Anna Nikola Żytkow (; born 21 February 1947) is a Polish astrophysicist working at the Institute of Astronomy of the

University of Cambridge The University of Cambridge is a Public university, public collegiate university, collegiate research university in Cambridge, England. Founded in 1209, the University of Cambridge is the List of oldest universities in continuous operation, wo ...

. Żytkow and

Kip Thorne Kip Stephen Thorne (born June 1, 1940) is an American theoretical physicist and writer known for his contributions in gravitational physics and astrophysics. Along with Rainer Weiss and Barry C. Barish, he was awarded the 2017 Nobel Pri ...

proposed a model for what is called the

Thorne–Żytkow object A Thorne–Żytkow object (TŻO or TZO), a type of hybrid star, is a conjectured type of star wherein a red giant or Red supergiant star, red supergiant contains a neutron star at its core, formed from the Stellar collision, collision of the gian ...

, which is a star within another star. Żytkow in 2014 was part of the team led by Emily M. Levesque which discovered the first candidate for such an object.

Thorne-Żytkow objects

Working together with

in 1976, Żytkow developed a theoretical model for a new star type, the

(TŻO), which contains either a

neutron star A neutron star is the gravitationally collapsed Stellar core, core of a massive supergiant star. It results from the supernova explosion of a stellar evolution#Massive star, massive star—combined with gravitational collapse—that compresses ...

or a black hole core at the center of a stellar envelope. The evolution of such a star occurs rarely and only two processes exist that define the structure and evolution of a TŻO. In the first process a collision between a neutron star and a normal star, either dwarf or giant, must occur in order to merge the two into a single object. This occurrence is rare since stars do not usually collide with each other. This could only happen in a dense cluster of stars. The second possible evolution of a larger TŻO can occur when a star expands into a red supergiant and engulfs its companion neutron star. A team led by

Emily Levesque Emily Levesque (born 1984) is an American astronomer, author, and associate professor in the Department of Astronomy at the University of Washington. She is known for her work on massive stars and using these stars to investigate galaxy formatio ...

(

University of Colorado at Boulder The University of Colorado Boulder (CU Boulder, CU, or Colorado) is a Public university, public research university in Boulder, Colorado, United States. Founded in 1876, five months before Colorado became a Federated state, state, it is the fla ...

) and including Anna Żytkow found the first viable TŻO candidate using the 6.5-meter Magellan Clay Telescope at the

Las Campanas Observatory Las Campanas Observatory (LCO) is an astronomy, astronomical observatory managed by the Carnegie Institution for Science (CIS). Located in Chile's Atacama Region, it sits about northeast of the city of La Serena, Chile, La Serena. The LCO's telesc ...

in 2014. Żytkow said upon the discovery: "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."

Personal life

Żytkow's career was interrupted by a mountaineering accident that nearly took her life.

Kuiper belt discoveries

In December 1995,

Mike Irwin Michael J. Irwin is a British astronomer. He is the director of the Cambridge Astronomical Survey Unit and one of the discoverers of the Cetus Dwarf galaxy and the Sagittarius Dwarf Elliptical Galaxy. Research Irwin is known worldwide for ...

Scott Tremaine Scott Duncan Tremaine (born 1950) is a Canadian-born astrophysicist. He is a fellow of the Royal Society of London, the Royal Society of Canada and the National Academy of Sciences. Tremaine is widely regarded as one of the world's leading ast ...

, and Anna N. Żytkow collaborated on the survey of two slow-moving objects, which are probable members of the

Kuiper belt The Kuiper belt ( ) is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times ...

. Żytkow and the group followed Edgeworth (1949) and Kuipers (1951) research, which indicates that protoplanetary disks extend beyond Neptune and that the disk material beyond Neptune had not coalesced into planets. This group of planetesimals is now known as the Kuiper belt. Żytkow and the rest of the group members spent most of their time adjusting the focus of the camera and instruments attached to the

Isaac Newton Telescope The Isaac Newton Telescope or INT is a 2.54 m (100 in) optical telescope run by the Isaac Newton Group of Telescopes at Roque de los Muchachos Observatory on La Palma in the Canary Islands since 1984. Originally the INT was situated at He ...

(INT). The group used the

Monte Carlo method Monte Carlo methods, or Monte Carlo experiments, are a broad class of computational algorithms that rely on repeated random sampling to obtain numerical results. The underlying concept is to use randomness to solve problems that might be ...

, which provided multiple simulations in two separate stages. The first stage is the detection rate for images that came from INT as a function of magnitude, which was investigated using artificial images adding to the original frames. The second stage involved examining the detection rate for a series of artificial images from INT that followed the typical slow moving solar system objects (SMO) track. The outcome of this survey was a detection of two new Kuiper belts objects within the area of 0.7 degree sq. to a limiting magnitude mR=23.5.

Publications

* The proper motion of HV2112: a TŻO candidate in the SMC; '' Monthly Notices of the Royal Astronomical Society Letters''; Mar. 2016; Clare C. Worley, Mike J. Irwin, Christopher Tout, Anna N. Żytkow, Morgan Fraser, Robert G. Izzard:

* A Search for Thorne-Zytkow Objects; ''

American Astronomical Society The American Astronomical Society (AAS, sometimes spoken as "double-A-S") is an American society of professional astronomers and other interested individuals, headquartered in Washington, DC. The primary objective of the AAS is to promote the adv ...

''; January 2014; Emily M. Levesque Philip Massey Anna N. Żytkow Nidia Morrell

* HV2112, a Thorne-Zytkow Object or a Super Asymptotic Giant Branch Star; '' Monthly Notices of the Royal Astronomical Society Letters''; 23 June 2014; Christopher Tout, Anna N. Zytkow, Ross P. Church, Herbert Ho Bun Lau

* Discovery of a Thorne-Zytkow object candidate in the Small Magellanic Cloud; '' Monthly Notices of the Royal Astronomical Society Letters''; September 2014; Emily M. Levesque, Philip Massey, Anna N. Zytkow, Nidia Morrell

* Quasi-stars, giants and the Schönberg–Chandrasekhar (SC) limit; ''

Monthly Notices of the Royal Astronomical Society ''Monthly Notices of the Royal Astronomical Society'' (MNRAS) is a peer-reviewed scientific journal in astronomy, astrophysics and related fields. It publishes original research in two formats: papers (of any length) and letters (limited to ...

''; January 2012; Warrick H. Ball, Christopher Tout, Anna N. Żytkow

* FY Aquilae and the gamma-ray burst GB 790331; ''

Astrophysical Journal ''The Astrophysical Journal'' (''ApJ'') is a peer-reviewed scientific journal of astrophysics and astronomy, established in 1895 by American astronomers George Ellery Hale and James Edward Keeler. The journal discontinued its print edition and ...

'', part 2, vol. 433, no. 2, p. L81-L84; 12 July 1994; Mike Irwin, Anna N. Zytkow

* A variable star in the vicinity of the soft γ-ray repeater 1806 – 20; ''

'', vol. 263, iss. 1; 1 July 1993; Mike Irwin Anna N. Żytkow

* The structure and evolution of Thorne-Zytkow objects; ''

'', part 1, vol. 386; Feb. 10, 1992;Robert C. Cannon, P. P. Eggleton, A. N. Zytkow, P. Podsiadlowski

* Giant and supergiant stars with degenerate neutron cores; ''

'', Part 1; Chris Eich; Mark E. Zimmermann; Kip S. Thorne; Anna N. Zytkow; 1 November 1989

* Stationary spherical accretion into black holes. I - Equations of structure; ''

'', vol. 194; Feb., 1981; Kip S. Thorne; Richard A. Flammang, Anna N. Zytkow

* Hydrogen shell flashes in a white dwarf with mass accretion; ''

'', Part 1, vol. 222; 1 June 1978; Bohdan Paczynski, Anna N. Zytkow

* Stars with degenerate neutron cores. I - Structure of equilibrium models; ''

'', part 1, vol. 212; Mar. 15, 1977; Kip S. Thorne;, Anna N. Zytkow

* The relativistic equations of stellar structure and evolution. Stars with degenerate neutron cores. 1: Structure of equilibrium models; ''

'', part 1, vol. 212; Mar. 15, 1977; Kip S. Thorne;, Anna N. Zytkow

* Red giants and supergiants with degenerate neutron cores neutron cores. 1: Structure of equilibrium models; ''

'', vol. 199; 1 July 1975; Kip S. Thorne;, Anna N. Zytkow

References

External links

Publications
1947 births Astronomers at the University of Cambridge Discoverers of minor planets Discoveries by Anna N. Żytkow Living people Polish astrophysicists Polish women physicists Women astrophysicists University of Warsaw alumni {{improve categories, date=November 2022