Hubble has now been in space for almost 30
years, and its mission has been a resounding success. It was never designed to look at objects in
our solar system, but that hasn’t stopped it from actually doing so over the course
of its mission, and as a result it has captured some very special moments we would have otherwise
missed. Not every planet has its own dedicated mission,
plus there is a lot to see besides just planets in our solar system. I’m Alex McColgan, and you’re watching
Astrum, and in this episode of the Hubble images series, we’ll look at some Hubble
snapshots of our solar system, and I’ll give you the context and an explanation of
the special moments it’s captured. Number 49. Asteroid 6478 Gault. It may surprise you to hear that this is an
asteroid, when it clearly looks like a comet. It’s even got two tails like we are used
to seeing on a comet. But no, this is in fact an asteroid found
in the asteroid belt, imaged this year. So, what’s with the tail? Well, it is believed that this 3.5 km wide
asteroid has been steadily speeding up its rotation due to something called the YORP
effect. Radiation from the Sun has a slight pushing
effect, meaning when it acts on an irregularly shaped body, under the right conditions it
can cause the body to speed up its rotation. Asteroid Gault’s rotation has gradually
sped up until it now rotates once every two hours, right on the limit of what an asteroid
can handle. Loose matter is being ejected into space by
centrifugal forces which are now overcoming the gravity of the asteroid. Eventually this asteroid will disintegrate
altogether, as most asteroids and comets are not solid rocks, but more like rubble piles. Which is very apparent in this next spectacular
image… Number 50. Comet Shoemaker-Levy 9 and Jupiter. Jupiter is sometimes referred to as the solar
system’s vacuum cleaner, and for good reason too. Jupiter by itself is so massive, it makes
up almost three quarters of all the mass in the solar system excluding the Sun. As a result, it has a powerful gravitational
effect on nearby objects. This was particularly evident when the 2km
wide comet Shoemaker-Levy passed too close to the gas giant in 1994. Jupiter’s gravity not only pulled the comet
in, it also ripped it apart, meaning by the time Shoemaker-Levy impacted Jupiter, it was
already in several different fragments. This was the first direct observation of an
extra-terrestrial collision. Interestingly, Shoemaker-Levy had been captured
by Jupiter around 20 years previously, but up until this point it was orbiting Jupiter
as an active comet, again, the first time this had been observed. However, this orbit took it too close to Jupiter’s
surface, where tidal forces pulled it apart, and only a year later these fragments impacted
Jupiter at 60km/s, or over 210,000kph. The impacts caused fireballs over 23,000°c,
which rose 3,000km above the limb of the planet. The largest impact left a dark spot on Jupiter
over 12,000km across, about the size of Earth, and the impact was estimated to have released
energy equivalent to 6,000,000 megatons of TNT, or over 600 times the world’s entire
nuclear arsenal put together. Various impacts, while perhaps not as impressive,
have been imaged since, and give weight to the theory of Jupiter being a cosmic vacuum
cleaner, protecting the inner solar system planets from devastating collisions. Number 51. The Moon. Now, the moon has a very big apparent diameter
in our sky, which means Hubble can’t fit the whole thing in in one go. Also, there are other missions out there which
capture far better images of the moon, like NASA’s Lunar Reconnaissance Orbiter for
instance, so Hubble’s time is better spent looking elsewhere. However, this image was taken in 2012, just
as Venus was passing in front of the Sun. So why image the moon? Scientist’s are using the Moon as a giant
mirror, to search for slight variations caused by sunlight being scattered through Venus’
atmosphere. These variations allow scientists to determine
the chemical composition of the atmosphere. Now, we already know the composition of Venus’
atmosphere, which means this was just a test to see if the light scattering experiment
produces accurate results. You see, Hubble often looks at distant stars
when an exoplanet is transiting in front of it, and it uses this process to determine
the composition of that exoplanet’s atmosphere. The Sun is too bright for Hubble to look at
directly, so light reflected off the moon provided the results scientists were looking
for. 52. Mars and Phobos. Mars is often imaged by Hubble, giving us
a full view of the entire disk, which can’t always be seen by orbiting spacecraft. In these images, Hubble can spot dust storms,
seasonal variations and other weather phenomena, important information to have for any rovers
on the surface, and to build up a catalogue of information which can be used to better
predict weather in the future. This time lapse shows a planet wide dust storm,
obscuring most of the surface features from view. However, you’ll also notice Mars’ two
moons, Phobos and Deimos, whizzing around the planet in the background. And they really are whizzing, look how far
they travel in just the 42 minutes this time lapse shows. Another time lapse shows Phobos, Mars’ closest
and largest moon, move over the course of 22 minutes. Phobos orbits the entire planet in only 7
and a half hours, meaning it is the only moon in the solar system to orbiter quicker than
a day on the parent planet. 53. Saturn and its inner moons. Since Cassini ended its mission in 2017, Saturn
has been without a dedicated mission. This means the best view we now have of Saturn
is courtesy of the Hubble Space Telescope. Hubble is often observing Saturn, checking
for various phenomena. Hubble can monitor the weather on Saturn,
giving us a better understanding of seasonal variations in the atmosphere. Cassini was only around Saturn for half a
Saturnian year, meaning Hubble is now filling in the remaining data as best as it can. The most notable events Hubble witnesses are
huge storms which span across thousands of kms on the planet. But because the Saturn system is such a beautiful
place, all the data collection also provides some striking shots. Here are a few of my favourites! 54. P/2010 A2. This looks like a pretty standard comet, wouldn’t
you agree? Have a close-up look at the nucleus though,
what is this weird filamentary structure? Surprisingly, this isn’t the shape of the
comet’s nucleus. Again, this isn’t even a comet. What you are looking at here is an extremely
rare event, it is two asteroids colliding. This X shape near the nucleus is in fact streamers
from the impact, rubble being flung into space in four directions, slowly being pulled back
in towards the centre of mass by the extremely weak gravity, with particles in the tail here
having escaped the gravity well altogether. Hubble has imaged a lot more from our solar
system, perhaps I will do another video capturing some more of what it’s seen. What’s amazing about Hubble is that even
though some places don’t have a dedicated mission at this point in time, it doesn’t
mean we are completely cut off from observing these places. We can check out storms happening on planets
millions of kilometres away, even witnessing events like a comet breaking apart and colliding
with a planet, or asteroids colliding with each other. And don’t worry, even though this mission
is approaching 30 years old, it’s not going anywhere anytime soon, latest estimates suggest
that Hubble will be with us until at least the 2030s. Want to get a deeper understanding of the
solar system and universe around us? I suggest giving Brilliant a go. Brilliant has interactive content that makes
solving puzzles and challenges about science and astronomy fun and hands-on, helping you
wrap your head around some of the more complex theories using real life examples and situations. This active learning combined with context
means that what you learn has a better chance of sticking with you throughout your life. Plus, they go into some really interesting
aspects of astronomy that will help you get a deeper appreciation of my videos! So, if you want to try it for yourself, you
can sign up for free today by using the link brilliant.org/astrum/ and that link will also
get you 20% off their annual Premium subscription to get unlimited access to all of Brilliant's
interactive math, science and computer science courses. Thanks for watching! If you liked this Hubble video, be sure to
check out the rest of the series in the playlist here. Also subscribe so you don’t miss out on
anymore in the future! For those of you that are Hindi or Spanish
speaking, be sure to check out the dedicated Astrum channels in those languages! Links in the description. All the best, and see you next time.
