My area of research is comets and asteroids, which I have been studying
since 1994. I am interested in the composition and physical properties
of these objects, and how they compare to each other and other objects
in the Solar System. Why? Because Small Bodies can tell us about
the origin of the Solar System -- what were the
compositional and thermophysical conditions in the solar
nebula and in the protoplanetary disk? Understanding
the origin of the Solar System is the
overall "big picture"
question that I (and many planetary scientists) work toward.
However to understand what the small bodies tell us about
our origins, we need to know what has happened to these objects
in the intervening 4.6 billion years sinice they formed.
In other words, I study cometary and asteroidal evolution.
This is not an easy task, but it is an interesting question
in its own right, and it is critical if we are to make sense
of what the Solar System is like today.
The experimental methods that I use almost always involve
telescopes, both on the ground and in space. I primarily
work at visible and infrared wavelengths, but have also
done radio experiments as well.
You can get a sense for some of the projects I'm working on
by checking out various paper databases:
my ORCID entry,
my ADS entry, and
my Google Scholar entry. But below I have some descriptions
of some of my projects.
Fun with specific objects:
- Behavior and nucleus properties
of comet 2P/Encke.
- Comet Encke is an unusual comet with a very short
orbital period. We have been working to understand the
nucleus's size (with infrared observations) and spin state
(with visible observations). We would also like to figure out
its shape since its diurnal light curve is very odd, having
only one bright peak (instead of two). Furthermore, we are studying
the comet's activity behavior when it is near aphelion. The
comet seems to be intrinsically brighter at 4 AU than it is
at say 2 or 3 AU, even though one would expect a comet to become
less active the farther it is from the Sun. Check out some of the P/Encke projects I've worked on.
- Behavior of
comet 29P/Schwassmann-Wachmann 1.
- Comet 29P is in a near-circular orbit just
outside Jupiter's orbit. It has a long history of having
outburst behavior, where its normal constant level of
activity will be punctuated with brightenings of a few
magnitudes. We are studying the evolution and devlopment
of the comet's coma before, during, and after these outbursts.
By watching how the morphology of the coma changes over time,
we hope to determine the comet's spin state and active areas.
We also are interested in understanding the nucleus's size
and shape. Check out some of the 29P projects I've worked on.
Fun with surveys:
Ensemble properties of cometary nuclei.
- This is a catchall project for lots of work I'm doing on
understanding the size distribution, albedo
distribution, and variety of thermal properties among
cometary nuclei. These are all important properties
for understanding how the evolutionary processes
that comets suffer actually affect their bulk properties.
The size and shape distributions give clues about the collisional
and fragmentation history of the bodies.
The albedo distribution tests just how robust the
classic "4%" assumption really is, plus will help us understand
how cometary activity changes a surface as a comet migrates
from more distant orbits to the inner Solar System.
The thermal properties tell us about the structure of the
nucleus, at least near the surface, which is again
part of the evolutionary story. So there
are lots of issues of evolution to be teased out here.
I'm a Co-I on the NEO Surveyor
mission, which hopefully launches in 2026, and will
provide IR measurements of thousands of comets. In the meantime,
I'm on other surveys using other telescope facilities; an
example of some of the work is here and here. Furthermore, I'm
involved with the NEOWISE
mission, which is continuing to detect gas, dust, and nuclei from
many comets year after year.
Activity of distant comets and Centaurs.
- Comet 29P counts as an active Centaur,
in addition to being a short-period comet. Centaurs
are usually defined as objects that orbit among the giant planets,
or more specifically have perihelia outside Jupiter's orbit, but
semimajor axes smaller than Neptune's.
are also active, in fact there are over
active Centaurs known,
and we're interested in understanding
the general phenomenon. Why are some Centaurs active
and others not? What does activity do to their surfaces?
Is the nature of the activity different compared to
normal inner-Solar System cometary activity? These questions
are important for understanding the evolution of
icy bodies as they dynamically migrate from the Scattered
Disk, through the giant planet region, and into the
inner Solar System. One very exciting part of
this project is that we will have JWST data
coming soon in 2022 and 2023 on several active Centaurs.
But we also have lots of ground-based visible data on many Centaurs
and on several short-period comets that are just slightly outside
the Centaur definition (and so tend to get overlooked).
Surface properties of near-Earth asteroids.
- We're studying not only NEAs that might
be dead comets but NEAs in general. For example, what
happens to NEAs that are in orbits that take them very
close to the Sun? If they are heated to high temperatures
(~600K to 1400 K) many times, what chemistry happens on
their surfaces? Do they evolve differently than NEAs
that stay cooler?
Currently the entire comet group here at UCF is relatively small:
However I collaborate with others here at UCF
and with many folks around the U.S. and Europe.
If you are an undergraduate or graduate student looking
to go into astronomy, and if comets and asteroids interest you, feel
free to contact me about coming to UCF.
updated august 2023
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