One of the night sky’s most famous sights isn’t what it appears to be.
Perhaps the most famous sight of a dying star is the
Ring Nebula, known since 1779. The Ring Nebula appears to be an enormous gaseous ring surrounding a white dwarf star. This is representative of the fate of Sun-like stars that aren’t part of multi-star systems. Despite its appearances, this isn’t a true ring after all. (NASA, ESA, and C. Robert O’Dell (Vanderbilt University))
At just over 2,000 light years away, it is the closest dying star to Earth.
In between the 2nd and 3rd brightest stars of the constellation Lyra, the blue giant stars Sheliak and Sulafat, the Ring Nebula shines prominently in the night skies. (NASA, ESA, Digitized Sky Survey 2)
Upon observing it, Charles Messier wrote: “it is very dull, but perfectly outlined; it is as large as Jupiter & resembles a planet which is fading.”
This is where the term planetary nebula comes from: where dying stars blow off their outer layers.
The elements of the periodic table, and where they originate, are detailed in this image above. While most elements originate primarily in supernovae or merging neutron stars, many vitally important elements are created, in part or even mostly, in these planetary nebulae like the Ring Nebula. (NASA/CXC/SAO/K. Divona)
But despite looking very much like a ring to our eyes, the Ring Nebula is anything but.
Planetary nebulae take a wide variety of shapes and orientations depending on the properties of the stellar system they arise from, and are responsible for many of the heavy elements in the Universe. Supergiant stars and giant stars entering the planetary nebula phase are both shown to build up many important elements of the periodic table via the s-process. (NASA, ESA, and The Hubble Heritage Team (STScI/AURA))
A huge, diffuse set of hydrogen shells surround it, showcasing the material blown off as the star dies.
The red outer shells are signs of ionized hydrogen gas, huge and intricate outside the ring itself. Sulfur and Oxygen ions, expelled from the star and prominent in the ring area, are viewed in the other colors shown here. (D. López (IAC), which is A. Oscoz, D. López, P. Rodríguez-Gil and L. Chinarro)
Along our line-of-sight, two lobes of low-density gas extend towards and away from us.
The Helix Nebula, a similar planetary nebula (with a donut-shaped appearance) to the Ring Nebula, has also had its 3D structure mapped out, and it is far more intricate than a simple ring explanation would indicate. (NASA, ESA, C.R. O’Dell (Vanderbilt University), and M. Meixner, P. McCullough, and G. Bacon ( Space Telescope Science Institute))
We are viewing this structure almost directly down one of its poles, which explains its ring-like appearance.
The Spitzer Space Telescope, looking in infrared light, showcases the temperature of different portions of the Ring Nebula. The inner regions are far hotter, which explains why they’re far brighter, as it’s the electrons falling down in their orbitals that causes the emission of the light that we can see. (NASA/JPL-Caltech/J. Hora (Harvard-Smithsonian CfA))
In 2013, astronomers used new Hubble data to map out the nebula’s 3D structure.
This schematic shows the geometry and structure of the Ring Nebula (Messier 57) as viewed side-on. This shows the nebula’s wide halo, inner region, lower-density lobes of material stretching towards and away from us, and the prominent, glowing disc. (NASA, ESA, and A. Feild (STScI))
The reflective, high-density gas is all most telescopes can see.
Through a modest-sized telescope at a dark-sky site, this is what the Ring Nebula will appear to look like through an eyepiece to a human observer. The origin of the name ‘Ring Nebula’ is apparent, but the true story is far more revealing. (Chris Spratt)
But we now know it isn’t a ring at all, but also displays intricate structure, with an outer halo, inner turbulence, lobes and knots.
The different elements (in different colors), the neutral knots of gas(dark globs), and the translucent hue of the inner ring are allartifacts of viewing this intricate 3D structure face-on. The RingNebula is no ring at all, nor is it spherical in shape. Its true nature isfar more complex, and has taken a variety of observations to reveal.(NASA, ESA, and C. Robert O’Dell (Vanderbilt University))
This may be exactly the fate awaiting our Sun in the future.
Mostly Mute Monday tells the science story of an astronomical object, image, or phenomenon in visuals and no more than 200 words. Talk less, smile more.