Researchers identify a minimoon fireball

phys.org ^ | 12/2/2019 | Bob Tirka

[BenLurkin]

Such objects circle the planet rather than plunge through the atmosphere and into the ground—at least for a time. It is believed most such objects do not circle the Earth for very long—they eventually succumb to gravity and crash through the atmosphere, or are instead flung back into space. As the researchers also note, to date only one such object has ever been recorded circling the Earth—an object named 2006 RH120 was spotted back in 2006 circling the planet—it did so for approximately 11 months before it escaped the Earth's gravity and made its way back into space. Also, only one minimoon fireball has ever been observed—a team running a camera network in Europe spotted one back in 2014. In this new effort, the researchers report a second identification of a TCO blazing through the sky as a fireball prior to hitting the ground.

The researchers found evidence of the fireball by pouring through data from Australia's Desert Fireball Network—a system of cameras (that also captures flight path) set up across the country for the specific purpose of capturing photographic evidence of a minimoon fireball. To find evidence of such a fireball, the researchers studied the photographs looking for evidence of any type of fireball, be it from a meteor or a TCO.

Once found, the team used the flight path data to calculate the trajectory of the blazing object—objects circling the Earth before streaking through the atmosphere will have come in at a smaller angle.

[Steely Tom]

I can understand how an object can approach Earth, get slowed just enough by skimming the atmosphere to then go into a stable (or semi-stable) orbit, and then eventually fall into that atmosphere.

I can't understand how an object — once having done this — can then (some time later) leave Earth orbit and go on about its merry way. Unless it has some sort of propulsion capability.

[Kickass Conservative]

It took off when it noticed some F-18’s approaching.

[tet68]

Not sure about that either.

Maybe it realized it was an election year.

[DannyTN]

It’s mother called.

[17th Miss Regt]

It left due to climate change.

[spudville]

I was wondering how it could be “blazing” in the vacuum of space.

[PapaBear3625]

I can't understand how an object — once having done this — can then (some time later) leave Earth orbit and go on about its merry way. Unless it has some sort of propulsion capability.

I'm going to guess an interaction with the moon might do it.

[fruser1]

It can happen because the atmosphere does not have homogenous density on the fringes. Plus it expands and contracts due to solar variance.

[null and void]

Plus it expands and contracts due to solar variance.

There is no solar variance, ask any pro-climate change scientist!

[Verginius Rufus]

Isaac Newton worked out the laws of gravity but does he explain why there is gravity to begin with? Why do masses attract? You have the earth over here and the moon over there--why don't they just leave each other alone?

We see light from distant galaxies which are billions of light-years away...so the light has been traveling for billions of years. Why doesn't it get tired?

[Phlyer]

I can understand . . . skimming the atmosphere . . . stable (or semi-stable) orbit, and then eventually fall into that atmosphere.

Your questions apply to a two-body problem, which the solar system is not. However, if an object 'skims' the atmosphere (in a two-body problem) it will not enter anything like a stable orbit. If it manages to get back above the atmosphere (doesn't re-enter immediately) then it still has less energy than before it made its skim. The next pass perigee will be no higher, and lose even more energy. It will re-enter in a few orbits at most.

The minimoon situation results from having multiple bodies. Consider an object that is passing by the Earth with barely enough energy to continue without being captured. Then put Jupiter 'behind' the object as it passes the Earth. The object can be slowed down just enough to be captured by the Earth - even without touching the atmosphere.

I can't understand how an object . . .Unless it has some sort of propulsion capability.

This is the same situation in reverse. At some later time, if the minimoon is just passing the Earth when Jupiter is ahead of it, then it can be tugged back into a non-Earth orbit (still in orbit about the sun).

If the minimoon passes again when Jupiter is behind it, even if it didn't skim the atmosphere when it became a minimoon, it can be decelerated enough to enter the atmosphere.

Of course, there are more solar system objects than just Jupiter, and because the Earth's orbit is not a perfect circle, the sun can accelerate objects at just the right moment. If enough effects add up together they don't have to be aligned just as the object is passing the Earth.

The common denominator is that the objects, at least as they are captured or escape, need to be right on the boundary of enough energy to orbit - which is the case if they just wander by in a solar orbit with parameters close to the Earth orbit.

[alexander_busek]

Isaac Newton worked out the laws of gravity but does he explain why there is gravity to begin with? Why do masses attract? You have the earth over here and the moon over there--why don't they just leave each other alone? We see light from distant galaxies which are billions of light-years away...so the light has been traveling for billions of years. Why doesn't it get tired?

Those are some pretty "deep" questions you pose there, Verginius Rufus.

Regards,

[mosesdapoet]

Any picture available on this? Posting one would add to this.

[elteemike]

Lots of pix at site...

phys.org

[Boogieman]

“I can’t understand how an object — once having done this — can then (some time later) leave Earth orbit and go on about its merry way.”

Perturbation from the moon probably. You have to remember that there are more than just 2 objects in the orbital system of the earth and the object that gets captured.

[Boogieman]

“does he explain why there is gravity to begin with?”

No, Newton had no explanation for it, he just found the equations to describe it (at least to some degree of accuracy).

Einstein did try to explain it, though I’m not certain that his explanation is anything more than a bit of sleight-of-hand. He basically said that gravitational attraction is kind of an illusion, that everything is still moving in a straight line when viewed in reference to “spacetime”, but the curvature of “spacetime” caused by the presence of mass makes it appear to us, observing in 3-dimensional space, like there is an acceleration between the two masses. As for why mass should deform “spacetime” (really just time, since the space component can’t be deformed), I don’t think Einstein really gave a good explanation for that.

“We see light from distant galaxies which are billions of light-years away...so the light has been traveling for billions of years. Why doesn’t it get tired?”

Well, that question is simple at least. Newton’s 1st Law of Motion: any object in motion will tend to stay in motion unless acted on by an outside force. Again, Einstein’s answer would be a bit different.

[texas booster]

Adding in a few sentences that discuss the TCO and what the abbreviation means:

space objects that make their way close to Earth but do not immediately get pulled in by gravity are known as temporarily captured orbiters (TCOs), natural Earth satellites, or simply minimoons. Such objects circle the planet rather than plunge through the atmosphere and into the ground—at least for a time. It is believed most such objects do not circle the Earth for very long—they eventually succumb to gravity and crash through the atmosphere, or are instead flung back into space.

As the researchers also note, to date only one such object has ever been recorded circling the Earth—an object named 2006 RH120 was spotted back in 2006 circling the planet—it did so for approximately 11 months before it escaped the Earth's gravity and made its way back into space.