Tag: Asteroid

NEO 2020 JJ 5/04/20

Another Near Earth Object encounter.  This time with a unique announcement:

Figure 1.

Notice that 2020 JJ has an anomalous distance of encounter of zero AU.  It is rounded off, of course.  The managers of this source will be contacted to encourage more decimal places!  By other sources, I find the “miss” distance to be about 16,200 miles which is indeed less than 0.1 Lunar Distances.

This, again is worthy of a more detailed diagram with a better picture of the Earth (Thanks, NASA!).

The approaching asteroid did not pass across the celestial equator – where all the geosynchronous communication satellites are – but further to the South.

The JPL Small Body Database Browser, which is also the source for the “circle and arrows” diagrams you have seen on these pages, has undoubtedly given us a more accurate figure.  However, it does have some limitations, which are clearly explained in the website:

“This orbit viewer was implemented using two-body methods, and hence should not be used for determining accurate long-term trajectories (over several years or decades) or planetary encounter circumstances.”

https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2000%20CH59;old=0;orb=1;cov=0;log=0;cad=0#orb

The alert readers (most of you) will point out that “planetary encounter circumstances” is exactly what I am talking about.  That statement means that when asteroids get close to a planet, their mutual gravity has a significant effect that is not calculated in this utility.  So, that 16,200 miss distance is not keenly accurate and almost certainly too large.  Not only that, but it also means that the orbit after the near encounter will have been altered.  It will need to be recalculated and replaced in the database.

JPL has a utility for that, called the “Horizons system” and NASA has an organization to keep track of these things (and studies methods to avoid collisions) called the Planetary Defense Coordination Office.  That said, rocks this small (about 13 feet across) are not easily detected far in advance.  They are also less destructive should they fall to Earth.  This one was small compared to the Chelyabinsk meteor.

NEO Encounter April 28, 2020

   In 1979, Skylab – America’s first space station – was falling out of orbit and my sister called me – her space nerd brother – to worry about this thing that she feared would fall on her new baby.  I tried to explain that the Earth is so big and the Skylab so small (relatively speaking) that the chances were nil that any person on Earth would be anywhere near where it fell. 

I went on to point out that there are natural meteorites that fall to Earth constantly and they could amount to the equivalent of thousands of Skylabs every year.  She never worried about those!

After that, she was not just worried – more like terrified!

I have since learned to advise people that they are more likely to be hit by a train, bitten by a shark and struck by lightning – all at the same time – than to be struck by anything falling from the sky.  There is exactly one case of a person being hit by a meteorite.  The lady was badly bruised, but not fatally.

I told you that to blunt the effect of telling you the following:

Another Near Earth Object passed by the Earth on April 28th, 2020.  I have checked a couple of reliable sources and I can tell you that the nearest it came was about 29 thousand miles.  And that sounds like a lot, since the earth itself is only about 8000 miles in diameter,

However, the NEO does come into our “territory” since we have satellites orbiting the Earth.  You might think that satellites are only hundreds of miles above the Earth and that is where you are mistaken.  I decided that those little diagrams with circles and arrows are insufficient for this one.  Please see the diagram in Figure 1 for details.

As you see, the NEO this week is close enough to be of definite interest.  However, it passed to the South of Earth – nowhere near the “belt” of geosynchronous satellites over the equator and over twice as far as the “cloud” of GPS satellites.  And, of course nowhere near the Space Station.

The asteroid is about 60 feet across. Satellites are flimsy aluminum gadgets and would crumble before the NEO. But Space is big and satellites are small.

Hasta Luego,

Steve

https://www.nasa.gov/mission_pages/skylab

Near Earth Object 2020 HF5

April 27, 2020

Another Near Earth Asteroid has zoomed by while no one was looking on April 22nd.   It may surprise the readers to learn that these things are so common that I only consider the ones that pass as close as the Moon to be of interest.  This one was at 0.4 Lunar Distances or about 95,542 miles.

Figure 1

The culprit is 2020 HF5  – a small rock, as asteroids go – that is only 52 feet across.  These encounters are listed at https://spaceweather.com/  – just scroll down a bit to find a table.

The rock in question is very much is roughly the same size as an asteroid that exploded over  Челябинске in Russia on my 58th birthday.  (Feb 15, 2013) . The heat of re-entry, combined with the tremendous air pressure of its hyper-sonic trajectory caused it to explode at 12 to 15 miles above the surface.  

There was a Russian teacher – Yulia Karbysheva – about my age who, like me, had been trained in Civil Defense exercises in elementary school.  They taught us what to do in a nuclear attack. When the meteor lit up the sky, she had her students hide under the desks – as she (and I) had been trained to do.  When the asteroid exploded and the shock wave arrived, it shattered all the windows and sent shards of glass over the desks – with the students safely beneath same.  After almost a half century, that training finally paid off – for the students.  Unfortunately, she was so concerned with the fourth-graders that she remained standing and was seriously injured.  In all, about 112 people were hospitalized, mostly cuts from flying glass.  There were some cases of flash blindness and ultraviolet burns.  Don’t look at the flash!  I learned that instinctively as a welder.

Our more recent visitor was similar in size, but with only about 1/2 the relative velocity as that meteor and would have about the one fourth the explosive potential.  About 117 kilotons – 9 Hiroshima bombs equivalent.

What’s that?   Oh…it’s the town’s name – “Chelyabinsk”.

Hasta Luego,

Steve

Near Earth Object 2020 GH4

April 13, 2020

There is a class of asteroids called NEO’s (Near Earth Objects).  As the name implies they hang around where the Earth does.  None have been found to threaten the Earth with collision, but some come close – if a quarter million miles may be considered “close”.

On April 15th 2020 an NEO designated 2020 NH 4 will pass closer to the Earth than the Moon.  Since its closest approach is still over two hundred thousand miles – about 25 Earth diameters – it is nothing to worry about.  The diagram in figure 1. Shows its trajectory through the Earth-Moon system. 

There is a subclass of NEOs called “Potentially Hazardous Objects” (PHOs), but that requires a diameter of 140 meters and this one is only 18 meters (59 feet) across. 

Figure 1: The Earth, the moon and 2020GH 4

To answer the inevitable question, yes this asteroid, had it hit the Earth, would have made a very big explosion.

To close on a comforting thought, NASA has a Planetary Defense Coordination Office and there are ways to use existing technology to avoid such things.

Use the “Reply” window below for questions, please. If the reply window is not visible, just click on the title at the top of the page. That will bring up the individual post instead of the categorical collection – and with it, a reply window.

Hasta Luego, Steve