After decades of searching, astronomers have finally found the collapsed core of the nearest supernova recorded in recent history.

Supernova 1987A
This Hubble Space Telescope image shows Supernova 1987A within the Large Magellanic Cloud, a neighboring galaxy to our Milky Way.
NASA / ESA / R. Kirshner (Harvard-Smithsonian Center for Astrophysics and Gordon and Betty Moore Foundation) / M. Mutchler and R. Avila (STScI)

In the 33 years since a supernova blew up in one of our nearest neighboring galaxies, astronomers haven’t been able to solve the mystery of what happened to the star. Now, we may finally have an answer.

The Supernova 1987A was one of the most-observed supernovae in history, exploding in the Large Magellanic Cloud just 168,000 light-years away. Telescopes around the globe and in space captured the blast wave, which illuminated three overlapping rings of material that had likely blown off in the star’s final days.

Neutrinos received at Earth right after the supernova indicated that the collapsed object ought to be a neutron star. But astronomers were unable to find any sign of a neutron star. Dust obscures the center of the blast. Some even wondered if a black hole had resulted instead.

Closer study showed that the gaseous remains of the star’s outer layers were slightly off-kilter, hinting that whatever compact object had formed in the blast — whether neutron star or black hole — it had received a kick away from the center of the explosion.

Then, new observations from the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile hinted that the search might be at an end. Phil Cigan (Cardiff University, UK) and colleagues used the array of radio antennas to zero in on a blob of “warm” dust. At 33 kelvin above absolute zero, the blob will hardly heat your feet at night, but it’s warm enough to be an anomaly. That study appeared in 2019 in the Astrophysical Journal (preprint available here).

Dust-enshrouded neutron star in Supernova 1987A
ALMA images of Supernova 1987A revealed a warm blob in the dusty core (inset), which might be heated by an enshrouded neutron star. At right, the red color shows radio emission from dust and gas detected by ALMA, green represents visible light detected by the Hubble Space Telescope, and blue shows the hot, X-ray-emitting gas detected by the Chandra X-ray Observatory. The green and blue emissions mark where the expanding shock wave from the exploded star is colliding with a ring of material around the supernova. In 1987, the light from the supernova set the ring aglow, and the ring has continued to brighten as the ejected gas slams into it.
ALMA (ESO / NAOJ / NRAO) / P. Cigan and R. Indebetouw / NRAO / AUI / NSF / B. Saxton / NASA / ESA

In a separate more recent study, which will also appear in the Astrophysical Journal (preprint available here), Dany Page (National Autonomous University of Mexico) and colleagues show that — out of a smorgasbord of possible alternatives — the only viable explanation seems to be that the dust is warmed by the light of a newborn neutron star. What’s more, they showed that the dust blob overlaps the predicted location of the kicked-out core.

Interestingly, the neutron star’s emission suggests it’s not a spinning, jet-beaming pulsar. Just a regular ol’ core crushed so hard that almost all of it is neutrons.

If everything pans out, then NS 1987A will be the youngest neutron star ever observed.

Read more in the NRAO press release.

Advertisement

Comments


Image of Rod

Rod

August 3, 2020 at 9:43 am

Calling the area 'the blob' sounds similar to the 1958 movie with Steve McQueen, 'The Blob' 🙂 You can watch short trailers using BING or Google searches. The angular resolution reported for this blob by ALMA is 80 mas. At 51.4E+3 pc distance, the size of this blob is at least 4112 AU across 🙂 The ALMA blob in SN1987A is even bigger than the blob in the 1958 movie 🙂

You must be logged in to post a comment.

Image of Peter Wilson

Peter Wilson

August 3, 2020 at 12:46 pm

Is the neutron star not a spinning, jet-beaming pulsar...or is the jet not pointed our direction?

You must be logged in to post a comment.

Image of Anthony Barreiro

Anthony Barreiro

August 3, 2020 at 4:39 pm

From Page et al. (2020)'s abstract:

" ... The infrared excess could be due to the decay of isotopes like 44Ti, accretion luminosity from a neutron star or black hole, magnetospheric emission or a wind originating from the spindown of a pulsar, or thermal emission from an embedded, cooling neutron star (NS 1987A). It is shown that the last possibility is the most plausible as the other explanations are disfavored by other observations and/or require fine-tuning of parameters. Not only are there indications the dust blob overlaps the predicted location of a kicked compact remnant, but its excess luminosity also matches the expected thermal power of a 30 year old neutron star. Furthermore, models of cooling neutron stars within the Minimal Cooling paradigm
readily fit both NS 1987A and Cas A, the next-youngest known neutron star. ... "

I don't understand most of the math and physics in the body of the article, but I am tickled by equations such as:

M(blob) Ti,0 ≥ (4.5 − 10.5) × 10−6 M(Sun)

You must be logged in to post a comment.

Image of Monica Young

Monica Young

August 5, 2020 at 3:48 pm

Hi Peter - good question! The main point of the authors as I understand it is that if the neutron star is a spinning, jet-beaming pulsar, then the pulsar's spindown is not what's heating the dust blob. The blob's infrared radiation seems to be coming from the neutron star's thermal emission only.

You must be logged in to post a comment.

Image of AJames

AJames

August 9, 2020 at 9:20 pm

Not all neutron stars become pulsars. This has something to do with the angular momentum which spins-up the small remnant enabling the radio jet generation. This probably something to do with its supernova core and how material is blown out after the supernova collapse.
An excellent ATNF article "An Introduction to Pulsar" is here. [1]
Frankly, astronomers don't exactly how much time must pass before the neutron pulsar appears, but not quite yet it seems.

You must be logged in to post a comment.

Image of Rod

Rod

August 3, 2020 at 8:49 pm

Anthony Barreiro, I found the preprint abstract a bit more easier to read and understand. "Fits to the far-infrared--millimeter spectral energy distribution give ejecta dust temperatures of 18--23K. We revise the ejecta dust mass to Mdust=0.2−0.4M⊙ for carbon or silicate grains, or a maximum of <0.7M⊙ for a mixture of grain species, using the predicted nucleosynthesis yields as an upper limit.", https://arxiv.org/abs/1910.02960. This is where I observed the 80 mas high angular resolution images from ALMA and calculated the size in AU. The blob apparently has quite a bit of dust too. 0.4 solar mass is more than 133,000 earth masses. The figures you cited were for a mass range 4.5 to 10.5 x 10^-6 solar masses or some 1.66 earth masses using 5E-6 solar masses.

You must be logged in to post a comment.

Image of Anthony Barreiro

Anthony Barreiro

August 4, 2020 at 3:02 pm

Rod, I'm just amused that the authors would call a variable M(blob). It's a smart decision, because the reader knows what they're talking about, but I would have expected them to use a more "scientific" sounding term.

You must be logged in to post a comment.

You must be logged in to post a comment.