The strange comet 17P/ Holmes

Observations from the 26th of October 2007 to the 9th of January  2008

South Germany, Bavaria


in deutsch

On the 24th of October world-wide the astronomers were confronted with a new phenomenon in the sky. The inconspicuous 16.3mag* bright comet P17/Holmes, discovered 1892 by Edwin Holmes was by the time only photographically provable by larger telescopes. On this day the comet increased in its brightness within hours up to 2,5 mag. Suddenly in the constellation Perseus a third bright "star" had emerged, which can be discovered despite of the prevailing full moon situation with the naked eyes easily. That means, the brightness increased by a factor of nearly 500000, while around the comet nucleus a circular expansion wave made itself recognizable


Left map for the 27th October 18:30 UTC/ 20:30 MESZ, latitude 48.1°, longitude 11.4°, (South Germany). Right map: Change of position till 18th November, 18:30 UTC / 19:30 MEZ

What had happened, that this cosmic ice ball in a distance of  2,4 AU (approx. 360 millions km) to the sun, suddenly begins itself to expand in a perfectly shaped radius? Was it a cosmic collision, a chemical reaction, or the wall "burst" around a large cavity within the comet body? May after coming nearer to the planet Mars (map) the green manikin did attack? So far there is no clear explanation for it !

For more basic info's about the comet scroll down.

Update: 5th March and 6-9. January 2008

1 mr 2 tb  3 tb

1) Comet 17P/ Holmes near the California Nebula, 5.3.08, 2) 17P/ Holmes near the star Algol, 9.1.08, Nikon 300mm, f4, Exp 110 sec, ASA 800 Canon 20D, Auerberg   3) 17P/ Holmes near the star  Algol, 6.01.08, Nikon 300mm, Exp. 120 sec, ASA 800 Canon 20D, Germerswang

Photo 1) Comet 17P/ Holmes near the California Nebula on the 3/5/2008. The very difuse nebula measures now apprx. more than 4,5 times of the moon diameter. This is equivalent to 2,25 degrees or 135arcmin.

Photo 2) and 3) 1/9/2008: Apprx. 84 arcmin lenght x 71 arcmin breadth is now the expansion of 17P/ Holmes by a distance of 2,1 AU (315 Mio. Km) from the earth. Despite the enormous widness of nearly 7,7 x 6,5 million kilometers the comet can be observed in dark areas surprisingly effordless with the naked eye. But near big towns, the object is really hard to observe. (estimated brightness 4,2 mag*).

Update: 5th of December 2007


Left: Nikon 300mm, f4 ( 480 mm dig), Exp 90 sec, ASA 800 Canon 20D

With nearly 56 arcmin, 17P/ Holmes is nearly 2 times bigger as the moon (may 3,7 mag*). It can be still observed in dark areas with naked eye.

Update: 28th of November 2007


 Nikon 300mm, f4 ( 480 mm dig), Exp 90 sec, ASA 800 Canon 20D


 Canon 10 mm (16 mm dig), Exp 90 sec, ASA 800 Canon 20D, Auerberg, South Germany

Due to the comet measures visual 45 arcmin, the diameter must reach up to 3,7 million kilometers. 17P/Holmes is fading surprising less (may 3,5 mag*). No problem to see the diffuse ball in dark areas with naked eye. The comets surrounding material in comparision to the 1,5 x moon diameter  makes it easy to discover, although the momenty brightness is declining. Watch vertical at midnight!

17th of November 2007


 Nikon 300mm x 2 times converted, f4 ( 960 mm dig), Exp.2x120 sec, ASA 800 Canon 20D

The expansion of 17P/ Holmes measures now 35 arcmin, and is visual archiving more the the moon (30,5'). Since the 5th of November the comet is the biggest object in our solar system. The diameter reaches up to 2,5 million kilometers. 17P/Holmes is dimming (may 3,2 mag*), but it is no problem to see the the expansiom wave with the naked eye. By using normal binoculars it is together with the "Perseus star" Mirfak a real magic view .

9th of November 2007


Photo left, Nikon 300 mm, f4 ( 480 mm,1.6 x dig), Exp.. 3 x 120 sec, ASA 800. Canon 20D. Photo right; Orion Optics 80/600 ED Exp.90 sec, ASA 800 Canon 20D

 (9.Nov,0:10 UTC), Jaufenpass (1700 müNN), Sterzing. Thank's to Martin for the borrowing of the 600ED!

Today the expansion of 17P/ Holmes is around 21,5 arcmin, and visual archiving more than 2/3rd of the moon (30,5'). It seems that the comet loose it's tail. A may low solar wind isn't able to blow out the dust from the center.

5th of November 2007


Today the expansion of 17P/ Holmes is around 17 arcmin, and visual archiving the wide as the half of the moon (30,5'). The real diameter of 1.2 mio km reaches now the size of our sun.*

1st-3rd of November 2007

1      2

Photo 1; Meade SC 8"/ 2000 mm (3200 mm, 1.6 x dig); Exp. 84sec, ASA 800 Canon 20D (1.Nov,0:15 UTC)

"It" is growing and growing! The expansion wave of the now 1.63 AU (247 Mio km) distanced comet from the earth is measuring in its diameter around 13 arcmin! The green coma reaches with apprx. 32 arcmin over a half degree and is a little bit bigger than the moon. Advice*: The size of the astronomy objects are in relation of the visual figure seen from the earth. That means: 13 arcmin in a distance of 247 million km are standing in proportion to 930.000 km! (Moon diameter only 3400 km).

3   4    5

Photo 3,4; Nikon 300 mm, f4 ( 480 mm,1.6 x dig), Bel. 3 und 1 x 120 sec, ASA 800. Canon 20D (3.Nov,0:15 UTC)

On the photos above you can see a weak tail, but on the left photo you have to amplifiy the contrast and graduation etc. of the image very high.

31. October 2007

Strukturs inside the coma centre!


Team Baader ; Photos originated at Baader Mammendorf. Overview with Canon 600/4, details in the centre photographed through a TEK-APO with 140mm opening and 1 m focal lenght. 8x 2min+4x1min+2x30s, 800-200 ASA. Camera 40D. Regards Martin!


29. October 2007


Meade SC 8"/ 2000 mm (3200 mm, 1.6 x dig); Exp. 22 sec, ASA 800 Canon 20D

Expansion wave since the 27th of October apprx. 2,5 times more in its diameter. With 8 arcmin the comet reaches a quarter of the moon diameter. You can see it with the unaided eye.

Team Baader 8x30s 1600ASA+4x30s 800ASA+2x30s 400ASA, MAK 10" f14, Canon 40D ohne Brennweitenverl. Standort Mammendorf 29.10.22:00h


Nikon 300 mm, f4 ( 480 mm,1.6 x dig), exp. 4 and 11 sec, ASA 800. Canon 20D

The overlighting moon moves away from the constellation Perseus, and the green coma appears again.

26/27. October 2007, nearly full moon!

1 2 3

1)Tamron 28 mm ( 35 mm,1.6 x digitally converted), f 5,6, exposure time 8 sec, ASA 400. Canon 20D

     2,3) Nikon 300 mm ( 480 mm,1.6 x digitally converted), f4, exposure time 7 to 10 sec, ASA 800. Canon 20D

The upper photos were taken in Moosburg Oberbayern

After in the entire Germany and half Europe area a sturdy haze plate had situated itself for five days, not the smallest cloud gap was even to be located in a radius of 300 km. After the first attempt in Lenggries/Jachenau failed completely because of a sudden high fog attack, the new hunt went into the weather broadcast announced mini gap near the city of Regensburg. Of corse it was also the purest haze battle and I had to change the location almost for four times.


Meade SC 200/2000 mm (3200 mm, 1.6 x digitally converted); Exposure row 4sec, 10sec, 32 seconds, ASA 800. Canon 20D

Telescope photos of 26th were taken near Landshut, South Germany

 Diameter of expansion wave , about 3,5' (arcmin); Green coma diameter about 6' (arcmin), Estmated brightness of the coma, 2,2 mag*

It is remarkable that the pressure wave, I suppose it was an explosion, spreads so fast that the size of the sky object daily   increases around 1,2 arcminutes. This would comply an expansion speed around 40.000 km per day. If the expansion wave stays constantly in its brightness, it will may be possible to see a small ring (my own estimation!) with the unaided eye in the night sky. Perhaps a brighter diffuse disk up to full moon size could be observed. Let's wait what is happening the next days /weeks.

But why can we only see a comet without its well-known tail (see comet Swan M4)

This is well explained by the momentary position sun-earth-comet (map). From the viewing point Earth, we can see directly on the nucleus. Behind the nucleus the always sun turned away tail hides, and an asymmetrical brightness inside the expansion wave is the reason.

*mag  = > light magnitude. Up to apprx. mag 5 stars are visible  in the city with the naked eye, in very dark areas to mag 6. --> The more high numerical value is given, the more weak are the objects.

ALL comet reports

  Lovejoy C/2014 Q2   C/2013 R1 Lovejoy  C/2012 S1 ISON   C/2011 L4 PanSTARRS   P1/2009 Garradd    

  C103P/ Hartley     2/09 N3 Lulin      11/08 Holmes      1/07 McNaught    10/06  Swan M4  

  5/06  SchwWAch  1/05  Machholz     5/04: Q4/Neat     3/01: Ikeya-Zhang

More about the comet 17P/ Holmes


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From Etna to Stromboli     Planets & Space

© 2007 photos and text by Baader Team  and (M. Rietze,mr),

© 2007 photos and text by T. Boeckel (tb), last modification 17.11.2007