Archaeology of Exo-Terrestrial Planetary Systems and a Search for Water
Lead Research Organisation:
University of Leicester
Department Name: Physics and Astronomy
Abstract
The research I propose will, uniquely, constrain the frequency and bulk chemical composition of terrestrial planets around other stars. Critically, my research program has the potential to detect the signature of water within rocky planetary bodies and thereby constrain the potential for oceans and habitats for life. This is made possible by stars at the end of their lives called white dwarfs. Over 95% of all stars in the Milky Way, including our Sun, will end their lives as white dwarfs, gently shedding their outer layers, then shrinking to Earth-sized, slowly cooling embers. By studying rocky planetary systems at white dwarfs, one sees a glimpse into the future of the Earth.
In the search for terrestrial planetary systems around other stars, white dwarfs offer a unique advantage. Owing to high gravities, heavy elements sink rapidly to the interior, leaving behind pure hydrogen or helium atmospheres. Those white dwarfs with rocky planetary systems can become contaminated by the infall of small, but detectable amounts of heavy elements such as silicon, magnesium, and iron (termed simply 'metals' by astronomers). Only recently, a number of white dwarfs polluted by rocky planetary debris have been discovered, and I have played a lead role in identifying and understanding these stars and their environments. These systems arose analogously to the rings of Saturn; a large asteroid or moon passing too close to the star was torn apart by gravity and now resides as a disk of material orbiting the white dwarf. This ring of debris gradually falls onto the star, contaminating its otherwise-pristine atmosphere with metals.
I will use white dwarfs polluted by metals to infer the masses, basic chemical compositions, and water content of their surviving rocky planetary systems. The proposed project has two parts: 1) to observe the rocky debris itself in orbit about the star, and 2) to measure the chemical content of this debris as it pollutes the star, broken down into its constituent elements.
The first part requires infrared and submillimeter observations to detect warm orbiting dust at these metal-polluted stars. The basic goal of this work is to unambiguously correlate orbiting rocky debris with the polluted stellar atmospheres, and firmly establish the material as planetary. The long-wavelength light from the warm dust provides a measure of the spatial distribution, temperature, size, and composition of the orbiting particles, thus constraining the nature of the now destroyed, rocky asteroid, moon, or planet. I will significantly increase the number of known white dwarfs with debris rings to gain a superior statistical understanding of the frequency of terrestrial planetary systems around other stars.
The second step is to use the star itself to determine the bulk chemical composition of the planetary debris falling onto and polluting its atmosphere. I will measure the relative elemental abundances of several to two dozen heavy elements in each of these stars using optical and ultraviolet observations. In doing so, it will be possible to establish the basic makeup of terrestrial planets around other stars, as well as catalog their diversity. Water can be identified by searching for oxygen in excess of that carried by rocks alone; a simple accounting of each detected metal as an oxide can reveal extra oxygen delivered as H2O. In this way I will determine the mass of water in rocky asteroids and moons, and compare these findings with water-rich Solar System bodies
In the search for terrestrial planetary systems around other stars, white dwarfs offer a unique advantage. Owing to high gravities, heavy elements sink rapidly to the interior, leaving behind pure hydrogen or helium atmospheres. Those white dwarfs with rocky planetary systems can become contaminated by the infall of small, but detectable amounts of heavy elements such as silicon, magnesium, and iron (termed simply 'metals' by astronomers). Only recently, a number of white dwarfs polluted by rocky planetary debris have been discovered, and I have played a lead role in identifying and understanding these stars and their environments. These systems arose analogously to the rings of Saturn; a large asteroid or moon passing too close to the star was torn apart by gravity and now resides as a disk of material orbiting the white dwarf. This ring of debris gradually falls onto the star, contaminating its otherwise-pristine atmosphere with metals.
I will use white dwarfs polluted by metals to infer the masses, basic chemical compositions, and water content of their surviving rocky planetary systems. The proposed project has two parts: 1) to observe the rocky debris itself in orbit about the star, and 2) to measure the chemical content of this debris as it pollutes the star, broken down into its constituent elements.
The first part requires infrared and submillimeter observations to detect warm orbiting dust at these metal-polluted stars. The basic goal of this work is to unambiguously correlate orbiting rocky debris with the polluted stellar atmospheres, and firmly establish the material as planetary. The long-wavelength light from the warm dust provides a measure of the spatial distribution, temperature, size, and composition of the orbiting particles, thus constraining the nature of the now destroyed, rocky asteroid, moon, or planet. I will significantly increase the number of known white dwarfs with debris rings to gain a superior statistical understanding of the frequency of terrestrial planetary systems around other stars.
The second step is to use the star itself to determine the bulk chemical composition of the planetary debris falling onto and polluting its atmosphere. I will measure the relative elemental abundances of several to two dozen heavy elements in each of these stars using optical and ultraviolet observations. In doing so, it will be possible to establish the basic makeup of terrestrial planets around other stars, as well as catalog their diversity. Water can be identified by searching for oxygen in excess of that carried by rocks alone; a simple accounting of each detected metal as an oxide can reveal extra oxygen delivered as H2O. In this way I will determine the mass of water in rocky asteroids and moons, and compare these findings with water-rich Solar System bodies
People |
ORCID iD |
| Jay Farihi (Principal Investigator / Fellow) |
Publications
Bergfors C
(2014)
Signs of a faint disc population at polluted white dwarfs
in Monthly Notices of the Royal Astronomical Society
Bonsor A
(2017)
Infrared observations of white dwarfs and the implications for the accretion of dusty planetary material
in Monthly Notices of the Royal Astronomical Society
Boyajian T
(2018)
The First Post- Kepler Brightness Dips of KIC 8462852
in The Astrophysical Journal
Cauley P
(2018)
Evidence for Eccentric, Precessing Gaseous Debris in the Circumstellar Absorption toward WD 1145 + 017
in The Astrophysical Journal Letters
Cunningham T
(2021)
Horizontal spreading of planetary debris accreted by white dwarfs
in Monthly Notices of the Royal Astronomical Society
Debes J
(2012)
THE WIRED SURVEY. III. AN INFRARED EXCESS AROUND THE ECLIPSING POST-COMMON ENVELOPE BINARY SDSS J030308.35+005443.7
in The Astrophysical Journal
Del Santo M
(2014)
The puzzling source IGR J17361-4441 in NGC 6388: a possible planetary tidal disruption event
in Monthly Notices of the Royal Astronomical Society
Dennihy E
(2020)
A Word to the WISE: Confusion is Unavoidable for WISE-selected Infrared Excesses
in The Astrophysical Journal
Dey A
(2019)
Overview of the DESI Legacy Imaging Surveys
in The Astronomical Journal
Dickinson N
(2012)
The origin of hot white dwarf circumstellar features The origin of hot DA circumstellar features
in Monthly Notices of the Royal Astronomical Society
Farihi J
(2012)
Scars of intense accretion episodes at metal-rich white dwarfs Intense metal accretion at white dwarfs
in Monthly Notices of the Royal Astronomical Society
Farihi J
(2013)
Evidence for water in the rocky debris of a disrupted extrasolar minor planet.
in Science (New York, N.Y.)
Farihi J
(2016)
Circumstellar debris and pollution at white dwarf stars
in New Astronomy Reviews
Farihi J
(2013)
Evidence of rocky planetesimals orbiting two Hyades stars
in Monthly Notices of the Royal Astronomical Society
Farihi J
(2017)
A circumbinary debris disk in a polluted white dwarf system
in Nature Astronomy
Farihi J
(2012)
A trio of metal-rich dust and gas discs found orbiting candidate white dwarfs with K -band excess White dwarfs with K-band excess
in Monthly Notices of the Royal Astronomical Society
Farihi J
(2022)
Relentless and complex transits from a planetesimal debris disc
in Monthly Notices of the Royal Astronomical Society
Farihi J
(2013)
Orbital and evolutionary constraints on the planet hosting binary GJ 86 from the Hubble Space Telescope
in Monthly Notices of the Royal Astronomical Society
Farihi J
(2012)
Precision astrometry of the exoplanet host candidate GD 66 Precision astrometry of GD 66
in Monthly Notices of the Royal Astronomical Society
Farihi J
(2016)
Solar abundances of rock-forming elements, extreme oxygen and hydrogen in a young polluted white dwarf
in Monthly Notices of the Royal Astronomical Society
Farihi J
(2018)
Dust production and depletion in evolved planetary systems
in Monthly Notices of the Royal Astronomical Society
Farihi J
(2018)
Magnetism, X-rays and accretion rates in WD 1145+017 and other polluted white dwarf systems
in Monthly Notices of the Royal Astronomical Society
Farihi J
(2014)
ALMA and Herschel observations of the prototype dusty and polluted white dwarf G29-38
in Monthly Notices of the Royal Astronomical Society
Gentile Fusillo N
(2017)
Trace hydrogen in helium atmosphere white dwarfs as a possible signature of water accretion
in Monthly Notices of the Royal Astronomical Society
Gentile Fusillo N
(2021)
White dwarfs with planetary remnants in the era of Gaia - I. Six emission line systems
in Monthly Notices of the Royal Astronomical Society
Girven J
(2012)
CONSTRAINTS ON THE LIFETIMES OF DISKS RESULTING FROM TIDALLY DESTROYED ROCKY PLANETARY BODIES
in The Astrophysical Journal
Gänsicke B
(2016)
HIGH-SPEED PHOTOMETRY OF THE DISINTEGRATING PLANETESIMALS AT WD1145+017: EVIDENCE FOR RAPID DYNAMICAL EVOLUTION
in The Astrophysical Journal Letters
Gänsicke B
(2018)
Broadening of Ly a by neutral helium in DBA white dwarfs
in Monthly Notices of the Royal Astronomical Society
Gänsicke B
(2012)
The chemical diversity of exo-terrestrial planetary debris around white dwarfs Exo-terrestrial debris around white dwarfs
in Monthly Notices of the Royal Astronomical Society
Hallakoun N
(2018)
Periodic optical variability and debris accretion in white dwarfs: a test for a causal connection*
in Monthly Notices of the Royal Astronomical Society
Hallakoun Na'ama
(2018)
Periodic optical variability and debris accretion in white dwarfs: a test for a causal connection
in Monthly Notices of the Royal Astronomical Society
Hermes J
(2014)
Heavy metals in a light white dwarf: abundances of the metal-rich, extremely low-mass GALEX J1717+6757
in Monthly Notices of the Royal Astronomical Society
Hoskin M
(2020)
White dwarf pollution by hydrated planetary remnants: hydrogen and metals in WD J204713.76-125908.9
in Monthly Notices of the Royal Astronomical Society
Izquierdo P
(2018)
Fast spectrophotometry of WD 1145+017
in Monthly Notices of the Royal Astronomical Society
Izquierdo P
(2021)
GD 424 - a helium-atmosphere white dwarf with a large amount of trace hydrogen in the process of digesting a rocky planetesimal
in Monthly Notices of the Royal Astronomical Society
Koester D
(2014)
The frequency of planetary debris around young white dwarfs
in Astronomy & Astrophysics
Manser CJ
(2019)
A planetesimal orbiting within the debris disc around a white dwarf star.
in Science (New York, N.Y.)
Melis C
(2012)
GASEOUS MATERIAL ORBITING THE POLLUTED, DUSTY WHITE DWARF HE 1349-2305
in The Astrophysical Journal
Raddi R
(2015)
Likely detection of water-rich asteroid debris in a metal-polluted white dwarf
in Monthly Notices of the Royal Astronomical Society
Redfield S
(2017)
Spectroscopic Evolution of Disintegrating Planetesimals: Minute to Month Variability in the Circumstellar Gas Associated with WD 1145+017
in The Astrophysical Journal
Rocchetto M
(2015)
The frequency and infrared brightness of circumstellar discs at white dwarfs
in Monthly Notices of the Royal Astronomical Society
Swan A
(2019)
The unbiased frequency of planetary signatures around single and binary white dwarfs using Spitzer and Hubble
in Monthly Notices of the Royal Astronomical Society
Swan A
(2019)
Interpretation and diversity of exoplanetary material orbiting white dwarfs
in Monthly Notices of the Royal Astronomical Society
Swan A
(2021)
Collisions in a gas-rich white dwarf planetary debris disc.
in Monthly notices of the Royal Astronomical Society
Swan A
(2019)
Most white dwarfs with detectable dust discs show infrared variability
in Monthly Notices of the Royal Astronomical Society: Letters
Tremblay P
(2020)
Gaia white dwarfs within 40 pc - I. Spectroscopic observations of new candidates
in Monthly Notices of the Royal Astronomical Society
Walters N
(2021)
A test of the planet-star unipolar inductor for magnetic white dwarfs
in Monthly Notices of the Royal Astronomical Society
Wilson D
(2016)
Carbon to oxygen ratios in extrasolar planetesimals
in Monthly Notices of the Royal Astronomical Society
Wilson D
(2019)
Multiwavelength observations of the EUV variable metal-rich white dwarf GD 394
in Monthly Notices of the Royal Astronomical Society
Wyatt M
(2014)
Stochastic accretion of planetesimals on to white dwarfs: constraints on the mass distribution of accreted material from atmospheric pollution
in Monthly Notices of the Royal Astronomical Society