by Nancy A. Levenson (with Rodrigo Carrasco)
Science Highlights
During the first half of 2012, Gemini users published a diverse collection of results.
Here are several highlights:
A Comet or an Impact in the Main Asteroid Belt?
A handful of comets orbit with the main asteroid belt. One peculiar object, P/2010 A2 (LINEAR),
discovered in 2010, has a cometary appearance (with a tail), and also an asteroid-like body. Is
P/2010 (A2) LINEAR a genuine sublimating comet, or is another process responsible for the
tail? Olivier Hainaut (European Southern Observatory) and colleagues used observations from
Gemini North with the Gemini Multi-Object Spectrograph (GMOS), along with several other
telescopes, to investigate this question.
The comet’s appearance in early
2010 was striking (Figure 1). Dust
does not immediately surround
the small nucleus, and the much
larger tail is detached. The tail is not
uniform, but rather shows several
crossing arcs close to the nucleus.
Figure 1.
The GMOS-North r’
image of P/2010 A2
(LINEAR) obtained on
February 19, 2010,
shows the small nucleus
separated from the
nearby dust tail.
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After first considering the survival of
water ice and other volatiles at this
location close to the Sun, the team
concluded that water would not persist longer than a few times 106 years, even with a cometlike nuclear composition. Thus, cometary activity (sublimation) is not responsible for expelling
dust from the surface to produce the observed tail. More detailed models of dust emission
(Figure 2) include the effects of grain size and time since emission to describe the resulting
extended tail. They determined that all cometary activity stopped at least several weeks before
the observations, and propose a single burst of dust ejection about a year earlier as the best
model. Also, relatively large dust particles produced the X-shaped arcs.
GeminiFocus
June2012