White Dwarf - Blog Posts

The trickster “Blinking Planetary”

Planetary nebula NGC 6826 is located about 4,200 light years from Earth in Cygnus. When observers look directly at it through a small telescope, they typically see only the nebula’s sparkling-white central star. However, by averting one’s gaze, glancing away from the central star, the nebula’s bulbous dust clouds come into view. This optical trickery earned this planetary nebula the name the "Blinking Planetary.” 

Over the next several thousand years, the nebula will gradually disperse into space, and then the central star will slowly cool as it radiates its energy for billions of years as a white dwarf. 

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Say hello to the Saturn Nebula 👋

Garden-variety stars like the Sun live fairly placid lives in their galactic neighborhoods, casually churning out heat and light for billions of years. When these stars reach retirement age, however, they transform into unique and often psychedelic works of art. This Hubble Space Telescope image of the Saturn Nebula shows the result, called a planetary nebula. While it looks like a piece of wrapped cosmic candy, what we see is actually the outer layers of a dying star.

Stars are powered by nuclear fusion, but each one comes with a limited supply of fuel. When a medium-mass star exhausts its nuclear fuel, it will swell up and shrug off its outer layers until only a small, hot core remains. The leftover core, called a white dwarf, is a lot like a hot coal that glows after a barbecue — eventually it will fade out. Until then, the gaseous debris fluoresces as it expands out into the cosmos, possibly destined to be recycled into later generations of stars and planets.

Using Hubble’s observations, scientists have characterized the nebula’s composition, structure, temperature and the way it interacts with surrounding material. Studying planetary nebulas is particularly interesting since our Sun will experience a similar fate around five billion years down the road.

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Say hello to the Butterfly Nebula 👋

It looks like our Hubble Space Telescope captured an image of a peaceful, cosmic butterfly unfurling its celestial wings, but the truth is vastly more violent. In the Butterfly Nebula, layers of gas are being ejected from a dying star. Medium-mass stars grow unstable as they run out of fuel, which leads them to blast tons of material out into space at speeds of over a million miles per hour!

Streams of intense ultraviolet radiation cause the cast-off material to glow, but eventually the nebula will fade and leave behind only a small stellar corpse called a white dwarf. Our middle-aged Sun can expect a similar fate once it runs out of fuel in about six billion years.

Planetary nebulas like this one aren’t actually related to planets; the term was coined by astronomer William Herschel, who actually discovered the Butterfly Nebula in 1826. Through his small telescope, planetary nebulas looked like glowing, planet-like orbs. While stars that generate planetary nebulas may have once had planets orbiting them, scientists expect that the fiery death throes these stars undergo will ultimately leave any planets in their vicinity completely uninhabitable.

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Say hello to globular cluster 47 Tucanae 👋

This glittery spray of ancient stars is about 16,700 light-years away from Earth toward the constellation Tucana. Globular clusters like this one are isolated star cities, home to hundreds of thousands of stars that are held together by their mutual gravity. And like the fast pace of cities, there's plenty of action in these stellar metropolises. The stars are in constant motion, orbiting around the cluster's center.

Past observations have shown that the heavyweight stars tend to crowd into the “downtown” core area, while lightweight stars reside in the less populated suburbs. But as heavyweight stars age, they rapidly lose mass, cool down and shut off their nuclear furnaces. After the purge, only the stars' bright, superhot cores – called white dwarfs – remain. This weight loss program causes the now lighter-weight white dwarfs to be nudged out of the downtown area through gravitational interactions with heftier stars.

Until these Hubble observations, astronomers had never seen the dynamic conveyor belt in action. The Hubble results reveal young white dwarfs amid their leisurely 40-million-year exodus from the bustling center of the cluster.

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