Source: Mike Brown, CalTech, July 2007
Some links are to other parts of this document.
Most are to other pages on Mike Brown's site or elsewhere on the Internet.
The discovery of
2003 UB313 Eris,
the 10th planet
the largest known dwarf planet
Discovery images of the dwarf planet Eris.
The three images were taken 1 1/2 hours apart on the night of October 21st, 2003.
Eris can be seen very slowly moving across the sky over the course of 3 hours.
Eris is 27% more massive than Pluto
2003 UB313 is now officially Eris!
Eris, the largest dwarf planet known, was discovered in an ongoing survey at
Observatory's Samuel Oschin
telescope by astronomers Mike Brown (Caltech), Chad Trujillo (Gemini
Observatory), and David Rabinowitz (Yale University). We
officially suggested the name on 6 September 2006, and it was accepted
and announced on 13 September 2006. In Greek mythology, Eris is the
goddess of warfare and strife. She stirs up jealousy and envy to cause fighting and
anger among men. At the wedding of Peleus and Thetis, the parents of the Greek
hero Achilles, all the gods with the exception of Eris were invited, and,
enraged at her exclusion, she spitefully caused a quarrel among the goddesses
that led to the Trojan war. In the astronomical world, Eris
stirred up a great deal of trouble among the international astronomical community when the
question of its proper designation led to a raucous meeting of the IAU in Prague. At the end of the conference,
IAU members voted to demote Pluto and Eris to dwarf-planet status, leaving the
solar system with only eight planets.
The satellite of Eris has received the offical name Dysnomia, who in
Greek mythology is Eris' daughter and the demon spirit of lawlessness.
As Dysnomia is a bit of a mouthful, we tend to simply call the satellite Dy, for short.
As promised for the past year, the name Xena (and satellite Gabrielle)
were simply placeholders while awaiting the IAU's decision on how an
official name was to be proposed. As that process dragged on, however,
many people got to know Xena and Gabrielle as the real names of these
objects and are sad to see them change. We admit to
some sadness ourselves.
We used the names for almost two years now and are having a hard time
swtiching. But for those who miss Xena, look for the obvious nod in the
new name of the moon of Eris.
Artists concept of the view from Eris with Dysnomia
in the background, looking back towards the distant sun.
Credit: Robert Hurt (IPAC)
What is it?
This new dwarf planet (see the now out of date "What makes a planet?"
below) is the largest object found in orbit around the sun
since the discovery of Neptune and its moon Triton in 1846. It is
larger than Pluto, discovered in 1930. Like Pluto, the new dwarf planet
is a member of the Kuiper belt, a swarm of icy bodies beyond Neptune in
orbit around the sun. Until this discovery Pluto was frequently
described as "the largest Kuiper belt object" in addition to being a
dwarf planet. Pluto is now the second largest Kuiper belt object,
while this is the largest currently known.
Where is it?
The dwarf planet is the most distant object ever seen in orbit around
the sun, even more distant than Sedna, the
planetoid discovered almost 2 years ago. It is almost 10 billion miles
from the sun and more than 3 times more distant than the next closest
planet, Pluto and takes more than twice as long to orbit the sun as
A view of the solar system from the north down. The four
circles show the orbits of Jupiter, Saturn, Uranus, and Neptune. The
yellow dot in the center is the sun. The earth, if it were shown, would
be inside the yellow dot representing the sun. The orbits of the two outermost planets, along
with their current positions, are also shown. If you are worried
because the sun appears to not be the focus of the orbital ellipse you are very observant!
But it is just a projection effect. The see the full 3D orbit go to
very nice web page
The dwarf planet can be seen using very high-end amateur equipment, but you need to know where
to look. The best way to find precise coordinates (of this planet, or
any other body in the solar system) is with JPL's horizons system. Click
on "select target" and then enter "2003 UB313" under small bodies.
The orbit of the new dwarf planet is even more
eccentric than that of Pluto. Pluto moves from 30 to 50 times the
sun-earth distance over its 250 year orbit, while the new planet moves
from 38 to 97 times the sun-earth distance over its 560 year orbit.
How big is it?
Usually when we first discover distant objects in the outer solar
system we don't know for sure how large they are. Why not? Because all
we see is a dot of light, like the picture at the top of the page. This
dot of light is sunlight reflected off the surface of the planet (interestingly the
sunlight takes almost a day to get out to the planet, reflect off of
it, and get back to the earth!), but we don't know if the object is
bright because it is large or if it is bright because it is highly
reflective or both.
When an object is too far away to directly see how big it is,
astronomers use an indirect method instead where they measure the heat
coming from the object. If we wanted to measure the size of a fire, for
example, we could do it by measuring the total amount of heat coming
from the fire. The temperature of the flames in a match and a bonfire
are essentially the same, but a bonfire emits much more heat because it
is much bigger. The same is true of distant planets. Because we know
how far away the planet is we have a pretty good idea of the surface
temperature (a frosty 405 degrees below zero!), thus when we measure
the total heat we can tell how big the object is. Unfortunately, the
new planet is so far away and so cold that our first attempt at
measuring the heat, using the Spitzer Space Telescope, could not detect
the heat output. This fact tells us that the object must be smaller
than about 3300 km.
In the meantime, observations have been made by a group from the
University of Bonn from the 30-meter IRAM telescope. This telescope, like Spitzer, measures the heat output. IRAM
measures the heat output in a region of the spectrum where much
less heat is given off, but IRAM is a much larger telescope than
Spitzer. The observations were successful in finally detecting the heat
of Eris. From the amount of heat measured they determined that Eris has
a diameter of 3000 +/- 400 km. A very nice discussion of the measurement and what the
uncertainties mean can be found at the
press release web page.
The newest size measurement comes
from the Hubble Space Telescope.
While for most telescopes the planet is too small to be seen as
anything other than a dot of light, HST can (just barely) directly
measure how big across it is. The measurement is extremely hard,
however, even for HST, because even HST distorts light a little bit as
it goes through the telescope, and we needed to be sure that we were
measuring the actual size of the planet, rather than being fooled by
distortion. So we waited until Eris was very close to a star and
then snapped a series of 28 pictures and carefully went back and forth
comparing the star and the planet. In the end, we determined that Eris is 2400 +/- 100 km across.
The best ever picture from the Hubble Space Telescope, as unimpressive
as it is (since Eris is so so so so so far away) looks like
When we initially guessed how big Eris was, we thought it was
likely a bit larger, because we guessed that it probably reflected the
same amount of sunlight as Pluto (about 60%). But this new size
measurement tells us that the planet reflects considerably more
sunlight than Pluto (86 +/- 7%)!. For more on this see below on what
Eris is made out of.
The new HST measurement makes it sound like the previous measurement
was "wrong," but it was not! All measurements in science are subject to
uncertainty, and the group from Bonn carefully stated what their
uncertainty was, just as we have with the new measurement.
What is on the surface of Eris?
We study the composition of distant objects by looking at sunlight
reflected off of them. The sunlight reflected off the surface of the
earth, for example, shows distinct signatures of the oxygen in earth's
atmosphere, of photosynthetic plants, and of abundant water, among
other things. We have been using the Gemini
Observatory on Mauna Kea, Hawaii to study the light reflected from
the surface of Eris, and have found that the dwarf planet looks
remarkably similar to Pluto. A comparison of the two is shown below,
where we show the amount of sunlight reflected in near infrared light.
This type of light, just beyond what is visible to the
human eye, is most sensitive to the types of ices expected on
surfaces in the outer solar system.
The plot above compares the amount of infrared sunlight of different colors ("wavelength") reflected from the
new planet with the amount of sunlight reflected from Pluto. The dips
in the amount of sunlight at 1.15, 1.35, 1.7, and 2.3 um are a characteristic signature of a surface
covered with solid frozen methane (natural gas). Both Pluto and Eris show
these signatures. At the very low temperatures of Pluto and Eris,
methane, which is in gaseous form on the earth, is frozen solid.
The interior of Eris, like the interior of Pluto, is likely a mixture of rock and ice.
Pluto and the new dwarf planet are not completely identical, however. While
Pluto's surface is moderately red, the new dwarf planet appears almost white,
and while Pluto has a mottled-looking surface which reflects on average
60% of the sunlight which hits it, the new planet appears essentially
uniform and reflects 86% (+/- 7%) of the light that hits it. These
characteristics were not at all expected. In fact, Eris reflects
more sunlight from its surface than any body in the solar system other
than Saturn's moon Enceladus,
which has active geysers continuously coating the surface in
fresh frost. We can't think of any source of heat for Eris that
would cause similar geysers. So what is happening?
We think that the bright surface and uniform white coloring of the
planet both have the same cause. Right now the planet is as far away
from the sun as it ever gets, and thus as cold as it ever gets. At this
distance from the sun even the planet's atmosphere is frozen solid. (In
fact if the earth were brought that far away from the sun its
atmosphere would freeze solid, too!). In 280 years the planet will be
the closest it ever gets -- a factor of almost 2.6 times closer. The
absolute temperature on the planet will rise over the next 280 years by
a factor of 1.6 (which is the square root of 2.6). The current
temperature of (a quite cold) 405 degrees below zero will be but a
distant memory at this point when the temperatures will be a balmy 360
degrees below zero. While both of these temperatures seem frigid beyond
imagination, to methane and nitrogen (the likely components of the
atmosphere of the planet), the difference between the two is the
difference between frozen solid and evaporating into the atmosphere.
In this hypothesis, then, Eris is bright and uniform because the
atmosphere that it used to have (280 years ago at its peak) is now
frozen solid to the ground, giving a bright shining coating to whatever
type of mottled surface used to be there. The whole atmosphere is now
probably only a few inches thick.
This whole process repeats itself over and over and over with the
dwarf planet's orbital period of 580 years.
For comparison, the relative temperature change on the new planet is
equivalent to the earth's average temperature changing from about 60
degrees F to about 360 degrees F ever 6 months. No other planet in the
solar system -- dwarf or otherwise -- goes through temperature swings
nearly as extreme as this!
What is Eris made out of?
While we can only see the surface of the dwarf planet, we have some educated
guesses about the interior. Pluto, we know, has a density about midway
between ice and rock, thus we think that it is made of about half and
half ice and rock on the inside. The new planet, being about the same
size and the same surface composition as Pluto, is probably close to
the same. We used to suspect that all
objects out in the Kuiper belt are the same on the inside but
recent measurements suggest a very wide variety! For this reason, we
are quite anxious to measure the actual density of the planet itself.
Such a measurement is possible by measuring the mass of the planet by
looking at the way its moon goes around
it and then dividing this mass by the volume (which we know because we
know the size). We need more observations of the moon to accurately
determine its orbit, however, so we don't think we will know the answer
until the end of the year.
How was Eris found?
We have been conducting an ongoing survey of the outer solar system using the
Palomar QUEST camera and the
Samuel Oschin Telescope at
in Southern California. This survey has been operating since the fall of
2001, with the switch to the QUEST camera happening in the summer of
2003. To date we have found around 80 bright Kuiper belt objects.
To find objects, we take three pictures of a small region of the night
sky over three hours and look for something that moves. The many billions of stars and
galaxies visible in the sky appear stationary, while satellites,
planets, asteroids, and comets appear to move. The image below shows
the three frames taken the night of October 21st, 2003 where we found
the new planet. Can you find the moving object?
The area of sky shown here is approximately 0.015% of the amount of sky that we look at every night,
but even though we survey vast regions of the sky per night, it is
still going to take us about 5 years to look at all of the sky visible
from Palomar Observatory.
Happily for us (and our families) much of the work is done by
computers. The telescope is robotically controlled and sends its data
to Pasadena every morning where it is searched by a bank of 10
computers at Caltech. Each morning the computers find approximately 100
potentially-moving objects that a human has to look at. The vast
majority are some flaw in the camera and are not real solar system
objects, but, occasionally, as seen above, a real object makes its
Because the new dwarf planet is so far away it is moving slower than
most of the objects that we find. It is moving so slowly, in fact, that our
computers didn't notice it the first time around! We began a special
reanalysis a year later to specifically look for very distant objects.
This reanalysis found the new planet at 11:20AM PST on January 5th
2005, almost 1 1/2 years after the initial data were obtained. Note that initial reports
suggested that the discovery date was January 8th. We apologize for the
mistake; it was caused because of the craziness surrounding the first
day of announcement. We didn't have time to check our notes and
apparently our memories are not as good as they used to be.
What is the real name going to be?
This part is obviously out of date - the answer to the question is Eris
When a new object is discovered the International Astronomical Union
(IAU) gives it a temporary designation based on the date it was first
seen. Thus 2003 UB313 can be decoded to tell you that the data from
which the object was discovered was obtained in the second half of
October 2003. Next, depending on what the object is, the discoverers
propose a certain type of permanent name.
Interestingly, there are no actual rules for how to name a
planet (presumably because no one expected there to be more). All of
the other planets are named for Greek or Roman gods, so an
obvious suggestion is to attempt to find such a name for the new
planet. Unfortunately, most of the Greek or Roman god names
(particularly those associated with creation, which tend to be the
major gods) were used back when the first asteroids were being
discovered. If a name is already taken by an asteroid, the IAU would
not allow that name to be used again. One such particularly apt name would have been
In Greek mythology Persephone is the (forcibly abducted) wife of Hades
(Roman Pluto) who spends six months each year underground close to
Hades. The new planet is on an orbit that could be described in
similar terms; half of the time it is in the vicinity of Pluto and half
of the time much further away. Sadly, the name Persephone was used in
1895 as a name for the 399th known asteroid. The perhaps more
appropriate Roman version of the name, Proserpina, was used even earlier
for the 26th known asteroid. The same story can be told for almost any
other Greek or Roman god of any consequence. One exception to this name
depletion is the Roman god Vulcan (Greek Haphaestus), the god of fire.
Astronomers have long reserved that term, however, for a once
hypothetical (now known to be nonexistent) planet closer to the
sun than Mercury (god of fire, near the sun, good name). We would
not want to use such a name to describe such a cold body as our new
Is this object really a planet or a dwarf planet?
Is Pluto a planet? What makes a planet?
note that all of this is out of date as of August 2006!
Even after all of these years of debate on the subject of whether or
not Pluto should be considered a planet, astronomers appear no closer
to agreement. I wrote extensively about this at the time of the
discovery of Sedna in March 2004. My thoughts have evolved since then,
so it might be amusing to see what
I said 1 1/2 years ago. I have been heavily influenced by writing a
scientific review article this summer on the topic of "What is a
planet?" with my colleague Gibor Basri at U.C. Berkeley who I thank for
his insights. The main stumbling block in defining planets in our solar
system is that, scientifically, it is quite clear that Pluto should
certainly not be put in the same category as the other planets. Some
astronomers have rather desperately attempted to concoct solutions
which keep Pluto a planet, but none of these are at all satisfactory,
as they also require calling dozens of other objects planets. While
people are perhaps prepared to go from 9 to 10 planets when something
previously unknown is discovered, it seems unlikely that many people
would be happy if astronomers suddenly said "we just decided, in fact,
that there are 23 planets, and we decided to let you know right
now." There is no good scientific way to keep Pluto a planet
without doing serious disservice to the remainder of the solar system.
Culturally, however, the idea that Pluto is a planet is enshrined in
a million different ways, from plastic placemats depicting the solar
system that include the nine planets, to official NASA web sites,
to mnemonics that all school children learn to keep the nine planets
straight, to U.S. postage stamps. Our culture has fully embraced the
idea that Pluto is a planet and also fully embraced the idea that
things like large asteroids and large Kuiper belt objects are not
In my view scientists should not be trying to legislate an entirely
new definition of the word "planet." They should be trying to determine
what it means. To the vast majority of society, "planet" means
those large objects we call Mercury through Pluto. We are then left
with two cultural choices. (1) Draw the line at
Pluto and say there are no more planets; or (2) Draw the line at Pluto
and say only things bigger are planets. Both would be culturally
acceptable, but to me only the second makes sense for what I think we
mean when we say the word planet. In addition, the
second continues to allow the possibility that exploration will find a
few more planets, which is a much more exciting prospect than that
suggested by the first possibility. We don't think the number of
planets found by the current generation of researchers will be large.
Maybe one or two more. But we think that letting future generations
still have a shot at planet-finding is nice.
Astronomers tend to dislike this solution as it is clearly
non-scientific. The best analogy I can come up with, though, is with
the definition of the word "continent." The word sound like it should
have some scientific definition, but clearly there is no way to
construct a definition that somehow gets the 7 things we call
continents to be singled out. Why is Europe called a separate
continent? Only because of culture. You will never hear geologists
engaged in a debate about the meaning of the word "continent" though.
When geologists talk about the earth and its land masses they define
precisely what they are talking about; they say "continental crust" or
"continental drift" or "continental plates" but almost never
"continent." Astronomers need to learn something from the geologists
here and realize that there are a few things -- like continents and
planets -- to which people have large emotional attachments, and they
should not try to quash that attachment.
Thus, we declare that the new object, with a size larger than Pluto,
is indeed a planet. A cultural planet, a historical planet. I will not
argue that it is a scientific planet, because there is no good
scientific definition which fits our solar system and our culture, and
I have decided to let culture win this one. We scientists will continue
our debates, but I hope we are generally ignored.
How was the planetary status be decided?
The above gives my personal view on how to resolve the planetary
status. The official decision will come from the International
Astronomical Union. We had hoped for a timely decision but we instead
appear to be stuck in committee limbo. Here is the story, as best I can
reconstruct it from the hints and rumors that I hear:
What else is out there?
The last week of July 2005 was an exciting one for the outer solar
system. In the course of two days the existence of three new objects
was announced, and each object was brighter than all of the previously
known objects in the Kuiper belt (with the exception of Pluto). With so
many bright objects coming out at once it is hard to keep them all
straight. Here is the quick score card:
|Brown, Trujillo, Rabinowitz
|Brown, Trujillo, Rabinowitz
|Brown, Trujillo, Rabinowitz
|2400 +/- 100 km (105% Pluto)
|4th brightest Kuiper belt object
|3rd brightest KBO
|2nd brightest KBO
|(note that though we
consider Pluto and Eris planets, they are also clearly members of
the Kuiper belt, with Pluto the brightest member)
|(an AU is the
distance from the earth to the sun)
|closest approach to sun
|furthest from sun
|tilt of orbit compared to planets
|yes! (two of them!)
|late summer, fall, early
spring, early summer
Here is where these extremely bright Kuiper belt objects are in the
solar system these days:
What is the real story about the hasty announcement and the reports of "hacking"?
In mid-July 2005 short abstracts of scientific talks to be given at a
meeting in September became available on the web (for example,
We intended to talk about the object now known as 2003 EL61, which we
had discovered around Christmas of 2004, and the abstracts were
designed to whet the appetite of the scientists who were attending the meeting. In these
abstracts we call the object a name that our software
automatically assigned, K40506A (the first Kuiper belt object we
discovered in data from 2004/05/06, May 6th). Using this name turns out
to have been a very bad idea on our part! Unbeknownst to us, some of the
telescopes that we had been using to study this object kept open records
of who has been observing, where they have been observing, and what
they have been observing (these detailed records have since been
removed from the web). A two-second Google search of "K40506A"
immediately reveals one of these observing records. A little playing
around with web addresses then reveals even more records not initially Googleable. Ouch. Bad news for us. From
the moment the abstracts became public anyone on the planet with a web
connection, and a little curiosity about this "K40506A" object, and a knowledge of orbital dynamics could
have found out where it was. Anyone on the planet with even a
modest-sized telescope could then go find the object and claim a discovery as their own.
According to our web server logs, these observing logs were accessed
on July 26, 2005 by a computer at the Instituto de Astrofisica in
Spain. Less than two days after this computer accessed the observing
logs, the same computer was used to send email officially claiming the
discovery by P. Santos-Sanz and J.-L. Ortiz at the Instituto de
Astrofisica (see detailed timeline here). At the time of the announcement
we truly believed that they had no prior knowledge that we had been
observing the object, and we truly believed that they had not used our
data to make the announcement of the discovery, but other people found
the coincidence suspicious.. Shortly after their announcement, however, we realized that all of our observing
records -- including those about what is now known as 2003 UB313, the
tenth planet -- were unexpectedly public, and made the decision to prematurely announce the discovery of 2003 UB313 that
same afternoon by a press conference. We were unhappy about having to
forgo normal scientific protocol and announce the discovery with no
corresponding scientific paper, but under the circumstances we felt we had no choice.
It is worth asking: if the observing records were on a publicly
accessible web site, is it wrong to look at them? The obvious
answer is that there is nothing wrong with looking at information on
any publicly accessible web site, just as there is nothing wrong with
looking at books in a library. But the standards of scientific ethics
are also clear: any information used from another source must be
acknowledged and cited. One is not allowed to go to a library, find out
about a discovery in a book, and then claim that discovery as your own
with no mention of having read it in a book. One is not even allowed to
first make a discovery and then go to the library and realize that
someone else independently made the same discovery and then not
acknowledge what you learned in the library. Such actions would be
considered scientifically dishonesty. It is not clear from the timeline
precisely what Ortiz and Santos-Sanz knew or how they used the
web-based records. They were required by the standards of science, however, to acknowledge their use
of our web-based records if they accessed them. The director of the IAA,
Dr. Jose Carlos del Toro Iniesta has promised to investigate what
precisely happened. We have confidence in Dr. del Toro Iniesta to
clarify the situation and determine the appropriate actions.
Some have commented that the real fault here was our own for keeping
the objects "secret." We are saddened by anti-scientific statements
like these, and have already
written extensively on why this rather bizarre accusation is spurious
below. The community of scientists condemns scientists who announce their results publicly before publishing
scientific papers. Regardless of the number of times these bizarre
accusations are repeated, we will continue at all times to adhere to
accepted scientific protocol.
Why does it take so long to announce these discoveries?
Soon after the announcement of the discovery of the new planet the
suggestion slowly made its way around the internet that we, the
discoverers, were somehow violating long standing scientific standards
by keeping the existence of the planet "secret" for so long. This
suggestion seemed so bizarre to us that we paid no attention at first,
but, as with many things on the internet, it has been repeated enough
times even reasonable people are starting to believe it. We would like
to quickly dispell this odd misconception that no credible scientist
One of the things that is so strange about this allegation is that it
should also be made of every single scientific result that is published
in a reputable scientific journal. In all such cases, scientists make
discoveries, they verify their discoveries, they carefully document
their discoveries, and they submit papers to scientific journals. What
they don't do is make
discoveries and immediately hold press conferences to announce them
(one need only think back to the cold fusion days to remember how
thoroughly the scientific community condemns such behavior). Good
science is a careful and deliberate process. The time from discovery to
announcement in a scientific paper can be a couple of years. For all of
our past discoveries, we have described the objects in scientific
papers before publicly announcing the objects' existence, and we have
made that announcement in under nine months. These papers allow other
astronomers to verify, confirm, and critique the analysis we have done.
Sadly, because we were forced to announce 2003 UB313 prematurely, we
have still yet to complete the scientific paper describing this object
(it is now finally complete! see below).
We find this situation scientifically embarrassing and apologize to our
colleagues who are reduced to learning about this new object from
reading reports in the press. We are hard at work on this scientific
paper, but, as we said above, good science is a careful and deliberate
process and we are not yet through with our analysis. Our intent in all
cases is to go from discovery to announcement in under nine months. We
think that is a pretty fast pace.
One could object to the above by noting that the
existence of these objects is never in doubt, so why not just announce the existence
immediately upon discovery and continue observing to learn more? This way other
astronomers could also study the new object. There are two reasons we
don't do this. First, we have dedicated a substantial part of our
careers to this survey preciselyso that we can discover and have the first crack at studying the large
objects in the outer solar system. The discovery itself contains little
of scientific interest. Almost all of the science that we are
interested in doing comes from studying the object in detail after discovery. Announcing the
existence of the objects and letting other astronomers get the first
detailed observations of these objects would ruin the entire scientific
point of spending so much effort on our survey. Some have argued that
doing things this way "harms science" by not letting others make
observations of the objects that we find. It is difficult to understand
how a nine month delay in studying an object that no one would even
know existed otherwise is in any way harmful to science!
Many other types of astronomical surveys are done for precisely the
same reasons. Astronomers survey the skies looking for ever higher
redshift galaxies. When they find them they study them and write a
scientific paper. When the paper comes out other astronomers learn of
the distant galaxy and they too study it. Other astronomers cull large
databases such as the 2MASS infrared survey to find rare objects like
brown dwarves. When they find them they study them and write a
scientific paper. When the paper comes out other astronomers learn of
the brown dwarves and they study them in perhaps different ways. Still
other astronomers look around nearby stars for the elusive signs of
directly detectable extrasolar planets. When they find one they study
it and write a scientific paper..... You get the point. This is the way
that the entire field of astronomy -- and probably all of science --
works. It's a very effective system; people who put in the tremendous
effort to find these rare objects are rewarded with getting to be the
first to study them scientifically. Astronomers who are unwilling or
unable to put in the effort to search for the objects still get to
study them after a small delay.
There is a second reason that we don't announce objects immediately,
and that is because we feel a responsibility not just to our scientific
colleagues but to the public. We know that these large objects that
keep being found are likely to be the result of intensive interest by
the public, and we would like to have the story as complete as possible
before making an announcement. Consider, for example, the instantaneous
Ortiz et al. announcement of the existence of 2003 EL61. Headlines in
places like the BBC web site breathlessly exclaimed "new object may be
twice the size of Pluto." But even at the time we knew that 2003 EL61
had a satellite and was only 30% the mass of Pluto. We quickly got the
truth out, but just barely. Sadly, other interesting aspects of 2003
EL61 also got lost in the shuffle. No one got to hear that it rotates
every 4 hours, faster than anything else known in the Kuiper belt. Or
how that fast rotation causes it to be shaped like a cigar. Or how we
use the existence of the satellite to calculate the mass. All of these
are interesting things that would have let the public learn a bit more
about the mysteries of physics and of the solar system. In the press
you get one chance to tell the story. In the case of the
instantaneous announcement of 2003 EL61 the story was simply "there is
a big object out there." We are saddened by the lost opportunity to
tell a richer scientific story and to have the public listen for just
one day to a tale that included a bit of astronomy, a bit of physics,
and a bit of detective story.
Given that we do precisely what other astronomers do and that we are
actually very prompt about making announcements, where did the crazy
ideas that we should be announcing objects instantly come from?
Interestingly, there is one area of astronomy in which instantaneous
announcement is both expected and beneficial to all. In the study of
rare, quickly changing objects, such as supernovae, gamma ray bursts,
comets, and near earth asteroids, astronomers quickly disseminate their
results so that as many people as possible can study the phenomenon
before it disappears or changes completely. No one discovers a comet
and keeps it to himself to study, because by the time the study was
done the comet would be gone and no one else could study it ever again.
The people initially suggesting that we were wrong to not announce our
objects instantly are, for the most part, a small group of amateur
astronomers who are familiar with comet and near earth asteroid
observation protocols. We can only assume that this familiarity led
them to their misconceptions. Kuiper belt objects are not quickly
changing phenomena. Astronomers will be intensively studying Eris
for a long time to come.
We hope to discover a few more large objects in the outer solar system.
When we do, we will do everything we can to learn as much as possible
about them before we make their existence public, and we will try to
make the announcement as complete and scientifically and publicly
interesting as possible. We will take the chance -- as all scientists
do -- that by taking the time to do the scientific job correctly
someone else may beat us to the announcement, and if they do we will
congratulate them heartily.
The scientific paper describing the discovery is finally done!
As described in detail elsewhere, we were forced to announce the
existence of Eris before we had finished a scientific paper
describing the discovery. While announcing discoveries via press
releases with no scientific paper is generally frowned upon by
scientists (including us) our colleagues have been understanding of the
unusual circumstances under which this happened. The scientific paper
describing the discovery has just been submitted to the Astrophysical
Journal. If you are curious what one of these papers looks like you can
the entire text. Now that the paper has been submitted to the
journal, the journal will send it out for peer-review, where another
scientist will carefully and critically read what we have read and
help decide if the paper meets accepted scientific standards. In almost
all cases, the reviewer will suggest at least some changes to the
manuscript before the paper is finally accepted. This process helps
ensure that published scientific papers are as accurate and complete as
As of now the review process is complete and the revised paper is
published in the December 10th 2005 issue of the Astrophysical Journal