Color changing star?

I had my telescope out a little over an hour ago looking at the moon
and stars and noticed something odd. There was a star(?) maybe west
southwestish, I dunno, I was just messing around. What was wierd was
that it changes colors, between greenish and red, sort of like a tacky
christmas light. I'm in central North Carolina and it was about a
fifth of the way up the sky. Anyone know what the heck it is? I
thought maybe a satelite but I wouldn't expect it to be so bright and
maybe to move more than it did. Anyone have any clue?

In article .com,
wrote:

I had my telescope out a little over an hour ago looking at the moon
and stars and noticed something odd. There was a star(?) maybe west
southwestish, I dunno, I was just messing around. What was wierd was
that it changes colors, between greenish and red, sort of like a tacky
christmas light. I'm in central North Carolina and it was about a
fifth of the way up the sky. Anyone know what the heck it is? I
thought maybe a satelite but I wouldn't expect it to be so bright and
maybe to move more than it did. Anyone have any clue?

It's quite common for a star's scintillation (twinkling) to make it
flash in a variety of colours. The effect is especially pronounced for
bright stars near the horizon when the atmosphere is turbulent. We
usually think of twinkling mainly as a fluctuation in brightness, but
where the various wavelengths in the star's light are refracted
differently (as by a prism, or in a rainbow), the colour will appear to
change as well.

--
Odysseus

"Odysseus" wrote in message
news
In article .com,
wrote:

I had my telescope out a little over an hour ago looking at the moon
and stars and noticed something odd. There was a star(?) maybe west
southwestish, I dunno, I was just messing around. What was wierd was
that it changes colors, between greenish and red, sort of like a tacky
christmas light. I'm in central North Carolina and it was about a
fifth of the way up the sky. Anyone know what the heck it is? I
thought maybe a satelite but I wouldn't expect it to be so bright and
maybe to move more than it did. Anyone have any clue?

It's quite common for a star's scintillation (twinkling) to make it
flash in a variety of colours. The effect is especially pronounced for
bright stars near the horizon when the atmosphere is turbulent. We
usually think of twinkling mainly as a fluctuation in brightness, but
where the various wavelengths in the star's light are refracted
differently (as by a prism, or in a rainbow), the colour will appear to
change as well.

--
Odysseus

You don't state the time but it might have been Sirius if early evening.
Did you also see Venus to the West, brighter than the star that was changing
colours?

It is unlikely that Venus would show colour variations the way a star would;
the angular size of the disk would tend to prevent it unless the seeing was
very bad indeed.

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

In article ,
Mike Dworetsky wrote:

"Odysseus" wrote in message
news
In article .com,
wrote:

I had my telescope out a little over an hour ago looking at the moon
and stars and noticed something odd. There was a star(?) maybe west
southwestish, I dunno, I was just messing around. What was wierd was
that it changes colors, between greenish and red, sort of like a tacky
christmas light. I'm in central North Carolina and it was about a
fifth of the way up the sky. Anyone know what the heck it is? I
thought maybe a satelite but I wouldn't expect it to be so bright and
maybe to move more than it did. Anyone have any clue?

It's quite common for a star's scintillation (twinkling) to make it
flash in a variety of colours. The effect is especially pronounced for
bright stars near the horizon when the atmosphere is turbulent. We
usually think of twinkling mainly as a fluctuation in brightness, but
where the various wavelengths in the star's light are refracted
differently (as by a prism, or in a rainbow), the colour will appear to
change as well.

--
Odysseus

You don't state the time but it might have been Sirius if early evening.
Did you also see Venus to the West, brighter than the star that was changing
colours?

It is unlikely that Venus would show colour variations the way a star would;
the angular size of the disk would tend to prevent it unless the seeing was
very bad indeed.

Otoh Venus is so much brighter that you can see it right down to the
horizon: if the air is clear, you can expect a horizontal extinction
around 5 magnitudes. Which will make Venus appear to shine at
magnitude +1 or so right before it sets -- and then it *will* twinkle,
often in different colors. But you need a really unobstructed view of
the horizon to be able to see this.

--
Mike Dworetsky

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--
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e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

"Paul Schlyter" wrote in message
...
In article ,
Mike Dworetsky wrote:

"Odysseus" wrote in message
news
In article .com,
wrote:

I had my telescope out a little over an hour ago looking at the moon
and stars and noticed something odd. There was a star(?) maybe west
southwestish, I dunno, I was just messing around. What was wierd was
that it changes colors, between greenish and red, sort of like a tacky
christmas light. I'm in central North Carolina and it was about a
fifth of the way up the sky. Anyone know what the heck it is? I
thought maybe a satelite but I wouldn't expect it to be so bright and
maybe to move more than it did. Anyone have any clue?

It's quite common for a star's scintillation (twinkling) to make it
flash in a variety of colours. The effect is especially pronounced for
bright stars near the horizon when the atmosphere is turbulent. We
usually think of twinkling mainly as a fluctuation in brightness, but
where the various wavelengths in the star's light are refracted
differently (as by a prism, or in a rainbow), the colour will appear to
change as well.

--
Odysseus

You don't state the time but it might have been Sirius if early evening.
Did you also see Venus to the West, brighter than the star that was
changing
colours?

It is unlikely that Venus would show colour variations the way a star
would;
the angular size of the disk would tend to prevent it unless the seeing
was
very bad indeed.

Otoh Venus is so much brighter that you can see it right down to the
horizon: if the air is clear, you can expect a horizontal extinction
around 5 magnitudes. Which will make Venus appear to shine at
magnitude +1 or so right before it sets -- and then it *will* twinkle,
often in different colors. But you need a really unobstructed view of
the horizon to be able to see this.


I agree, but he described it as "about a fifth of the way up in the sky",
which does not sound like very near the horizon to me. Hence my guess that
he might be seeing Sirius, which normally shows just the effects described,
and which should be about the right elevation in the early evening. The
obvious question is whether he saw Venus at the same time as a different
object.

--
Mike Dworetsky

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