The Discovery of 'Planet' Ceres

For a long time, astronomers believed that there must have been a planet lurking in the gap between Mars and Jupiter. What they found was Ceres, and this object's story is one of scientific cattiness and our ever-evolving understanding of space.

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Episode Transcript

Speaker 1 (00:01):
Welcome to steph you missed in history class from how
Stuff Works dot com. Hello, and welcome to the podcast.
I'm Holly Fry and I'm Tracy Wilson, and I have
to confess up front that UM and I might offend
people by saying this a little bit. The impetus for

(00:24):
this episode is because I can get a little cranky
and fussy about people who are still campaigning to get
Pluto back as a planet. Yeah, doesn't have feelings. I
don't think people do. Is personally hurt by having been
no longer well, and some of it for me, it's

(00:47):
just that like there are there are rules and reasons.
There's still a debate that can certainly happen, but there
are rules and reasons, and it it's explained why it
was made a dwarf planet, and people will come back
and say it shouldn't matter that it's small. It's still
a planet, and it's like, hey, that doesn't have anything
to do with it. So, but we're not talking about Pluto.

(01:07):
We've done that before. But instead we're going to talk
about some other heavenly bodies that had a similar kind
of uh discovery misclassification shift. It's kind of you know,
I wanted to talk about how like our our knowledge
and our what we believe to be true, and how
we lay out our knowledge of the universe, and the

(01:29):
Solar System specifically changes all the time based on new information.
So in eighteen hundred there were only seven known planets
in the Solar System, and at that point it was Mercury, Venus, Earth, Mars, Jupiter, Saturn,
and Uranus. Wondering if there might be a planet in
between Mars and Jupiter had really taken up headspace for
a lot of astronomers up to that point. Once Uranus

(01:52):
was discovered in seventy one by Sir William Herschel, it
validated a theory that indicated that there should be sort
of regular space seeing between the orbital ellipses of planets,
and this gave astronomers even stronger conviction that there must
be a planet there in that swath of space between
Mars's orbit and Jupiter's orbit, but no one had identified

(02:13):
a planet there. Uh. Johannes Kepler even theorized about a
planet in that gap between those two planets in fix
in his work Mysterium Cosmographicum, and he actually hinted that
there would be more than one they're writing quote. Yet
the interposition of a single planet was not sufficient for
the huge gap between Jupiter and Mars. Plenty of astronomers

(02:36):
dedicated huge chunks of their careers to try to find
this elusive planet that they felt absolutely must be lurking
in that empty swath of space, but to no avail.
But eventually an Italian astronomer who was really a mathematician
found something. And today we're going to talk about the
celestial object series, the man who spotted in, what it is,

(02:58):
what it's been in terms of nomenclature, and how science shifts,
it shifts it's thinking as new information is uncovered. To
talk about series, we're going to talk a little bit
about Giuseppe Piazzi. He was born on July sixteenth, seventeen
forty six, so we are coming up on his birthday.
He was one of ten sons, and his parents, who

(03:19):
lived in Ponti in Baltalina in the north of Italy,
were really well off financially because many of his siblings
had died when they were still very young. Giseppe was
baptized in a very quick home ceremony, with the official
record quote because of impending danger of death, and though
his parents had been fearful of his health, Giuseppe grew

(03:42):
to adulthood and at the age of nineteen, as was
often customary for wealthy sons, he took holy orders to
become a priest, and he pursued a number of academic
studies and eventually, starting in seventeen seventy, at the request
of the church, he began teaching philosophy and mathematics as
a touring lecturer throughout Italy. In seventeen eighty one, he

(04:03):
became the chair of mathematics at a new educational institution
that would eventually become the University of Palermo. Six years later,
he was named chair of astronomy at the school. This
is an interesting move because he hadn't really been a
studying astronomy for that all that long, but he was
a really devoted scholar, and astronomy would eventually become the

(04:26):
thing that he was known for. In early seventeen eighty seven,
the same year that he was named chair of astronomy,
Piazza began an intensive three year study trip so that
he could really become as familiar with astronomy as he could,
and during that time, he spent time in Paris and London,
and he became the colleague and friend of astronomers in

(04:46):
both of those cities. It was because of these connections
and the study that he was able to secure a
five foot circular scale altesimus telescope that would become a
crucial component of the observatory that he had been tasked
with build ing at the University. That telescope was made
in London by mathematician and astronomical instrument specialist Jesse Ramsden.

(05:08):
When Piazzy returned to Palermo at the end of seventeen
eighty nine, he focused entirely on the construction of the observatory,
and it was only a matter of months before it
was completed. It was built on top of a tower
at the Royal Palace. With his new observatory completed and
this impressive telescope telescope installed, Justessette set to work making observations,

(05:31):
focusing primarily on accurately mapping the positions of stars, and
this mapping effort was truly painstaking. Each star had to
be observed for a minimum of four nights, and this
had to be done for each observable star. This work
would eventually culminate in the publication of a star catalog
in eighteen o three, which one Piazza an array of accolades.

(05:54):
But while he was mapping all those stars, he stumbled
across something else entirely. So it's a little early normally
for a break for a sponsor, but we want to
keep this next section altogether, So we're gonna pause here
and have a little sponsor break, and then we will
come back and talk about what it was that Piazzi
stumbled upon. On New Year's Day eighteen o one, Piazzy

(06:23):
noticed a tiny dot in the heavens, specifically in the
shoulder of the Taurus constellation, as was his method. He
observed it again the following night, and it had moved.
After two more nights of observation, he thought he might
have identified something new, which might perhaps be a comment,

(06:43):
so we contacted the press. Yeah, that was customary. It
wasn't like he was a glory hound. It was just
something you did. You reported that you had maybe found something.
So I'm imagining that as he was doing this, he
was he was measuring all the stars at like the
same time time every night, because they moved anyway, Yeah,
he was mapping them throughout the course of the night. Okay,

(07:08):
so that's why they would each to get four nights observation. Uh.
And as this story hit the papers and the news spread,
other astronomers, of course started taking notice. But for his part,
Piazzi was a little reluctant to put a label on
his observation. He still was not confident about exactly what
it was. In late January, he wrote a letter to

(07:29):
his best friend in Milan about the discovery, and he
voiced his uncertainty and excitement all at once. Just here's
what he said. I've announced this star as a comet,
but since it shows no nebulosity, and moreover, since it
had a slow and rather uniform motion, I surmised that
it could be something better than a comet. However, I

(07:50):
would not buy any means advanced publicly this conjecture. As
soon as I shall have a larger number of observations,
I will try to compute its elements. And in fact,
a second letter that he wrote the very same time,
but to another colleague, also in Milan, is a little different.
He indicated in that letter with more certain language, that

(08:11):
he felt that his observed object was a comet. And
this inconsistency as to whether it might be a planet
or whether it certainly was a comment was noted by
the two recipients, who knew each other. They basically gossiped
about their comment letter well, and in the writings about it,
the one that he wrote to and said it was

(08:33):
a comet seemed almost peeved that he hadn't shared the
possibility that it could be a planet like he seemed
kind of offended at how he had been left out
of the loop. So to further complicate matters, Piazzi became
ill after his first forty one days of observation and
his study of this new object had to be halted.
Then the son's halo made it impossible to see for

(08:56):
a while. Piazzi's colleagues had to use the data he
had collected up to that point to try to calculate
where the planet would appear again once it would become
observable again, and eventually it was the young German uh
Carl Friedrich Gauss, who was only twenty four at the time,
who devised a calculation method that correctly located piazz has

(09:17):
lost planet or comments. As the public interest group people
started asking astronomers about Piazzi's discovery. This actually led to
some interesting cattiness regarding what to name it. When Johann
elert Bode spoke to the Prussian Academy and in the
press at Easter just a few months after Piazzy had
made his first observation, he declared the discovery of a

(09:41):
new planet, this really being Piazzi's discovery, not his own,
which he called. Juno astronomer of Baron Franz Zavit von Zak,
who will talk about more in just a moment, called
it Harra. And Piazzi had actually named his discovery series Ferdinandea,
after the Roman goddess of agriculture, that's the series portion

(10:02):
and the patron goddess of Sicily as well, series was
Uh and King Ferdinand of Bourbon. And he was not
too pleased about the other names being spouted by other astronomers,
and in a letter to a colleague in August of
eighteen o one, he said, quote, if the Germans think
they have the right to name somebody else's discoveries, they
can call my new star the way they like. As
for me, I will always keep it the name of Surer,

(10:25):
and I will be very obliged if you and your
colleagues will do the same. Like the Bone Wars. We
already have that an archive from past hosts if you
want to hear about it. Yeah. The name Series was
eventually acknowledged throughout the astronomical community, although the Ferdinandia was

(10:46):
dropped largely because it made the name terribly long. And
as for the nature of Series, by mid eighteen o two,
after another astronomer had observed it and its orbit had
been tracked, was fairly settled to most that it was
in need a planet and not a comet. It wasn't
entirely settled. There were some people who doubted it entirely,
and when Piazzy rewrote his observations in a new edition

(11:09):
with different data, it caused quite a stir. Von Zac wrote, quote,
what is going on with Series Fernandia? Nothing has been
found as yet, either in France or Germany. People's are
starting to doubt Already skeptics are making jokes about it.
What is devil Piazzy doing? I love finding out how

(11:32):
catty this whole, this whole group of scientists was. They're
so often so catty. Uh. Piazzi's full findings with all
of the updated data were published in September of eighteen
o two, and while Series was obviously much smaller than
any planet identified up to that point, astronomers were still

(11:52):
categorizing it as a new planet, and finding a new
planet was a really important event at this juncture in history.
Uh And in the wake of the publishing there was
this flurry of activity as other astronomers analyzed the data
and calculated the orbit of Series and hashed out any
and all details, and they were ever debating the merit
of Piazzi's work, and Piazza himself was busy working on

(12:14):
other responsible abilities at the university. However, he also maddened
the astronomical community by continually and casually referring to Series
as a star or a comet sometimes rather than a planet.
There's actually a funny bit of coincidence around Piazzi discovering Series, because,
as we mentioned earlier, there were other astronomers who were

(12:35):
really focused on looking for this planet they thought must
be in the region of space him then by the
orbits of Jupiter and Mars. One of them a German
Hungarian astronomer named Baron Franz Zabra von Zach who we
mentioned earlier had determined what was that what was needed
was a collective effort, So von Zak invited most of

(12:57):
the prominent astronomers of the day to be to this project,
and this group became known as the Celestial Police. They
each patrolled for to keep with the policing metaphor, a
designated section of the heavens in search of the missing planet,
and eventually Piazzy was invited to be part of the team,
but it appears that the invitation, which was relayed through

(13:19):
a letter written to another colleague, was actually dated after
Giuseppe Piazzy had found Series already, and moreover, Piazzy never
received that invitation, So there is some speculation, given the
evidence of how Caddie all of these dudes could be,
that they were trying to kind of like loop him

(13:40):
into their crowd so that they could all share some
of the glory of having found it after the fact. No,
we totally we invited him to be part of our group.
You got guys, it sounds like middle school really does.
When a new element was found in eighteen o three,
it was named Serrium and attribute to Series. This was

(14:02):
definitely a time of series fever and The practice of
naming elements after recently discovered planets has happened several times. Uranium, neptunium,
and plutonium are all named for planets as well. Because
Series was so small in comparison to any of the
other known planets, it eventually was sort of classified as

(14:23):
a minor planet, and the search for another planet between
Mars and Jupiter that might perhaps have greater mass uh continued.
It was spurred on, in fact, by Piazzy's find So
not long after the Series discovery, and over a period
of six years, three other planets were discovered in that
same band of space. So that's right. There's a time

(14:44):
that was believed that we had four entire planets between
Mars and Jupiter, and the first of these was initially
observed on March eighteen o two, so that was even
before Piazzy had published his final data on Series, and
that was identified by Wilhelm Olbers and he saw something

(15:05):
in the wing of the Virgo constellation that he had
not observed prior, and after two days of observation of
this object, he was convinced it was a planet, and
he named it Palace. Other astronomers were also pretty quickly convinced,
and it made them even more certain that there might
be yet other planets in that Mars Jupiter gap. On
September one, st eight, you know, for Carl Ludwig Harding

(15:27):
spotted the next planet at the intersection of the orbits
of Series and Palace, and this one was called Juno.
Willelm Olbers once again had the honor of discovering the
fourth new planet of the nineteenth century, Vesta, on March
twenty eighteen O seven. Palace, Juno, Investa were all smaller
than Series, so they too were considered minor planets. But

(15:50):
of course, if you crack open any current textbook that
features our Solar system, none of these objects are listed
as planets at all. So you may be wondering what happened,
And we're going to talk about how Series and its
siblings ceased to be classified as planets, whether minor or not.
Right after we pause once again for a quick word
from one of our sponsors to get back to what

(16:18):
happened the Series. Slowly, the realization was made the Series
and its neighbors where maybe not actually planets after all.
When a fifth body named Austraia was discovered in five
by kale Hanky it was classified as an asteroid. The
term asteroid had actually been used by William Herschel as
a proposed classifier when Palace was first found. But the

(16:43):
discovery of the asteroid Australia really started a shift in
thinking about the four previous discoveries that had happened in
that belt. And soon more and more asteroids were identified
in that same area where all of these objects were
existing together. Soon more and more asteroids were identified in
that same area where all of these objects existed, and

(17:05):
eventually it dawned on people that what was actually there
was an asteroid belt. So to talk about how Series
and all these other asteroids came from, we have to
go way way way back four point six billion years.
At that point, a disc shaped dust and gas cloud

(17:26):
was around our still forming Sun. So that's the solar nebula,
slowly leading to the formation of planets within that cloud. Yes,
so as some particles would bump into each other, they
would stick to one another, and then they would collide
with more particles and form progressively larger and larger clumps,

(17:46):
eventually growing large enough that these clumps would develop gravitational
pull and then attract more mass to them, but not
all gravity bearing clumps are created equal, some grow larger
than others. Once Jupiter developed, it's highly likely that its
gravity was so great that it just dominated the material
attraction game in that part of the Solar nebula. So Jupiter,

(18:11):
with its massive size, rob Series and other objects of
the chance to grow into full sized planets. That asteroid
belt that Series is part of is sometimes just sometimes
described as that missing planet between Mars and Jupiter that
just couldn't pull itself together into one cohesive body because
of Jupiter's incredible gravitational pull. That's selfish and jerk Jupiter. No,

(18:37):
I'm don't write me hate mail because you love Jupiter.
I love it too, But it did cost the opportunity
of Series and other objects UH from forming into bigger objects.
So the diameter of Series and its equator, it's about
six hundred and five miles or nine seventy kilometers, and
its surface area is equivalent to about thirty eight percent

(19:00):
United States. So if you could unwrap the surface of
Series and lay it out on a map of the US,
that's how you would get that percentage number. As to
why this is not a planet, the requirements for a
heavenly body to be classified as a planet, as formally
determined by the International Astronomical Union in two thousand and
six are as follows a planet, There's a celestial body

(19:24):
that is in orbit around the Sun, has sufficient mass
for its self gravity to overcome rigid body forces so
that it assumes a hydrostatic equilibrium, which means nearly round shape,
and it has cleared the neighborhood around its orbit. And
these are the same requirements you may recall that Pluto

(19:44):
was not able to meet and so got demoted to
dwarf planet. Series does not clear the neighborhood around its orbit.
So while it's particularly unusual in comparison to other asteroids
in one case because it is so round compared to others,
still no die us on planethood. We should mention though,
that when the argument about Pluto's stand status as a

(20:05):
planet or not was still in play, it briefly brought
up the possibility of reclassifying Series as a planet once again.
But even though it's not a planet but a dwarf planet,
Series is still the dominant feature of the asteroid belt.
It's a lot larger than anything else in the belt.
By a significant margin. Series contains approximately thirty of the

(20:27):
total mass found in the asteroid belt. That's a lot
if you think about all of that stuff floating in
the asteroid belt, of it is all concentrated in Series.
On September two thousand seven, NASA's Dawn mission, which was
read led by the Jet Propulsion Lab at California, launched
a spacecraft from Cape Canaveral Air Force Station, Florida and

(20:51):
its destinations that's destination's plural, VESTA and Series. After spending
some time with VESTA in terms of a year in
a few months, Dawn arrived at the series in early March.
That made it the first spacecraft to orbit two extraterrestrial
targets as well as the first to orbit an asteroid. Yeah.

(21:11):
That's sort of one of the cool things in all
of this and one of the things that I love
particularly about spaces that we're watching history be made all
the time, which is really cool. Uh. And you may
be wondering why it would be so important to study Series.
As we mentioned earlier, it was likely on its way
to becoming a planet before Jupiter mucked that whole thing up,

(21:31):
so it's considered a proto planet. And by studying proto
planets we have the potential to discover all kinds of
things about planetary development and as a consequence, our own
planet Earth. It's like traveling back in time and looking
at history sort of in an arrested state. This is
like the space version of the Island of Curtsey that
we talked about in our Hamming episode. That like it's

(21:54):
been protected since it was farmed, so scientists can study
like how islands get plants and animals living on them.
It's like that boot space and without plants and animals
living on it that we know of. As we mentioned earlier,
Series is the Roman goddess of harvests, so the naming

(22:17):
convention for the features of series discovered by the Dawn
Mission follows that theme, with gods and goddesses, vegetation, and
festivals related to agriculture serving uh as the well of
the options for naming things on it and thanks to
the Dawn Project, we now know a lot more about
series than we did just a few years ago. It's

(22:37):
covered with shallow craters, which we didn't know. It appears
to have water ice on its surface. There are numerous
bright spots on the dwarf planet surface, likely a substance
such as ice or salt that's reflecting light. Dawn has
now photographed of the surface with the resolution of a
hundred and twenty feet or thirty five ms per pixel. Yeah,

(22:58):
and I didn't put the exact where that far exceed
exceeds the projected goal for Series. I think the goal
was to photograph approximately eight percent of the planet's surface.
So the Dawn mission has really exceeded all expectations. It's
been quite amazing, uh, and kind of in line with that.
The Dawn spacecraft was originally intended to remain a satellite

(23:21):
of Series indefinitely once the mission had ended. In the
time since it arrived at Series, it's performed more than
one thousand orbits and it is extremely stable there. But
quite recently, in April of this year, so seen, a
new proposal was submitted to extend Dawn's mission. A team
from University of California at Los Angeles, headed by Chris Russell,

(23:42):
would like for Series to visit yet another object rather
than just be parked in orbit. As of this recording,
I could not find any news on a decision one
way or another, but there could be a whole another
phase of life for this really cool mission, which is
exploring this really cool dwarf planet that we once thought
was a planet and now is not. And thankfully enough

(24:02):
time has passed that the sour grapes that may have
existed over that demotion are completely died down. And I
can't wait for that to be the case with Pluto
as well. Do you also have some listener mail? I
am now that I've done pushing my Pluto as a
dwarf planet, and that's fine agenda. Um. So I have

(24:26):
two wonderful postcards from our listener, Jennifer and her dad.
They are traveling through France, and the first one is Hi, ladies,
my dad and I are at Arles, France today, home
of many of Angos sites that inspired many of his works.
We had drinks at the Night Cafe and we are
staying in Saint Remy, which is what Starry Night depicts. Again,

(24:47):
I have to thank you for wonderful hours of entertaining podcast.
We will write again and delivered on that one, says
Hi again ladies, writing from Rousillon, this time where there
are beautiful hills of red and orange. The village also
minds Ochre mineral deposits used to color paints and makeups,
which we talked about in our History of Cosmetics episode. Uh,

(25:07):
my fan in the color episode, I believe my father
and I have been enjoying your podcast as we drive
through the countryside. You all make the journey just a
bit more interesting. Uh. And she says, well, write again.
I have not gotten another one, but these are both
so lovely. It's so nice to sort of get to
go on the trip with them and see where they've
been going. And I really I know I say it
all the time, but I feel it always merits saying

(25:28):
it again. I am always so grateful and touched and
honored that people want to take time out of their
vacation to write us a postcard and send it. Uh.
It's incredibly meaningful. It's so kind and thoughtful. So thank you,
thank you, thank you. If you would like to write
to us, you can do so at History Podcast at
how Stuff Works dot com. You can visit us at

(25:49):
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go to our parents site, how stuff Works. Type of
the word asteroid in the search bar, and you will

(26:11):
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(26:38):
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