Office of Communications and Public Affairs
FOR IMMEDIATE RELEASE:
Contact: David Poratta, 212-854-6581 or dpopratta@columbia.edu
Shedding Light on Black Holes
Astrophysics Laboratory Scientist Aids in Refining Models of Black Hole Winds
New York N.Y. -- Columbia astronomer Daniel Wolf Savin, a specialist in laboratory
astrophysics, together with Andreas Wolf of the Max-Plank Institute for Nuclear Physics in
Heidelberg, Germany, and Alfred Mueller of the University of Giessen, Germany, have proven
that a standard theoretical model which supposedly explained the nature of collisions between
electrons and iron ions in the winds surrounding black holes, is “incorrect.”
“Our research,” says Savin, “helps answer the question of how matter can be expelled away from
a black hole rather than getting sucked down the gravitational drain of the black hole.” The
benefits of this discovery means being able to input, and thus update, the new data into current
theoretical models, leading to enhanced understandings of black hole winds.
Savin and his colleagues sought to shed light onto a puzzling aspect in the structure of outflowing winds near black holes. New satellite information revealed that the iron in these winds is
far less ionized than current theoretical modeling suggests. Nagai Netzer, a scientist with Tel
Aviv University, had suggested that the low “theoretical” electron-ion recombination rates (the
‘modeling’ approach) for iron are responsible for the differences between the actual observations
and models.
To test the idea, Savin and his collaborators used the heavy-ion Test Storage Ring (TSR) at the
Max Planck Institute for Nuclear Physics (MPI-K) in Heidelberg, Germany, to recreate in the lab
what happens in outer space with electron-ion collisions surrounding black holes. The results of
the experiment confirmed that published theoretical electron-ion recombination rates were
inaccurate.
In the experiment, the team took a negatively charged beam of iron ions, accelerated it, and then
directed it through a thin foil. This process stripped the ions of some of their electrons, creating
a beam of positively charged iron ions. The beam was then merged with a beam of electrons,
and the team measured how many iron ions captured an electron. The effect of this capture
process mimics the interactions occurring in black hole winds far off in the universe.
More
Laboratory astrophysics allows astronomers to read spectra from distant objects in the universe.
This little-known area of astrophysics is an interdisciplinary field combining physics, chemistry,
and astronomy. It involves research by physicists who reproduce experimentally or theoretically
the physical processes that create the observed cosmic spectra. By understanding these
fundamental processes, which can be thought of as the letters in the spectrum, astronomers are
able to spell out the words, piece together the sentences, and decipher the story hidden in each
celestial object.
***
Daniel Wolf Savin was recently elected as a Fellow to the prestigious American Physical
Society. The Society recognized Dr. Savin “for his many and wide ranging contributions to
atomic collision studies; their applications to astrophysics and for catalyzing numerous
astrophysically motivated research projects with other atomic, molecular, and optical scientists.”
No more than one half of one percent of the Society’s membership is elected as a Fellow in any
given year.
***
About Columbia University: A leading academic and research university, Columbia
continually seeks to advance the frontiers of knowledge and to foster a campus community
deeply engaged in understanding and addressing the complex global issues of our time.
Columbia's extensive public service initiatives, cultural collaborations and community
partnerships help define the University’s underlying values and mission to educate students to be
both leading scholars and informed, engaged citizens. Founded in 1754 as King’s College,
Columbia University in the City of New York is the country’s fifth oldest institution of higher
learning.
For more on Astronomy at Columbia: "http://www.astro.columbia.edu/"
###
2