Blink Comparator - Humason (1922) vs Wallis-Provin (~1997)
(Comparator needs a bit more tweaking.)
Van Maanen's Plate XV(1), with comparison stars labeled in red.
Two VLA/VLBI water maser study areas are indicated by green crosses.
An image scale is shown in red in the lower left-hand corner.
The scale of the motions is indicated in the lower right-hand corner (left-hand in
The length of the arrows represents the motions during an interval of 2,500 years.(1) Pg. 267.
A spreadsheet with the comparison stars data and scaling calculations is at: m33rcm.xls.
van Maanen's image above has been East-West "mirrored" to match conventional celestial
maps. Each pixel in the image has an estimated angular size of two arcsecs.
According to van Maanen's proper motion velocity measurements, none of his comparison stars should have moved enough since 1922 to have changed their photographic positions by at least one pixel on this digitized image. In contrast, the rapid mover (#367), which van Maanen rejected as being a member of the nebula, could have moved by as much as three pixels. (This appears to have happened.
Notes on the crude blink comparators below
[Added 14 Apr 2007.]
Exaggerated radial distortions
in Ritchey's 1910 image.
Exaggerated radial distortions
in a 4-part CCD photo mosaic
M33 Dark Star Image by Tony Pilato
M33 Photo Mosaic by Rob Gendler
* * *
- - -
Comments on Knut Lundmark's "Studies of Anagalactic Nebulae"
See the blink comparator (its not aligned right yet) which shows van Maanen's internal motions compared to Lundmark's.
- - -
Comments on VLBI/VLBA M33 Internal Proper Motion StudiesSee: Brunthaler, A., Reid, M.J., Falcke, H., Greenhill, L.J., Henkel, C.,
The Geometric Distance and Proper Motion of the Triangulum Galaxy (M33),
Science, 307, 1440-1443 (2005) (4)
Two regions of water vapor maser activity in M33 have been being studied for internal motions since 1987(3)(4) using NRAO VLBI and VLBA facilities. The following image shows the locations of these two areas.
M33 showing NRAO VLBI/VLBA locations for water vapor masers.
Predicted motions (white arrows) are based on a M33 rotation curve and geometric/kinematic considerations.
VLBA measurements [inserted by author of this webpage] are shown in red.
These two water maser regions are indicated by green crosses on the van Maanen image at the top of this page.
VLBI/VLBA M33 Commentary
(II) - On page 39 of the 16 Aug 2004 report [pdf] Mapping the Future of VLBI Science in the U.S., it is stated, "...the Committee received consistent input from a significant number of [VLBI] community members, as well as individuals serving on the Committee itself, that the current state of VLBI-related software leaves much to be desired." [Added 30 Oct 2005.] [Report can be reached by Googling the underlined title. 30 May 2011]
(III) - Brunthaler et al(4) say that the water maser regions they studied are in the eastern half of M33. The masers are actually in the western half. Van Mannen(1) published an image of M33 as though it were being viewed from outside the celestial sphere. His annotations on Humason's 1922 plate (shown at the top of this web page) thus have East on the right and west on the left, but the nebula and directions are consistent. (His image has been mirrored on this page to show a conventional representation of the nebula.) [Added 26 Jul 2006.]
- - -
Where van Maanen May Have Gone WrongAdded 20 Aug 2009
On page 1441 of Brunthaler, et al(4), it is stated:
"The maser emissions in M33/19 and IC 133 are variable on time scales less than one year. Between epochs, new maser features appeared and others disappeared. However we were able to detect and follow the motions of four features in M33/19 and six features in IC 133 over all four epochs. The feature identification was based on the positions and radial velocities of the maser emissions."
(They detected 29 distinct emission features.)
If van Maanen's nebulous objects had similar lifetimes, and his minimum period between epochs was 12 years (radial velocities were not used as tracking aids), he could end up identifying totally different nebulosities as being one and the same. In 1917 Kotinsky(5) measured internal motions in M51. His measured proper motion magnitudes were comparable to those found by van Maanen, but the motions were in the opposite direction. (One other astronomer at the time found similar results.) Knut Lundmark used van Maanen's M33 starting points and found similar proper motion magnitudes but the orientation of the majority of the velocity vectors were inconsistent with those done by van Maanen. (see the van Maanen - Lundmark M33 blink comparator.)
It could be that each of these observers found what they were looking for. As far as that goes, Brunthaler, et al might have a problem as well. They set aside more than half of their detected features because of non-conformance with position and/or radial velocity expectations.)
Here is a graph (based on Table 1, ref(4)) showing the NRAO H2O M33 Maser observation dates.
It would be helpful to employ a time-wise intensive VLBI/VLBA observing regimen that would have a short enough delay between epochs such that no newly formed maser region could be misidentified as the continued presense of an earlier faded maser region. (Or so that features whose proper motions are faster than what currently accepted ideas allow don't get tossed.)
(2) Knut Lundmark, "Studies of Anagalactic Nebulae - First Paper," Nova Acta Regiae Societatis Scientiarum Upsaliensis, Volumen Extra Ordinem Editum, (1927).
(3) A.L. Argon, L.J. Greenhill, J.M. Moran, M.J. Reid, K.M. Menten, M. Inoue, "The IC 133 Water Vapor Maser in the Galaxy M33: A Geometric Distance" - Astrophysical Journal, 615, 702 (2004).
(4) A. Brunthaler, M.J. Reid, H. Falcke, L.J. Greenhill, C. Henkel, "The Geometric Distance and Proper Motion of the Triangulum Galaxy (M33)", Science, 307, 1440, (2005) - NADS - [Link to Jive pdf no longer works. 21 Aug 2009.]
(5) Kostinsky, S., "Probable Motions in the Spiral Nebula Messier 51 (Cannes Venatici) Found With the Stereo-comparator. Preliminary Communication," MNRAS, 77, 233 (1917) - NADS
Up one level |