LONEOS Discovers Asteroid with the Smallest Orbit (2004 JG6)

http://www.lowell.edu/press_room/rel...04JG6_rls.html

Lowell Observatory
For Immediate Release

May 20, 2004

contact: Steele Wotkyns
(928) 233-3232


LONEOS Discovers Asteroid with the Smallest Orbit

Flagstaff, AZ-The ongoing search for near-Earth asteroids at Lowell
Observatory has yielded another interesting object. Designated 2004 JG6,
this asteroid was found in the course of LONEOS (the Lowell Observatory
Near-Earth Object Search) on the evening of May 10 by observer Brian Skiff.

"I immediately noticed the unusual motion," said Skiff, "so it was certain
that it was of more than ordinary interest." He quickly reported it to the
Minor Planet Center (MPC) in Cambridge MA, which acts as an international
clearinghouse for asteroid and comet discoveries. The MPC then posted it on
a Web page for verification by astronomers worldwide. It happened that all
the initial follow up observations, however, were obtained by amateur and
professional observers in the Southwest US. The additional sky positions
measured in the ensuing few days allowed an orbit to be calculated.

The official discovery announcement and preliminary orbit were published by
the MPC on May 13. This showed that the object was located between Earth and
Venus (presently the very bright "evening star" in the western sky). In
addition, 2004 JG6 goes around the Sun in just six months, making it the
asteroid with the shortest known orbital period. Ordinary asteroids are
located between the orbits of Mars and Jupiter, roughly two to four times
farther from the Sun than Earth, taking several years to go around the Sun.

Instead, 2004 JG6 orbits entirely within Earth's orbit, only the second
object so far found to do so. "What makes this asteroid unique is that, on
average, it is the second closest solar system object orbiting the Sun,"
said Edward Bowell, LONEOS Director. Only planet Mercury orbits closer to
the Sun.

As shown in the included diagram, JG6 crosses the orbits of Venus and
Mercury, passing less than 30 million miles from the Sun every six months.
The approximate average orbital speed of this asteroid is more than 30
km/sec, or 67,000 miles per hour. Depending on their locations, the asteroid
may pass as close as 3.5 million miles from Earth and about 2 million miles
from planet Mercury. In the coming weeks 2004 JG6 will pass between Earth
and the Sun, just inside Earth's orbit. It will move through the
constellations Cancer and Canis Minor low in the western sky at dusk.
Because of the near-exact six-month period, the asteroid should be
observable again in nearly the same spot in the sky next May, having gone
around the Sun twice while Earth will have made only one circuit.

From present estimates, 2004 JG6 is probably between 500 meters and 1 km in
diameter. Despite its proximity, the object poses no danger of colliding
with Earth.

Asteroids with orbits entirely within the Earth's orbit have been informally
called "Apoheles," from the Hawaiian word for orbit. Apohele also has Greek
roots: "apo" for outside, and "heli" for Sun. Objects orbiting entirely
within Earth's orbit are thought by dynamicist William F. Bottke of
Southwest Research Institute and colleagues to comprise just two percent of
the total near-Earth object population, making them rare as well as
difficult to discover. This is because they stay in the daylight sky almost
all of the time. There may exist about 50 Apoheles of comparable size to or
larger than 2004 JG6, but many of them are certain to be unobservable from
the ground.

The first asteroid found entirely inside Earth's orbit was 2003 CP20, found
just over a year ago by the NASA-funded Lincoln Laboratory Near-Earth
Asteroid Research project, which observes near Socorro, New Mexico. Although
larger than 2004 JG6, 2003 CP20 is a little more distant from the Sun.

LONEOS is one of five programs funded by NASA to search for asteroids and
comets that may approach our planet closely. The NASA program's current goal
is to discover 90 percent of near-Earth asteroids larger than 1 km in
diameter by 2008. There are thought to be about 1,100 such asteroids.

#END#

For additional information:

LONEOS = http://asteroid.lowell.edu/asteroid/...neos_disc.html
MPC = http://cfa-www.harvard.edu/iau/mpc.html
MPC's official discovery announcement:
http://cfa-www.harvard.edu/mpec/K04/K04J60.html
JPL orbit diagram/animations:
http://neo.jpl.nasa.gov/cgi-bin/db_shm?sstr=2004+JG6 (for best results, copy
and paste URL into browser)
Static view of 2004 JG6 by Tom Polakis :
http://www.psiaz.com/polakis/misc/2004JG6.jpg

Diagram of 2004 JG6 by Larry Wasserman, Astronomer, Lowell Observatory (a
pdf)

Ron (or somebody else of the same name) wrote in message
thusly:

Because of the near-exact six-month period, the asteroid should be
observable again in nearly the same spot in the sky next May, having gone
around the Sun twice while Earth will have made only one circuit.

Presumably inferior conjunction occurs every year. Always in May, or does it
slowly wander through the year?

Has a transit schedule been worked out? Would a transit of something so
small, be observable with current technology?

--
Paul Townsend
I put it down there, and when I went back to it, there it was GONE!

Interchange the alphabetic elements to reply

In article ,
Prai Jei wrote:

Ron (or somebody else of the same name) wrote in message
thusly:

Because of the near-exact six-month period, the asteroid should be
observable again in nearly the same spot in the sky next May, having gone
around the Sun twice while Earth will have made only one circuit.

Presumably inferior conjunction occurs every year. Always in May, or does it
slowly wander through the year?

It's too early to tell - refined orbital elements are needed before one
can conclude whether this body is in resonance with the Earth or not.

Has a transit schedule been worked out? Would a transit of something so
small, be observable with current technology?

It would definitely be too small to observe in transit: the apparent
diameter of this body, when it's closest to the Earth, is expected to
be between 0.03 and 0.06 arc seconds.

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://www.stjarnhimlen.se/
http://home.tiscali.se/pausch/

In article ,
(Paul Schlyter) writes:
It would definitely be too small to observe in transit: the apparent
diameter of this body, when it's closest to the Earth, is expected to
be between 0.03 and 0.06 arc seconds.

Are you sure that's too small? What's the angular resolution of
solar telescopes these days? Observing a transit doesn't require
resolving the asteroid disk, only detecting the brightness decrease
it causes. That depends on signal to noise, which is probably
limited by variations in the solar surface brightness. I don't know
the numbers, but it isn't obvious to me that the observation is
impossible.

Even if a transit is observable, I'm not sure what its scientific
value would be. Presumably it would determine the asteroid diameter,
but is there much value in that? On the other hand, if a solar
telescope is observing the Sun anyway, you get the transit
observation "for free," so why not make use of it?

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
valid Reply-To address to receive an acknowledgement. Commercial
email may be sent to your ISP.)

In article , (Steve Willner) writes:
In article ,
(Paul Schlyter) writes:
It would definitely be too small to observe in transit: the apparent
diameter of this body, when it's closest to the Earth, is expected to
be between 0.03 and 0.06 arc seconds.

Are you sure that's too small? What's the angular resolution of
solar telescopes these days? Observing a transit doesn't require
resolving the asteroid disk, only detecting the brightness decrease
it causes. That depends on signal to noise, which is probably
limited by variations in the solar surface brightness. I don't know
the numbers, but it isn't obvious to me that the observation is
impossible.


Currently, solar telescopes using state of the art adaptive optics systems
are achieving resolutions on the order of 0.15 arc seconds over relatively
small fields of view. The solar telescopes producing the best images have
effective diameters of about 1 meter. The proposed Advanced Technology
Solar Telescope (ATST) is a 4 meter class telescope designed to have a
resolution of 0.03 arc seconds at 550 nm.

The contrast of the granular structures on the Sun is a few percent. Many
solar observations are photon limited and signal to noise suffers from a
lack of photons. This is due to a lot of our observations are taken at
very high spectral resolution (spectrographs having a spectral resolution of
delta lambda/lambda 1,000,000 are not uncommon and imaging systems having
a spectral resolution of delta lambda/lambda on the order of 250,000 exist).
An additional complication is that we also desire very short exposure times
(a few milliseconds) to reduce image blur due to seeing and to properly
sample the changes with time of solar structure.

Even if a transit is observable, I'm not sure what its scientific
value would be. Presumably it would determine the asteroid diameter,
but is there much value in that? On the other hand, if a solar
telescope is observing the Sun anyway, you get the transit
observation "for free," so why not make use of it?


Transits and eclipses are useful to measure scattered light in our optical
systems. In any case, I don't think a transit of a body 0.06 arc seconds
in diameter could be seen anytime in the foreseeable future.

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
valid Reply-To address to receive an acknowledgement. Commercial
email may be sent to your ISP.)



__________________________________________________ ______________________
Craig A. Gullixson
Instrument Engineer INTERNET:
National Solar Observatory/Sac. Peak PHONE: (505) 434-7065
Sunspot, NM 88349 USA FAX: (505) 434-7029

In article ,
(Craig Gullixson) writes:
Currently, solar telescopes using state of the art adaptive optics systems
are achieving resolutions on the order of 0.15 arc seconds over relatively
small fields of view. The solar telescopes producing the best images have
effective diameters of about 1 meter. The proposed Advanced Technology
Solar Telescope (ATST) is a 4 meter class telescope designed to have a
resolution of 0.03 arc seconds at 550 nm.

Thanks. I hadn't heard about ATST. Amazing!

The contrast of the granular structures on the Sun is a few percent. Many
solar observations are photon limited and signal to noise suffers from a
lack of photons. This is due to a lot of our observations are taken at
very high spectral resolution (spectrographs having a spectral resolution of
delta lambda/lambda 1,000,000 are not uncommon and imaging systems having
a spectral resolution of delta lambda/lambda on the order of 250,000 exist).

For transit observations of an asteroid -- the original topic of this
thread -- presumably one would use a broad bandwidth. Of course that
precludes the telescope's normal program so there would have to be
scientific merit to a transit observation for it to be considered for
scheduling.

I must admit that for a nighttime astronomer like me, the concept of
solar observations being photon-starved is a bit mind-boggling. (Not
that I doubt you!)

An additional complication is that we also desire very short exposure times
(a few milliseconds) to reduce image blur due to seeing and to properly
sample the changes with time of solar structure.

For transit observations, many minutes or hours of data could be
added together. All in all, it seems the observations would be
limited by the contrast of the solar surface.

Transits and eclipses are useful to measure scattered light in our optical
systems.

That seems a hard way to do it, although I don't suppose there are
any easy ways.

In any case, I don't think a transit of a body 0.06 arc seconds
in diameter could be seen anytime in the foreseeable future.

Based on what you have written above, observing such a transit seems
trivial for ATST. The asteroid in transit would be fully black for
the equivalent of four spatial resolution elements. Even with
current solar telescopes, the observation looks possible. The
brightness in a single resolution element would be diminished by 16%,
several times the contrast fluctuations, and this location of
diminished brightness would cross the solar disk in a predictable
way. Wouldn't you expect that to be detectable?

Mind you, I'm not advocating for or against a potential observation,
just wondering about feasibility.

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
valid Reply-To address to receive an acknowledgement. Commercial
email may be sent to your ISP.)

In article , (Steve Willner) writes:
In article ,
(Craig Gullixson) writes:
Currently, solar telescopes using state of the art adaptive optics systems
are achieving resolutions on the order of 0.15 arc seconds over relatively
small fields of view. The solar telescopes producing the best images have
effective diameters of about 1 meter. The proposed Advanced Technology
Solar Telescope (ATST) is a 4 meter class telescope designed to have a
resolution of 0.03 arc seconds at 550 nm.

Thanks. I hadn't heard about ATST. Amazing!

The contrast of the granular structures on the Sun is a few percent. Many
solar observations are photon limited and signal to noise suffers from a
lack of photons. This is due to a lot of our observations are taken at
very high spectral resolution (spectrographs having a spectral resolution of
delta lambda/lambda 1,000,000 are not uncommon and imaging systems having
a spectral resolution of delta lambda/lambda on the order of 250,000 exist).

For transit observations of an asteroid -- the original topic of this
thread -- presumably one would use a broad bandwidth. Of course that
precludes the telescope's normal program so there would have to be
scientific merit to a transit observation for it to be considered for
scheduling.

Broad band for us tends to be about 1 nm. Remember we are also geared for
high temporal resolution, so that constrains the maximum bandwidths we use.
Broad band in the nighttime sense, 10 to 100 nm, can break optics and cause
flames in this business.


I must admit that for a nighttime astronomer like me, the concept of
solar observations being photon-starved is a bit mind-boggling. (Not
that I doubt you!)

I started out on the dark side, so it suprised me also.


An additional complication is that we also desire very short exposure times
(a few milliseconds) to reduce image blur due to seeing and to properly
sample the changes with time of solar structure.

For transit observations, many minutes or hours of data could be
added together. All in all, it seems the observations would be
limited by the contrast of the solar surface.

You also have scattered light from the atmosphere, scattered light from
the telescope and instrumentation. Even with AO, very good seeing would
be required to achieve 0.03 arcsecond resolution. Finally, the surface
structure of the sun changes with time.


Transits and eclipses are useful to measure scattered light in our optical
systems.

That seems a hard way to do it, although I don't suppose there are
any easy ways.

In any case, I don't think a transit of a body 0.06 arc seconds
in diameter could be seen anytime in the foreseeable future.

Based on what you have written above, observing such a transit seems
trivial for ATST. The asteroid in transit would be fully black for
the equivalent of four spatial resolution elements. Even with
current solar telescopes, the observation looks possible. The
brightness in a single resolution element would be diminished by 16%,
several times the contrast fluctuations, and this location of
diminished brightness would cross the solar disk in a predictable
way. Wouldn't you expect that to be detectable?

I think it would be really tough. If the seeing was good and the atmospheric
scatter was really small and the orbit of the object was known well enough
that one could blind track the object and sum a bunch of images, perhaps it
could be done with ATST.


Mind you, I'm not advocating for or against a potential observation,
just wondering about feasibility.

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
valid Reply-To address to receive an acknowledgement. Commercial
email may be sent to your ISP.)


__________________________________________________ ______________________
Craig A. Gullixson
Instrument Engineer INTERNET:
National Solar Observatory/Sac. Peak PHONE: (505) 434-7065
Sunspot, NM 88349 USA FAX: (505) 434-7029