Barnard's Star
Proper Motion Explained!
So, what's the story behind Barnard's star and specifically why don't I
get what I expect to see when it is plotted in TheSky
Astronomy Software?
Barnard's star has the highest proper motion of any star in the
entire sky. In fact, this star moves at ~10.3 arc seconds each year!
Since this star is included in the Hipparcos catalog (in TheSky
use Edit | Find HIP 87937)
the input data contains the necessary information to accurately compute the
position of the star (proper motion) over time. The following charts created by show the position of Barnard's
star over a period of 50 years.
TheSky6 uses the even more
complete and very accurate UCAC-2/USNO-B1 stellar data also containing an entry with
proper motion for Barnard's star.
TheSky5 Display
10 year increments
The red line is the projected path
indication direction and amount the star will move over a 10 year
period. The length of this vector line can be up to a realistic 10,000 years! Note the
small yellow reference marker is the position from Brian Skiff's latest catalog
of Landolt standards data which can also be used with TheSky 5
or TheSky version 6 by using the Database
Manager.
Enabling Proper Motion TheSky version 5
Enabling Proper Motion
Stellar Options
Note that the GSC and Hipparcos/Tycho catalogs can be turned
on and off as needed. This is also true of the USNO A 2.0 stars, both the 550
million stars on 11 CD-ROM's and the single CD of 54 million stars.
Please see the following document for details on how to use the USNO
data in TheSky.
Enabling Proper Motion TheSky6
Use View | Stellar Options and select the "Catalogs/Astrometry"
tab.
Stellar Options dialog
Under "Proper motion" select Compute as shown
Note in TheSky6 the newer USNO-B 1.0 subset stellar
data and the UCAC2 (50 million total stars) can also be selected and deselected
along with the GSC, Hipparcos/Tycho and USNO A 2.0 data accordingly.
If you wish to see how much a star with proper motion is going
to move over a long period of time enable the Draw vector options and select the
number of years you are interested in. Most stars do not move appreciably
over a short period (say a couple of years) so normally entering 100 to 1000 or
more years is realistic.
Narrow field around M67
1,000 years of proper motion
Due to the number of questions regarding errors in data plotted
in TheSky the following article in
Sky and Telescope was prompted by me and
written by Stuart Goldman. Hats off to Mr. Goldman for his excellent job!
More details on catalog input errors can be found here CATALOG
CAPRICIOUSNESS. Along the same lines the question as to why
TheSky does not "split" the Trapezium stars in the Orion Nebula is
here Where is the
Trapezium?
Another feature in TheSky is the ability
to create images from the Palomar Sky Survey distributed on the 102 CD-ROMS or the
compressed version of 18 CD-ROMS known as RealSky.
So provided you have the data available, with a single mouse click
TheSky can create the same field (1 degree or less) using Software Bisque's programs CCDSoft
or RealSkyView
as shipped with the RealSky data.
One of the biggest advantages to using the Palomar data is the
fact that the data created is
from an actual photograph. Therefore it is not subject to catalog input
errors (exception stars with high proper motion and/or minor planets, planets,
and comets). In the case of Barnard's star note the position of the star
on the photograph that was taken in July of 1950! As you can see from the
above image showing the year 2000 position the star is in a completely different
location, that is to say Barnard's star has in fact moved appreciably over the
years.
Now, to take it one set further CCDSoft
will take the above image and set TheSky's Site information based on the
information found in the FITS header and create an equivalent field. Using
CCDSoft's unique
feature Research | Comparison | Star Chart the same corresponding field is
created in TheSky!
Grid lines and labels
Example TheSky Display
Blink compare
Palomar Sky Survey digitized photograph and TheSky Display
RealSky/DSS
Copyright
Note the star cataloged as GSC 425:184 is obviously an error due
to the changing position of this star! The entry for this star in
the GSC catalog was actually created in 1981 and that is where the star was at
that time. The GSC
catalog is prone to many errors (millions in fact) but this very valuable
catalog is still being used for many reasons although it will most likely be
replaced by most astronomy programs in the near future. Now consider the same field with only the
Hipparcos and Tycho data,
Hipparcos/Tycho Data Only
Quit a different story, indeed
Now the same field with USNO, GSC, and Hipparcos/Tycho
plotted. So as one can clearly see TheSky is very flexible.
One more feature found in TheSky is
Image
Link. Image
Link allows the end user to place
their own photographs or CCD images into the display for analysis.
TheSky with DSS image and catalog data plotted
Fantastic!!
RealSky/DSS
Copyright
No question as to how accurate the plotting of the stars in
TheSky is now. And finally an image from TheSky6 showing the UCAC2,
USNO-B1 Full, GSC, and Hipparcos/Tycho data.
TheSky6 plotting over 1 billion stars!
Wow! Nearly ever star on the Palomar image accounted for!
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