Researcher Presents Evidence of Dark Matter in the Milky Way
Hello reader!
It follows an article published today (03/04) in the english
website of the Agência FAPESP noting that researcher presents evidence of dark matter in the Milky Way.
Duda Falcão
NEWS
Researcher Presents Evidence of
Dark Matter in the Milky
Way
By José Tadeu Arantes
March 04, 2015
(Photo: A. Fujii/NASA)
A study
published in Nature Physics compares the
gravitational profile of the galaxy’s
central portion to the profile
it would have if it consisted entirely of
luminous matter.
|
Agência FAPESP – Robust proof of the existence of
dark matter in the region between the solar system and the center of the Milky
Way has been obtained by Fabio Iocco, a researcher affiliated with São Paulo
State University’s Theoretical Physics Institute (IFT-UNESP) and the ICTP South
American Institute for Fundamental Research (ICTP-SAIFR) in Brazil. A paper
reporting the study, “Evidence for dark matter in the inner Milky
Way” by Iocco et al., was published online by Nature Physics on
February 9.
“We obtained this evidence by measuring the rotation
of our galaxy with great precision,” Iocco told Agência FAPESP. “We
then used the rotation data to calculate the galaxy’s gravitational attraction,
and from the gravitational attraction, we arrived at its mass. Its calculated
mass is greater than that of its luminous matter (stars and gas) alone. The
difference points to the existence of another material component in the region,
and this has to be dark matter.”
Iocco is Italian and is working in Brazil supported by a scholarship and research grant from
FAPESP’s Young Investigators Grants program.
The hypothesis that the universe contains an unknown
form of matter, called dark matter because it has never been detected via
direct astronomical observation, was formulated in the 1970s, when scientists
were first able to produce very precise calculations of the rotation of gas
around the center of a spiral galaxy.
This rotation is difficult to measure in the Milky Way
because all human observers are located inside the galaxy, roughly halfway
between its periphery and its center.
“Measuring gas and star rotation with the necessary
precision has been a major challenge for all these years because of our
position in the galaxy,” Iocco said. “It’s particularly difficult in the region
between the Sun and the center of the Milky Way, where there’s a high concentration
of stars and gas, thus contributing more to the amount of mass.”
“We had to compile two enormous datasets. We needed
indicators of total gravitational potential and rotation curves, including
variations in the velocities of stars, gas and masers [sources of electromagnetic emission]. For this purpose,
we compiled all the data recorded in the literature since the 1960s. We also
needed the distribution of visible matter. In this case, because of the lack of
consensus in the literature regarding the morphological structure of the
galaxy, we collected data on all the existing models instead of running the
risk of choosing the wrong model.”
According to Iocco, neither these datasets nor the
distribution of visible matter are compatible with the calculated galactic
rotation curve. “This is one of the reasons why we’re so sure of having proved
the existence of dark matter in the region, including the Solar System,” he
said.
There has been a great deal of speculation about the
composition of dark matter. Iocco preferred not to express an opinion.
“We didn’t set out to answer that question in the
paper,” he said. “Indeed, we didn’t assume the existence of any kind of dark
matter. The evidence for it emerged from our calculations. There must be some
kind of matter, something that exerts gravitational attraction, and it must be
dark, non-baryonic, and non-compact. The findings of our forthcoming studies
using the same data should provide more precise answers to questions about the
distribution of this dark matter, which could help to determine the nature of
this material component, be it through direct or indirect detection.”
Fabio Iocco was born in Naples and graduated from the
University of Naples Federico II, where he also earned a PhD. While working on
his doctorate, he spent three years at Stanford University, California, as a
visiting researcher. Once back in Europe, he worked at the Arcetri Observatory
in Florence, Italy, and later in Paris, Stockholm and Madrid, before coming to
São Paulo.
The paper “Evidence for dark matter in the
inner Milky Way” (doi: 10.1038/nphys3237), by Iocco et al., can be
read on the Nature Physics website
at www.nature.com/nphys/journal/vaop/ncurrent/full/nphys3237.html.
Source: English WebSite of the Agência FAPESP
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