Holmes Comet Coma Grows Bigger Than The Sun

coondoggie passed us a NetworkWorld article, as he does, noting that there is now an object in our solar system bigger than Sol. The Holmes comet has a huge coma, with a diameter scientists are now calculating to be larger than our own middle-sized star. "Scientists don't seem to have a guess as to how big it will ultimately become. The Holmes coma's diameter on Nov. 9 was 869,900 miles (1.4 million kilometers), based on measurements by Rachel Stevenson, Jan Kleyna and Pedro Lacerda of the University of Hawaii Institute for Astronomy. The sun's diameter, stated differently by various sources, is about 864,900 miles (1.392 million kilometers)."

Comments

Name

[Anonymous Coward]

Look, don't try to sound cool by calling the sun "Sol". It just sounds pompous.

Re:Name

[Anonymous Coward]

So if it's bigger that Sol, does it look as big as Luna from Terra?

Re:Name

[drfireman]

I inhabit a planet circling a nearby "sun." Actually, we call our "sun" Sol, and we find it a little insulting that your SF writers have assumed the name was unclaimed. Stop it. We don't call our "moon" Luna, so you're safe there, but I have to say, on behalf of my people, that it sounds stupid, and "moon" wasn't taken anyway (we call our little satellite thing "Kodak"). There's lots of other stuff you guys have wrong, too, but here on our planet we're not really supposed to be reading Slashdot during work hours. Maybe I'll post from home later.

Re:Name

[fm6]

Hey, get your pop culture references straight. The aliens on Star Trek don't speak English, their voices are automatically translated by the "universal translator" which also has the ability to warp the light around their faces so their lips stay in sync with the English version of what they're saying.

Re:Name

[h4rm0ny]

A sun is a type of thing, Sol is the name of the sun that happens to be closes to us.

Oh no! No. This is as bad as all those people who have started pronouncing Uranus "your-an-us" rather than "your-a-nus" because they think it sounds more scientific that way. As if sounding "scientific" is a good thing as opposed to trying to make things as understandable as possible (and funny). A sun is not a type of thing. You can say it to mean that, put it with a lower case 's' and people will know what you mean, but we have a word that specifically means that with no ambiguity and the word is star. We have been calling the Sun "the Sun" for a long, long time. Other languages have their own words for the Sun and they are direct equivalents. They don't mean "stars" or even "stars with planets around them." Each word means, quite specifically The Sun. And the interesting thing is that one of those languages is Latin and its word for the Sun is "Sol." It is the direct equivalent word with the same meaning. Why you think translating something into another language is suddenly correct and using the native word incorrect I don't know. But I am suspicious that it is that same creeping desire on the part of some people to sound "scientific." The English speaking world has used the Sun for centuries quite happily without any ambiguity which has appeared out of nowhere in recent years.

The overwhelming majority of English speakers call it the Sun and don't mean stars and wouldn't think to mean stars. Almost nobody calls it Sol. Why introduce confusion?

The Sun. The Stars. Uranus [rude pronunciation].

Thank you.

In other news...

[explosivejared]

Sol now jealous of the precocious, scampy little comet's meteoric rise in popularity and size has become addicted to painkillers and alcohol. Friends close to the star hope to be able to talk the down-and-out celestial body into going to rehab.

Re:In other news...

[john83]

Nah, it'll just resort to using a cane and become bitter and hilariously sarcastic.

Re:In other news...

[o'reor]

Sol now jealous of the precocious, scampy little comet's meteoric rise in popularity and size

... and you forgot to mention the "Enl4rg3 y0ur coma" spam mail that Sol has now started to receive...

Diameter? A bit hard to define.

[gardyloo]

Yes, this is pedantic, but by practically any definition (even leaving aside unbounded electromagnetic radiation or mass), Sol is FAR larger than the comet. The very fact that the comet HAS a tail of sorts speaks to the influence of the solar wind.

      I'd guess that the diameter that most people talk about when they're discussing the sun is that determined by the mean-free scatting path length of photons produced within the sun. Once the photons' probability for escaping the sun is higher than that for being scattered back into the interior, that's what we usually call the "diameter", and it accounts for the relatively sharp "edge" to the sun.

      I could release a bunch of helium atoms on Earth's surface, and eventually they'd diffuse enough to be effectively larger than the sun's "diameter" as defined in the articles. It still doesn't mean a whole lot.

Re:Diameter? A bit hard to define.

[Anonymous Coward]

But the term "large", when used without specifying which measurement is being referred to, usually refers to length. Thus, for solar objects, diameter. By that measurement, Holmes is technically larger than the sun.

This depends - as the parent post already pointed out - entirely on how you define the diameter of the object in question. And - again, as the parent post already pointed out - the diameter of the sun is usually defined by that part of the sun which emits most of the photons that reach us from the sun. By most other definitions - and there are lots of them that do make sense - the diameter of the sun is larger. Much larger, in fact.

Incidentally, if you define the diameter of the sun using a measure that more-or-less matches the one used for defining the diameter of a comet's coma - namely, the diameter of the gas cloud emitted by the object in question - you'll get the entire heliosphere. Which is way larger than the coma of 17P/Holmes.

Re:Diameter? A bit hard to define.

[osu-neko]

Not really, no. Using the same standards for measurement, the diameter of the sun is over 800,000 miles, whereas the diameter of the comet is only a few miles. OTOH, if you want to include the coma, then the diameter of Holmes is over 800,000 miles, but the diameter of the sun is over ten billion miles (assuming you measure the short distance across the coma/heliopause and not down the length of their respective tails).

oblig

[Joe the Lesser]

Man: Every once and a while we dump a big piece of ice in the ocean, solving our problems once and for all.
Girl: But...
Man: ONCE AND FOR ALL!

"Bigger than..."

[RealGrouchy]

So we'll have to revise the list, then?

1. Beatles
2. Jesus
3. Holmes Comet
4. Sun

- RG>

Correct != pompous

[Anonymous Coward]

Our sun's name is "Sol." It is correct to call it by its proper name.

I don't think it makes the speaker sound pompous at all. Appealing to one's own ethos to strengthen an argument makes someone sound pompous. Quoting the law to justify an opinion about morality makes someone sound pompous. Using the word "Virii" to mean "more than one computer virus" makes a speaker sound pompous, and is also incorrect.

But simply speaking in a technically precise manner, especially to a science-literate target audience on a techie/geeky website, is not in the least bit pompous.

I would go so far as to call it "expected."

Re:Definition trouble.

[Mundocani]

I know you guys are right and all, but this is more of a fun factoid than some sort of scientific claim. Yeah, the sun is bigger, and has magnetic fields and winds and has tons more mass and everything, but as an amateur astronomer (very amateur), I still find it fascinating just how large the thing has become since exploding only a few weeks ago. That it's larger than the "visible" sun is, to me, just wild -- even if it is nothing but a huge bubble with very little substance.

John Holmes Comet Grows Bigger

[Fear the Clam]

The Holmes comet has a huge coma

And it's headed straight for your black hole, bay-bee.

Re:Spur of the moment thought

[edremy]

Umm, how? It's a bit tough to snare things moving at kilometers/second relative to your velocity, even assuming that there is something strong enough to grab on to in a comet. If it's not moving at kps relative, then you don't gain anything anyway- you've expended the energy to fly in formation with it.

You want free energy for spaceflight? There are better ways

Re:Spur of the moment thought

[inviolet]

Why not make a satellite hitch ride on one of these comets to the outer reaches of the solar system. Assuming they go there once every round, even hitching Halley's comet will get us further than Pioneer 1&2 have been in a shorter time, without wasting any precious fuel.

To hitch a ride on a passing comet, you can do one of two things:

1. Match velocities, and then land on it. -or-

2. Not match velocities, and then get smashed to bits by it.

Method 2 easily achieves your goal of travelling to the outer reaches of the solar system "without wasting any precious fuel". However, your satellite will no longer be functional, or even identifiable. But other than that, yeah, it's a great idea. :)

(Tell me Mrs. Lincoln, other than that, how did you enjoy the theatre?)

Got a photo of it last night

[yeremein]

I took a picture of the comet just yesterday. Posted here.

In fact, I have several photos of the comet taken over the past few weeks. They're not all cropped the same, but it's still quite apparent how much the comet is expanding. One of these days I plan to put together a composite photo, fixing the stars in place, and showing not only the expansion of the comet but also its motion relative to the stars.

Comet P/17 Holmes visibility, naked eye aspect

[fyngyrz]

So if it's bigger that Sol, does it look as big as Luna from Terra?

It looks exactly like this.

That's a shot with a 50mm portrait lens - no telescope, no magnification, nothing. The comet is plainly visible as an orb, yes, just as the sun is.

Re:Comet P/17 Holmes visibility, naked eye aspect

[fyngyrz]

I'm quite serious. Read the text I supplied with the image. The "orbs" you refer to are not resolved images of the edges of stars, they are simply burned out areas on the camera's sensor as the atmosphere's lensing moves the stars around over the many seconds of the exposure. Those stars are points of light, no more.

The burnout on many star occurs because stars, in relation to one another, can be literally millions of times different in brightness. Comet Holmes, while large, is not nearly as bright as many of those stars at any one sensor location, hence is does not burn out the imager and you get a considerably more accurate representation of it. Likewise, the dimmest stars still appear as pinpoints because when they are lensed to a random location, one or two passes over a sensor site aren't enough to result in a bright reading - that only happens at the centroid of the focus, essentially right where the star actually is.

Re:Comet P/17 Holmes visibility, naked eye aspect

[fyngyrz]

Also, re your remark about post processing, I did three and only three things:

1) I used levels to push very faint background stars and sensor noise (which is fairly significant at ISO 3200) down towards or into black;

2) I pushed the color saturation up by about double to bring out the colors of the stars.

3) I clipped the portion of the image containing the comet and a few stars out and posted that fragment only, as opposed to the entire 10 megapixel shot.

None of which affected the capture of the comet in any significant manner. It isn't reflecting any particular color, so the change in saturation had no effect. The comet is quite bright, so pushing down the bottom-most brightness levels only served to trim a few pixels at the darkest edges of the comet. It appears just a trifle larger in the original.

Read the FAQ

[benhocking]

Slashdot seems to be very Earth-centric. Do you have any plans to be more galactic in your scope?

Slashdot is Earth-centric. We readily admit this, and really don't see it as a problem. Slashdot is run by Earthlings, after all, and the vast majority of our readership is from the Earth. We're certainly not opposed to doing more galactic stories, but we don't have any formal plans for making that happen. All we can really tell you is that if you're outside the solar system and you have news, submit it, and if it looks interesting, we'll post it.

Damn you

[benhocking]

The big fiery ball in the sky is called Sun by [pulling number out of ass] 99.9% of all English speaking humans.

I'll never be able to use that number again. From now on I'll have to say 0.1% less than 100% or something like that...

Really, what possessed you to store it up there in the first place?!?