Bubbles with Titanium Trigger Titanic Explosions


Apr 21, 2021

Supernova remnant Cassiopeia A (Cas A),

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Scientists have found fragments of titanium blasting out of a famous supernova. This discovery, made with NASA’s Chandra X-ray Observatory, could be a major step in pinpointing exactly how some giant stars explode.

This work is based on Chandra observations of the remains of a supernova called Cassiopeia A (Cas A), located in our galaxy about 11,000 light-years from Earth. This is one of the youngest known supernova remnants, with an age of about 350 years.

For years, scientists have struggled to understand how massive stars – those with masses over about 10 times that of the Sun – explode when they run out of fuel. This result provides an invaluable new clue.

“Scientists think most of the titanium that is used in our daily lives — such as in electronics or jewelry — is produced in a massive star’s explosion,” said Toshiki Sato of Rikkyo University in Japan, who led the study that appears in the journal Nature. “However, until now scientists have never been able to capture the moment just after stable titanium is made.”

When the nuclear power source of a massive star runs out, the center collapses under gravity and forms either a dense stellar core called a neutron star or, less often, a black hole. When a neutron star is created, the inside of the collapsing massive star bounces off the surface of the stellar core, reversing the implosion.

The heat from this cataclysmic event produces a shock wave – similar to a sonic boom from a supersonic jet – that races outwards through the rest of the doomed star, producing new elements by nuclear reactions as it goes. However, in many computer models of this process, energy is quickly lost and the shock wave’s journey outwards stalls, preventing the supernova explosion.

Recent three-dimensional computer simulations suggest that neutrinos — very low-mass subatomic particles — made in the creation of the neutron star play a crucial role in driving bubbles that speed away from the neutron star. These bubbles continue driving the shock wave forward to trigger the supernova explosion.

With the new study of Cas A, the team discovered powerful evidence for such a neutrino-driven explosion. In the Chandra data they found that finger-shaped structures pointing away from the explosion site contain titanium and chromium, coinciding with iron debris previously detected with Chandra. The conditions required for the creation of these elements in nuclear reactions, such as the temperature and density, match those of bubbles in simulations that drive the explosions.

The titanium that was found by Chandra in Cas A and that is predicted by these simulations is a stable isotope of the element, meaning that the number of neutrons its atoms contain implies that it does not change by radioactivity into a different, lighter element. Previously astronomers had used NASA’s NuSTAR telescope to discover an unstable isotope of titanium in different locations in Cas A. Every 60 years about half of this titanium isotope transforms into scandium and then calcium.

“We have never seen this signature of titanium bubbles in a supernova remnant before, a result that was only possible with Chandra’s incredibly sharp images,” said co-author Keiichi Maeda of Kyoto University in Japan. “Our result is an important step in solving the problem of how these stars explode as supernovae.”

“When the supernova happened, titanium fragments were produced deep inside the massive star. The fragments penetrated the surface of the massive star, forming the rim of the supernova remnant, Cas A,” said co-author Shigehiro Nagataki of the RIKEN Cluster for Pioneering Research in Japan.            

These results strongly support the idea of a neutrino-driven explosion to explain at least some supernovae.

“Our research could be the most important observational result probing the role of neutrinos in exploding massive stars since the detection of neutrinos from Supernova 1987A,” said co-author Takashi Yoshida of Kyoto University in Japan.

Astronomers used over a million and half seconds, or over 18 days, of Chandra observing time from the supernova Cassiopeia A (Cas A) taken between 2000 and 2018. The amount of stable titanium produced in Cas A exceeds the total mass of the Earth.

These results have been published in the April 22, 2021 issue of Nature. In addition to Sato, Maeda, Nagataki and Yoshida, the authors of the paper are Brian Grefenstette (California Institute of Technology in Pasadena, California), Brian J. Williams (NASA Goddard Space Flight Center in Greenbelt, Maryland), Hideyuki Umeda (University of Tokyo in Japan), Masaomi Ono (RIKEN Cluster for Pioneering Research in Japan), and Jack Hughes (Rutgers University in Piscataway, New Jersey).

NASA’s Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center controls science from Cambridge Massachusetts and flight operations from Burlington, Massachusetts.

Image credit: NASA/CXC/RIKEN/T. Sato et al.; NuSTAR: NASA/NuSTAR)

Read more from NASA’s Chandra X-ray Observatory.

For more Chandra images, multimedia and related materials, visit:


Last Updated: Apr 23, 2021

Editor: Lee Mohon

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April 30, 2021 3:37 am

This is one of the few areas where the simulations are completely based on known physics. Quantum Electrodynamics (QED) simulations have predicted physical results which were then measured in experiments in the real world. In one in particular, a laser beam striking an a microscopic pellet was predicted to produce a shock wave racing around the pellet. An ultra-high speed camera actually captured the predicted shock wave. Originally it was expected that the pellet would simply vaporize to a plasma during the energy exchange. The action was to take place in the ignition facility of a fusion reactor. IIRC

While there are still major discoveries remaining to be made in the quantum world, at least some of the tools can contribute to unexpected discoveries.

M Courtney
April 30, 2021 3:43 am

Real science. Observations, hypotheses, testing.
Amazing that neutrinos can drive anything when they barely interact with anything else in this universe.

Reply to  M Courtney
April 30, 2021 4:45 pm

What is the purpose of neutrinos? Now we may know.

Reply to  Anti-griff
May 1, 2021 1:06 am

The purpose for which neutrinos where first proposed was to maintain conservation of lepton number and conservation of energy in beta decay.

April 30, 2021 3:52 am

“Bubbles with Titanium Trigger Titanic Explosions”
I thought it hit an iceberg.

(I couldn’t help myself)

Reply to  Speed
April 30, 2021 4:14 am

Obviously you thought wrong.

*Scratching the head*

Last edited 13 days ago by whiten
Geoff Sherrington
Reply to  Speed
April 30, 2021 4:16 am

Yeh, I thought it was a trailer for a new movie with Bubbles, a non-female champagne drinking playboy meeting Titanium, a non-male blonde, leading to a cata-orgasmic bed event. Some use of big Ts.
Seriously, I disagree with comments about observation, science etc. Authors should not be so certain of imagined events as to express them like “The fragments penetrated the surface of the massive star, forming the rim of the supernova remnant.” Have they seen a rim? Are these fragments soft enough to emit a spectrum while cold enough to chip at rocks?
Geoff S

Abolition Man
Reply to  Geoff Sherrington
April 30, 2021 4:37 am

All the best looking models were consulted; for both of your paragraphs!
Also, if you don’t mind, please stop gendering your playboys and blondes; it’s likely to be very triggering for the trolls!

Last edited 13 days ago by Abolition Man
Abolition Man
April 30, 2021 4:34 am

I thought from the second paragraph that this article was going to be about newly discovered particles that travel faster than light! How else do you explain 350 year old super nova that is 11,000 light years away being visible to Chandra? But then I realized that these are REAL scientists, not Climastrologists, so it’s probably just a mistake.
Did they perhaps mean 11,350 years old?

Tom in Florida
Reply to  Abolition Man
April 30, 2021 5:30 am

I thought it was quite obvious that it has been known for 350 years, not the age of the supernova it self.

Abolition Man
Reply to  Tom in Florida
April 30, 2021 6:22 am

Not to quibble, but the inexactitude of scientists and scientific articles is one of the major problem with ALL scientific endeavors now; especially climate science as is so often seen! They could have have said that light arrived, or that the super nova was first seen 350 years ago. What they said is WRONG!
Forgive me if trying to poke a little humor at the error offends you!

Tom in Florida
Reply to  Abolition Man
April 30, 2021 8:39 am

Not offended, and I get your point.

Abolition Man
Reply to  Tom in Florida
April 30, 2021 10:21 am

You, sir, are a scholar and a gentleman! Cheers!

Last edited 13 days ago by Abolition Man
Michael S. Kelly
Reply to  Abolition Man
April 30, 2021 12:12 pm

At least they didn’t write “The supernova occurred 11,000 years ago last Friday.”

Abolition Man
Reply to  Michael S. Kelly
April 30, 2021 1:35 pm

Of course not, Michael!
With titanic explosions, triggered by titanium bubbles it had to be 11,350 years ago last Tuesday!

Reply to  Tom in Florida
April 30, 2021 7:57 am

Yes Tom.

Even the mass of that Titanium is estimated and clearly shown to be roughly that of Earth.

But still somehow, after this point is made,
no size of this Titanium “Earth” is given for consideration.
Like the spatial size.

Or just me… must have missed it!

Well, even the estimated Earth mass is to be considered as correct only in a 50/50.
While in the same time the size measurements for Earth, quite clearly in no any doubt or dispute.

*scratching the head again*


Tom Abbott
April 30, 2021 5:29 am

There must be a lot of neutron stars floating around in the universe.

April 30, 2021 6:07 am

Just as well that our local star is relatively docile ‘creature’, currently waking-up from its two year hibernation in order to spend most of this decade shedding off some of its surplus energy, for which we are eternally grateful.
April data graph is in the link, while the image below is from previous month stored on elsewhere on i1.wp.com and I’m unable to delete/remove it with the available edit control.

Last edited 13 days ago by Vuk
Bruce Cobb
April 30, 2021 8:20 am

“Bubbles With Titanium” would be a good name for a band.

Abolition Man
Reply to  Bruce Cobb
April 30, 2021 10:29 am

Wasn’t that one of Madonna’s early wardrobe malfunctions?

April 30, 2021 8:33 am

match those of bubbles in simulations that drive the explosions.
Pretty sure simulations are not driving the explosions.

April 30, 2021 8:39 am

energy is quickly lost and the shock wave’s journey outwards stalls, preventing the supernova explosion.
Not enough CO2 to reach the tipping point.

April 30, 2021 8:53 am

However, until now scientists have never been able to capture the moment just after stable titanium is made

Ti48 comes from silicon burning in the shock wave during the first day after supernova, initially forming Cr48 which then (if it doesn’t capture another helium) undergoes a 16 hr half life decay (via two beta+ decays) to form a stable Ti48 nucleus.

The star is 350 years after supernova so it seems an exaggeration to say we are “capturing the moment” of creating Titanium here.

Abolition Man
Reply to  menace
April 30, 2021 10:38 am

You’re right, of course; and it would have been nice if they had included more data like the size of the remnant and a timeline of the events after the collapse and explosion! Thanks for filling in some of the gaps!

Michael S. Kelly
Reply to  menace
April 30, 2021 12:21 pm

I just invested a bunch of money in a futures contract to buy titanium at $0.01 per quadrillion tonnes, so when the stuff arrives here, I’ll have the market cornered.

Admittedly, it’s a long contract…

Reply to  menace
May 2, 2021 11:33 am

It irks me when these press releases don’t cite the published article. Link below, and it’s paywalled, or I would have more to say.

I am fairly certain they are not talking about Ti48 created hours or days after explosion. They are more likley talking about new processes occuring during the explosion, typically milliseconds to a second or two after it begins.

I’ve been following with some interest the work being done to understand the workings of core collapse stellar explosions. Their 1-D and 2-D models suffered from a severe lack of ability to explode. The shock wave always or usually stalled and that was the end of it.

With 3-D models the simulations had neutrinos generating convective activity which can get the shock wave going again. That’s really oversimplified tho, and there are plenty of video presentations from lectures and conferences out there if you are interested in learning more.

I’ve always thought it was fascinating that all of the lay-person level science documenteries about supernovae clearly explained how the star explodes, but in reality scientists had not a clue why they did so.


Gary Pearse
April 30, 2021 2:32 pm

On earth Ti is fairly abundant occurring in the minerals ilmenite (FeTiO2) and rutile (TiO2), which are abundant in granitic rocks and, hence, in beach sands from which much of the Ti used is produced. They are also abundant in ferro-carbonatites (calcium-iron carbonate magmas) associated with rare earth deposits and usually directly with columbite, a niobium(Ta) oxide.

“Every 60 years about half of this titanium isotope transforms into scandium and then calcium.”

Interestingly, terrestrial Ti is also, in its minerals and associated minerals, a companion of calcium, iron and rare earths including scandium (which some, as I do, consider a rare earth along with its fellows yttrium and the 15 Lanthanides that lie below it as Group 3 elements in the periodic table.

This supports an idea I have from other evidence about the relationship between the association of elements in mineral deposits (say Cu-Zn) and their cosmic creation. That is to say that in ‘earth processes’ there is no random association of elements. When molten or dissolved, they appear to seek each other out!

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