Irradiated atmospheres of brown dwarfs: providing an insight into exoplanet atmospheres
Lead Research Organisation:
University of Leicester
Department Name: Physics and Astronomy
Abstract
I will use this fellowship to explore, and ultimately understand how irradiation affects the atmospheres of brown dwarfs.
Brown dwarfs are the missing link between stars and exoplanets. They are the size of Jupiter but may be up to 70 times as massive. However, unlike exoplanets, they form like stars, from the collapse of a massive gas cloud. The first brown dwarf was imaged in 1995, the very same year as the first exoplanet detection, and to date over 1200 have been discovered. Our closest brown dwarf is the Sun's fourth nearest neighbour! Young brown dwarfs have very similar atmospheres to directly imaged exoplanets, and brown dwarfs are often used to tell us what we would expect to see in an exoplanet atmosphere. However, most exoplanets are orbiting very close to their host star, which is much brighter, making it very difficult to determine what is in its atmosphere.
I will study brown dwarfs that are in very close orbits with a hot companion. In these systems, the brown dwarf may complete an orbit in as little as 2 hours. These systems are tidally locked, meaning that the same side of the brown dwarf continually faces the companion. I discovered that this hot side can be up to 500 degrees hotter than the dark side of the brown dwarf, causing winds that transport energy from the hot side to the cold side. It is clear that heating a brown dwarf or exoplanet drastically alters its atmosphere, as the irradiation splits up and creates new molecules.
I will observe these binaries using 4m and 8m telescopes around the world. My observations will monitor the brown dwarf as it orbits its companion, to understand how much brighter the brown dwarf gets as its heated side moves into view. By observing in different wavelengths, I will be able to see how the different layers in the atmosphere respond to the heating. I will also take spectra of the brown dwarf at different points in its orbit. The new James Webb Space Telescope, launched in 2018 is an ideal facility for this work. I will use these spectra to determine what the atmosphere is made of, and which molecules are being created by the irradiation. The creation of new molecules depends very much on how hot the brown dwarf's companion is, so studying as many systems as possible, with host stars of different temperatures is very important.
There are, however, very few of these systems known to date, so as well as studying the known systems, I will discover new ones using a new survey for discovering exoplanets, NGTS, and also wide field surveys. These surveys image the sky at many wavelengths, and by combining data from them I will be able to identify new binaries. I will then obtain more observations of them with world leading telescopes, to measure the masses, and the orbital timescale.
Finally I will work with my collaborators to create models of these systems. These models will be used to explain the processes occurring in the brown dwarf atmosphere as it is heated and will also be used to explain what happens in heated exoplanet atmospheres.
Brown dwarfs are the missing link between stars and exoplanets. They are the size of Jupiter but may be up to 70 times as massive. However, unlike exoplanets, they form like stars, from the collapse of a massive gas cloud. The first brown dwarf was imaged in 1995, the very same year as the first exoplanet detection, and to date over 1200 have been discovered. Our closest brown dwarf is the Sun's fourth nearest neighbour! Young brown dwarfs have very similar atmospheres to directly imaged exoplanets, and brown dwarfs are often used to tell us what we would expect to see in an exoplanet atmosphere. However, most exoplanets are orbiting very close to their host star, which is much brighter, making it very difficult to determine what is in its atmosphere.
I will study brown dwarfs that are in very close orbits with a hot companion. In these systems, the brown dwarf may complete an orbit in as little as 2 hours. These systems are tidally locked, meaning that the same side of the brown dwarf continually faces the companion. I discovered that this hot side can be up to 500 degrees hotter than the dark side of the brown dwarf, causing winds that transport energy from the hot side to the cold side. It is clear that heating a brown dwarf or exoplanet drastically alters its atmosphere, as the irradiation splits up and creates new molecules.
I will observe these binaries using 4m and 8m telescopes around the world. My observations will monitor the brown dwarf as it orbits its companion, to understand how much brighter the brown dwarf gets as its heated side moves into view. By observing in different wavelengths, I will be able to see how the different layers in the atmosphere respond to the heating. I will also take spectra of the brown dwarf at different points in its orbit. The new James Webb Space Telescope, launched in 2018 is an ideal facility for this work. I will use these spectra to determine what the atmosphere is made of, and which molecules are being created by the irradiation. The creation of new molecules depends very much on how hot the brown dwarf's companion is, so studying as many systems as possible, with host stars of different temperatures is very important.
There are, however, very few of these systems known to date, so as well as studying the known systems, I will discover new ones using a new survey for discovering exoplanets, NGTS, and also wide field surveys. These surveys image the sky at many wavelengths, and by combining data from them I will be able to identify new binaries. I will then obtain more observations of them with world leading telescopes, to measure the masses, and the orbital timescale.
Finally I will work with my collaborators to create models of these systems. These models will be used to explain the processes occurring in the brown dwarf atmosphere as it is heated and will also be used to explain what happens in heated exoplanet atmospheres.
People |
ORCID iD |
Sarah Casewell (Principal Investigator / Fellow) |
Publications
Jenkins J
(2020)
An ultrahot Neptune in the Neptune desert
in Nature Astronomy
Jenkins James S.
(2020)
An ultrahot Neptune in the Neptune desert
in Nature Astronomy
JWST Transiting Exoplanet Community Early Release Science Team
(2023)
Identification of carbon dioxide in an exoplanet atmosphere.
in Nature
Kaye L
(2022)
Transit timings variations in the three-planet system: TOI-270
in Monthly Notices of the Royal Astronomical Society
Kiman R
(2022)
wdwarfdate: A Python Package to Derive Bayesian Ages of White Dwarfs
in The Astronomical Journal
Kirkpatrick J
(2021)
The Enigmatic Brown Dwarf WISEA J153429.75-104303.3 (a.k.a. "The Accident")
in The Astrophysical Journal Letters
Kiwy F
(2022)
Discovery of 34 Low-mass Comoving Systems Using NOIRLab Source Catalog DR2
in The Astronomical Journal
Kiwy F.
(2022)
VizieR Online Data Catalog: 34 Low-mass comoving systems astrometry using NSC DR2 (Kiwy+, 2022)
in VizieR Online Data Catalog
Kota T
(2022)
Discovery of 16 New Members of the Solar Neighborhood Using Proper Motions from CatWISE2020
in The Astronomical Journal
Lee E
(2020)
Simplified 3D GCM modelling of the irradiated brown dwarf WD 0137-349B
in Monthly Notices of the Royal Astronomical Society
Description | Collaboration with Thomas Beatty at University of Wisconsin, Madison. |
Organisation | University of Wisconsin-Madison |
Country | United States |
Sector | Academic/University |
PI Contribution | Royal society travel grant to the value of £6000 to enable closer collaboration between the teams. |
Collaborator Contribution | Knowledge of NIRSPC on the JWST |
Impact | 2 JWST Proposals with the applicant as PI. |
Start Year | 2022 |
Description | BBC interview on local radio |
Form Of Engagement Activity | A press release, press conference or response to a media enquiry/interview |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Public/other audiences |
Results and Impact | Radio interview answering children's questions about science |
Year(s) Of Engagement Activity | 2022 |
Description | BBC interview on local radio |
Form Of Engagement Activity | A press release, press conference or response to a media enquiry/interview |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Public/other audiences |
Results and Impact | Brief radio interview answering a child's question about where the sun goes during the day as part of Radio Leicester's regular segment where children ask questions |
Year(s) Of Engagement Activity | 2020 |
Description | Blog for the National Space Centre |
Form Of Engagement Activity | Engagement focused website, blog or social media channel |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Public/other audiences |
Results and Impact | I wrote a blog post for the National Space Centre discussing the backyard worlds citizen science project and advertising a demonstration of the platform at the Space Lates event in January 2020. The intended output was to encourage people to get involved with the various projects hosted at the zooniverse and to encourage people to get more involved with citizen science. |
Year(s) Of Engagement Activity | 2019 |
URL | https://spacecentre.co.uk/blog-post/hunting-for-planet-9/ |
Description | Interview for Quanta magazine |
Form Of Engagement Activity | A magazine, newsletter or online publication |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Public/other audiences |
Results and Impact | Interview with journalist for magazine articles about new discoveries |
Year(s) Of Engagement Activity | 2021 |
Description | National Space Centre Backyard worlds citizen science project demonstration |
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 | I ran a citizen science demonstration at the "Space Lates" event at the National Space Centre. I saw about 70 people who I showed how to use the Zooniverse platform and search for brown dwarfs in WISE data. The demonstration was aimed at encouraging the general public to be involved with the zooniverse and to get involved with citizen science projects. |
Year(s) Of Engagement Activity | 2020 |
URL | https://www.zooniverse.org/projects/marckuchner/backyard-worlds-planet-9/classify |
Description | Outreach videos for National Space Centre |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Public/other audiences |
Results and Impact | Provided the national Space Centre with short videos about me as an astronomer and my career path. These have been used online as part of the international day of women and girls in science celebrations as well as online events relating to careers in the space industry |
Year(s) Of Engagement Activity | 2020 |
Description | Podcast about UK in space industry |
Form Of Engagement Activity | A broadcast e.g. TV/radio/film/podcast (other than news/press) |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Industry/Business |
Results and Impact | Podcast as part of the UK space conference discussing "Space to inspire" |
Year(s) Of Engagement Activity | 2021 |
Description | Public talk to astronomy society |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Public/other audiences |
Results and Impact | Online talk (due to COVID) to an astronomy society |
Year(s) Of Engagement Activity | 2020 |
Description | Space Lates at the National Space Centre |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Public/other audiences |
Results and Impact | Public talk to general public on citizen science |
Year(s) Of Engagement Activity | 2021 |