TITLE: The best images of Pluto we have ever seen
Astronomer Edward Barnard was training the Yerkes Observatory's Bruce photographic telescope
on a portion of the sky constellation Taurus.
He wasn’t looking for planets, but that night in November 1909, he took a wide field
exposure for one hour and 19 minutes, surveying a region around Halley's comet.
Then he stored the plate and recorded the data in his logbook.
What happened though is that, nearly 100 years later, astronomers at Yerkes looked again
at Barnard’s photographic plate from November 11, 1909, and another taken on August 21 of
that year and found what they believe are the earliest known pictures of Pluto, exposed
21 years before the planet was even discovered.
Astronomers used a tool, called MegaStar sky atlas software, that gives a precise position
for Pluto at any date past or future, based on current orbital data.
By overlaying the simulated MegaStar position on the 1909 photos, they found tiny dots—nearly
at the limit of what can be distinguished from the photographic grain of the old plates—at
the same position.
Another team reexamined the 1909 plates and compared them to modern Palomar sky survey
photos of the same part of the sky. The results were slightly ambiguous, complicated
by the fact that the Palomar images show faint stars at nearly the same position as the claimed
Pluto. But on the November 11 exposure, they seemed to see a faint elongated image at the
indicated position of Pluto and they consider this identification fairly certain.”
Whether that was Pluto or not, a long time has passed since these pictures were taken,
and today we have CCDs instead of photographic plates, that perform much better!
This animation from NASA combines various observations of Pluto over the course of several
decades. The first frame is a digital zoom-in on Pluto as it appeared upon its discovery
by Clyde Tombaugh in 1930. The other images show various views of Pluto as seen by NASA's
Hubble Space Telescope beginning in the 1990s and NASA's New Horizons spacecraft in 2015.
The final sequence zooms into a close-up frame of Pluto released on July 15, 2015.
New horizons literally revolutionized our understanding of Pluto, and therefore, our
understanding of the Solar System, the place in the universe we are living in.
what's Pluto, where it is found, and why is it a dwarf planet.
Pluto is a frigid world, billions of kilometers from Earth, and 30 times less massive than
the then-smallest known planet, Mercury. But Pluto was not alone. It was found to have
five satellites. The largest, Charon, was discovered in 1978. The smaller four were
discovered using the Hubble Space Telescope in 2005, 2011, and 2012 and officially named
Nix, Hydra, in early 2006, Kerberos and Styx in 2013 by the International astronomical
union.
The International Astronomical Union was also responsible for the decision of Pluto not
to be a planet. The final resolution, after a bunch of draft
proposals, came out at the end of the Prague General Assembly, held in 2006. The definition
of a planet in the Solar System would be as follows:
A celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity
to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape,
and (c) has cleared the neighborhood around its orbit.
This final resolution means that Pluto cannot be classified as a planet, because it doesn't
fulfill the third criterion.
Nowadays, Pluto is considered a dwarf planet. In 2006 people at NASA decided that they wanted
to know more about Pluto, its shape, and its atmosphere and geology.
So they designed a specific mission with the aim of exploring Pluto. It was called New
Horizons, and in 2006 it was launched. The mission's goal was to get to Pluto as
soon as possible, and this is also the reason why New Horizons was launched by means of
an Atlas V rocket.
The mission launched on Jan. 19, 2006, and began its journey to Pluto.
To reach Pluto, the mission designers decided to use a Jupiter gravitational assist.
Basically, New Horizon would have swung past Jupiter for a gravity boost to get on the
right path for Pluto, with the desired velocity, thus saving fuel.
So, although the mission was primarily designed for Pluto, the first encounter New Horizons
had was the one with Jupiter. This was a unique occasion to test the instruments
and camera onboard and to conduct the first scientific studies.
For example, this is a mosaic of three New Horizons images of Jupiter's Little Red Spot,
taken with the spacecraft's Long Range Reconnaissance Imager (LORRI) camera on February 26 from
a range of 3.5 million kilometers. The image scale is 17 kilometers per pixel, and the
area covered measures 33,000 kilometers from top to bottom, two and one-half times the
diameter of Earth.
The Little Red Spot, a smaller cousin of the famous Great Red Spot, formed in the past
decade from the merger of three smaller Jovian storms, and is now the second-largest storm
on Jupiter. About a year ago its color, formerly white, changed to a reddish shade similar
to the Great Red Spot, perhaps because it is now powerful enough to dredge up reddish
material from deeper inside Jupiter. These are the most detailed images ever taken of
the Little Red Spot since its formation.
LORRI took the images as the Sun was about to set on the Little Red Spot. The LORRI camera
was designed to look at Pluto, where sunlight is much fainter than it is at Jupiter, so
the images would have been overexposed if LORRI had looked at the storm when it was
illuminated by the noonday Sun. The dim evening illumination helped the LORRI camera obtain
well-exposed images. The nice thing here is that the New Horizons team used predictions
made by amateur astronomers in 2006, based on their observations of the motion of the
Little Red Spot with backyard telescopes, to help them accurately point LORRI at the
storm.
On January 15, 2015, the spacecraft began its approach phase to Pluto and, as it was
getting closer, the pictures were getting better. The image resolution was something
amazing, and astronomers began to understand what a major revolution this mission was about
to make.
New Horizons conducted scientific studies of Pluto in the summer of 2015, culminating
with Pluto's closest approach on July 14, 2015.
However, it should be said that this mission was not simple at all!
New Horizons' team experienced a software anomaly, and the probe went into safe mode,
preventing the spacecraft from performing scientific observations until engineers could
resolve the problem. On July 5, NASA announced that the problem was determined to be a timing
flaw in a command sequence used to prepare the spacecraft for its flyby, and the spacecraft
would resume scheduled science operations on July 7. Thankfully, the science observations
lost because of the anomaly were judged to have no impact on the mission's main objectives
and minimal impact on other objectives.
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So, what did New Horizons find out about Pluto? Before New Horizons, we knew Pluto was small
and we only had blurred pictures of it. After new Horizons, we knew Pluto had mountain
ranges, ice plains, glaciers, and even an atmosphere!
The mountains likely formed no more than 100 million years ago -- mere youngsters relative
to the 4.56-billion-year age of the solar system -- and may still be in the process
of building. That suggests the close-up region, which covers less than one percent of Pluto’s
surface, may still be geologically active today.
CLOSE-UP IMAGE:
How do scientists know about the age of these mountains?
Well, they look around and search for craters. Like the rest of Pluto, this region would
presumably have been pummeled by space debris for billions of years and would have once
been heavily cratered -- unless recent activity had given the region a facelift, erasing those
pockmarks. And indeed, we can't find a lot of craters around.
Although methane and nitrogen ice covers much of the surface of Pluto, these materials are
not strong enough to build the mountains. Instead, a stiffer material, most likely water
ice, created the peaks. In fact, at Pluto’s temperatures, water-ice behaves more like
rock.
But the cutest thing New Horizons showed us is that Pluto has a thin, tenuous atmosphere.
This atmosphere expands when it comes closer to the Sun and collapses as it moves farther
away – similar to a comet. The main constituent is molecular nitrogen, though molecules of
methane and carbon monoxide have also been detected.
When Pluto is close to the Sun, its surface ices sublimate (changing directly from solid
to gas) and rise to temporarily form a thin atmosphere. Pluto's low gravity is about 6%
of Earth's, and therefore it causes the atmosphere to be much more extended in altitude than
our planet's. This is a picture of Pluto's atmosphere when
backlit by the Sun. The blue color is close to what a human eye
would have seen and is caused by layers of haze in the atmosphere.
If you think about it, this sight is similar to the one astronauts can see every day on
the international space station, only they are looking at the atmosphere of the Earth.
For example, here's a view of Pakistan and India.
NASA decided to also look at Charon. Charon is one of Pluto's moons, actually,
it is the largest one, and it is literally dancing around Pluto.
Well, not actually. Pluto and Charon orbit around their common center of mass, which,
given the small size of Pluto, is a point in the space between the two objects.
Around the dancing couple are four small moons, called Styx, Nix, Kerberos, and Hydra.
All four small moons are less than 50 kilometers in their longest dimension. Each has a lumpy
shape because, unlike Pluto and Charon, they aren’t big enough for gravity to squish
them into a ball.
From looking at Nix as a point of light with the Hubble Space Telescope and with New Horizons
on approach, we knew that Nix’s brightness regularly changed over time, and therefore
it was probably elongated. However, the first image (on the left) really surprised us, because
Nix appeared to be round—not at all elongated.
But this was just because we were looking down the long axis.
The following images would look more “potato-ish.” And also, scientists realized that seen from
a different perspective, Nix presented a crater. Nix isn’t very large, and there is a very
fine line between an impact that will make a crater that big and one that will break
Nix apart. So either Nix was very lucky in surviving that collision, or it’s a fragment
of an older moon that was somehow destroyed.
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As part of an extended mission, pending NASA approval, the spacecraft is expected to head
farther into the Kuiper Belt to examine another of the ancient, icy mini-worlds in that vast
region, at least a billion miles beyond Neptune’s orbit.
Anyway, once studied Pluto and its system, New Horizons' mission was extended.
The spacecraft continued its unparalleled voyage on New Year’s 2019 with the exploration
of Arrokoth – which the team had nicknamed “Ultima Thule” ­-- a billion miles beyond
Pluto, and the farthest flyby ever conducted.
But what's Arrokoth? Well, first of all, it is worth saying that
the team didn't know about the existence of this object before New Horizon was launched:
this object was located and selected for New Horizons to visit after Pluto,
New horizons were healthy and well after Pluto, and NASA's team decided to adjust its course
so it could Reach Arrokoth.
New Horizons flew by Arrokoth on Jan. 1, 2019, snapping images that showed a double-lobed
object that looked like a partially flattened snowman. It’s also very red — even redder
than Pluto. The object's strange shape — unlike any ever seen — was the biggest surprise
of the flyby. Here's a picture of it:
Arrokoth orbits in the Kuiper Belt, a region in the outer solar system that is full of
icy and ancient objects. Because they are so far from the Sun, Kuiper Belt objects have
only been slightly heated since forming, and are thought to be well-preserved, frozen samples
of what the outer solar system was like after its birth more than 4.5 billion years ago.
So probably, the two pieces of Arrokoth merged together when our solar system and the planets
were forming. The merge could therefore give us insights into how fragments, dust, and
rocks get together and form planets!
Thanks, New Horizons!
Thanks for watching everyone! What do you guys think about this video? Let
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