Ia ~5285.4 Mly (approx.)

❓ Frequently Asked Questions About RLC11Ale

Scientific & observational Q&As indexed from astronomical databases & the sne.space
🔍 24 of 24
What type of supernova is RLC11Ale and what kind of star exploded? Astrophysics & Progenitor
RLC11Ale 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 RLC11Ale? Astrophysics & Progenitor
The progenitor of RLC11Ale 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 RLC11Ale from Earth and how old is the light reaching us? Cosmic Distance & Time
RLC11Ale has a luminosity distance of approximately 6.94 Billion Light-Years (redshift z = 0.383, d_L = 2127). Under a flat ΛCDM cosmology (H₀≈70 km/s/Mpc, Ωₘ≈0.3), the corresponding lookback time is ≈4143 Myr — when the light set out 4142.9 million years ago in deep Precambrian time, well before multicellular animals dominated Earth. 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 RLC11Ale tell us about the expansion of space? Cosmic Distance & Time
RLC11Ale exhibits a measured spectroscopic redshift of z = 0.3830. The cockpit reports a user-facing recession velocity of 93,939.8 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 (≈114,821 km/s) is a different low-z approximation and is not mixed here.
How bright did RLC11Ale become at its peak, and how many Suns does that equal? Explosion Energetics
The peak brightness of RLC11Ale 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 RLC11Ale, and where did that energy go? Explosion Energetics
The total energy released by RLC11Ale 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 RLC11Ale expanding through space? Explosion Energetics
Spectroscopic line blueshifts imply an ejecta velocity of approximately 93,900 km/s (~31.3% of c) for RLC11Ale. This is distinct from cosmological recession velocity inferred from redshift.
What powers the prolonged glow of RLC11Ale weeks and months after detonation? Radioactive Engine
The power source sustaining RLC11Ale 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 RLC11Ale create and disperse into the universe? Nucleosynthesis & Elements
The nucleosynthetic products of RLC11Ale 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 RLC11Ale leave behind a black hole, a neutron star, or nothing at all? Cosmic Remnant
Whether RLC11Ale 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 RLC11Ale'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 RLC11Ale. 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 RLC11Ale explode, and where is it located relative to the galactic center? Galactic Environment
RLC11Ale is cataloged with host galaxy MACSJ0949.8+1708. No secure nuclear offset is published in this record.
Where is RLC11Ale located in the night sky and which constellation is it in? Sky Coordinates
In the celestial sphere, RLC11Ale is located at Right Ascension 09:49:48.07 and Declination +17:07:24.0, situated in the constellation Leo (The Lion). Because its declination is +17:07:24.0, it is primarily placed in the Northern celestial hemisphere.
How much Milky Way interstellar dust obscures our view of RLC11Ale? Interstellar Dust
Along this line of sight, the catalog records a Milky Way foreground color excess of E(B−V) = 0.0259 mag (source: published extinction estimate), corresponding to roughly A_V ≈ 0.08 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 RLC11Ale monitored? Astronomical Observations
No calibrated photometry is published for RLC11Ale. 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 RLC11Ale's chemical makeup? Astronomical Observations
No spectrum has been published for RLC11Ale. 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 RLC11Ale and how was it first detected? Discovery & History
RLC11Ale was officially reported on 2011/04/23 by HST. 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 RLC11Ale? Scientific Research
Data for RLC11Ale 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 RLC11Ale? Cross-Identifications
Throughout global alert streams and survey databases, RLC11Ale has also been designated as: SN Alexander. 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 RLC11Ale contribute to measuring the Hubble Constant and the scale of the cosmos? Cosmology & Distance Ladder
RLC11Ale 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 RLC11Ale be detected on Earth? Multi-Messenger Astronomy
No neutrino or gravitational-wave counterpart has been reported for RLC11Ale, 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 RLC11Ale 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 RLC11Ale is not established for a historical comparison (unclassified; redshift z = 0.383 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 RLC11Ale allow astrophysicists to probe diverse galactic environments, metallicities, and stellar populations across the broader universe.
Can I see RLC11Ale tonight with a backyard telescope or binoculars? Backyard Observation
Unknown — no measured brightness. RLC11Ale was discovered 5685 days ago (2011/04/23), 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 RLC11Ale 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 6.94 Billion Light-Years, the inverse-square law dilutes the radiation by quintillions of times, making RLC11Ale 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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