From 8ad017aa3635fb9958898b6bcfe6ea0e2b0a0198 Mon Sep 17 00:00:00 2001 From: icweaver Date: Mon, 15 Feb 2021 22:51:56 -0500 Subject: [PATCH 1/4] added background --- docs/make.jl | 1 + docs/src/introduction.md | 103 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 104 insertions(+) create mode 100644 docs/src/introduction.md diff --git a/docs/make.jl b/docs/make.jl index 9349a7d..2ea06bd 100644 --- a/docs/make.jl +++ b/docs/make.jl @@ -20,6 +20,7 @@ makedocs(; pages=[ "Home" => "index.md", "Getting Started" => "gettingstarted.md", + "Introduction" => "introduction.md", "Benchmarks" => "bench.md", "API/Reference" => "api.md" ], diff --git a/docs/src/introduction.md b/docs/src/introduction.md new file mode 100644 index 0000000..e238032 --- /dev/null +++ b/docs/src/introduction.md @@ -0,0 +1,103 @@ +# Introduction + +## Historical overview + +Transit light curves are an essential tool used for the detection of +[exoplanets](https://en.wikipedia.org/wiki/Exoplanet). To date, there have been over 4,300 +confirmed planets discovered in over 3,400 different star systems, with an additional +2,400 candidates currently awaiting follow-up analysis and validation[^1]. Since the first +confirmed discovery of an exoplanet -- as part of a multi-planetary system in 1992[^2], +and the first exoplanet discovered around a Sun-like star shortly after in 1995[^3] -- +there has been an explosion in new discoveries, thanks in large part to the successful +[Kepler/K2](https://www.nasa.gov/mission_pages/kepler/main/index.html) and +[TESS](https://tess.mit.edu/) space missions. The large majority of these planets have +been detected via the [transit +method](https://exoplanets.nasa.gov/faq/31/whats-a-transit/): + +![](https://exoplanetarchive.ipac.caltech.edu/exoplanetplots/exo_dischist_cumulative_cb.png) +https://exoplanetarchive.ipac.caltech.edu + +## Transit method + +This method works by observing the dimming in apparent brightness of a star as a planet +passes in front of it from our point of view. The plot of the star's brightness as a +function of time defines the *white light curve* as seen in the schematic below: + +![](https://upload.wikimedia.org/wikipedia/commons/1/10/Theoretical_Transiting_Exoplanet_Light_Curve.jpg)
+[*How Do You Find an Exoplanet?* by John Asher Johnson](https://www.google.com/books/edition/How_Do_You_Find_an_Exoplanet/-DNJCgAAQBAJ?hl=en) + +Even just starting with a simple single planet system in a circular orbit, there is +already a wealth of information encoded in this diagram. These observations give us +insight not only into the bulk properties of the planet, but into the architecture of its +orbital system and characteristics of its host star as well. For example, *direct +observables* from the light curve like the *transit duration* $(T)$ and *ingress/egress* +time $(\tau)$ give us information about how tilted its orbit is and how fast the planet is +traveling, while the *transit depth* $(\delta)$ gives us a direct measure of the size of +the planet relative to its star. For circular orbits, these are nicely summarized by: + +```math +\begin{align} +\frac{R_\text{p}}{R_*} &= \delta^{1/2} \\ + +b^2 &= 1 - \delta^{1/2}\frac{T}{t} \\ + +\frac{a}{R_*} &= \frac{P\delta^{1/4}}{2\pi} +\left(\frac{4}{T\tau}\right)^{1/2} + +\rho_* &= \frac{3P}{G\pi^2}\left(\frac{\delta^{1/4}}{\sqrt{T\tau}}\right)^3 \quad, +\end{align} +``` + +where $P$ is the period of the planet's orbit and $a$ its semi-major axis, $b$ is the +impact parameter, $R_*$ is the radius of its star, and $\rho_*$ is the stellar +density. + +### Limb darkening +Not shown above is an added dimension that `Transits.jl` excels in, [limb +darkening](https://en.wikipedia.org/wiki/Limb_darkening#:~:text=Limb%20darkening%20is%20an%20optical,construct%20models%20with%20such%20gradients), demonstrated in the schematic below: + +![](https://user-images.githubusercontent.com/25312320/108404912-712f1c00-71ee-11eb-968e-b34001fe7a55.jpg)
+http://www.astro.utoronto.ca/~astrolab/files/AST326_LimbDarkening_2017.pdf + +This effect is intimately related to the shape of the light curve, and allows us to +constrain the brightness profile of the star itself. As we will see next, the method of +transit light curves is not just useful for the detection of exoplanets, but also for +taking it to the next step of characterizing its atmosphere. + +## Transmission spectroscopy +If we perform the technique of transit light curve modeling on a wavelength-by-wavelength +basis, we can further probe the properties of the host star and begin to make predictions +about the properties of the planet's atmosphere, such as its chemical composition and +whether clouds/hazes are likely to be present at higher altitudes. This analysis begins in +the same way as with the white light curve seen above, only now a *wavelength binned light +curve* is measured at a range of different wavelengths: + +![](https://user-images.githubusercontent.com/25312320/108020235-f1386480-6fe9-11eb-87f2-4970dabd7839.png) +Adapted from Weaver et al. (2021, *submitted*) + +Plotting these wavelength dependent transit depths then builds a *transmission +spectrum*, which is filled with information about the planet's atmosphere and its star, +summarized below: + +![Text here!](https://user-images.githubusercontent.com/25312320/108021680-124e8480-6fed-11eb-8eaf-bbf9b0df217b.jpg) +[Benneke & Seager (2012)](https://ui.adsabs.harvard.edu/abs/2012ApJ...753..100B/abstract) + +![](https://s3.amazonaws.com/aasie/images/0004-637X/853/2/122/apjaaa08cf1_hr.jpg) +[Rackham, Apai, & Giampapa (2018)](https://ui.adsabs.harvard.edu/abs/2018ApJ...853..122R/abstract) + +Performing forward +modeling (see, e.g., [Kempton et al. 2016](https://ui.adsabs.harvard.edu/abs/2017PASP..129d4402K/abstract), [Goyal et al. 2017](https://ui.adsabs.harvard.edu/abs/2018MNRAS.474.5158G/abstract)) and +retrievals (see, e.g., [Barstow et al. 2020](https://ui.adsabs.harvard.edu/abs/2020MNRAS.493.4884B/abstract) and references therein) using these +frameworks then allows us to explore exoplanetary atmospheres in never before seen detail. + +## Summary +The detection and characterization of exoplanets through their transit light curves is a relatively new technique +in the field of astronomy, with recent advances only being made possible through novel +uses of large, ground-based telescopes and soon in the future with planned [ELTs](https://en.wikipedia.org/wiki/Extremely_large_telescope) and space based +missions like [JWST](https://www.jwst.nasa.gov/). Studies using these observing facilities +will require the fast and precise computation of transit light curves, which [`Transits.jl`](https://github.com/JuliaAstro/Transits.jl) +aims to provide. + +[^1]: https://exoplanetarchive.ipac.caltech.edu/ +[^2]: https://ui.adsabs.harvard.edu/abs/1992Natur.355..145W/abstract +[^3]: https://ui.adsabs.harvard.edu/abs/1995Natur.378..355M/abstract From f321b7d97f19770037cad99004e96036841e770b Mon Sep 17 00:00:00 2001 From: Miles Lucas Date: Mon, 22 Feb 2021 12:34:17 -0600 Subject: [PATCH 2/4] update to universal DOI --- README.md | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/README.md b/README.md index 4ae6673..2e93e17 100644 --- a/README.md +++ b/README.md @@ -7,7 +7,7 @@ [![Stable](https://img.shields.io/badge/docs-stable-blue.svg)](https://juliaastro.github.io/Transits.jl/stable) [![Dev](https://img.shields.io/badge/docs-dev-blue.svg)](https://juliaastro.github.io/Transits.jl/dev) -[![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.4544095.svg)](https://doi.org/10.5281/zenodo.4544095) +[![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.4544094.svg)](https://doi.org/10.5281/zenodo.4544094) Flexible photometric transit curves with limb darkening. The goals of this package are, in this order @@ -121,4 +121,4 @@ flux = @. ld(orbit, t, 0.1) ## Citations -If you use Transits.jl or a derivative of it in your work please consider citing it at the [Zenodo DOI](https://doi.org/10.5281/zenodo.4544095). If you use `PolynomialLimbDark` or `QuadLimbDark` please also cite [Agol et al. (2020)](https://ui.adsabs.harvard.edu/abs/2020AJ....159..123A/abstract) and [Luger et al. (2019)](https://ui.adsabs.harvard.edu/abs/2019AJ....157...64L/abstract). If you use `Kipping13` please cite [Kipping (2013)](https://ui.adsabs.harvard.edu/abs/2013MNRAS.435.2152K/exportcitation). BibTeX for all those citations can be found in [`CITATIONS.bib`](CITATIONS.bib). +If you use Transits.jl or a derivative of it in your work please consider citing it at the [Zenodo DOI](https://doi.org/10.5281/zenodo.4544094). If you use `PolynomialLimbDark` or `QuadLimbDark` please also cite [Agol et al. (2020)](https://ui.adsabs.harvard.edu/abs/2020AJ....159..123A/abstract) and [Luger et al. (2019)](https://ui.adsabs.harvard.edu/abs/2019AJ....157...64L/abstract). If you use `Kipping13` please cite [Kipping (2013)](https://ui.adsabs.harvard.edu/abs/2013MNRAS.435.2152K/exportcitation). BibTeX for all those citations can be found in [`CITATIONS.bib`](CITATIONS.bib). From 6cb7e29402f487fade19a899a249225de1c54126 Mon Sep 17 00:00:00 2001 From: Miles Lucas Date: Mon, 22 Feb 2021 12:34:57 -0600 Subject: [PATCH 3/4] update to universal DOI --- docs/src/index.md | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/docs/src/index.md b/docs/src/index.md index 62f2290..b35b59c 100644 --- a/docs/src/index.md +++ b/docs/src/index.md @@ -10,7 +10,7 @@ CurrentModule = Transits [![Coverage](https://codecov.io/gh/juliaastro/Transits.jl/branch/master/graph/badge.svg)](https://codecov.io/gh/juliaastro/Transits.jl) [![License](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT) -[![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.4544095.svg)](https://doi.org/10.5281/zenodo.4544095) +[![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.4544094.svg)](https://doi.org/10.5281/zenodo.4544094) Transits.jl provides flexible and powerful occultation curves with limb darkening. The goals of this package are, in this order * have a simple interface with high *composability* @@ -36,4 +36,4 @@ pkg> add Transits#master ## Citations -If you use Transits.jl or a derivative of it in your work please consider citing it at the [Zenodo DOI](https://doi.org/10.5281/zenodo.4544095). If you use `PolynomialLimbDark` or `QuadLimbDark` please also cite [Agol et al. (2020)](https://ui.adsabs.harvard.edu/abs/2020AJ....159..123A/abstract) and [Luger et al. (2019)](https://ui.adsabs.harvard.edu/abs/2019AJ....157...64L/abstract). If you use `Kipping13` please cite [Kipping (2013)](https://ui.adsabs.harvard.edu/abs/2013MNRAS.435.2152K/exportcitation). BibTeX for all those citations can be found in [`CITATIONS.bib`](https://github.com/JuliaAstro/Transits.jl/blob/master/CITATIONS.bib). +If you use Transits.jl or a derivative of it in your work please consider citing it at the [Zenodo DOI](https://doi.org/10.5281/zenodo.4544094). If you use `PolynomialLimbDark` or `QuadLimbDark` please also cite [Agol et al. (2020)](https://ui.adsabs.harvard.edu/abs/2020AJ....159..123A/abstract) and [Luger et al. (2019)](https://ui.adsabs.harvard.edu/abs/2019AJ....157...64L/abstract). If you use `Kipping13` please cite [Kipping (2013)](https://ui.adsabs.harvard.edu/abs/2013MNRAS.435.2152K/exportcitation). BibTeX for all those citations can be found in [`CITATIONS.bib`](https://github.com/JuliaAstro/Transits.jl/blob/master/CITATIONS.bib). From e41f8fed25dca7f0733efe02273e9466a2ec25bf Mon Sep 17 00:00:00 2001 From: Miles Lucas Date: Mon, 22 Feb 2021 12:43:10 -0600 Subject: [PATCH 4/4] rearrange docs order --- docs/make.jl | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/docs/make.jl b/docs/make.jl index 2ea06bd..6eb32c7 100644 --- a/docs/make.jl +++ b/docs/make.jl @@ -19,8 +19,8 @@ makedocs(; ), pages=[ "Home" => "index.md", - "Getting Started" => "gettingstarted.md", "Introduction" => "introduction.md", + "Getting Started" => "gettingstarted.md", "Benchmarks" => "bench.md", "API/Reference" => "api.md" ],