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Breaking news: a x400,000 brightening of 17P/Holmes! October 25, 2007

Posted by dorigo in astronomy, news.

Comet 17P/Holmes has experienced a huge outburst, brightening yesterday in the matter of hours from magnitude 16.8 to magnitude 3 and below. That is a jump of brightness of 400,000 times!!

The transformation has been spotted at 13:40UT on October 24th by Seiichi Yoshida in Yokohama, Japan. And the comet has continued to brighten since!  

The comet is easy to find with naked eye in the evening sky for northern observers close to Mirfak, also known as \alpha Persei. Look for an extra star in Perseus, you will not miss it even under polluted skies. With large instruments it should look a bit like a dense globular cluster. The thing is far away, but bright! Don’t forget to comment here if you see it… The sky on northern Italy is expected to be bad tonight and tomorrow, darn it.

Read reports and see pictures by amateurs in this thread.


1. Amara - October 25, 2007

Sky is awful in southern Italy too. Any idea how a comet could brighten 400,000 times in timespan of hours?

2. dorigo - October 25, 2007

Hi Amara,

yes, I have an idea… The comet is actually an alien spaceship, and its nuclear reactor just blew the whole thing off.

Easy explanation, no ? It just involves a unobserved alien race wandering around inside chunks of ice in our solar system. Reminds me of some recent theories beyond the standard model of particle physics…


Addendum: in the list of needed hypothesis there also is the presence on board of some idiot who disabled the alarms as the core was going into chinese syndrome.

3. dorigo - October 25, 2007

Another one: the comet just crossed the path of a cosmic string and was torn to smithereens.


4. Amara - October 25, 2007

Tommaso: CMEs can rip off the ion tail of a comet, but I wonder if such a shock can also disrupt a comet nucleus …?

5. Amara - October 25, 2007

P.S. I would think that alien race would be doing something more useful than wandering around inside chunks of ice.
If I were them, I would be working on building a tethered TNO networked city, sitting in methane hot tubs, drinking a frozen pina colada and watching the colorful meteor shower shows that I made.

6. Kea - October 25, 2007

According to NASA, it isn’t that close to its perihelion, so I’m guessing the ‘melting ice’ theory that I heard is wrong.

7. A comet visible to the naked eye! « Flintstone Stargazing - October 25, 2007

[…] comet visible to the naked eye! October 25th, 2007 — Ed I learned first at this post about a comet that has suddenly brightened to magnitude 2.8! That means it should be easily […]

8. Tony Smith - October 25, 2007

Acccording to a 24 October 2007 space.com web article by Joe Rao:
“… Why Comet Holmes has undergone such an explosive outburst is not understood.
What is amazing is that it made its closest approach to the sun last May, but came no closer than 191 million miles (307 million kilometers) to the sun. The comet is now moving away from the sun and currently is quite far out from Earth at a distance of 151 million miles (243 million kilometers). …
This comet is part of Jupiter’s “family” of comets – a group in which the far end of their respective orbits (aphelia) cluster around the orbit of Jupiter and takes 6.88 years to make one circuit around the Sun. …
this is probably not the first outburst for Comet Holmes: when it was discovered in 1892, it was likely in outburst mode, since it became as bright as fourth magnitude and was dimly visible to the naked eye …
what this object will do in the coming days and weeks is not known …”.

Zdenek Sekanina, in Proceedings of the International Astronomical Union (2006), 2: 211-220, said about comet 73P/Schwassmann/Wachmann in its 2006 appearance:
“… From the behavior of the primary fragment C, 73P is not a dying comet, even though fragment B and others were episodically breaking up into many pieces.
Each episode began with the sudden appearance of a starlike nucleus condensation and a rapidly expanding outburst,
followed by a development of jets,
and a gradual tailward extension of the fading condensation,
until the discrete masses embedded in it could be resolved …”.

Could this Comet 17P/Holmes episode be “… the sudden appearance of a starlike nucleus condensation and a rapidly expanding outburst …” ?

Will it be “… followed by development of jets …”
“… a gradual tailward extension of the fading condensation …” ?

Tony Smith

9. Kea - October 25, 2007

Starlike nucleus condensation in a comet? Louise?

10. changcho - October 25, 2007

Most interesting! I observed it last night with my wife and kids and it looked like an anomalous ‘star’ in the constellation of Perseus; that’s the weird thing, with the naked eye it looked like a star.

Pointed binoculars to it and we could tell there was something weird in its appearance, since it looked extended. So, pointed the 150 mm Maksutov to it and it looked wonderful: bright starlike nucleus, with a large, extended coma.

Thanks to J. Rao (via T. Smith) for the extra dynamical information (i.e., the fact that it’s a Jupiter Family Comet; its period; the fact that it’s moving AWAY , etc.). Very interesting.

2007 is turing out to be an iteresting year for comets: McNaught in the begining of the year and Holems at the end of the year!

11. marlon - October 26, 2007

i am sure this is nibiru. dont ask nasa about it, they will never tell the truth.

12. Kea - October 26, 2007

But its orbit is only 7 years, so it can’t be Nibiru. Oh, unless its orbit is about to change dramatically… goody! I can’t wait to meet some aliens.

13. dorigo - October 26, 2007

Hi Tony,

thank you for the quotes. Indeed, that comet is an interesting object to study!

I heard a report from a fellow visual amateur, Michele Scaffidi, who observed it yesterday with a 16″ scope. He described a bright yellow nucleus and a fainter roundish reddish outer halo. Must be very nice to look, unfortunately my dob is in the mountains and there’s no way I am going to travel there with a full moon, and thus only the comet in my observing agenda. Sure, a comet is nice, but… Gas prices are high!

Nibiru ??? What the hell ? 🙂

Kea, I am sure aliens can’t wait either. Imagine the conversations on category theory. You’d probably be the only one who could converse with them, using your graphs.


14. dorigo - October 26, 2007

With respect to your quotes about 73/P, Tony: I think the phenomenology was that of an object ripped apart by gravitational interaction with a massive body. I am not aware of anything that could cause the same effect on 17/P… That is why I was speculating a cosmic string, or some other multidimensional object crossing our 3-D “plane” near the comet… Just for fun of course!


15. Amara - October 26, 2007

Related behavior to the centaur Echeclus ??

16. Amara - October 26, 2007

forgot the first quote: link should be here.

17. dorigo - October 26, 2007

Interesting… One can’t help asking how probable it is such a collision.

18. Amara - October 26, 2007

A collision, or perhaps explosive sublimation of a very volatile gas: CO?

19. Tony Smith - October 27, 2007

Tommaso asks “… how probable it is such a collision …” to cause the outburst of 17P/Holmes.

According to a web page of Gary Kronk’s Cometography:
“… 17P/Holmes … was discovered [ in 1892 ] during an apparent outburst in brightness …[and]… experienced another outburst in brightness around January 16 [1893] … a telescope revealed a nucleus of magnitude 8 and a coma 41 arc seconds across … The comet steadily faded after the mid-January outburst …”.

Since in the 115 years ( roughly 115 / 7 = 16. … orbits of 17P/Holmes ) from 1892 to 2007 the comet has had no outburst,
maybe it might be reasonable to guess that it hits something
every 16 orbits,
from that (and a guess at its physical cross-section) maybe a density of asteroids could be calculated
that might be compared with what is known about the density of asteroids distributed between Jupiter’s orbit ( around 5 AU ) and the comet’s perihelion distance (about 2 AU, acccording to Kronk, which is outside the orbit of Mars ( around 1.5 AU) so the orbit of 17P/Homes might be considered to be within the Asteroid Belt ).

Tony Smith

20. Amara - October 27, 2007

You know about the Main Belt comets, right?

21. Tony Smith - October 27, 2007

Amara asked about “… the Main Belt comets …”.

According to an IFA Hawaii web page of Henry Hsieh
“… main-belt comets … the MBCs present a distinct contrast with other periodic comets (the Jupiter-family and Halley-family comets, or JFCs and HFCs) which originate in the cold outer solar system in the Kuiper Belt or Oort Cloud … Unlike the JFCs and HFCs, the MBCs appear to have formed in the much warmer inner solar system … MBC orbits are comparatively much more circular (making solar heating effectively constant) … for the activation of MBCs … We hypothesize … excavating impacts from other asteroids that “dig up” buried (and thus preserved) ice, exposing it to the heat of the Sun …”.

According to a Joe Rao article on space.com,
“… Comet Holmes … is part of Jupiter’s “family” of comets – a group in which the far end of their respective orbits (aphelia) cluster around the orbit of Jupiter …”,
according to a CIW web page of Scott Sheppard
“… Jupiter Family comets … are believed to originate from the Kuiper Belt … Their orbits are controlled by Jupiter …”.

Even though the orbit of 17P/Holmes may not be circular enough for it to be a true Main Belt Comet,
since its perihelion is pretty far out (around 2 AU) it may be that it Hsieh’s hypothesis for “activation” …
“… excavating impacts from other asteroids that “dig up” buried (and thus preserved) ice, exposing it to the heat of the Sun …”
might indeed apply to the outburst of 17P/Holmes.

Tony Smith

22. Dan - October 29, 2007

I’m no astronomer, and don’t even play one on TV, but I work around them (including Henry Hsieh sometimes) and I’m trying to think of anything other than explosive outgassing or a collision that would cause this.

Fortunately for uneducated ol’ me, the astronomers are curious too, so lots of people are taking lots of pictures and lots of spectra (in fact, I’m watching one of Henry’s fellow grad students take some data on it as I type this) and I look forward to them explaining it! 🙂

23. Peter Nelson - November 8, 2007

I managed to get a shot of it from my deck in Chelmsford Massachusetts, USA (about 35mi NW of Boston) before the clouds rolled in last night. I put it on my blog along with a shocking new theory (you might not get it if you didn’t grow up watching American TV)

24. marlon - November 10, 2007

from this year, 2007 to 2012, celestial phenomena will be regular events in the sky. To the mayans, these are not strange happenings but are associated with the solar system entering the galactic core of milky way galaxy.

25. zooped.org » Blog Archive » Comet 17/P Holmes - November 10, 2007

[…] on October 30, 2007 at Costa Mesa, California – via Wikipedia.Now, the net has been full of reports about comet Holmes these last days. However, I hadn’t really taken note of it – but tonight, the […]

26. dorigo - November 11, 2007

Nice picture Peter. Your theory is … well… interesting 🙂

Marlon, what do you mean ? The solar system is not going anywhere!


27. U - January 14, 2008

“associated with the solar system entering the galactic core of the milky way galaxy”??? What are you talking about? The solar system isn’t entering the galactic core of the milky way! We are 10’s of thousands of light years out in one of the spiral arms – in the galactic boondocks of the milky way, in fact. People, please get some real science/astronomy books and take the time and spend the effort to read them.


28. Inbound - April 28, 2008

I just got a new telescope. I can’t wait to try it out.

29. dorigo - April 28, 2008

Hello Inbound,

have fun! And remember, even a small instrument can give endless satisfaction. Just keep digging on new things to aim it at. There are constantly new supernova explosions, moon transits over Jupiter, new comets, new celestial events of all kinds.

Another advice: keep a log file of your observations. As you watch an object, describe it to yourself (even speaking aloud if that doesn’t bother you), trying to capture all possible details. Observe from a dark site, cover yourself with plenty of clothing, and find a comfortable position. These are very important ingredients for a successful viewing!


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