Outside our solar system, there are enormous,
extremely hot, alien-worlds.
These mysterious exoplanets were originally
thought to be the misfits of the cosmos, but
it turns out, there are hundreds of them and
they’re the source of a lot of speculation.
Astronomers call these exoplanets, hot-Jupiters
because they have a similar mass and composition
as our solar system’s largest planet.
They are, however, for the most part, much
larger and have a greater volume and as the
name suggests they are hot...like really really
hot.
The first hot Jupiter was discovered in 1995.
Astronomers spotted the exoplanet orbiting
extremely close to its parent star - so close
that it caused the star to wobble.
This observation inspired a new process of
exoplanetary discovery called the radial-velocity
method aka the ‘wobble method’.
It works like this… scientists use the light
spectrum to measure the movement of a star.
If the star’s light waves compress together
and then stretch out, it’s color signature
will change indicating that the star is in
fact, wobbling.
And this is a sign that a hot-Jupiter may
be close by.
Astronomers still use the wobble method today
and it’s contributed to the discovery of
hundreds of hot Jupiters.
These exotic extrasolar gas giants have a
few characteristics in common.
Like we mentioned earlier, hot Jupiters are
located feverishly close to their parent stars.
Take, OGLE-TR-56b for example.
Astronomers discovered this hot Jupiter clinging
to its parent star at a distance of about
0.02 AU.
AU stands for astronomical unit and 1 AU represents
the average distance from Earth to the Sun.
To put that into perspective, Mercury orbits
the sun at 0.39 AU.
So OGLE-TR-56b is about fourteen times closer
to its parent star than Mercury is to the
Sun.
Because of this close proximity, hot Jupiters
have scorching surface temperatures.
Since they are tidally locked, only one side
of these exoplanets faces its parent star.
While, both sides reach extreme temperatures,
the dayside is much hotter.
KELT-9b is the hottest gas giant on record
with a dayside temperature of more than 7,800
degrees Fahrenheit.
That’s about nine times hotter than the
average temperature on Venus - the hottest
planet in our solar system.
The temperatures of hot Jupiters fluctuate
as they orbit their parent star at a rapid
pace.
Their orbital periods are typically shorter
than 10 Earth days.
WASP-18b has one of the shortest orbits ever
discovered.
It takes this massive exoplanet just 23 hours
to rotate around its star in an almost perfectly
circular orbit.
But the orbital paths of younger hot Jupiters
are thought to be more unconventional, because
they’re further away from their parent stars.
HD 80606b for example, has a particularly
unusual route.
During its elliptical orbit the hot Jupiter
swings close to its star at speed and then
shoots back out at a great distance.
Scientists believe this exoplanet is in the
process of migrating towards its star, and
it’s path could help explain how hot Jupiters
are formed.
One of the leading hot Jupiter formation theories
holds that these gas giants were born farther
away from their stars, but over hundreds of
millions of years, are driven inward by the
gravitational influences from nearby stars
or planets.
And as a hot Jupiter migrates closer to its
star, its orbital path becomes more circular.
But when a hot Jupiter’s orbit becomes too
close, it will enter a death spiral.
The tidal forces from its much larger parent
star, will ultimately destroy the gas giant.
It’s a bittersweet ending for these beautiful
bizarre worlds.
While it’s sad to see them go, with every
hot Jupiter death, we will learn more about
the mysterious objects that inhabit 
the cosmos.
