Star Systems » The Formalhaut Star System

About 25 light years away in the constellation of the southern fish Piscis Austrini (not to be confused with the well known zodiacal constellation Pisces) there is a brilliant star. Its common name is Formalhaut. The name is derived from the arabic which means mouth of the southern fish (pronounced fo-mal-low). It is about 2.3 times the mass of the Sun and about 16 times as luminous. It has the honour of being the first star with a gas giant planet that has been seen visibly by the Hubble Space Telescope. It has been found to be surrounded by a huge cloud of ice and dust. Observation of Fomalhaut's disk shows a hole in the middle. Perhaps the 'hole' is due to planets which have scooped up the dust. So far none have been detected within the hole. But in a stunning discovery announced in November of 2008, one was found by direct imaging to be orbiting within the disk. This image, taken with the Advanced Camera for Surveys aboard NASA's Hubble Space Telescope, shows the newly discovered planet, Fomalhaut b, orbiting its parent star, Fomalhaut. The image is illustrated on the right hand side above. The small white box at lower right pinpoints the planet's location. Fomalhaut b has carved a path along the inner edge of a vast, dusty debris ring encircling Fomalhaut that is 21.5 billion miles across. Fomalhaut b lies 1.8 billion miles inside the ring's inner edge and orbits 10.7 billion miles from its star. The inset on the right above is a composite image showing the planet's position during Hubble observations taken in 2004 and 2006. Astronomers have calculated that Fomalhaut b completes an orbit around its parent star every 872 year. It was only realised in 2008 that the tiny point of light which showed up in photographs taken in 2004 and 2006 was in fact a planet. (Credit for the photograph is given to Zoly Levay ZoltSTSci and NASA and ESA.)

Our own Solar System has a similar ring to that of Formalhaut called the Kuiper Belt, but it is estimated to have a thousand times less material than Fomalhaut's ring. Fomalhaut is believed to be a young star, only 100 to 300 million years old, with a potential lifespan of only a billion years. The surface temperature is around 8,751K. It's mass is 2.1 times that of the Sun luminosity is 18times greater and its diameter is roughly 1.8 times as large. Its habitable zone is far farther out than that for our Solar System. This is however rather theoretical since the star is only destined to 'live' about a billion years.

Ray Goodwin

Somewhere there are mountains
Glistening in the snow
Somewhere there are mountains
That we shall never know

Somewhere there are rivers
Flowing fast and free
Somewhere there are rivers
That we can never see

Somewhere there are oceans
And sun drenched island sands
Forests full of creatures
In vastly distant lands

Somewhere there’s a planet
Beneath an alien star
The people watch our tiny sun
And wonder where we are

One day perhaps we’ll find them
Across the void of space
Perhaps through ways as yet unknown
We’ll meet them face to face

The author of this web site Ray Goodwin holds B.Sc. Degrees from London University in Chemistry, Geology and Physiology and an M.Sc. in Biochemistry. He has spent most of his professional life teaching in Colleges of Technology. On his retirement he has entered the fields of astronomy, astrochemistry, astrobiology and space sciences. He has spent a great deal of his retirement in visiting amateur astronomy societies and in attending European Space Agency Symposia in ESTEC in the Netherlands and other scientific conferences in England and Sweden. He regularly attends the yearly European Astrofest in South Kensington London and other meetings in the UK. He has written scientific articles and given a number of lectures on diverse scientific subjects.

Readers of this web site are invited to e-mail the author ( and discuss their opinions of the topics dealt with and suggest any changes which they think may be helpful.

Life in the Cosmos Website
Version 01.00 - April 20, 2015.