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Fomalhaut

HIP 113368; Alpha PsA; 24 PsA

HIP 113368; Alpha PsA; 24 PsA Star PsA Visible Level 1 Naked eye / Binoculars
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Physical Properties

Magnitude 1.16
Spectral Type A4V
Star Color White (B-V 0.09)
Temperature 8602 K
Radius 1.9 R☉
Distance 25.4 ly

Position & Identifiers

RA 22h 57m 39.1s
Dec -29° 37' 20.0"
Constellation PsA
HR 8728
HIP 113368
Bayer Alpha
Flamsteed 24 PsA

Visibility

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Multiple Star System

Companion Mag 6.6
Companion Sp K4V
Position Angle 188°
Star Colors A: White B: Orange
Discoverer SHY 106

Size Comparison

Stellar Lifecycle

Spectral Classification

Hertzsprung-Russell Diagram

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Blackbody Spectrum

Stellar Absorption Spectrum

Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.

Stellar Notes

CPM with HR 8721.
FOMALHAUT; Os Piscis Meridiani; Os Piscis Notii; Difda al Auwel, the "First Frog."
Diam. = 0.00198 - 0.00210".

Survey Image

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About Fomalhaut

Description

Fomalhaut is the brightest star in the constellation Piscis Austrinus (the Southern Fish) at magnitude 1.16, located about 25 light-years from Earth. It is a white main-sequence star of spectral type A3V, about 1.9 times the mass of the Sun and 16.6 times more luminous. Fomalhaut is famous for its prominent debris disk — a ring of dusty material about 133 AU from the star — which was one of the first to be directly imaged. It is part of a wide triple star system with two distant companions.

Observing Tips

Fomalhaut is sometimes called 'the Loneliest Star' because it shines in a region of sky largely devoid of other bright stars, low in the southern sky as seen from northern latitudes during autumn evenings. Its isolated brilliance makes it easy to identify. From the Northern Hemisphere, look for it low in the south during October and November. It is best seen from September through November. From southern latitudes, it passes nearly overhead.

History

The name Fomalhaut comes from the Arabic 'Fam al-Hut' meaning 'mouth of the fish.' It was the last of the four Royal Stars of ancient Persia, marking the winter solstice around 2500 BC. In 2008, a direct image of what appeared to be a planet (Fomalhaut b) was taken by the Hubble Space Telescope. However, later observations suggested the bright spot may actually have been an expanding cloud of debris from a collision between two planetesimals.

Fun Facts

Fomalhaut's debris disk, sometimes called 'the Eye of Sauron' for its appearance in Hubble images, has a sharp inner edge that suggests a planet is gravitationally sculpting it. The Fomalhaut system is actually a wide triple: TW Piscis Austrini (Fomalhaut B) and LP 876-10 (Fomalhaut C) are distant companion stars about 1 and 3.2 light-years away respectively.