APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

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APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby APOD Robot » Mon Nov 13, 2017 5:08 am

Image Comet Machholz Approaches the Sun

Explanation: Why is Comet Maccholz so depleted of carbon-containing chemicals? Comet 96P/Machholz's original fame derives from its getting closer to the Sun than any other short period comet -- half as close as Mercury -- and doing so every five years. To better understand this unusual comet, NASA's Sun-monitoring SOHO spacecraft tracked the comet during its latest approach to the Sun in October. The featured image composite shows the tail-enhanced comet swooping past the Sun. The Sun's bright surface is hidden from view behind a dark occulter, although parts of the Sun's extended corona are visible. Neighboring stars dot the background. One hypothesis holds that these close solar approaches somehow cause Comet Machholz to shed its carbon, while another hypothesis posits that the comet formed with this composition far away -- possibly even in another star system.

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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby alter-ego » Mon Nov 13, 2017 7:12 am

APOD Robot wrote:...
Neighboring stars dot the background.

Along with Jupiter playing hide 'n seek behind the occulter.
A pessimist is nothing more than an experienced optimist

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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby Abbawabba53@gmail.com » Mon Nov 13, 2017 7:37 am

Does “half the distance of Mercury” mean the comet comes closer to the sun than Mercury or farther than Mercury?

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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby Boomer12k » Mon Nov 13, 2017 8:09 am

Abbawabba53@gmail.com wrote:Does “half the distance of Mercury” mean the comet comes closer to the sun than Mercury or farther than Mercury?


Closer....me thinkest....

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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby Boomer12k » Mon Nov 13, 2017 8:14 am

Maybe it formed in a less Carbon dense sector of the solar system's accretion disk, lo those many Yahren ago....but being "another visitor", is a possibility as we have seen...but the short period would seem to suggest otherwise...maybe it was just worn away with a lot of its dust?

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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby smitty » Mon Nov 13, 2017 1:38 pm

Suspect it should have been "twice as close as Mercury," i.e., half the distance as Mercury. Words do matter, especially in science!

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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby neufer » Mon Nov 13, 2017 2:05 pm

Click to play embedded YouTube video.
smitty wrote:
Boomer12k wrote:
Abbawabba53@gmail.com wrote:
Does “half the distance of Mercury” mean the comet comes closer to the sun than Mercury or farther than Mercury?

Closer....me thinkest....

Suspect it should have been "twice as close as Mercury," i.e., half the distance as Mercury. Words do matter, especially in science!
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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby rstevenson » Mon Nov 13, 2017 2:05 pm

smitty wrote:Suspect it should have been "twice as close as Mercury," i.e., half the distance as Mercury. Words do matter, especially in science!

Well, that would depend on which English you're speaking, Canajun, Merican, Aussy, or Brit. “Half as close as Mercury” seems clear to me, though “half the distance of Mercury” would have been better. "Twice as close" is confusing because it describes a quantity that is one-half as large using the word "twice".

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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby Alex571 » Mon Nov 13, 2017 2:25 pm

Halfway between the occulter and the left part of the image, is this another comet ?

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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby neufer » Mon Nov 13, 2017 3:16 pm

rstevenson wrote:
“Half as close as Mercury” seems clear to me, though “half the distance of Mercury” would have been better.

Actually, with a perihelion of just 0.12375 AU: “a third the distance of Mercury” would have been even better.
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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby Chris Peterson » Mon Nov 13, 2017 3:34 pm

Alex571 wrote:Halfway between the occulter and the left part of the image, is this another comet ?

There are several other things in the image that look a bit like comets. I suspect all of them are cosmic ray hits on the detector.
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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby Chris Peterson » Mon Nov 13, 2017 3:35 pm

rstevenson wrote:
smitty wrote:Suspect it should have been "twice as close as Mercury," i.e., half the distance as Mercury. Words do matter, especially in science!

Well, that would depend on which English you're speaking, Canajun, Merican, Aussy, or Brit. “Half as close as Mercury” seems clear to me, though “half the distance of Mercury” would have been better. "Twice as close" is confusing because it describes a quantity that is one-half as large using the word "twice".

In the context of the caption, I'd say none of them are confusing, regardless of how "standard" we want to consider the constructions.
Chris

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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby neufer » Mon Nov 13, 2017 3:38 pm

https://en.wikipedia.org/wiki/Arietids wrote:
<<The Arietids are a strong meteor shower that lasts from May 22 to July 2 each year, and peaks on June 7. The Arietids, along with the Zeta Perseids, are the most intense daylight meteor showers of the year. The source of the shower is unknown, but scientists suspect that they come from the asteroid 1566 Icarus, although the orbit also corresponds similarly to 96P/Machholz.

First discovered at Jodrell Bank Observatory in England during the summer of 1947, the showers are caused when the Earth passes through a dense portion of two interplanetary meteoroid streams, producing an average of 60 shooting stars each hour, that originate in the sky from the constellation Aries and the constellation Perseus. However, because both constellations are so close to the Sun when these showers reach their peak, the showers are difficult to view with the naked eye. Some of the early meteors are visible in the very early hours of the morning, usually an hour before dawn. The meteors strike Earth's atmosphere at speeds around 39 km/s.>>
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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby Case » Mon Nov 13, 2017 3:43 pm

Alex571 wrote:Halfway between the occulter and the left part of the image, is this another comet ?

I think not. If you view the ~264 frame click-through movie (75 MiB), the comet 96P and the stars move slowly, but you can see a lot of specks and streaks coming and going, and that one only appears at frame 114 (2017/10/27 09:06).

Chris Peterson wrote:There are several other things in the image that look a bit like comets. I suspect all of them are cosmic ray hits on the detector.

This LASCO page describes that the SOHO’s LASCO frequently captures interplanetary dust and sometimes even particles from the spacecraft itself. Unfortunately, their sample images are not/no longer accessible, so I can’t compare with today’s APOD.

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something very special!

Postby neufer » Mon Nov 13, 2017 6:29 pm

https://en.wikipedia.org/wiki/Large_Ang ... oronagraph wrote:
<<The Large Angle and Spectrometric Coronagraph (LASCO) is one of a number of instruments aboard the Solar and Heliospheric Observatory satellite (SOHO). LASCO consists of three solar coronagraphs with nested fields of view:

    C1 - a Fabry–Pérot interferometer coronagraph imaging from 1.1 to 3 solar radii
    C2 - a white light coronagraph imaging from 1.5 to 6 solar radii (orange)
    C3 - a white light coronagraph imaging from 3.7 to 30 solar radii (blue)
These coronagraphs monitor the solar corona by using an optical system to create, in effect, an artificial solar eclipse. The white light coronagraphs C2 and C3 produce images of the corona over much of the visible spectrum, while the C1 interferometer produces images of the corona in a number of very narrow visible wavelength bands.

The LASCO instruments are not the newest.
They were built in the late 1980s, when a digital camera was something very special.

Sometimes disturbances do happen. There are two kinds that repeatedly occur:

    Blackouts and Whiteouts, in broken lines, circle-like shapes, or over the whole picture. They are caused by the electronics box. There has never been a firmware update, since it was judged as too sensitive changing the flight-software.

    Black and white pixels, occurring in patterns, without pattern or alone. Those "missing blocks" are telemetry dropouts, caused by radio interference or a disturbance in the data transfer to Goddard Space Flight Center.>>
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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby MarkBour » Mon Nov 13, 2017 7:51 pm

Chris Peterson wrote:
rstevenson wrote:
smitty wrote:Suspect it should have been "twice as close as Mercury," i.e., half the distance as Mercury. Words do matter, especially in science!

Well, that would depend on which English you're speaking, Canajun, Merican, Aussy, or Brit. “Half as close as Mercury” seems clear to me, though “half the distance of Mercury” would have been better. "Twice as close" is confusing because it describes a quantity that is one-half as large using the word "twice".

In the context of the caption, I'd say none of them are confusing, regardless of how "standard" we want to consider the constructions.

“I don’t know half of you half as well as I should like; and I like less than half of you half as well as you deserve.”
Bilbo Baggins, The Fellowship of the Ring, A Long-expected Party

I'd say "half as close" is a phrase to be avoided. What is the "measure of closeness" that is being halved?
It's sort of like saying "half as cold", when all we have is a measure of hot, not cold.
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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby Chris Peterson » Tue Nov 14, 2017 12:00 am

MarkBour wrote:
Chris Peterson wrote:
rstevenson wrote:Well, that would depend on which English you're speaking, Canajun, Merican, Aussy, or Brit. “Half as close as Mercury” seems clear to me, though “half the distance of Mercury” would have been better. "Twice as close" is confusing because it describes a quantity that is one-half as large using the word "twice".

In the context of the caption, I'd say none of them are confusing, regardless of how "standard" we want to consider the constructions.

“I don’t know half of you half as well as I should like; and I like less than half of you half as well as you deserve.”
Bilbo Baggins, The Fellowship of the Ring, A Long-expected Party

I'd say "half as close" is a phrase to be avoided. What is the "measure of closeness" that is being halved?
It's sort of like saying "half as cold", when all we have is a measure of hot, not cold.

I'm not saying it's great usage. Just that in this context it's obvious what it means.
Chris

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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby neufer » Tue Nov 14, 2017 2:46 pm

Chris Peterson wrote:
MarkBour wrote:
I'd say "half as close" is a phrase to be avoided. What is the "measure of closeness" that is being halved?
It's sort of like saying "half as cold", when all we have is a measure of hot, not cold.

I'm not saying it's great usage. Just that in this context it's obvious what it means.

Here Comet Machholz is seen approaching the Sun much closer than Mercury ever does
(; or to be specific: "half as close").

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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby blucat » Wed Nov 15, 2017 10:42 am

What is that strong thin stream of , 'stuff', going_from/coming_to the Sun, in the upper right? Is the Sun 'alive' and communicating with the centre of the Galaxy? Or, what? Does anyone know? If this is a hole in the Sun's magnetic field and this is a super strong constant CME, that would be very big news? What is this? Cheers, oh and sorry for that last post, accidental, oops ..

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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby DeedsofEarth » Wed Nov 15, 2017 7:40 pm

To the question regarding the comet's distance from the sun, perhaps "Midway between Mercury and the sun, inside Mercury's orbit" would clarify the comet's distance.

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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby BobStein-VisiBone » Wed Nov 15, 2017 9:27 pm

neufer wrote:
Chris Peterson wrote:
MarkBour wrote:
I'd say "half as close" is a phrase to be avoided.

I'm not saying it's great usage. Just that in this context it's obvious what it means.

Here Comet Machholz is seen approaching the Sun much closer than Mercury ever does (; or to be specific: "half as close").

Got it. The comet got half as close to the sun as Mercury. Obviously Earth is two and a half times as close.

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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby MarkBour » Wed Nov 15, 2017 10:23 pm

BobStein-VisiBone wrote:
neufer wrote:
Chris Peterson wrote:I'm not saying it's great usage. Just that in this context it's obvious what it means.

Here Comet Machholz is seen approaching the Sun much closer than Mercury ever does (; or to be specific: "half as close").

Got it. The comet got half as close to the sun as Mercury. Obviously Earth is two and a half times as close.

:lol2:
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Re: APOD: Comet Machholz Approaches the Sun (2017 Nov 13)

Postby MarkBour » Wed Nov 15, 2017 11:27 pm

In the wonderful video that comes up when you click on the featured image, a very bright object moves left-to-right near the occulter (hence near the Sun). It is moving consistently with the stellar background. alter-ego identified that it is Jupiter. When I say these items are moving, I mean "perceptually, or in the video". I am guessing that this motion is primarily caused by the orbital motion of the SOHO probe. So, I assume the ecliptic is roughly horizontal in this image. Wikipedia confirms that 96P/Machholz has an orbit that is quite inclined to the ecliptic, though it may appear exaggerated here.
Mark Goldfain


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