This episode of Primal Space is supported by CuriosityStream. Watch thousands of documentaries for free
by visiting curiositystream.com/primalspace On the 24th of April, 1990, Space Shuttle
Discovery launched the Hubble telescope into orbit. This was an exciting time for space exploration, as Hubble promised to produce mind boggling images, showing us an early view of our universe
as it was forming. But as soon as Hubble came online, scientists
noticed a serious problem with its mirror. Although this was the most precisely cut mirror
ever made, a slight defect of just 2,000 nanometers meant that Hubble failed to produce sharp
images. After 3 years, scientists managed to produce
a fix for the mirror and Hubble began scanning the universe for its secrets. Since then, Hubble has operated for nearly
30 years, capturing the most stunning images of distant stars and galaxies. But like everything, Hubble has its limits,
and the world's most famous telescope will eventually come to an end in the not-too-distant
future. But how long does it have left? And why has it reached a limit in terms of
what it can observe? Throughout its lifetime, Hubble has taken
millions of amazing pictures. It’s able to observe other parts of the
electromagnetic spectrum that an ordinary telescope couldn’t see. Since it’s outside of Earth’s atmosphere,
it has an unobstructed view of the universe which allows it to capture objects that are
dimmer and much more distant than a ground-based telescope ever could. Despite this, Hubble’s best images have
come and gone, and the limitations of physics will likely stop it from seeing anything dimmer
or further than it already has. In order to observe the furthest and dimmest
objects in the universe, you need a telescope with an extremely high resolution and the
ability to capture as much light as possible. The resolution of a telescope
is limited to the number of wavelengths it can fit across its mirror. The angular resolution of a telescope measures
its ability to identify two separate objects that have a short angular distance when observed
by a telescope. This is given by 1.22 multiplied by the wavelength
of the light over the diameter of the mirror. When observing visible light of about 500nm,
Hubble has an angular resolution of about 0.05 arcseconds. This beats the human eye’s resolution by
a factor of 1000. For even shorter wavelengths like ultraviolet,
the resolution gets even better and Hubble can achieve an angular resolution as low as
0.01 arcseconds. Hubble is also limited by the types of wavelengths
it can observe. Stars emit a wide range of light, and although Hubble can observe a wide range of wavelengths, it can’t observe anything
greater than near infrared. This limits its ability to look back in time
to distant objects. As the universe expands, the fabric of space expands with it. When light travels through the universe, its wavelength is stretched with the expansion of space. This means that by the time the light arrives
at Hubble, the wavelength of the light is longer than when it left the object. This is known as red shifting. As the distance to an object increases the
longer its light will spend travelling through space and the more red-shifted it will get. If the light is redshifted too much, it could
be stretched to a wavelength outside of Hubble’s viewing range. One of the main goals of the Hubble telescope
was to find the most distant Galaxy in the known universe. It achieved this in 2016, when it discovered
Galaxy GN-Z11. This galaxy is located 32 billion light-years
away and the light we see from it shows the Galaxy as it was 13.4 billion years ago, just
400 million years after the Big Bang. This Galaxy is at the very limit of how far
into the past Hubble can see, and it was discovered due to some incredible circumstances. The Galaxy just so happens to be in an area
of the universe where there is very little neutral gas between it and Hubble. This gave the telescope a clear view to observe
the Galaxy. The light coming from the Galaxy
passed by another nearby Galaxy which caused it to be gravitationally lensed. This happens when the light from an object is bent by the gravitational pull of another object. Light that would otherwise miss the observer is bent in a away which directs it towards the observer. This caused the light from Galaxy GN-Z11 to be magnified, just enough for Hubble to observe it. So far, Hubble has been capturing these stunning
images for 29 years. Due to it’s design, Hubble was capable of
being serviced in orbit. Over the years, the Space Shuttle crew visited Hubble on 5 separate missions to fix and replace faulty components. However, since the Shuttle program ended in 2011, we no longer have the ability to maintain Hubble, which is starting to take its toll
on the telescope. Hubble has 6 gyros onboard which it uses to
maneuver and point its telescope precisely towards its target. In the last 5 years, 3 of these gyros have
failed. Even if Hubble continues to function over
the next decade, its orbit is constantly decaying and in the 2030’s Hubble will crash into
the atmosphere and burn up before reaching the ground. By the time this happens, the next generation
of space telescopes will be in orbit, producing even more stunning images of our universe. But Hubble’s groundbreaking images will
never be forgotten. So although Hubble will be decades old before
it retires, it’s existence will be a mere flash compared to the age of the objects it
managed to capture. Nevertheless, the incredible engineering and
science behind this telescope helped us take an enormous step forward in our understanding
of the universe. If you’d like to watch more about Hubble,
check out this documentary on CuriosityStream which looks at the process of turning Hubble’s
data into stunning images like this. CuriosityStream is a streaming service with
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featuring the likes of Stephen Hawking and David Attenborough. You can watch them all for free by visiting
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