🔭 Deep Field (~2.1′ FOV) · Highest-Definition Optical Field (0.25″/pix)
● SN2011fe Explosion Site
High-magnification deep optical view into SN2011fe's host environment. Pan and scroll to explore the cosmic neighborhood where this star exploded.
★ Benchmark Astrophysical Landmark
SN2011fe is recognized as one of the definitive benchmark supernovae in modern astrophysics. Due to its exceptional peak luminosity, favorable host galaxy orientation, and rapid multi-messenger follow-up, it was extensively observed across the electromagnetic spectrum by premier facilities—including space telescopes (HST, JWST, Swift) and global ground-based spectroscopic networks. It provides foundational empirical constraints for stellar progenitor models, ejecta dynamics, and cosmological distance calibrations.
⚡ Quick Observer Facts & Telemetry
IAU Transients DB🌐 Distance to Earth
~21 Million Light-Years
Lookback Cosmic Time
✨ Peak Brightness
Mag 9.48
Binoculars (7x50)
☀️ Peak Radiance
1.8 billion Suns
Combined Stellar Energy
🚀 Shock Velocity
~240 km/s
~0.1% Speed of Light
🌌 Host Galaxy
M101
Offset: 279.20″ (8.01 kpc)
🧭 Constellation
Canes Venatici
The Hunting Dogs
💥 Explosion Physics
Type Ia
Thermonuclear White Dwarf
📅 Discovered On
2011/08/24
Nugent et al.
THE MODERN GOLD STANDARD • PINWHEEL GALAXY (M101)
The Definitive Benchmark Type Ia Supernova of the 21st Century
On August 24, 2011, the automated Palomar Transient Factory (PTF) caught a faint transient in the picturesque spiral arms of the Pinwheel Galaxy (Messier 101) just 11 hours after explosion. Designated SN 2011fe, it surged to peak magnitude 9.9, becoming the brightest, closest, and cleanest Type Ia supernova observed in the northern hemisphere in four decades.
★ Landmark Dossier: SN 2011fe
Host Galaxy: Messier 101 (Pinwheel Galaxy) •
Distance: ~21 Million Light-Years •
Peak Apparent Magnitude: m = +9.9 (Accessible in Binoculars!) •
Milestone: Caught within hours of detonation; Zero host dust reddening (E(B-V) ≈ 0.0)
What made SN 2011fe extraordinary was its pristine observational setting: it detonated in an outer spiral arm of M101 with almost zero interstellar dust extinction. This provided an unblemished, textbook laboratory to observe a carbon-oxygen white dwarf detonation from day zero through late-phase nebular decay.
ASTROPHYSICAL BREAKTHROUGHS
Ruling Out Giant Companion Stars
Because PTF captured the fireball when it was less than one-thousandth of its peak luminosity, astrophysicists were able to set severe physical limits on the size of the progenitor. The absence of an early shock-interaction flash ruled out red giants and normal main-sequence companions, providing powerful evidence favoring the double-degenerate merger channel (the collision of two white dwarfs) or an extremely compact subgiant donor.
Furthermore, deep radio non-detections with the Very Large Array (VLA) proved the circumstellar environment was exceptionally vacuum-clean, confirming that no significant stellar wind was blowing from a companion star in the centuries leading to detonation.
COORDINATES & OBSERVATION
Position in the Pinwheel Galaxy
In the northern night sky, SN 2011fe is located in the magnificent Pinwheel Galaxy in Ursa Major (RA 14:03:05.711,
Dec +54:16:25.22). Its high-fidelity light curves remain the foundational template used by astronomers worldwide to calibrate
cosmological distance scales.
Can I see it tonight? No — this supernova is physically extinguished.
Supernovae are brief, explosive cosmic catastrophes. They brighten over days to weeks and then permanently fade into darkness as their radioactive nickel-56 and cobalt-56 fuel decays. This explosion occurred 15.1 years ago (2011/09/06). Accounting for cosmological time dilation at redshift z = 0.0008, the rest-frame age is +5522.6 days. By standard radioactive decay templates, its optical brightness has decayed by Δm ≈ 84.2 magnitudes to an estimated magnitude 93.7, rendering the transient undetectable to all ground-based observatories.
Instrument Breakdown: At its maximum brightness in 2011/09/06, it reached magnitude 9.48 (Binoculars (50mm)). Tonight, pointing a telescope at these coordinates will reveal only the background host galaxy (M101).
| Instrument Class & Aperture | Sensitivity Limit | At Peak Maximum (m=9.48) | Tonight (Est. m≈93.7) |
|---|---|---|---|
| Naked Eye Dark sky site (Bortle 1–3) with no optical aid |
m ≤ 6.0 | ❌ Below limit | ❌ Below limit |
| Binoculars (50mm) Standard 7x50 or 10x50 handheld binoculars |
m ≤ 9.5 | ✅ Detectable | ❌ Below limit |
| Small Backyard Scope (4" / 100mm) Entry 4-inch (100mm) refractor / reflector |
m ≤ 12.0 | ✅ Detectable | ❌ Below limit |
| Medium Amateur Scope (8"–12") 8-inch to 12-inch Dobsonian or Schmidt-Cassegrain |
m ≤ 14.5 | ✅ Detectable | ❌ Below limit |
| Amateur CMOS Rig Cooled monochrome/color CMOS camera with multi-hour stack |
m ≤ 19.5 | ✅ Detectable | ❌ Below limit |
| 2m–3m Research Telescope University or regional observatory (e.g. Palomar 60", Calar Alto) |
m ≤ 22.0 | ✅ Detectable | ❌ Below limit |
| Giant 8m–10m Observatories Keck (10m), VLT (8.2m), Gemini, Subaru optical imaging |
m ≤ 25.0 | ✅ Detectable | ❌ Below limit |
| Space Observatories Only Hubble Space Telescope (WFC3) / JWST (NIRCam deep stack) |
m ≤ 30.0 | ✅ Detectable | ❌ Below limit |
🌌 Cosmic Neighbors & Contemporaries
110,222+ Transients Indexed
Cataloged supernovae closest to SN2011fe in discovery time, spatial sky neighborhood, and cosmological lookback epoch:
⏱️ Closest in Time
PSc190327
Exploded same day
Type Ia
2011/08/24 · Mag 21.99
PSc310009
Exploded same day
Type Ia
2011/08/24 · Mag 22.33
PSc310050
Exploded same day
Type Ia
2011/08/24 · Mag 22.79
❓ Frequently Asked Questions About SN2011fe
Scientific & observational Q&As indexed from astronomical databases & the Open Supernova Catalog
What type of supernova is SN2011fe and what kind of star exploded? Astrophysics & Progenitor
SN2011fe is classified as a Type Ia Supernova—the complete thermonuclear detonation of an ultra-dense carbon-oxygen white dwarf star. In a binary system, the white dwarf siphoned material from a companion star (or merged with a second white dwarf) until reaching the Chandrasekhar limit (~1.4 solar masses). At this critical threshold, uncontrollable carbon and oxygen fusion detonated through the stellar interior in less than a second with supersonic speeds exceeding 10,000 km/s. Because their peak absolute luminosities follow remarkably consistent empirical relations (the Phillips relation), Type Ia supernovae serve as 'Standard Candles' for measuring cosmological distances and the accelerated expansion of the universe.
What was the progenitor star doing in the millions of years leading up to SN2011fe? Astrophysics & Progenitor
The progenitor of SN2011fe began billions of years ago as a modest intermediate-mass star (1 to 8 solar masses). After exhausting its core hydrogen and helium, it expelled its outer envelope as a glowing planetary nebula, leaving behind a dense carbon-oxygen white dwarf the size of Earth but with the mass of the Sun. For millions or billions of years, it orbited in a close binary system, gradually accreting hydrogen- and helium-rich gas from its stellar companion until gravitational compression pushed its core temperature past the threshold of runaway carbon ignition.
How far away is SN2011fe from Earth and how old is the light reaching us? Cosmic Distance & Time
SN2011fe is located approximately ~21 Million Light-Years from Earth (cosmological redshift z = 0.000804, luminosity distance d_L = 3.56). Because electromagnetic radiation travels at 299,792 km/s, the photons detected by modern telescopes began their cosmic voyage 11.6 million years ago during the Miocene epoch as mammalian lineages and grasslands flourished. While that light traveled across intergalactic space, Earth's continents shifted and biological evolution shaped the history of our planet.
What does the cosmological redshift of SN2011fe tell us about the expansion of space? Cosmic Distance & Time
SN2011fe exhibits a measured spectroscopic redshift of z = 0.0008. Under Hubble's Law, this redshift corresponds to an apparent recessional velocity of approximately 241.0 km/s away from our Milky Way galaxy. This redshift is not motion through space alone, but the stretching of light waves as the fabric of the universe itself expanded during the millions of years the photons traveled to our telescopes.
How bright did SN2011fe become at its peak, and how many Suns does that equal? Explosion Energetics
At peak brightness, SN2011fe achieved an apparent magnitude of 9.48 around 2011/09/06. Corrected for cosmic distance and foreground interstellar dust, its intrinsic absolute magnitude was -18.28. At this peak, the exploding star radiated with the incandescent brilliance of approximately 1.8 billion Suns combined, briefly outshining the cumulative starlight of entire dwarf galaxies!
How much total energy was released by SN2011fe, and where did that energy go? Explosion Energetics
The thermonuclear explosion of SN2011fe released approximately 10⁵¹ ergs of energy (1 Bethe or 1 foe), equivalent to 10²⁸ megatons of TNT! Virtually all of this energy was converted into the kinetic blast wave and the radioactive synthesis of heavy isotopes. Because Type Ia supernovae lack a gravitational core collapse into a neutron star, neutrino emission was minimal (~1%), and the blast converted its full binding energy into the kinetic destruction of the white dwarf.
How fast are the supernova ejecta and shockwave of SN2011fe expanding through space? Explosion Energetics
The debris and shockwave of SN2011fe erupted into space at an astounding velocity of approximately 240 km/s (measured spectroscopically). This corresponds to roughly 0.1% of the speed of light (Mach 700 in air)! At this blistering speed, the expanding debris shell traverses the entire diameter of planet Earth in just 53.09 seconds, carving a giant bubble in the interstellar medium.
What powers the prolonged glow of SN2011fe weeks and months after detonation? Radioactive Engine
The brilliant light curve of SN2011fe is energized by the radioactive decay of heavy isotopes synthesized during detonation. The blast produced approximately 0.5 to 0.7 solar masses of radioactive Nickel-56 (⁵⁶Ni). ⁵⁶Ni decays with a half-life of 6.075 days into Cobalt-56 (⁵⁶Co), emitting energetic gamma rays that heat the opaque expanding fireball to power the optical peak. Subsequently, ⁵⁶Co decays into stable Iron-56 (⁵⁶Fe) with a half-life of 77.2 days, governing the smooth, exponential decline tail observed over the following year.
What chemical elements did SN2011fe create and disperse into the universe? Nucleosynthesis & Elements
As a thermonuclear Type Ia explosion, SN2011fe functioned as a premier cosmic foundry for iron-peak elements. The detonation synthesized over half a solar mass of Iron-56 (⁵⁶Fe)—the exact element that forms Earth's dense metallic core and binds oxygen in human red blood cells! It also forged substantial quantities of silicon (producing the hallmark Si II λ6355 absorption dip), sulfur, calcium, argon, and titanium, enriching the interstellar clouds that condense into future planetary systems.
Did SN2011fe leave behind a black hole, a neutron star, or nothing at all? Cosmic Remnant
Nothing remains at the center. Because a Type Ia supernova involves the total thermonuclear disruption of the progenitor white dwarf, the entire star was incinerated and flung into space. There is no central neutron star, pulsar, or black hole left behind. The star's entire mass now exists as an expanding gaseous shell traveling through the host galaxy.
What will SN2011fe's explosion site look like in 1,000 to 10,000 years? Cosmic Remnant
Over the coming millennia, the explosion site of SN2011fe will undergo three dramatic evolutionary epochs: During the next few centuries (Free Expansion phase), the ejecta shell will continue expanding at thousands of km/s. Between 500 and 10,000 years (the Sedov-Taylor adiabatic phase), the forward shock will sweep up hundreds of solar masses of interstellar gas, heating it to tens of millions of degrees and glowing in bright thermal X-rays (similar to the famous Cygnus Loop or Cassiopeia A). Eventually, the cooling shock will compress nearby giant molecular clouds, triggering the gravitational collapse of new stars and solar systems!
In which galaxy did SN2011fe explode, and where is it located relative to the galactic center? Galactic Environment
SN2011fe occurred in M101, located at an offset of 279.20″ (8.01 kpc) from the galactic nucleus. In optical and infrared imaging, this positions the explosion within the galaxy's active stellar disk or spiral arms, where ongoing star formation constantly generates massive short-lived stellar progenitors.
Where is SN2011fe located in the night sky and which constellation is it in? Sky Coordinates
In the celestial sphere, SN2011fe is located at Right Ascension 14:03:05.711 and Declination +54:16:25.22, situated in the constellation Canes Venatici (The Hunting Dogs). Because its declination is +54:16:25.22, it is primarily placed in the Northern celestial hemisphere.
How much Milky Way interstellar dust obscures our view of SN2011fe? Interstellar Dust
Light from SN2011fe passed through interstellar dust in the Milky Way, suffering a foreground color excess of E(B-V) = 0.008 magnitudes (based on Schlafly & Finkbeiner 2011 galactic recalibrations). This cosmic dust absorbs and scatters shorter blue wavelengths, dimming the transient by approximately A_V ≈ 0.02 magnitudes in visual light.
Across which photometric filter bands was SN2011fe monitored? Astronomical Observations
SN2011fe was tracked across 3483 photometric observations across a baseline of 1474.6 days utilizing filter bands including
1, 2, B, H, I, I1, I2, Ic. Data were captured by observatories and survey networks including ANS 11, ANS 130, ANS 61, BBOS. Multi-color photometry tracks the temperature evolution of the fireball, verifying the rise time to peak and the rate of radioactive decline.What did astronomical spectroscopy reveal about SN2011fe's chemical makeup? Astronomical Observations
Astronomers obtained 158 spectroscopic epochs for SN2011fe from -10.5 Å to 24989.5 Å by facilities including 2.2m uh, HST. Optical spectroscopy provides the definitive physical fingerprint of the transient: P-Cygni line profiles reveal the expansion speed of the ejecta, while characteristic absorption features (such as hydrogen Balmer lines Hα/Hβ in Type II, or Si II λ6355 in Type Ia) identify the stellar composition and physical mechanism of the explosion.
Who discovered SN2011fe and how was it first detected? Discovery & History
SN2011fe was officially reported on 2011/08/24 by Nugent et al.. 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 SN2011fe? Scientific Research
SN2011fe is documented across 45 scientific references and archival data sources in the Open Supernova Catalog. These include discovery circulars and research datasets from 2020MNRAS.492.4325S, 2019MNRAS.490.3882S, 2017MNRAS.466.3442J, 2017MNRAS.472.3437G. 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 SN2011fe? Cross-Identifications
Throughout global alert streams and survey databases, SN2011fe has also been designated as:
PTF11kly, PSN J14030581+5416254, PTF11kly. 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 SN2011fe contribute to measuring the Hubble Constant and the scale of the cosmos? Cosmology & Distance Ladder
Because SN2011fe is a Type Ia supernova, it serves as an indispensable rung on the Cosmic Distance Ladder. Astrophysicists utilize the Phillips relation—a tight empirical correlation between peak absolute magnitude and light curve decline rate (Δm₁₅)—to standardize its luminosity. By comparing this calibrated intrinsic brightness with observed apparent magnitude, researchers calculate precise geometric distances across the universe, providing key empirical tests of the Hubble constant (H₀) and dark energy.
Could gravitational waves or neutrinos from SN2011fe be detected on Earth? Multi-Messenger Astronomy
For thermonuclear explosions like SN2011fe, gravitational wave and neutrino emissions are negligible compared to core-collapse events. However, multi-messenger radio and X-ray observations are crucial: detecting synchrotron radio emission would reveal circumstellar gas shed by a companion star, helping settle the century-old debate between single-degenerate and double-degenerate white dwarf progenitor channels.
How does SN2011fe 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), SN2011fe occurred at a distance of ~21 Million Light-Years. While historical naked-eye supernovae occurred within our Milky Way or its immediate satellites, modern discoveries like SN2011fe allow astrophysicists to probe diverse galactic environments, metallicities, and stellar populations across the broader universe.
Can I see SN2011fe tonight with a backyard telescope or binoculars? Backyard Observation
SN2011fe exploded 15.1 years ago (2011/08/24). Optical transient emission has completely faded along its radioactive decay curve. Today, pointing a telescope at these coordinates reveals the expanding remnant nebula or M101; the original optical transient is no longer detectable with amateur backyard equipment.
Does the radiation or shockwave from SN2011fe 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 ~21 Million Light-Years, the inverse-square law dilutes the radiation by quintillions of times, making SN2011fe 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.
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