Some stars die a beautiful death, ejecting their outer layers of gas into space, then lighting it all up with their waning energy. When that happens, we get a nebula. Astronomers working with the Gemini Observatory just shared a new image of one of these spectacular objects.
It’s called CVMP 1 and it’s a planetary nebula, a somewhat confusing term that comes from a time when astronomers saw them in space and weren’t sure what they were. Planetary nebula have nothing to do with planets, but through the viewfinders of historic telescopes they were round and appeared to be planets.
CVMP 1 is about 6500 light years away in the constellation Circinus, or The Compass. As a star ages, it exhausts the hydrogen in its core, and then switches to fusion of hydrogen in its shell. When that happens it grows in volume and cools, turning red, or reddish-orange. At that point, it’s a red giant.
Depending on the initial mass of the star, it can through several fusion phases, and in some cases it sheds its outer material like CVMP 1’s progenitor star did. In that case, only the core of the star remains, to light up all of the ejected material as a planetary nebula.
The display won’t last long, in astronomical terms. CVMP 1 will only sustain this stellar light show for about 10,000 years, a mere blink of an eye to a star. Eventually, the core remnant of the star will run out of fuel and cool. Once that happens, it’ll no longer give off enough ultraviolet energy to ionize the expelled gas and light it up. As the star cools, and as the expelled outer shell of the star travels further and further away, the display comes to an end.
CVMP 1 has a peculiar hourglass shape that earned the nebula its nick-name: the Hourglass Nebula. Many nebulae have these types of nicknames because of the wide variety of shapes they come in. The characteristics of the progenitor star, or stars, influences the nebula’s shape. A nebula created by a binary star system looks different than those spawned from single stars. The nebula is also shaped by any planets that orbit the star, and the rotation rate of the progenitor star. Astronomers don’t have a total understanding of all the factors that shape a planetary nebula.
Though visually stunning, the Hourglass Nebula is of interest to astronomers for other reasons. Astronomers who studied the nebula say that the gases in the hourglass shape are highly enriched in helium and nitrogen. It’s also one of the largest planetary nebula ever observed. Those observations together suggest that it’s one of the most highly-evolved planetary nebula that we know of. That’s giving astronomers an opportunity to study the later stages in the lives of planetary nebula.
Astronomers have studied the progenitor star in the center of this light show and they say that it has a core temperature of at least 130,000 degrees C (230,000 degrees F). For comparison, our Sun’s core temperature is near 15 million degrees C (27 million degrees F). The star in CVMP 1 has cooled considerably already, and will continue to cool. It’ll take a long time, but eventually the star will fade to nothing.
After it cools sufficiently, the star at the center of this display will become a white dwarf, just a pale remnant of the star that once lit up its surroundings. That usually takes about 10,000 years, and when that much time has passed, there’ll only be a tiny white dot left. But that doesn’t mean something important hasn’t happened.
Along with being beautiful, planetary nebulae play an important role in the cosmos. As the star at the center evolves, it synthesizes heavier elements, heavier than the hydrogen and helium that it formed out of. And as it sheds its outer layers, its spreads those heavier elements out into space, to be taken up in the next cycle of star and solar system formation. Without these heavier elements—called metals in astronomy—life could not exist.
The Gemini Observatory is not a single facility. It’s a network of telescopes around the world. They cover both the northern and southern hemispheres, and together they can see the entire sky. A fraction of the observing time is dedicated to obtaining images like this one of CVMP 1, purely for our enjoyment and interest.
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