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The Sky This Month - November 2007

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Written by Gary Boyle, Ottawa on
Post Date: 
Sun, 2007/11/04

What a Comet !!!

The biggest story of the month is the unexpected outburst of 17P/Comet Holmes. This outburst occurred over a short 24 hour period starting October 23rd. By the 24th, the comet had increase its brightness from magnitude 17.5 to magnitude 2.5, that is an order of one million times. At the time of writing this article the comet halo is still growing but the inner portion is fading a bit. It is still a very impressive object.

Astronomers are not sure how long the spectacle in the North will last. We do know this comet has had previous outbursts in the past. In fact that is how E. Holmes of England discovered it on the night of November 6 1892. Of all thing, it was determined the comet’s date of perihelion to the Sun (at a distance of 2 astronomical units) was back on August of that year and the outburst occurred when it was about a month past the Earth – as it returned to the depths of the solar system. It did however undergo another outburst some three month after discovery when the nucleus was spotted to be 8th magnitude and only seen in a telescope.

 

 

Comet Holmes has a 7 year return period. The 1899 return did not produce any outburst and has been quiet until last month. A possible explanation of these sudden brightening is the Comet might possess ‘sink holes’. As Holmes rounded the Sun, gravitational forces probably weaken these areas and it gave way thus releasing an enormous amount of fresh inner material to the solar winds.

Aside to this marvel of the night let us look ahead to November skies and the constellations of Aries, Pisces, Cetus and Eridanus areas contain some interesting objects. We first start of NGC 772, a 10.3 magnitude giant galaxy. Estimated to measure some 250,000 light years (ly) in length, it is situated about 130 million ly away. This galaxy was quite popular back in 2003 as two supernovae were discovered over the course of three weeks. NGC 772 looks distorted thanks to a companion E3 galaxy pulling at it.

 

 

M77 in Cetus is a good example of an active galaxy. This face on is also the prototype to the famous group of objects call the Seyfert galaxies. M77 is estimated to reside about 60 million ly away and holds a decent brightness at magnitude 8.9.

NGC 488 is another face on Sb spiral galaxy. It possesses a large bright nucleus and narrow – tightly wrapped bluish coloured arms. NGC 488 lies 90 million ly away and glows at magnitude 10.3. One of two planetary nebulas featured this month is NGC 246.

Although it is listed at magnitude 10.3 it is a challenge in small telescopes due to the low surface brightness and colour. You will uncover the four stars associated with the planetary including the 12th magnitude central star but that is it. Large scopes will reveal the faint nebulosity as well as the dark hole off center. An OIII filter will help matters.

The globular cluster NGC 288 measuring some 14 arc minutes across. Averted vision is required to resolve the clusters members. NGC 288 glows at magnitude 8.1 and is estimated to be 39,000 ly from us. Moving one and three-quarter degrees to the north and gaze at the great Sculptor Galaxy – NGC 253. With wide angle photography, you will catch both in the same portrait. Catalogued at magnitude 7.8, this almost edge on galaxy is about as wide as the Moon – taking up a half a degree of sky. Take you time on this lovely as you will pick up dark lanes, dark patches knot and mottling.

NGC 1300 is a classic version of a barred spiral galaxy is estimated to be 75 million ly away. Its brightness is pegged at magnitude 10.5 but is diffuse because of its face on orientation. This distant galaxy is estimated to be 150,000 ly across. Within one and a half lunar widths above NGC 1300 you will first come across NGC 1297, a magnitude 13 round galaxy.

We end off with the second planetary on the chart – NGC 1535. Moderate telescopes will reveal a greenish inner disk along with a faint outer halo – all surrounding a 12th magnitude central star. NGC 1535 is however fairly small object.

 

 

Even though Jupiter - the King of planets is now lost in the solar glare, there are five other planets to choose from. First there is Neptune embedded in the constellation Capricornus. At magnitude 7.9, a telescope or binoculars are a must in capturing this tiny blue ball. Move over one constellation to the left to Aquarius to find brighter Uranus. This bluish-green fuzz might first looks like a planetary nebula but the absent central star says it is not. Uranus is just under naked eye visibility at magnitude 5.8.

Next we have the mysterious red planet – Mars. Very prominent tinge of bright orange makes it the bright object in its base constellation of Gemini. Mars will be at its best for seeing close to Christmas. Mars will reach opposition on December 24 but is closest to the Earth on December 19 at about 88 million km. Mars and Orion (on its side) rise at the same time. The red planet begins its retrograde motion on November 15. By the end of this month, Mars will shine at magnitude -1.2. Keep following and photographing this wonderful planet.

As the night wears on, the early morning sky sets the stage for Saturn and the brilliant Venus. However Venus is slowly sliding down to the eastern horizon but will remain a morning object until its superior conjunction on June 9, 2008. Saturn is located 7 degrees to the left of Regulus (Alpha Leonis). As the months move on, the ringed wonder will rise earlier and earlier.

 

Object

Type

Magnitude

Coordinates

M 74

Spiral galaxy

9.2

RA:01h 37m 8.9s Dec:+15d 49' 37"

M 77

Round galaxy

8.8

RA:02h 43m 7.8s Dec:+00d 01' 13"

NGC 0055

Elongated galaxy

8.0

RA:00h 15m 19.7s Dec:-39d 08' 24"

NGC 0246

Planetary nebula

8.0

RA:00h 47m 25.3s Dec:-11d 50' 18"

NGC 0247

Elongated galaxy

8.9

RA:00h 47m 31.1s Dec:-20d 43' 20"

NGC 0253

Elongated galaxy

7.1

RA:00h 48m 0.9s Dec:-25d 14' 21"

NGC 0257

Round galaxy

14.0

RA:00h 48m 31.9s Dec:+08d 21' 45"

NGC 0268

Round galaxy

13.0

RA:00h 50m 37.5s Dec:-05d 09' 17"

NGC 0488

Elongated galaxy

10.3

RA:01h 22m 14.0s Dec:+05d 17' 39"

NGC 0584

Elongated galaxy

10.4

RA:01h 31m 43.3s Dec:-06d 49' 24"

NGC 0613

Spiral galaxy

10.0

RA:00h 50m 37.5s Dec:-05d 09' 17"

NGC 0720

Elongated galaxy

10.2

RA:01h 53m 24.7s Dec:-13d 41' 31"

NGC 0772

Round galaxy

10.3

RA:01h 59m 45.5s Dec:+19d 03' 30"

NGC 0908

Elongated galaxy

10.2

RA:02h 23m 29.6s Dec:-21d 11' 41"

NGC 1232

Spiral galaxy

9.9

RA:03h 10m 11.1s Dec:-20d 33' 00"

NGC 1300

Barred spiral galaxy

10.4

RA:03h 20m 5.1s Dec:-19d 23' 05"

NGC 1332

Elongated galaxy

10.3

RA:03h 26m 40.8s Dec:-21d 18' 08"

NGC 1398

Round galaxy

9.7

RA:03h 39m 15.8s Dec:-26d 18' 14"

NGC 1407

Round galaxy

9.8

RA:03h 40m 35.0s Dec:-18d 33' 15"

NGC 1535

Planetary nebula

10.0

RA:03h 39m 15.8s Dec:-26d 18' 14"

 

What was a meteor storm a few years ago, the Leonids will peak on November 18th at 3:00 UT. But don’t hold you breath on this one as rates are expected to be 5 to 15 per hour. In fact sporadic meteor (non shower meteors) might outnumber this year’s Leonids.

Observe and enjoy Comet Holmes as often as you can, before its fades. Until next month, clear skies everyone.

Gary Boyle