Science 2017-10-06T14:49:42+00:00

Science with Twinkle

Twinkle’s High-level mission objectives

  1. Exoplanet science
    • Infrared and/or visible photometric follow-up of 1000+ exoplanets
    • Space-based spectroscopic observation of at least 100 pre-selected bright exoplanets in the Milky Way to enable characterisation of their atmospheres, down to super-Earth-sized objects
  2. Observations of solar system objects
  3. Observations of bright stars, disks, and supernovae

1. Exoplanets

Twinkle’s highly-stable instrument will allow the photometric and spectroscopic observation of a wide range of planetary classes around different types of stars, with a focus on bright sources close to the ecliptic. The planets will be observed through transit and eclipse photometry and spectroscopy, as well as phase curves, eclipse mapping and multiple narrow-band time-series. The targets observed by Twinkle will be composed of known exoplanets, mainly discovered by existing and upcoming ground surveys in our galaxy (e.g. WASP, NGTS and radial velocity surveys [1,2]), and will also feature planets newly-discovered by space observatories (Cheops, TESS [3,4]).

Exoplanet targets

Twinkle is designed to perform photometric and spectroscopic observations of exoplanets simultaneously from the optical to IR (0.4-4.5 micron). The instrument design will allow Twinkle to observe targets located at +/- 40º from the ecliptic, with the possibility to extend the field of regard to +/- 60º for non-demanding targets. The current target sample list is populated with known planets, but upcoming surveys are expected to find a large number of nearby bright planets. The figures below show the position of currently known planets observable with Twinkle, as well as simulations of expected targets [5].

Sky maps showing the locations of known and simulated planets observable by Twinkle. Here, transiting planets within the field of view are divided into size regimes as defined in the legend. Left: Known planets discovered as of June 1st, 2016. Right: Simulated planets that are projected to be found based on Kepler statistics [5]

Photometry (1000+ planets)

Follow-up visible and/or IR photometric observations using Twinkle will improve the orbital ephemerides and other planetary/stellar parameters and properties of a large sample of previously-discovered exoplanets.

Spectroscopy (100+ planets)

The brightest targets can be studied in great detail through spectroscopic measurements. The wavelength range adopted covers all of the expected key atmospheric gases, e.g. H2O, CO2, CH4, NH3, HCN, H2S, including exotic metallic compounds, such as TiO, VO, SiO [6] and condensed species. It will also permit the simultaneous monitoring of the stellar variability and the presence and distribution of clouds and hazes in the exoplanet atmosphere. Monitoring the weather and thermal properties of these planets through repeated measurements in the optical and infrared wavelength bands will be a key aspect of this mission. The figure below illustrates the results expected by Twinkle for a cloud-free atmosphere.

Simulated Twinkle observations of a hot-Jupiter around a bright star showing the quality of the spectra the instrument will provide.

2. Solar System Science

Twinkle’s scientific opportunities are not limited to exoplanet science: the visible and infrared spectrometers are also compatible with observations of numerous other astrophysical objects, including asteroids and comets, solar system moons and planets.

Asteroids

Key science possibilities:

  • Investigating hydration features – this is only possible for a space-based facility like Twinkle
  • Composition of stony asteroids with minerals on surface
  • Detecting organics in asteroid spectra
  • Rotational variation in asteroid spectra

The table below gives an overview of key features relevant to spectroscopy of asteroids.

Absorption feature Wavelength (microns) Molecules Useful for
Silicates 1

1.2

Olivene

Pyroxene

Determining minerology
Hydration 0.7

3

1.4

1.9

2.2-2.4

Unknown

OH, H2O (water-ice) & more

OH

OH & H2O (water-ice)

OH

Primitive asteroids

Primitive asteroids

Not yet detected in asteroids

Not yet detected in asteroids

Identifying phyllosilicates, aluminium, magnesium; not yet detected in asteroids

Organics 3.2-3.6 CH2 & CH3 Themis family asteroids (incl. Main Belt comets)

Key spectral features for asteroids in the 0.4-4.5µm range (work by S. Lindsay, N. Bowles, and B. Edwards, in preparation)

Comets

Key science possibilities:

  • Comae of bright comets: Twinkle will be able to characterise composition, size and structure of ice grains in comet comae

Importance of understanding comets:

  • Understanding of initial stages of planet formation
  • Structure of early solid grains in solar system formation
  • Pre-protoplanetary outer disk conditions

The table below gives an overview of key features relevant to spectroscopy of comets.

Absorption/ emission feature Wavelength (microns) Molecules Useful for
Water-ice 2

3

H2O Understanding primordial water sources
Water-vapour 2.7 H2O Understanding primordial water sources
Organics 3.3-3.6 CH2 & CH3 Understanding potential sources of organics on Earth
CO2 4.3 CO2 CO2 abundance constrains comet formation & activity

Key spectral features for comets in the 0.4-4.5µm range (work by S. Lindsay, N. Bowles and B. Edwards, in preparation)

3. Bright Sources

Our team is working to assess Twinkle’s performance for other science cases which include bright stars, brown dwarfs, disks and supernovae. If you are interested in exploring these capabilities please get in touch with our science team at info@twinkle-spacemission.co.uk

References

[1] D. L. Pollacco et al., The WASP Project and the SuperWASP Cameras, 2006, PASP, 118, Issue 848, pp.1407-1418.

[2] P. J. Wheatley et al., Next Generation Transit Survey (NGTS), 2013, EPJ Web of Conferences, 47, id.13002.

[3] C. Broeg et al., CHEOPS: A transit photometry mission for ESA’s small mission programme, 2013, EPJ Web of Conferences, 47, id.03005.

[4] G. R. Ricker et al., Transiting Exoplanet Survey Satellite (TESS), 2014, Proceedings of the SPIE, 9143, id 914320, 15pp.

[5] Rice et al., Analysis of Potential Targets for the Twinkle Space Mission, in preparation.

[6] J. Tennyson and S.N. Yurchenko, ExoMol: molecular line lists for exoplanet and other atmospheres, Mon. Not. R. astr. Soc., 425, 21-33 (2012)