Astronomers using the NASA/ESA Hubble Space Telescope
have seen dramatic changes in the atmosphere of a faraway planet.
Just after a violent stellar flare bathed it
in intense X-ray radiation
the scientists detected the planet’s atmosphere furiously evaporating away.
These violent events 63 light-years from Earth have given astronomers
their first ever glimpse of the changing weather and climate
on a planet outside our own Solar System.
Brought to you by the European Space Agency and NASA
Hubblecast episode 56: Dramatic change spotted on a faraway planet
Presented by Dr J, aka Dr Joe Liske
Planet HD 189733b has a blue sky, but that’s where the similarities with Earth end.
It’s a huge gas giant similar to Jupiter, but it lies extremely close to its star
much closer than any planet in the Solar System lies to the Sun.
This makes its climate exceptionally hot, with temperatures exceeding 1000ºC.
A team of scientists used Hubble to observe the planet in 2010
and again in 2011, as it was silhouetted against its parent star.
While backlit in this way, a planet’s atmosphere imprints its signature
on the starlight, allowing astronomers to decode what is happening
on scales that would be far too tiny to image directly.
The first set of observations actually… didn’t show much at all.
The scientists had hoped to confirm what they had seen once before
on another planet
the upper layers of the atmosphere gradually boiling off
under the intense assault of the starlight.
But Hubble’s first observations of HD 189733b
showed no trace of the atmosphere escaping.
But if the first set of observations was pretty boring,
the second set was anything but.
Just before they began to observe with Hubble for the second time,
the Swift satellite detected a huge flare coming from the surface of the star
giving off powerful radiation including atmosphere-frying X-rays.
This was like a more violent version of the solar flares
that disrupt communication satellites here on Earth.
When the planet slid into view a few hours later, the changes were startling.
Where they had seen a slumbering planet in 2010
they saw its atmosphere furiously boiling away in 2011.
A plume of gas was evaporating off the planet
which was losing at least 1000 tonnes of gas from its atmosphere every second.
The team believes that the spike in X-rays from the flare
can probably explain the atmospheric evaporation spotted with Hubble.
This type of radiation has enough energy to accelerate
the particles in the atmosphere, which would drive them off the planet.
There are other intriguing possibilities, though,
which are all linked to the star’s activity.
For example it might be gradual seasonal variations in X-rays from the star
rather than the sudden effect of the flare
which drove the change between 2010 and 2011.
This would be similar to the Sun’s 11-year sunspot cycle.
The team have fresh observations planned with Hubble
Hubble and ESA’s XMM-Newton X-ray space telescope
to help nail down exactly what triggered the atmosphere’s evaporation.
But regardless of the cause, this is the first time ever scientists have observed
a clear change in an exoplanet’s atmosphere.
Transcribed by ESA/Hubble