Asteroid 2009 SG18 future threat

[MeteorWayne]

As silylene and I discussed yesterday, this asteroid has been climbing in risk for the last few days, so I thought I'd start a threat to watch how future observations change the risk.

For those new to the subject of following potentially dangerous asteroids:

DON'T PANIC!

We have watched quite a few of these, in fact I'll bump up the topic on the last one we followed if you'd like to look at how things usually develop. Future observations always (so far) eliminate the threat and eventually it disappears from the risk page. It's just for fun and education that we follow it in this forum. The arc (observation period) for this asteroid is only 4 days so the uncertainty as to the actual orbit is huge. It is a Torino scale zero, which means:

No Hazard
(White Zone) 0 The likelihood of a collision is zero, or is so low as to be effectively zero. Also applies to small objects such as meteors and bodies that burn up in the atmosphere as well as infrequent meteorite falls that rarely cause damage.

The current cumulative chance of impact for all 33 Potential Impacts between 2019 and 2095 is one in 2.2 million (Palermo Scale -1.99), the highest risk for the 2022 impact is 1 in 5.5 million. (Palermo scale = -2.26)



The asteroid was discovered Sept 21 by the Catalina survey, currently the most prolific in finding NEOs. It is a large asteroid (~900 meters) in a highly inclined (55 degree) very elliptical (e=.55) orbit with perihelion just inside the earth's, and aphelion in the outer asteroid belt near the 2:1 resonance with Jupiter. It is currently about 0.8 AU from earth with closest approach for this orbit 0.662 AU on October 23rd when it will be a very dim magnitude +19.5.

From JPL:
EMOID= 0.00117639
27 obs over 4 days
RMS = 0.55829

 

[435T]

Very Interesting.. Thanks for the thread and updates.

 

[Shpaget]

I can already see a brand new extinction theory developing from this

A well respected scientist calculates that a 900 meters asteroid is about to hit Earth. Unfortunately nothing can stop it since it's orbit is highly irregular and at awkward inclination which makes any attempt to launch counter measures useless.
The threat of this asteroid is calculated to be 0 (zero) on a threat-from-space scale which means almost certain impact.
Duck and cover.

 

[silylene]

I leave on vacation tothe southern Carribean tomorrow for the next 8 fays, and no internet

I will miss the development of the 2009 SG18 saga. But I will seek this thread the day I return!

 

[Boris_Badenov]

900 meters, eh? I wonder if anyone would be willing to figure out what the Dv budget would be to capture it into a stable orbit.
I'd like to see a usable mining body at EML-1 that could be populated with BA-330 modules. :ugeek: :mrgreen:

 

[MeteorWayne]

For an object in this type of orbit, I suspect it would be quite high. The speed relative to earth is 33 km/sec. That's a lot. there are many more asteroids as large or larger whose relative velocity is 10 km/sec or less. And since KE= 1/2 m*v^2, it would require 9 times as much energy to capture it.

 

[Boris_Badenov]

And since KE= 1/2 m*v^2, it would require 9 times as much energy to capture it.

Thats a bundle alright.

 

[MeteorWayne]

Odd sequence of updates; some things that usually update first are behind, others are advanced.

In any case, the threat is plummeting as expected.

Updated with 36 obs over 7 days (through today):

Potential impacts:
11 from 2019-2096

Palermo scale
Cumulative -2.76 1 in 8.3 million
Highest individual event risk: Sept 20 2044 (1 in 23.8 million impact risk)-3.22
EMOID 0.0139451

From JPL Horizons, only updated with data through the 24th:

Closest approach this orbit 0.692 AU Oct 22, Mag +19.5
Plane crossing Oct 19

Current location in sky:

In the Constellation Hercules

 

[lekszikov]

Dear Wayne!

Would you be so kind to explain the EMoid thing? (im a newbie ) I think its in Au (am i right?) , and the smaller Emoid signs a more dangerous Neo. Please say something about this...

(sorry for my bad english, im from midle east europe)

 

[Shpaget]

So, there won't be any world wide panic and mass suicides?
Why did I buy all those inflatable rafts and canned beans?
It's your fault Wayne :evil:

[offtopic]

im from midle east europe

Really? Where from?
We're neighbors.
I'm from Croatia.
[/offtopic]

EDIT:
BTW, welcome

 

[MeteorWayne]

No problem, my bad for not explaining it. I apologize. We've discussed it before but not in this thread. I should have done so.

Yes it is the distance between the orbit of the asteroid, and that of the earth. An impact can only occur if the orbits intersect.

Let me get an official definition... {whirrs and clicks ensue}

Here's a short one...Earth MOID (Minimum Orbit Intersection Distance)

Let's see if I can find a more detailed one {more whirrs and clicks}

Yeah, here's one:

EMoid/Earth MOID
The value (in AU) of the Earth MOID. This is the minimum distance between the orbit of the earth and the minor planet. The MOID value is for the earth (not the earth-moon barycenter) and is for the epoch of the minor-planet orbit. Note that the MOID does not give any information on actual close approaches--you should refer to lists of close encounters for such information. A value less than the radius of the earth does NOT indicate that a hit will occur.

 

[lekszikov]

thanks Wayne!
So the Emoid is just one information, but if its smaller, the neo could come closer to the orbit of the Earth.


I'm from HUngary, from a Little Town , just 30 km to the Croatian-Hungarian border. Maybe we met any time

 

[TimeDog]

im curious, is there a site that gives updates on new discoveries like this or is that sort or information diffused across many astro news sites?

 

[MeteorWayne]

Yes there is (again discussed in many previous threads, but not this one yet).

The easiest to read is this, the JPL (Jet Propulsion Laboratory) "Sentry" website. It automatically takes new positions and creates the most likely orbits and their rsik for future impacts with earth. You can click around at some of the links on this site and get a feel for the process, though our threads on this subject also provide a lot of enlightenment. You can find the definitions for the Torino and Palermo scale assessments of the risk, and learn a heck of a lot more.

http://neo.jpl.nasa.gov/risk/

The other site of value is the NEODyS webpage. It uses a different program to calculate the orbits and asess the risk. In most cases they agree almost completely; it's actually a good quality check to have a different program digest the same observational data. Sometimes one or the other is a few hours ahead.


http://newton.dm.unipi.it/neodys/index.php?pc=4.1

 

[TimeDog]

sweet, thanks. i think im gonna spend the next couple of hours learning how to decipher the data

 

[MeteorWayne]

Great, that's the right thing to do. If you have any questions after that, feel free to ask!

Wayne

 

[MeteorWayne]

Well this asteroid is about to drop off the risk list, so a few parting comments. The Aphelion ("Q" in the elements) is now 4.54 AU, so it appears this asteroid is close to a Jupiter Family comet, except for one fact, it's orbit is retrograde. This indicated the object most likely came from the Kuiper Belt, and it's orbit has been greatly disturbed by Jove.

Have a look here:

http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2009+SG18;orb=1

You can see the highly inclined retrograde orbit. Use the handle on the right to shift the angle of the view.

Cumulative PS is -4.04 (1 in 158 million), Max is -4.47 (2044, 1 in 417 million) and it's down to 11 potential impacts between 2035-2050.

 

[MeteorWayne]

Probably the last day for this rock on the rsik page. Down to 2 potential impacts, both on Sept 20 2044 with combined odds of 1 in 714 million.

Each observation (now 45 over 9 days) seems to make the orbit bigger, and further from the sun. Perihelion is now .986 AU, and aphelion 4.74 AU, Closest approach this year will be 10/22 at 0.703 AU.

 

[MeteorWayne]

Poof, this asteroid has been removed from the risk list.

 

[TimeDog]

excellent

 

[MeteorWayne]

Yeah, but there's plenty more where that came from. Currently #1 among newly discovered objects is 2009 SD229, about half a km wide, impact risk in the 1 in 10 million range, beginning in November 2012. However, it only has 1.4 days of tracking data, so that's a very preliminary orbit.

BTW, that designation 2009 SD229 means it was the 5729th asteroid discovered during the 2 week interval from Sept 16-30. A busy 2 weeks!

MW