Astrophysics Research Overview
Wide Angle Search for Planets
Searching for planetary transits is a demonstrated technique for
the discovery of new planets beyond the solar system. The Wide
Angle Search for Planets (WASP) is undertaking a comprehensive,
wide-field sky survey to detect planetary transits in stars down
to 18th magnitude. With greatly increased numbers of known
extra-solar planets we will investigate the accretion
processes that lead to planet formation, and thus better
understand the origin of our own home. WASP will also provide
a wealth of data on all classes of variable stars, allowing the
systematic analysis of large samples and the discovery of new
and rare variable types.
For further information see our WASP@Keele homepage.
Quick tours of the H-R diagram
When a star like the Sun exhausts its fuel its internal structure undergoes
major changes and it moves away from the main sequence of the Hertzsprung
Russell diagram. During this phase of evolution it seeds the interstellar
medium with dust and gas in the form of a wind, providing the raw materials
for the formation of new stars. This research involves using infrared and
sub-millimeter telescopes to probe the latter stages of stellar evolution,
particularly those stars that evolve on the timescale of a human lifetime.
These include not only the 'born-again' stars, which re-ignite some of
their fuel as they head towards the white dwarf region of the H-R diagram,
but also the explosions of novae, in which thermonuclear runaway occurs on
the surface of a white dwarf in a close binary system.
For further information see the Nye Evans' homepage.
Accretion in compact binary stars
Accretion is one of the most widespread and important phenomena in
the universe. It is the dominant source of X-rays in the universe,
powering X-ray sources from black-hole binaries to active galaxies.
Accretion discs are also crucial in the formation of stars and contain
the material out of which planets grow. Close binary stars provide
the best opportunities for studying the physical processes of
accretion. Keele's programme investigates accretion onto neutron
stars and white-dwarf stars, using satellites such as XMM, Chandra
and HST, complemented by ground-based telescopes. A particular
strength is the understanding of magnetically channelled accretion,
where the accretion process interacts with a strong magnetic field
on the compact star.
For further information see Coel Hellier's homepage.
Low-mass stars in clusters and associations
Stars like the Sun or of even lower mass are born in clusters and
associations. We search for young Suns, low-mass stars and brown dwarfs
in star forming regions and clusters in order to find how common they
are in a variety of environments and follow the temporal evolution of
their discs, rotation rates, magnetic activity and chemical abundances.
Our goals are to understand the way in which birth environment influences
the development of low-mass stars (and their planetary systems) and to
investigate the astrophysics, such as mixing, convection and magnetic
fields, that are incorporated into pre main sequence evolutionary models.
For further information see Rob Jeffries' homepage.
Stellar and interstellar physics as drivers of galaxy evolution
Galaxies evolve because stars form and die within them. This cycle depends
on the dynamics of the interstellar medium... and affects it. Galaxies are also
stirred by external disturbances such as galaxy-galaxy encounters. The ecology
in which stars and galaxies take part is subject of a diverse range of
observational programmes at Keele. These include the physics of molecular clouds
and star formation, stellar feedback and supernova remnants, and the structure
and dynamics of the interstellar medium from the smallest, au scales to the
largest, global galactic scales. We study these processes in the Milky Way and
other nearby galaxies such as the Magellanic Clouds and spiral galaxies within
about 7 Mpc distance, where we can still study the individual red supergiant
progenitors of supernovae.
For further information see Jacco van Loon's homepage.
Observations of close binary stars
Many stars are found in pairs (binaries) and orbit around each other with
orbital periods of years, weeks, days or even every few hours. These stars
have often interacted very strongly and may have exchanged mass or thrown
their outer layers out of the binary system. This can produce some of the most
dramatic objects in the sky, e.g., black hole X-ray binaries and Type-Ia
supernovae. It is difficult to predict how stars behave when they interact
strongly, so research at Keele uses surveys to find simpler examples of close
binary stars which have interacted in the past, and may do again, but are
currently not exchanging mass. We then study these binaries in more detail to
measure their properties, e.g., the number in the galaxy, their distribution
of orbital periods or the masses and sizes of the stars. This research gives
information which is being used to understand the properties of many types of
interacting binary stars.
For further information see Pierre Maxted's homepage.
Atmospheric Parameters of Stars
The stellar atmospheric parameters of effective temperature and surface
gravity are of fundamental astrophysical importance. They are the
prerequisites to any detailed abundance analysis. As well as defining the
physical conditions in the stellar atmosphere, these parameters are
directly related to the physical properties of the star; mass, radius and
luminosity. Model atmospheres are our analytical link between the physical
properties and the observables - flux distributions and spectral line
profiles. We can obtain effective temperature and surface gravity from
suitable observations, assuming of course that the models we use are
adequate and appropriate.
For further information see Barry Smalley's homepage.
Stellar Hydrodynamics, Evolution and Nucleosynthesis (SHEN)
The SHEN group, lead by Dr Raphael Hirschi, studies stars and related topics like
gamma-ray bursts (GRBs), supernovae (SNe) and the origin of elements
by performing numerical simulations. Simulations include both multi-D hydrodynamics simulations and standard 1D stellar evolution models.
Models are being computed at
metallicities ranging from solar down to very low metallicities and
from the main sequence until the pre-supernova stage. These models
are able to predict properties of the star during its evolution
(mass, surface composition and position in the HR diagram), long and
soft GRB rates coming from single stars and the production of
chemical elements in massive stars. The main focus of the group is currently the ERC-funded SHYNE project.
For further information see Raphael Hirschi's homepage.
Active Galactic Nuclei
The nuclei of all galaxies, including our own Milkyway, are thought
to contain super-massive black holes, ranging in mass from a
few million to a few billion times that of our Sun.
While the nuclei of some galaxies remain dormant, a substantial
fraction radiate vast amounts of energy, greater than all the starlight
in one whole galaxy combined. The intense emission from these
so-called Active Galactic Nuclei (or AGN) can occur in a region smaller than
the size of our own Solar System, via accretion of matter onto the
supermassive black hole. The emission closest to the black hole event
horizon is in the form of high energy radiation, such as X-rays. Research
into the high energy emission from AGN is conducted
with space-based observatories such as XMM-Newton, Chandra, Suzaku, RXTE and
Integral. By studying the atomic X-ray line emission from elements such as
iron, the properties of the very hot, innermost regions around super-massive
black holes can be deduced. The iron line emission can be warped by
relativistic effects near to the black hole and provides a direct probe of
the black hole's strong gravitational pull.
For further information contact James Reeves.
Research is conducted into Gamma-ray bursts, otherwise known as
GRBs. GRBs are thought to be the most powerful explosions in the known
Universe, however until recently their origins were largely unknown. Recent
research is showing that some types of GRB are linked with energetic
supernovae, occuring in many distant galaxies throughout the Universe,
associated with regions of intense star formation. A new
development includes the detection of many high redshifts bursts, including
one such burst at a redshift of z=6.3, one of the most distant known objects
in the Universe. The study of distant high redshift bursts is important to
our understanding of the early Universe shortly after the Big Bang and to
how the first stars and galaxies formed.
For further information contact James Reeves.
The Large and Small Magellanic Clouds are the nearest templates for the detailed
study of star formation under metal-poor conditions. These galaxies mirror the
conditions typical of galaxies during the early phases of their assembly,
providing a stepping stone to understand star formation at high redshift where
such processes can not be directly observed. Furthermore, they provide the
exciting new opportunity of bridging the gap between star formation processes
on large galactic-wide scales and on the small scales of individual young
stellar objects (YSOs).
The advent of the Spitzer Space Telescope finally allowed the identification of
sizable samples of early-type YSOs across the whole MCs. The Spitzer Legacy
Programs (SAGE and SAGE-SMC) have photometrically identified 1000s of previously
unknown YSOs, while the Herschel Legacy program (HERITAGE) is revealing the
youngest, most embedded YSOs, that are only accessible at longer wavelengths
Using Spitzer, Herschel and ground-based spectroscopic facilities we investigate
the detailed properties of gas- and solid-state chemistry at sub-solar
metallicity. Any variations on the gas and ice phase chemistries could imply
significant variations in gas-phase abundances of oxygen, carbon, water and CO,
that consequently impact the ability of the YSO envelopes to cool and its early
evolution. We use galaxy-wide photometric surveys to constrain the Initial mass
function and star formation rates across the whole system in order to link the
environmental conditions to the star formation outcomes.
For further information contact Joana Oliveira