Up next in 10
On February 12, 2026, astronomers described a star in Andromeda that went dark. Hubble cannot find it. A black hole was born, and there was no supernova to mark it.
This video walks the clock inside a dying massive star: t=0 when silicon burning ends, t=1 second of free fall, and the millisecond when a proto-neutron star has no surface left.
Timestamps
0:00 A disappearance in Andromeda
0:42 The Clock Starts
1:55 Fuel That Runs Out
3:20 The Iron Trap
4:30 Bounce And Stall
5:40 Neutrinos Leave First
6:55 The Part That Actually Matters
8:10 When There Is No Explosion
9:25 The Horizon Itself
10:40 What Does Not Happen
Numbers are from published astronomy. Where measurements have ranges, we say about.
#blackhole #astronomy #supernova #astrophysics #space #neutronstar #scienceexplained #failedsupernova
Educational explainer only. This is not a prediction that a nearby star collapses tomorrow, and it is not a claim that Earth is in danger from a stellar-mass black hole.
Visuals are original AI-generated stills. Audio may be synthetic. Not medical, legal, or financial advice.
Show More Show Less View Video Transcript
0:00
On February 12th, 2026, astronomers
0:03
published a star in the Andromeda galaxy
0:05
that went dark without a supernova. The
0:08
object is called M31204DS1.
0:12
It sits about 2.5 million lighty years
0:14
from Earth. It formed at about 13 times
0:17
the mass of the sun, and by the end,
0:19
stellar winds had stripped it down to
0:21
about five. In 2014, it brightened in
0:24
the infrared. From 2017 to 2022, its
0:27
optical light fell by a factor of about
0:30
10,000. Hubble cannot find the star. The
0:33
birth of a black hole, in this case, was
0:35
not an explosion. It was a
0:37
disappearance.
0:39
The clock starts. You are inside an iron
0:41
core about as wide as Earth, holding
0:44
about 1.4 solar masses at the center of
0:47
a star that has already burned hydrogen
0:49
for about 7 million years. At t equals
0:52
z, silicon burning has just finished.
0:54
For a 25 solar mass star, that silicon
0:58
stage lasts about one day. Oxygen before
1:01
it lasts months. Carbon lasts centuries.
1:04
Helium lasts hundreds of thousands of
1:06
years. Hydrogen lasts millions. Nutrinos
1:10
are already stealing energy from the
1:11
core. And the temperature is past 3
1:14
billion Kelvin. If you could stand
1:16
there, the density would already be a
1:18
million times water. and gravity would
1:21
be winning on a clock you can count on
1:23
your fingers. At TE or C equals 1
1:26
second, the core is in freef fall. At TE
1:28
equals 5 seconds, if nothing holds it,
1:31
the inner core has already passed
1:33
nuclear density.
1:35
Fuel that runs out. The first problem is
1:39
a schedule. A massive star is a furnace
1:42
that has to keep lighting a hotter fuel
1:44
because the last one ran out. Hydrogen
1:47
becomes helium. Helium becomes carbon.
1:49
Carbon becomes neon. Neon becomes
1:52
oxygen. Oxygen becomes silicon. Silicon
1:55
becomes iron peak nuclei, mostly nickel
1:59
56 that later decays to iron 56. Each
2:03
jump needs a hotter, denser core because
2:06
the next nucleus has a stronger electric
2:09
charge and like charges push apart. You
2:12
compress the factory to keep it running.
2:14
For a 25 solar mass star, the numbers
2:16
look like this. Hydrogen about 6.5
2:19
million years. Helium about 685,000
2:22
years. Carbon about 317 years. Neon
2:26
about 321 days. Oxygen about 116 days.
2:31
Silicon about 1 day. Then you hit iron.
2:34
Iron is the trap. Fusing iron costs
2:36
energy instead of paying it. Gamma rays
2:39
start photo disintegrating nuclei which
2:42
costs more. Electrons get captured by
2:44
protons, making neutrons, and the
2:47
reaction dumps nutrinos. The pressure
2:50
that was holding up a star hundreds of
2:52
times wider than the sun is gone. The
2:55
iron trap. You are now in that
2:58
Earth-sized iron sphere. Density climbs
3:01
through 10 billion g per cm, then a
3:04
trillion. Nutrinos that used to stream
3:06
out get trapped at about 10^ the 12th g
3:09
per cime. The collapse time is the freef
3:12
fall time, a few hundred milliseconds.
3:15
The inner core falls. The outer core
3:18
rains in at thousands of kilometers/s.
3:20
When the center hits nuclear saturation
3:22
density, about 2.7 * 10 14th g per cubic
3:27
cm, nuclear matter stiffens like a
3:30
spring that cannot compress. The inner
3:33
core slams to a halt and rebounds. That
3:35
bounce launches a shock. You want that
3:37
shock to be the supernova. For many
3:40
stars, it is. For the ones that make
3:42
stellar black holes, it often is not.
3:45
Bounce and stall. The shock runs out a
3:48
few hundred kilometers and stalls. It
3:51
spends energy ripping iron into protons
3:53
and neutrons. It also has to push
3:56
against the ram pressure of the still
3:58
falling outer core. You are watching a
4:01
logistics failure turn into a physics
4:03
failure. In a 2025 three-dimensional
4:06
simulation, the shock reaches about 170
4:09
km, stalls, and never revives. The
4:13
proton neutron star keeps eating. About
4:16
325 milliseconds after bounce, that
4:19
object is too heavy to exist as a star.
4:22
In a 2023 run of a 40 solar mass
4:25
progenitor, the explosion actually
4:27
launches at about 0.25 25 seconds after
4:30
bounce and the proton neutron star still
4:33
collapses to a black hole about 1.5
4:36
seconds later at a gravitational mass of
4:38
about 2.3 solar masses. A supernova and
4:42
a black hole can share the same second.
4:45
The remnant is born at a few solar
4:47
masses. The envelope may still be on its
4:50
way in. Nutrinos leave first. About 99%
4:56
of the gravitational energy of the
4:58
collapse leaves as nutrinos roughly 10
5:00
to the 53 URG in a burst of seconds.
5:03
Light is still trapped in the envelope.
5:06
On February 23rd, 1987 at 7:35 UTC, came
5:11
the 2 recorded 12 anti-utrinos. The
5:15
Irvine, Michigan Brook Haven detector
5:17
recorded eight. Boxon recorded five. The
5:20
whole burst lasted under 13 seconds. The
5:23
light of SN1 1987A arrived about 3 hours
5:27
later after the shock broke out of the
5:29
surface of a blue super giant about
5:32
160,000 lighty years away in the large
5:35
melanic cloud. That event left a compact
5:38
remnant almost certainly a neutron star.
5:42
The nutrino flash is the birth
5:44
certificate. If the remnant is a black
5:46
hole, the nutrino signal can cut off
5:48
when the radiating surface falls through
5:50
the new horizon. You would not catch
5:53
that cut off from Earth unless the
5:54
collapse happened in our own galaxy.
5:56
Close. 1987A was nearby on cosmic
6:00
scales. And still only a handful of
6:02
particles hit the tanks. The part that
6:05
actually matters. And it gets worse.
6:07
Neutron degeneracy pressure and nuclear
6:10
repulsion have a ceiling. That ceiling
6:12
is the Tolman Oppenheimer Vulkoff limit.
6:16
estimated around two to three solar
6:18
masses for a cold non-rotating neutron
6:21
star. The heaviest well-measured neutron
6:24
stars sit near 2.35 solar masses. Push
6:28
past that and there is no known force
6:30
that keeps the surface. The proton
6:32
neutron star is still hot and still
6:35
accreting, so it can overshoot the limit
6:37
in less than a second. In failed
6:39
explosion calculations, the last
6:42
millisecond of the proton neutron star
6:44
shows central density jumping by a
6:46
factor of about three. Horizon formation
6:49
in coordinate time is under a
6:51
millisecond. After that, the object has
6:54
no radius you can stand on. It has a
6:56
Schwarz child radius 2gm over c^ 2. For
7:00
the sun, that radius is about 3 km. For
7:03
a 10 solar mass hole, it is about 30 km.
7:06
For a few solar mass remnant, you are
7:09
looking at a sphere maybe 10 kilometers
7:11
across and everything that still wants
7:13
to fall has to thread that hole.
7:16
when there is no explosion. March 2009,
7:19
in the spiral galaxy NGC6946,
7:23
about 22 million lighty years away, a
7:25
red super giant of about 25 solar
7:28
masses, cataloged as N6946
7:31
BH1, brightened to at least a million
7:33
times the luminosity of the sun, then
7:36
vanished from optical images by 2015.
7:39
Hubble confirmed the disappearance. A
7:41
faint infrared leftover remains
7:43
consistent with debris falling onto a
7:46
newly formed black hole. That is the
7:48
failed supernova channel. The shock
7:50
never ejects the envelope. Most of the
7:53
star falls in. You do not get a bright
7:55
supernova. You get a star that winks
7:57
out. M31 2014 DS1. The February 2026
8:02
case looks like the same family. A
8:05
hydrogen pore super giant in Andromeda.
8:08
a 2014 infrared bump. Then a fade of
8:11
about 10,000 in optical light, a dusty
8:14
shell expanding at about a 100
8:15
kilometers per second. No fireworks, a
8:18
black hole. Anyway, the horizon itself.
8:21
The event horizon is not a crust. It is
8:24
the last outgoing light ray that never
8:27
makes it to infinity. Inside it, every
8:30
future path points inward. From the
8:32
outside, collapse appears to freeze near
8:35
that radius. The star does not vanish
8:37
from its own clocks in one blink. From
8:40
yours, red shift stretches the last
8:42
photons toward infinity and infrared and
8:45
then radio and then nothing.
8:47
Practically, after a few light crossing
8:49
times, a few milliseconds for a stellar
8:52
mass hole, the object is black. Pair
8:55
that with fallback. Even a successful
8:57
explosion can dump extra mass onto the
9:00
remnant. In that 40 solar mass
9:02
simulation, the hole forms at about 2.3
9:05
solar masses, then accretes another 0.2
9:08
solar masses in 7 seconds. The hole
9:11
grows in the dark under the dying star
9:14
while the outer layers are still
9:15
deciding whether to leave. If the star
9:18
is in a binary, leftover gas can later
9:20
form a disc and scream in X-rays. That
9:24
is how we found Signis X1 in 1964.
9:28
The hole there is about 21 solar masses.
9:31
It did not empty the constellation. It
9:33
sat there and stripped a companion. What
9:36
does not happen? Your night sky does not
9:39
go dark tomorrow. The sun cannot do
9:42
this. The sun will leave a white dwarf
9:44
of about 0.6 solar masses, well under
9:47
the 1.4 solar mass Chandraar limit. A
9:51
stellar mass black hole does not roam
9:53
the neighborhood vacuuming planets.
9:55
Gravity at a large distance is the same
9:57
as the star that died. What changes is
10:00
the size of the object, not the mass you
10:03
already felt from far away. Beetlejuice,
10:06
if it ever collapses, is hundreds of
10:08
light years out and Earth is not in a
10:10
danger zone from a hole of a few tens of
10:13
solar masses at that range. GW1509
10:16
quartor on September 14th, 2015 at
10:20
095045
10:21
UTC was two already born holes about 36
10:25
and 29 solar masses merging more than a
10:28
billion light years away converting
10:30
about three solar masses into
10:32
gravitational waves in about a fifth of
10:35
a second. Ligos 4 km.
#News