Sirius B size and scale context

Sirius B is the white dwarf companion of Sirius A, the brightest star in the night sky. Hubble measurements show it packs about the Sun’s mass into a body smaller than Earth, with gravity so strong that a person would weigh tens of millions of pounds on its surface. Read its scale context, comparisons, and journey links on the canonical object page.

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Between the smallest and the largest, perspective is everything.

About

Scale of Space is a scroll-based journey through the universe, placing objects on a single logarithmic scale so you can compare size across an unbroken range.

Guides turn parts of that scale into curated essays, while focused views let you explore the same range through specific groups of objects.

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Solar System Planets From Electron to Atoms Stars To Scale Birth And Death Of Stars Black Holes To Scale

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Planets of the Solar System Stars of the Universe Black holes Subatomic scale

Return to Earth hello@scaleofspace.org

Between the smallest and the largest, perspective is everything.

About

Scale of Space is a scroll-based journey through the universe, placing objects on a single logarithmic scale so you can compare size across an unbroken range.

Guides turn parts of that scale into curated essays, while focused views let you explore the same range through specific groups of objects.

Editorial

Solar System Planets From Electron to Atoms Stars To Scale Birth And Death Of Stars Black Holes To Scale

Views

Planets of the Solar System Stars of the Universe Black holes Subatomic scale

Return to Earth hello@scaleofspace.org

Planets

Mars

Mars is the fourth planet from the Sun and the Solar System’s best-studied cold desert world. Ancient river valleys, lake beds, and minerals formed in water show that it once had a much wetter surface environment, even though today it is dry, thin-aired, and intensely cold.

Scale fact6,779 kmdiameter

Object class: Terrestrial planet
Mass: ~0.107 Earth masses
Host: Sun
Estimated age: ~4.5 billion years
Composition: Silicate rock, iron-rich minerals, polar ice
Temperature: ~210 K mean surface

Stellar remnants

Sirius B

Scale fact11,268 kmdiameter

Object class: White dwarf
Mass: ~1.02 solar masses
Host: Sirius system
Estimated age: ~228 million years
Composition: Electron-degenerate carbon-oxygen matter
Temperature: ~25,000 K surface

Planets

Earth

Earth is the rocky planet on which we live and the most familiar anchor for planetary scale. It remains the only world known to host life, with long-lived surface oceans that have shaped both its geology and its atmosphere.

Scale fact12,742 kmdiameter

Object class: Terrestrial planet
Composition: Silicate rock and iron core
Temperature: ~288 K mean surface
Estimated age: ~4.54 billion years
Host: Sun