TABLE OF ASTEROID GROUPS
----------------------=
John Pazmino
NYSkies Astronomy Inc
www.nyskies.org
nyskies@nyskies.org
2008 August 31
Introduction
----------
The NYSkies Seminar of 3 June 2008 highlighted asteroids. The
theme was limited to asteroids inside of Jupiter's orbit, omitting
those in the outer solar system. This was merely a simplicity to help
organize the discussion.
As part of that session I hacked a table from Internet of asteroid
groups. The original was incomplete. I filled in missing data from
various websites and print references. There are still holes in the
table, but it's fleshed out to be useful in understanding and
discussing asteroids of the inner solar system.
For the Earth-threat asteroids I give the perihelion 'q' or
aphelion 'Q' as well. The dashes are data that are not applicable in
the group definition or have yet to be narrowed in my inquiries.
Readers are invited to fill in the missing data.
Groups and families
-----------------
When the number of known asteroid grew large enough, it became
evident that they bunched around certain combinations of orbital
elements. An 'asteroid group' is a set of asteroids sharing common
elements. Groups were revealed several decades ago, when asteroids
were still mere pinpoints on photographs with almost no physical
characteristics. They were studied for their dynamical behavior under
gravity of the planets, notably Jupiter.
In the late 1990s we started to examine asteroids via radar,
spectrometry, and colorimetry. These methods gave us physical
properties of asteroids, leading to the establishment of families. An
'asteroid family' is a set of asteroid sharing common physical
properties, as sussed out by their spectrum, color, and radargram.
Some groups later were found also to be families, so they show up
in dialog about both categories. There could be situations where
pieces from one larger asteroid broke off, forming a family of the
fragments. These may continue to travel in similar orbits, forming a
group.
In this article I discuss only groups, the dynamical category of
asteroid.
Elements
------
The orbital elements of an asteroid are unlike those of the major
planets. Asteroids, being infinitesimally small compared with a
planet, are disturbed easily by gravity. This disturbance shows up in
mutable orbit elements, such that a given set turns more and more
stale within a decade. Hence, in a planetarium program, you must
obtain current elements to faithfully plot the path of an asteroid.
Using old elements will plot wrong paths, however neat and pretty they
look.
Asteroid elements are
Epoch - a given date, usually in Julian Day number at even 400th days,
for which the elements are valid. The elements are valid for the next
few hundred days, until the next epoch. Elements from a several epochs
ago should be tagged for only historical use.
Mean anomaly - the angular revolution of the asteroid in its orbit
completed at the epoch date. This is NOT the 'longitude' of the
asteroid relative to the Sun! It's a uniform-flowing angular motion
from which, by computation, the actual longitude is derived. It starts
at 0 at the perihelion of the orbit and runs thru 360 degrees back at
perihelion after one lap around the orbit.
Semimajor axis - the mean between the perihelion and aphelion distance
of the asteroid from the Sun. Because asteroid orbits can be strongly
excentric, it is not wise to equate semimajor axis with a 'mean orbit
radius' like for a major planet.
Excentricity - the degree of ellipse in the shape of the orbit, like
for a periodic comet. 0 is a circular orbit. 1 is a parabola, for
which no asteroid so far qualifies. Perhaps a dead comet in a
parabolic orbit could be called an asteroid? Asteroids have closed
orbits, unlike most comets. Comets can have parabolic orbits, allowing
only a single round of the Sun. Excentricities between 0 and 1 are
ellipses, the shape for an asteroid orbit.
Inclination - the tilt of the orbit plane relative to the Earth's
orbit, or ecliptic. Once in a while this is stated relative to
Jupiter's orbit or to a combined plane of all the planets. For
statistical purposes, it doesn't matter much which inclination is
used, as long as you know which it is and don't mix them among
asteroids. Inclinations from 0 to 90 degrees are direct or prograde
orbits. 90 to 180 are for retrograde asteroids, of which there are
apparently very few.
Longitude of ascending node - the heliocentric longitude of the south-
to-north intercept of the asteroid orbit with the Earth's orbit. The
other intercept is the descending node, 180 degrees away.
Argument of perihelion - The angular distance around the orbit from
the ascending node to the perihelion point. This is measured along the
orbit, not in the ecliptic plane. For low inclination orbits, the
error is small. For inclinations greater than about 5 to 8 degrees,
the error is too severe to ignore and you must use the proper
measurement method.
longitude of perihelion - not a usual parameter, this is the sum of
the longitude of ascending node and argument of perihelion This
element is used in some statistical studies but is not a basic
dynamical property of the asteroid. The sum is a pure arithmetic one
along two paths, the ecliptic and then the orbit.
Mean daily motion - Not really necessary, but handy in computations,
it's the angular change of mean anomaly per Earth day. It can be
calculated from the semimajor axis with Kepler's laws, so it's not
really an independent element. Alternatively, it's 360 degrees divided
by the orbit period in Earth days.
Perihelion date - The date, in either decimal or in Julian Day number,
when the asteroid passes thru the perihelion point in its orbit. This
is often missed out for an asteroid because it repeatedly rounds
perihelion every few years. A comet may round perihelion once, for a
parabola orbit, or only at long intervals. At the moment of perihelion
pass the mean anomaly is 0.
Perihelion distance - Not an independent element because it can be
calculated from the semimajor axis and excentricity. It is the
distance from the Sun to the perihelion point on the orbit.
Aphelion distance - Not an independent element because it can be
calculated from the semimajor axis and excentricity. It is the
distance from the Sun to the aphelion point on the orbit.
The big three
-----------
Dynamical studies of asteroids involve all of the orbital
elements. however, for many purposes, examining just three can yield
extremely good insight to the behavior of an asteroid. These are the
semimajor axis, inclination, and excentricity. Their symbols are 'a',
'i', and 'e' in charts, tables, formulae. Sometimes the Greek letters
alpha, iota, and epsilon are used for one or an other of them.
Asteroid groups are defined principally by these three elements,
with the action of any others offering supplemental qualification.
Interrelations
------------
Several parameters are interrelated, being computed from each
other. Additional, somewhat trivial, interrelations are permutations
of the ones here.
Semimajor axis = ((perihelion) + (aphelion)) / (2)
= (perihelion) / ((1) - (excentricity))
Perihelion = (semimajor axis) * ((1) - (excentricity))
Aphelion = (semimajor axis) * ((1) + (excentricity))
Excentricity = (1) - ((perihelion) / (semimajor axis))
Osculating elements
-----------------
The orbital elements of asteroids mutate quickly, typicly over
decades. Osculating elements are the instantaneous values of the
elements for a given moment. they are valid for only a short time,
within the current lap of the orbit. It is wise to use in most
planetarium programs the osculating elements valid for an epoch close
to the period of simulation.
The files of asteroid elements available from planetarium author
and the Minor Planet Center wwbsites are the osculating elements and
must be replaced every couple years.
Mean elements
-----------
Mean elements are those elements smoothed out to simulate an
asteroid for many decades. The are cleared of shortterm deviations
from the planets circulating around the Sun and tugging at the
asteroid from all directions. However, to use them properly, a true
dynamical model of the solar system is required. It moves the asteroid
under gravity from the planets and will yield at a given moment the
osculating elements.
Proper elements
-------------
For studies of asteroids over geologic or astronomic time, a
refined set of elements is required. They account for the longterm
changes in the planet orbits. For the larger asteroids, the proper
elements are close to mean elements. However, they can be quite
different from values of the osculating elements for a given moment.
The intent of the proper elements is to give elements for an
asteroid as if it was in a pure two-body dynamical situation just it
and the Sun without the other planets. To this end they are artificial
and do not directly relate to the current behavior of the asteroid.
Because there is no generally agreed method for deriving proper
elements, sources will offer different sets. Articles in astronomy
journals present new or alternative approaches for obtaining proper
elements, with comparison with existing sets.
Proper elements can be used only by a high-powered dynamical
model, not the level commonly run on home computers. hence, they
should NOT be the input to a planetarium or dynamic model; the
resulting trajectory and ephemeris will be entirely wrong.
Proper elements are about as good a 'book' set of elements there
is, without having to issue now ones like for mean or osculating
elements. Thus, they are handy for statistical analyses of asteroids
and the detection of groups.
Usually only the semimajor axis, inclination, and excentricity are
computed as proper elements. The proper elements remain constant in
the sense that they can begin a simulation at any point of time,
backward or forward many millions of years. They will modify into the
osculating elements at any given moment during the simulation.
Names of groups
-------------
A group is named for a prototype member in that group. This may be
the most important, best studied, brightest, largest, or first
discovered. There is no rule for picking a prototype, the name
settling in by general consensus among astronomers. In rare cases, the
group name doesn't come from an actual asteroid of that name, due to
historical quirk.
Kirkwood gaps
-----------
In 1874 Kirkwood discovered that there were certain distances from
the Sun where there were no or very few asteroids. Asteroids seem to
avoid these specific distances and bunch up away from them. It's a bit
of amazement that he figured this out with the only 200ish asteroids
known is his day. In fact, he recognized that certain other gaps were
possible but there were not enough asteroids to show them up.
Kirkwood explained the avoided distances as those having simple
ratios of orbital period with Jupiter, like 2/5 or 1/3. For the 1/3
case, the asteroid period is 1/3 Jupiter year, so every third
revolution of the asteroid finds it in conjunction with Jupiter at the
same longitude around the Sun. Thus, every third lap, Jupiter's tug of
gravity pulls it a bit farther away from the Sun, out of the orbit at
the 1/3 distance.
This tug is cumulative, where tugs in other directions tend to net
out over a revolution of the asteroid and Jupiter. After a few rounds,
the asteroid is deposited in a new orbit at such distance that disrupts
the simple ratio. The 1/3 place is in time sweeped clear of asteroids,
forming one of the Kirkwood gaps.
In the table below, some groups appear to sit in or very close to
a Kirkwood gap. However, this is misleading from just the semimajor
axis. Semimajor axis for asteroids can be a distance from the Sun
rarely occupied by the asteroid during its rounds. In fact, such
asteroids 'in a Kirkwood gap' have high excentricity so they are
carried in and out of the gap, messing up the chances of always being
tugged by Jupiter at each conjunction. Any low excentricity asteroids
that once were in the gap were, yes, eventually sweeped away.
Resonance
-------
The ratio of one planet period to that of an other creates a
resonance situation. When the one planet is extremely small compared
to the other, like an asteroid against a Jupiter, the little body can
suffer badly under the resonance mechanism.
Resonance is cited in four[!] ways, which can be hideously
confusing if not clearly explained. Two are based on rounds of the
bodies's orbit and two are based on the bodies's periods. In all four
cases, the resonance may be written as a fraction or a proportion. So,
there are in all EIGHT ways you may see, in different articles, the
one and same resonance case.
To give the resonance by laps we state the laps of the one body
versus the laps of the other. If an asteroid makes three rounds of its
orbit while Jupiter makes two in its own, we say the asteroid is in a
3/2 or 3:2 resonance with Jupiter. The first number applies to the
asteroid; the second, Jupiter.
Some authors bank off of Jupiter and say the asteroid is in a 2/3
or 2:3 resonance. All four of these statements are valid, provided you
are explicit about which you are using.
Similar reasoning applies to the method of periods. The asteroid,
by comparing period of revolution, is in a 2/3, 2:3, 3/2, 3:2
resonance with Jupiter.
To sort out things, we have
--------------------
Jupiter asteroid
viewpoint viewpoint
--------- ----------
periods
fraction 2/3 3/2
proportn 2:3 3:2
laps
fraction 3/2 2/3
proportn 3:2 2:3
------------------------------
Jupiter the sweeper
-----------------
Jupiter, being the most massive of the planets, more than every
other solar system body combined (except, of course, the Sun), exerts
a strong gravity influence over a wide sector around him. Woe be to
the comet who wanders within 2 AU of Jupiter. Asteroids are more
resistent to Jupiter's gravity by running in more or less stable
orbits around the Sun in the asteroid belt. The pull of Jupiter comes
from the whole 360 degree circle around the asteroid and from varying
distances. The pulls net out in the short term, leaving minor
oscillations of the asteroid's orbital elements. A comet pulled by
Jupiter has no chance to 'undo' the distortion by a future pass within
a few months or years, so its orbit is permanently changed. There are
exceptions for short-period comets, like Oterma and Helin-Roman-
Crockett, whose orbits are radicly altered several times by Jupiter
within decades.
When asteroids are caught in a resonance situation, in or near the
Kirkwood gaps, they can suffer major orbit distortion. On each
occurrence of conjunction with Jupiter the asteroid suffers an
unbalanced extra pull, both in direction and strength. The
accumulation of these tugs draws the asteroid out of the resonant
orbit into one where the resonance is broken, there no longer being a
simple ratio of the two periods or laps.
The result is that the Kirkwood gaps are sweeped clean of
asteroids, save for those that pass thru in severely excentric orbits
and do not repeatedly suffer the resonant pulls.
Beyond 4.05 AU Jupiter's gravity is so strong that no stable
asteroid circular or low-excentricity orbit is possible. This region
of the solar system (plus a similar one beyond Jupiter) is devoid of
permanent residents. Thule, the only known asteroid to inhabit this
'forbidden zone', is in an unstable orbit that will decay within a few
decades or a century. The asteroid will eventually drop lower into the
main belt or be veered outward beyond Jupiter, depending on the exact
dynamical simulation you rely on.
Earth & Mars resonance
-------------------
Besides Jupiter, both Earth and Mars can create resonance with
asteroids in the inner region of the asteroid belt. These are far
weaker than Jupiter resonances, but given enough time, they are
effective in shifting asteroids away from certain radii from the Sun.
Earth coorbiters
--------------
Several asteroids have orbits almost coincident with Earth's but I
found no generally agreed name for this group. Here I call it the
Cruithne group, after perhaps the most famous of its members. There is
likely no danger of collision, except if the orbit is disturbed by an
other planet, because a Cruithne asteroid never actually gets too
close to Earth.
A Cruithne asteroid may start in an orbit just larger than
Earth's, say with a period of 366.25 days versus Earth's 365.25. If we
start with the two bodies in superior conjunction, the asteroid seems
from Earth's eye to plod slowly thru the stars, falling behind in the
stars by about 1 degree of heliocentric longitude per year.
Eventually, after some 180 Earth years, the asteroid is a few million
kilometers ahead of earth, with Earth still gaining on it.
Earth's gravity than pulls the asteroid back, slowing it and
making it fall into a lower heliocentric orbit, within that of
Earth's. The asteroid now has a period of, say, 364.25 days. It pulls
ahead of earth, 1 degree per year, to migrate away, round the Sun to
superior conjunction, continue round to chase Earth from behind.
When it gets within hailing distance of Earth, Earth's gravity
pulls the asteroid forward, speeding it and shifting it to a slightly
higher orbit. This has the 366.25 day orbit, and the see-saw motion
repeats.
A solar system plot of such an asteroid resembles a C-shape toilet
seat, with the cutout at Earth! The asteroid runs faster than Earth
along the inner edge of the toilet seat, loops around the cutout, runs
slower than Earth along the outer edge, loops around the opposite side
of the cutout, and so on. Some folk, for politeness sake, call this a
horseshoe orbit, altho it hardly looks like any shoe a respectable
horde will kindly wear.
The usual solar system diagram and descriptions are really tricky
to interpret correctly. You really should simulate a Cruithne asteroid
with a solar system dynamics program. No, you can not use a 'trolley
track' model, even if using current elements. The resulting path over
even a few years will be totally wrong.
In fact, the asteroid makes this round and back motion ONLY as
viewed from Earth. it DOES NOT shift back and forth relative to the
Sun. What the Sun sees is a normal prograde asteroid that indexes
between one, faster-than-Earth, orbit and an other, slower=than=Earth,
orbit, but always moving prograde thru the zodiac.
Earth=threats
-----------
If an asteroid's orbit can graze or cross that of Earth, that
asteroid can be a threat to Earth by collision. This is true even if
there is a substantial inclination so the asteroid usually passes
north or south of Earth when crossing Earth's orbit. That's because
the inclination can be shifted by perturbations from other planets,
including Earth itself, such that on a future round, we could suffer
the collision.
There are four cases of threat: Apohele, Aten, Apollo, and Amor.
The last three are named for actual members of their groups. The
Apohele asteroid group is named for an asteroid that was not confirmed
after discovery. For several years, there were no other members of the
Apohele group. By now, 2008, there are five or six members, but none
are actually named Apohele.
Apohele
-----
The Apohele asteroid orbits entirely within Earth's orbit with its
aphelion at Earth's perihelion. That is, when an Apohele is farthest
from the Sun, it COULD meet Earth when Earth is at perihelion. The two
orbits are tangent, altho it will be some long while before both
bodies are simultaneously at the common point.
It is extremely tough to find and track an Apohele because it, in
Earth's sky, are for the most part of their orbit in daylight or
strong twilight. Their greatest elongation from the Sun is 90 degrees,
at which point the asteroid is REALLY close to us.
They also are seen only in partial phase, no greater than half-
full. This, with the highly textures surface, makes an Apohele among
the faintest of asteroids.
Aten
--
An Aten asteroid has a semimajor axis less than Earth's but an
aphelion greater than Earth's. This may be hard to visualize at first:
How can an asteroid with a smaller orbit than Earth's cross Earth's
orbit? The trick is in the excentricity, shown by a made-up example.
Suppose an Aten has an SMA of 0.8 AU, against Earth's 1.0 AU. Also
allow that its excentricity is such that the perihelion distance of
the asteroid is 0.3 AU. Such an asteroid would have an excentricity of
0.625.
Adding twice the SMA to the perihelion gives the aphelion, so we
have ((2)*(0.8))+(0.3) = 1.1 AU. This example asteroid can ride 0.1
AU, about 15 million kilometers, beyond Earth, It could strike us on
the outward rise to aphelion or on the inward fall from there.
Apollo
----
An Apollo asteroid has SMA greater than Earth's and crosses her
orbit. This is the easy situation to visualize. The meet can be at
either the inward or outward segment of the Apollo trajectory.
Amor
--
an Amor asteroid has SMA greater than Earth's and its perihelion
at Earth's aphelion. The orbits are tangent This is the inversion of
the Apohele case, but there are a lot of members in the Amor group.
The Earth collision can occur when an Amor rounds its perihelion.
SMA and period
------------
An equivalent definition of the Earth-threat asteroids is based on
orbital period. Since the period is a direct relation to the semimajor
axis, the two definitions are commutable. For period in Earth year's
and semimajor axis in AU, the two are related by
(period) = (semimajor axis)^(3/2)
(smeimajor axis) = (period)^(2/3)
Thus the Atens and Apoheles have periods less than Earth's, less than
one year, while the Apollos and Amors have periods more than one year.
Parameter limits
--------------
The range of the orbit elements defining a group differs among
authors because they are not truly hard and sharp frontiers. The best
agreed boundaries are those of semimajor axis. Plots of asteroids
generally show firm delimitation between groups along SMA, making
vertical banding in the graphs (SMA on horizontal axis).
The borders for excentricity and inclination are more diffuse.
Authors may take as a limit the extreme values, a value enclosing some
greater percent of group members, a statistical average, and so on.
You may find else where limits for excentricity and inclination
that appear to disagree with the ones in the table here.
Hilda
---
This group of asteroids hovers near 4 AU from the Sun in strongly
excentric orbits. Any that were in a low-excentricity orbit were
sweeped away long ago. The Hilda asteroid survives because its orbit
adjusted to put the aphelion far from Jupiter, where it would
otherwise put it within a fractional AU from the planet for a certain
death.
The aphelia of the Hilda group are at 60, 180, and 300 degree
longitudinal separation around the Sun from Jupiter. The perihelia are
at 0, 120, 240 degrees. The 0 degree perihelion is close to Jupiter
but the asteroid is moving fast enough to get away to a safe distance
quickly.
The Hilda group is a good example of an asteroid orbit that is
hardly static at all. Old elements of a Hilda will produce
utterly wrong trajectories. The entire orbit migrates in step with
Jupiter to keep the line of apsides, joining perihelion and aphelion,
at the stated separations from Jupiter.
A given Hilda has an orbit aligned to ONE of the three longitude
displacements and that orbit slews around the Sun pacing Jupiter.
Collectively, the Hilda group sorted itself out into the three sets of
orbit.
The 60-degree and 300-degree aphelia of a Hilda touches the inner
edge of the Trojans, but there is no chance of either group losing
members to the other. A Trojan moves too quickly to drop down into a
Hilda orbit and a Hilda moves too slowly to be caught up with the
Trojans. The members of both groups, altho mixed together at about 4.8
AU from the Sun, bypass each other without interaction.
Trojan
-----
Stricta ments the Trojan group is uniquely associated with
Jupiter. However, the name is applied to similar dynamical groups
attached to other planets. Only the Jupiter Trojans have members named
for participants of the Trojan War.
A loose descriptions of a Trojan is that they sit 60 degrees ahead
and behind Jupiter in the planet's orbit. These points are also
defined as the Lagrange libration points L4 (ahead) and L5 (behind).
This is false in the general case because no planet has a true
circular orbit. The definition is the equilateral triangle
configurations of asteroid, planet, Sun, regardless of where the
asteroid point of the triangle is relative to the orbit of the planet.
There are two triangles, one with its asteroids lagging the planet;
the other, leading. The L4 and L5 points are at the points of the
triangles
In the case of a strongly excentric planet orbit, the Trojans may
be an unstable group because the gravity regime around them is in
constant flux.
Among the planets in 2007, Jupiter, Mars, and Neptune have Trojan
asteroids. Earth is suspected to have Trojans but none as yet have
been found.
Table of asteroid groups
----------------------
The table here is arranged in ascending order of semimajor axis.
Mind well that the limits for the parameters may differ from those
cited by other authors.
------------------------------------------------------------
group | SMA (AU) | exc | inc | prototype | remarks
---------+----------+-------+-------+--------------+------------
Vulanoid | Q<0.4 | N/A | --- | none yet | within Mercury
Apohele | <1, Q=.98| --- | ~0 | 1998-DK36 | Earth grazer
Aten | <1, Q>.98| --- | ~0 | 2062 Aten | Earth crosser
Cruithne | 1 | 0 | ~0 | 3753 Cruithne| Earth coorbiter
Earth Tj | 1 | ~0 | ~0 | none yet | At L4 & L5
Amor |>1, q=1.02| --- | ~0 | 1221 Amor | Earth grazer
Apollo |>1, q<1.02| --- | ~0 | 1862 Apollo | Earth crosser
Mars Tj | 1.52 | ~0 | ~0 | 5261 Eureka | At L4 & L5
Hungaria | 1.78-2 | <.18 | 16-34 | 434 Hungaria | 9:2 resonance
Kirkwood | 1.9 | --- | --- | gap | 9:2 resonance
Kirkwood | 2.06 | --- | --- | gap | 4:1 resonance
Flora | 2.15-2.35|.03-.23|1.5-8.0| 8 Flora | 4:9 Mars res
Kirkwood | 2.25 | --- | --- | gap | 7:2 resonance
Phocaea | 2.25-2.5 | >.10 | 18-32 | 25 Phocaea |
Nysa | 2.41-2.5 |.12-.21|1.5-4.3| 44 Nysa | AKA Hertha
Kirkwood | 2.50 | --- | --- | gap | 3:1 resonance
Alinda | 2.5 | .4-.65| --- | 887 Alinda | 1:4 Earth res
Maria | 2.5-2.71 | --- | 12-17 | 170 Maria |
Eunomia | 2.53-2.72|.08-.22| 11-16 | 15 Eunomia | family?
Adeona | 2.66-2.69| <.18 | 0-21 | 145 Adonia | family?
Pallas | 2.7-2.82 | --- | 33-38 | 2 Pallas |
Kirkwood | 2.71 | --- | --- | gap | 8:3 resonance
Dora | 2.76-2.81| <.2 | 0-14 | 668 Dora | family?
Kirkwood | 2.82 | --- | --- | gap | 5:2 resonance
Koronis | 2.83-2.91| 0-.11 | 0-3.5 | 158 Koronis | family?
Kirkwood | 2.95 | --- | --- | gap | 7:3 resonance
Eos | 2.99-3.03|.01-.13| 8-12 | 221 Eos | family?
Themis | 3.08-3.24|.09-.22| 0-3 | 24 Themis | family?
Griqua | 3.1-3.27 | >.35 | >20 | 1362 Griqua |
Hygiea | 3.06-3.24|.09-.19|3.5-6.8| 10 Hygiea | family?
Kirkwood | 3.27 | --- | --- | gap | 2:1 resonance
Cybele | 3.27-3.7 | <.3 | 0-25 | 55 Cybele | 7:4 resonance
Kirkwood | 3.7 | --- | --- | gap | 5:3 resonance
Hilda | 3.7-4.2 | >.07 | 0-20 | 153 Hilda | 3:2 resonance
forbidden| 4.05-5.0 | --- | --- | gap | empty
Thule | 4.2 | --- | --- | 279 Thule | unstable 4:3 res
Trojan | 5.05-5.4 | ~0 | --- | 588 Achilles | At L4 & L5
---------+----------+-------+-------+--------------+------------