[ad_1]
Search box title
Astronomers caught a rare glance at a rapidly fading shroud of gas around an aging star. Archival data from NASA’s Hubble Space Telescope reveals that the Hen 3-1357 nebula, nicknamed the Stingray Nebula, has been precipitously erased over the past two decades. To witness such a rapid rate of change in a planetary nebula is extremely rare, say the researchers.
Images captured by Hubble in 2016, compared to Hubble images taken in 1996, show a nebula whose luminosity has dramatically decreased and changed shape. The bright blue fluorescent tendrils and gas filaments towards the nebula’s center are all but gone, and the wavy edges that earned this nebula its aquatic-themed name are all but gone. The young nebula no longer appears against the black velvet background of the vast universe.
“It’s very, very dramatic and very strange,” said Martín A. Guerrero, team member at the Instituto de Astrofísica de Andalucía in Granada, Spain. “We are witnessing the evolution of a nebula in real time. In a few years, we see variations in the nebula. We’ve never seen this before with the clarity we get from this point of view. “
Researchers have discovered unprecedented changes in the light emitted by glowing nitrogen, hydrogen and oxygen projected by the dying star at the center of the nebula. Oxygen emission, in particular, dropped in brightness by a factor of almost 1,000 between 1996 and 2016.
“Changes in the nebulae have already been observed, but what we have here are changes in the fundamental structure of the nebula,” said Bruce Balick of the University of Washington in Seattle, head of new research. “In most studies, the nebula usually gets bigger. Here, it fundamentally changes shape and weakens, and on an unprecedented time scale. Also, to our surprise, it doesn’t get bigger. This is because the once shiny inner elliptical ring seems to shrink as it fades.
Ground observations of other planetary nebulae have shown evidence of changes in brightness over time, but such speculations have so far not been confirmed. Only Hubble can resolve the changes in the structure of this tiny nebula. The new article examines every image of the Stingray Nebula from the Hubble Archives.
“Due to the optical stability of Hubble, we are very, very confident that this nebula will change in brightness over time,” Guerrero added. “This is something that can only be confirmed with Hubble visual acuity.”
The researchers note that the nebula’s rapid changes are a response to its central star, SAO 244567, which expands due to a drop in temperature and in turn emits less ionizing radiation.
A 2016 study by Nicole Reindl, now of the University of Potsdam, Germany, and a team of international researchers, also using Hubble data, noted that the star at the center of the Stingray nebula, SAO 244567, is special in itself.
Observations from 1971 to 2002 showed the star’s temperature to soar from less than 40,000 to 108,000 degrees Fahrenheit, more than ten times hotter than our Sun’s surface. Now, Reindl and his research team have shown that SAO 245567 cools. Reindl believes the temperature jump was caused by a brief flash of helium fusion that occurred in a shell around the core of the central star. Recently, the star appears to be going back to its first stage of stellar evolution.
“We’re very lucky to be watching him right then,” Reindl said. “In such a flash of helium it evolves very quickly and it involves short evolution timescales, so we usually can’t see how these stars evolve. We were just there at the right time to understand this.
The team studying the rapid fading of the Stingray Nebula can only speculate at this time about what awaits for the future of this young nebula. At its current rate of fading, it is estimated that the nebula will be barely detectable in 20 or 30 years.
The Hubble Space Telescope is an international cooperation project between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland operates the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts science operations at Hubble. STScI is operated for NASA by the Association of Universities for Astronomical Research in Washington, DC
[ad_2]
Source link