High-magnification deep optical view into ASASSN-18dn's host environment. Pan and scroll to explore the cosmic neighborhood where this star exploded.
⚡ Quick Observer Facts & Telemetry
IAU Transients DBThe Thermonuclear Obliteration of a White Dwarf
On 2018/02/22, astronomers scanning the heavens flagged a sudden, violent pinpoint of light that had flared into visibility. Designated ASASSN-18dn, it represents a catastrophic stellar explosion classified as a Type Ia supernova.
In a binary star system located deep within 2MASX J10023148+1343409, a dense carbon-oxygen white dwarf—the dead stellar corpse of an ancient sun—orbited its stellar companion for millions of years. As it siphoned material across the gravitational saddle point, its mass relentlessly climbed toward the Chandrasekhar limit of 1.4 solar masses. At that fateful tipping point, uncontrollable carbon fusion ignited in the degenerate core, ripping the entire star apart in a thermonuclear detonation that left behind zero remnant.
A Message Across Deep Cosmic Time
The light from ASASSN-18dn is a dispatch from an ancient past. Located approximately 571.6 Million Light-Years away
(redshift z = 0.03848), the photons detected by telescopes today began their journey
571.6 million years ago during the Paleozoic era, long before the first dinosaurs appeared on Earth.
While this burst of electromagnetic radiation traversed the cold void of intergalactic space at 299,792 kilometers per second, continents on Earth drifted, mountain ranges rose, and entire ecosystems rose and fell. To look into a telescope at ASASSN-18dn is to gaze directly into prehistoric cosmic time.
Incandescence of 1.7 billion Suns
At the height of the outburst around 2018/02/21, ASASSN-18dn surged to a peak apparent magnitude of 17.9 and an intrinsic absolute magnitude of -18.277. At that instant, this single dying star radiated with the collective power of approximately 1.7 billion Suns combined, outshining whole dwarf galaxies and illuminating the surrounding interstellar medium.
The total energy released by the cataclysm was on the order of 10⁵¹ to 10⁵³ ergs. Virtually all of this was deposited into the kinetic shockwave and radioactive nucleosynthesis.
The Radioactive Furnace: Why Supernovae Glow for Months
Unlike a conventional terrestrial explosion that cools and goes dark in seconds, ASASSN-18dn shone brightly for weeks and months. The secret behind this prolonged celestial glow is nuclear physics: the extreme heat and pressure of detonation synthesized vast quantities of radioactive Nickel-56 (⁵⁶Ni).
With a half-life of 6.075 days, Nickel-56 decays into Cobalt-56 (⁵⁶Co), emitting gamma rays and high-energy positrons that heat the expanding ejecta from within. Cobalt-56 in turn decays with a half-life of 77.2 days into stable Iron-56 (⁵⁶Fe), powering the steady exponential radioactive tail observed in the light curve.
Cosmic Kiln: Seeding the Elements of Life
Supernovae are the premier chemical foundries of our universe. ASASSN-18dn forged and liberated tons of newly synthesized elements: rich supplies of iron, silicon, calcium, and sulfur that will one day seed the formation of rocky terrestrial worlds.
As Carl Sagan famously observed, "We are made of star-stuff." The iron atoms that carry oxygen in human hemoglobin and the calcium in our bones were originally forged in explosions identical to ASASSN-18dn billions of years ago.
Galactic Setting in Columba
ASASSN-18dn detonated inside 2MASX J10023148+1343409, positioned at an offset of 1.07″ (0.84 kpc) from the galactic nucleus.
In our terrestrial sky, it resides in the constellation Columba (The Dove) at Right Ascension 06:10:58.951
and Declination -33:41:18.09.
The Scientific Surveillance Campaign
Following its discovery by ASAS-SN, observatories worldwide swung their lenses toward ASASSN-18dn. In the Open Supernova Catalog, ASASSN-18dn 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.
Stargazer's Field Guide: Can You See It Tonight?
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 8.6 years ago (2018/02/21). Accounting for cosmological time dilation at redshift z = 0.0385, the rest-frame age is +3027.5 days. By standard radioactive decay templates, its optical brightness has decayed by Δm ≈ 46.8 magnitudes to an estimated magnitude 64.7, rendering the transient undetectable to all ground-based observatories.
Instrument Breakdown: At its maximum brightness in 2018/02/21, it reached magnitude 17.90 (Amateur CMOS Rig). Tonight, pointing a telescope at these coordinates will reveal only the background host galaxy (2MASX J10023148+1343409).
| Instrument Class & Aperture | Sensitivity Limit | At Peak Maximum (m=17.90) | Tonight (Est. m≈64.7) |
|---|---|---|---|
| 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 | ❌ Below limit | ❌ Below limit |
| Small Backyard Scope (4" / 100mm) Entry 4-inch (100mm) refractor / reflector |
m ≤ 12.0 | ❌ Below limit | ❌ Below limit |
| Medium Amateur Scope (8"–12") 8-inch to 12-inch Dobsonian or Schmidt-Cassegrain |
m ≤ 14.5 | ❌ Below limit | ❌ 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 |
Planetary Safety Note: Even though ASASSN-18dn was a titanic explosion, our planet sits safely outside the lethal 50–100 light-year kill zone. At a distance of 571.6 Million Light-Years, the blast poses zero physical hazard to Earth's biosphere.
Cataloged supernovae closest to ASASSN-18dn in discovery time, spatial sky neighborhood, and cosmological lookback epoch:
❓ Frequently Asked Questions About ASASSN-18dn
What type of supernova is ASASSN-18dn and what kind of star exploded? Astrophysics & Progenitor
What was the progenitor star doing in the millions of years leading up to ASASSN-18dn? Astrophysics & Progenitor
How far away is ASASSN-18dn from Earth and how old is the light reaching us? Cosmic Distance & Time
What does the cosmological redshift of ASASSN-18dn tell us about the expansion of space? Cosmic Distance & Time
How bright did ASASSN-18dn become at its peak, and how many Suns does that equal? Explosion Energetics
How much total energy was released by ASASSN-18dn, and where did that energy go? Explosion Energetics
How fast are the supernova ejecta and shockwave of ASASSN-18dn expanding through space? Explosion Energetics
What powers the prolonged glow of ASASSN-18dn weeks and months after detonation? Radioactive Engine
What chemical elements did ASASSN-18dn create and disperse into the universe? Nucleosynthesis & Elements
Did ASASSN-18dn leave behind a black hole, a neutron star, or nothing at all? Cosmic Remnant
What will ASASSN-18dn's explosion site look like in 1,000 to 10,000 years? Cosmic Remnant
In which galaxy did ASASSN-18dn explode, and where is it located relative to the galactic center? Galactic Environment
Where is ASASSN-18dn located in the night sky and which constellation is it in? Sky Coordinates
How much Milky Way interstellar dust obscures our view of ASASSN-18dn? Interstellar Dust
Across which photometric filter bands was ASASSN-18dn monitored? Astronomical Observations
What did astronomical spectroscopy reveal about ASASSN-18dn's chemical makeup? Astronomical Observations
Who discovered ASASSN-18dn and how was it first detected? Discovery & History
How many scientific publications and observatories have contributed data to ASASSN-18dn? Scientific Research
What other names and survey identifiers exist for ASASSN-18dn? Cross-Identifications
AT2018yd. 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).