Download Comet ISON keeps observers guessing

News
Editorial
Zoo goes zoom
Sue Bowler,
Editor
The
Zooniverse
is expanding.
Citizen
science,
research
projects that
harness the eyes and intellects
of armies of volunteers, is going
from strength to strength. The
results speak for themselves. In
this issue, Karen Masters and
Chris Lintott report on an RAS
Specialist Discussion Meeting
on galaxy morphology, using the
work of Galaxy Zoo volunteers.
Galaxy Zoo members also chose
the image we’ve used on the
cover of this issue, for which I’m
most grateful!
More and more research
fields in astronomy have more
data than ever before, thanks
to large surveys and the careful
curation of legacy information;
disciplines in geophysics are also
using the method, for example in
monitoring volcanoes. Whatever
the science, the challenge
of handling large datasets is
not going to go away, so the
Zooniverse and its army of
volunteers is making a significant
difference.
The benefits to researchers are
clear, but what about that army
of volunteers? Why do people
choose to spend their free time
poring over scientific images?
The volunteers themselves say
that they enjoy it, they like to
learn and that they get a lot of
satisfaction from contributing to
research. They find things, too.
Hanny’s Voorwerp, a glowing
green object spotted by Galaxy
Zoo volunteer Hanny Van Arkel,
proved to be a new type of gas
cloud, for example.
In other words, there are quite
a lot of people who don’t just
enjoy finding out about research,
they want to be part of it, too.
In the Zooniverse, they are part
of it. This is not only a fabulous
resource for research, but it is
also a boost to our sciences. A
lot of people out there support
astronomy and geophysics
strongly enough to do something
for it. That’s a lot of impact and
long may it continue to expand.
[email protected]
5.4
Comet ISON keeps observers guessing
Speculation about whether or not
comet C2012 S1 ISON will live up
to its “comet of the century” billing
has continued as it became visible
again in August. Early observations
including the first image, taken by
amateur observer Bruce Gary of
Arizona, suggested that it had not
brightened as much as anticipated
in early light curves.
Comets are notoriously variable in
how they behave, especially compared to predictions of their behaviour; comet Kohoutek (C/1969 O1)
in 1969 is in the mind of many comet
observers, since it was widely talked
up as a comet of the century but
proved to be less than spectacular.
Comet ISON has been suggested as
a naked-eye object for late November, but it may not survive its closest
approach to the Sun on 28 November.
Comet ISON was observed by
NASA’s Swift satellite in January 2013 and by the Hubble Space
Telescope in April, revealing some
activity consistent with release of
volatiles such as carbon dioxide.
The Spitzer Space Observatory captured a 3.6 µm image in July that
showed a plume of dust behind the
comet as it approached the Sun, as
well as strong carbon dioxide emission. Observers hope that the com-
A Hubble Space Telescope
composite image of Comet ISON
taken in April 2013 with the Wide
Field Camera 3. (NASA, ESA, Hubble
Heritage Team [STScI/AURA])
et’s activity will increase as it passes
Mars at the start of October, when
temperatures should increase enough
to start water-ice activity. NASA has
a coordinated observing campaign to
track the comet.
As it passes Mars at a distance of
0.07 au, Mars Science Laboratory
researchers will observe it with the
HiRISE camera, designed for mapping the surface of Mars. While the
camera is not ideal for imaging comets, because it has a limited maximum exposure time, it should be
able to detect ISON at a time when
it has crossed the solar system’s frost
line and warmed up enough to start
vaporizing frozen water. The measurements from Mars could help to
refine estimates of the size of ISON’s
nucleus, which may in turn help to
predict whether or not it will survive
perihelion.
Comet ISON was discovered on 21
September 2012 by Vitali Nevski and
Artyom Novichonok at the International Scientific Optical Network
(ISON) telescope near Kislovodsk,
Russia. It is believed to be inbound
on its first passage from the distant
Oort Cloud, on a parabolic orbit that
will take it less than 2 million km
from the Sun at its closest point – a
sungrazing comet. Debate continues
over whether comet ISON will survive perihelion. Observers will just
have to wait and see.
http://www.isoncampaign.org
Are we martians, chemically speaking?
Early in the history of the solar
system, Earth was a much less
hospitable planet than Mars; the
idea that life on Earth originated
on Mars has received a boost from
chemical evidence that a form of
the element molybdenum that
may have been essential for life
to develop existed on Mars at the
time – and not on Earth.
Prof. Steven Benner from the Westheimer Institute for Science and
Technology in Florida, speaking at
the annual Goldschmidt Conference in Florence, set out two problems with the idea of life forming on
Earth. The first is the tar problem:
if you add energy such as heat or
light to organic molecules and leave
them alone, they don’t create life, but
rather turn into something more like
tar. Elements such as boron – found
in martian meteorites – and molybdenum can stop tar forming and bring
about the reactions needed for life.
The second problem Benner iden-
tified was that the early Earth was
covered with water, making it difficult for elements such as boron or
molybdenum to build up into useful
concentrations.
Benner suggested this is further evidence for life originating in the warm
wet conditions on the young Mars,
and reaching Earth via meteorites.
Climate change on Mars made it
less hospitable to life, whereas Earth
became more habitable.
http://bit.ly/14kQAPD
Looking ahead to the future of the Sun
A star very like the Sun – but 4 billion years older – is giving astronomers a glimpse of how our star
will age. This “solar twin” also
suggests a link between stellar
age and lithium content.
An international team led by astronomers in Brazil has used ESO’s Very
Large Telescope to establish that star
HIP 102152, 250 light-years away
and 8.2 billion years old, is chemically very similar to the Sun. The
team also found another star very
like the Sun but younger: 18 Scorpii,
which is 2.9 billion years old compared to our Sun’s 4.6 billion years.
Solar twins are rare; HIP 102152 is
the oldest found.
A key measurement for these stars
is the lithium content. Lithium
formed in the later stages of the
Big Bang, along with hydrogen and
helium. The Sun has very little lithium, just 1% of the primordial proportion. Researchers have wondered
how typical the Sun is as a star, given
this unusually low lithium content.
HIP 102152 also has very low lithium levels, lower than the Sun, while
18 Scorpii and other younger solar
twins have higher proportions. The
correlation between age and lithium
content suggests that stars somehow
destroy lithium as they age.
A final twist in the story is that
HIP 102152 has an unusual chemical composition pattern that is subtly
different to most other solar twins,
but similar to the Sun. They both
show a deficiency of the elements
that are abundant in meteorites and
on Earth. This is a strong hint that
HIP 102152 may host terrestrial
rocky planets.
This research was published in
Astrophysical Journal Letters by
TalaWanda Monroe et al.
http://www.eso.org/public/news/eso1337
A&G • October 2013 • Vol. 54