APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

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APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby APOD Robot » Fri Oct 17, 2014 4:05 am

Image Messier 6 and Comet Siding Spring

Explanation: This looks like a near miss but the greenish coma and tail of Comet Siding Spring (C/2013 A1) are really 2,000 light-years or so away from the stars of open cluster Messier 6. They do appear close together though, along the same line-of-sight in this gorgeous October 9th skyscape toward the constellation Scorpius. Still, on Sunday, October 19th this comet really will be involved in a near miss, passing within only 139,500 kilometers of planet Mars. That's about 10 times closer than any known comet flyby of planet Earth, and nearly one third the Earth-Moon distance. While an impact with the nucleus is not a threat the comet's dust, moving with a speed of about 56 kilometers per second relative to the Red Planet, and outskirts of its gaseous coma could interact with the thin Martian atmosphere. Of course, the comet's close encounter will be followed intently by spacecraft in Martian orbit and rovers on the surface.

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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby Ann » Fri Oct 17, 2014 4:19 am

This is a really lovely image, and I'm very glad to see it. The Butterfly Cluster truly sparkles. The deep red stars seen within it are distant red giants, but the bright yellow star in the cluster is indeed a member of it.

There is a lot of dust in the background. Note, however, that we can see more small background stars to the lower left than to the upper right of the cluster. There is less dust to the lower left.

The comet really adds to the beauty of the scene! And it is indeed going to be interesting to see if its "close shave" with Mars is going to have any noticeable effects on the Red Planet.

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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby Boomer12k » Fri Oct 17, 2014 5:07 am

Awesome!!!!

"...Like a Diamond...in the sky..."... :D

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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby Indigo_Sunrise » Fri Oct 17, 2014 10:41 am

Boomer12k wrote:"...Like a Diamond...in the sky..."

/snip

That's pretty much what I was thinking: another beautiful image of super-sparkly jewels!
Fabulous!

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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby MargaritaMc » Fri Oct 17, 2014 11:04 am

Planetary Society Video about Comet Siding Spring

The Comet Campaign has some excellent blogs.

M

PS. I've just discovered that the Comet Campaign were/are hosting a Reddit discussion on Siding Spring
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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby Psnarf » Fri Oct 17, 2014 3:52 pm

Will Siding Spring be visible from Earth without a telescope, or will it be a dot next to Mars?

Re: That Reddit discussion, methinks you might say that every star is the center of galaxy, since we really don't know where the boundary is. A star 14 billion light years away could be just as far from the boundary as Sol, making them both the center of the universe. My brain hurts.

othermoons

Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby othermoons » Fri Oct 17, 2014 4:24 pm

Would a superhuman being for example traveling in space be able to see such a magnificent site with unaided eyes?

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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby Chris Peterson » Fri Oct 17, 2014 4:33 pm

othermoons wrote:Would a superhuman being for example traveling in space be able to see such a magnificent site with unaided eyes?

Define "superhuman".

An ordinary human in space would see nothing like this. Only a few stars, little color, and much lower resolution.
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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby Bob » Fri Oct 17, 2014 4:49 pm

"10 times closer"? When I multiply anything by 10 I get a larger number. How about "one tenth of the distance"?

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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby Chris Peterson » Fri Oct 17, 2014 4:56 pm

Bob wrote:"10 times closer"? When I multiply anything by 10 I get a larger number. How about "one tenth of the distance"?

"Ten times closer" is a perfectly common and acceptable language form, and there's nothing confusing about it.
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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby visual_astronomer » Fri Oct 17, 2014 5:11 pm

I don't intend to launch a grammer thread, but I agree with Bob.

Just becuase some people say "I could care less" when they really mean "I couldn't care less" doesn't make it correct.

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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby Chris Peterson » Fri Oct 17, 2014 5:13 pm

visual_astronomer wrote:I don't intend to launch a grammer thread, but I agree with Bob.
Just becuase some people say "I could care less" when they really mean "I couldn't care less" doesn't make it correct.

Agreed. But there's nothing wrong with the expression Bob was objecting to. (I like "one tenth the distance" better, but in fact, both are correct usage.)
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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby rstevenson » Fri Oct 17, 2014 6:46 pm

When you say "one tenth the distance" you're defining what it is you're taking one tenth of, the overall distance. But when you say "10 times closer" what are you multiplying by 10?

Saying "10 times closer" is like saying "twice as cold", a meaningless phrase I hear once in a while in weather reports.

Rob

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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby Chris Peterson » Fri Oct 17, 2014 6:56 pm

rstevenson wrote:When you say "one tenth the distance" you're defining what it is you're taking one tenth of, the overall distance. But when you say "10 times closer" what are you multiplying by 10?

Saying "10 times closer" is like saying "twice as cold", a meaningless phrase I hear once in a while in weather reports.

I would say that "ten times closer" is completely synonymous with "one tenth the distance". And here's a good test. Are you confused by "ten times closer" in the way you are with "twice as cold"? Does "ten times closer" result in an ambiguous interpretation? I'd say "no" to both, which is why it's reasonable usage, even if you make the argument that, strictly parsed, it's a bit idiomatic.
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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby geckzilla » Fri Oct 17, 2014 7:00 pm

Well, you're multiplying units of closeness. If x is a unit of closeness then another object is 10x less close. This reminds me of writing a script in inverted logic.
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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby Chris Peterson » Fri Oct 17, 2014 7:08 pm

geckzilla wrote:Well, you're multiplying units of closeness. If x is a unit of closeness then another object is 10x less close. This reminds me of writing a script in inverted logic.

"Times closer" means divide in the same way the "times farther" means multiply. The mistake is in thinking that "times" in this context has to mean multiplication. "Ten times closer" is just the complement of "ten times farther", and both are unambiguous.
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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby rstevenson » Fri Oct 17, 2014 7:15 pm

I'm usually the first to agree that language is maleable, but...
"Times closer" means divide in the same way the "times farther" means multiply ?
No. "Times" means multiply. Modifying it with "closer" adds confusion, not sense. But I'm willing to agree that this might be a regional interpretation. English is written, spelled, spoken, pronounced, and interpreted somewhat differently in different parts of the world, even in different parts of the same country.

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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby BMAONE23 » Fri Oct 17, 2014 7:23 pm

1 object is being viewed by 2 vantage points
Vantage pt A and Vantage pt B
Vantage pt A is 9 miles away and Vantage pt B is 90 miles away
Vantage pt B is 10 times farther away than Vantage pt A
or the reciprocal
Vantage pt A is 10 times closer than Vantage pt B

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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby geckzilla » Fri Oct 17, 2014 7:30 pm

Chris Peterson wrote:
geckzilla wrote:Well, you're multiplying units of closeness. If x is a unit of closeness then another object is 10x less close. This reminds me of writing a script in inverted logic.

"Times closer" means divide in the same way the "times farther" means multiply. The mistake is in thinking that "times" in this context has to mean multiplication. "Ten times closer" is just the complement of "ten times farther", and both are unambiguous.

Maybe I do all my division by multiplication!
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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby Chris Peterson » Fri Oct 17, 2014 7:39 pm

geckzilla wrote:
Chris Peterson wrote:
geckzilla wrote:Well, you're multiplying units of closeness. If x is a unit of closeness then another object is 10x less close. This reminds me of writing a script in inverted logic.

"Times closer" means divide in the same way the "times farther" means multiply. The mistake is in thinking that "times" in this context has to mean multiplication. "Ten times closer" is just the complement of "ten times farther", and both are unambiguous.

Maybe I do all my division by multiplication!

I generally do.
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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby Chris Peterson » Fri Oct 17, 2014 7:41 pm

rstevenson wrote:I'm usually the first to agree that language is maleable, but...
"Times closer" means divide in the same way the "times farther" means multiply ?
No. "Times" means multiply. Modifying it with "closer" adds confusion, not sense. But I'm willing to agree that this might be a regional interpretation. English is written, spelled, spoken, pronounced, and interpreted somewhat differently in different parts of the world, even in different parts of the same country.

But you didn't answer my question. Is there any way that "ten times closer" can be reasonably misunderstood? If not, I'd argue there's no issue.
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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby FloridaMike » Fri Oct 17, 2014 8:15 pm

Maybe each APOD should have a grammar discussion thread and a science discussion thread. :)
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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby MargaritaMc » Fri Oct 17, 2014 8:21 pm

FloridaMike wrote:Maybe each APOD should have a grammar discussion thread and a science discussion thread. :)

:yes: :thumb_up:
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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby Ron-Astro Pharmacist » Fri Oct 17, 2014 9:13 pm

Chris Peterson wrote:
rstevenson wrote:I'm usually the first to agree that language is maleable, but...
"Times closer" means divide in the same way the "times farther" means multiply ?
No. "Times" means multiply. Modifying it with "closer" adds confusion, not sense. But I'm willing to agree that this might be a regional interpretation. English is written, spelled, spoken, pronounced, and interpreted somewhat differently in different parts of the world, even in different parts of the same country.

But you didn't answer my question. Is there any way that "ten times closer" can be reasonably misunderstood? If not, I'd argue there's no issue.


I'll butt in. A moving object is little hard to define at a point in time. If Siding Spring is 100,000 Km from Mars is it 10 x closer at 10,000 Km? Then 10 x closer at 1,000 Km? You'd have a hard time accurately describing it at a moment using the "closer" language leading to misunderstanding. I'd hate to hear a NASA official saying, "It's 10 x closer now than it was at noon. Well, at least it was 5 seconds ago." I would hope to hear a different description of its location.

Comparing two separate objects to another at a defined time and place is a different story .
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Re: APOD: Messier 6 and Comet Siding Spring (2014 Oct 17)

Postby Nitpicker » Fri Oct 17, 2014 9:14 pm

Chris Peterson wrote:
Bob wrote:"10 times closer"? When I multiply anything by 10 I get a larger number. How about "one tenth of the distance"?

"Ten times closer" is a perfectly common and acceptable language form, and there's nothing confusing about it.


I agree with Chris, and it is not just about language. Closeness is inversely proportional to distance. As closeness increases, distance decreases and vice versa. It is just that we don't commonly use units for closeness expressed in dimensions of [Length]-1.


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