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So a neutron star is kind of.
About the size of Chicago.
Unexpected elements from the BBC World Service.
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Hello and welcome to NewsHour.
It's coming to you live from the BBC World Service studios in London.
I'm Tim Franks.
And we're starting in Syria with a story that feels unpredicted and unpredictable.
Unpredicted because it's been a shock just how far and how fast rebel forces have advanced, and unpredictable because working out where this now leads is phenomenally difficult.
At least in this program, we'll try to ask some of the questions.
A very brief recap.
It was a few days ago that an alliance of rebel forces in the north of the country launched their offensive.
They swept south towards the city of Hama and also up to towards Aleppo, Syria's second city, which now, remarkably, appears to have fallen into their control.
Or at least the forces of President Bashar Al Assad have melted away.
As for Mr.
Assad himself, he made his first televised appearance since the rebel advances began on Wednesday, meeting the Iranian foreign minister in Damascus.
Let's begin with the voices of those caught up in this remarkable redrawing of the map of control.
The forces allied with President Assad do retain one advantage, command of the skies.
And that's the panicked sound of the Syrian Volunteer Civil Defence Group, known as the White Helmets, scrambling to respond to the aftermath of airstrikes on the city of Idlib.