M51 Hubble Remix (2009 Dec 26)

[APOD Robot]

M51 Hubble Remix

Explanation: The 51st entry in Charles Messier's famous catalog is perhaps the original spiral nebula - a large galaxy with a well defined spiral structure also cataloged as NGC 5194. Over 60,000 light-years across, M51's spiral arms and dust lanes clearly sweep in front of its companion galaxy (right), NGC 5195. Image data from the Hubble's Advanced Camera for Surveys has been reprocessed to produce this alternative portrait of the well-known interacting galaxy pair. The processing has further sharpened details and enhanced color and contrast in otherwise faint areas, bringing out dust lanes and extended streams that cross the small companion, along with features in the surroundings and core of M51 itself. The pair are about 31 million light-years distant. Not far on the sky from the handle of the Big Dipper, they officially lie within the boundaries of the small constellation Canes Venatici.

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[Jay]

Is today's image orientation ninety degrees off to the left?

MGC 5195 is supposed to appear to the right, but seems to
be at the top...

Just wondering.


BTW, whatever resolved with the triple sunrise image?

[neufer]

Is today's image orientation ninety degrees off to the left?

MGC 5195 is supposed to appear to the right, but seems to
be at the top...

It' supposed to be a snowman.

BTW, whatever resolved with the triple sunrise image?

Double pained glass.

[Chris Peterson]

Is today's image orientation ninety degrees off to the left?

Actually, this is a "properly" oriented image: north up, east left. That is how astronomical images are conventionally presented, since this matches the orientation you see if you look upwards and think in terms of equatorial coordinates. Of course, many images are commonly presented at other angles for aesthetic reasons, or because of constraints created by the sensor aspect ratio.

[neufer]

<<Recent simulations bear out that M51's spiral structure was caused by NGC 5195 passing through the main disk of M51 about 500 to 600 million years ago. In this model, NGC 5195 came from behind M51 through the disk towards the observer and made another disk crossing as recently as 50 to 100 Myrs ago until it is where we observe it to be now, slightly behind M51.

A black hole, surrounded by a ring of dust, is thought to exist at the heart of the spiral. The dust ring stands almost perpendicular to the relatively flat spiral nebula. A secondary ring crosses the primary ring on a different axis, a phenomenon that is contrary to expectations.>>

[DavidLeodis]

Is today's image orientation ninety degrees off to the left?

Actually, this is a "properly" oriented image: north up, east left. That is how astronomical images are conventionally presented, since this matches the orientation you see if you look upwards and think in terms of equatorial coordinates. Of course, many images are commonly presented at other angles for aesthetic reasons, or because of constraints created by the sensor aspect ratio.

But this does not alter the fact that the text in the explanation states that the companion galaxy NGC 5195 is to the right, when surely it should state it is above M51 in the image. It may be obvious it should state above, but it is confusing.

Sorry if I seem picky today but the "The pair are about 31 million light-years distant" in the explanation has a link to information where it states it is 37 million years.

It's a great image though.

[Case]

the "The pair are about 31 million light-years distant" in the explanation has a link to information where it states it is 37 million years.

The SEDS page for M51 states: "The value of M51's (and the whole group's) distance is still not very well known. Our value, of 37 Mly, is based on photometric methods and e.g. given by Kenneth Glyn Jones. Some authors give significantly lower values (less than 20 Mly), but a recent (2001) STScI Press Release gave 31 million light years."

Wikipedia quotes a 2006 article for the distance, that concluded 7.1 ± 1.2 Mpc, or 23 ± 4 Mly.
NED says 7.7 Mpc, or 25 Mly for M51.
Both are quite a lot closer.

[Chris Peterson]

But this does not alter the fact that the text in the explanation states that the companion galaxy NGC 5195 is to the right, when surely it should state it is above M51 in the image. It may be obvious it should state above, but it is confusing.

Ah... I misunderstood the issue.

The source of the problem is clear: the caption was cribbed directly from a previous M51 APOD in which the companion galaxy was indeed to the right in the image. In this repeat, however, the image itself is rotated, and the caption is no longer accurate in this respect. It should properly say "north" or "above".

[DavidLeodis]

the "The pair are about 31 million light-years distant" in the explanation has a link to information where it states it is 37 million years.

The SEDS page for M51 states: "The value of M51's (and the whole group's) distance is still not very well known. Our value, of 37 Mly, is based on photometric methods and e.g. given by Kenneth Glyn Jones. Some authors give significantly lower values (less than 20 Mly), but a recent (2001) STScI Press Release gave 31 million light years."

Wikipedia quotes a 2006 article for the distance, that concluded 7.1 ± 1.2 Mpc, or 23 ± 4 Mly.
NED says 7.7 Mpc, or 25 Mly for M51.
Both are quite a lot closer.

Thanks Case. Interestingly the link that I mentioned in the explanation is also to a SEDS page. I've noticed though that page has "Last Modification: April 18, 1998" so its information is probably not that which is currently thought to be.

[DavidLeodis]

But this does not alter the fact that the text in the explanation states that the companion galaxy NGC 5195 is to the right, when surely it should state it is above M51 in the image. It may be obvious it should state above, but it is confusing.

Ah... I misunderstood the issue.

The source of the problem is clear: the caption was cribbed directly from a previous M51 APOD in which the companion galaxy was indeed to the right in the image. In this repeat, however, the image itself is rotated, and the caption is no longer accurate in this respect. It should properly say "north" or "above".

Thanks Chris. That explains why the position of NGC 5195 is stated wrongly in the explanation.