Fact-checked by Grok 2 weeks ago

Thin disk

The thin disk is the dominant structural component of the Milky Way's galactic disk, forming a thin, flattened layer of stars, interstellar gas, and dust aligned with the plane of the galaxy's rotation, where the majority of current star formation takes place.^[1] This region hosts the younger, metal-enriched stellar populations classified as Population I, characterized by higher abundances of elements heavier than hydrogen and helium (metallicity [Fe/H] typically ranging from -1.0 to +0.5) and ages spanning from a few million years to about 13 billion years.^[2]^[3] Distinguished from the overlying thick disk, the thin disk features a smaller vertical scale height of approximately 300 parsecs, in contrast to the thick disk's roughly 1000 parsecs, resulting in a more compact distribution near the galactic plane.^[4] It comprises about 90% of the Milky Way's disk stars, with the remainder in the thicker component, and exhibits nearly circular orbits with relatively low velocity dispersions, indicating a dynamically stable and "cool" structure shaped by prolonged, quiescent evolution.^[5]^[2] The thin disk's radial extent reaches beyond 15 kiloparsecs from the galactic center, embedding spiral arms rich in young, hot stars and molecular clouds that fuel continued stellar birth.^[6] Observations from missions like Gaia have refined our understanding of the thin disk's formation, including the discovery (as of 2024) of its oldest component forming around 13 billion years ago, suggesting early co-formation elements with the thick disk alongside later gradual gas accretion and in-situ star formation over billions of years.^[7] Its chemical gradients and age-velocity relations provide key insights into the Milky Way's secular evolution, with ongoing research highlighting subtle variations in structure across different stellar age bins.^[8]

Overview

Definition

The thin disk is the primary planar component of spiral galaxies, consisting of stars, gas, and dust that orbit the galactic center in a flattened distribution.^[9] This structure represents the main site of ongoing star formation and contains the majority of a galaxy's younger, metal-rich stellar population, distinguishing it as the defining feature of disk-dominated systems.^[9] Unlike the central bulge or bar, which form dense, spheroidal concentrations of older stars near the galactic core, the thin disk exhibits a non-central, radially extended density profile that emphasizes its disk-like geometry.^[10] This planar arrangement arises from the conservation of angular momentum during galaxy assembly, creating a thin, flattened layer that rotates coherently around the center.^[9] In the Milky Way, the thin disk forms a thin, flattened structure with a radial extent up to approximately 15-20 kpc from the galactic center, coexisting with the central bulge and surrounding stellar halo as part of the overall galactic architecture.^[10]^[11]

Key Characteristics

The thin disk of the Milky Way exhibits a flattened structure perpendicular to the galactic plane, characterized by a vertical scale height of approximately 300 pc, which defines its thickness and distinguishes it from the thicker components of the galaxy. This scale height arises from the vertical distribution of stars and gas, resulting in a relatively compact layer that contains the majority of the disk's luminous matter. Radially, the thin disk extends with a scale length of about 2–3 kpc, reflecting the exponential decline in density outward from the galactic center, and it harbors a total mass on the order of $5 \times 10^{10} solar masses, comprising the bulk of the Milky Way's stellar disk population.^[12]^[13] Kinematically, the thin disk is defined by orderly motion, where stars and interstellar gas predominantly follow nearly circular orbits around the galactic center. At the Sun's position, approximately 8 kpc from the center, these orbital velocities average around 220 km/s, indicative of a flat rotation curve that supports the disk's stability against perturbations. This coherent rotation, with low velocity dispersions, underscores the thin disk's role as the primary site of organized galactic dynamics. The surface density profile of the thin disk follows an exponential form, \Sigma(r) \propto \exp(-r / h_R), where r is the galactocentric radius and h_R is the radial scale length, typically valued at 2–3 kpc. This profile captures the gradual tapering of mass density with increasing distance from the center, providing a foundational model for understanding the disk's spatial extent and mass distribution.

Structure and Composition

Stellar Populations

The thin disk of the Milky Way is primarily composed of young to intermediate-age stars, with most having ages less than 8–10 billion years, reflecting ongoing star formation over the past several gigayears.^[14] These stars predominantly belong to Population I, characterized by high metallicity levels, typically [Fe/H] from -1.0 to +0.5, which indicates enrichment from multiple generations of stellar nucleosynthesis.^[15] This population contrasts with older, metal-poor components in other galactic structures, emphasizing the thin disk's role as a site of relatively recent stellar activity. Metallicity in the thin disk exhibits both radial and vertical gradients. Radially, metallicity decreases outward from the galactic center at a rate of approximately -0.07 dex/kpc for stars aged 1–4 Gyr, flattening for older populations and approaching a near-uniform distribution beyond about 4 Gyr.^[16] Vertically, the gradient is steeper near the mid-plane, with metal-rich stars concentrated closer to the galactic plane, decreasing with height as older, more dispersed populations contribute at larger |Z|.^[17] These gradients arise from inside-out disk formation and radial migration, influencing the chemical evolution across the structure.^[18] The current star formation rate in the thin disk is estimated at 1–2 solar masses per year, fueling the production of new stars primarily in the spiral arms where gas densities are enhanced.^[19] Representative examples include OB associations, which trace the youngest, massive stars in these arms, and open clusters such as the Hyades, a ~0.7 Gyr old group exemplifying intermediate-age thin disk members with solar-like abundances.^[15]^[20]

Interstellar Medium

The interstellar medium (ISM) in the thin disk of the Milky Way is composed predominantly of gas, which accounts for approximately 10% of the disk's total mass, with the gas consisting mainly of neutral atomic hydrogen (HI), molecular hydrogen (H2), and ionized gas, along with helium and trace metals.^[21]^[22] Dust grains contribute about 1% of the total ISM mass by weight.^[23] This gas is organized into multiple phases maintained in rough thermal and pressure equilibrium: the cold neutral medium (CNM) at temperatures of 50–100 K and densities around 20–50 cm⁻³, primarily atomic HI; the warm neutral medium (WNM) at 5,000–8,000 K and lower densities of ~0.1 cm⁻³, also mostly HI; and dense molecular clouds where H₂ dominates, with temperatures below 50 K and densities exceeding 100 cm⁻³. These phases, as outlined in the classic three-phase ISM model, fill the thin disk with a total gas mass estimated at 8–9 × 10⁹ solar masses within 20 kpc of the center.^[24] Dust within the thin disk primarily causes extinction in visible wavelengths by absorbing and scattering starlight, which dims and reddens distant objects and enables three-dimensional mapping of dust distributions.^[25] In the infrared, thermal emission from heated dust grains traces its concentration along spiral arms, highlighting the ISM's association with large-scale galactic structures.^[26]^[25] Dynamically, the ISM's turbulent pressure from its multiphase structure provides support against the vertical gravitational compression of the thin disk, helping to establish its scale height. The gas's radial velocity dispersion \sigma_R further contributes to local stability via the Toomre criterion, Q \approx \frac{\sigma_R \kappa}{3.36 G \Sigma} > 1, where \kappa is the epicyclic frequency, G is the gravitational constant, and \Sigma is the total surface density; near the Sun, Q \approx 2, ensuring the disk resists axisymmetric gravitational collapse.^[27]

Formation and Evolution

Theoretical Models

The theoretical models for the formation of the thin disk in the Milky Way emphasize physical processes such as gravitational collapse, radial gas flows, and dynamical interactions that shape its structure over cosmic time. These frameworks aim to explain the disk's flattened geometry, chemical evolution, and kinematic properties through conservation laws and secular processes, often simulated via N-body and hydrodynamical methods. One foundational model is the monolithic collapse scenario, proposed by Eggen, Lynden-Bell, and Sandage in 1962, which posits a rapid formation of the galactic disk from the collapse of a single, massive proto-galactic gas cloud approximately 10 Gyr ago. In this process, the cloud undergoes a dynamical collapse on a timescale of order $10^8 years, during which conservation of angular momentum flattens the material into a thin, rotating disk structure, with higher angular momentum material settling into the equatorial plane to form the thin component. This model predicts an early, quiescent buildup of the disk without significant external perturbations, leading to a vertically thin configuration stabilized by self-gravity. An alternative framework is the inside-out formation model, which describes the thin disk's radial buildup through outward-propagating star formation triggered by gas accretion and inflows. In this scenario, star formation begins in the inner regions and progresses outward over several gigayears, building the disk from the center with increasing scale lengths at larger radii. This process is supported by observed metallicity gradients, where inner disk stars exhibit higher abundances due to prolonged enrichment from earlier, more intense star formation episodes, while outer regions remain metal-poor longer. Seminal chemical evolution models, such as those by Chiappini et al. (2001), incorporate radial gas flows to reproduce these gradients and the disk's age distribution. While major mergers are less emphasized for the thin disk, minor mergers and smooth accretion play a role in its dynamical evolution by heating pre-existing stellar populations, increasing velocity dispersions without destroying the overall thin structure. In this view, the thin disk emerges as a secularly evolved component, where ongoing gas accretion fuels star formation and maintains vertical thinness, while minor satellite interactions contribute to gradual thickening over time without dominating the formation. Simulations by Quinn et al. (1993) demonstrate how such minor mergers can heat a progenitor thin disk, scattering stars vertically but preserving the disk's coherence through subsequent dissipation. Recent Gaia data further support this by revealing age-dependent structures consistent with inside-out growth and minor accretion events.^[28] A key aspect of these models is the vertical equilibrium of the thin disk, where the stellar density stratification is described by the self-gravitating isothermal sheet solution to the Poisson equation:

\rho(z) = \rho_0 \, \sech^2\left(\frac{z}{z_0}\right)

Here, \rho(z) is the density at height z above the midplane, \rho_0 is the midplane density, and z_0 is the scale height related to the velocity dispersion \sigma_z by z_0 = \sigma_z^2 / (\pi [G](/page/G) \Sigma), with \Sigma the surface density; this profile arises from balancing gravitational potential and pressure support in a steady-state disk.

Chronological Development

Recent analyses of data from the Gaia mission have revealed the presence of metal-poor stars exceeding 12 billion years in age within the thin disk, indicating that its formation began approximately 13 billion years ago, shortly after the Big Bang.^[7]^[29] This discovery, reported in 2024, challenges prior estimates and suggests an early onset tied to the rapid collapse and settling of gas in the proto-galactic disk.^[30] Star formation in the thin disk reached its peak around 11 billion years ago, with rates increasing to approximately 11 M⊙ yr⁻¹, particularly in the inner regions where activity was highest between 6-8 billion years ago based on earlier analyses, transitioning to lower levels in the outer disk by 4-6 billion years ago.^[28]^[31] This inside-out buildup contributed to the disk's total stellar mass accumulating gradually over cosmic time, with a notable dip in activity around 8-9 billion years ago followed by sustained but reduced formation.^[13] The evolutionary phases of the thin disk began with an initial rapid settling of material post-formation, leading to a stable structure that supported ongoing star formation driven by density waves in spiral arms.^[32] Subsequent phases involved a transition to quieter accretion, with quenching of star formation observed in the inner regions around 8-10 billion years ago.^[33]^[34] The Solar System's migration from the innermost disk regions over its lifetime has influenced local chemical evolution, as evidenced by the Sun's elemental abundance patterns reflecting passage through varying metallicity environments in the thin disk.^[35]

Observations and Data

Historical Context

In the late 18th century, William Herschel conducted the first systematic star counts across the sky, mapping the distribution of stars and concluding that the Milky Way formed a flattened, lens-shaped disk with the Sun near its center.^[36] His observations, based on 683 directions using a 19-inch reflector telescope, revealed the concentration of stars along the galactic plane, establishing the disk-like structure of the stellar system.^[37] By the 1920s, Jacobus Kapteyn advanced these efforts through extensive star counts in selected areas of the sky. Kapteyn's analysis, incorporating proper motions and magnitudes, modeled the galaxy as a single flattened ellipsoid with the Sun offset from the center.^[38] Photometric surveys in the mid-20th century further illuminated the disk's morphology. The Palomar Observatory Sky Survey (POSS), initiated in 1949, produced wide-field photographic plates that visually captured the Milky Way's flattened, edge-on appearance, emphasizing its thin, extended nature against the background sky. These images provided empirical evidence for the disk's geometry, aiding early kinematic studies. A pivotal recognition of the thin disk as a distinct entity occurred in the 1980s through detailed star counts and velocity measurements. In their seminal 1983 study, Gerard Gilmore and I. Neill Reid analyzed stellar densities toward the South Galactic Pole, identifying a thin component with a scale height of about 300 pc alongside a thicker one at 1350 pc, thereby separating the young, kinematically cooler thin disk from the older thick disk. By the 1990s, Hertzsprung-Russell (HR) diagrams of nearby F and G dwarf stars confirmed the thin disk's relative youth. Edvardsson et al. (1993) derived ages from spectroscopic data and HR positions, showing that thin disk stars formed primarily within the last 8-10 billion years, contrasting with older populations and linking the component to ongoing star formation.

Contemporary Surveys

The Gaia mission, launched in 2013 by the European Space Agency, has revolutionized the study of the Milky Way's thin disk through high-precision astrometry and photometry for approximately 1.8 billion stars. By providing positions, parallaxes, proper motions, and radial velocities, Gaia has enabled detailed mapping of the thin disk's kinematics, including velocity fields and rotation curves that reveal its 3D structure and dynamical asymmetries. The third data release (DR3) in 2022 extended these measurements to distances up to 30 kpc, allowing reconstruction of extended kinematic maps that highlight radial and vertical velocity gradients in the thin disk.^[39]^[40] Complementary spectroscopic surveys such as APOGEE (Apache Point Observatory Galactic Evolution Experiment), part of the Sloan Digital Sky Survey, and LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope) have provided chemical abundance measurements for millions of thin disk stars, facilitating determinations of their ages and metallicities. APOGEE's near-infrared spectra of over 700,000 stars, including many thin disk giants, yield precise [C/N] ratios that serve as age proxies, revealing age-metallicity trends across the disk. Similarly, LAMOST has delivered medium-resolution spectra for more than 10 million stars, enabling abundance analyses that trace thin disk chemical evolution and identify young populations in the outer regions.^[41]^[42]^[43] To interpret these datasets, astronomers employ isochrone fitting techniques, which compare observed color-magnitude diagrams of thin disk stars to theoretical stellar evolution models to infer ages with uncertainties typically below 20% for main-sequence and subgiant populations. Additionally, chemodynamical modeling integrates chemical abundances, kinematics, and dynamical simulations to constrain the thin disk's vertical scale heights, predicting values around 300 pc for young populations and up to approximately 700 pc for older components based on vertical velocity dispersions.^[44]^[45]

Comparisons

With Thick Disk

The thin disk of the Milky Way exhibits a significantly smaller vertical scale height of approximately 300 pc compared to the thick disk's scale height of about 1 kpc, allowing the thicker component to extend up to roughly 3 kpc perpendicular to the galactic plane.^[46]^[47] This structural distinction arises from the thin disk's more compact, dynamically cooler configuration, which confines most of its stars closer to the midplane. In terms of stellar populations, the thick disk is markedly older, with the majority of its stars exceeding 8 Gyr in age and displaying lower metallicity levels around [Fe/H] ≈ -0.5, whereas the thin disk hosts a younger mix of stars that are generally more metal-rich.^[47] Kinematically, the thick disk shows elevated velocity dispersions, particularly a vertical component of ~40–50 km/s, reflecting a hotter dynamical state shaped by early mergers that disrupted and heated the stellar distribution.^[46]^[47]^[48] Overall, the thin disk dominates the Milky Way's disk mass, accounting for approximately 90% of disk stars, while the thick disk contributes only about 10%, with the two components overlapping radially but separated vertically due to their differing scale heights.^[6]

With Stellar Halo

The thin disk and stellar halo of the Milky Way exhibit profound morphological differences that reflect their distinct dynamical histories. The thin disk forms a flattened, axisymmetric structure embedded in the galactic plane, characterized by differential rotation and a vertical scale height of approximately 300 pc, which confines the majority of its stellar content to heights |z| < 1 kpc above and below the plane. In stark contrast, the stellar halo encompasses a roughly spherical distribution of stars that is pressure-supported rather than rotationally supported, extending far beyond the disk with an overall oblate shape; its inner regions (within ~5 kpc) display a triaxial ellipsoidal morphology, with axis ratios indicating elongation along the major axes. These morphological distinctions highlight the thin disk's role as a coherent, rotating subsystem versus the halo's more isotropic, diffuse envelope. Kinematically, the thin disk's stars pursue nearly circular, prograde orbits aligned with the galactic rotation, achieving mean azimuthal velocities of ~220 km/s in the solar neighborhood. Halo stars deviate markedly, tracing highly eccentric orbits with eccentricities typically exceeding 0.7, which contribute to their radial and vertical excursions across the galaxy. The halo as a whole shows minimal net rotation, with a mean azimuthal velocity lagging the local standard of rest by approximately 100 km/s, underscoring its pressure-dominated support against the galactic potential. In terms of chemical composition and stellar ages, the halo population is dominated by ancient, metal-poor stars with ages greater than 10 Gyr and metallicities [Fe/H] < -1, often exhibiting low alpha-element enhancements ([α/Fe] ≈ 0 for the accreted component). These traits contrast sharply with the thin disk's younger stellar cohort (ages <8 Gyr on average), which displays near-solar abundances ([Fe/H] ≈ 0, [α/Fe] ≈ 0) shaped by prolonged, low-intensity star formation. Such differences in chemistry and chronology suggest the halo's origins in early accretion events, while the thin disk evolved through in-situ processes involving gas-rich mergers and secular evolution. Spatially, these components occupy largely non-overlapping regimes: the thin disk's density drops exponentially beyond |z| ≈ 1 kpc, whereas the halo's stellar density prevails at vertical extents >10 kpc, comprising the dominant tracer of the galaxy's outer gravitational potential up to ~30 kpc. This vertical stratification ensures minimal contamination between the populations in high-latitude surveys.

References

[1]
Thin Disk | COSMOS - Centre for Astrophysics and Supercomputing
The thin disk is a defining component of disk galaxies, containing stars, gas, and dust in the galaxy's plane of rotation, and is an active site for star ...
[2]
25.5 Stellar Populations in the Galaxy - Astronomy 2e | OpenStax
Mar 9, 2022 · Young stars lie in the thin disk, are rich in metals, and orbit the Galaxy's center at high speed. The stars in the halo are old, have low ...
[3]
Thick Disk | COSMOS - Centre for Astrophysics and Supercomputing
Thin disks contain young stars, while the stars in thick disks are almost all older than 10 billion years. The metallicities of thick disk stars range from ...
[4]
The disk of the Milky Way
thick disk: scale height around 800 pc. These stars orbit the center of the Milky Way at a relatively slow speed. thin disk: scale height around 300 pc.
[5]
Galactic Archaeology | National Air and Space Museum
Jan 4, 2022 · Roughly nine-tenths of the stars reside in the thin disk, where they're more tightly packed.
[6]
Structure and Evolution of the Milky Way - Ken Freeman
The surface brightness of the thick disk is about 10% of the thin disk's, and near the Galactic plane it rotates almost as rapidly as the thin disk. Its ...
[7]
The formation and survival of the Milky Way's oldest stellar disk
Oct 10, 2024 · We present a study of the age-dependent structure and star formation rate of the Milky Way's disk using high-α stars with substantial orbital angular momentum.
[8]
Structural Parameters of the Thin Disk Population from Evolved ...
Feb 12, 2025 · This study investigates the structural parameters of the thin-disk population by analyzing the spatial distribution of evolved stars in the solar neighborhood.
[9]
SIZING UP THE MILKY WAY: A BAYESIAN MIXTURE MODEL META ...
THE MW DISK SCALE LENGTH DATA SET. We have collected 29 different measurements of the exponential scale length Ld, of the MW's disk published since 1990.
[10]
Reconstructing the star formation history of the Milky Way disc(s ...
In each case this would give the thick disc a mass of around 2.1 × 1010M⊙, 3.2 × 1010M⊙, and 2.7 × 1010M⊙ assuming a total Milky Way stellar mass of 5 × 1010M⊙.
[11]
Density Structure and Integrated Properties of the Milky Way Disk
Sep 10, 2025 · Near the solar neighborhood, the scale height of the thin disk is ... The characteristic scale length of the Milky Way disk is still ...
[12]
The Milky Way's stellar disk | The Astronomy and Astrophysics Review
May 1, 2013 · We review and lay out what analysis and modeling machinery needs to be in place to test mechanism of disk galaxy evolution and to stringently ...
[13]
The evolution of the Milky Way's radial metallicity gradient
We measure the age dependence of the radial metallicity distribution in the Milky Way's thin disc over cosmic time.
[14]
The Flattening Metallicity Gradient in the Milky Way's Thin Disk - arXiv
Sep 20, 2021 · We find that commonly used selections for ``thin disk'' stars (such as low-\alpha chemistry or vertically thin orbits) yield radial metallicity ...
[15]
evolution of the Milky Way's thin disc radial metallicity gradient with ...
They find a break in the radial metallicity relationship at around 12 kpc, recovering a gradient of −0.073 ± 0.002 dex kpc−1 inside and −0.032 ± 0.002 dex kpc−1 ...
[16]
The Star Formation Rate of the Milky Way as Seen by Herschel
We present a new derivation of the Milky Way's current star formation rate (SFR) based on the data of the Herschel InfraRed Galactic Plane Survey (Hi-GAL).
[17]
[1901.06050] Chemical compositions of giants in the Hyades ... - arXiv
Jan 18, 2019 · Three giants each from the Hyades and Praesepe open clusters were similarly observed and analysed. ... thin disc as determined from giants ...
[18]
mass distribution in disk galaxies
There are two major methods to measure the mass distribution using rotation curves, which are the direct method and the decomposition method.Missing: exp h_R)
[19]
H II Regions - Interstellar Medium and the Milky Way
Jun 27, 2022 · About 99% of the interstellar medium is gas with about 90% of it in the form of hydrogen (atomic or molecular form), 10% helium, and traces of other elements.
[20]
[PDF] IV Interstellar Dust
Since the ISM is about. 10% of the baryonic mass of the Galaxy, dust grains comprise roughly 0.1% of the total. At the same time, they absorb roughly 30-50% of ...
[21]
[PDF] Modelling mass distribution of the Milky Way galaxy using Gaia's ...
It is also precisely matches a bulge stellar mass of 1.63 × 10. 11Mʘ of the. M90 model in Ref.24. The mass of the gas disk is calculate as 8.43 ± 0.84 × 10.
[22]
Detection of the Milky Way spiral arms in dust from 3D mapping
Large stellar surveys are sensitive to interstellar dust through the effects of reddening. Using extinctions measured from photometry and spectroscopy, together ...
[23]
Dust in Galaxies - Department of Physics and Astronomy
Dust has been observed in two guises - optical/UV absorption and far-IR emission. Much of what (little) we know about its grain properties comes from analysis ...
[24]
Disk Stability of the Milky Way Near the Sun - IOPscience
We have generalized the Toomre's stability criterion to the more realistic 3D galaxy models. The generalized Toomre's parameter Q near the sun is 2.08 or 2.20 ...
[25]
4: The oldest thin disc of the Milky Way using Gaia-RVS
Conclusions. The Milky Way thin disc formed less than 1 billion years after the Big Bang and continuously built up in an inside-out manner – this finding ...Missing: timeline | Show results with:timeline
[26]
Milky Way's Thin Disk Formed Less Than One Billion Years from Big ...
Aug 1, 2024 · Using data from ESA's Gaia mission, astronomers have found a large number of metal-poor stars older than 13 billion years on orbits similar ...
[27]
Discovery of ancient stars on the stellar thin disk of the Milky Way
Jul 31, 2024 · They formed the Milky Way's thin disk less than 1 billion years after the Big Bang, several billion years earlier than previously believed. The ...Missing: peak Gyr
[28]
Stellar Mass Distribution and Star Formation History of the Galactic ...
(5) The disk has a peak star formation rate (SFR) changing from 6–8 Gyr ago at the inner part to 4–6 Gyr ago at the outer part, indicating an inside-out ...
[29]
Disk Formation and Evolution of Simulated Milky Way Mass Galaxy ...
Oct 2, 2025 · The formation of galactic disks is theoretically understood as a result of the conservation of angular momentum of cooling gas within dark ...
[30]
APOGEE provides evidence of star formation quenching in our Galaxy
We show here the first evidence that the Milky Way experienced a generalised quenching of its star formation at the end of its thick-disk formation ~9 Gyr ago.
[31]
[PDF] Radial structure and formation of the Milky Way disc - HAL
Dec 1, 2021 · The dilution occurred during the quenching phase, setting the initial conditions for the formation of the thin disc, whose evolution then ...
[32]
Remarkable Migration of the Solar System from the Innermost ...
We argue that the large movement of the solar system from the innermost disk over its lifetime is inferred from an elemental abundance pattern of the Sun.
[33]
XII. On the construction of the heavens - Journals
(2012) Mapping the Milky Way: William Herschel's Star Gages, The Physics Teacher, 10.1119/1.4772040, 51:1, (48-51), Online publication date: 1-Jan-2013.
[34]
Mapping the Milky Way: William Herschel's Star Gages
Jan 1, 2013 · From 1784 to 1785, ably assisted by his sister Caroline, Herschel attempted to map out the shape of the Milky Way star system. His cross section ...
[35]
Jacobus Kapteyn - UNLV Physics
The Kapteyn universe (1922) is at least approximately an ellipsoid of stars with diameter ≅ 17 kpc, maximum thickness ≅ 3 kpc, and the Solar System offset from ...Missing: counts | Show results with:counts
[36]
Gaia Data Release 3 - Mapping the asymmetric disc of the Milky Way
In this paper, we show the extraordinary capabilities of Gaia DR3 to shed light on the structure and kinematic issues mentioned above. We use similar ...
[37]
Mapping the Milky Way Disk with Gaia DR3: 3D Extended Kinematic ...
The kinematic maps reconstructed with LIM up to R ≈ 30 kpc show that the Milky Way is characterized by asymmetrical motions with significant gradients in all ...
[38]
APOGEE [C/N] Abundances across the Galaxy: Migration and Infall ...
The prospect of [C/N] abundance as an age indicator opens the possibility for studying [C/N]–metallicity or age–metallicity abundance trends across the MW disk.4. Results · 4.1. Lgb Sample · 5. Interpretations
[39]
APOGEE - SDSS
APOGEE is a large-scale, stellar spectroscopic survey conducted in the near-infrared (H-band) portion of the electromagnetic spectrum.The Apogee Survey · Apogee Data Products · Observing And Data Use...Missing: thin | Show results with:thin
[40]
Searching for R-process-enhanced Stars in the LAMOST Survey. II ...
May 8, 2025 · This study reports the discovery of two relatively bright, highly RPE stars ([Eu/Fe] > +0.70) located in the Milky Way disk, with [Fe/H] of −0.34 and −0.80, ...
[41]
NASA's Webb Digs into Structural Origins of Disk Galaxies
Jun 26, 2025 · The team's analysis suggests that thick disk formation occurs first, and thin disk formation follows. When this process occurs depends on the galaxy's mass.Data Through Thick and Thin · How This Applies to Home
[42]
Toward Precise Stellar Ages: Combining Isochrone Fitting with ...
We present a new age-dating technique that combines gyrochronology with isochrone fitting to infer ages for FGKM main-sequence and subgiant field stars.
[43]
Chemodynamical evolution of the Milky Way disk - I. The solar vicinity
Here we focus on the Milky Way, by using a detailed thin-disk chemical evolution model (matching local observables, which are weakly affected by radial ...
[44]
[PDF] Milky Way Components: Thin and Thick Disk
Dec 4, 2013 · Scale height ~ 1000 pc (thin disk: ~ 300 pc). ▫ Surface brightness of thick disk: ~ 10% of thin disk's. ▫ Stars mainly older than 10 Gyr ...<|control11|><|separator|>
[45]
The Galactic thick and thin disks: differences in evolution
The thick disk stars have a scale height from 760 to 1450 pc (Gilmore ... The “age – metallicity” relation of the thin and thick disk of the Galaxy ...
[46]
bursty origin of the Milky Way thick disc - Oxford Academic
... origin of this thick-to-thin transition has been hard to distill. One idea is that discs are born thick during an early period of gas-rich mergers (Brook et al.