A time-series plot showing the brightness of an astronomical object over time, designed to reveal exoplanet transit events as characteristic dips in flux. The plot displays photometric measurements with error bars against time or orbital phase, with an optional fitted transit model overlay. This visualization is fundamental in observational astronomy for detecting and characterizing planetary transits, variable stars, and other periodic brightness variations.
""" anyplot.ai
lightcurve-transit: Astronomical Light Curve
Library: letsplot 4.10.1 | Python 3.13.14
Quality: 93/100 | Updated: 2026-06-20
"""
import os
import numpy as np
import pandas as pd
from lets_plot import (
LetsPlot,
aes,
element_blank,
element_line,
element_rect,
element_text,
geom_errorbar,
geom_line,
geom_point,
geom_ribbon,
geom_text,
ggplot,
ggsave,
ggsize,
labs,
layer_tooltips,
scale_color_manual,
scale_fill_manual,
scale_x_continuous,
scale_y_continuous,
theme,
theme_minimal,
)
LetsPlot.setup_html()
THEME = os.getenv("ANYPLOT_THEME", "light")
# Imprint palette — first series always #009E73
IMPRINT_GREEN = "#009E73"
IMPRINT_LAVENDER = "#C475FD"
# Theme-adaptive chrome tokens
PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
ELEVATED_BG = "#FFFDF6" if THEME == "light" else "#242420"
INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"
INK_MUTED = "#6B6A63" if THEME == "light" else "#A8A79F"
# Grid: rgba(INK, 0.15) composited on PAGE_BG
GRID_COLOR = "#D8D7D0" if THEME == "light" else "#3A3A36"
# Data: simulated phase-folded exoplanet transit
np.random.seed(42)
n_points = 400
phase = np.sort(np.random.uniform(0.0, 1.0, n_points))
transit_center = 0.5
transit_duration = 0.08
transit_depth = 0.01
ingress_duration = 0.015
half_dur = transit_duration / 2
half_ingress = ingress_duration / 2
# Limb-darkened transit model (observations)
dist_obs = np.abs(phase - transit_center)
model_flux = np.ones_like(phase)
in_transit = dist_obs < half_dur - half_ingress
r_obs = dist_obs[in_transit] / (half_dur - half_ingress)
model_flux[in_transit] = 1.0 - transit_depth * (1 - 0.3 * (1 - np.sqrt(1 - r_obs**2)))
in_ingress = (dist_obs >= half_dur - half_ingress) & (dist_obs < half_dur + half_ingress)
model_flux[in_ingress] = 1.0 - transit_depth * (half_dur + half_ingress - dist_obs[in_ingress]) / (2 * half_ingress)
flux_err = np.random.uniform(0.001, 0.003, n_points)
flux = model_flux + np.random.normal(0, 1, n_points) * flux_err
# Smooth model curve with uncertainty envelope
phase_model = np.linspace(0.0, 1.0, 1000)
dist_model = np.abs(phase_model - transit_center)
model_smooth = np.ones_like(phase_model)
in_transit_m = dist_model < half_dur - half_ingress
r_model = dist_model[in_transit_m] / (half_dur - half_ingress)
model_smooth[in_transit_m] = 1.0 - transit_depth * (1 - 0.3 * (1 - np.sqrt(1 - r_model**2)))
in_ingress_m = (dist_model >= half_dur - half_ingress) & (dist_model < half_dur + half_ingress)
model_smooth[in_ingress_m] = 1.0 - transit_depth * (half_dur + half_ingress - dist_model[in_ingress_m]) / (
2 * half_ingress
)
model_upper = model_smooth + 0.0015
model_lower = model_smooth - 0.0015
df_obs = pd.DataFrame(
{
"phase": phase,
"flux": flux,
"flux_err": flux_err,
"ymin": flux - flux_err,
"ymax": flux + flux_err,
"series": "Observations",
}
)
df_model = pd.DataFrame(
{
"phase": phase_model,
"flux": model_smooth,
"upper": model_upper,
"lower": model_lower,
"series": "Transit Model",
"band": "Model ±1.5σ",
}
)
# Annotation: mark the transit minimum
transit_min = model_smooth[np.argmin(np.abs(phase_model - transit_center))]
df_annot = pd.DataFrame({"phase": [transit_center], "flux": [transit_min - 0.0018], "label": ["Transit Minimum"]})
plot = (
ggplot()
+ geom_ribbon(
aes(x="phase", ymin="lower", ymax="upper", fill="band"),
data=df_model,
alpha=0.18,
color=IMPRINT_LAVENDER,
size=0.0,
tooltips=layer_tooltips()
.line("Model flux|@flux")
.line("Phase|@phase")
.format("@flux", ".5f")
.format("@phase", ".3f"),
)
+ geom_errorbar(
aes(x="phase", ymin="ymin", ymax="ymax"), data=df_obs, color=INK_MUTED, alpha=0.5, size=0.4, width=0.0
)
+ geom_point(
aes(x="phase", y="flux", color="series"),
data=df_obs,
size=2.5,
alpha=0.5,
tooltips=layer_tooltips()
.line("Flux|@flux")
.line("Phase|@phase")
.line("Error|@flux_err")
.format("@flux", ".5f")
.format("@phase", ".3f")
.format("@flux_err", ".4f"),
)
+ geom_line(aes(x="phase", y="flux", color="series"), data=df_model, size=1.5, tooltips="none")
+ geom_text(aes(x="phase", y="flux", label="label"), data=df_annot, color=INK_SOFT, size=3, hjust=0.5, vjust=0.5)
+ scale_color_manual(values={"Observations": IMPRINT_GREEN, "Transit Model": IMPRINT_LAVENDER}, name="")
+ scale_fill_manual(values={"Model ±1.5σ": IMPRINT_LAVENDER}, name="")
+ scale_x_continuous(name="Orbital Phase", breaks=[0.0, 0.2, 0.4, 0.6, 0.8, 1.0])
+ scale_y_continuous(name="Relative Flux")
+ labs(
title="lightcurve-transit · python · letsplot · anyplot.ai",
subtitle="Phase-folded exoplanet transit · Depth: ~1% · Quadratic limb darkening model",
)
+ theme_minimal()
+ theme(
plot_title=element_text(size=16, face="bold", color=INK),
plot_subtitle=element_text(size=10, color=INK_SOFT),
axis_title=element_text(size=12, color=INK),
axis_text=element_text(size=10, color=INK_SOFT),
legend_text=element_text(size=10, color=INK_SOFT),
legend_background=element_rect(fill=ELEVATED_BG, color=INK_SOFT),
legend_position="top",
panel_grid_major_x=element_blank(),
panel_grid_minor=element_blank(),
panel_grid_major_y=element_line(color=GRID_COLOR, size=0.4),
axis_ticks=element_blank(),
axis_line_x=element_line(color=INK_SOFT),
axis_line_y=element_line(color=INK_SOFT),
plot_background=element_rect(fill=PAGE_BG, color=PAGE_BG),
panel_background=element_rect(fill=PAGE_BG),
)
+ ggsize(800, 450)
)
ggsave(plot, f"plot-{THEME}.png", scale=4, path=".")
ggsave(plot, f"plot-{THEME}.html", path=".")
Part of Astronomical Light Curve on anyplot.ai.