The Sun is about halfway through
At about 4.6 billion years old, the Sun has used roughly half of its main-sequence lifetime.
Scale Guide
The birth and death of stars, to scale
Explore the scaleStars form inside vast molecular clouds. Their later evolution branches with mass, mass loss and binary interaction, producing white dwarfs, neutron stars or black holes.
Birthplaces
Stars begin inside structures far larger than themselves
Shared physical scale
728ly
Initial mass strongly influences a star’s lifetime and endpoint, but it is not the only variable. Rotation, chemical composition, mass loss and exchange with a companion can alter the path.
The Orion, Eagle, Carina and Tarantula nebulae contain gas and dust spread across many light-years. Dense regions collapse and fragment into stars while radiation, winds and earlier generations of stars erode or compress nearby material.
Lifetimes
Heavier stars live shorter lives
Proxima Centauri can burn hydrogen for trillions of years; the Sun’s main-sequence lifetime is about ten billion years; massive stars such as Spica A exhaust fuel much faster. A heavier star has more fuel, but its higher core pressure burns it far faster: a star of ten solar masses lasts only a few tens of millions of years.
Shared physical scale
8.37million km
Sun-like endings
Sun-like stars end by shedding their outer layers
Low- and intermediate-mass stars can shed their outer layers and expose hot cores that ionize planetary nebulae such as NGC 7027, the Ring, Helix and Cat's Eye. The core contracts into a white dwarf; Sirius B contains about one solar mass in a body slightly smaller than Earth.
Shared physical scale
4.21ly
Massive endings
Massive stars end in supernovae or collapse
Betelgeuse and Eta Carinae A lose mass before their final endpoints; the Homunculus records Eta Carinae’s nineteenth-century Great Eruption, which the star survived. The Crab supernova left an expanding remnant and a pulsar that still powers it. Cygnus X-1 contains a stellar-mass black hole, another possible product of massive-star evolution.
Shared physical scale
8.14ly
Afterlives
A dying star can leave both a vast cloud and a tiny remnant
Sirius B, the Crab Pulsar and Cygnus X-1 represent a white dwarf, neutron star and stellar-mass black hole. Ejected gas may spread across light-years while the surviving core contracts to planetary, city or horizon scales.
Shared physical scale
7,954km
Scale anchors
Worth remembering
A teaspoon of white dwarf weighs tonnes
Sirius B averages about 2.7 tonnes per cubic centimeter, so a teaspoon of its matter would weigh more than ten tonnes.
The Crab supernova was seen in 1054
Chinese astronomers recorded the explosion that made the Crab Nebula; it stayed visible in daylight for about three weeks.
A neutron star is city-sized
The Crab Pulsar holds more mass than the Sun in a sphere about 20 kilometers wide and spins about 30 times per second.
Profiles
Birth clouds, stars, and stellar remnants
Star-forming regions, living stars, ejected nebulae and compact remnants from the branches above.
The Orion Nebula is one of the nearest large star-forming regions, close enough for astronomers to resolve young stars inside glowing gas and dust. Hubble observations revealed many protoplanetary disks here, allowing researchers to study how radiation from nearby massive stars affects planet-forming material.
The Eagle Nebula is a young star-forming region in the Milky Way best known for the Pillars of Creation, towering columns of cold gas and dust sculpted by intense radiation from nearby massive stars. Beyond the famous pillars, it is a broad active nebula whose embedded cluster is steadily reshaping the surrounding cloud.
The Carina Nebula is one of the Milky Way’s largest and most dramatic star-forming regions. It is a turbulent complex of glowing gas, dark dust, newborn stars, and young clusters, and it contains some of the most massive and luminous stars known, including Eta Carinae.
The Tarantula Nebula is the most luminous known star-forming region in the Local Group. It lies in the Large Magellanic Cloud and contains the dense young cluster R136, whose massive stars flood the surrounding gas with radiation and powerful winds.
Proxima Centauri is the nearest known star to the Sun, just over four light-years away. ESA describes it as a flare star prone to dramatic brightening, yet because it burns fuel so slowly it may remain on the main sequence for another four trillion years.
Visual creditscaleofspace.org / CC BY-NC 4.0
The Sun is the star at the center of the Solar System and the source of almost all the energy reaching its planets. It fuses about 600 million metric tons of hydrogen each second, and energy released in the core takes on the order of 100,000 years to work its way out to the visible surface.
Visual creditSolar Dynamics Observatory 2024 / NASA / SDO / HMI science team / Public domainSource: Wikimedia Commons
Sirius A is the brightest star in Earth’s night sky and the luminous primary of the Sirius binary. The same system also contains Sirius B, a white dwarf.
Visual creditscaleofspace.org / CC BY-NC 4.0
Spica A is the hot blue primary in the Spica binary and a Beta Cephei variable near the end of its main-sequence life. Its rapid rotation and close companion distort the star into an ellipsoidal shape, so the unresolved system brightens and dims slightly as the stars orbit.
Visual creditscaleofspace.org / CC BY-NC 4.0
Betelgeuse is a red supergiant nearing the end of its stellar life. Its dramatic dimming in 2019 and 2020 turned out to be caused by a dusty veil ejected from the star, giving astronomers a rare direct look at how giant stars shed material into space.
Visual creditscaleofspace.org / CC BY-NC 4.0
Eta Carinae A is the luminous blue variable primary in the Eta Carinae system, buried inside the Carina Nebula. Its dense wind makes the star’s surface hard to define, so this record uses an approximate visible stellar disk rather than a clean hydrostatic radius.
Visual creditscaleofspace.org / CC BY-NC 4.0
The Homunculus Nebula is the compact bipolar ejecta around Eta Carinae, blown out during the Great Eruption of the 1840s. Its twin lobes and thin equatorial skirt preserve that stellar outburst in unusually sharp, small-scale form.
Visual creditHubble 1996 / Nathan Smith (University of California, Berkeley), NASA / ESA / Public domainSource: Wikimedia Commons
NGC 7027 is a young planetary nebula in Cygnus with a compact bright inner region wrapped in fainter outer shells of gas. Recent Hubble observations show a remnant still changing shape, where newer, more directed outflows are running into older material shed by the dying central star.
The Cat's Eye Nebula is a planetary nebula in Draco whose bright inner core folds shells, jets, and dense knots around a dying central star. Hubble resolves that compact center as a layered record of repeated mass loss, distinct from the much fainter halo beyond it.
The Ring Nebula is a planetary nebula in Lyra, a glowing shell left behind when a dying Sun-like star shed its outer layers. Hubble reveals a distorted doughnut of ionized gas with lower-density material threaded through the center.
Visual creditHubble 2013 / NASA, ESA, and C. Robert O’Dell (Vanderbilt University) / Public domainSource: Wikimedia Commons
The Helix Nebula is one of the closest planetary nebulae to Earth, a glowing shell expelled by a dying Sun-like star. From Earth it can look like a simple doughnut, but the full structure is a layered remnant built from two nearly perpendicular gaseous disks and outflows.
Visual creditHubble 2002 / NASA, ESA, C.R. O'Dell (Vanderbilt University), M. Meixner and P. McCullough (STScI) / Public domainSource: NASA Science
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.
Visual creditscaleofspace.org / CC BY-NC 4.0
The Crab Nebula is the expanding supernova remnant created by the stellar explosion recorded in 1054. Its tangled filaments are still being energized from within by the Crab Pulsar, the neutron star left by the explosion.
Visual creditNASA's Great Observatories 2006 / X-ray: NASA/CXC/J. Hester (ASU); Optical: NASA/ESA/J. Hester & A. Loll (ASU); Infrared: NASA/JPL-Caltech/R. Gehrz (Univ. Minn.) / Public domainSource: Wikimedia Commons
The Crab Pulsar is the neutron-star core left behind by the explosion that also created the Crab Nebula. It spins about 30 times each second, and its magnetic engine drives much of the nebula’s glow by pouring particles and radiation into the surrounding wreckage.
Visual creditscaleofspace.org / CC BY-NC 4.0
Cygnus X-1 was the first cosmic object widely accepted as a black hole. It blazes in X-rays because the black hole is stripping hot gas from a massive blue supergiant companion and funneling it into a compact accretion flow.
Visual creditscaleofspace.org / CC BY-NC 4.0
The material is recycled. Gas shed by dying stars and blown out by supernovae enriches the clouds where the next stars form, carrying the carbon, oxygen and iron made inside earlier stars.
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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 explain selected parts of that range, while focused views filter the objects by subject.