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A star INSIDE a star: Scientists discover neutron star within a supergiant 200,000 light-years from Earth
- Astronomers have found a strange hybrid star using a telescope in Chile
- The so-called Thorne-Żytkow object consists of a neutron star that was swallowed by a much larger red supergiant
- Such objects were first predicted to exist in 1975 by astronomers Dr Kip Thorne and Dr Anna Żytkow
- They are thought to occur when a neutron star collides with a red supergiant and is absorbed
- The exact process by which this happens though is not well understood
- HV 2112, the object that was found, is 200,000 light-years away
By Jonathan O'Callaghan for MailOnline
In 1975 astronomers Dr Kip Thorne and Dr Anna Żytkow predicted the existence of a star within a star, dubbed a Thorne-Żytkow object.
They suggested one would form when a neutron star collided with a supergiant, being swallowed inside its huge companion.
And now almost 40 years later the evidence for such an object has been found, providing astronomers with a fascinating and bizarre new space object to study.
Astronomers have found a strange double star using a telescope in Chile. The so-called Thorne-Żytkow object consists of a neutron star that was swallowed by a much larger red supergiant. This can occur if two stars are orbiting each other, as shown in this illustration, and one is pushed into the other
Thorne-Żytkow objects (TŻOs) are hybrids of red supergiant and neutron stars that, from the outside, resemble regular red supergiants such as Betelgeuse in Orion.
Their chemical signatures are different from such stars, however, due to the unique activity taking place inside.
And amazingly, while regular stars are powered by nuclear fusion in their cores, TŻOs are actually powered by the absorbed neutron star.
The discovery of one of these incredible objects was announced earlier this year, reports Amy Teitel for Motherboard.
The astronomers made their discovery with the 6.5-metre (21.3 feet) Magellan Clay telescope on Las Campanas in Chile.
They examined the spectrum of light emitted from apparent red supergiants, which tells them what elements are present.
When the spectrum of one particular star - HV 2112 in the Small Magellanic Cloud 200,000 light-years away - was first displayed, the observers were quite surprised by some of the unusual features.
Such objects were first predicted to exist in 1975 by astronomers Dr Kip Thorne and Dr Anna Żytkow. They are thought to occur when a neutron star (shown in illustration) collides with a red supergiant and is absorbed. The exact process by which this happens though is not well understood
Project leader Dr Emily Levesque of the University of Colorado Boulder and her colleagues took a close look at the subtle lines in the spectrum and found that it contained excess rubidium, lithium and molybdenum.
- WHAT IS A NEUTRON STAR?
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When the core of a massive star undergoes gravitational collapse at the end of its life, protons and electrons are literally scrunched together, leaving behind one of nature's most wondrous creations: a neutron star.
Neutron stars cram roughly 1.3 to 2.5 solar masses into a city-sized sphere perhaps 12 miles (20 kilometers) across.
Matter is packed so tightly that a sugar-cube-sized amount of material would weigh more than 1 billion tons, about the same as Mount Everest.
Source: nasa.gov
Past research has shown that normal stellar processes can create each of these elements, but high abundances of all three of these at the temperatures typical of red supergiants is a unique signature of TŻOs.
‘Studying these objects is exciting because it represents a completely new model of how stellar interiors can work,’ said Dr Levesque.
‘In these interiors we also have a new way of producing heavy elements in our universe.
‘You've heard that everything is made of “star stuff” - inside these stars we might now have a new way to make some of it.’
And Dr Żytkow, who has now seen her prediction be validated, said: ‘I am extremely happy that observational confirmation of our theoretical prediction has started to emerge.’
‘Since Kip Thorne and I proposed our models of stars with neutron cores, people were not able to disprove our work.
‘If theory is sound, experimental confirmation shows up sooner or later.
‘So it was a matter of identification of a promising group of stars, getting telescope time and proceeding with the project.’
The astronomers made their discovery with the 6.5-meter Magellan Clay telescope on Las Campanas, in Chile (pictured). They examined the spectrum of light emitted from apparent red supergiants, which tells them what elements are present, and found one called HV 2112 was likely one of these bizarre hybrid objects
The team is careful to point out that HV 2112 displays some chemical characteristics that don't quite match theoretical models.
Co-author of the study Dr Philip Massey of Lowell Observatory in Flagstarr, Arizona points out: ‘We could, of course, be wrong.
‘There are some minor inconsistencies between some of the details of what we found and what theory predicts.
‘But the theoretical predictions are quite old, and there have been a lot of improvements in the theory since then.
‘Hopefully our discovery will spur additional work on the theoretical side now.’
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