Ask An Astronomer

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Ask An Astronomer

Postby Lord Chrusher » 02 Feb 2012, 04:24

EDIT: WARNING THIS IS AN IMAGE HEAVY THREAD

As many of you know I am doing a PhD in astrophysics.

Prompted by this
Master Gunner wrote:I've learned far more from your posts than what I've learned in the class so far ....


I have decided to ask you for any questions you might have about astronomy and try to answer them.

A couple caveats:
I am not guaranty that I will answer all questions. Also some concepts are quite difficult to your head around.

To start things off a few big pretty pictures:

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Credit: ESO/INAF-VST/OmegaCAM. Acknowledgement: A. Grado/INAF-Capodimonte Observatory

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Credit ESO/J. Emerson/VISTA. Acknowledgment: Cambridge Astronomical Survey Unit

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Credit: ESO

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Credit: ESO
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Re: Ask An Astronomer

Postby General Michi » 02 Feb 2012, 04:41

What is the furthest known star/solar system

Can't remember the moon's name but I heard that one of Jupiter's moons (or maybe it was Saturn's) is capable of supporting life. Have there been any recent advancements in this theory?

Is there a nebula that looks like the Eye of Sauran.

What does my horoscope say about me today?
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Re: Ask An Astronomer

Postby Lord Chrusher » 02 Feb 2012, 05:28

General Michi wrote:What is the furthest known star/solar system


The furthest known planet is GOGLE-2005-BLG-390Lb which is 21 500 ly (6.6 kpc) away. It has a mass about six times that of Earth and orbits its star, GOGLE-2005-BLG-390L, once every ten years.

I have two answers to the most distant star question. We have directly observed stars out to distances beyond 50 million light years (the distance of the Virgo galaxy cluster, 16 Mpc). However we have observed the deaths of stars at much greater distances. The most distant supernova I can find in the literature (z = 2.357) would now be almost 19 billion light years away now. The light from this supernova took almost 11 billion years to reach us. The reason these two distances are not the same is that the universe is expanding.

General Michi wrote:Can't remember the moon's name but I heard that one of Jupiter's moons (or maybe it was Saturn's) is capable of supporting life. Have there been any recent advancements in this theory?


Titan, which is the only moon in the Solar System with an atmosphere. Analogous to Earth's water cycle, Titan has a methane cycle. Methane forms clouds, falls as rain, forms clouds and freezes solid on Titan - it is rather cold with an average temperature -180 C (94 K). However the presence of organic (using the chemistry definition - carbon bonded to itself) molecules has caused some to suggest life could be possible Although lakes of liquid methane were somewhat recently confirmed by Cassini mission I know of no progress on the life front.

General Michi wrote:Is there a nebula that looks like the Eye of Sauran.


The Cat's Eye Nebula looks a bit like it:
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Credit: Nordic Optical Telescope and Romano Corradi (Isaac Newton Group of Telescopes, Spain)
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Re: Ask An Astronomer

Postby Master Gunner » 02 Feb 2012, 07:11

Dark Energy. I understand that it's responsible for the accelerating expansion of the universe, but that's all I understand about it. Where does it come from, how does other work?

(I ask as my astronomy prof rambles on about spectral line analysis).
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Re: Ask An Astronomer

Postby Garfman » 02 Feb 2012, 07:38

This is prompted by Newt Gingrich's Moonbase Master plan:

Is there a good reason to go back to the moon? Is there anything we could get there that we can't here? Or should we focus on being somewhere we haven't been before?
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Re: Ask An Astronomer

Postby Drdiggit42 » 02 Feb 2012, 08:26

Do you think inter-stellar travel will be possible within my lifetime?(I am 19)

Are there any planets in the alpha centauri system that could possible support life?
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Re: Ask An Astronomer

Postby Merrymaker_Mortalis » 02 Feb 2012, 08:38

Where can I find the Andromeda galaxy in the night sky (Britain)? I thought I could see the milkyway band the othe rnight and I got excited and searched for Andromeda.

Also, when I was 6 I saw an orb in the sky with a 'ring' around it. What could that have been? I was convinced at the time it was Saturn and I have been confused ever since.
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Re: Ask An Astronomer

Postby General Michi » 02 Feb 2012, 08:44

Merrymaker_Mortalis wrote:Also, when I was 6 I saw an orb in the sky with a 'ring' around it. What could that have been? I was convinced at the time it was Saturn and I have been confused ever since.


I saw Saturn about a year and a half ago so it very well could have been it
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Re: Ask An Astronomer

Postby Merrymaker_Mortalis » 02 Feb 2012, 08:54

It was with my naked eye.
Might have been the Moon with an aura around it. However I can never be really sure as it occurred 16 odd years ago and is likely to be corrupted by memory.
Last edited by Merrymaker_Mortalis on 02 Feb 2012, 08:57, edited 1 time in total.
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Re: Ask An Astronomer

Postby Drdiggit42 » 02 Feb 2012, 08:55

I'm pretty sure I saw Saturn when I was young too. Despite light pollution and deceiving airplanes I get a pretty good view of the night sky at my house.
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Re: Ask An Astronomer

Postby plummeting_sloth » 02 Feb 2012, 09:15

Why are many scientist predicting this year to be a year of strong solar activity and what effect do you think that will have?
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Re: Ask An Astronomer

Postby Metcarfre » 02 Feb 2012, 09:49

What are some the direct and indirect applications of astronomical research being currently conducted?

(Incidentally astronomical research, particularly adaptive optics, is helping with MY research - retinal therapeutics)
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Re: Ask An Astronomer

Postby EnglishMQ » 02 Feb 2012, 09:56

The Universe is constantly expanding, what are we expanding into and what if we were to catch up?
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Re: Ask An Astronomer

Postby Rikadyn » 02 Feb 2012, 18:46

If mercury is in Virgo's 7th house...oh wait...
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Re: Ask An Astronomer

Postby Gap Filler » 03 Feb 2012, 03:38

Do you agree with the sentiment of this or this counter argument?

Speaking of Voyager, was reading about when Voyager 1 reached the heliopause the other day. How big is the Solar System by your reckoning? Has Voyager 1 left the Solar System yet?
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Re: Ask An Astronomer

Postby Lord Chrusher » 03 Feb 2012, 05:40

Master Gunner wrote:Dark Energy. I understand that it's responsible for the accelerating expansion of the universe, but that's all I understand about it. Where does it come from, how does other work?

(I ask as my astronomy prof rambles on about spectral line analysis).


But spectral line analysis is what I do!

We do not know what dark energy is or where it comes from.

About 15 years ago astronomers where measuring the expansion of the universe using supernova. A certain type of supernova (type Ia) are always the same intrinsic brightness. Since you know the apparent brightness of the supernova you can work out how far away it is. If you know how fast the supernova appears to be moving away from us you can work out how fast the universe is expanding. Since light takes time to get to us we see further back in time the further we look out in the universe, allowing us to the universe's evolution.

The supernova observations showed that the rate of the universe's expansion is increasing. However the expansion that you would expect from the observed visible and dark matter would be decreasing. Dark energy was introduced as something to fill the gap and make theory fit with observation.

The idea of dark matter is Einstein's. Einstein introduced a cosmological constant to allow for a static universe in his models. This constant has the same properties as the simplest form of dark energy. When the universe was shown to be expanding by Hubble and others Einstein withdrew the constant, calling it his greatest blunder.

The Nobel prize in physics for 2011 was awarded for the discovery of the accelerating expansion of the universe. The head of the astronomy department I am in was a member of one of the two teams that independently made the discovery so he got go as one of the official guests of the laureates to the Nobel prize ceremonies in Stockholm.


Garfman wrote:This is prompted by Newt Gingrich's Moonbase Master plan:

Is there a good reason to go back to the moon? Is there anything we could get there that we can't here? Or should we focus on being somewhere we haven't been before?


There are valid scientific reasons to return to Moon as well as reasons related to the development of space travel. However there is no economic reason to go other than tourism.

Studying the Moon up close would tell us a lot about how the Moon formed and how the Solar System formed. The far side of the Moon could be a good place to put certain types of telescopes. The Moon is close by in space terms; going to the Moon would serve as a useful dry run of say going to Mars.

There is nothing on the Moon valuable enough to be worth the insane cost of shipping it back to Earth. Any Moon base would be heavily dependant on supplies and subsidies from Earth at least for decades. The Moon is quite an inhospitable place - colonies will most likely be underground.

I think we should try and go to Mars. On the way to Mars we will likely visit the Moon again. However space flight has to become faster, safer and most importantly cheaper before we set out on such journey. Even if space flight becomes much cheaper going to Mars will be a hugely expensive task.


Drdiggit42 wrote:Do you think inter-stellar travel will be possible within my lifetime?(I am 19)

Are there any planets in the alpha centauri system that could possible support life?


Interstellar travel is possible now. However it is also impractical. To travel to the closest stars with current technology would take hundreds of years.

To make interstellar travel practical we would need to be able to travel faster than the speed of light. Under our current understanding of the laws of physics this impossible. Physics would need a radical rethink such as the one the occurred at the start of twentieth century with development of relativity and quantum theory.

Predicting this sort of is quite difficult. I am going say practical interstellar travel in our lifetimes so I can be pleasantly surprised if it does occur.


Merrymaker_Mortalis wrote:Where can I find the Andromeda galaxy in the night sky (Britain)? I thought I could see the milkyway band the othe rnight and I got excited and searched for Andromeda.


No matter where you are on Earth you will find the Andromeda Galaxy (better known to astronomers as M31) in the Andromeda constellation.

Some Googling found this:
Image
Source http://astronomerica.awardspace.com/spacewalk-m31.php

You will need a clear, Moonless in a dark site away from light pollution to see M31 with the naked eye. If you let your eyes adjust you should be able to see a faint fuzzy patch. Even looking through a decent sized telescope it will still look like a faint fuzzy blob. You need a decent telescope and a long exposure photograph to see any detail.


General Michi wrote:
Merrymaker_Mortalis wrote:Also, when I was 6 I saw an orb in the sky with a 'ring' around it. What could that have been? I was convinced at the time it was Saturn and I have been confused ever since.


I saw Saturn about a year and a half ago so it very well could have been it


Merrymaker_Mortalis wrote:It was with my naked eye.
Might have been the Moon with an aura around it. However I can never be really sure as it occurred 16 odd years ago and is likely to be corrupted by memory.


Drdiggit42 wrote:I'm pretty sure I saw Saturn when I was young too. Despite light pollution and deceiving airplanes I get a pretty good view of the night sky at my house.


Unless you have anime sized eyes you need binoculars or a telescope to see Saturn's rings. To the naked eye it appears as a point source.

With out knowing when you saw your ringed object, where in the sky you saw it, and what size the ring was as well as things how bright it was and what colour it was I can not tell you what you saw. I am almost certain that you did not see Saturn; most likely the ring you saw was an atmospheric effect.

Since Saturn can one of the brightest planets - their brightness varies as we all moving around the Sun causing distance to them to change - most people have likely seen it with realising. Unlike Andromeda, Saturn is quite spectacular through a telescope.
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Re: Ask An Astronomer

Postby Master Gunner » 03 Feb 2012, 06:27

I'm looking for a new background image for my laptop. What insanely large image do you think would make for a cool background? (Other than the Eta Carinae Nebula, that I still use on my desktop).
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Re: Ask An Astronomer

Postby Brad » 03 Feb 2012, 16:29

Placing a heavy gas in a dradle-shaped container and rapidly spinning it to create a gradient of atmospheric density and firing a laser into said gradient produces bent (smoothly defracted) light, but not a gravitational effect as a black hole does.

That doesn't seem fair. Is that fair? I want my anti-gravity moon shoes.

A real question - space elevators seem like a pretty swell idea. Space station took a lot of shuttle runs to get that stuff up there - why didn't the elevator happen? Is it another physics thing that doesn't work like it says on the box or costs silly?
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Re: Ask An Astronomer

Postby ecks » 03 Feb 2012, 17:05

Brad wrote:A real question - space elevators seem like a pretty swell idea. Space station took a lot of shuttle runs to get that stuff up there - why didn't the elevator happen? Is it another physics thing that doesn't work like it says on the box or costs silly?

I think you'll find the costs are... astronomical. http://mirrors.rit.edu/instantCSI/
Sorry.

Since I posted anyways I might as well give a less stupid answer, even though I'm not an astronomer (or a physicist for that matter).

I don't think we really know how to make thousands of KM's of nanotubes yet, and I'm not sure if any materials we can produce in huge quantities are up to the task. Also, until we are really planning on colonising the moon or mars or something, I don't think the cost/benefit numbers are going to be anywhere near reasonable even if we could make the nanotubes.
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Re: Ask An Astronomer

Postby Dutch guy » 03 Feb 2012, 18:32

As a mechanical engineer I feel compotent enough to answer that space elevator question. Like ecks just pointed out, we have no way of making a material suitable for making a space elevator.
A "cable" made from carbon nanotubes has been mentioned as a possible option, but right now there is no way of making them in any sort of length and the material is very fragile. It has tremendous strength in the longitudinal direction, but you could cut them with blunt scissors.

A currently more or less possible alternative would be a fountain tower or a launch loop. Those pose some problems with the amount of stored kinetic energy and have quite a few design challenges of their own.
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Re: Ask An Astronomer

Postby Lord Chrusher » 03 Feb 2012, 21:15

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Although really, the damage was done when the party planners took the hole punch to the elevator ribbon to hang up the sign.
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Re: Ask An Astronomer

Postby Merrymaker_Mortalis » 04 Feb 2012, 05:00

Lord Chrusher wrote:EPIC SNIP


My current memory thinks it was orangey. But my memory may have been corrupted by reading UFO sighting reports of an object similar in nature. Humans can't help but changing their story to suit an explanation, and at that time a UFO was the best explanation, better than seeing Saturn who is billions of miles away.

Best explanation I could give now would be I saw the moon during a Lunar eclipse where it was discoloured and it had some auratic effect around it creating the illusion of it appearing like Saturn.

I have always been scared to look up at the night sky due to nightmares of seeing unexplained occurances. Only recently I have changed my dread into fascination.
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Re: Ask An Astronomer

Postby Elomin Sha » 04 Feb 2012, 13:26

What's your stance on erotic Star Trek Fan Fiction?
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Re: Ask An Astronomer

Postby Lord Hosk » 04 Feb 2012, 13:52

What about the possibility of He-3 mining on the dark side of the moon which could yield significant quantities. While metals are far to expensive to bring back I have heard that as He-3 is extremely rare on earth as nuclear technology advances it takes the cost to over $2000 per L which make it viable.
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Re: Ask An Astronomer

Postby Henrietta » 04 Feb 2012, 16:16

Master Gunner wrote:I'm looking for a new background image for my laptop. What insanely large image do you think would make for a cool background? (Other than the Eta Carinae Nebula, that I still use on my desktop).

The Astronomy Picture of the Day archives run back to 1995; you should be able to find something you like.

ETA: I'm currently using this one.

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