Astrophysics Group

Cavendish Laboratory

Research

The Astrophysics Group carries out a wide range of research activities and projects, with particular emphasis on the fields of optical interferometry, the cosmic microwave background (CMB) radiation, galaxy evolution, star formation and expolanets. There is an increasing theoretical component in the work of the AP Group, both in terms of fundamental physics (in application to relativity and cosmology), gravitational physics, and as modelling and simulation assume more prominent roles in the areas of cosmology and astrophysics. Our activities in these areas embrace the confrontation between observation and theory and the development of instrumentation and technology, such as cm-wave technology and big data/exascale astronomy, where the group is taking a leading role within the SKA telescope project.

For observational work we use a wide range of facilities worldwide in addition to those we have been involved in building. Locally we operate the Mullard Radio Astronomy Observatory a few miles outside Cambridge, where we have developed world-class telescopes including the Ryle Telescope, the Cambridge Optical Aperture Synthesis Telescope (COAST) and the Very Small Array. The VSA is a telescope for studying the CMB and was developed jointly with Jodrell Bank and the IAC Tenerife (where it is now located). The telescopes at Lord’s Bridge have now been joined by the Arcminute MicroKelvin Imager (AMI), which images the CMB at high resolution. This consists of a Small Array of ten 4-metre telescopes, and a Large Array composed of eight 13-metre dishes of the Ryle Telescope, which have been moved into a new configuration.

If you are interested in doing research in any of the areas described, find out a little more using the links on the left and then visit our Graduate Research Opportunities web pages.

 

Research Activities

Optical technology

The main focus of our research is the application of the aperture synthesis technique at optical wavelengths, in order to produce extremely high resolution images of astronomical objects.

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VLT

CMB

A significant fraction of the Astrophysics Group is involved in work on the Cosmic Microwave Background, both experimental and theoretical. We are currently operating the Arcminute Microkelvin Imager, an arcminute-scale survey telescope, and developing analysis techniques for the Planck satellite.

cp_Planck_large

Credit: ESA

Galaxy formation and evolution

The two main research interests within the Galaxy Evolution area are the cosmological evolution of star forming galaxies, in particular the physical mechanisms regulating star formation, and secondly the origin and evolution of radio sources and the effect they have on their environment.  There is mounting evidence that these phenomena are in fact closely related.

BH

Artist’s impression of a Black Hole

Star formation

An understanding of the process of star formation is an essential requirement of theories of galaxy formation and evolution, and gives direct insights into the formation of our own Sun and the number of extra-solar planets we expect to find in the Galaxy. We use telescopes operating at millimetre and sub-mm wavelengths to observe the cool molecular clouds which are collapsing to form stars and help understand the basic physics of star formation. The image shows the Orion A molecular cloud, with SCUBA-2 850 micron emission (red) tracing dust lanes which block the optical light observed with HST (blue).

Orion A molecular cloud, with SCUBA-2 850 micron showing dust lanes blocking optical light observed with HST.

Orion A

Exoplanets

Our research team focuses on the detection and characterisation of extrasolar planets. We are also involved in the development of new instrumentation.

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Exoplanet impression

Theoretical cosmology and gravitational physics

We work on topics in theoretical cosmology and astrophysics, as well as on advanced data analysis methods for cosmology. The active areas of research span inflationary cosmology to novel neural network methods, with a common theme of the confrontation of theoretical predictions with experiment, and the best way to carry this out. Topics addressed include Bayesian Evidence-based comparison of cosmological models and data sets, tests of predictions from modified gravity theories, gravitational wave template detection and analysis, and tests of inflation using data from the Planck Satellite. We also work actively on more theoretical topics involving the construction of modified gravity theories themselves, and the localisation of energy and spin in General Relativity.

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Credit: NASA

Radio cosmology

We have an active research group working on early universe observations at radio wavelengths, a with particular focus on the Epoch of Reionization. We participate in an ongoing project (PAPER: The precision array for probing the Epoch of Reionization) and lead antenna design work for the low frequency array of the Square Kilometre Array.

Hera_HI

Simulation by Dr. Daniel Jacobs of the imaging capabilities of HERA.

Big data/exascale astronomy

Projects such as the SKA are exemplars of big data astronomy and exascale computing.

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SKA artist’s impression

Cm-wave technology

We develop technology for low frequency radio instrumentation; antennas, LNAs, receiving boards, etc. We are currently in charge of the development of antennas for both the SKA-low instrument and the RAPID project.

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SKA antenna elements designed at Cambridge

 

Research Projects

SKA

A further major, and developing, area of the Group’s activity lies in our involvement in the Square Kilometre Array (SKA). This is a worldwide endeavour to create a telescope spanning frequencies from 50 MHz up to at least 10 GHz, with a total collecting area of more than 1 square kilometre, and with the possibility of simultaneous observation of many patches on the sky. Such a telescope would enable fundamental advances in many areas of astrophysics and cosmology. Alongside with our work on SKA we participate in the development of precursor and related telescopes. Currently our group is involved in the development of RAPID, a portable interferometer.

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RAPID

The Radio Array of Portable Interferometric Detectors (RAPID) is being designed for investigations of ionospheric phenomena, solar radio emission, the Galactic synchrotron background, and ultra-high energy cosmic rays via airshower emission. The array will consist of 50-100 small, low-gain broadband antennas operating below 500 MHz. Unlike existing arrays, RAPID can be operated without any cabling between the antennas and a central location, and can be shipped, deployed and physically reconfigured quickly and easily with zero site infrastructure.

rapidJPG

RAPID system

PAPER and HERA

Both PAPER and HERA telescopes will explore the cosmic reionization, which corresponds to the epoch in which the first stars and black holes reionize the neutral intergalactic medium (IGM) that pervades the Universe following recombination, within a few hundred million years of the Big Bang. The epoch of reionization, and the preceding ‘dark ages’ prior to the formation of the first stars, represent the last unexplored phases of cosmic evolution to be tested and explored.

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Possible HERA configuration

MROI

Our pioneering work in optical interferometry has led to our group being partners in the development and construction of a major new instrument, the Magdalena Ridge Optical Interferometer (MROI) being constructed in New Mexico.

Schematic of MROI showing ten telescopes in a close-packed configuration. The shortest baseline in this configuration is 7.5m. Light collected by the telescopes is transported in evacuated beam relay pipes to the Beam Combining Facility building, where the paths travelled by the light from different telescopes are equalised by the delay lines (in the pipes shown top right), before the light beams are interfered on optical tables in the Beam Combining Area.

Planck

Data analysis in the CMB area has become a highly-developed subject in its own right – jointly with the Institute of Astronomy, we are a designated centre for scientific analysis f data from the Planck Surveyor satellite.

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Planck telescope

ALMA

We are strongly involved in the Atacama Large Millimetre Array (ALMA) – a worldwide collaborative project to build a high-resolution millimetre-wave telescope in Chile.

Atacama Large Millimetre Array (ALMA)

JWST

We are involved in the definition, optimisation and scientific exploitation of  NIRSpec, the near-IR multi-object and IFU spectrometer for the James Webb Space Telescope.

MOONS

We are involved in the construction and scientific exploitation of MOONS, the next generation near-IR and optical multi-object spectrograph for the Very Large Telescope.

E-ELT

We are involved in developing the high resolution spectrometer, HIRES, for the European Extremely Large Telescope(E-ELT),  sited on Cerro Armazones in northern Chile.

E-ELT artist view

NGTS

The Next-Generation Transit Survey (NGTS) is a wide-field photometric survey designed to discover transiting Neptune-size and smaller exoplanets around bright stars (magnitude V<13). The NGTS project is a partnership between the University of Cambridge, Queen’s University Belfast, University of Warwick, University of Leicester, Observatoire de Geneve, DLR (Berlin) and Universidad Catolica de Chile.

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Credit: DLR

CHEOPS

The CHaracterizing ExOPlanet Satellite (CHEOPS) will be the first mission dedicated to search for transits by means of ultrahigh precision photometry on bright stars already known to host planets.The CHEOPS project is a partnership between european team members, including the University of Cambridge.

cheops_ext

Credit: ESA

CAMELS

The CAMbridge Emission Line Surveyor (CAMELS) is a pathfinder program to demonstrate on-chip spectrometry at millimetre wavelengths. CAMELS will observe at frequencies from 103–114.7GHz, providing 512 channels with a spectral resolution of R = 3000.

CAMELS

CAMELS detector

AMI Digital Correlator

The primary goal of the AMI Digital Correlator (AMIDC) project is to equip the AMI telescope with a highly channelized digital correlator system giving more flexibility in the location of this band and a much more uniform response across it.

The AMI Small Array

The AMI Small Array

Variable Dielectric Delay Lines in Liquid Crystals for Phased Array Feeds

In this project we seek to exploit a novel liquid crystal technology, which allows a controllable true time delay to be applied to an RF signal of frequencies up to tens of GHz. The basic technology has already been demonstrated and has a wide variety of applications. We now intend to use this technology to construct a real astronomical demonstration system for delay lines and show that these can be integrated into the beamforming module of an existing Phased Array Feed (PAF) instrument, dramatically improving its capabilities.

PHAROS

PHAROS array