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NGC5906 - Splinter Galaxy

(Ivor Trueman)
(Ivor Trueman)
Cropped close-up (Ivor Trueman)
(James Clark)
(NGC5905 & NGC5908 James Clark)
(NGC5906 James Clark)

Information...

NGC5906 (also known as NGC5907) is an edge-on spiral galaxy in the constellation of Draco, approx. 50 million light years away from Earth.

Also captured in Ivor Trueman's image are 33 more distant galaxies, including a faint smudge belonging to PGC2551882 which works out at approx. 5 billion light years away. The light captured from this galaxy left it's system at about the time our Sun was first formed, about half the age of the Milky Way.

In James Clark's wider-field image, you can also see the edge on Spiral galaxy is NGC5908 & the disturbed face-on spiral galaxy is NGC5905. The latter is a HII galaxy which generally are starburst galaxies with low metallicity and a high perctange of neutral hydrogen.

For more info. see the Wikepedia entry.

 

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Map

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Measuring Angles

Hold your arm at full length, then close one eye & use the hand shapes shown above to measure the angular distance between the stars.

(Ain't anatomy wonderful!)

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Apparent Magnitude

The apparent magnitude of a star is a measure of how bright it appears from Earth. The scale was introduced over 2,000 years ago by the Greek astronomer Hipparchus, who grouped stars into six categories. The brightest 20 or so were deemed to be 'first magnitude', slightly dimmer stars 'second magnitude', and so on until the barely visible stars were classed as 'sixth magnitude'.

Later it was recognised that our eyesight, once it has been given time to get used to darkness, has a logarithmic response. i.e. a Mag. 1 star is actually 2.512 times brighter than a Mag. 2 star, or 6.310 times brighter than a Mag. 3 star (2.512 x 2.512 = 6.310).

The six Magnitudes thus corresponds to a 2.5126 difference in brightness or 100x.

Apparent magnitude

Today the scale has now been extended, so that brighter objects can have an apparent magnitude of 0 or even negative. The brightest star Sirius, for example, has an apparent magnitude of -1.44 and the Sun is a whopping -26.74, due to it's close proximity to Earth.

 

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