Variable stars

You know..............the ones that tend to change their magnitudes in a matter of minutes or hours. I am wondering if there are any particularly "active" ones to watch over the course of say 3-4 hrs that has a history of changing right before your eyes.

Or does that really even happan as i interpruted it?

Paul,

If you want an easy target to hone your skills on then try observing Algol in the constellation of Perseus. Algol is a bright naked eye variable star that changes from a dim magnitude 3.4 to a bright magnitude 2.1 every 2.87 days like clockwork. Observing Algol with binoculars and a starchart is a great way of learning how to estimate its brightness changes. If you record your estimates over a period of a few weeks you should be able to plot them on a graph for fun!

Take a look at: www.skyandtelescope.com/observing/object...Minima_of_Algol.html

Phil.

You know..............the ones that tend to change their magnitudes in a matter of minutes or hours. I am wondering if there are any particularly "active" ones to watch over the course of say 3-4 hrs that has a history of changing right before your eyes.

Some Dwarf Cepheids have periods in that range. A little longer would be the RR Lyrae's at under a day.

Active is not a word I'd use with regular variables! RR Lyrae for example has a period of under a day but the magnitude change is from ~7 to ~8. So you'd need the scope and be fairly good at comparing magnitudes (easiest to do by comparing to other stars of fixed luminosity).

The shorter the period the smaller the change. Which given the processes going on makes sense - you wouldn't expect a star to stay stable if its luminosity increased by an order of magnitude every few hours.

If you want to get into this Algol is the one thats most often recommended to begin with. It's changes are visible to the naked eye over a couple of days.

Or does that really even happan as i interpruted it?

huh?

Thanks for that Phil. I know Algor due to my search for Holmes. T'is a bright one alright. The thing is i am ignorant to star Mags (i know the lower the figure......the brighter the star is).

To the untrained eye (mine) would i notice a big difference in Algor?

Is there some way (a VERY EASY WAY) to really know if it is brighter tonight then it was 2 nights ago?

A scale of some kind on which to measure its brighness.

With increased brighness...would it appear larger to the naked eye or in bins,scope?

If so how would i measure it to know?

Maybe i'm getting too far ahead of myself with variable stars?

I guess it's like any point of light in the sky. When observed at different times/conditions you kinda know if its brighter then the last time you saw it.

I wont use the moon..................cuz thats a BAD example. Mars is a good one. Its not as bright in the sky as it was say a month ago.


Which given the processes going on makes sense - you wouldn't expect a star to stay stable if its luminosity increased by an order of magnitude every few hours.

Thats what i thought. ANY star that can change Mag that quick surely is very unstable and likely to go nova on us. I think i read it in "Turn Left at Orion" that some variables do change within a matter of HOURS.

We all know that there are 24 hours in a day...............so by "HOURS" it could mean 36,48 etc. I just thought it meant SOME variables literally change in Hours (in the same 24 hr day)..................

But i was dubious about this and how i read it.

P.S.~~~"active" is a word i used to describe. It's not the term that was used.

Thanks for that Phil. I know Algor due to my search for Holmes. T'is a bright one alright. The thing is i am ignorant to star Mags (i know the lower the figure......the brighter the star is).

To the untrained eye (mine) would i notice a big difference in Algor?

Is there some way (a VERY EASY WAY) to really know if it is brighter tonight then it was 2 nights ago?

A scale of some kind on which to measure its brighness.

Yes. print out a starmap of the Perseus region with the star magnitudes labled from any planetarium program (there's an on-line one at Sky & Telescope's site) and use this to estimate the brightness of Algol. Once you know the magnitude of a near by comparison star you can then look at Algol and decide if it is brighter or dimmer. Note this down. Then pick another comparison star and repeat the process until you have pegged Algol's magnitude.

With increased brighness...would it appear larger to the naked eye or in bins,scope?

If so how would i measure it to know?

No, it won't appear any bigger - just brighter. Stars are point sources of light (effectively) and you cannot see the disk of a star unless you are using a giant professional scope... and then only just.

Maybe i'm getting too far ahead of myself with variable stars?

Definitely not! Variable star observing is fun and a great way to learn about stellar magnitudes. Give it a go - and record your observations on paper!

Phil.

Is there some way (a VERY EASY WAY) to really know if it is brighter tonight then it was 2 nights ago?

A scale of some kind on which to measure its brighness.

Magnitude. Get out a star chart and compare the brightness of your target to other stars of similar brightness that are listed. It may help to unfocus the bino's a little.

Thats what i thought. ANY star that can change Mag that quick surely is very unstable and likely to go nova on us. I think i read it in "Turn Left at Orion" that some variables do change within a matter of HOURS.

We all know that there are 24 hours in a day...............so by "HOURS" it could mean 36,48 etc. I just thought it meant SOME variables literally change in Hours (in the same 24 hr day)..................

Like I said some Dwarf Cephids have a period of less than a few hours. Very difficult to detect the variability though.

Actually they are called Delta Scuti variables not Dwarf Cepheids anymore www.aavso.org/vstar/vsots/summer04.shtml