WEBVTT FILE

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(music)

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(Narrator) I am Stefan Immler, an astrophysicist

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at NASA's Goddard Space Flight Center. I'd like to

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take you on a tour of two nearby galaxies in our cosmic neighborhood,

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the Large and Small Magellanic Clouds, as captured in ultraviolet light

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by NASA's Swift satellite. These images are the highest-resolution

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wide-field surveys of the galaxies at ultraviolet wavelengths.

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Both of these galaxies are less then 200,000 light

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years away, and each contains a few hundred million stars

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like our sun. If you live or travelled to the Southern Hemisphere, you'll

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see both of these galaxies as faint cloudy patches in the night

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sky. Both galaxies orbit our own as well as each other.

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Of the two, the LMC is physically larger and nearer

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to us than the SMC. Their messy shapes are products of gravitational

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interactions between them, tidal forces from the much bigger Milky Way, and

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internal processes like star formation. In visible light,

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we see a mix of sun-like stars, along with pink patches that

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mark star-formation regions, where hydrogen gas is set aglow by the light

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of young stars. These are especially prominent in the LMC.

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Viewed at higher energies, in the UV, the LMC looks

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very different. This wavelength blocks out the older stars,

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mostly showing those less than 500 million years old.

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These galaxies are relatively small, but they're also very

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close to us. This means that they appear much larger than the field of view

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of Swift's telescope. So we had to take many different observations and

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stitch them together. Swift had to image 172 separate

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fields in 2,200 short snapshots to take in

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the whole galaxy. The LMC's most striking feature

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is the dramatic Tarantula Nebula. This is the most active

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star factory in any of the dozens of galaxies in

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the Local Group, which includes the Milk Way and Andromeda.

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Thousands of stars form each year within cool, dark

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molecular clouds. Once they start shining, they blow off their

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birth cloud with powerful outflows called stellar winds.

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These winds, in turn, sculpt the gases into the Tarantula's

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spider-like shape. One star here, named R136a1,

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is one of the most massive known, weighing more than

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260 times the sun. The LMC holds more than

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a thousand star clusters formed during previous rounds of star formation.

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We mostly see hot, young, luminous stars, plus a few stars

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in exotic stages as they near stellar death.

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Wherever there are hot, young and massive stars there are also

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supernovae. In 1987, the closest stellar explosion

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in more than 400 years occurred in the outskirts, of the Tarantula Nebula.

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Even 26 years later, the after glow of the explosion

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remains detectable in the ultraviolet.

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All told, the new Swift mosaics reveal about a million objects

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in the LMC and about 250,000 objects in the

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smaller, less massive and more distant SMC.

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For this mosaic of the SMC, Swift imaged about

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50 fields and took 656 snapshots.

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One interesting feature is the massive young

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star cluster NGC 346. It contains

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the SMC's brightest star, HD 5980,

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a triple star system where all members among the most luminous

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stars known. The intense light and strong outflows from these stars

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mold the surrounding gas into a shape resembling a cobweb.

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The Swift UV mosaics allow

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us to study the evolution of young stars in the LMC and SMC

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all in one view. That's impossible for us to do for our own galaxy

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because we're inside it. The images

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give us a panoramic window into how stars are born, evolve and die

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across two complete galaxies. That gives us fresh

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insight into the many ways stars transformed the universe

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into what we see around us today.

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Music

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Beeping

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Beeping

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