UBC Assoc. Prof. Brett Gladman is one of an international
team of astronomers who have discovered three previously unknown
moons of Neptune using an innovative technique.
These moons are the first to be discovered orbiting the gas
giant since the Voyager II flyby in 1989, and the first discovered
from a ground-based telescope since 1949. The find boosts
the number of known satellites of Neptune to 11.
The new satellites were a challenge to detect because they
are only about 30-40 kms (18-24 miles) in size. Their small
size and distance from the Sun prevent the satellites from
shining any brighter than 25th magnitude, about 100 million
times fainter than can be seen with the unaided eye.
To locate the new moons, the team, lead by Matthew Holman
of the Harvard Smithsonian Center for Astrophysics and J.J.
Kavelaars of the National Research Council of Canada, utilized
an innovative technique. Using the 4.0-meter Blanco telescope
at the Cerro Tololo Inter-American Observatory, Chile, and
the 3.6-meter Canada-France-Hawaii Telescope, Hawaii, they
took multiple exposures of the sky surrounding Neptune.
After digitally tracking the motion of the planet as it moved
across the sky, they then added many frames together to boost
the signal of any faint objects. Since they tracked the planet’s
motion, stars showed up in the final combined image as streaks
of light, while the moons accompanying the planet appeared
as points of light.
Gladman’s role in these discoveries has been in tracking
these satellites as they orbited around the planet in the
past 18 months.
"The tracking of these extremely faint objects is extremely
difficult, but necessary for without many observations one
cannot calculate their orbits around the planet in order to
learn about their origin," says Gladman, a Canada Research
Chair in Planetary Astronomy.
It now appears that each giant planet’s irregular satellite
population is the result of an ancient collision between a
former moon and a passing comet or asteroid. The discovery
of these moons has opened a window through which scientists
can observe the conditions in the solar system at the time
the planets were forming.
Additional information on the discovery and Prof. Gladman’s
work can be found at: www.astro.ubc.ca/people/gladman/nep2003.html
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