Tag Archive for 'astronomy'

HD 98800 – the polar circumbinary disk

As outlined in the paper and the press release (free PDF here), we have discovered that the HD 98800 quadruple star system hosts a disk that orbits at right angles to the binary it surrounds.

Here is Fig. 1 from the paper, which shows the setup. If the geometry of the disk around the inner binary doesn’t make sense, try taking a look at this simulation.

The HD 98800 system
The HD 98800 system

What does this show? The system has two binaries, A and B, which orbit each other at a distance of about the Pluto-Sun distance. Since both A and B are binaries, the individual stars are called Aa and Ab, and Ba and Bb. The “inner binary” BaBb is surrounded by a ring of gas and dust about the size of the Asteroid belt, this is shown in the right panel. All that is then orbiting the other binary, AaAb. The curious thing is that none of the orbital planes are aligned, and the BaBb plane is at right angles to the plane of the disk.

This system should prove very valuable to people that are interested in disk physics – here we can quantify the effects of the stars on the disk so compare the data with models. Of course, it’s possible that the disk is forming planets, and there is evidence that suggests this is underway, meaning that polar circumbinary planets may exist and be found in the future!

Mauna Kea Frost



Herschel SPIRE time

16.5hrs of Herschel SPIRE time: check(0)


Herschel proposal submitted, love that cute little cheetah that’s always popping up!(0)

Astronomy: quite useful actually

astronomy saves lives and is useful for once!(0)

Thesis submission

Though I printed it a while ago, my PhD thesis was submitted yesterday. Thanks for three years of tax-free employment Australia!(0)


Curious, my photo of the nifty moon-jupiter-venus configuration generated half as many visits as my most popular blog entry, but in only a few days. It appears the title “smiley moon” was what everyone would be googling…(0)

Smiley moon

Go out and look at the moon tonight. Venus and Jupiter are nearby making a smiley face. Maybe it will cheer the world up some…

smiley face moon

smiley face moon

Thinking ahead

“It is clear, however, that there are a lot of open questions but we believe that we have disclosed a thinkable strategy how to survive the Red Giant catastrophe of our Sun without violating known laws of Nature. To our best knowledge this is the first time that somebody speculated about such a kind of Planetary Engineering.”-  Taube & Seifritz (2008)

Now that’s thinking ahead… though given the mess we’ve made in 150 years of industrialisation, perhaps ensuring our planet is habitable in 100 years would be more of a priority, rather than problems that will arise in 1,000,000,000 years.

This is secret…



Telescope pier

This is part of one of the old burnt out telescopes at Mt Stromlo.

old telescope

old telescope

ASA conference done

The ASA conference ended nicely. Well worth the trip over to check the place out.

Apparently someone said “He always looks like he just got out of bed, but seems to know what he’s talking about” when I got up to advertise my poster. Best praise from a stranger I’ve had for ages…

Holiday time!

Nothing to do

The weather was rubbish all night, so I had nothing to do. I took a photo just before bed time when I was refilling the dewar…

filling the dewar

More photos here

SSO Sunrise

I stayed up a wee bit later this morning to watch the sun come up. Well worth it.

sso sunrise

More photos here.

eta Aquarid meteor shower: captured!

At the end of last night we were taking a few images of a supernova. In the second image we managed to get a passing satellite in the frame, pretty unusual but it happens. The third appeared to have something like a plane, but it wasn’t flashing. The reason? We think the ‘plane’ was a meteor from the eta Aquarids, pieces of Halley’s comet. It went straight through the middle of the supernova’s host galaxy! Well it did from our vantage point anyway…

eta Aqaurid

Warrumbungle National Park

I’m at Siding Spring Observatory near Coonabarabran in NSW this week. I’m looking for planets via the transit technique for my friend Dan. The observatory is situated in a national park, with great views of the park and surrounding terrain.


There are more photos here.

Old Perl IRAF module and (e)cl

So I found this old perl module Astro::IRAF::CL.pm which is a perl interface to the IRAF cl. It’s rather old and doesn’t work because the ecl is too high tech for the old module. I fixed this by changing the CL.pm file on line 127:

my $t = Expect->spawn('cl') || croak "Cannot spawn CL: $!";


my $t = Expect->spawn('cl -old') || croak "Cannot spawn CL: $!";

so that the module uses the old cl rather than the extended one. I also changed the maximum line length allowed in the _break_into_strings subroutine to stop error messages. I ran into trouble with too long lines (help pages say see hconfig$iraf.h, mine is a binary however) so put it back. All seems to work fine….

Hot Super-Earths: accepted!

We have received the excellent news that my third paper has been accepted to ApJ. The paper is about possible mechanisms by which Earth-Neptune (low-)mass planets can reach very close orbits. Using standard models we find trends that might be found by future discoveries, and think about what we can learn from them.

Discovery of low-mass planets (which don’t have large Juipter-like atmospheres) will be particularly interesting, because they may be habitable due to (maybe) having solid surfaces. Unfortunately planets are much easier to find when they’re orbiting very close to their parent stars, and too hot to be habitable. Therefore, if they exist, the first decent sample of low mass planets will be discovered in short-period, close-in orbits.

It’s unlikely that planets in these orbits would form there, because it’s hard to form anything at all close to the star. Therefore, from a formation point of view, there are two main ways these planets
could get to close-in orbits after forming further out: by scattering off other planets, or by migrating through the disk out of which they form. In our paper, we show that planets that scatter will be hard to detect, and that migration is a better mechanism.

At present, very little is known about migration of planets in the “super-Earth” mass range, so discovery of these planets should tell us something about how migration works. Alternatively, we might not find any low-mass planets in short-period orbits, which would tell us that migration doesn’t work how current wisdom says. So either way we learn something!

The paper is posted on astro-ph for now, until the journal publishes it.

Third paper resubmitted

Thanks to a nice referees report, and some simulations finally finishing, I submitted a revised version of our “Hot super-Earths” paper this morning. Hopefully all will be well and that will be number three!(0)


I am a Royal Society University Research Fellow based in the Astronomy and Astrophysics Group at the University of Warwick, UK. I work on various theoretical and observational aspects of planet formation and the end results – planets and debris disks – as seen around nearby stars. Among other topics, I have recently worked on transiting dust populations, what debris disks may tell us about the alignment of orbits in stellar and planetary systems, and the possible impact of exo-Zodiacal dust on future missions to image Earth-like planets around other stars. I am/have been involved in many collaborations, including large surveys such as ALMA REASONS, LBTI HOSTS, NaCo ISPY, Herschel DEBRIS, JCMT SONS, and Spitzer SpiKeS.


HD 98000. This is a binary star comprising two sun-like components, surrounded by a thick disc of material. What’s different about this system is that the plane of the stars’ orbits is inclined at almost 90 degrees to the plane of the disc.
University of Warwick/Mark Garlick
KIC8462852 PDS110  
HD181327 HD181327 tau Ceti
Fomalhaut C kappa CrB HD181327
eta Crv 61 Vir and GJ 581 snow line


  • Orbital element constraints for linear motion a la Pearce et al (2015). Underlying python scripts here.
  • sdf – SED fitting library, still under development but some of the core bits are fairly stable (e.g. synthetic photometry)
  • alma – simple semi-analytic optically-thin disk image generation, primarily for visibility modelling of ALMA data

Refereed Papers

These, and other related proceedings and proposals, can be found on ADS or orcid.org.
2020 (3/18|28/130)
  • Planet formation in intermediate-separation binary systems, Panic et al., MNRAS in press
  • Rapid CO gas dispersal from NO Lup’s class III circumstellar disc, Lovell, Kennedy, et al., MNRASL in press
  • Hiding signatures of gravitational instability in protoplanetary discs with planets, Rowther et al., ApJL in press [ ADS | press ]
  • ALMA Survey of Lupus Class III Stars: Early Planetesimal Belt Formation and Rapid Disk Dispersal, Lovell et al., MNRAS in press [ ADS ]
  • Mutual inclinations between giant planets and their debris discs in HD 113337 and HD 38529, Xuan, Kennedy et al., MNRAS [ ADS ]
  • Insights into the planetary dynamics of HD 206893 with ALMA, Marino et al., MNRAS [ ADS ]
  • Spin-Orbit Alignment of the beta Pictoris Planetary System, Kraus et al., ApJL [ ADS ]
  • The unexpected narrowness of eccentric debris rings: a sign of eccentricity during the protoplanetary disc phase, Kennedy, RSOS [ ADS ]
  • A low-mass stellar companion to the young variable star RZ Psc, Kennedy et al., MNRASL [ ADS ]
  • Survey of planetesimal belts with ALMA: gas detected around the Sun-like star HD 129590, Kral et al., MNRAS [ ADS ]
  • No significant correlation between radial velocity planet presence and debris disc properties, Yelverton, Kennedy, & Su, MNRAS [ ADS ]
  • Herschel Observations of Disks Around Late-type Stars, Tanner et al., PASP [ ADS ]
  • A remnant planetary core in the hot Neptunian desert, Armstrong et al., Nature [ ADS | PDF | press ]
  • The HOSTS survey for exozodiacal dust: Observational results from the complete survey, Ertel et al., AJ [ ADS ]
  • ISPY – NACO Imaging Survey for Planets around Young stars, Survey description and results from the first 2.5 years of observations, Launhardt et al., A&A [ ADS ]
  • Searching for a dusty cometary belt around Trappist-1 with ALMA, Marino et al., MNRAS [ ADS ]
  • Constraining planet formation around 6-8M_sun stars, Veras et al., MNRAS [ ADS ]
  • Are Inner Disc Misalignments Common? ALMA Reveals an Isotropic Outer Disc Inclination Distribution for Young Dipper Stars, Ansdell et al., MNRAS [ ADS ]
2019 (3/19|25/112)
  • An unusually large gaseous transit in a debris disc, Igelsias et al., MNRAS [ ADS ]
  • Dust production in the debris disk around HR 4796 A, Olofsson et al., A&A [ ADS ]
  • A statistically significant lack of debris discs in medium separation binary systems, Yelverton, Kennedy et al., MNRAS [ ADS ]
  • A Gap in the Mass Distribution for Warm Neptune and Terrestrial Planets, Armstrong et al., ApJL [ ADS ]
  • The REASONS Survey: Resolved Millimeter Observations of a Large Debris Disk Around the Nearby F Star HD 170773, Sepulveda et al., ApJ [ ADS ]
  • ISPY – NaCo Imaging Survey for Planets around Young stars – Discovery of an M dwarf in the gap between HD 193571 and its debris ring, Musso-Barcucci et al., A&A, [ ADS ]
  • A transiting exocomet detected in broadband light by TESS in the beta Pictoris system, Zieba et al., A&A [ ADS | githubpress ]
  • Extreme Debris Disk Variability — Exploring the Diverse Outcomes of Large Asteroid Impacts During the Era of Terrestrial Planet Formation, Su et al., ApJ [ ADS ]
  • Kuiper Belt-Like Hot and Cold Populations of Planetesimal Inclinations in the beta Pictoris Belt Revealed by ALMA, Matra et al., AJ [ ADS ]
  • ISPY – the NaCo Imaging Survey for Planets around Young stars: A young companion candidate embedded in the R CrA cloud, Cugno et al., A&A [ ADS ]
  • High-resolution spectroscopy of Boyajian’s star during optical dimming events, Martinez-Gonzalez et al., MNRAS [ ADS ]
  • The PDS 110 observing campaign — photometric and spectroscopic observations reveal eclipses are aperiodic, Osborn et al., MNRAS [ ADS ]
  • A circumbinary protoplanetary disc in a polar configurationKennedy et al., Nature Astronomy [ PDF | ADSweb | press ]
  • Spectral and orbital characterisation of the directly imaged giant planet HIP 65426 b, Cheetham et al., A&A [ ADS ]
  • A gap in HD 92945’s broad planetesimal disc revealed by ALMA, Marino et al., MNRAS [ ADS ]
  • The Little Dippers: Transits of Star-grazing Exocomets?, Ansdell et al., MNRAS [ ADS ]
  • The wavelength dependence of interstellar polarization in the Local Hot Bubble, Cotton et al., MNRAS [ ADS ]
  • An automated search for transiting exocomets, Kennedy et al., MNRAS [ ADSgithub ]
  • Detection of a giant flare displaying quasi-periodic pulsations from a pre-main sequence M star with NGTS, Jackman et al., MNRAS [ ADS ]
2018 (4/21|23/93)
  • Comprehensive analysis of HD 105, a young Solar System analog, Marshall et al., MNRAS [ ADS ]
  • Using warm dust to constrain unseen planets, Bonsor et al., MNRAS [ ADS ]
  • Constraining the presence of giant planets in two-belt debris disk systems with VLT/SPHERE direct imaging and dynamical arguments, Matthews et al., MNRAS [ ADS ]
  • Empty gaps? Depleting annular regions in debris discs by secular resonance with a two-planet system, Yelverton & Kennedy, MNRAS [ ADS ]
  • The KIC 8462852 Light Curve From 2015.75 to 2018.18 Shows a Variable Secular Decline, Schaefer et al., MNRAS [ ADS ]
  • A gap in the planetesimal disc around HD 107146 and asymmetric warm dust emission revealed by ALMA, Marino et al., MNRAS [ ADS ]
  • Unlocking the secrets of the midplane gas and dust distribution in the young hybrid disc HD 141569, Miley et al. A&A [ ADS ]
  • Exocomet Orbit Fitting: Accelerating Coma Absorption During Transits of beta Pictoris, Kennedy, MNRAS [ ADS | github ]
  • Infrared colours and inferred masses of metal-poor giant stars in the Kepler field, Casey, Kennedy et al. MNRAS [ ADS ]
  • An Empirical Planetesimal Belt Radius – Stellar Luminosity Relation, Matra, Marino, Kennedy et al, ApJ  [ ADS ]
  • The HOSTS survey – Exo-zodiacal dust measurements for 30 stars, Ertel et al., AJ [ ADS | press ]
  • Circumbinary, not transitional: On the spiral arms, cavity, shadows, fast radial flows, streamers and horseshoe in the HD142527 disc, Price et al., MNRAS [ ADS ]
  • Kuiper Belt Analogues in Nearby M-type Planet-host Systems, Kennedy et al., MNRAS [ ADS ]
  • Discovery of New Dipper Stars with K2: A Window into the Inner Disk Region of T Tauri Stars, Hedges, Hodgkin, & Kennedy, MNRAS [ ADS ]
  • ALMA observations of the narrow HR 4796A debris ring, Kennedy et al, MNRAS [ ADS ]
  • Shaping HR8799’s outer dust belt with an unseen planet, Read et al, MNRAS [ ADS ]
  • A-type Stellar Abundances: A Corollary to Herschel Observations of Debris Disks, Draper et al., ApJ, [ ADS ]
  • The First Post-Kepler Brightness Dips of KIC 8462852, Boyajian et al, ApJL [ ADS | press ]
  • Analysis of the Herschel DEBRIS Sun-like star sample, Sibthorpe, Kennedy, et al, MNRAS [ ADS ]
  • Modelling the KIC8462852 light curves: compatibility of the dips and secular dimming with an exocomet interpretation, Wyatt et al, MNRAS [ ADS ]
  • Optical Polarimetry of KIC 8462852 in May-August 2017, Steele et al, MNRAS [ ADS ]
2017 (1/13|20/72)
  • Extinction and the Dimming of KIC 8462852, Meng et al, ApJ [ ADS | press | more press ]
  • The First Scattered Light Image of the Debris Disk around the Sco-Cen target HD 129590, Matthews et al., ApJL [ ADS ]
  • SONS: The JCMT legacy survey of debris discs in the submillimetre, Holland, Matthews, Kennedy et al, MNRAS [ ADS ]
  • Periodic Eclipses of the Young Star PDS 110 Discovered with WASP and KELT Photometry, Osborn et al, MNRAS [ ADS | press ]
  • A Complete ALMA Map of the Fomalhaut Debris Disk, MacGregor et al, MNRAS [ ADS | press ]
  • Detection of exocometary CO within the 440 Myr-old Fomalhaut belt: a similar CO+CO$_2$ ice abundance in exocomets and Solar System comets, Matra et al, MNRAS [ ADS | press ]
  • ALMA observations of the multiplanet system 61 Vir: What lies outside super-Earth systems?, Marino et al, MNRAS [ ADS ]
  • The Northern Arc of epsilon Eridani’s Debris Ring as Seen by ALMA, Booth et al, MNRAS [ ADS ]
  • Predictions for the secondary CO, C and O gas content of debris discs from the destruction of volatile-rich planetesimals, Kral et al, MNRAS [ ADS | press ]
  • The transiting dust clumps in the evolved disk of the Sun-like UXOr RZ Psc, Kennedy et al, RSOS [ ADS | RSOS | github ]
  • First scattered-light images of the gas-rich debris disk around 49 Ceti, Choquet et al, ApJL [ ADS ]
  • Discovery of a low-mass companion inside the debris ring surrounding the F5V star HD 206893, Milli et al, A&A [ ADS ]
  • ALMA observations of the eta Corvi debris disc: inward scattering of CO-rich exocomets by a chain of 3-30 M_Earth planets?, Marino et al, MNRAS [ ADS ]
2016 (0/12|19/59)
  • The SHARDDS survey: first resolved image of the HD114082 debris disk in Lower Centaurus Crux with SPHERE, Wahhaj, Milli, Kennedy et al, A&A [ ADS ]
  • Dipper disks not inclined towards edge-on orbits, Ansdell et al, MNRASL [ ADS ]
  • ALMA Observations of the Debris Disk of Solar Analogue tau Ceti, MacGregor et al, ApJ [ ADS ]
  • Deep LMT/AzTEC millimeter observations of epsilon Eridani and its surroundings, Chavez et al, MNRAS [ ADS ]
  • The Gaia-ESO Survey: revisiting the Li-rich giant problem, Casey et al, MNRAS [ ADS ]
  • Exocometary gas in the HD 181327 debris ring, Marino et al, MNRAS [ ADS | press ]
  • Effects of disc asymmetries on astrometric measurements, Kral et al, A&A [ ADS ]
  • Polarization measurements of hot dust stars and the local interstellar medium, Marshall et al, ApJ [ ADS ]
  • Nulling Data Reduction and On-Sky Performance of the Large Binocular Telescope Interferometer, Defrere et al, ApJ [ ADS ]
  • Planet Hunters X. KIC 8462852 – Where’s the Flux? Boyajian et al, MNRAS [ ADS | press | kickstarter ]
  • IR-excesses around nearby Lambda Boo stars are caused by debris disks rather than ISM bow waves, Draper et al, MNRAS [ ADS ]
  • Young “Dipper” Stars in Upper Sco and rho Oph Observed by K2, Ansdell et al, ApJ [ ADS ]
2015 (4/11|19/47)
  • The AU Mic debris disk: far-infrared and submillimeter resolved imaging, Matthews, Kennedy et al, ApJ [ ADS ]
  • Kuiper belt structure around nearby super-Earth host stars, Kennedy et al, MNRAS [ ADS ]
  • Warm exo-Zodi from cool exo-Kuiper belts: the significance of P-R drag and the inference of intervening planets, Kennedy & Piette, MNRAS [ ADS ]
  • Stellar Multiplicity and Debris Disks: An Unbiased Sample, Rodriguez et al, MNRAS [ ADS ]
  • Constraining the orbits of sub-stellar companions imaged over short orbital arcs, Pearce, Wyatt, & Kennedy, MNRAS [ ADS ]
  • Does the Presence of Planets Affect the Frequency and Properties of Extrasolar Kuiper Belts? Results from the Herschel DEBRIS and DUNES Surveys, Moro-Martin, Marshall, Kennedy, et al., ApJ [ADS ]
  • Five steps in the evolution from protoplanetary to debris disk, Wyatt, Panic, Kennedy, & Matra, Ap&SS [ ADS ]
  • Exo-zodi modelling for the Large Binocular Telescope Interferometer, Kennedy et al, ApJS [ ADS | PDF ]
  • Target Selection for the LBTI Exozodi Key Science Program, Weinberger, Bryden, Kennedy et al, ApJS [ ADS | PDF ]
  • First-light LBT nulling interferometric observations: warm exozodiacal dust resolved within a few AU of eta Crv, Defrere et al, ApJ [ ADS | PDF | press ]
  • Nature or nurture of coplanar Tatooines: the aligned circumbinary Kuiper belt analogue around HD 131511, Kennedy, MNRAS Letters [ ADS | PDF ]
2014 (3/14|15/36)
  • An unbiased study of debris discs around A-type stars with Herschel, Thureau et al, MNRAS [ ADS | PDF ]
  • Towards chemical constraints on hot jupiter migration, Madhusudhan, Amin, & Kennedy, ApJL [ ADS | PDF ]
  • Interpreting the extended emission around three nearby debris disc host stars, Marshall et al, A&A [ ADS ]
  • Do two temperature debris disks have multiple belts? Kennedy & Wyatt, MNRAS [ ADS | PDF ]
  • The Debris Disk of Solar Analogue tau Ceti: Herschel Observations and Dynamical Simulations of the Proposed Multiplanet System, Lawler, di Francesco, Kennedy et al, MNRAS [ ADS | PDF | press ]
  • A Herschel PACS survey of brown dwarfs in IC 2391: Limits on primordial and debris disk fractions, Riaz & Kennedy, MNRAS [ ADS | PDF ]
  • Correlations between the stellar, planetary, and debris components of exoplanet systems observed by Herschel, Marshall et al, A&A [ ADS | PDF ]
  • Spatially Resolved Imaging of the Two-Component eta Crv Debris Disk with Herschel, Duchene et al, ApJ [ ADS | PDF ]
  • Evolution from protoplanetary to debris discs: The transition disc around HD 166191Kennedy et al, MNRAS [ ADS | PDF ]
  • Discovery of the Fomalhaut C debris diskKennedy et al, MNRAS Letters [ ADS | PDF | press | more press ]
  • Alignment in star-debris disc systems seen by Herschel, Greaves, Kennedy, et al, MNRAS Letters [ ADS | PDF ]
  • Herschel Observations of Debris Discs Orbiting Planet-hosting Subgiants, Bonsor, Kennedy, et al, MNRAS [ ADS | PDF ]
  • Imaged sub-stellar companions: not as eccentric as they appear? The effect of an unseen inner mass on derived orbits, Pearce, Wyatt, & Kennedy, MNRAS [ ADS | PDF ]
  • Resolved imaging of the HR 8799 debris disk with Herschel, Matthews, Kennedy, et al, ApJ [ ADS | PDF ]

2013 (2/7|12/22)

  • Star – Planet – Debris Disk Alignment in the HD 82943 system: Is planetary system coplanarity actually the norm?, Kennedy et al, MNRAS [ ADSPDF ]
  • First results of the SONS survey: submillimetre detections of debris discs, Panic et al, MNRAS [ ADS | PDF]
  • The bright end of the exo-Zodi luminosity function: Disk evolution and implications for exo-Earth detectabilityKennedy & Wyatt, MNRAS [ ADS | PDF ]
  • Spatially Resolved Images of Dust Belt(s) Around the Planet-hosting Subgiant Kappa CrB, Bonsor, Kennedy et al, MNRAS [ ADS | PDF | press ]
  • Resolved debris disks around A stars in the Herschel DEBRIS survey, Booth, Kennedy et al, MNRAS [ ADS | PDF ]
  • Millimeter Emission Structure in the first ALMA Image of the AU Mic Debris Disk, MacGregor et al, ApJL [ ADS | PDF ]
  • The Debris Disk around gamma Doradus Resolved with Herschel, Broekhoven-Fiene, Matthews, Kennedy et al, ApJ [ ADS | PDF ]

2012 (3/6|10/15)

  • A DEBRIS Disk Around The Planet Hosting M-star GJ 581 Spatially Resolved with Herschel, Lestrade et al, A&A [ ADS | PDF | press ]
  • Coplanar circumbinary debris disks, Kennedy et al, MNRAS [ ADS | PDF ]
  • Confusion limited surveys: using WISE to quantify the rarity of warm dust around Kepler stars, Kennedy & Wyatt, MNRAS [ ADS | PDF ]
  • Herschel imaging of 61 Vir: implications for the prevalence of debris in low-mass planetary systems, Wyatt, Kennedy et al, MNRAS [ ADS | PDF | press ]
  • A peculiar class of debris disks from Herschel/DUNES – Steep spectral energy distributions, Ertel et al, A&A [ ADS | PDF ]
  • 99 Herculis: Host to a circumbinary polar ring debris disk, Kennedy et al, MNRAS [ ADS | PDF ]

2011 (2/3|7/9)

  • Searching for Saturn’s Dust Swarm: Limits on the size distribution of Irregular Satellites from km to micron sizes, Kennedy et al, MNRAS [ ADS | PDF ]
  • Multi-Wavelength Modelling of the Beta Leo Debris Disc: 1, 2 or 3 planetesimal populations? Churcher et al, MNRAS [ ADS | PDF ]
  • Collisional Evolution of Irregular Satellite Swarms: Detectable Dust around Solar System and Extrasolar PlanetsKennedy & Wyatt, MNRAS [ ADS | PDF ]

2010 (1/2|5/6)

  • Resolving debris discs in the far-infrared: early highlights from the DEBRIS survey, Matthews et al, A&A [ ADS | PDF ]
  • Are Debris Disks Self-Stirred? Kennedy & Wyatt, MNRAS [ ADS | PDF]

2009 (1/1/4)

  • Stellar mass dependent disk dispersal, Kennedy & Kenyon, ApJ [ ADS | PDF ]

2008 (2/2|3/3)

  • Planet formation around stars of various masses: Hot super-Earths, Kennedy & Kenyon, ApJ [ ADS | blog | PDF ]
  • Planet formation around stars of various masses: The snow line and the frequency of gas giants, Kennedy & Kenyon, ApJ [ ADS | blog | PDF ]

2006 (1/1|1/1)

  • Planet formation around low-mass stars: The moving snow line and super-Earths, Kennedy, Kenyon, & Bromley, ApJ [ ADS | blog | PDF | press ]

Conference Proceedings (first author only)

  • Two-temperature debris disks – signposts for directly imaged planets?, Kennedy & Wyatt 2015, IAU314 [ ADS ]
  • The bright end of the exo-Zodi luminosity function: Disk evolution and implications for exo-Earth detectability, Kennedy & Wyatt 2014, IAU299 [ ADS ]
  • Planet formation around M Dwarfs: The moving snow line and super-EarthsKennedy, Kenyon, & Bromley 2007 [ ADS | blog | PDF ]
Observing programmes (as PI)
  • The frontier of rocky planet formation: are low-mass stars super-efficient?,  ALMA Cycle 5, 2017
  • The Fomalhaut C Debris Disk: Key to the famous eccentric ring around A? ALMA Cycle 5, 2017
  • A unique window on circumbinary planet formation at only 45pc, ALMA Cycle 5, 2017
  • Disk structure and warping in the quadruple HD 98800 system, VLT/SPHERE, 2015
  • Grain size and composition in a planet-forming system with transiting dust clumps, VLT/VISIR, 2015
  • Photometric and spectral variability during terrestrial planet formation, VLT/VISIR, 2014
  • K2 Cycles 2 and 3: Transiting planets as a part of whole planetary systems, K2 target proposal, 2014
  • The Origin of Debris Rings: Planets or Gas?, ALMA Cycles 2 & 3, 2014 & 2015
  • The Fomalhaut C Debris Disk and implications for the Fomalhaut system, SCUBA2 Director’s Discretionary Time, 2013
  • Herschel imaging of a candidate warm debris disk, Herschel Director’s Discretionary Time, 2012
  • Debris Disks as a Tracer of Star and Planet Formation in Binaries, Herschel OT2, 2011
  • An Irregular Dust Cloud around Uranus, Herschel OT1, 2010

Selected observing programmes (as Co-I)

  • Pericenter glow and dust production in the debris disk around HR 4796, PI: J. Olofsson, 2017
  • Proto-planetary disc masses at the end of their lifetime, PI: G. Rosotti, 2017
  • SPHERE imaging of nearby super-Earth planet host systems, PI: M. Read, 2017
  • Spin-orbit alignment in debris disks, VLT/GRAVITY, PI: S Kraus, 2016
  • “Where’s the flux?”: Exocomets or Giant Impact?, Spitzer, PI: H. Meng, 2015/2016
  • Imaging Planets in Sco-Cen Double-Belt Debris Disk Systems, VLT/SPHERE, PI: S. Hinkley, 2015
  • Imaging Planets in the Best-Characterized Double-Belt Debris Disk Systems, VLT/SPHERE, PI: E. Matthews, 2015
  • Awakening the giants, DDo51 survey of the bulge, La Silla 2.2m, PI: M. Ness, 2015
  • Giant planets around nearby young stars – a large NaCo L’ imaging survey, VLT/NaCo GTO 2015-
  • Behind Hubble’s blind spot (a.k.a. SHARDDS), VLT/SPHERE, PI: J. Milli, 2015
  • Characterisation of hot circumstellar dust using optical polarisation, HIPPI, PI: J. Marshall, 2015
  • Imaging Planets in the Best-Characterized Double-Belt Debris Disk Systems, VLT/SPHERE, PI: S. Hinkley, 2014
  • LMT/AzTEC millimetre observations of eps Eri’s cold debris disk, LMT, PI: M. Chavez, 2014
  • CO in bright debris disks within 100pc, Nobeyama 45m, PI: L. Matra, 2014
  • Resolving the narrow Kuiper belt analog around epsilon Eridani, ALMA Cycle 2, PI: A. Jordan, 2014
  • What lies outside super-Earth planetary systems?, ALMA Cycle 2, PI: M. Wyatt, 2014
  • Constraining the Inner Disk Edge of the Solar Analog tau Ceti, ALMA Cycle 2, PI: S. Lawler, 2014
  • Testing the correlation between low mass planets and debris disks, HST, PI: P. Kalas, 2014
  • SpiKeS, Spitzer IRAC survey of the Kepler field, Spitzer, PI: M. Werner, 2013
  • Constraining the structure of the Kappa Cr B planetary system, a unique subgiant, orbited by two companions and a debris disc, HST, PI: A. Bonsor, 2013
  • Finding low-mass planets in debris-disk systems: searching for correlations, SOPHIE, PI: E. Di Folco, 2013
  • Small SpiKeS, Spitzer IRAC pilot survey of one Kepler tile, Spitzer, PI: M. Werner, 2012
  • LBTI exo-zodi key science team, PI: M. Wyatt, 2012
  • SONS, SCUBA-2 Legacy survey PI: B. Matthews, 2012
  • Imaging the Birth Ring of the AU Mic Debris Disk, ALMA, PI: D. Wilner, 2011
  • Confirmation and characterisation of two debris disks around low-mass stars, Herschel, PI: J-F Lestrade, 2011
  • Debris Disks around Low-Mass Planet-Bearing Stars, Herschel, PI: G. Bryden, 2011
  • Debris Disks around Planet-Bearing Stars, Herschel, PI: G. Bryden, 2010
  • Search for a correlation between planets and debris discs around retired A stars, Herschel, PI: A. Bonsor, 2010
  • Testing Planetary Dynamics and Evolutionary History in the HR 8799 Planet/Disc System, Herschel, PI: B. Matthews, 2010
  • DEBRIS, PI: B. Matthews & J. Greaves, Herschel Key Programme, 2009


  • Nature
  • NASA Exoplanet Research Program
  • Monthly Notices of the Royal Astronomical Society
  • Astronomy & Astrophysics
  • The Astrophysical Journal
  • Research in Astronomy and Astrophysics
  • James Clerk Maxwell Telescope TAG


  • Warwick lecturer for PX389 Cosmology (2018-)
  • Warwick tutee supervision (2017-)
  • Supervision of PhD students (Ben Yelverton 2016-, Patrick Cronin-Coltsmann 2018-)
  • Occasional substitute lecturer for Mark Wyatt’s Planetary System Dynamics course
  • Co-supervision of Cambridge PhD students (Tim Pearce, Matthew Read, Sebastian Marino, 2013-2017)
  • Supervision of Cambridge summer and part III students (2009-2017)
  • Supervising for Astrophysical Fluid Dynamics (third year course at University of Cambridge, 2013/14/16)
  • Supervising for Mathematical Methods (second your course at University of Cambridge, 2014/15)
  • Graduate student lectures, Nov 2012, IoA [ slides ]

Funding Awarded

  • RAS Undergraduate Bursary for a summer student, April 2015
  • RAS Undergraduate Bursary for a summer student, March 2014
  • RAS Undergraduate Bursary for a summer student, March 2013


  • Comets that orbit other stars, Sheffield Colloquium, Oct 2019
  • Comets that orbit other stars, Harvard Colloquium, Oct 2019
  • A circumbinary protoplanetary disk in a polar configuration, Harvard ITC Lunch, Oct 2019
  • Single, Shallow, & Strange Transits, Warwick, Sept 2019
  • A circumbinary protoplanetary disk in a polar configuration, Cairns, July 2019
  • Comets that orbit other stars, IAP Colloquium, Paris, June 2019 [ video ]
  • Debris disk constraints on planet formation, Invited Review, New Horizons in Planet Formation, Victoria, May 2019
  • Disks and sub-stellar companions, Seminar, Valparaiso, March 2019
  • Disks and sub-stellar companions, Imperial Colloquium, London, January 2019
  • Disk dynamics in multiple systems, CHEXO, September 2018
  • Debris disks, Invited Review, Planet Formation and Evolution, Jena, September 2017
  • Machine learn a dust spectrum, Cosmic Dust, Tokyo, August 2017
  • The exocomet interpretation of KIC 8462852, Mt Stromlo, March 2017
  • Exoplanetary systems, Warwick, October 2016
  • Transiting dust clumps around a Sun-like star, Cambridge, October 2016
  • Exo-Zodi, IoA Colloquium, Cambridge, February 2016
  • Exploding asteroids and fragmented comets, GAIA Alerts, Liverpool, November 2015
  • The exo-Zodi problem, UCL colloquium, 5 October 2015
  • Debris disks: seeing dust, Invited Review, Cosmic Dust, Tokyo, August 2015
  • Warm exo-Zodi from cool exo-Kuiper belts, Pathways II Satellite, July 2015
  • The challenge of the exo-Zodi, EWASS, June 2015
  • A wider view of circumbinary planetary system alignment, EWASS, June 2015
  • The exo-Zodi problem, Exeter colloquium, June 2015
  • Two-temperature debris disks, IAU Symposium 314, Atlanta, May 2015 [ slides ]
  • A wider view of planetary system alignment, UK Exoplanet meeting, Warwick, Apr 2015
  • First results from the LBTI, Cambridge Exoplanets, Jan 2015
  • Exo-Zodi characterisation and origins, Invited talk, MAD Workshop, Santiago, Chile, Nov 2014
  • Planet formation and evolution from debris disks, Invited review, La Cristalera workshop, Madrid, Spain, Sept 2014
  • Disk Modelling results, Invited review, 30 Years of beta Pictoris, Paris, France, Sept 2014 [ slides ]
  • exo-Zodi and exo-Earths, AcrossHR, Cambridge 2014, [ slides ]
  • Theory and Modelling of Debris Disks, Invited review, G. Haro 2014 workshop, INAOE, Mexico
  • Debris disk science with SPICA, SPICA workshop, Leiden, May 2014 [slides ]
  • Debris disks, IPAC, March 2014 [ slides ]
  • The origin of the Fomalhaut stellar and planetary systems, Cambridge Exoplanet group, Jan 2014
  • exo-Zodi and exo-Earths, IAU Symposium 299, Victoria, June 2013 [ slides ]
  • Debris disks and planets, and vice versa, IoA, Cambridge, Feb 2013 [ slides ]
  • Debris disks and their relation to planets, UNSW, Sydney, Dec 2012
  • Debris disks and their relation to planets, Mt Stromlo, Australian Exoplanet Workshop, Dec 2012 [ slides ]
  • Debris disks and their relation to planets, Mt Stromlo, Australian National University, Dec 2012
  • Debris disks and their relation to planets, CAR, Uni of Hertfordshire, Nov 2012 [ slides ]
  • Dust from Saturn’s Irregular Satellites, UK NAM, Mar 2011 [ pdf ]
  • Irregular Satellite Swarms, Mt Stromlo, Feb 2011 [ pdf ]
  • Evolution of Irregular Satellites, Cambridge DAMTP, Feb 2011
  • Herschel DEBRIS Survey, RAS Early Impact of Herschel meeting, January 2011 [ pdf ]
  • Theory of Disk Dispersal around M-Dwarfs, Invited review, August 2010, Cool Stars Splinter on M-Dwarf Planet Formation [ keynote | pdf ]
  • IoA Theory Grant talks, August 2010
  • IoA Star and Planet Formation group, March 2010
  • INI Dynamics of Disks and Planets Final Workshop, Dec 2009
  • IoA Theory Grant talks, Nov 2009
  • Final talk at RSAA [ slides (main) (side) | blog ]
  • Super-Earth talk at ASA 2008 [ slides | blog ]
  • Mid-term review at RSAA [ slides ]
  • Super-earth talk at the Fifth Stromlo Symposium [ slides ]


  • exo-Zodi and prospects for exo-Earth detection at PPVI, 2013 [ poster ]
  • A Circumbinary Polar-ring Debris Disk at Herschel’s View of Star and Planet Formation, 2012 [ poster ]
  • A Circumbinary Polar-ring Debris Disk at Signposts of Planet Formation Conference, 2011 [ poster ]
  • Are debris disks self-stirred? posters at Newton Institute workshops in Cambridge and Edinburgh late 2009 [ poster ]
  • Gas giant frequency poster at ASA 2008 [ poster ]
  • Gas giant frequency poster at Origins of Solar Systems Gordon Conference, 2007 [ poster ]
  • Super-earth poster at the Astronomical Society of Australia Annual Meeting, 2006 [ poster ]

Conference/meeting involvement

  • Co-organiser, Lorentz Center Rocks, Rings, and Rubble workshop, Leiden, 2016
  • Session Chair, Resolving planet formation in the era of ALMA and extreme AO, Santiago, 2016
  • Session chair, Cosmic Dust, Tokyo, 2015
  • LOC, Characterizing Planetary Systems Across the HR Diagram, Cambridge, 2014
  • OC, Stromlo Student Seminars, Australian National University, 2006
  • OC, Harley Wood Winter School, Bateman’s Bay, Australia, 2006



  • Some thoughts on how to create your own space in your research field + tips for fellowship applications. Written for this fellowship event.

My PhD involved thinking about how planet formation depends on the star the planets form around, and what we might learn as more planets orbiting a range of different stars are discovered. I worked with Scott Kenyon of Smithsonian Astrophysical Observatory, part of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA in the USA. This link has a copy of my thesis as submitted (no corrections), though the body is just the first four papers listed here outlined a bit more in blog posts, links below.

  • Stellar mass dependent disk dispersal in the Astrophysical Journal in April 2009 (ApJ v695 p1210) [ ADS ]
  • Planet formation around stars of various masses: Hot super-Earths in the Astrophysical Journal in August 2008 (ApJ v682 p1264) [ ADS | blog entry ]
  • Planet formation around stars of various masses: The snow line and the frequency of gas giants appeared in the Astrophysical Journal in January 2008 (ApJ v673 p502) [ ADS | blog entry ]
  • Planet formation around M Dwarfs: The moving snow line and super-Earths appeared in Astrophysics and Space Science in August 2007 (Ap&SS v311 p9) [ ADS | blog entry ] (this paper is basically a clearer version of the one below)
  • Planet formation around low-mass stars: The moving snow line and super-Earths appeared in the Astrophysical Journal Letters in October 2006 (ApJL v650 p139) [ ADS | blog entry ]

April fools relativity

I think April the first is probably a bad day to publish a serious paper. Anyone looking at astro-ph today will be busy enjoying this paper, rather than looking at your paper. Reference number 6 in that paper is also worth a look…(0)


So I’ve made a half-assed resolution to try and take a nice photo every day. Today I was working on the resonances set up when planets migrate and shepherd others, and stole this image out of the excellent book ‘Solar System Dynamics.’

mean motion resonances

Paper accepted!

After four revisions and seven months of extra (part time) work, my second planet formation paper has been accepted, finally! To sum up the paper in a few sentences…

We think that the likelihood of a star forming at least one gas giant planet increases with the mass of the star. There are two reasons for this: Firstly, the mass of the disks surrounding these stars seems to increase with the mass of the star, and therefore so do the masses of protoplanets that form. Secondly, there is probably a threshold protoplanet mass at which gas accretion occurs and giant planets form. Higher mass stars can therefore form protoplanets above the gas giant forming threshold (and therefore gas giants) more easily, because on average they have more material to do so.

The preprint can be found here.

Planet formation around stars of various masses: The snow line and the frequency of gas giants

This paper was just accepted to the Astrophysical Journal. It considers a simple disk and snow line model, and uses this to predict the likelihood of stars of different masses harbouring gas giants. We think gas giant frequency increases with stellar mass, which is consistent with observations at present.

In summary, observations indicate that disk mass changes roughly with stellar mass, with a wide distribution of masses at a given stellar mass. Therefore more massive stars on average have more material available for planet formation. In addition, there appears to be a threshold protoplanet mass for forming gas giants of about ten Earth masses. Around more massive stars, a higher fraction of the disks can form protoplanets greater than ten Earth masses, so these stars are more likely to form gas giants.

Recent observations by John Johnson indicate a trend of increasing planet frequency with stellar mass, as our paper predicts. Future observations will improve statistics to solidify this result. In the more distant future, planet discoveries will find how processes like migration and scattering have influenced the distribution of planets we can see now.

The paper can be found through the NASA Astrophysics Data System. For more information on my PhD have a look at the main PhD page.

Planet formation around M Dwarfs: The moving snow line and super-Earths

This paper, just accepted to the 5SS conference proceedings, is similar to the ApJ letter here. It uses a smaller increase in surface density at the snow line, based on modern Solar abundance figures for oxygen. A brief comment on type I migration has also been added.

The paper can be found through the NASA Astrophysics Data System. For more information on my PhD have a look at the main PhD page.

A typical day at the CfA…

So I imagine people wondering, what is a typical day at Harvard-CfA like for Grant? Here is my ‘typical’ day…

So after wandering down to school through a crisp morning with patches of snow, I find there are some people I know passing through. I go and meet Anna who lives in Texas, and also see Martin and Ken from Australia. I then go to a talk by a guy from Caltech who does cool theoretical planet work, and later to a talk by another guy who does cool observational planet work. Finally I go out to dinner with more people who do things I’m interested in. And the best thing: dinner was free, thanks ITC!

Meeting three or four people in a day who do research directly related to what I do is very cool, and hasn’t even come close to happening in two years in Australia.

Of course some days I just sit at my desk at play with my computer…

Comet McNaught

A comet discovered by Rob McNaught at Siding Spring Observatory is nearing the sun in about a week. It will be at its brightest around the 15th Jan, when it will appear as in the image below (though a little later when the sun has set!). More information can be found on this page.

software image of comet location

Mt Stromlo on the rebuild III

Three years later the burnt out domes are getting repainted, they look very white!

very white indeed

Mt Stromlo on the rebuild II

Work is well underway on rebuilding the Commonwealth Solar Observatory (CSO), where people here used to have bbq’s every second week. The painted silver domes have been unveiled recently, and look very shiny!


Stromlo Student Seminars

The 4th annual Stromlo Student Seminars were held Thursday and Friday last week, and were a resounding success.

Thanks to all those who made the effort to come from elsewhere and contribute to a great couple of days of student science.

See this post for notes on the social side of things…

Mt Stromlo on the rebuild!

We have recently had our new Advanced Instrumentation and Technology Center (AITC) opened. I’ve been watching it come together from my office window, and put together a little time lapse animation of photos taken with my phone.

Have a look at the animation here (19Mb).

my room's view

more press release madness

On Monday an ANU press release went out and all hell broke loose. Well I did three radio interviews and made it onto PM, Radio National’s evening news which is quite an achievement aparrently.

My 15 minutes of fame is now over. There are a bunch of links to how my story got pasted over the internet on my PhD publications page.

It even made it into Nature’s research highlights!

snowy super-Earth press release

The Harvard-Smithsonian Center for Astrophysics (CfA) have put out a press release relating to our recently accepted ‘super-Earth’ paper (astro-ph/0609140, ApJL). It’s also on Universe today which is very cool.

This blog has rewritten what happens and makes some good points about what a super-Earth really is, and about disk masses which do have a wide range. Our model uses a disk that is reasonably massive, for this and dynamical reasons we don’t expect planets much larger than ~5 Earth masses to form in this manner.

There are even a few sites I’ve never heard of that have the release: Spaceflight Now, and Space Daily.

It seems a tad unfortunate that today a light plane crashed into an apartment building in Manhattan. It’s probably best when press releases go out on ‘no news’ days… (because this is obviously front page news)

In case you’re wondering, below is an artists image of a super-Earth, an icy planet several times further away from a dim ‘red dwarf’ star than the Earth is from the Sun.

it really does look like this

Planet formation around low-mass stars: The moving snow line and super-Earths

Our first paper is about how the snow-line in a protoplanetary disk can move due to evolution of the central star, and how it helps the formation of super-Earth mass planets around M Dwarfs. Kennedy, Kenyon & Bromley (2006) uses a simple disk evolution model, with which we are starting to link formation of planets with that of their parent stars.

As a low-mass red dwarf is born it contracts to its main sequence size over hundreds of millions of years. This contraction limits the radiating area of the star, and so it becomes fainter, and the surrounding disk in which planets form becomes cooler.

The cooling of the star means that the distance where ices condense (known as the ‘snow line’) moves inward. In the same way that it is easier to build a snowman above the snow line on a mountain, the presence of ices in the planet forming disk makes it easier to build planets. These planets can be several times larger than our Earth, and are largely made up of ice, roughly similar in structure to Neptune.

The paper had an associated press release, and subsequently generated a bunch of media attention

ANU Press release | CfA Press Release | Uni of Utah press release | Universe Today | Spaceflight Now | Space Daily | Centauri Dreams | PhysOrg | Unexplained Mysteries | Astrobiology Magazine | SciFi Source Book | AstroFind.net | Science Alert | ABC Radio National | ABC Canberra | Nature

The paper can be found through the NASA Astrophysics Data System. For more information on my PhD have a look at the main PhD page.

cats on Mars?

I thought the Astronomy Picture of the Day today looked like the face of a cat when it turned up in my google desktop plugin.


Upon opening the real APOD page it turned out to be ‘the unusual stone mesas of the Cydonia region on Mars’.

Oh well


This is the last thing I’ll add while I’m at Parkes, I promise.

I got an excellent tour of the Dish this morning. We climbed on the edge of the dish and took a ride up to zenith, and then climbed up to the focus cabin. The view from up there is spectacular. I’ve never taken so many photos

the dish

The Dish!

Oh yeah I’m at the dish, in Parkes NSW. The telescope of the movie is every bit as impressive as it was made to look in the movie. I have proven that by taking amazing photos of it.

Since it’s a radio telescope it can work during the day, which unfortunately we aren’t taking advantage of. Our runs are from 5pm to 8am which leaves one feeling a little tired on occasion.

Nevertheless it has been totally worth the paltry 4 hour drive here from Canberra. Thanks Ken!



I’ve spent the last three nights at SSO on the 40″ telescope with Daniel Bayliss looking at the galactic plane. The surrounding national park is beautiful, and there are plenty of walks one can do to pass the daytime hours not spent sleeping, see this entry for the one I did. The trip was a a great learning experience. I now feel the urge to dream up a few observational projects of my own..


if you’ve seen the news about there being a lot less comets these days and wondered what all the fuss was about, you can go have a look at Paul’s web page.

my own work will be along before xmas (or else!)