First Image of an Alien Planet
Hubble Space Telescope
||Hubble Space Telescope does it again, from ESA's
"Hubblecast." The NASA's ESA's Hubble Telescope has discovered an
extra-solar planet for the first time using direct visible light
|First Image of an Alien Planet
Hubble Space Telescope
|Fomalhaut is the brightest star in
the constellation Piscis Austrinus and one of the brightest stars in the
sky. Fomalhaut can be seen low in the southern sky in the northern
hemisphere in fall and early winter evenings. Near latitude 50˚N, it
sets around the time Sirius rises, and does not reappear until Antares
Its name means "mouth of the whale", from the Arabic fum
al-ḥawt. It is a class A star on the main sequence approximately 25
light-years (7.7 pc) from Earth.
It is classified as a Vega-like star that emits excess infrared
radiation, indicating it is surrounded by a circumstellar disk.
Fomalhaut holds a special significance in extrasolar planet research, as
it is the center of the first stellar system with an extrasolar planet
(Fomalhaut b) imaged at visible wavelengths.
Fomalhaut b is an extrasolar planet approximately 25 light-years away in
the constellation of Piscis Austrinus. The planet was discovered
orbiting the A-type main sequence star Fomalhaut in 2008 in photos taken
by the Hubble Space Telescope.
Fomalhaut b and three planets
around HR 8799, whose discovery was announced simultaneously, were the
first extrasolar planets whose orbital motion was confirmed via direct
The planet is estimated to be approximately the same size as Jupiter, with a maximum mass of three Jupiters and a most probable mass of 0.5 to two.
is 115 AU (17 billion km, 11 billion mi, about 20% greater than the
aphelion distance of Eris and 3.8 times the semi-major axis of Neptune)
from its sun, giving it an orbital period of 872 earth years.
Fomalhaut has about 16 times the Sun's luminosity,
so Neptune and Fomalhaut b are in regions of similar temperature (due to
the inverse square law).
Fomalhaut b is suspected, on the basis of its brightness in visible
light and dimness in infrared, to be surrounded by a circumplanetary
disc with a radius approximately 20–40 times the radius of Jupiter (by
comparison, the outer edge of Saturn's A ring is at a distance of only
about 2 Jupiter radii from the centre of the planet).
This size is similar to the orbital radii of Jupiter's Galilean
satellites and therefore may represent a stage in the formation of a
system of moons around the planet.
The planet Fomalhaut b is estimated to be approximately the same size as Jupiter and was discovered in 2008 in photos taken by the Hubble Space Telescope.
The existence of the planet was inferred in 2005 from its influence on the Fomalhaut dust belt; the belt is not centered on the star, and has a sharper inner boundary than would normally be expected.
However, the planet was only located in May 2008 after Paul Kalas and James Graham singled it out of Hubble photographs taken in 2004 and 2006.
NASA released the composite discovery photograph, obtained by the Hubble Space Telescope's ACS, on November 13th, 2008.