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Wrong order.
Jun 14, 2001

You'll be better off reading the second of the following journal enteries first.

(No replies)

Planets around A type stars. Update.
May 27, 2001

OK, so a binary planet system orbiting an A type star yes?

Well, initially I was thinking along the lines of some weird individual stars orbit in order to have strange seasons of normal length, however I concluded that this wouldn't work and would be unlikely. Then I thought about Pluto and considered Earth and came up with this. Basically if the Moon was the same size as the earth (and not on a 5 degree tilt) we would orbit a common canter of gravity in the very middle of our orbit. We may orbit this canter say every 27 days the same as we do now. However our orbit would take us closer to the sun at one point, call it point S, and further at the opposite point, point W. Of course in an Earth Moon orbit we would hardly be able to measure the changes because that distance covered would be negligible compared to an AU.

So now we increase the scale, plop in a type a star, move our orbit much further out to a distance in the correct temperature region (could be called the life orbit) for the star. Then our year becomes longer, and seasons just huge as you noted. In steps my planet with a companion planet of the same mass. Quite large things, but not gaseous or with a unbelievable gravity, just big enough. These two planets orbit each other at a distance of something like 1/2 AU, so that their orbital period of their CG is about two Eyears (Earth years) or so. || Here I am not sure as to the nature of binary systems and whether keplars laws apply to dictate the period of binary systems. || So these two companion planets are orbiting each other and their common CG is orbiting the star in 8 Eyears as you gave. If they are orbiting each other every two every Eyears, call this a Y*, then every year one planet passes point S four times and W four times. The Y* will last 2 Eyears, and each season 6 months or so, not too much problem for plants on the surface or for people to come with.

This season could then introduce fantastic new forms of animal behaviour, notably that Humans could migrate every winter to the other planet and have another summer again!. Space stations can be mounted on the CG, where they would no move, allowing for better launches to other planets. The two planets would allow for easy measurements of parallax as they have an inbuilt separation rather then having to wit to go round our orbit. 2 people could measure a stars position one night and compare data and work out accurate instantaneous parallax. Space probes could use the sling shot effect to great use, gaining gravity assists from each planet many time in a short period of time and be launched into deep space with ease.

In fact I would just love to live there, having two planets to manage and explore, with the ease of developing space technologies (it's like having a secluded patch of free space in between!), and the beautiful sight of a crescent sister planet rising after the sun sets, with your friends on it as well as on your planet. Just stunning. wouldn't be surprised if these aliens would be the first to developed and travel through space.

Hope that make sense and explains my weird minds witterings, so sorry it took me so long. What is this book that you are writing like then? Will it be published? Also what is your background in astronomy?

Have fun working out what I said, and ask if you need clarification, I will endeavour reply sooner.

Cheers and good luck,

Nick
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This was my reply.
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Dear Nick,

This is great. I can understand it. I'll let you know if I do have any problems. This could work. The book well most times when I'm writing a book I tell people about it but this book is different in two ways to my other books. The first is it is the first book that I write to be written in first person narrative (I said, I picked up instead of he said, he picked up) and also it really is going to be a work of art I hope and is very well worked out. I don't want to tell people too much and spoil the surprise. So far what I can tell you is that to create these aliens I have to design the aliens to be partly humanoid to fit the story however I'll try and thing of physical differences. Also I need to create a new language, alphabet, religion, history and things like that. This is why it so well thought out.

You also mentioned how beautiful it would be to see the sister planet rise, I'm thinking of putting the planet in the globular cluster where the nearest planets are only light days away and even without a sister planet the sky would be a bright as if there were a full moon every night. How do you feel about seeing that in the sky. If the stars are only light days away then for these people in the future traveling to the nearest star would be a possibility that we can't consider without an interstellar ram-scoop.
One other thing on bright night skies, how would you feel if tomorrow Betelgeuse went supernova? It would turn night into day, be visible even during the day and it 'points' would stretch from horizon to horizon (you'd also have tremendous light pollution but from the other direction to the one were signing the petition for). I have to say that although there is the issue of light pollution it's something that outweighs the disadvantage since the last supernova to be seen from Earth like that (in our Galaxy) was Gaimnga (spelling?) in prehistoric times and it really is an experience to 'write home about' for want of a better phrase.

One last thing, would the sister planet have any gravitational forces against the other planet? It's just a thought and would it be possible for the planet to have any moons (ideally I'd like three (think of how light up the night sky would be then)).

Many thanks again.

Richard.
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This was my next reply.
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Dear Nick,

I was going to write in the week end but I was working and didn't get round to it. I'm afraid I have a bit of bad news. When I received you solution to my problem on planets round A type stars I was thrilled that there WAS a solution and to get it. However you did say you were unsure about Keplars law so I thought I better check it out.

Last Monday I phoned the Science Line (you may want to put their number on the H2G2 AS page. It is a free phone number and is 0808 800 4000. They are open between the hours of 4:30 pm and 6:30 pm on weekdays) and asked them about you solution. They told me to phone back on Wednesday when someone better suited to answer the question was in. When I did they told me there were a few problems with planets around A type stars.

The first was one for me to worry about. If was that A type stars were very young and there may not be time for the planet to form and develop intelligent life. They may be time for it to develop intelligent life and that could be done on a planet that formed around another star and escaped it's pull like Pluto will do in 9,000 million years and then was caught by this planet like the moon may have been done to the Earth or like the Red Star was done in Anne McCaffery's Chronicles of Pern.

The second was in your solution. The idea of a second planet was not too good. They weren’t sure if the orbit would be stable and the closeness of the planet did mean there could be server tidal forces. Also it could pull it out of the life zone a one point or another scorching it, or sending it into an ice age. The main problem though was that it didn't solve the problem. The seasons of the Earth a determined by the tilt or the Earth and are nothing to do with the distance from the star. In fact the Earth is closer to the Sun during the Northern Hemisphere's winter than in the summer. I know that for the tilt the planet needs a moon. Also the Earth's axis spins and so rotates the star charts every several thousand years. Maybe with three moons it could change the tilt in a MUCH quicker time and to a MUCH greater degree. Would that work?

I'm sorry your solution didn't work. Both for you and for me. If you have any other idea's let me know. I'm beginning to think I'll have to chose a K type star. I'd like to use an A type star if possible though. Thanks for trying and Don't Panic (that's for me to do).

Richard.

(No replies)

Planets around A type stars.
Mar 25, 2001

I'm writeing a book about a planet round an A type star and have run into a small problem. I've put question into the H2G2 AS and into the H2G2 AS conversation forum but I haven't had much response at the moment so I thought I put a journel entery here. Any assistance is greatly appriciated (spelling?) and will be rewarded as long as a contact address is left.
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This is what have been discussed so far. Any comments on any part that is helpful will be great.
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I'm writing a book about a planet around an A type star like Sirius. However for the planet to be round the life zone of this star it has to be 474,208,814.8 miles from the star. This is because Sirius is a suitable A type star to model my A type star on and it's 26 brighter, hotter and bigger than the sun and that means that the planet has to be 5.099019514 times further than it would be from the Sun (93,000,000). This means that the length of a year on this planet would be quite long. If the planet were four time further away the year would be eight years with seasons being two years long. However this creates a problem in the book because I ideally need the year to be a similar length to an Earth year. I know if I'd chosen a G type
star there wouldn't have been a problem.

I was thinking of having the planet move round the star faster that would mean if it was moving fast enough the year could be a similar length but the speed a planet moves round a star relative to it's distance from the star is a universal constant like the speed of light. This also wouldn't be possible since the further a planet is from a star the slower it moves. If it moved faster then there is a chance of it escaping the star gravity a spinning of into space as a rouge planet like Pluto will be in about 9,000 years. This means I need to think of other ideas and see if they will work. At the moment the only thing I managed to come up with is that the star is a binary
star with one or more companion stars and that with the orbit it could take round the other stars the year could be longer but it could have seasons lasting three months that run in the order of Winter, Spring, Summer, Autumn and follows this pattern a sure as the Earth does. It would means that there would be several Winters a year and the same for the other seasons but this wouldn't be a problem.
I was wondering if you tell me what you think of that idea an suggest any others that would have same solution.
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I got this reply.
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Why not slow their perception of time down, so that the inhabitants
experience life as if a rotation around Sirius were one year, even
though it is actually 8 years of Earth time? This is similar in some
ways to the perceived notion that insects experience the passage of
time differently to humans, manifested in our difficulty at swatting
or catching flies...

Also Ian M Banks proposed the nice idea of an Orbital, which is an
artificial environment that completely rings a star at the right
distance, and which revolves at a rate that gives equal night and
day. Given sufficient technology and intelligence of the native
population, the space environment would not need to be natural, and
could perhaps be customised perfectly to their needs.

CR
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This was my reply.
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Thanks for the suggestion. I had thought of that and that would have been okay apart from the fact that I want a person from Earth to visit the planet however I suppose his perception of time could be slowed down as well. As with the suggestion of the orbital, the technology for that is much to advanced for the level opf technology that the people are as since they are still hunter's and gatherers.
However I may use the first idea so thanks for it. I also thought that maybe if there is a binary system them the planet may be fried but if there was a close orbit to a White Dwarf like Sirius B then that may solve the problem or the planet could be 93,000,000 miles from the star and have a thick dusk cloud between it and the planet that absobes much of the suns heat, light and radiation. What do you think about those ideas? Thanks again.
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I got this reply.
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Humans evolved with a year that was shorter than ours, 22 or 23 hours I think (proved by people being put in a cave and reverting to a 22 hour day) so there is no reason at all for why the new planet needs to have an Earth length day or year. As live begins to evolve the length of day will naturally be programed into the life system so it's natural day will be 35 hours and it's year 400 days etc. I
agree that there needs to be the correct distance range for the solar radiation to be safe but enough to allow life, for us being 93 million miles

>or the planet could be 93,000,000 miles from the star and
>have a thick dusk cloud between it and the planet that
>absobes much of the suns heat, light and radiation.

Don't really like this suggestion, why would there be this dust cloud? If it were a failed planet like our asteroid belt then there would be large rocks and not dust, and this wouldn't absorb nearly enough light. If it is dust then this would be enveloped either into itself to creat said astroids or collapse towards the star. I'm guessing the idea of 93 M miles is just to give the earth type days and years, yes? It shouldn't need the same conditions as Earth
as they wont be earth people who evolved there, they probably won't have elbows for a start. If a human goes there then were going to have to cope with the shock of living with aliens so never mind the longer days (the aliens will also have to cope with us!).

>year could be longer but it could have seasons
>lasting three months that run in the order of Winter,
>Spring, Summer, Autumn and follows this pattern a sure as
>the Earth does. It would means that there would be several
>Winters a year and the same for the other seasons but this
>wouldn't be a problem.

This couldn't work, I don't think as the planet would need a slight tit and the axis of rotation would need to progress round a number of times each year.

If you /really/ want to have an Earth like environmet I guess you could have a highly elliptical orbit, which would mean that the close approaches would constitute 2 summers and an axis tilt POINTING PARRALELL TO THE CLOSE APPROACH PATH so there would be 2 other summers at the extreams where the tilt caused the summer like on Earth. I guess this has problems as with an elliptical orbit of such a degree the loci of Sirrus would be close to one apex, so the plannet would wave an extreamly short hot period and a long cool period. Get a point where the close approaches gives a summer at the equinoxes and then a large tilt gives a summer again this would give 2 sumemrs per year, for each hemisphere.

OR:
have a binary planet system, with quite a long period, this would mean that there could be a summer every binary orbit, for both planets and there could be enough orbits per long year as you see fit.


OR: (and this is an od one)
So we have a distant plannet in a region to allow life, but with a long year. OK, so if the axis of rotation is somehow in line with it's orbit path... no that won't give a nice length day. Hmm...

Hope that makes some sence.
Yeliab, 32373
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This was my reply.
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The length of day with my problem it not an issue since it isn't related to the planet's distance from the star. However the problem isn't about the visitor noticing anything strange about the year either. Also there's no problem with him seeing aliens. He's on another planet so he has to prepared for that and he may have already seen other aliens (if they're anything like you get in Star Trek they wont be a problem anyway).

To do with the idea of the dust cloud, that was to have Earth length years that was why I suggested 93,000,000 miles. However I was reading a book about terraforming Venus and a dust cloud was suggested to combat Venus being only 67,000,000 miles from the Sun (therefore if it can work for Venus it should work for me, shouldn't it?)

I like the idea of the binary system you mentioned.

>have a binary planet system, with quite a long period,
>this would mean that there could be a summer every binary
>orbit, for both planets and there could be enough orbits
>per long year as you see fit.

If you could tell me more about it that would be great.

I hope you don't think I'm criticizing what you said. I'm just mentioning my thoughts on it. If you can think of any more ideas that would be great but I'm interested on the binary idea and it may work.

The real thing I needs if four seasons in the order of Winter, Spring, Summer and Autumn that last about three Earth months even if the sequence is repeated several times a year. I really do need a solution because this is to do with the central theme of the book.

Any suggestion you have would be great. I may have to have a G type star but I'd like to leave that as a last option. Thanks for any help.

Richard.
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If anyone can help me from this point on. Or has any other ideas please let me know. Thanks.

(3 replies, Latest reply: Apr 15, 2001)

Help!
Jun 27, 2000

Week nine.

I decided that I should contribute to the guide since I had done nothing and looked around for a subject and found it wasn't on the guide so I researched it for two months and found a lot of information. I was about to submit it when I found that if I write it in HTML I can include pictures and I did come across some pictures in my reserach and I can include an equal balance of text and graphics which makes things eaiser to read.

I would like to include pictures but I don't know how to write in HTML so if anyone sees this and can help or can tell me where to go to help I would be very greatful. I just wan't to include some pictures with plain text (*.txt).

Thank you anyone who can help me. I SOMETIMES think about rewards!

P.S. Sorry about the spilling.

(1 reply, Latest reply: Oct 25, 2000)

Day one.
Apr 20, 2000

After a lot of seraching of the space lanes I finally managed to get a ship that was going to the western spiral arm of the Galaxy. I found a small unregarded blue / green planet and decided to have a look round.
I didn't realise how backward it was...that was until I realised that it had the Hitch-Hiker's Guide to the Galaxy. Since I'm a field researcher for the guide I decided to jote down what I didn while I was on the planet.
I have to say I was surprised to find the planet since I heard that it was destroyed by the Vogons over ten years ago but then information can be widly inaccurate.

On the first day I decided to ask if anyone would like to share ideas on the Hitch-Hiker's Guide to the Galaxy computer game.

(No replies)