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Good article and very interesting content but stuff like: "The impact caused the asteroid’s orbit around another space rock to shrink — Dimorphos now completes
by wonderwonder 4y ago
Good article and very interesting content but stuff like:
"The impact caused the asteroid’s orbit around another space rock to shrink — Dimorphos now completes an orbit 33 minutes faster than before the impact"
drives me nuts. How long did the orbit originally take? Without this information it very much obscures the point.
Edit: I looked it up
"Before the impact, the orbital period was 11 hours, 55 minutes. It now is 11 hours, 22 minutes. NASA's previous estimate, announced in October, was an orbital change of 32 minutes. The benchmark for success had been set as a change of at least 1 minute, 13 seconds."
So it reduced it by about 1%. Pretty cool.
Edit2: as pointed out correctly by @statusgraph it's actually close to 5%. I fumbled the math on that.
https://www.voanews.com/a/asteroid-bashing-spacecraft-phenomenally-successful-studies-find/6985731.html#:~:text=%22The%20momentum%20of%20the%20collision,to%20Didymos%2C%22%20Thomas%20said.&text=Before%20the%20impact%2C%20the%20orbital,was%2011%20hours%2C%2055%20minutes https://www.voanews.com/a/asteroid-bashing-spacecraft-phenom....
- m4rtink 4y agoYeah, that is a quite substantial change! I was kind of expecting something much smaller - eq. measurable but not really significant.
- dylan604 4y agoin astronomical terms, measurable but not really significant, can become significant at cosmological times scales/distances. adjust the trajectory of something at the distance of Jupiter by a "measurable but not really significant" amount, and it could be the difference of a direct impact with earth or a near miss by the time that not really significant amount is accumulated for that distance.
- statusgraph 4y agoBy almost 5% actually! https://www.google.com/search?q=11hr+22min+%2F+11hr+55min&oq=11hr+22min+%2F+11hr+55min&aqs=chrome..69i57j33i10i160l3.6536j0j1&sourceid=chrome&ie=UTF-8 https://www.google.com/search?q=11hr+22min+%2F+11hr+55min&oq...
- wonderwonder 4y agoYou're right! Not sure how I did that.
- deleted 4y ago[deleted]
- chungy 4y agoIf you run Linux and have the `units` program installed, you can even do it without reaching for a web page: $ units '1-(11hr+22min)/(11hr+55min)' Definition: 0.046153846
- vultour 4y agoOr you can just convert it into minutes...
- willyt 4y agoJust tried this on macOS but it must be a different 'units' command as it won't accept that input. :-( However I just discovered that if you hit command spacebar and paste that into the spotlight search it gives the right answer! Spotlight has always done simple unit conversions but it didn't used to be able to do calculations with units in them. I wonder when that was introduced...
- dredmorbius 4y agoMacOS's default units(1) is the BSD version. GNU Units is far more featureful (and useful IMO). You can install that, as "gunits", using Homebrew.
- tstrimple 4y agoMost of the time I can get away with pretending MacOS is just sitting on top of Linux, but occasionally the BSD differences pop up and bite me.
- deleted 4y ago[deleted]
- rektide 4y agoWhat about the other way? How much did the impact craft weigh? How much delta-v did it have?
- Ensorceled 4y agoIt was about the size of a golf cart so I presume it's mass would be in an equally bizarre measurement, like "mass equivalent to 175 gallons of milk".
- pc86 4y agoSize of a golf cart and mass of a golf cart made of milk?
- wcoenen 4y agoAnother way to quantity the effect on Dimorphos is the speed change. It was about 2 centimeter/second. So if Dimorphos would be an object orbiting the sun by itself, then its location in its orbit would be shifted by about an Earth radius over 10 years. (In reality, Dimorphosis is paired with the 100x heavier Didimos, so their orbit around the sun was affected much less.)
- mannykannot 4y agoAfter the impact and velocity change, it would no longer follow its original orbit, but instead enter enter a new one, just as it did around Didymos.
- wcoenen 4y agoYes, the ellipse of the orbit would change a bit, while still passing through the point where the impact happened. Most of the change would be on the opposite side of the ellipse. However, I think that for such a small velocity change, it is a reasonable approximation to assume that the ellipsis around the sun stays pretty much the same, and only the phase of the object (i.e. where it is on the ellipsis at which time) is affected.