INNATE Investigating the nature and origins of exoplanets in the Neptunian desert
Lead Research Organisation:
University of Warwick
Department Name: Physics
Abstract
Our knowledge of exoplanets has undergone a step change since the discovery of 51 Peg b 25 years ago. Planets are now commonplace, with most stars found to be hosting planetary systems. In the set of over 4300 planets known, trends and gaps in the distribution are seen with respect to planet size, composition and host star properties, arising from the formation and evolution processes which sculpt these worlds.
A striking signature in the planet distribution is the 'Neptunian desert', a dearth of Neptune-like planets orbiting close to their host stars. Planets which arrive so close to their stars are evaporated away, or are disrupted entirely by the strong gravitational forces of the star. Yet, recently a number of planets have been discovered inside the desert, surprising expectations and highlighting a gap in our understanding. The origin of these hot Neptunes is unknown, and they present a unique opportunity to study the extreme outcomes of planet formation. Such outliers of the normal processes allow us to benchmark planetary formation theories, with many of the typical degeneracies stripped away.
With this proposal, we will combine photometric and spectroscopic observations from TESS, NGTS, CORALIE, HARPS and Gaia to carry out an ambitious and comprehensive research program investigating the nature and origins of planets in the desert. (1) We will uncover the unbiased demographic properties of the in-desert planets, finding the distributions of planet mass, radius, density, internal structure and host star properties. (2) We will establish the dynamical context of these systems by determining the presence of outer companions and local density of stars (3) We will connect the measured demographics, dynamics and internal structure to wider formation and evolution theory. The combined results will transform our understanding not only of the in-desert planets but of the wider formation, structure and evolution of planetary systems.
A striking signature in the planet distribution is the 'Neptunian desert', a dearth of Neptune-like planets orbiting close to their host stars. Planets which arrive so close to their stars are evaporated away, or are disrupted entirely by the strong gravitational forces of the star. Yet, recently a number of planets have been discovered inside the desert, surprising expectations and highlighting a gap in our understanding. The origin of these hot Neptunes is unknown, and they present a unique opportunity to study the extreme outcomes of planet formation. Such outliers of the normal processes allow us to benchmark planetary formation theories, with many of the typical degeneracies stripped away.
With this proposal, we will combine photometric and spectroscopic observations from TESS, NGTS, CORALIE, HARPS and Gaia to carry out an ambitious and comprehensive research program investigating the nature and origins of planets in the desert. (1) We will uncover the unbiased demographic properties of the in-desert planets, finding the distributions of planet mass, radius, density, internal structure and host star properties. (2) We will establish the dynamical context of these systems by determining the presence of outer companions and local density of stars (3) We will connect the measured demographics, dynamics and internal structure to wider formation and evolution theory. The combined results will transform our understanding not only of the in-desert planets but of the wider formation, structure and evolution of planetary systems.
People |
ORCID iD |
| David John Armstrong (Principal Investigator) |
Publications
Osborn A
(2023)
TOI-332 b: a super dense Neptune found deep within the Neptunian desert
in Monthly Notices of the Royal Astronomical Society
Luque R
(2023)
A resonant sextuplet of sub-Neptunes transiting the bright star HD 110067.
in Nature
Nagel E
(2023)
The CARMENES search for exoplanets around M dwarfs Telluric absorption corrected high S/N optical and near-infrared template spectra of 382 M dwarf stars
in Astronomy & Astrophysics
Frame G.
(2023)
TOI-2498 b: a hot bloated super-Neptune within the Neptune desert
in Monthly Notices of the Royal Astronomical Society
Psaridi A
(2023)
Three Saturn-mass planets transiting F-type stars revealed with TESS and HARPS TOI-615b, TOI-622b, and TOI-2641b
in Astronomy & Astrophysics
Hawthorn F
(2023)
TOI-908: a planet at the edge of the Neptune desert transiting a G-type star
in Monthly Notices of the Royal Astronomical Society
Barros S
(2023)
The young mini-Neptune HD 207496b that is either a naked core or on the verge of becoming one
in Astronomy & Astrophysics
Sha L
(2023)
TESS spots a mini-neptune interior to a hot saturn in the TOI-2000 system
in Monthly Notices of the Royal Astronomical Society
Armstrong D
(2023)
Discovery and characterization of two Neptune-mass planets orbiting HD 212729 with TESS
in Monthly Notices of the Royal Astronomical Society
Hadjigeorghiou A
(2024)
The positional probability and true host star identification of TESS exoplanet candidates
in Monthly Notices of the Royal Astronomical Society
Bouchy F
(2024)
NGTS discovery of a highly inflated Saturn-mass planet and a highly irradiated hot Jupiter NGTS-26 b and NGTS-27 b
in Astronomy & Astrophysics
Dash S
(2024)
Constraints on atmospheric water abundance and cloud deck pressure in the warm Neptune GJ 3470 b via CARMENES transmission spectroscopy
in Monthly Notices of the Royal Astronomical Society
Doyle, L
(2024)
The TESS SPOC FFI target sample explored with gaia
in MNRAS
Panwar V
(2024)
The mystery of water in the atmosphere of t Boötis b continues: Insights from revisiting archival CRIRES observations
in Monthly Notices of the Royal Astronomical Society
Cui K
(2024)
Identifying Light-curve Signals with a Deep-learning-based Object Detection Algorithm. II. A General Light-curve Classification Framework
in The Astrophysical Journal Supplement Series
Castro-González A
(2024)
TOI-5005 b: A super-Neptune in the savanna near the ridge
in Astronomy & Astrophysics
Pritchard M
(2024)
Sandwiched planet formation: restricting the mass of a middle planet
in Monthly Notices of the Royal Astronomical Society
Gill S
(2024)
TOI-2447 b / NGTS-29 b: a 69-day Saturn around a Solar analogue
in Monthly Notices of the Royal Astronomical Society
Suárez Mascareño A
(2024)
TESS and ESPRESSO discover a super-Earth and a mini-Neptune orbiting the K-dwarf TOI-238
in Astronomy & Astrophysics
Cortés-Contreras M
(2024)
CARMENES input catalogue of M dwarfs VIII. Kinematics in the solar neighbourhood
in Astronomy & Astrophysics
Nabbie E
(2024)
Surviving in the Hot-Neptune Desert: The Discovery of the Ultrahot Neptune TOI-3261b
in The Astronomical Journal
Hacker A
(2024)
TOI-2374 b and TOI-3071 b: two metal-rich sub-Saturns well within the Neptunian desert
in Monthly Notices of the Royal Astronomical Society
Freckelton A
(2024)
BEBOP V. Homogeneous stellar analysis of potential circumbinary planet hosts
in Monthly Notices of the Royal Astronomical Society
Castro-González A
(2024)
Mapping the exo-Neptunian landscape A ridge between the desert and savanna
in Astronomy & Astrophysics
Lillo-Box J
(2024)
K2-399 b is not a planet The Saturn that wandered through the Neptune desert is actually a hierarchical eclipsing binary
in Astronomy & Astrophysics
Barnes R
(2025)
History and Habitability of the LP 890-9 Planetary System
in The Planetary Science Journal
Bonfanti A
(2025)
Radii, masses, and transit-timing variations of the three-planet system orbiting the naked-eye star TOI-396
in Astronomy & Astrophysics
Grieves N
(2025)
Discovery of a cold giant planet and mass measurement of a hot super-Earth in the multi-planetary system WASP-132
in Astronomy & Astrophysics
| Description | A key homogenous sample of target stars has been defined and published. Connections between desert planets and hot Jupiters have been identified in nearby companion star fractions (objective 2). Multiple desert and near-desert planets have been surveyed with radial velocities and characterised, building a population to be investigated later in the grant timeframe. A new demographic feature, the Neptunian ridge, has been identified and published. |
| Exploitation Route | New observing proposals, and as observational drivers of theoretical investigations. |
| Sectors | Other |
| Description | ESO OPC Expert Panels |
| Geographic Reach | Europe |
| Policy Influence Type | Participation in a guidance/advisory committee |
| Description | Warwick District Council Member |
| Geographic Reach | Local/Municipal/Regional |
| Policy Influence Type | Participation in a guidance/advisory committee |
| Impact | Specifics are in places confidential, however external organisations to the Council have reported that they have made their development plans more environmentally friendly as a result of a Green party led administration. The Council itself has approved a budget involving an additional 5M for decarbonisation, alongside numerous smaller changes and plans in development. |
| Title | TESS SPOC FFI Main Sequence Target Sample |
| Description | VizieR online Data Catalogue associated with article published in journal Monthly Notices of the Royal Astronomical Society with title ' The TESS SPOC FFI target sample explored with Gaia.' (bibcode: 2024MNRAS.529.1802D) |
| Type Of Material | Database/Collection of data |
| Year Produced | 2024 |
| Provided To Others? | Yes |
| Impact | Target sample defined for several in progress demographic statistical studies. |
| URL | https://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/529/1802 |
| Title | TOI-615, TOI-622, TOI-2641 RVs + ground phot. |
| Description | VizieR online Data Catalogue associated with article published in journal Astronomy and Astrophysics with title ' Three Saturn-mass planets transiting F-type stars revealed with TESS and HARPS. TOI-615b, TOI-622b, and TOI-2641b.' (bibcode: 2023A&A...675A..39P) |
| Type Of Material | Database/Collection of data |
| Year Produced | 2023 |
| Provided To Others? | Yes |
| URL | https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/675/A39 |
| Description | NOMADS Collaboration |
| Organisation | Laboratoire d'Astrophysique de Marseile |
| Country | France |
| Sector | Academic/University |
| PI Contribution | Armstrong is the PI of this collaboration. The group of >30 academics and students works to characterise planets in the Neptunian desert, with the long term aim of revealing the demographics and statistical properties of the desert planet population. Our research team's contribution is in acquiring telescope time on the HARPS spectrograph, coordinating observations, targets, and the wider consortium, and providing strategic direction to the project. |
| Collaborator Contribution | Different collaborators have different inputs. These include stellar characterisation, planetary internal structure modelling, false positive simulations, telescope observing, and photometric and spectroscopic followup of candidates. |
| Impact | Publications in progress. |
| Start Year | 2021 |
| Description | NOMADS Collaboration |
| Organisation | National University of San Martin |
| Country | Argentina |
| Sector | Academic/University |
| PI Contribution | Armstrong is the PI of this collaboration. The group of >30 academics and students works to characterise planets in the Neptunian desert, with the long term aim of revealing the demographics and statistical properties of the desert planet population. Our research team's contribution is in acquiring telescope time on the HARPS spectrograph, coordinating observations, targets, and the wider consortium, and providing strategic direction to the project. |
| Collaborator Contribution | Different collaborators have different inputs. These include stellar characterisation, planetary internal structure modelling, false positive simulations, telescope observing, and photometric and spectroscopic followup of candidates. |
| Impact | Publications in progress. |
| Start Year | 2021 |
| Description | NOMADS Collaboration |
| Organisation | University of Geneva |
| Department | Geneva Observatory |
| Country | Switzerland |
| Sector | Academic/University |
| PI Contribution | Armstrong is the PI of this collaboration. The group of >30 academics and students works to characterise planets in the Neptunian desert, with the long term aim of revealing the demographics and statistical properties of the desert planet population. Our research team's contribution is in acquiring telescope time on the HARPS spectrograph, coordinating observations, targets, and the wider consortium, and providing strategic direction to the project. |
| Collaborator Contribution | Different collaborators have different inputs. These include stellar characterisation, planetary internal structure modelling, false positive simulations, telescope observing, and photometric and spectroscopic followup of candidates. |
| Impact | Publications in progress. |
| Start Year | 2021 |
| Description | NOMADS Collaboration |
| Organisation | University of Porto |
| Country | Portugal |
| Sector | Academic/University |
| PI Contribution | Armstrong is the PI of this collaboration. The group of >30 academics and students works to characterise planets in the Neptunian desert, with the long term aim of revealing the demographics and statistical properties of the desert planet population. Our research team's contribution is in acquiring telescope time on the HARPS spectrograph, coordinating observations, targets, and the wider consortium, and providing strategic direction to the project. |
| Collaborator Contribution | Different collaborators have different inputs. These include stellar characterisation, planetary internal structure modelling, false positive simulations, telescope observing, and photometric and spectroscopic followup of candidates. |
| Impact | Publications in progress. |
| Start Year | 2021 |
| Description | TESS Follow-up Observing Program (TFOP) |
| Organisation | Massachusetts Institute of Technology |
| Country | United States |
| Sector | Academic/University |
| PI Contribution | I am the PI of a HARPS spectrograph program which follows up candidate TESS planets. The results of the follow-up are coordinated with the TFOP collaboration to avoid duplicating observations and maximise the efficiency of the TESS satellite and my HARPS program. |
| Collaborator Contribution | MIT is the site of the TESS science office where TESS data is initially processed. TFOP is actually a wider collaboration involving a large number of institutes around the world, and coordinates follow-up activities to TESS planets. THE main team at MIT contribute to my research by releasing early lists of TESS planet candidates which allows me to save significant time in moving to planet characterisation. The amount of in-kind funding is an estimate but the time saved is substantial, and hence the in-kind funding is likely underestimated if anything. |
| Impact | Publications: Several publications as detailed in the publications section. |
| Start Year | 2019 |
| Title | DEEP-LC lightcurve classification tool |
| Description | Software tool to classify variability in astrophysical lightcurves |
| Type Of Technology | Software |
| Year Produced | 2024 |
| Open Source License? | Yes |
| Impact | - |
| URL | https://github.com/ckm3/Deep-LC |
| Title | TESS Positional Probability Tool |
| Description | Publicly released Python code for determining the true source of exoplanet transit-like events in TESS photometry. |
| Type Of Technology | Software |
| Year Produced | 2023 |
| Impact | Use of the tool is ongoing and interest in utilising it and developing it further has been expressed by researchers at MIT and in Madrid. |
| URL | https://github.com/ahadjigeorghiou/TESSPositionalProbability |
| Title | TESS lightcurve viewer |
| Description | Webtool that allows easy viewing of TESS lightcurve data (https://tess.cuikaiming.com/) |
| Type Of Technology | Webtool/Application |
| Year Produced | 2024 |
| Impact | - |
| URL | https://tess.cuikaiming.com/ |
| Title | TESS stellar and planet distribution generator |
| Description | SOftware that allows simulation of lightcurves for planets, eclipsing binaries and other astrophysical scenarios for testing, training ML models, and general use. |
| Type Of Technology | Software |
| Year Produced | 2025 |
| Open Source License? | Yes |
| Impact | Use in ongoing research. |
| URL | https://github.com/ckm3/pastisML-tess |
| Title | raccoon: Radial velocities and Activity indicators from Cross-COrrelatiON with masks |
| Description | Author: M Lafarga. raccoon implements the cross-correlation function (CCF) method. It builds weighted binary masks from a stellar spectrum template, computes the CCF of stellar spectra with a mask, and derives radial velocities (RVs) and activity indicators from the CCF. raccoon is mainly implemented in Python 3; it also uses some Fortran subroutines that are called from Python. Bibcode: 2024ascl.soft05023L |
| Type Of Technology | Software |
| Year Produced | 2024 |
| Open Source License? | Yes |
| Impact | Described in: 2023A&A...670A.139R Used in: 2020A&A...636A..36L |
| URL | https://github.com/mlafarga/raccoon |
| Description | Astronomy on Tap |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Public/other audiences |
| Results and Impact | Organised 2 events for Astronomy on Tap Coventry, which consisted on a couple of talks by astronomy researchers and quizzes on a non-traditional setting like a pub. Attendance ~50 people. |
| Year(s) Of Engagement Activity | 2023,2024 |
| Description | Chatea con una astro´noma 2024 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Schools |
| Results and Impact | Online event organised by the Spanish Astronomy Society. Chatted with ~20 high school students in Spain about astronomy and life as a researcher. |
| Year(s) Of Engagement Activity | 2024 |
| Description | Coding with Sophie workshop |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Schools |
| Results and Impact | Coding lessons with an astronomy background to primary school students (~50 students). |
| Year(s) Of Engagement Activity | 2023,2024 |
| URL | https://codingwithsophie.warwick.ac.uk/ |
| Description | Festivals on campus promoting STEM subjects including planetarium shows |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Public/other audiences |
| Results and Impact | 2 festivals on campus promoting STEM subjects including 16 planetarium shows to the general public with audiences totalling 500+ |
| Year(s) Of Engagement Activity | 2023,2024 |
| Description | Interview for national press |
| Form Of Engagement Activity | A press release, press conference or response to a media enquiry/interview |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Media (as a channel to the public) |
| Results and Impact | BBC interview about article "A resonant sextuplet of sub-Neptunes transiting the bright star HD 110067" |
| Year(s) Of Engagement Activity | 2023 |
| URL | https://www.bbc.co.uk/news/science-environment-67488931 |
| Description | Observatory Tours at Marsh Observatory |
| Form Of Engagement Activity | Participation in an open day or visit at my research institution |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Third sector organisations |
| Results and Impact | >100 children aged 8-14 years visited the campus observatory for tours. These were from Squirrels, Beavers, Cubs and Scout groups, as well as the general public. |
| Year(s) Of Engagement Activity | 2023,2024,2025 |
| Description | Press release on 2025 planet parade |
| Form Of Engagement Activity | A press release, press conference or response to a media enquiry/interview |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Media (as a channel to the public) |
| Results and Impact | Press release and quotations issued around the planet parade - multiple solar system planets visible in the sky through early 2025. Interviews given with BBC, AFP (Association France Presse). Quote picked up by mutiple national media sources including national newspapers. Members of the public noticed this and contacted me. |
| Year(s) Of Engagement Activity | 2025 |
| Description | Space Camps running exoplanet workshop for Year 5 |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Schools |
| Results and Impact | Space Camps running exoplanet workshop for Year 5 in two schools in Sutton Coldfield for 120 students. |
| Year(s) Of Engagement Activity | 2023,2024 |
| Description | Visit to rural school in Shropshire |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Schools |
| Results and Impact | Visit to rural school in Shropshire for running workshops for Years 3 - 6. Also visited Reception, Years1 and Year2. Total of 90 students. |
| Year(s) Of Engagement Activity | 2024 |