NRAO/Socorro Colloquium Series
Michal Drahus
Caltech
Catastrophic Disruptions of Comets
Spontaneous disruption of cometary nuclei is one
of the least understood, but most important aspects of their nature. Attempts
to explain the mysterious phenomenon date back to 1846, when in the middle of
January astronomers were surprised to see periodic comet Biela had split into
two pieces. In the course of time many similar events were discovered and the breakup
rate estimated to be close to one per century per comet. Breakups are often
accompanied by massive outbursts of brightness, but it is not even clear if it
is the outburst that triggers splitting or the other way around. The fate of
split comets is frequently the same: their fragments continue to break up and
quickly disappear. For example, the two pieces of comet Biela were recovered
during the next return in 1852, but have never been seen again. Instead,
intense meteor showers were observed during the comet's next expected returns.
In spite of this long history and great importance for the determination of cometary
lifetimes, the phenomenon remains unexplained to date, although several
hypotheses have been proposed. For example, it has been speculated that the
disruption can be caused by nucleus spin-up powered by outgassing torques,
which can drive the nucleus spin rate beyond the limit of rotational stability.
I will discuss the progress in testing this hypothesis that has happened in the
last decade, and overview possible future studies aimed at solving this longest-standing
problem in cometary science.
March 21, 2014
11:00 am
Array Operations Center Auditorium
All NRAO employees are invited to attend via video, available in Charlottesville 245, Green Bank Auditorium, Tucson N525, and NTC 400.
Local Host: Miller Goss
