Tag Archives: neutron stars

Interview with Giovanni Camelio

I was born in Milan, Italy. I took my bachelor and master in Physics at the University of Milan “Degli Studi,” and I took my PhD in Physics in the University of Rome “Sapienza.” I have always wanted to be a scientist; I remember that I chose to become a physicist in high school when I was studying optic waves and in particular the redshift effect. What really impressed me was how the description of that phenomenon was easy and straightforward after putting it in a mathematical form.

The thing I like the most about being a scientist is the possibility to devote my time to study and understand reality. What I really dislike is the rush to publish. This attitude causes the problems that afflict modern science and deprives the work of any pleasure and of its real goal, namely the effort to deepen our understanding of nature.

What is your field of research and/or what project are you involved in at the OKC?
My research field is the study of hot neutron stars. My project here is to implement a code that describes the neutrino diffusion in a rotating neutron star, fully accounting for general relativity effects. We will use this code to study super-massive neutron stars that originate from a binary neutron star merger.

Which of your skills are you most proud of? What new skills would you like to learn in the next year?
I think that my strength as a scientist is my multidisciplinarity (I have worked on different topics in my career) and my intuition. In the next year I would like to have more time to study and improve my mathematical skills.

If you had unlimited funding, to be spent on something scientifically relevant, what would you use it for?
If I had unlimited funding, that in my case specifically means unlimited time, I would work on the problem of determining the oscillation modes of a rotating neutron star. These permit us to study the stability of neutron stars and their gravitational wave emission.

What’s your favorite food? Why?
My favorite food is beef liver with onions. I don’t know why.

How do you relax after a hard day of work?
After work I enjoy the company of friends, and alternatively reading or drawing.

What do you hope to see accomplished scientifically in the next 50 years?
Realistically, in the next 50 years I would like to see consensus on the origin of dark matter. Moreover, it would be great to have a quality evaluation paradigm for scientists that wouldn’t actually harm science.

Giovanni is a postdoc in the SU Astronomy Department who joined the OKC in the fall of 2017.
Thanks Giovanni!

Extreme-Gravity Stars

The lives of massive stars are characterized by companionship: these stars are almost always found in gravitationally bound pairs. As such massive binaries evolve further, their cores run out of nuclear fuel and the stars can explode as supernovae, leaving behind in their centers either a neutron star or a black hole. In most cases such an explosion would be fatal for the binary, and disrupt it. In some cases, however, the final phases of binary stellar evolution can produce two compact objects -either white dwarfs, neutron stars or black holes– in tight binary systems.

Compact objects in binary pairs are driven closer and closer together as their system loses energy through interactions and gravitational radiation. The resulting merger of these types of objects is thought to be responsible for some of the most energetic events in the Universe including Type Ia supernovae and short duration gamma ray bursts.

The Laser Interferometer Gravitational-wave Observatory (LIGO) has made it possible to observe the gravitational waves emitted during mergers of compact objects. Since the beginning of data collection with the advanced instrument the LIGO observatory has detected gravitational waves from three different mergers of black hole pairs. Each of these detections was surprising because they involved a population of black holes that had not been observed before : black holes with masses of a few tens of solar masses. Scientists are also anticipating that LIGO will detect merging neutron stars.

A photo of Stephan Rosswog
Stephan Rosswog, Oskar Klein Centre, Stockholm University

Compact binary systems are really a cornerstone of modern astrophysics. Once the merger of a neutron star binary is detected in gravitational waves and electromagnetically, this will tell us about General Relativity, give us hints on how and where such binary systems form and —maybe most surprisingly— it may answer questions about nuclear physics that cannot be answered otherwise. This is maybe the most fascinating part of this rich story. — Stephan Rosswog

Connecting the sources of gravitational waves with phenomena that scientists are already familiar with, like supernovae and gamma ray bursts, requires that we observe the electromagnetic counterpart to the gravitational wave event. This is a challenging task with LIGO in its current state because the detector isn’t able to localize an event very precisely so follow-up searches with optical (and other wavelength) telescopes must search large areas of the sky for a new transient source.

A conference on The Physics of Extreme-Gravity Stars took place in Stockholm in June 2017.

Header image is from a simulation of two neutron stars merging, credit to Stephan Rosswog.