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Starts With A Bang

Scientists May Have Just Found The Youngest Neutron Star Ever

It comes from a supernova seen just 33 years ago, and it doesn’t pulse.

33 years ago, a supernova occurred just 168,000 light-years from Earth.

This new image of the supernova remnant SN 1987A was taken by the NASA/ESA Hubble Space Telescope in January 2017 using its Wide Field Camera 3 (WFC3). Since its launch in 1990 Hubble has observed the expanding dust cloud of SN 1987A several times and this way helped astronomers to create a better understanding of these cosmic explosions. (NASA, ESA, AND R. KIRSHNER (HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS AND GORDON AND BETTY MOORE FOUNDATION) AND P. CHALLIS (HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS))

Dubbed SN 1987A, it was the closest supernova directly observed since 1604.

In 1604, the last naked-eye supernova to occur in the Milky Way galaxy happened, known today as Kepler’s supernova. Although the supernova faded from naked-eye view by 1605, its remnant remains visible today, as shown here in an X-ray/optical/infrared composite. The bright yellow “streaks” are the only component still visible in the optical. (NASA/ESA/JHU/R.SANKRIT & W.BLAIR)

We first detected the neutrinos from it, and then, hours later, the explosive light.

When neutrinos from the supernova explosion SN 1987a arrived on Earth, they passed through enormous tanks of matter lined with photomultiplier tubes, creating a signal based on neutrino interactions. This marked the birth of neutrino astronomy beyond the Sun, a science that has advanced tremendously over the past few decades. (SUPER KAMIOKANDE COLLABORATION)

Originating from the Large Magellanic Cloud, it was briefly visible to human eyes.

The remnant of supernova 1987a, located in the Large Magellanic Cloud some 165,000 light years away. It was the closest observed supernova to Earth in more than three centuries, and reached a maximum magnitude of +2.8, clearly visible to the naked eye and significantly brighter than the host galaxy containing it. (NOEL CARBONI & THE ESA/ESO/NASA PHOTOSHOP FITS LIBERATOR)

For years, scientists examined this cataclysm’s afterglow, observing the bright, expanding gaseous shells.

For the past 33 years, astronomers have used the best tools available at humanity’s disposal to track the evolution of both the inner and outer components of the remnants of the famous, close supernova, SN 1987A. The inner, dusty core has remained mysterious, but the outer, expanding gaseous layers have revealed telling details for a long time. (X-RAY: NASA/CXC/U.COLORADO/S.ZHEKOV ET AL.; OPTICAL: NASA/STSCI/CFA/P.CHALLIS)

But inside, embedded within dusty clouds, a remnant core must exist.

This montage shows the evolution of the supernova SN 1987A between 1994 and 2016, as seen by the NASA/ESA Hubble Space Telescope. The supernova explosion was first spotted in 1987 and is among the brightest supernovae within the last 400 years. The outward-moving shockwave of material continues to collide with earlier ejecta, leading to brightening events at later times. (NASA, ESA, AND R. KIRSHNER (HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS AND GORDON AND BETTY MOORE FOUNDATION) AND P. CHALLIS (HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS))

SN 1987A was a type II supernova: a blue supergiant exploding at its life cycle’s end.

The stars within the Tarantula nebula, part of the complex containing the remnant of SN 1987A, also contain the enormous star cluster 30 Doradus, which contain some of the brightest, most massive blue supergiant stars known to humanity. Many of them will end their lives in type II supernovae, giving rise to neutron star or black hole remnants. (NASA, ESA, AND E. SABBI (ESA/STSCI); ACKNOWLEDGMENT: R. O’CONNELL (UNIVERSITY OF VIRGINIA) AND THE WIDE FIELD CAMERA 3 SCIENCE OVERSIGHT COMMITTEE)

These explosions always create either neutron stars or black holes, but none had yet been discovered.

The anatomy of a very massive star throughout its life, culminating in a Type II Supernova when the core runs out of nuclear fuel. The final stage of fusion is typically silicon-burning, producing iron and iron-like elements in the core for only a brief while before a supernova ensues. We believe that core-collapse supernovae produce a continuous spectrum of neutron stars to black holes, with no other realistic options for the core’s remnant. (NICOLE RAGER FULLER/NSF)

Many anticipated a central pulsar’s presence: analogous to the Crab Nebula.

Five different combined wavelengths show the true magnificence and diversity of phenomena at play in the Crab Nebula. The X-ray data, in purple, shows the hot gas/plasma created by the central pulsar, which is clearly identifiable in both the individual and the composite image. (G. DUBNER (IAFE, CONICET-UNIVERSITY OF BUENOS AIRES) ET AL.; NRAO/AUI/NSF; A. LOLL ET AL.; T. TEMIM ET AL.; F. SEWARD ET AL.; CHANDRA/CXC; SPITZER/JPL-CALTECH; XMM-NEWTON/ESA; AND HUBBLE/STSCI)

But not all neutron stars pulse; some simply emit high-temperature radiation.

The Atacama Large Millimetre/submillimetre Array, as photographed with the Magellanic clouds overhead. A large number of dishes close together, as part of ALMA, helps bring out many of the faintest details at lower resolutions, while a smaller number of more distant dishes helps resolve the details from the most luminous locations. This has resolved features in dust clouds 168,000 light-years away to unprecedented detail. (ESO/C. MALIN)

ALMA, a high-resolution radio telescope array, just revealed a telling, critical signature.

Features in the central dusty core of the SN 1987A remnant, color coded by temperature, reveals a hot source of radiation shrouded in dust. Based on the inferred temperature and flux from the source, it should be a very young, hot neutron star seen in an earlier stage than any ever discovered thus far. (CARDIFF UNIVERSITY / P. CIGAN ET AL.)

ALMA saw a hot “blob” in the dusty center of SN 1987A’s remnant.

Extremely high-resolution ALMA images revealed a hot “blob” in the dusty core of Supernova 1987A (inset), which could be the location of the missing neutron star. The red color shows dust and cold gas in the center of the supernova remnant, taken at radio wavelengths with ALMA. The green and blue hues reveal where the expanding shock wave from the exploded star is colliding with a ring of material around the supernova. (ALMA (ESO/NAOJ/NRAO), P. CIGAN AND R. INDEBETOUW; NRAO/AUI/NSF, B. SAXTON; NASA/ESA)

It’s located exactly where the observed explosion would “kick” a remnant core.

This Wolf–Rayet star is known as WR 31a, located about 30,000 light-years away in the constellation of Carina. The outer nebula is expelled hydrogen and helium, while the central star burns at over 100,000 K. In the relatively near future, this star will explode in a supernova, enriching the surrounding interstellar medium with new, heavy elements, and likely imparting a significant kick to the stellar remnant left behind. (ESA/HUBBLE & NASA; ACKNOWLEDGEMENT: JUDY SCHMIDT)

Black holes can’t heat dust sufficiently; a very young neutron star is required.

Neutron stars are small objects, perhaps just 25-to-40 km across, but containing more mass than even the Sun; they’re like one giant atomic nucleus. In the early stages of life, they can be tremendously hot, with temperatures greater than even the hottest, bluest stars, but only emitting small amounts of overall luminosity, as their radiating surface area is tiny. (NASA)

It’s the youngest neutron star ever discovered: 33 years old.

The Cassiopeia A supernova remnant was not visible to the naked eye, but astronomers have determined that it occurred in the 2nd half of the 17th century based on the remnant’s properties. There is a neutron star that has been found at the center, but it’s some ~320 years older than the remnant of SN 1987A. (NASA, ESA, AND THE HUBBLE HERITAGE (STSCI/AURA)-ESA/HUBBLE COLLABORATION. ACKNOWLEDGEMENT: ROBERT A. FESEN (DARTMOUTH COLLEGE, USA) AND JAMES LONG (ESA/HUBBLE))

As its evolution continues, we may even someday directly see it pulsing.

As the core region of the SN 1987A remnant continues to evolve, the central dusty region will cool off and much of the radiation obscured from it will become visible, while the central remnant will continue to cool and evolve as well. It’s conceivable, when this occurs, that periodic radio pulses will become observable, revealing whether the central neutron star is a pulsar or not. (ALMA (ESO/NAOJ/NRAO), P. CIGAN AND R. INDEBETOUW; NRAO/AUI/NSF, B. SAXTON; NASA/ESA)

Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.

Ethan Siegel is the author of Beyond the Galaxy and Treknology. You can pre-order his third book, currently in development: the Encyclopaedia Cosmologica.


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