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Somebody give this star a speeding ticket.

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15 years 9 months ago - 15 years 9 months ago #72447 by bertthebudgie
Replied by bertthebudgie on topic Re:Somebody give this star a speeding ticket.
Wow what a find dg. I wonder would the difference in proper motion due to the fact that the dss image was taken in April and yours in August thus adding the Earths orbital movement to you calculation?.

I mean as it is a nearby star could it be the stars paralax you are measuring rather then its true proper motion. Means you need to take another image in 6 months to be sure:)

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Last edit: 15 years 9 months ago by bertthebudgie.

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15 years 9 months ago - 15 years 9 months ago #72483 by JohnMurphy
Replied by JohnMurphy on topic Re:Somebody give this star a speeding ticket.
Nice result DG. Nice research Vagelis (say hi to Kiriakee for me, and of course all the gang - missing you all - hope to see you next June).
DeeBee - Parallax would affect all stars in the field thereby negating any differentiation. Think of it this way - there are many stars in the field, incl. galaxies with widely different distances from earth, yet they show no apparent movement. Unless the star in question is very close we should see no discrepancy

Clear Skies,
John Murphy
Irish Astronomical Society
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Last edit: 15 years 9 months ago by JohnMurphy.

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15 years 9 months ago #72497 by bertthebudgie
Replied by bertthebudgie on topic Re:Somebody give this star a speeding ticket.
You are correct. But I understand that this star is very close to us.

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15 years 9 months ago #72568 by cobyrne
Replied by cobyrne on topic Re:Somebody give this star a speeding ticket.
Dave Grennan wrote:

I carried out an astrometric analysis and discovered the following
DeltaA (Diff in RA) = .73"
DeltaD (Diff in Dec) = 3.68"

This thus corresponds to;

PMRA = 38.42 mas/yr
PMDEC = 193.68 mas/yr

Are you sure you did your calculations correctly? It looks to me as if the star is moving more in RA than it is in DEC. Did you remember to multiply your RA seconds by 15 to convert to arc seconds? That would have given you 576.3 mas/yr - 38% more than what simbad gives, but at least the right order of magnitude.

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15 years 9 months ago #72574 by cobyrne
Replied by cobyrne on topic Re:Somebody give this star a speeding ticket.
The parallax of the star is given in SIMBAD as 44.4 mas plus-or-minus 3.3 mas.

So it's distance from us is 1.0 / 0.0444 = 22.5 parsecs = 73.4 light years (plus-or-minus 5.5 light years).

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15 years 9 months ago #72576 by DaveGrennan
Replied by DaveGrennan on topic Re:Somebody give this star a speeding ticket.
You are spot on Chris. Thats exactly what I did.

I had forgotten to convert it to angular degrees. The correct value should be therefore;

.73 * (15 * cos(41)) = .73 *11.3206 = 8.2641" which equates to a PMRA of 435mas/yr. This is much closer to the published value.

Regards and Clear Skies,

Dave.
J41 - Raheny Observatory.
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