Dennis Stello's page
The Kepler satellite at Ball Aerospace & Technologies
I am an astrophysicist at the School of
Physics at the University of New South Wales where I am
heading the Stellar Oscillations Group.
To contact me see my contact details.
My main area of research is asteroseismology
-- the study of stars through the interpretation of their
oscillations -- which aims to understand stellar structure and
In particular, my interest and expertise are within:
- Observation and interpretation of stellar oscillations
- Modelling stellar evolution and pulsation
- Solar-like oscillations
- Stellar clusters
- Red giant stars
- Automatic data analysis software
Dennis Stello's publications and
Main research infrastructure:
research is centred around the analysis of data from NASA's Kepler, K2
, and TESS
missions. My role as
member of the Kepler Asteroseismic Science Consortium (KASC
and leader of two working groups involved the target selection and
analysis of Kepler data. I also work on the Kepler mission's new
life, called K2, which we are using for Galactic Archaeology
I am chair of the working group working on the asteroseismology of
red giant stars in the TESS Asteroseismic Science Consortium (TASC
I am part of the Stellar
Oscillation Network Group
, which uses ground-based
high-precision radial-velocity measurement to detect the Doppler
shift of stars caused by their oscillations.
M67 open cluster
campaigns. I led a global multi-site observing campaign with
about a dozen telescopes in Australia, Asia, Africa, Europe,
North- and South America. The aim was to detect stellar
oscillations on a large number of stars that were all 'born' at
the same time out of the same cloud of interstellar gas. I was
part of the core team that re-observed the stars with NASA's K2
mission, and led the publication reporting the team's first
you blow through a trumpet, plug the string of a guitar, or
move your finger across the rim of the wine glass to make it
ring, you are creating standing sound waves. These sound
waves depend on the physical properties of the 'ringing'
object, such as its size and shape, its temperature, and
what it is made of. For example, a full wine glass with
water sounds differently than when it is empty. If you play
a trumpet at room temperature it sounds differently than if
you had just taken it out of a freezer. And while a violin
and a cello look very similar you will have no trouble
telling which is which purely from the sound they produce.
In a similar way astronomers can obtain knowledge about the
interiors of stars, like their size, temperature, and
internal structure by measuring the frequencies of the
oscillations caused by standing sound waves inside the
stars. This technique-- called Asteroseismology -- is
analogue to 'Earth'-seismology where geologists measure
sound waves in the Earth triggered by earthquakes to find
out what the Earth's interior is made of.
The oscillations in a star makes the star ring like a large
spherical bell, with regions of compression and expansion as
illustrated in the cartoon as yellow and red regions.
Detecting the oscillations can be done by measuring the Doppler shift of the
light from the surface of the star, which measures the speed
by which the surface is literally moving in and out as the
star oscillate (vibrate). The surface of a star like the Sun
will only move in and out by about 100m with speeds of a few
metres per second, roughly walking speed, while a more
evolved star like a Red Giant will oscillate more vigorously
with amplitudes 10 to 100 times larger. Another technique is
to measure the brightness
of the star as it changes due to the compression and
expansion. These brightness variations are of the
order of a few parts per million (less than 0.001%) for a
Sun-like star, and about 0.01 to 0.1% for a Red Giant.
It is truly amazing that these tiny oscillations in a star
many light years away can be measured from Earth!
|Listen to the sound
of the stars (sound based on observed frequencies,
scaled to the human audible range):
alpha Cen A A star
slightly older and bigger than the Sun.
A more massive and much more evolved red giant star,
with a radius 10 times that of the Sun.
concert Starting with the sound of a small red
giant you will gradually hear three stars of
increasing size - entering the "red giant
Oscillating star (credit: DASC)
Marc Hon (PhD: University of New South Wales)
Hafiz Mohd (PhD: University of New South Wales)
Jason Drury (PhD: University of Sydney)
Doug Compton (PhD: University of Sydney)
Joel Zinn (PhD: Ohio State University)
Beau Bellamy (MSc: University of Sydney)
Jason Drury (Hons: University of Sydney)
Bhuwan Ghimire (PhD: University of Sydney)
Jacob Richter (Hons: University of Sydney)
Daniel Sultmann (Hons: University of Sydney)
Julie Lykke (MSc: Aarhus University)
Enrico Corsaro (PhD: University of Catania)
Timothy White (PhD: University of Sydney)
Daniel Huber (PhD: University of Sydney)
Media and outreach:
AI reveals the
true age of
Hon and his
the team to
not been able
to do. This
stars in great
tells us that
team led by
joined by his
stars in two
suggest that the
energy of star
Australian (press) (pdf)
- Astronomers find ancient magnetic
field hiding inside retired stars
A team led
by Dennis Stello, and
including Daniel Huber and Tim
the University of Sydney
has found that strong magnetic
fields in the cores of stars
ABC 1 (TV) news report (download)
- Kepler 37-b: The smallest planet found
discovery of Kepler 37-b marked the smallest
planet found so far. With a size similar to our
moon this was a
suggesting that small planets are abundant in
the Galaxy. Dennis Stello and Tim Bedding at the University
of Sydney helped pin down the size of the host star
(Kepler 37) and hence that of the planet itself.
A year of swashbuckling advances (February 2012).
Age's annual review of the big things in the world of
science anno 2011 gives special mention to
Stello and Tim Bedding
of Sydney and their recent results on the asteroseismology of a
planet hosting star.
- Aging stars are slow on
the outside but fast on the inside (December 2011).
of fast spinning cores in old red giant stars
Sydney Morning Herald
Asteroseismology confirms habitable Super-Earth around
Sun-like star (December 2011).
team at the University of
used data from NASA's Kepler Mission to measure the
mass and size of the planet hosting star Kepler 22 and found it to
be almost identical to the Sun.
Sydney Morning Herald
Star quakes in hundres of stars (January 2010).
first results from the Kepler Mission led by the team at
the University of
- Launch of NASA's Kepler telescope (March 2009).
first mission to be capable of detecing Earth-sized
planets orbiting distant sun-like stars.
will use the Kepler data to study stellar
Northern star breathes new life (July 2008).
After over 100 years of decline in its oscillation amplitude the
Northern star takes astronomers by surprise.
- Ultrabass Sounds of the
Giant Star Xi Hya (April 2002).
first asteroseismic observation of a star very different
from the Sun.
ESO press release (ESO