Hubble captures intricacies of R Aquarii
The NASA/ESA Hubble Space Telescope has provided a dramatic and colourful close-up look at one of the most boisterous stars in our galaxy, weaving a huge spiral pattern among the stars. Hubble's images capturing its details and its evolution are featured by a unique timelapse video.
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Residing only roughly 700 light-years from Earth in the constellation Aquarius, R Aquarii is a symbiotic binary star: a type of binary star system consisting of a white dwarf and a red giant that is surrounded by a large, dynamic nebula. As the closest symbiotic star to Earth, R Aquarii was studied by none other than Edwin Hubble in an effort to understand the mechanism that powers the system.
R Aquarii undergoes violent eruptions that blast out huge filaments of glowing gas. This dramatically demonstrates how the Universe redistributes the products of nuclear energy that form deep inside stars and jet back into space.
R Aquarii belongs to a class of double stars called symbiotic stars. The primary star is an aging red giant and its companion is a compact burned-out star known as a white dwarf. The red giant primary star is classified as a Mira variable that is over 400 times larger than our Sun. The bloated monster star pulsates, changes temperature, and varies in brightness by a factor of 750 times over a roughly 390-day period. At its peak the star is blinding at nearly 5000 times our Sun’s brightness. When the white dwarf swings closest to the red giant along its 44-year orbital period, it gravitationally siphons off hydrogen gas. This material accumulates on the dwarf star’s surface until it undergoes spontaneous nuclear fusion, making that surface explode like a gigantic hydrogen bomb – a so-called nova [1]. After the outburst, the fueling cycle begins again.
These events have more than just a passing interest to astronomers and laymen alike in that this is one known way – as well as the truly titanic but extremely rare supernova events – to release chemical elements heavier than hydrogen and helium into the interstellar medium. Heavier elements like carbon, nitrogen, and oxygen are critical building blocks of planets like Earth and lifeforms such as our own. They are formed in the deep interiors of stars, where the temperature is high enough to fuse hydrogen and helium.
This outburst ejects geyser-like filaments shooting out from the core, forming loops and trails as the plasma emerges in streamers. The plasma is twisted by the force of the explosion and channeled upwards and outwards by strong magnetic fields. The outflow appears to bend back on itself into a spiral pattern. The filaments are glowing in visible light because they are energized by blistering radiation from the stellar duo that is R Aquarii. The nebula around the binary star is known as Cederblad 211, and may be the remnant of a past nova.
The scale of the event is extraordinary even in astronomical terms since emitting material can be traced out to at least 400 billion km – or 2500 times the distance between the Sun and Earth – from the central core.
The ESA/Hubble team has developed a unique timelapse of the object consisting of multiple observing programmes that span from 2014 to 2023. Across the five images, the rapid and dramatic evolution of the binary star and its surrounding nebula can be seen. The binary star dims and brightens, seen by the size of the red diffraction spikes around it, due to the strong pulsations of the red giant star. The nebula is shown in mostly green colours, but bluer parts of it come in and out of view: this is because they are being illuminated as the lighthouse-like beam of light from the spinning binary star sweeps over them.
Notes
[1] A nova, from the Latin stella nova meaning 'new star', is the temporary appearance of a new and bright star in the sky. The 'new' star is actually a white dwarf in a close binary system, which has temporarily greatly increased in brightness due to a thermonuclear explosion at its surface; this explosion is what astronomers refer to as a nova. A supernova gets its name from the same source, but is a somewhat different and much more energetic astrophysical phenomenon.
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The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
The Hubble observations featured in this release include those from program 16312 (PI: M. Karovska), 16055 (PI: M. Karovska), 14847 (PI: M. Karovska), and 13339 (PI: M. Stute).
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