Astronomers use IAC instrument to probe the origins of cosmic rays

Astronomers use IAC instrument to probe the origins of cosmic rays

Left. Composite image of the remnant of Tycho Brahe’s
supernova (1572) using data from the Chandra x-ray satellite
observatory (yellow, green, blue (credits NASA/SAO), from the
Spitzer infrared satellite observatory (red, credits,
NASA/JPL-Caltech), and from the Calar Alto observatory (stars
whtie, credit, Krause et al.). The transparent magenta box
shows the field of the ACAM instrument at the Cassegrain focus
of the William Herschel Telescope (WHT, ORM, La Palma). Centre,
a zoom-in on the ACAM field with a green box showing the size
of the field of the 2d spectrograph GHaFaS (WHT, ORM).Right.
The reduced and integrated image of GHaFaS in the emission from
ionized hydrogen (Ha). Credit: NASA/SAO, NASA/JPL-Caltech

In November 1572 a supernova explosion was observed in the
direction of the constellation of Cassiopeia, and its most
famous observer was Tycho Brahe, one of the founders of
modern observational astronomy. The explosion produced an
expanding cloud of superhot gas, a supernova remnant which
was rediscovered in 1952 by British radioastronomers,
confirmed by visible photographs from Mount Palomar
observatory, California, in the 1960’s, and a spectacular
image was taken in X-rays by the Chandra satellite
observatory in 2002. Astronomers use supernova remnants to
explore high energy physics in interstellar space.

In an article to be published in the Astrophysical
a team from 7 countries, including researchers at
the Instituto de Astrofísica de Canarias (IAC), has observed
the Tycho remnant with GHaFaS, a
sophisticated instrument from the IAC, mounted on the 4.2m
William Herschel Telescope (WHT) at the Roque de los Muchachos
Observatory (Garafía, La Palma, Canary Islands). Their aim was
to explore the hypothesis that the , high energy sub-atomic particles
which continually bombard the Earth’s , originate in these highly
energetic gas clouds. GHaFaS allows astronomers to observe the
emission from ionized hydrogen across wide fields, giving a map
of the velocity structure within an object in fine detail.

They mapped a sizeable portion of the Tycho remnant cloud,
including a prominent bright filament, and showed that the
hydrogen line emitted from the filament shows a much bigger
spread of velocities than can be explained from the temperature
of the gas. In fact they measured two components of emission,
one with a large velocity spread, and another with an even
larger spread. They showed that the only way for the emission
to show these characteristics is if there is a mechanical
mechanism in the cloud producing particles. Supernova remnants have
long been considered a probable source of the cosmic rays which
pour onto the outer atmosphere of the Earth, but this is the
first time that clear evidence for an acceleration mechanism
has been produced. Cosmic rays have energies much higher than
those produced in even the biggest particle accelerators on
Earth (such as CERN), and their study is important not only for
astrophysics but for particle physics.

“These results could not have been produced by any of the other
spectrographs on major telescopes in the world” says Joan Font,
one of the authors of the article, and the person responsible
for the operations of GHaFaS. “Our instrument has a unique
combination of high velocity resolution, wide field, and good
angular resolution, and this combination was required for the
Tycho project”. These observations are a first step towards a
fuller understanding of the cosmic ray acceleration mechanism
in . “We should be
able to combine these results with observations already taken
using the OSIRIS narrow band imager on the 10.4m Gran
Telescopio CANARIAS (GTC) to determine the efficiency of
acceleration of the cosmic rays” says John Beckman, another IAC
researcher and a co-author on the paper.

Explore further:
explanation for the galaxy’s cosmic radiation

More information: Sladjana Knežević et al, Balmer
Filaments in Tycho’s Supernova Remnant: An Interplay between
Cosmic-ray and Broad-neutral Precursors, The Astrophysical
(2017). DOI: 10.3847/1538-4357/aa8323

Journal reference: Astrophysical

Provided by: Instituto de Astrofísica de Canarias