29 years ago, the Space Shuttle Discovery launched carrying a precious cargo: the Hubble Space Telescope
Each year this revolutionary telescope takes an image of a special object to commemorate the anniversary of its launch.
This year it has revisited an object it demystified over twenty years ago: the Southern Crab Nebula
The new, stunning image of this dynamic object
celebrates Hubble’s achievements, past, present, and future.
April has a unique significance in astronomy
because it marks the anniversary of the Hubble Space Telescope’s launch in 1990
from the Kennedy Space Center in the US.
A collaboration between ESA and NASA,
it was the first space telescope of its kind.
Since it began operating, Hubble has changed astronomy for ever.
It has transformed the way the public sees the universe
by presenting breathtaking and profound images of everything from newborn stars still in their nurseries
to the oldest known galaxies, formed over 13 billion years ago.
To celebrate its 29th birthday, Hubble dedicated some of its observing time
to capture a beautiful image of the Southern Crab Nebula
visible in the constellation of Centaurus.
The nebula is formed by the interaction of a pair of stars at its bright centre:
a red giant and a white dwarf.
The red giant is a star nearing the end of its life, shedding its outer layers of gas and dust.
The white dwarf’s gravity pulls some of this cast-off material around it.
When too much of this material builds up around the dead star for it to hold on to,
it is ejected in an eruption that creates the “bubbles” of gas and dust,
forming the hourglass shapes emanating out into space.
The presence of two nested shapes tells astronomers that the Southern Crab Nebula has erupted like this at least twice.
However, they did not always know this much detail about it.
When it was discovered in the 1960s, it was assumed to be an ordinary star.
It was only when ground-based telescopes at the European Southern Observatory were pointed at it in 1989,
that astronomers discovered an enigmatic object.
Their images of the object closely resemble a crab,
so they chose to incorporate this into its name.
It was called the Southern Crab Nebula
to distinguish it from the previously known Crab Nebula that is visible in the northern hemisphere.
In 1998, Hubble observed the object,
hoping that its greater imaging capabilities might be able to reveal the phenomenon that created it.
This image unveiled the second bubble and the bright active centre as distinct elements of the nebula.
Not only has our understanding of the object evolved over time,
but the Southern Crab Nebula itself is evolving as well.
There may even be more eruptions, forming more ‘“bubbles” of gas and dust.
Eventually, the red giant star at its centre will run out of fuel,
leaving behind its core in the form of a second dead white dwarf star.
What remains of its outer atmosphere will be left behind to form a planetary nebula,
a glowing shell of gas and dust expanding and dissipating into interstellar space.
This material will enrich the galaxy with the heavier elements formed inside the star during its lifetime,
including carbon, nitrogen, and oxygen.
Because transitions like these amount to only a tiny portion of the lives of stars,
it is rare to have the chance to observe such a system in flux.
This new anniversary image will give astronomers another data point
in the Southern Crab Nebula’s dynamic journey.
The power of Hubble has turned the Southern Crab
from an indistinct enigma into an exquisite structure —
something it has done for countless objects over the years.
Astronomers and the public alike owe Hubble a vote of thanks for telling the story of the Universe,
one observation at a time.