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MattC1977 t1_jajewbx wrote

“Altered the orbit of the asteroid by 33 minutes “

Can someone ELI5 that for me? Does “33 minutes” translate to feet, yards, miles?

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zeeblecroid t1_jajjw9a wrote

It translates to minutes. Dimorphos completes an orbit in 33 fewer minutes than it did before it got smacked.

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rokoeh t1_jakp7yd wrote

So it's orbital speed and orbit changed by how much? In relation to it's parent body?

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TKtommmy t1_jal2boz wrote

Well if its orbit takes 1 year to complete then it equates to changing the orbital speed/period around the sun by 0.0057%

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Strykker2 t1_jalarad wrote

In this case Dimorphos orbits another asteriod, and has an orbital period of a few hours.

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aerowtf t1_jakmdvq wrote

it changes the shape of the orbit, making it slightly tighter or wider, which also corresponds to time

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TyrannoFan t1_jal81qr wrote

It represents the change in how long the asteroid will take to complete an orbit around the sun. It might not sound like much in the context of years-long orbits, but if this change in orbit can be enacted early enough and in the right direction, it can be the difference between the asteroid eventually striking Earth directly or missing it.

Think about a car driving down a road at 60mph. Let's say that 60 miles down the road, someone will walk across the road, let's call them Earth, and they won't be paying attention to traffic, idk maybe they're on their phone and have earphones in. In 1hr, the car will cross paths with Earth and run them over assuming it doesn't slow down. If you try and slow it down right as it's gonna hit Earth, you'll have to really slam on the breaks, and even then it might be too late. But if you intervene 1hr in advance and slow the car down ever so slightly such that the car arrives at where Earth crosses the road just a few seconds later, the crisis is averted with very little energy spent.

That's the exact same principle behind asteroid redirection efforts like this. Hope it helps.

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gobblox38 t1_jal0lpq wrote

These are arc minutes. There are 360° in a circle, 60 minutes in a degree, and 60 seconds in a minute.

On earth, an arc minute along a great circle is equal to a nautical mile. The conversion to any unit of length depends on the radius of the rotation. If the orbit is elliptical, the equation gets more complicated.

EDIT: I was totally incorrect about what they were talking about. See daughter post for details.

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TKtommmy t1_jal2jo6 wrote

No, we're talking the orbital period in time. Actual minutes of time.

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gobblox38 t1_jal5eri wrote

>Based on the change in the binary orbit period^2 , we find an instantaneous reduction in Dimorphos’s along-track orbital velocity component of 2.70 ± 0.10 mm s^–1

I should have read the article more closely. I thought they meant the angle changed when what really happened is the speed reduction increased the orbital period by 33 minutes.

After giving some consideration as to why they'd write it like that, it makes sense. Changing the orbital period by an amount of time may be enough for another orbiting body to get out of the way.

My bias got in the way of this one, thanks for the correction.

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