ALTAIR / STELLAR DOSSIER

Altair

16.73 light-years from Sol

Rapid spin gives Altair an oblate shape and a hotter polar region above a cooler equator.

Stellar view ↗

01
Artist’s impression of Altair
A7 V · rapid rotator

A familiar star stretched by rotation.

Stellar conditions ↗

02
EFFECTIVE TEMPERATURE7,594 K

Light escaping from a gaseous photosphere.

Altair7,594 K
Sol5,770 K
Shared scale 0–10,000 K · effective, not core temperature

Evolution ↗

03
H–R MAPBRIGHTER ↑
SOLHEREHOTTERCOOLER →
CURRENT PHASE

Main sequence.

  1. NOWHydrogen fusion
  2. LATERGiant phase
  3. REMNANTWhite dwarf
A broad evolutionary sequence, not an estimate of remaining lifetime.

Photosphere & activity ↗

05
A conceptual equatorial view with modest flattening and brighter poles. Shape, viewing angle and brightness are illustrative.An oblate sun ↗ ARTIST’S IMPRESSION · 3 VIEWS

Diameter comparison ↗

06
2.008 × Sol

Luminosity ↗

07
≈ 10.6 × Sol

Total energy emitted · all wavelengths

Published luminosity estimate
Sources ↗
ALTAIR

Instrument detail

Artist’s impression of Altair

Artist’s impression · structure and color are illustrative.

One star, more than one radius.

Interferometry and a two-dimensional stellar model give an equatorial radius of 2.008 ± 0.006 solar radii. The polar radius is smaller, so the circular size comparison represents its equatorial diameter.

A latitude-dependent photosphere.

Rapid rotation reduces effective gravity at the equator. The equatorial region is cooler and dimmer than the poles, a pattern called gravity darkening. A single temperature is only a representative comparison. The model gives 6,780 K at the equator and 8,621 K at the pole, with a mean of 7,594 K.

The model reaches below the surface.

The 2020 analysis combines interferometry, spectroscopy and oscillation constraints. Its interior model suggests a core rotating faster than the envelope; this is an inference from a stellar model.

STELLAR PROFILESIZE · TEMPERATURE · EVOLUTION

A star in perspective.

DIAMETER / SOL2.01 ×

About 101% wider than our Sun.

Circles compare diameter, not mass or luminosity. Equatorial radius 2.008 ± 0.006 solar radii; polar radius 1.565 ± 0.014 solar radii, Bouchaud et al. (2020).

EFFECTIVE TEMPERATURE

Light escaping from a gaseous photosphere.

  • Altair≈ 7,594 K
  • Sol≈ 5,770 K

Shared scale: 0–10,000 K. Effective temperature describes total emitted energy per unit surface area; it is not the core temperature. Mean model temperature 7,594 K; the 2020 model ranges from 6,780 K at the equator to 8,621 K at the pole. Composition uncertainty affects these values.

LIFE PHASE

Main sequence.

  1. NOWHydrogen fusion
  2. LATERGiant phase
  3. REMNANTWhite dwarf

A broad evolutionary sequence, not an estimate of remaining lifetime.

Research · size and temperature ↗
LIFE & HUMAN SURVIVAL / THE STAR ITSELF
POSSIBILITY FOR LIFEIncompatible with known life

The star’s hot gaseous layers cannot provide the cool, stable environment required by life as we know it. Conditions on any orbiting worlds are a separate question.

WITHOUT PROTECTIONNot survivable

No breathable air or solid ground. Extreme heat and radiation make a close encounter lethal; a meaningful survival timer depends on where you are.

NASA · stellar structure and evolution ↗
10⁵1,000100.10.00110⁻⁵30,00010,0005,0002,500LUMINOSITY / SOL · BRIGHTER →HOTTER ← EFFECTIVE TEMPERATURE (K) → COOLERSUPERGIANTSGIANTSWHITE DWARFSMAIN SEQUENCESOLAltair
Altair7,594 K · ≈ 10.6 × Sol
Sol / reference5,770 K · 1 × Sol

Published luminosity estimate. Both axes are logarithmic; equal steps represent equal ratios.

Small points are other worlds in this atlas. The soft band marks the main sequence; region labels are broad guides, not a path through time.

Main sequence.

  1. NOWHydrogen fusion
  2. LATERGiant phase
  3. REMNANTWhite dwarf

A broad evolutionary sequence, not an estimate of remaining lifetime.

Research ↗

How much energy leaves the star?

≈ 10.6 × Sol

This compares total radiant power across all wavelengths, not just visible light or apparent brightness in our sky. The beams on the dashboard share a linear length scale.

Adopted literature luminosity 10.6 solar luminosities, discussed by Bouchaud et al. (2020); not computed from the equatorial radius as a sphere.

Equatorial radius 2.008 ± 0.006 solar radii; polar radius 1.565 ± 0.014 solar radii, Bouchaud et al. (2020).

Mean model temperature 7,594 K; the 2020 model ranges from 6,780 K at the equator to 8,621 K at the pole. Composition uncertainty affects these values.

Research · bolometric luminosity model ↗

One star, more than one radius.

Interferometry and a two-dimensional stellar model give an equatorial radius of 2.008 ± 0.006 solar radii. The polar radius is smaller, so the circular size comparison represents its equatorial diameter.

A latitude-dependent photosphere.

Rapid rotation reduces effective gravity at the equator. The equatorial region is cooler and dimmer than the poles, a pattern called gravity darkening. A single temperature is only a representative comparison. The model gives 6,780 K at the equator and 8,621 K at the pole, with a mean of 7,594 K.

The model reaches below the surface.

The 2020 analysis combines interferometry, spectroscopy and oscillation constraints. Its interior model suggests a core rotating faster than the envelope; this is an inference from a stellar model.

A conceptual equatorial view with modest flattening and brighter poles. Shape, viewing angle and brightness are illustrative.

An oblate sun

A conceptual equatorial view with modest flattening and brighter poles. Shape, viewing angle and brightness are illustrative.

An invented close view of equatorial gas; the warm tint illustrates relatively cooler emission, not a solid surface.

Along the equator

An invented close view of equatorial gas; the warm tint illustrates relatively cooler emission, not a solid surface.

An imagined polar photosphere. Fine convection patterns are artistic detail, not an observed map.

Across a bright pole

An imagined polar photosphere. Fine convection patterns are artistic detail, not an observed map.

Stellar images are artistic interpretations, not resolved photographs of this star.