13 research outputs found
Exoplanet Catalogues
One of the most exciting developments in the field of exoplanets has been the
progression from 'stamp-collecting' to demography, from discovery to
characterisation, from exoplanets to comparative exoplanetology. There is an
exhilaration when a prediction is confirmed, a trend is observed, or a new
population appears. This transition has been driven by the rise in the sheer
number of known exoplanets, which has been rising exponentially for two decades
(Mamajek 2016). However, the careful collection, scrutiny and organisation of
these exoplanets is necessary for drawing robust, scientific conclusions that
are sensitive to the biases and caveats that have gone into their discovery.
The purpose of this chapter is to discuss and demonstrate important
considerations to keep in mind when examining or constructing a catalogue of
exoplanets. First, we introduce the value of exoplanetary catalogues. There are
a handful of large, online databases that aggregate the available exoplanet
literature and render it digestible and navigable - an ever more complex task
with the growing number and diversity of exoplanet discoveries. We compare and
contrast three of the most up-to-date general catalogues, including the data
and tools that are available. We then describe exoplanet catalogues that were
constructed to address specific science questions or exoplanet discovery space.
Although we do not attempt to list or summarise all the published lists of
exoplanets in the literature in this chapter, we explore the case study of the
NASA Kepler mission planet catalogues in some detail. Finally, we lay out some
of the best practices to adopt when constructing or utilising an exoplanet
catalogue.Comment: 14 pages, 6 figures. Invited review chapter, to appear in "Handbook
of Exoplanets", edited by H.J. Deeg and J.A. Belmonte, section editor N.
Batalh
Transit Timing and Duration Variations for the Discovery and Characterization of Exoplanets
Transiting exoplanets in multi-planet systems have non-Keplerian orbits which
can cause the times and durations of transits to vary. The theory and
observations of transit timing variations (TTV) and transit duration variations
(TDV) are reviewed. Since the last review, the Kepler spacecraft has detected
several hundred perturbed planets. In a few cases, these data have been used to
discover additional planets, similar to the historical discovery of Neptune in
our own Solar System. However, the more impactful aspect of TTV and TDV studies
has been characterization of planetary systems in which multiple planets
transit. After addressing the equations of motion and parameter scalings, the
main dynamical mechanisms for TTV and TDV are described, with citations to the
observational literature for real examples. We describe parameter constraints,
particularly the origin of the mass/eccentricity degeneracy and how it is
overcome by the high-frequency component of the signal. On the observational
side, derivation of timing precision and introduction to the timing diagram are
given. Science results are reviewed, with an emphasis on mass measurements of
transiting sub-Neptunes and super-Earths, from which bulk compositions may be
inferred.Comment: Revised version. Invited review submitted to 'Handbook of
Exoplanets,' Exoplanet Discovery Methods section, Springer Reference Works,
Juan Antonio Belmonte and Hans Deeg, Eds. TeX and figures may be found at
https://github.com/ericagol/TTV_revie
A Neptune-sized transiting planet closely orbiting a 5–10-million-year-old star
Theories of the formation and early evolution of planetary systems postulate that planets are born in circumstellar disks, and undergo radial migration during and after dissipation of the dust and gas disk from which they formed^1, 2. The precise ages of meteorites indicate that planetesimals—the building blocks of planets—are produced within the first million years of a star’s life^3. Fully formed planets are frequently detected on short orbital periods around mature stars. Some theories suggest that the in situ formation of planets close to their host stars is unlikely and that the existence of such planets is therefore evidence of large-scale migration^4, 5. Other theories posit that planet assembly at small orbital separations may be common^6, 7, 8. Here we report a newly born, transiting planet orbiting its star with a period of 5.4 days. The planet is 50 per cent larger than Neptune, and its mass is less than 3.6 times that of Jupiter (at 99.7 per cent confidence), with a true mass likely to be similar to that of Neptune. The star is 5–10 million years old and has a tenuous dust disk extending outward from about twice the Earth–Sun separation, in addition to the fully formed planet located at less than one-twentieth of the Earth–Sun separation
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C/2014 UN<inf>271</inf>(Bernardinelli-Bernstein): The Nearly Spherical Cow of Comets
C/2014 UN271 (Bernardinelli-Bernstein) is a comet incoming from the Oort
cloud which is remarkable in having the brightest (and presumably largest)
nucleus of any well-measured comet, and having been discovered at heliocentric
distance au farther than any Oort-cloud member. We describe the
properties that can be inferred from images recorded until the first reports of
activity in June 2021. The orbit has with perihelion of 10.97 au
to be reached in 2031, and previous aphelion at au. Backwards
integration of the orbit under a standard Galactic tidal model and known
stellar encounters suggests this is a pristine new comet, with a perihelion of
au on its previous perihelion passage 3.5 Myr ago. The photometric
data show an unresolved nucleus with absolute magnitude colors that
are typical of comet nuclei or Damocloids, and no secular trend as it traversed
the range 34--23 au. For -band geometric albedo this implies a
diameter of km. There is strong evidence of brightness
fluctuations at mag level, but no rotation period can be discerned. A
coma consistent with a ``stationary' surface-brightness distribution
grew in scattering cross-section at an exponential rate from
m to m as the comet approached from 28 to 20 au. The activity is
consistent with a simple model of sublimation of a surface species in radiative
equilibrium with the Sun. The inferred enthalpy of sublimation matches those of
and . More-volatile species -- and -- must be
far less abundant on the sublimating surfaces
Extrasolar enigmas: from disintegrating exoplanets to exoasteroids
Thousands of transiting exoplanets have been discovered to date, thanks in
great part to the {\em Kepler} space mission. As in all populations, and
certainly in the case of exoplanets, one finds unique objects with distinct
characteristics. Here we will describe the properties and behaviour of a small
group of `disintegrating' exoplanets discovered over the last few years (KIC
12557548b, K2-22b, and others). They evaporate, lose mass unraveling their
naked cores, produce spectacular dusty comet-like tails, and feature highly
variable asymmetric transits. Apart from these exoplanets, there is
observational evidence for even smaller `exo-'objects orbiting other stars:
exoasteroids and exocomets. Most probably, such objects are also behind the
mystery of Boyajian's star. Ongoing and upcoming space missions such as {\em
TESS} and PLATO will hopefully discover more objects of this kind, and a new
era of the exploration of small extrasolar systems bodies will be upon us.Comment: Accepted for publication in the book "Reviews in Frontiers of Modern
Astrophysics: From Space Debris to Cosmology" (eds Kabath, Jones and Skarka;
publisher Springer Nature) funded by the European Union Erasmus+ Strategic
Partnership grant "Per Aspera Ad Astra Simul" 2017-1-CZ01-KA203-03556
The Wide-field Spectroscopic Telescope (WST) Science White Paper
The Wide-field Spectroscopic Telescope (WST) is proposed as a new facility dedicated to the efficient delivery of spectroscopic surveys. This white paper summarises the initial concept as well as the corresponding science cases. WST will feature simultaneous operation of a large field-of-view (3 sq. degree), a high multiplex (20,000) multi-object spectrograph (MOS) and a giant 3x3 sq. arcmin integral field spectrograph (IFS). In scientific capability these requirements place WST far ahead of existing and planned facilities. Given the current investment in deep imaging surveys and noting the diagnostic power of
spectroscopy, WST will fill a crucial gap in astronomical capability and work synergistically with future ground and space-based facilities. This white paper shows that WST can address outstanding scientific questions in the areas of cosmology; galaxy assembly, evolution, and enrichment, including our own Milky Way; origin of stars and planets; time domain and multi-messenger astrophysics. WST's uniquely rich dataset will deliver unforeseen discoveries in many of these areas. The WST Science Team (already including more than 500 scientists worldwide) is open to the all astronomical community. To register in the WST Science Team please visit https://www.wstelescope.com/for-scientists/participat
TOI-954 b and K2-329 b: short-period Saturn-mass planets that test whether irradiation leads to inflation
We report the discovery of two short-period Saturn-mass planets, one transiting the G subgiant TOI-954 (TIC 44792534, V = 10.343, T = 9.78) observed in TESS sectors 4 and 5 and one transiting the G dwarf K2-329 (EPIC 246193072, V = 12.70, K = 10.67) observed in K2 campaigns 12 and 19. We confirm and characterize these two planets with a variety of ground-based archival and follow-up observations, including photometry, reconnaissance spectroscopy, precise radial velocity, and high-resolution imaging. Combining all available data, we find that TOI-954 b has a radius of 0.852(-0.062)(+0.053) R-J and a mass of 0.174(-0.017)(+0.018) M-J and is in a 3.68 day orbit, while K2-329 b has a radius of 0.774(-0.024)(+0.026) R-J and a mass if 0.260(-0.022)(+0.020) M-J and is in a 12.46 day orbit. As TOI-954 b is 30 times more irradiated than K2-329 b but more or less the same size, these two planets provide an opportunity to test whether irradiation leads to inflation of Saturn-mass planets and contribute to future comparative studies that explore Saturn-mass planets at contrasting points in their lifetimes
A nearby transiting rocky exoplanet that is suitable for atmospheric investigation.
Spectroscopy of transiting exoplanets can be used to investigate their atmospheric properties and habitability. Combining radial velocity (RV) and transit data provides additional information on exoplanet physical properties. We detect a transiting rocky planet with an orbital period of 1.467 days around the nearby red dwarf star Gliese 486. The planet Gliese 486 b is 2.81 Earth masses and 1.31 Earth radii, with uncertainties of 5%, as determined from RV data and photometric light curves. The host star is at a distance of ~8.1 parsecs, has a J-band magnitude of ~7.2, and is observable from both hemispheres of Earth. On the basis of these properties and the planet's short orbital period and high equilibrium temperature, we show that this terrestrial planet is suitable for emission and transit spectroscopy