News • Views
The white
dwarf that acts
like a pulsar
Periodic high-energy X-ray pulses
have been picked up from a white
dwarf – behaviour typical of a
pulsar and not at all what was
expected from these supposedly
dying stars.
Although both white dwarfs and pulsars are compact objects formed from
stars, they had been thought very different. White dwarfs have run out of
fuel and so just cool down and fade
away; the even denser neutron stars
that form pulsars emit beams of radio
and X-ray emission as they spin.
Yukikatsu Terada of the Institute
of Physical and Chemical Research
(RIKEN) in Wako, Japan, led the
team that found the strange white
dwarf, called AE Aquarii, part of
a binary pair. The team were using
Suzaku, the joint JAXA/NASA X‑ray
observatory, to investigate possible
source mechanisms for cosmic rays.
They wondered if white dwarfs such
as this one, rapidly spinning and with
powerful magnetic fields, could be a
sufficiently energetic source. The
team found the expected glow of soft
X-rays from gas falling from the companion star onto the white dwarf, but
they also found intermittent bursts of
harder X-rays. These had a period of
33 seconds, matching the rotation of
the white dwarf.
Because pulsars emit cosmic rays
by a mechanism thought to involve
charged particles trapped in and interacting with the powerful magnetic
fields, a similar mechanism in white
dwarfs may make them widespread
sources of low-energy cosmic rays.
http://www.isas.jaxa.jp/e
Letters
Bernard Pagel
and me
From Jeremy Tatum
I read with interest the obituary of
Bernard Pagel (Edmunds 2007). I
worked only briefly as a student at
Herstmonceux under the guidance
of Dr Pagel several decades ago, but
I still remember his great encouragement and help. However, Dr Pagel
was not the only astronomer to
recall the tripartite division of Gaul.
In the course of a paper on microwave spectroscopy in the Astrophysical Journal (Tatum 1986) I wrote
that: “Figure 5, like Gaul, est omnis
divisa in partes tres.” In my original
manuscript I had followed this with
the reference in the usual style (Caesar 45 BC) and had included it in the
1.6
UKIRT Infrared Deep Sky Survey goes global
The first section of a major infrared
sky survey has gone on worldwide
release, as part of UKIDSS.
This part of the UKIRT Infrared
Deep Sky Survey has been available
to European Southern Observatory
members for 18 months now, but the
worldwide release will bring this valuable dataset into the wider research
world. And it is just the beginning:
UKIRT has already mapped a larger
volume of the sky than any previous infrared survey, and it has now
mapped 15 times as much as is covered by this release. New releases
every six months should continue to
deliver the sort of new objects and
landscapes that have already come
out of the project, including the
coolest brown dwarf in the galaxy,
and a quasar with a redshift of more
than 6, i.e. 12.7 billion years old.
http://outreach.jach.hawaii.edu/
room/2008_ukidss_dr1/
Left: a visual light image of IRAS 20376, about 5500 light-years from Earth in
the constellation Cygnus, taken by the Second Digital Sky Survey in the 1980s.
Right: the same area in the infrared showing the presence and structure of an
H ii star-forming region. This will be part of a future UKIDSS release. (UKIDSS)
Tracking dust back to supernova explosions
Dust particles in a supernova
remnant have been tracked to the
supernova itself – an important
step in understanding the formation of planets.
Supernova remnant Cas A is known
to be dusty, but where does the dust
come from? A team led by Jeonghee
Rho from NASA’s Spitzer Science
Center used the Spitzer Space Telescope to find out and analyse the dust.
They found it in the same places as
the supernova gas, unambiguously
formed in the same explosion (published in the Astrophysical Journal).
There was a lot of dust, around
10 000 times the mass of the Earth,
easily enough for Spitzer’s sensitive
reference list at the end of that paper
as I do in this. The quotation did
appear in the published paper, but
much to my regret (and annoyance)
the reference did not.
In my case, the quotation did
not indicate my great erudition
and breadth of scholarship – quite
the opposite, in fact! The words
are from the very first sentence
of De Bello Gallico, and I never
got beyond that first sentence. I
never succeeded in passing Latin at
O-level, and consequently (unlike
Bernard Pagel) I missed any opportunity of going to Cambridge.
Jeremy B Tatum, University of Victoria.
References
Caesar J 45 BC De Bello Gallico (Rome).
Edmunds M 2007 A&G 48 6.37.
Tatum J B 1986 Astrophysical Journal
Supplement 60 433–474.
Spitzer’s false-colour view of Cas A,
with silicon gas in blue, argon in
green and red marking dust.
infrared detectors to detect protosilicates, silicon dioxide, iron oxides,
pyroxene, carbon, aluminium oxide
New light on
Stonyhurst discs
From Kevin Kilburn, Fintan O’Reilly
We have had an excellent response
regarding the missing set of original
Stonyhurst discs (A&G 48 6.6) and
we would especially like to thank
Peter Hingley for facilitating email
communication with Prof. Jack
Meadows and Dr Richard Jameson.
In the mid-1960s the original discs,
with solar drawings and other
19th-century science material, were
acquired for the Astronomy Department at the University of Leicester.
The solar drawings and perhaps also
the discs were subsequently sent to
the Royal Greenwich Observatory.
Around 1990 the RGO archive
of Stonyhurst solar drawings
and other compounds.
But even Spitzer could not detect it
all, according to Haley Gomez, of the
University of Cardiff, one of the team
working on Cas A. That will take a
new observatory – the European Herschel Space Telescope.
“At the moment we’re missing
something,” says Gomez. “The dust
Spitzer is looking at is quite warm,
about 100 K. We think there’s colder
dust in there, which Spitzer doesn’t
see – at around 20 K. We’re hoping
that Herschel will allow us to see the
colder dust. Herschel could completely change the way we see the
universe.”
http://www.cardiff.ac.uk
was transferred to the University
Library, Cambridge. We thank
Adam Perkins, Curator of Scientific
Manuscripts, for this information
and also for providing a list of the
solar drawings made at Stonyhurst
1880–1947. Most are still packaged
and unopened at the University
Library and it may be that the
original Stonyhurst discs are with
this archive. The drawings are on
heavy-duty paper, 40 × 40 cm square.
We have now also discovered that
the original Stonyhurst discs are on
glazed linen, not glass as previously
indicated, at a scale of 10 inches to
the solar diameter. Any further information would be most welcome.
Kevin J Kilburn, Secretary, Society for
the History of Astronomy, kkilburn@
globalnet.co.uk. Fintan O’Reilly, Curator,
Stonyhurst College Observatory.
A&G • February 2008 • Vol. 49