University of Notre Dame astronomer Peter Garnavich,
Notre Dame professor of physics, is co-investigator on the largest
Hubble project ever undertaken, one that will watch galaxies form
and hunt for distant explosions. Astronomers will peer deep into the
universe in five directions to document the early history of star
formation, galaxy evolution and find distant supernova explosions
in the ambitious new project, which will require an unprecedented
amount of time on the Hubble Space Telescope.
"The new instruments installed and ones repaired
by astronauts last year have made this investigation possible: it
is like having a new, even bigger telescope," Garnavich said.
By imaging more than 250,000 distant galaxies, the
project will provide the first comprehensive view of the structure
and assembly of galaxies over the first third of cosmic time. It also
will yield crucial data on the earliest stages in the formation of
supermassive black holes and find distant supernovae important for
understanding dark energy and the accelerating expansion of the universe.
The project is led jointly by Henry Ferguson of the
Space Telescope Science Institute and Sandra Faber of the University
of California, Santa Cruz. The effort relies on Hubble’s powerful
new infrared camera, the Wide Field Camera 3 (WFC3), as well as the
telescope’s repaired Advanced Camera for Surveys (ACS).
The program, which brings together a large international
team of collaborators, was awarded a record 902 orbits of observing
time as one of three large-scale projects chosen for the Hubble Multi-Cycle
Treasury Program. It takes Hubble 97 minutes to make one orbit, so
observing time totals about two months but will be spread out over
the next two to three years.
A powerful telescope like Hubble allows astronomers
to see back in time as it gathers light that has traveled for billions
of years across the universe. The new survey is designed to observe
galaxies at distances that correspond to “look-back times” from 9
billion years ago to about 13 billion years in the past, or only about
600,000 years after the Big Bang. Of all the stars in the universe,
only about 1 percent had formed at the time of the most distant epoch
included in the survey.
The new data will be used to answer many key questions
about galaxy evolution and cosmology. By studying how galaxy masses,
morphologies and star formation rates changed over time, researchers
can test theories of galaxy formation and evolution.
Another important component of the project is the
search for distant examples of a particular type of exploding star
known as a Type Ia supernova.
Astronomers have used the uniform brightness of these
supernovae to measure cosmic distances, leading to the conclusion
that a mysterious force called dark energy is accelerating the expansion
of the universe. Observations of distant Type Ia supernovae will enable
researchers to study how the rate of expansion of the universe has
changed over time.
Garnavich was on one of the two teams that first
discovered the accelerating universe back in 1998.
"In these deep Hubble observations we should find
a handful of very distant supernovae that exploded before cosmic acceleration
started,” Garnavich said. “This will be a great test of whether we
really understand what the supernovae are telling us."
Data from this project will be made available to the entire
astronomy community with no proprietary period.
"The idea is to provide a unique and large data set that could
not have been built by adding together many small projects,” Garnavich
said. “These Multi-Cycle Treasury program images will be used by anyone
trying to understand how galaxies were put together."
Additional information about the project is available
at the Space
Telescope Web site.