Comments on: Polaris Brightness Variations are Revived, Astronomers Mystified

By: Vino

Vino — Mon, 28 Jul 2008 09:52:51 +0000

Hi! there is one another group who has done similar work in polaris…the link is http://arxiv.org/abs/0805.1165….
They both are interesting….
regards,
Vino

By: Aodhhan

Aodhhan — Thu, 24 Jul 2008 12:14:28 +0000

Nice job Astrofiend.
Like I stated in a post a few days ago, every once in a while something comes along to mess wtih our constants, and we find the universe isn't the age it was, and distances are different. I wouldn't get too concerned with an outside influence just yet. It may be something passing and unique. In which case we learn how to recognize it and treat it as a signpost which has been turned in the wrong direction.

However, everything isn't just going to be thrown out the window. There may an external reason why this is doing what it is, or it may be a part of its lifecycle we just haven't witnessed before. or we could have missed it totally and we need to get out the tap shoes.

All in all, I love the fact we gain a lot more questions every day than we find answers. Some of us are just sicker than others when it comes to being attracted to the unknown.

By: Astrofiend

Astrofiend — Thu, 24 Jul 2008 02:11:36 +0000

"Bill Says:
July 23rd, 2008 at 6:49 am

"So much for standard candles, they flicker."

>>>Well, it's the amplitude of the variations that is changing in this case, but it is the period of variations has not, and it is this property that is associated with the star's absolute magnitude and hence is useful for determining distance. The amplitude does not matter in terms of using cepheids as a 'standard candle'. Furthermore, there has never been an exception found to the period-luminosity relationship in cepheids. So from that point of view, this observation changes nothing.

However, it is an interesting find, and obviously one that will need an explanation if we can one day hope to say that we understand stars and stellar behaviour.

Bill Says:
July 23rd, 2008 at 8:11 am
"But, John, are not the Cepheids said to be varying by some (unknown) intrinsic property, which is the cornerstone of their use as standard candles?"

>>>The mechanism of variability is not completely unknown. There is a good deal of evidence to suggest that it is due to the repeated ionisation/expansion/deionisation/contraction cycle of the stellar atmosphere. The star heats helium in its atmosphere and ionises it. This plasma then becomes more opaque due to the ionisation, and radiation pressure pushes the atmosphere outwards and expands it. The atmosphere then cools due to the expansion, deionises and becomes less opaque. The atmosphere contracts, heats up and reionises and the cycle continues.

As for what can modify the amplitude of this cycle, I know not, but it is not to hard to envision some process that could modulate the amplitude variation on lengthy timescales while leaving the period essentially unchanged.

By: mike

mike — Wed, 23 Jul 2008 22:02:39 +0000

Let's see now, a trinary star has been observed to decrease in amplitude for a mere 100 years and we expected it to fizzle out and not it not to resume it's former variability?

By: Bill

Bill — Wed, 23 Jul 2008 15:11:09 +0000

But, John, are not the Cepheids said to be varying by some (unknown) intrinsic property, which is the cornerstone of their use as standard candles? Thus the statistically aberrant modification of a Cepheid behavior by unknown external influences should be especially troubling. And we would have to ask why other Cepheids should not vary in response to external influences…or are they already – that would sure make the candles less standard? The exception seems to open a kettle of fish.

By: John Mendenhall

John Mendenhall — Wed, 23 Jul 2008 14:41:47 +0000

Close in Jupiters, the companion stars, whatever . . . something simple will turn up.
Statistically, Cepheids are reliable. Remember, this is the exception, not the rule.

By: Mikel

Mikel — Wed, 23 Jul 2008 13:55:32 +0000

On a more serious note (forget my alien nonsense…it was for fun), we know that Polaris is a trinary star. I wonder if it's possible the other two stars could be having an effect on the Cepheid's variability…

By: LLDIAZ

LLDIAZ — Wed, 23 Jul 2008 13:50:45 +0000

Or a large number of plus jupiter sized planets in its system would create this effect as well…

By: Bill

Bill — Wed, 23 Jul 2008 13:49:06 +0000

So much for standard candles, they flicker. The instrumentation technology is amazing. Stellar theory, however, is in an abysmal state, with far less than predictive power, and seems to be worse off with every new discovery. The plasma behavior…keeping in mind that this ionized stuff constitutes an electric current…hints at the underlying cause of the variation.

By: Mikel

Mikel — Wed, 23 Jul 2008 13:45:05 +0000

No, folks, you all have it wrong. This is actually a signal from an alien species! They know this is our "guiding star", so they're cleverly using it to send us a message. All we have to do is interpret the variations the right way and bingo, we're in the galactic family!

By: Eric Near Buffalo

Eric Near Buffalo — Wed, 23 Jul 2008 13:40:08 +0000

Either dark matter or it's passing through some serious dusty regions in space. Star brightness doesn't fluctuate with its maximum and minimum cycles, correct? If that's true, then I can rule that out for myself.

By: Andy

Andy — Wed, 23 Jul 2008 10:33:35 +0000

Let me see…dark energy, dark matter. I know! Dark plasma! You can't see it or detect it directly but, by studying how it affects ordinary plasma velocity, its existence can be postulated. Got any more mysteries that need solving?