Astrophoto: The Goldilocks Variable in the Dumbbell Nebula by Stefan Heutz

We are very fortunate, and perhaps lucky, to inhabit a planet near a star whose behavior has been relatively monotonous for billions of years. This is a vital quality of any star to spawn and support life. But, there are many suns that do not have this characteristic. These suns regularly increase their radiance by outpouring dramatic amounts of additional energy such as the Goldilocks variable star that can sometimes be seen in images of the Dumbbell Nebula, pictured here.

During our Sun’s eleven year sunspot cycle, the amount of radiation released changes by only about 0.1 percent. This is an important behavior for stars to sustain habitable environments. They need to be constant over the millennia. Most stars are stable, but a significant minority experience large changes in their luminosity that would have consequential effects on nearby orbiting planets and any life that they may attempt to harbor. These are known as variable stars and they have been useful for helping scientists deduce the mass, temperature and internal makeup of stars in general. Variable stars have also enabled astronomers to measure the distance to remote galaxies and understand the age of the universe.

One of the most famous variable stars, designated Omicron Ceti, is also known as Mira and it can be found in the constellation Cetus. In the late 1500’s, an amateur astronomer discovered that this star’s brightness slowly pulsated over a long period of time. It rivaled Aldebaran (the brightest star in the constellation Taurus) when it was at peak brilliance but it could also become forty times dimmer than the human eye can detect during a 330 day cycle. Mira is a bloated star twice as wide as the orbit of Mars. It is an old star near the end of its useful life having converted much of its original hydrogen into heavier elements. Its brightness variation is the result of Mira changing size and temperature.

There are thousands of stars that behave similarly to Mira, and one of them was discovered in 1988 by a Czech amateur astronomer, Leos Ondra, while studying the stars in and around our view of the Dumbbbell Nebula. While researching through books, journals and star charts, he noticed that this star was sometimes visible in pictures but occasionally it was noticeably absent. After confirming that it was not a photographic artifact, he concluded that the star, arrowed in the accompanying image, had a long period between its bright and dim extremes. He privately referenced it Goldilocks in honor of a young lady he admired at the time and the name has stuck.

Over the next few years his discovery was confirmed by careful observation and the star was found to be similar to Mira- bloated, near the end of its useful output and going through an expansion and contraction cycle that lasted 213 days. Click here and you will see the difference in this star’s appearance over a one year period between 2005 and 2006- be patient while both images load into your browser. It should be noted that the Goldilocks variable star is not within the Dumbbell Nebula- nor are most of the other stars that can be seen. It is located much farther in the distance and can be seen because the closer nebula is partially transparent.

The Dumbbell Nebula is, itself, the outer shell of a star that has ended its useful life- all that remains is this expanding shroud of material and the star’s exposed inner core, near the center, which is slowly cooling and fading to black. This nebula is located in the northern constellation of Vulpecula and is approximately 300 light years from Earth.

This spectacular image was produce by European astronomer Stefan Heutz on June 17, 2006 from his backyard imaging location though a 10.5 inch Cassegrain telescope and a 1.5 mega-pixel camera. It required an exposure of almost three hours.

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Written by R. Jay GaBany