Does a particular star's brightness change throughout the year?

[KurtLudwig]

TL;DR Summary

Does a particular star's brightness change throughout the year?

Since the Earth orbits around the sun and very slightly changes its relative angle and position, does the brightness of a particular star change from season to the season?

 

[Vanadium 50]

Not noticeably (other than trivialities like "below the horizon")

The Earth's position changes by 16 light minutes in six months. The nearest star is 4 light years away.

 

[DaveC426913]

There are certainly things that can change a star's apparent brightness. Clear/hazy skies is one, dark/bright skies is another.

But, as Van says, certainly not the geometry of our Solar System. Even for the nearest star, that change is on the order of one part in 125,000.

 

[Janus]

And there are such thing as variable stars. Mira is one example. It has a period of ~332 days, and can actually vary enough in brightness to go from not being visible at all with the unaided eye to being one of the brighter stars in the sky.

 

[DaveC426913]

Ah. Was wondering if variable star variance could be spotted with the naked eye...

 

[Vanadium 50]

Omicron Ceti goes from visible to invisible on a ~yearly cycle. But it has nothing to do with Earth's orbit.

 

[stefan r]

Ah. Was wondering if variable star variance could be spotted with the naked eye...

A lot of people noticed Betelgeuse last winter.

Algol was associated with bad luck in ancient Egypt. Ptolemy said it was Perseus's demon. The variability was probably noticed by ancients but the measurement of the variability was not explicitly mentioned.

 

[KurtLudwig]

Janus wrote: "And there are such thing as variable stars. Mira is one example. It has a period of ~332 days, and can actually vary enough in brightness to go from not being visible at all with the unaided eye to being one of the brighter stars in the sky."
How can a star change brightness to such a degree? The nuclear reaction cannot diminish and then again increase in cycles of 332 days. Is the star's light blocked by a black hole? No, a black hole would generate a distorted image of the star. What process is responsible?

 

[Vanadium 50]

As it says on Wikipedia, "They are pulsating due to the entire star expanding and contracting. This produces a change in temperature along with radius, both of which factors cause the variation in luminosity. The pulsation depends on the mass and radius of the star and there is a well-defined relationship between period and luminosity (and colour). The very large visual amplitudes are not due to large luminosity changes, but due to a shifting of energy output between infrared and visual wavelengths as the stars change temperature during their pulsations."

 

[KurtLudwig]

I should have checked on Wikipedia first. Thank you.

 

[sophiecentaur]

One of the methods that was discovered for finding the distance to a star is based on parallax. The Earth's orbit is 2AU in diameter and that amount of movement is enough to see relative movement of closer stars to the more distant stars that appear 'fixed'. Astronomical distance are often quoted in Parsecs.

I could imaging that parallax due to our solar orbit could also account for occultation of a distant bright star by large dark star once or twice a year. Someone is bound to have looked for this amongst the vast amount of data that we now have. Spotting such variations comes under the heading of 'Transient Astronomy' and there is a lot of juice in that particular lemon - it just needs to be found amongst existing data.

 

[stefan r]

One of the methods that was discovered for finding the distance to a star is based on parallax. The Earth's orbit is 2AU in diameter and that amount of movement is enough to see relative movement of closer stars to the more distant stars that appear 'fixed'. Astronomical distance are often quoted in Parsecs.

I could imaging that parallax due to our solar orbit could also account for occultation of a distant bright star by large dark star once or twice a year. Someone is bound to have looked for this amongst the vast amount of data that we now have. Spotting such variations comes under the heading of 'Transient Astronomy' and there is a lot of juice in that particular lemon - it just needs to be found amongst existing data.

The occulting object would have to be co-moving with the Sun (in 2 non-radial dimensions). The light source would have to be extremely far away or also co-moving with both the Sun and the occultor.

There should be a fleet of thousands of space telescopes looking in all directions all of the time. There should also be dedicated computers to run algorithms on all the data.

... by large dark star ...

What is this thing?

 

[sophiecentaur]

Nearby brown dwarf?

 

[ohwilleke]

Ah. Was wondering if variable star variance could be spotted with the naked eye...

It was attested to in pre-literate oral histories of Aboriginal Australians and in pre-literate oral histories in Anatolia.

 

[bob012345]

I should have checked on Wikipedia first. Thank you.

Not necessarily. It's not always accurate and there are many knowledgeable people at PF.