Newly Discovered PHA's

[MeteorWayne]

The purpose of this topic is to provide a repository for newly discovered Potentially Hazardous Asteroids with high Palermo Scale rankings (Say -3 or higher?). They'll stay here until they either drift down in risk (when we'll stop talking about them), or if the risk stays sustained for a time, when we will create a dedicated thread as we have for interesting asteroids in the past.

There's a separate thread for close approaches to earth (< 2 Lunar Distance); occasionally an object will appear in both topics.

MW

 

[silylene]

Wayne, good idea on a thread devoted to this subject. A collision by 2009 YG would be devastating. Anyways, with more data it appears the chances of collision are decreasing further.

 

[MeteorWayne]

Off topic, but I have reviewed the asteroids on JPL's Sentry risk page with listed risk for 2010. There are 7.
Here's the list from the highest risk to the lowest:
2008 AO112 (Cumulative PS -4.30, 2010 -4.62) [310 meters]
2007 YM (Cumulative -5.20, 2010 -5.32) [20m]
2008 EM68 (-5.21, -5.57) [10m]
2004 FU162 (-5.32,-6.01) [6m]
2005 TM173 (-5.44,-6.37) [50m]
2007 UO6 (-5.63,-6.13) [12m]
2008 VL (-6.50,-8.00) [8m]

All can be considered lost. The longest arc is 2.00 days (2007 VO6), the shortest 0.03 day (2004 FU162). In total for all 7 there are only 59 observations (Max 12 for 2007 YM and 2008 EM68; Min 4 for 2004 FU162), and the total arc for all 7 combined is only 5.35 days. IOW, the only reason they are even on the risk page is because there are too few observations to exclude them.

 

[R1]

What does it mean they're lost? They will have to be discovered again with
new initials of the time?

[Good idea about a dedicated threat to potentially hazardous asteroids, will the thread be pinned
to the top? I did not know what PHA stood for initially, ( PeriHelion Asteroids? ) but now I do.]

 

[MeteorWayne]

What I mean by lost is they were never observed since the original fraction of a day or two days.

What would happen is that if found again, they might indeed be given a new designation temporarily, but once the orbits match (if the match is close enough) they would be identified as the same object and the original designation would apply. However, with the very short observation periods on first discovery, it might be impossible to positively ID them again. Still, with the ever improving search campaigns, it would be most likely that a rediscovery (especially for the largest one, 2008 AO112, ~ 310 meters) would obtain a sufficiently precise orbit that a positive match would be likely.

I have gone back and added the size (best guess of the center of the range) to the list. 2005 TM173 is 50 meters, the rest are tiny.

 

[MeteorWayne]

Today's data has 2009 YG as a Torino Scale 1 for the 2050 virtual impactor on NEODyS, so l will start a dedicated thread and move the 2009 YG posts to it.

MW

 

[silylene]

MW, thanks. I rather like this system of organizing the NEO's.

 

[MeteorWayne]

Thanx silylene. Sometimes organization is a good thing

 

[MeteorWayne]

Noticed this on the JPL small body database today:

2003 SE308 = 2009 YE9

Apparently old images have been identified as the same object. While this is not a PHA (it is a Main Belt asteroid), it shows how the process works...

 

[MeteorWayne]

Technically:

PHAs
Potentially Hazardous Asteriods: NEAs whose Minimum Orbit Intersection Distance (MOID) with the Earth is 0.05 AU or less and whose absolute magnitude (H) is 22.0 or brighter.

 

[MeteorWayne]

bump

 

[EarthlingX]

I just came across this :
www.cfa.harvard.edu : List Of The Potentially Hazardous Asteroids (PHAs)

and then

Plot of the Innermost Solar System

with some pretty pictures and animations.

 

[MeteorWayne]

A relevant SDC article:

Beware the Small Ones

Put aside the vision of Bruce Willis wrestling with huge space rocks threatening to doom Earth "Armageddon"-style. It turns out that people should be more worried about smaller space rocks that explode in our atmosphere.

While smaller than Earth-busting asteroids, these "airbursters" — like the space rock that exploded in 1908 high over Tunguska, Siberia — are more immediate threats, scientists say. They can cause localized destruction and may intrude in our airspace with little warning time...

Such objects are expected to impact the Earth on average every two to 12 years...

The risks of exploding asteroids and the need to keep watch for hazardous near-Earth objects took center stage at September's Space 2010 conference in California, sponsored by the American Institute of Aeronautics and Astronautics.

"We used to think that the only real threat was from impacts that hit the ground ... and that the atmosphere would protect us from the small ones," said physicist Mark Boslough of Sandia National Laboratories in Albuquerque, N.M. "We never really thought about the physics of airbursts. ... There hasn't been that much research."

...


The classic asteroid event occurred 102 years ago in Tunguska, Boslough said. It involved an object that broke up in a cascading way, leading to a rapidly expanding fireball and subsequent blast wave.

"That blast wave hit the ground, and the wind associated with it was high enough to actually blow over trees," he said.

The downed trees covered at least 2,000 square kilometers (more than 770 square miles) — with no crater associated with the explosion located.

Boslough said that, in his opinion, the Tunguska asteroid was probably a 40-meter (131-foot) object. "Tunguska wasn't the lower threshold. You could imagine something 30 meters (98 feet) across," he said, and in that case, it would explode with a little bit less energy and a little higher in the atmosphere.

"But if you just happened to be directly under it, yes, it could be fatal," Boslough added...

Similar in view was Don Yeomans, manager of NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif.

"We're doing very well with detecting the large ones. But we've got a long way to go for the small ones," Yeomans added.

His message regarding planetary defense:

"We need to find them before they find us."

 

[kg]

A relevant SDC article:

....While smaller than Earth-busting asteroids, these "airbursters" — like the space rock that exploded in 1908 high over Tunguska, Siberia —
The classic asteroid event occurred 102 years ago in Tunguska, Boslough said. It involved an object that broke up in a cascading way, leading to a rapidly expanding fireball and subsequent blast wave.....

Speaking for myself but I think it might be true of most star gazers that if I had been in Tunguska in 1908 I would have stood awestruck watching that object enter the atmosphere untill it exploded and burned out my retnas. Any advice on knowing when it's better to duck and cover instead of observing? Maybe seeing such a rare event is worth going blind?

 

[MeteorWayne]

2010 TM now has it's own thread, since the level of detail being posted by that geek/nerd user Meteor Wayne was cluttering up this one with detail of interest to only a few.

Moderator Meteor Wayne