Stranded NASA astronaut leaves the ISS for the first time in 225 days

After spending 225 days aboard the International Space Station (ISS), a stranded NASA astronaut has finally stepped outside for the first time.

But she's not coming home just yet.

Sunita Williams, the station's commander, worked with fellow NASA astronaut Nick Hague for some overdue repairs during the planned six-and-a-half-hour spacewalk.

"I'm coming out," Williams radioed at around 6.30 am ET, as the ISS floated 260 miles above Turkmenistan.

Williams and her crewmate Butch Wilmore were originally scheduled to spend just eight days on the ISS.

However, their mission was extended after a malfunction in the Boeing Starliner capsule made it unsafe for their return.

It's looking like the duo won't be able to return until late March or possibly April.

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This was Williams’ eighth career spacewalk and her second time living on the ISS.

Another spacewalk is planned for January 23 where Williams will team up with Wilmore for his first venture outside the station since their unexpectedly extended mission began.

NASA's current plan is to bring Williams, Wilmore, Hague and Russian Cosmonaut Aleksandr Gorbunov back to Earth after the SpaceX Crew-10 mission reaches the ISS.

Originally planned for February, this mission has now been delayed by one or two months.

Medical professionals are also concerned about Williams' condition as she appeared gaunt in ISS photos sent back to Earth.

"What you're seeing there in that picture is somebody that I think is experiencing the natural stresses of living at a very high altitude, even in a pressurized cabin, for extended periods," said Dr. Vinay Gupta, a pulmonologist and veteran in Seattle.

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"Her cheeks appear a bit sunken - and usually it happens when you've had sort of total body weight loss."

Dr. Gupta added: "I think what I can discern by her face and her cheeks being sunken in is that [she] has probably been at a significant [calorie] deficit for a while."

However, Williams dismissed the claims, saying in a video interview that she had actually gained muscle during her time in space.

"My thighs are a little bit bigger, my butt is a little bit bigger. We do a lot of squats," she said.

Interestingly, Williams noted that she's the same weight as when she launched to the ISS in June, but her change in appearance was due to 'fluid shift.'

NASA has delayed the Crew-19 launch in December to allow extra processing time for SpaceX’s new Dragon spacecraft. Meaning that the Starliner crew will spend at least 10 months in space before finally returning to Earth.