The Integral, Fermi and Swift space observatories have used the
magnifying power of a cosmic lens to explore the inner regions of a
supermassive black hole.
Gamma rays are highly energetic radiation emitted by some of the most
extreme objects in our Universe. Jets of gamma rays moving at close to
the speed of light stream from the areas around black holes, for
example. These jets are thought to be emitted by superheated material
spinning wildly as it is devoured by the hungry black hole.
Our telescopes will never be powerful enough to reveal these inner
regions, and scientists struggle to examine exactly how these jets are
unleashed into the Universe.
“Because we can’t clearly see what’s going on, we don’t fully understand
this behaviour,” says Andrii Neronov of the University of Geneva,
Switzerland, lead author on the Nature Physics paper published online today.
“However, our method allowed us to ‘resolve’ this region, and get an
insight into the patch of space directly surrounding a supermassive
black hole known as PKS 1830-211.”
This black hole lies many billions of light-years away. Neither ESA’s
Integral satellite nor NASA’s Fermi gamma-ray telescope can observe the
region unaided, but a lucky coincidence provides a helping hand:
gravitational microlensing.
“From Earth, black holes are tiny. They’re just so very far away,” notes
Dr Neronov. “Trying to observe PKS 1830-211 is like trying to look at
an ant sitting on the Moon.
“None of our telescopes can observe something so small, so we used a trick to resolve the ant: a huge gravitational lens.”
Massive cosmic objects, from single stars to galaxy clusters, bend and
focus the light that flows around them with their gravity, acting like
giant magnifying glasses.
Dr Neronov and colleagues used a star sitting between their target and
Earth to ‘zoom in’ to the black hole and measure the size of the
jet-emitting region – the first time this method has ever been used with
gamma rays.
They picked out structures on the same angular scale as that of the Moon
ant. The observed patch of sky covers a region about 100 times the
Earth–Sun distance. In astronomical terms, this is remarkably small.
“Our observations demonstrate that the gamma rays come from the direct
vicinity of the black hole itself,” says Dr Neronov. “This gives us some
idea about what is and isn’t important in generating the jets.
“It’s amazing to be able to see such tiny things at such enormous
distances from us. I’m very excited to have a ‘black-hole-scope’ to
investigate the inner regions of the jets.”
Observing the gamma-ray source with ESA’s Integral and NASA’s Fermi and
Swift allowed the astronomers to build up a more complete picture of the
radiation streaming out.
The more energetic gamma rays, detected by Fermi, are seen to be coming
from the tiny base of the jet – the ‘ant on the Moon’-size region –
while the lower energy gamma rays, detected by Integral, were emitted
from a much larger surrounding region.
The team also studied X-rays using Integral and Swift. They found these
X-rays to be emanating from a region stretching around the hole some 400
billion km or more.
“This black hole is one of the most powerful known objects of its kind.
Fully characterising its emission will hopefully give us real insight
into how these jets form,” says Erik Kuulkers, ESA’s Integral project
scientist.
“Fortunately, the black hole lies in the field of space located towards the centre of our Galaxy, so Integral sees it often.
“These observations provide unique information about the high-energy
processes taking place around supermassive black holes, by allowing us
to ‘look inside’ tiny structures lying very far away from us.”
Notes for Editors
The results described here are reported in “Central engine of a gamma-ray blazar resolved through the “magnifying glass” of gravitational microlensing,” by A. Neronov, I. Vovk and D. Malyshev, published online in Nature Physics on 6 July.
For further information, please contact:
ESA Science and Robotic Exploration Communication Officer
Tel: +31 71 565 6799
Mob: +31 61 594 3 954
Email: markus.bauer@esa.int
Andrii Neronov
ISDC, Astronomy Department
University of Geneva
Switzerland
Tel: +41 22 379 2120
Email: Andrii.Neronov@unige.ch
Erik Kuulkers
Integral Project Scientist
Directorate of Science and Robotic Exploration
European Space Agency
Tel: +34 918 131 358
Mob: +34 699 439 987
Email: erik.Kuulkers@sciops.esa.int
Source: ESA
