What Temperature Is In Space And Its Cosmic Variations

Fundamental Temperature Concepts in Space

The thermodynamic principles governing temperature in space rely on three key factors:
1. Particle Density: Regions with sparse particles (e.g., interstellar voids) exhibit temperatures based on mean molecular kinetic energy, while dense environments (e.g., stellar atmospheres) reflect collisional equilibrium.
2. Radiative Transfer: Electromagnetic radiation dominates heat transfer in near-vacuum conditions, with objects emitting or absorbing energy according to their blackbody spectrum.
3. Dynamic Equilibrium: Many space environments lack thermal equilibrium, with temperatures varying across scales—e.g., a planet’s upper atmosphere may reach thousands of degrees due to solar UV absorption, while its surface remains habitable.

Thermodynamic Definitions and Kinetic Energy in a Vacuum

T = (2/3k) (1/2 mv²)
Where:

T = Temperature (K)

k = Boltzmann constant (1.38 × 10⁻²³ J/K)

m = Particle mass

v = Root-mean-square velocity of particles

The absence of a heat reservoir means temperature measurements in space often rely on spectral line widths (Doppler broadening) or thermal emission spectra rather than traditional thermometers.

Comparative Temperature Ranges in Cosmic Environments

Key Note: Temperatures in space are not uniform—a single location may exhibit multiple thermal regimes (e.g., a planet’s dayside vs. nightside). Values represent average kinetic temperatures unless specified otherwise.

Non-Equilibrium Thermodynamics in Space

Non-Equilibrium Defined: A system where temperature gradients, chemical reactions, or energy inputs prevent uniform energy distribution across particles.

2. Dust and Gas Phase Separation

3. Quantum Effects at Ultra-Low Temperatures

Measurement Techniques for Space Temperatures

Primary Methods:
1. Spectroscopy: Analyzing Doppler shifts and emission/absorption lines to infer particle velocities.
2. Blackbody Radiation: Measuring infrared to X-ray spectra to derive temperature via Planck’s law.
3. Particle Velocity Distributions: Using mass spectrometers (e.g., on

Measurement Methods for Space Temperatures

Space temperatures, ranging from near absolute zero in the cosmic void to millions of kelvin in stellar atmospheres, require specialized instruments and analytical techniques to quantify accurately. These methods leverage electromagnetic radiation across the spectrum, particle interactions, and thermodynamic principles to infer thermal conditions in environments where direct contact measurements are impossible. The following sections detail the primary instruments and analytical approaches used in astrophysical thermometry, emphasizing their operational principles and applications in observational astronomy.

Infrared and Optical Telescopes for Thermal Mapping

Infrared (IR) and optical telescopes detect thermal radiation emitted or absorbed by celestial objects, enabling temperature estimates based on blackbody radiation principles. These instruments are particularly effective for studying cold interstellar dust, planetary atmospheres, and star-forming regions where thermal emission dominates in specific wavelength bands.

Key instruments include:

Spitzer Space Telescope (2003–2020): Operated primarily in the mid- and far-infrared (3–180 µm), Spitzer measured thermal emission from dust grains and cold molecular clouds. Its Multiband Imaging Photometer (MIPS) at 70 and 160 µm was critical for mapping temperatures in protoplanetary disks and star-forming cores.

James Webb Space Telescope (JWST, launched 2021): With its Mid-Infrared Instrument (MIRI, 5–28 µm) and Near-Infrared Camera (NIRCam, 0.6–5 µm), JWST resolves finer temperature gradients in exoplanetary atmospheres and distant galaxies. MIRI’s coronagraphic capabilities also isolate thermal signatures of debris disks around stars.

Herschel Space Observatory (2009–2013): Specialized in far-infrared and submillimeter wavelengths (55–672 µm), Herschel mapped the coldest regions of the universe, including the cosmic microwave background (CMB) anisotropies and the thermal structure of molecular clouds.

Operational principles rely on Planck’s law and Wien’s displacement law, where the peak emission wavelength (λ_max) of a blackbody is inversely proportional to temperature (T). For example, dust at 20 K emits predominantly at ~150 µm, detectable by instruments like Herschel’s Spectral and Photometric Imaging Receiver (SPIRE). Calibration against known standards (e.g., laboratory blackbodies or CMB models) ensures accuracy within ±1–5 K for extended sources.

Radio Astronomy and Spectral Line Thermometry

Radio astronomy extends thermal measurements to neutral and ionized gas phases, where rotational and vibrational transitions of molecules or atomic fine-structure lines reveal kinetic temperatures. These methods are essential for probing the interstellar medium (ISM), molecular clouds, and high-redshift galaxies where optical/IR observations are obscured.

Key techniques include:

21-cm Line of Neutral Hydrogen (HI): The hyperfine transition of neutral hydrogen (1420 MHz) provides temperatures via its spin-flip probability, sensitive to gas densities and radiation fields. Observatories like the Green Bank Telescope (GBT) or Square Kilometre Array (SKA) use this line to map the warm ionized medium (WIM) and cold neutral medium (CNM) in galaxies.

Carbon Monoxide (CO) Rotational Lines: CO transitions (e.g., J=1→0 at 115 GHz) are bright tracers of molecular gas, with line widths reflecting thermal and turbulent motions. The Atacama Large Millimeter/submillimeter Array (ALMA) resolves CO emission in protostellar cores, yielding temperatures from radiative transfer models that account for excitation conditions.

Fine-Structure Lines of Ionized Gas: Transitions like [CII] (158 µm), [OIII] (52 µm), and [NII] (122 µm) probe electron temperatures (Te) in H II regions via their collisional excitation. The Stratospheric Observatory for Infrared Astronomy (SOFIA) has used these lines to measure Te ≈ 8,000–10,000 K in galactic star-forming regions.

Spectral line broadening (Doppler and pressure broadening) further refines temperature estimates. For instance, the Hα emission line (656.3 nm) in ionized hydrogen nebulae exhibits Gaussian profiles whose widths (Δλ) correlate with kinetic temperatures (Tk) via:

The Doppler width (Δλ_D) relates to temperature as:
\[
\Delta \lambda_D = \frac{\lambda_0}{c} \sqrt{\frac{2 k_B T}{m_H}},
\]
where \( \lambda_0 \) is the rest wavelength, \( c \) the speed of light, \( k_B \) Boltzmann’s constant, and \( m_H \) the hydrogen mass. In the Orion Nebula (M42), observed Hα widths correspond to core temperatures of ~10,000 K, while outer regions show ~5,000–7,000 K due to radiative cooling.

Cosmic Microwave Background as a Thermometric Baseline

The Cosmic Microwave Background (CMB) radiation, a relic of the Big Bang, provides the deepest temperature reference in the universe, with a current blackbody spectrum peaking at microwave frequencies (λ_max ≈ 1.06 mm). Its uniform temperature of 2.72548 ± 0.00004 K (Planck 2018 results) serves as a zero-point for cosmological thermometry, while anisotropies (ΔT/T ≈ 10⁻⁵) encode information about early-universe conditions.

Key applications include:

Temperature Fluctuations and Recombination Epoch: The CMB’s power spectrum, measured by missions like Planck and WMAP, reveals acoustic oscillations in the primordial plasma. The first peak (ℓ ≈ 200) corresponds to the sound horizon at recombination (z ≈ 1,100), where the CMB temperature was ~3,000 K.

Sunyaev-Zel’dovich Effect (SZ): Hot gas in galaxy clusters scatters CMB photons, imprinting spectral distortions (thermal SZ: ΔT/T ∝ T_e; kinetic SZ: ΔT/T ∝ v_r). Observations with ACT (Atacama Cosmology Telescope) or SPT (South Pole Telescope) constrain cluster temperatures to within ±1–2 keV (≈10–20 million K).

Baryon Acoustic Oscillations (BAO): The CMB’s angular scale, combined with large-scale structure surveys (e.g., DESI), cross-calibrates temperature evolution over cosmic time, linking early-universe physics to late-time expansion.

The CMB’s spectral radiance \( B_\nu(T) \) is described by Planck’s law:
\[
B_\nu(T) = \frac{2h\nu^3}{c^2} \frac{1}{e^{h\nu/k_B T} - 1},
\]
where deviations from a perfect blackbody (e.g., spectral distortions at µK levels) probe energy release mechanisms like Silk damping or primordial magnetic fields.

Particle Velocity Distributions and Kinetic Temperatures

In high-energy astrophysical plasmas (e.g., solar corona, accretion disks, or supernova remnants), Maxwell-Boltzmann distributions govern particle velocities, with temperatures derived from line-of-sight velocity dispersions. These methods are critical for environments where thermal equilibrium is not achieved, requiring non-equilibrium statistical mechanics.

Key approaches include:

Doppler Broadening in X-Ray Spectra: Instruments like Chandra or XMM-Newton resolve iron Kα lines (6.4–6.97 keV) in active galactic nuclei (AGN), where widths indicate virial temperatures (T ≈ 10⁷–10⁸ K) in broad-line regions. The relativistic Doppler effect further complicates analysis in strong gravitational fields.

Proton and Electron Temperatures in Solar Wind: Spacecraft like Parker Solar Probe measure ion distributions via electrostatic analyzers, revealing electron temperatures (Te ≈ 10⁵–10⁶ K) and proton temperatures (Tp ≈ 10⁴–10⁵ K) in coronal holes. Anisotropies in these distributions (Te ≠ Tp) indicate wave-particle interactions.

Neutral Gas Kinematics: For cold atomic hydrogen, 21-cm absorption spectroscopy against background quasars (e.g., GBT observations) traces spin temperatures (T_s ≈ 100–1,000 K) in the ISM, often higher than kinetic temperatures due to UV pumping.

For a Maxwellian velocity distribution, the second moment of the line-of-sight velocity \( v_z \) yields the kinetic temperature:
\[
T_k = \frac

Extreme Temperature Environments in the Cosmos

The universe encompasses a spectrum of thermal conditions far beyond Earth’s familiar range, from near-absolute-zero environments to regions where matter exists in plasma states exceeding billions of kelvin. These extremes arise from fundamental astrophysical processes—gravitational compression, nuclear fusion, relativistic particle interactions, and quantum degeneracy—each governing distinct cosmic phenomena. Understanding these environments provides insight into the behavior of matter under extreme conditions, the lifecycle of stars, and the fundamental laws of thermodynamics in astrophysical contexts.

The study of cosmic temperature extremes also informs theoretical models of black hole accretion, stellar nucleosynthesis, and the early universe’s thermal history. Below, the most extreme known locations in the cosmos are categorized by their thermal properties, alongside the mechanisms driving their formation.

Coldest Known Locations in the Universe

Ultra-cold regions in space approach absolute zero (0 K or −273.15°C), where quantum effects dominate and matter exhibits exotic states such as Bose-Einstein condensates (BECs). These environments form in expanding gas clouds or regions of minimal thermal energy transfer, often linked to the dissipation of kinetic energy into the cosmic microwave background (CMB).

Absolute Zero Context:
The third law of thermodynamics dictates that absolute zero is unattainable, but cosmic structures can reach temperatures within 10^−7 K of it, limited by quantum fluctuations and residual CMB radiation.

Notable Ultra-Cold Cosmic Environments:

• Boomerang Nebula (−272.15°C or 1 K)
  A pre-planetary nebula in the constellation Centaurus, this object exhibits the coldest recorded temperature in the universe. Its extreme cold results from a high-velocity bipolar outflow (164 km/s) of gas, which expands adiabatically, converting thermal energy into kinetic energy. The nebula’s central star, a red giant, ejects material at such speeds that the gas cools to near absolute zero, forming a Bose-Einstein condensate of hydrogen molecules.
• Laboratory-Emulated Ultra-Cold Gases (≤ 10^−9 K)
  While not cosmic, terrestrial experiments using laser cooling and magnetic trapping achieve temperatures where fermionic superfluids or degenerate quantum gases form. These systems mimic conditions in neutron star crusts or dark matter halos, where gravitational potential dominates thermal motion.
• Molecular Cloud Cores (10–20 K)
  Dense regions within giant molecular clouds (e.g., Orion Nebula) reach temperatures just above the CMB’s 2.725 K due to collisional de-excitation of molecules like CO and H₂. These environments are critical for star formation, as dust grains and gas cool efficiently, enabling gravitational collapse.

Mechanisms Driving Cosmic Cooling:

1. Adiabatic Expansion:
   In nebulae like the Boomerang Nebula, rapid gas expansion reduces particle collisions, lowering internal energy. The process follows the ideal gas law:

   \( PV^\gamma = \text{constant} \)
   where \( \gamma \) (adiabatic index) determines the temperature drop rate.

2. Radiative Cooling via Molecular Transitions:
   Polyatomic molecules (e.g., H₂O, CO) emit infrared photons during rotational/vibrational transitions, dissipating heat into space. This dominates in star-forming regions where dust absorbs and re-emits radiation.
3. Quantum Degeneracy Pressure:
   At temperatures below 1 μK, fermions (e.g., electrons in white dwarfs) occupy the lowest energy states, suppressing thermal motion. This stabilizes compact objects against gravitational collapse.

Hottest Known Locations in the Universe

Thermal extremes in the cosmos are primarily associated with gravitational energy release, nuclear fusion, and relativistic particle acceleration. Temperatures in these regions exceed those achievable in terrestrial laboratories, often reaching 10^12 K—conditions where matter exists as a quark-gluon plasma or undergoes pair production (matter-antimatter annihilation).

Energy-Temperature Relation:
In relativistic plasmas, temperature \( T \) scales with energy density \( \rho \) via:
\( k_B T \approx \frac{\hbar c}{R} \) (where \( R \) is the Schwarzschild radius for black holes).
For a solar-mass black hole, this implies \( T \approx 10^{12} \) K near the event horizon.

Notable Ultra-Hot Cosmic Environments:

• Quasar Cores (10^12 K)
  The accretion disks around supermassive black holes (SMBHs) in quasars reach temperatures where Compton scattering of photons by relativistic electrons dominates. The virial theorem relates temperature to gravitational potential:

  \( T \propto \frac{GMm}{k_B r} \)
  where \( M \) is the black hole mass, \( r \) the inner disk radius, and \( m \) the electron mass.

  Observations of broad emission lines (e.g., Mg II, C IV) indicate disk temperatures of 10^5–10^6 K, while the central corona may exceed 10^9 K due to magnetic reconnection.
• Supernova Remnants (10^7–10^8 K)
  The shock waves from Type Ia or core-collapse supernovae heat interstellar medium (ISM) gas to X-ray-emitting temperatures. Sedov-Taylor blast waves compress and heat surrounding material via:

  \( T \propto \frac{E_{\text{explosion}}}{n r^3} \)
  where \( E \) is explosion energy, \( n \) ambient density, and \( r \) shock radius.

  The Crab Nebula’s synchrotron radiation (from electrons at \( 10^{12} \) K) confirms these temperatures.
• Neutron Star Mergers (10^11–10^12 K)
  The collision of neutron stars (e.g., GW170817) produces r-process nucleosynthesis in an ultra-dense, ultra-hot environment. The merger’s tidal disruption and magnetohydrodynamic (MHD) turbulence generate temperatures where free neutrons coexist with protons, enabling rapid neutron capture.
• Big Bang Afterglow (10^9–10^10 K)
  The early universe’s plasma state (recombination epoch, ~380,000 years post-Bang) had temperatures of ~3,000 K, but primordial nucleosynthesis occurred at 10^9 K, where protons and neutrons fused into helium. The CMB’s redshifted photons today reflect this era’s thermal history.

Energy Transfer Processes in Extreme Environments:

Protostar Formation Energy Flow: The collapse of a molecular cloud core illustrates how gravitational potential converts into thermal energy, creating temperature gradients from the envelope to the core. Key stages include:

1. Gravitational Collapse (Initial State):
   A Jeans-unstable cloud (\( M > M_J \)) fragments under self-gravity, with kinetic energy \( K \) and potential energy \( U \) satisfying:

   \( |U| \gg K \) → \( T \approx 10–100 \) K (outer envelope).

2. Shock Heating (First Hydrostatic Core):
   As the core density increases (\( n > 10^{10} \text{ cm}^{-3} \)), adiabatic compression raises temperatures to ~2,000 K, ionizing hydrogen. The Larson-Penston model describes this phase:

   \( \frac{dT}{dt} \propto \frac{GMm}{r^2} \frac{dr}{dt} \)

3. Degeneracy Pressure Dominance (Kelvin-Helmholtz Contraction):
   Electron degeneracy halts further cooling, and the core temperature plateaus at ~1,000 K before deuterium fusion ignites. The Hayashi track on HR diagrams maps this phase.
4. Thermonuclear Ignition (Main Sequence):
   

   

   Human Perception vs. Scientific Reality of Space Temperature

   Popular media often depicts space as an unrelenting "freezing vacuum," evoking imagery of absolute cold where all thermal energy vanishes. However, this portrayal oversimplifies the fundamental physics of heat transfer in a vacuum, where temperature behaves differently than in Earth’s atmosphere. The absence of conduction or convection in space means objects do not "feel" cold in the conventional sense; instead, temperature is governed by radiative heat exchange and material properties. Understanding this discrepancy is critical for spacecraft engineering, as misconceptions can lead to flawed thermal management strategies. Below, the scientific reality of space temperature is contrasted with common misrepresentations, followed by a technical breakdown of how materials respond to extreme thermal conditions in a vacuum.
   

   Misrepresentations in Media and Scientific Clarifications

   The characterization of space as "freezing" stems from its average temperature of 2.725 Kelvin (K)—the cosmic microwave background (CMB) radiation temperature—measured in the farthest reaches of the universe. However, this value is misleading when applied to local environments, such as near Earth or the Sun, where temperatures can range from -270°C (3 K) in shadowed regions to thousands of degrees Celsius on sunlit surfaces. The confusion arises because:
   
5. Heat transfer mechanisms are absent in a vacuum: Without air or matter to conduct or convect heat, objects in space do not equilibrate with their surroundings through traditional means. Instead, they rely solely on radiation, where energy is emitted as electromagnetic waves.
6. Temperature is a measure of molecular kinetic energy: In a vacuum, an object’s temperature depends on its internal energy state, not ambient conditions. For example, a spacecraft’s electronics may operate at room temperature (20–30°C) while its outer surface radiates heat into the void at -100°C or lower.
7. The concept of "cold" is relative: The CMB temperature is not a direct measure of local thermal conditions. Near Earth, temperatures are influenced by solar radiation, planetary albedo (reflected sunlight), and the thermal inertia of materials.

Key Distinction:
"Space is not 'cold' in the sense of conducting coldness; it is a thermal insulator where objects retain or lose heat based on their emissivity and absorptivity, not ambient temperature."

Thermal Behavior of Materials in Space Vacuum

Materials in space undergo distinct thermal responses due to the absence of conduction and convection. Their behavior is dictated by:
1. Thermal expansion coefficients (α) – The rate at which materials expand or contract with temperature changes, critical for structural integrity.
2. Phase changes – Substances like liquid nitrogen (boiling point: -196°C at 1 atm) vaporize instantaneously in a vacuum, altering material properties.
3. Radiative properties – Emissivity (ε) and absorptivity (α) determine how efficiently a material absorbs or emits infrared radiation.

1. Thermal Expansion in Vacuum
   Materials expand or contract based on their coefficient of thermal expansion (α), measured in per Kelvin (K⁻¹). In space, rapid temperature fluctuations (e.g., -200°C to +150°C during Earth orbit) can induce mechanical stress. Examples:
   
2. Aluminum (α ≈ 23 × 10⁻⁶ K⁻¹): Expands significantly, requiring flexible joints or thermal buffers in spacecraft structures.
3. Invar (Fe-Ni alloy, α ≈ 0.6 × 10⁻⁶ K⁻¹): Used in precision instruments to minimize dimensional changes.
4. Graphite composites (α ≈ 0–7 × 10⁻⁶ K⁻¹): Anisotropic expansion (direction-dependent) complicates thermal design.

Design Consideration:
"Structural materials must account for cumulative thermal cycling over mission lifespans (e.g., 15+ years for deep-space probes), where repeated expansion-contraction cycles can lead to fatigue failure."

5. Phase Changes and Vaporization in Vacuum
   In a vacuum, liquids and solids undergo sublimation or explosive vaporization due to the absence of atmospheric pressure. Key examples:
   
6. Liquid nitrogen (N₂, bp: -196°C at 1 atm): Boils at -210°C in a hard vacuum (10⁻⁶ torr), causing rapid pressure buildup if contained. Spacecraft cryogenic systems (e.g., Hubble’s instruments) use multi-layer insulation (MLI) to mitigate heat leaks.
7. Water ice (sublimation point: ~195 K): Transitions directly to vapor in space, a process critical for comet studies (e.g., Rosetta mission) and ice-based propulsion systems.
8. Lubricants and adhesives: Many Earth-based formulations fail in vacuum due to outgassing or embrittlement. Space-qualified alternatives (e.g., silicone-based compounds) are required.

Vacuum-Specific Phenomenon:
"The boiling point of a liquid in a vacuum is determined by its vapor pressure, not ambient temperature. For example, liquid oxygen (LOX) boils at -118°C at 10⁻⁶ torr, regardless of external conditions."

9. Radiative Heat Transfer and Material Selection
   In space, Stefan-Boltzmann law governs heat exchange:
   P = εσA(T⁴ – T₀⁴)
   Where:
   
10. P = Net radiative power (W)
11. ε = Emissivity (0–1)
12. σ = Stefan-Boltzmann constant (5.67 × 10⁻⁸ W·m⁻²·K⁻⁴)
13. A = Surface area (m²)
14. T, T₀ = Object and surroundings temperature (K)

Materials are categorized by their thermal radiative properties:


15. High-emissivity surfaces (ε ≈ 0.8–0.9): E.g., white paints (zinc oxide), used to passively cool spacecraft by radiating heat.
16. Low-emissivity surfaces (ε ≈ 0.02–0.1): E.g., gold or silver coatings, used to reflect solar radiation (e.g., James Webb Space Telescope’s sunshield).
17. Selective surfaces: Combine absorptivity (α) and emissivity (ε) to balance solar absorption and IR emission (e.g., OSR—Optical Solar Reflectors).

Critical Design Trade-off:
"A material with high solar absorptivity (α ≈ 0.9) may overheat in sunlight, while one with low emissivity (ε ≈ 0.05) may fail to reject excess heat in shadow."

Challenges in Spacecraft Thermal Design

Designing materials to withstand space temperature extremes requires addressing:
1. Thermal gradients: A single spacecraft may experience ±200°C variations between sunlit and shadowed sides (e.g., International Space Station modules).
2. Outgassing: Organic materials release gases in vacuum, contaminating optical surfaces (e.g., Hubble’s COSTAR corrective optics).
3. Thermal conductivity mismatches: Combining metals (high conductivity) with insulators (low conductivity) creates hot/cold spots (e.g., electronic boxes sandwiched between radiators).

1. Multi-Layer Insulation (MLI) Systems
   MLI is the primary passive thermal control method, consisting of 10–50 layers of aluminum-coated Kapton or Mylar with low-conductivity spacers (e.g., Dacron netting). Key features:
   
2. Reduces heat transfer by 99% compared to still air (effective thermal conductivity: ~10⁻⁵ W/m·K).
3. Operating range: -270°C to +150°C (used in Mars rovers, Voyager probes).
4. Limitations: Adds mass (typically 5–10 kg/m²) and requires precise deployment to avoid wrinkles (which increase conductivity).
Space temperature transcends the binary of "hot" or "cold," instead unfolding as a spectrum dictated by energy gradients, particle interactions, and extreme astrophysical processes. The Boomerang Nebula’s near-absolute-zero chill contrasts sharply with quasar cores burning at trillions of kelvins, illustrating how temperature in the cosmos is a product of density, gravitational forces, and nuclear activity rather than ambient conditions. For humanity, these discoveries redefine engineering challenges—from shielding spacecraft against thermal fluctuations to interpreting spectral data that traces the universe’s thermal history. Ultimately, the study of space temperature is not just an exercise in measurement but a window into the fundamental forces shaping existence.

FAQ

What is the temperature in space measured in Celsius?

The average temperature of empty space is about -270.45°C (absolute zero is -273.15°C). Near Earth, cosmic background radiation keeps it around -2.7°C, but direct sunlight can heat objects to hundreds of degrees.

What is the temperature in space?

Space has no uniform temperature—it ranges from -270°C in deep vacuum to thousands of degrees near stars. The cosmic microwave background sets a baseline of -2.7°C, but objects exposed to sunlight can reach 120°C+.

What is the temperature of space in Fahrenheit?

The average temperature of empty space is roughly -455°F (near absolute zero). Near Earth, it’s about -26.5°F due to cosmic background radiation, while sunlight-warmed objects can hit 250°F+.

What is the temperature of space in Kelvin?

The cosmic microwave background fixes space’s baseline at 2.73K. Deep vacuum can approach 0K (absolute zero), while stellar regions reach millions of Kelvin.

What is the temperature in space in degrees?

Space has no single temperature—it varies from near 0K in voids to thousands of degrees near stars. The average between objects is roughly -270°C (or -454°F), but sunlight raises surface temps significantly.

What is the temperature in space between Mars and Earth?

In the void between Mars and Earth, space hovers near -2.7°C (270K) from cosmic background radiation. Objects in sunlight reach ~100–150°C, while shaded sides drop to -100°C or lower.

• astrophysical-extremes
• cosmic microwave background
• cosmic-thermodynamics
• space-temperature
• thermal physics

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Material	Emissivity (ε)	Application	Thermal Conductivity (W/m·K)
Aluminized Kapton (MLI)	0.03 (outer), 0.8 (inner)	Spacecraft insulation	0.12 (in-plane), 0.00001 (through-thickness)
White Zinc Oxide Paint