Abstract
Monoceros, Canis Minor, Hydra, Canis Major, Puppis, Lepus, Columba, Pyxis, Antlia, Vela.
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Notes
- 1.
See Appendix 1 for details on astronomical coordinate systems.
- 2.
See Appendix 2 on magnitudes for a description of integrated and combined magnitudes.
- 3.
See Appendix 3 for details on star type and classification
- 4.
This star is in fact not part of the cluster but a foreground star.
- 5.
Filters are mentioned extensively throughout the text, as they really do make a difference, and thus every nebula observer should have one (or two or three). See Appendix 4 for details of the various types of light filters available.
- 6.
The whole process of star formation would be a book in itself. I refer readers to the book Observer’s Guide to Stellar Evolution for a simple, complete and up-to-date introduction to the topic.
- 7.
The quoted magnitude of a cluster may be the result of only a few bright stars, or on the other hand may be the result of a large number of faint stars. Also, the diameter of a cluster is often misleading, as in most cases it has been calculated from photographic plates, which, as experienced amateurs will know, bear little resemblance to what is seen at the eyepiece.
- 8.
See Appendix 5 for details about star clusters.
- 9.
See Appendix 6 for details about double stars.
- 10.
But only if we regard its components as a single object. Otherwise Alpha (α) Monocerotis is the brightest.
- 11.
The subscript indicates the star is variable.
- 12.
Bear in mind that the position angle and separation may change over a short period of time, and so the values given here may be different to what you observe now.
- 13.
The magnitudes given for the deep sky objects is the integrated magnitude, i.e., as if all the stars (or nebula)) were concentrated to the size of one star.
- 14.
The nebula is so large that many differing coordinates can be given, and are, if you trawl through the databases.
- 15.
It may be of interest to note that Hydra is the largest constellation, covering 1,303 square degrees and over 100 degrees long.
- 16.
It was suspected by F. W. Bessel in 1834-5, but actually observed visually by A. G. Clark in 1862.
- 17.
There is some controversy with Sirius, as ancient records suggest (Greek astronomer Ptolemy) that it was a reddish color. Current ideas about stellar evolution cannot explain this discrepancy. It remains unsolved.
- 18.
There is a 9.5 magnitude companion, some 130” away at a P. A. of 187°.
- 19.
In truth, the system is extremely complex, and made up of five components. The inner pair is believed to be about a tenth of an AU apart, less than a quarter of the Mercury-Sun distance. So close, in fact that they must distort each other.
- 20.
Recent research suggests that the star is in fact a distant member of the cluster. However, this contradicts its estimated distance using Hipparcos parallax measurements. The debate, and research, continues.
- 21.
There is some slight evidence that Messier 41 and Collinder 121 are physically related, due to their closeness of 60 light years.
- 22.
The PK designation refers to the planetary nebuae cataloge of Perek and Kohoutek (1967).
- 23.
There is considerable controversy over this star. Some say it is a hypergiant, while others a normal red supergiant. The problem arises because of how one defines the surface of a star. For instance, VY has an average density of 0.000005 to 000010 km/m3, or 100,000 times less dense than Earth’s atmosphere at sea level. So where does the star end and space begin?
- 24.
Many databases give differing values for the variability. Be warned.
- 25.
Over the past several years, many extrasolar planets have been found around stars in the constellation. Alas, we don’t discuss these here.
- 26.
Note that this is ‘k’ and not ‘kappa.’
- 27.
Oddly, there is no object found using Messier’s coordinates, and M47 was considered a lost Messier object. It wasn’t until 1959 that Canadian astronomer T. F. Morris realized that NGC 2422 and M47 were the same thing!
- 28.
It had been suggested that the cluster in fact two different open clusters lying along the same line of sight. This was confirmed in 1996. They are designated as NGC 2451A and NGC 2451B.
- 29.
The star has been classified as a double star, but over the past 100 years, its separation has increased by more than would normally be expected, and thus it is just a line-of-sight coincidence.
- 30.
From a dark location, obviously.
- 31.
This is another example of an object with several quoted magnitudes, ranging from 10.1 to 11.5.
- 32.
A casual glance at a good star atlas will show immediately that this is the only word that can be used!
- 33.
It may be that it is all but unresovable at this time in its orbit, in all but the very largest telescopes.
- 34.
For those interested the third component can be found thus (from the primary): P.A. 27°: Sep. 0.8”.
- 35.
Recent research has shown that this is a chance alignment, rather like NGC 2438 and Messier 46, discussed in the section on Puppis.
- 36.
Some observers report a size of 1.4 by 0.8 arcminutes.
- 37.
Some observers state that the spiral arms show a distinct coiled counterclockwise spiral structure.
- 38.
As well as Antarctica, of course.
- 39.
It has recently been discovered that the primary is itself an eclipsing binary with a drop of nearly 0.5 magnitudes. Why this has never been noticed before is a mystery. In addition it is the brightest star in the entire sky that has no proper name.
- 40.
There are of course many more double, triple and multiple stars in Vela, but only the brightest are mentioned here.
- 41.
We await the inevitable email saying that it has.
- 42.
Those individuals blessed with large equipment may be able to see the planetary nebulae RCW 44 nearly one arc minute northeast of the cluster’s center. Recent research suggests that the nebula is not associated with the cluster.
- 43.
Research suggests that it is not a cluster but rather an OB Association situated near the morphological center of the Gum Nebula, and is in fact responsible for making most the nebula glow, or fluoresce, along with the association Vela OB2.
- 44.
In the north of Trumpler 10 is another faint cluster, NGC 2671, as can be seen on the image.
- 45.
This of course is not visible to the naked eye, or even through modest telescopes, but mentioned due to its enormous size, and thus, importance. It is however a wonderful opportunity of astro imagers.
- 46.
The nebula also contains the Vela Pulsar, the first pulsar to be optically identified.
- 47.
Bear in mind that using an [OIII] filter, or any interference filter, will dim the light from stars, and so a rich star field may not appear rich, when viewed through the filter.
- 48.
Stands for Rogers-Campbell-Whiteoak, in case you were wondering.
- 49.
Scientifically it is also full of surprises. It is a very fast-moving cluster, at 490 km per second, the fastest known of any similar object. It also appears to be moving around the Milky Way in a direction opposite to most other objects, which does suggest that it may be a captured globular cluster or even, at one time, part of another dwarf galaxy.
- 50.
This is the magnitude as estimated from photographic plates.
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Inglis, M. (2018). The Milky Way: January – February. In: Astronomy of the Milky Way. The Patrick Moore Practical Astronomy Series. Springer, Cham. https://doi.org/10.1007/978-3-319-72950-3_2
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