🔭 Deep Field (~2.1′ FOV) · DSS2 Optical (China-VO mirror)
● SN1604A Explosion Site
High-magnification deep optical view into SN1604A's host environment. Pan and scroll to explore the cosmic neighborhood where this star exploded.
★ Benchmark Astrophysical Landmark
SN1604A 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
16,633 Light-Years
Lookback Cosmic Time
✨ Peak Brightness
Mag -2.95
Naked-Eye
☀️ Peak Radiance
340.4 million Suns
Combined Stellar Energy
🚀 Shock Velocity
Not measured
No spectral ejecta velocity
🌌 Host Galaxy
Milky Way
Center Coincident
🧭 Constellation
Scorpius
The Scorpion
💥 Explosion Physics
Type I
Core-Collapse Supergiant
📅 Discovered On
1604/10/09
Altobelli
HISTORIC BENCHMARK • OCTOBER 1604
Kepler's Supernova: The Last Naked-Eye Blast in the Milky Way
In October 1604, German astronomer and mathematician Johannes Kepler observed a brilliant new star in the constellation Ophiuchus, near a planetary conjunction of Mars, Jupiter, and Saturn. SN 1604 peaked at magnitude −2.5 (brighter than Jupiter) and holds a unique place in human history: it is the last supernova observed to detonate within our own Milky Way galaxy.
★ Landmark Dossier: SN 1604 (Kepler's Nova)
Observer: Johannes Kepler (Imperial Mathematician to Rudolf II) •
Type: Type Ia Thermonuclear •
Distance: ~20,000 Light-Years (Ophiuchus) •
Peak Apparent Magnitude: m ≈ −2.5 (Brighter than Jupiter) •
Milestone: Last observed Milky Way supernova in over 420 years!
Kepler documented the star's day-by-day brightness decline for over a year, publishing his monumental work De Stella Nova in Pede Serpentarii ("On the New Star in the Foot of the Serpent Bearer") in 1606. Like Tycho's star three decades earlier, Kepler's supernova proved that the cosmos was dynamic, laying the philosophical foundation for the Scientific Revolution and Newtonian mechanics.
CHANDRA X-RAY MYSTERIES
Dense Circumstellar Knots and the Progenitor Identity
High-resolution imaging with the Chandra X-ray Observatory revealed that Kepler's remnant is rich in dense, nitrogen-enhanced circumstellar knots. This indicates that before the white dwarf detonated, its companion star—likely an evolved asymptotic giant branch (AGB) red giant—shed immense wind material that was compressed by the supersonic blast wave.
Because our galaxy averages an expected 2 to 3 supernovae per century, the Milky Way is currently statistically overdue for its next naked-eye supernova. When the next galactic event detonates, global neutrino networks (SNEWS), gravitational wave detectors, and space observatories stand ready for immediate alert!
COORDINATES & OBSERVABILITY
Observing the Kepler Remnant
Located in the constellation Ophiuchus at RA 17:30:42, Dec -21:29, Kepler's remnant is an intriguing
target for deep narrowband astro-imaging during summer months in both hemispheres.
Can I see it tonight? Only as an expanding historical remnant.
Discovered 154167 days ago (1604/10/09). Cataloged peak 1604/10/28 (154148d ago; rest-frame phase +154148.0d). Cataloged/observed peak: m = -2.95 on 1604/10/28. Latest observed: m = 4.70 on 1605/09/29 (MJD -92455.0).
No reliable current brightness estimate — no event-specific brightness fit with documented uncertainty is published for this object. Class-average decay templates are not used as object-specific predictions. Latest observed magnitude: m = 4.70 on 1605/09/29 (MJD -92455.0). Published upper limits (nondetections) exist in the photometry record. Current brightness trend is unknown (last observation 1605/09/29 (MJD -92455.0); same-band recent pair unavailable or stale).
| Instrument Class & Aperture | Sensitivity Limit | Cataloged Peak (m=-2.95 on 1604/10/28) | Current Brightness Tonight |
|---|---|---|---|
| Naked Eye Dark sky site (Bortle 1–3) with no optical aid | m ≤ 6.0 | ✅ Reachable | No reliable estimate |
| Binoculars (50mm) Standard 7x50 or 10x50 handheld binoculars | m ≤ 9.5 | ✅ Reachable | No reliable estimate |
| Small Backyard Scope (4" / 100mm) Entry 4-inch (100mm) refractor / reflector | m ≤ 12.0 | ✅ Reachable | No reliable estimate |
| Medium Amateur Scope (8"–12") 8-inch to 12-inch Dobsonian or Schmidt-Cassegrain | m ≤ 14.5 | ✅ Reachable | 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 |
🌌 Cosmic Neighbors & Contemporaries
105,868+ transients indexed
Cataloged transients closest to SN1604A in discovery time, spatial sky neighborhood, and cosmological redshift:
⏱️ Closest in Time
SN1572A
11660d before
Type I
1572/11/06 · Mag -4
SN1885A
+102580d after
Type I
1885/08/17 · Mag 9
SN1895A
+106078d after
Type Transient
1895/03/16 · Mag 12.5
🔭 Closest on the Sky
GRB 990426
59.2′ away
Type LGRB
Discovered 1999/04/26
AT2018etu
1.07° away
Type Candidate
Discovered 2018/08/08
Gaia18cev
1.22° away
Type XRB
Discovered 2018/08/14
🌌 Same Cosmic Era (Redshift)
No redshift match available (target z missing or no comparable redshifts in index).
❓ Frequently Asked Questions About SN1604A
Scientific & observational Q&As indexed from astronomical databases & the sne.space
What type of supernova is SN1604A and what kind of star exploded? Astrophysics & Progenitor
SN1604A is cataloged as a Type I 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 SN1604A? Astrophysics & Progenitor
The specific progenitor of SN1604A 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 SN1604A.
How far away is SN1604A from Earth and how old is the light reaching us? Cosmic Distance & Time
SN1604A has a luminosity distance of approximately 16,633 Light-Years. 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 SN1604A tell us about the expansion of space? Cosmic Distance & Time
No spectroscopic redshift has been measured for SN1604A. 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 SN1604A become at its peak, and how many Suns does that equal? Explosion Energetics
At peak brightness, SN1604A achieved an apparent magnitude of -2.95 around 1604/10/28. Corrected for cosmic distance and foreground interstellar dust, its intrinsic absolute magnitude was -16.5. At this peak, the exploding star radiated with the incandescent brilliance of approximately 340.4 million Suns combined, briefly outshining the cumulative starlight of entire dwarf galaxies!
How much total energy was released by SN1604A, 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 SN1604A.
How fast are the supernova ejecta and shockwave of SN1604A expanding through space? Explosion Energetics
No ejecta velocity is measured for SN1604A. 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 SN1604A 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 SN1604A. 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 SN1604A create and disperse into the universe? Nucleosynthesis & Elements
The nucleosynthetic products of SN1604A 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 SN1604A leave behind a black hole, a neutron star, or nothing at all? Cosmic Remnant
A core-collapse explosion associated with SN1604A'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 SN1604A'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 SN1604A. 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 SN1604A explode, and where is it located relative to the galactic center? Galactic Environment
SN1604A is cataloged with host galaxy Milky Way. No secure nuclear offset is published in this record.
Where is SN1604A located in the night sky and which constellation is it in? Sky Coordinates
In the celestial sphere, SN1604A is located at Right Ascension 17:30:42 and Declination -21:29, situated in the constellation Scorpius (The Scorpion). Because its declination is -21:29, it is favorably placed for Southern Hemisphere observatories.
How much Milky Way interstellar dust obscures our view of SN1604A? Interstellar Dust
Along this line of sight, the catalog records a Milky Way foreground color excess of E(B−V) = 0.2205 mag (source: Analytical Galactic Disk Model (IAU)), corresponding to roughly A_V ≈ 0.68 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 SN1604A monitored? Astronomical Observations
SN1604A was tracked across 36 photometric observations across a baseline of 356.0 days utilizing filter bands including
V. Data were captured by observatories and survey networks including global optical observatories. 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 SN1604A's chemical makeup? Astronomical Observations
No spectrum has been published for SN1604A. 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 SN1604A and how was it first detected? Discovery & History
SN1604A was officially reported on 1604/10/09 by Altobelli. 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 SN1604A? Scientific Research
SN1604A is documented across 9 scientific references and archival data sources in the sne.space. These include discovery circulars and research datasets from 2016ApJ...817...36S, 2014BASI...42...47G, 1977hisu.book.....C, Discorso, nel quale si dimostra, che la nuova stella apparita l'Ottobre 1604 non e cometa, ne stella... creata di nuovo... ma una di quelle, che furono da principio nel cielo.. 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 SN1604A? Cross-Identifications
Throughout global alert streams and survey databases, SN1604A has also been designated as:
Kepler's supernova, G004.5+06.8, MWSNR 004.5+06.8, Kepler, SN1604, 3C358, V843 Oph, Kepler's Star. 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 SN1604A contribute to measuring the Hubble Constant and the scale of the cosmos? Cosmology & Distance Ladder
SN1604A 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 SN1604A be detected on Earth? Multi-Messenger Astronomy
No neutrino or gravitational-wave counterpart has been reported for SN1604A, 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 SN1604A 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), SN1604A occurred at a distance of 16,633 Light-Years. While historical naked-eye supernovae occurred within our Milky Way or its immediate satellites, modern discoveries like SN1604A allow astrophysicists to probe diverse galactic environments, metallicities, and stellar populations across the broader universe.
Can I see SN1604A tonight with a backyard telescope or binoculars? Backyard Observation
Unknown — no measured brightness. SN1604A was discovered 154167 days ago (1604/10/09), 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 SN1604A 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 16,633 Light-Years, the inverse-square law dilutes the radiation by quintillions of times, making SN1604A completely harmless to our biosphere and purely a fascinating spectacle for human exploration.
Data sourced from IAU TNS, ALeRCE, WISeREP, and the sne.space.
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