Sky and Telescope - November 2016 - 11

METEORITES I FRIPON: BLACK HOLES I Clouds Rain Down
A French network of all-sky sentinels
intends to speed up determination of
meteorites' trajectories and landing sites.
The innovative Fireball Recovery and
Interplanetary Observation Network
(FRIPON) is a collaboration between the
Observatory of Paris, National Center of
Scientiﬁc Research (CNRS), University of
Paris-South, French National Museum of
Natural History, and Aix-Marseille University. The network of 100 cameras and
25 radio receivers provides continuous
all-sky coverage over all of France.
Researchers estimate that 10 meteorites
fall in the country every year, but a meteor
sighting followed by a subsequent recovery
has been a once-a-decade aﬀair. With FRIPON, researchers will catch a meteorite's
fall from various angles and from known
coordinates, enabling them to quickly
and accurately determine the location of a
possible strewnﬁeld for an organized search
campaign. The goal is to accomplish a
ground recovery within 24 hours, before
space rocks become heavily contaminated.
An accurate trajectory might also help
reveal the object's source.
Researchers hope to expand FRIPON
into other European countries. Other networks include those in the UK and Spain,
and NASA researchers maintain two in
the United States. Read more about FRIPON at https://is.gd/fripon.
■ DAVID DICKINSON

Astronomers have detected three cold
gas clumps falling toward a galaxy's center - at odds with the prevailing idea for
how black holes get their food.
Scientists have long assumed that a
galaxy's central black hole eats from a
steady-stream buﬀet of hot gas impinging
on it from all sides. But there's growing
reason to think this notion is wrong.
Instead, the hot gas a galaxy sits in should
- under the right conditions - cool and
form clumps, which then rain down into
the galactic center and feed the black
hole. The diﬀerence matters, because it
might dramatically change the eﬀect a
black hole has on its galaxy.
Last March, astronomers conﬁrmed
that the threshold conditions for this
clumping and raining exists in a range
of galaxy clusters. Now, Grant Tremblay
(Yale) and colleagues report the ﬁrst
detection of cold clouds falling toward
the central black hole in the brightest
big elliptical of the cluster Abell 2597. As
detailed in the June 9th Nature, the team
didn't detect the clouds directly; rather,
they show up in ALMA data as "shadows,"
places where cold gas soaked up the light
from the hole's brilliant jet. Each clump

■ CAMILLE M. CARLISLE

This artist's concept depicts clouds of cold
molecular gas condensing around the brightest
galaxy in the cluster Abell 2597. The clouds
condense out of the hot, ionized gas that suffuses the cluster. New ALMA data reveal three
such clouds raining in on the galaxy, plunging
toward the central supermassive black hole.

SCOPES I Spy Dish Restored for Education
Students at the Pisgah Astronomical
Research Institute (PARI) now have a
new radio telescope to use for exploring
the cosmos. The North Carolina facility
began in 1962 as a NASA satellite tracking station and then was handed over
to the Department of Defense, which
installed a 12-meter-wide radio antenna
to collect classiﬁed data during the Cold
War. For 15 years, the big dish operated
mysteriously under a large dome.
PARI took possession of the site in
1999 and has since transformed the

is probably tens of light-years across.
Although the observations don't reveal
whether the clouds are orbiting the black
hole or just plunging toward it, the team
can tell that they are falling in at about
300 km/s (670,000 mph) and that they're
within 300 light-years of the black hole.
These results are "entirely inconsistent" with the longstanding hot-accretion
scenario for black hole growth, Tremblay
explains. "If these 'rainstorms' exist in
more galaxies, we may need to seriously
rethink how we model black hole accretion," he says.

NRAO / AUI / NSF, DANA BERRY / SKYWORKS

A New All-Sky Network

sprawling complex into an education
center (S&T: Sept. 2013, p. 36). The
staﬀ found the 12-m antenna dead - a
lightning strike had destroyed its control
processor. Needing new motors and
drives, the big dish languished until
2012, when funding became available for
renovations.
With the help of various contributors
and volunteers, including students, PARI
staﬀ removed the aging dome, installed
new hardware, cleaned the entire instrument, and created software to allow users

to operate the telescope remotely. Now
fully operational after lying dormant for
25 years, the restored telescope captures
photons emanating from hydrogen atoms
at a frequency of 1420 megahertz (21 cm
in wavelength).
This summer, Duke University
students used the telescope as a one-of-akind teaching tool. Then, in the fall, PARI
plans to make the instrument available
to students around the world to remotely
examine star formation, stellar nurseries,
and the motion of stars with respect to
Earth, among other projects.
■ ANA V. ACEVES

Sk yandTelescope.com November 2016

https://is.gd/fripon http://www.SkyandTelescope.com

Sky and Telescope - November 2016

Table of Contents for the Digital Edition of Sky and Telescope - November 2016