Why do we see distant stars?

Originally posted by Im a Marty
I think I read that the stars light is amplified by the atmosphere, When in space - or on the moon, you cannot see the stars that we see here.

Also - those stars are long gone!

I'm not going to get into the first part of your post, considering I'm exhausted from trying to convince gary-whats-his-name that a photon does not need atmosphere to be seen (considering the Apollo astronauts used an optical sextant to navigate by star).

The second part of your post though...
Why would you say they are long gone?

We know stars live for billions of years (such as our sun, which has been around for almost 5 billion years), and the stars we see in the sky are only a few hundred to several thousand light years away. Why would they be gone, if we are seeing them as they were only a couple of thousand years ago?

reply to post by AllIsOne


OP you have to understand, the "the grass is greener on the other side" concept need to be said here.

If none of the stars are blocked, our entire night sky will be white or rather filled with stars you will barely see any dark areas, but we actually see the opposite, mostly dark areas and some stars.

So yeah, we don't see most of the stars, the ones we see are the lucky ones that did not get blocked(most of the time), they probably do flicker, but we don't stare at them 24/7.

Considering we're seeing light from many many years ago, perhaps it has been blocked out, but we won't see it for another 100 years or so.. or perhaps you already missed it.

Originally posted by AllIsOne
How come we can see that star without any major flickering? Yet, we see that star continuously shinning at night?

We can see stars at night because there are no clouds in the sky at the time of viewing

reply to post by inverslyproportional

I think my largest thing about what "we know" about astronomy ..and I know I will upset the purists with this .. but we're guessing. 90% guessing. They guess frequently and turn out to be wrong MORE often than they are right about places right here on Earth. The moon was a source of endless discovery and still is, for that matter.....where most of those discoveries come at the contradiction and putting down of a previous theory at least someone stood completely behind up to that point.

Now they sit and confidently declare within small %'s of error, how far away things are that are unthinkably far away to begin with (if the guesswork has basis). I was hoping Voyager might have reported back something more interesting on clearing the sphere, but apparently not. Interesting to note, much of the heliosphere was ALSO said to be new, different and unexpected. Indeed... That's just a few feet away from Earth in relative distances and comparisons ....and we knew little to nothing of critical aspects of it.

So... I'm skeptical of all the "science" for what is radically beyond any form of direct observation with the ability to measure beyond literal assumption built on presumption. I know it's all mankind has until we leave this planet, so we have to work with something .... but it's interesting sometimes to see how much people have come to accept the mid-stages of a scientific process as settled or accepted fact.

My imagination and I are happy with considering the gaps ...enormous gaps...left in the current knowledge of what is out beyond our Solar System. After all, there are gaps enough to keep Man busy for centuries more.

Originally posted by AllIsOne
I.e. Hipparcos 5926 in Cassiopeia is 16,308 light-years away. One light year is 9.4607 × 10*12 km. How come we can see that star without any major flickering? Seeing a star means that the light traveled an almost unimaginable distance without being absorbed, or blocked along the way. I feel the photons should have hit something along the way, i.e. planets, gasses, suns, space debris, etc.. The universe is full of moving objects. Yet, we see that star continuously shinning at night?

The theory of distance and time in the universe is probably wrong, like a bunch of other theories. We know nothing about the true nature of the universe. Keep an open mind, there is constantly new theories coming up.

The light you see is actually very old. It takes quite some time for the light to reach us. Some light we see may come from stars that no longer exist.

reply to post by Wrabbit2000

I think my largest thing about what "we know" about astronomy ..and I know I will upset the purists with this .. but we're guessing. 90% guessing.

I agree with you there Wrabbit. Too many assumptions and circular logic, the Cosmic Distance Ladder being the biggie. Star colours are not to be trusted as part of any models if the colour of our own Sun is so contentious. Taking a picture of the Sun from space seems like it is not as simple it seems, and I still wonder why the pinhole projection that Don Pettit was supposed to do from the ISS was never done, or has not been tried again. An ND filtered shot is not mentioned, but if the ND filter reduces all wavelengths equally accross the spectrum, then I would have thought it a true colour representation.

The colour of the Sun from Earth:
www.science20.com...

ND filtered shot from Earth:
mcalisterium.wordpress.com...

So with the same setup from the ISS the Sun should appear white? Why haven't they tried it to find out? It would need to be an ISS mid-day shot and not the Sunset/Sunrise images which are all we ever see from the ISS, to be a valid comparison.

And how about using one of the 4 colour video cameras on the CanadArm2 on the ISS to show us a video of the Moon, which I can do easily from home, but has not even been tried AFAIK from the ISS. Does that make any sense? They are too busy, we can see it from Earth, why bother from space, the cameras weren't designed to do that, pick your favorite excuse. Total nonsense, there is no excuse except that they CAN NOT do it.

@Ove38

Keep an open mind, there is constantly new theories coming up.

Good advice I'd say.

reply to post by Wrabbit2000


Wrabbit, I did not imply we know everything, nor mean to if you took it that way.

I was simply trying state things we do know to be facts. As we have tested and applied the knowledge in the real world ie. The probes that have passed harmlessly turough these regions, without fear of anything hitting anything.

I am far too smart and knowledgeable to make an assertion along the lines of us knowing everything about anything, as we are but infants, newly born, and still looking around in awe trying to make sense of what we are seeing.

A poster to the bottom of this page has made a very good arguement about said ignorance of the cosmos. Though I will address him individually.

Good day, keep on your toes, it is april first.

Sorry double post

Originally posted by litterbaux
reply to post by AllIsOne

 

I don't have an answer for your question, I just wanted to make a reply of what a great question this is. It seems very hard to believe that a constant stream of light could make it to earth without something either bending it or getting in the way.

And what should that be?

The stars we see are all IN OUR GALAXY, so there is not really much in between. Space is a vacuum. What else is there to explain? Yes, space is vast, big...and light can travel 1000s or 100000s or light years undisturbed, that's what space is. What should there be "in between"? UFOs? Clouds?

Oh dear - It's the return of the "we-don't-know-everything-therefore-we-don't-know-anything" argument.



I wonder if it is a coping mechanism for people who are intimidated by others who possess more knowledge and education than themselves? I prefer to give people the benefit of the doubt...

For the genuinely curious (and ATS is full of these), the coolest question in all of science is, "How do we know what we know?" One of the reasons I like astronomy so much (as opposed to - say - neuroscience, which is no-doubt a fascinating field, but is completely over my head - no pun intended) is that the answers are understandable to a non-college graduate (such as myself) and useful discoveries and contributions are made daily (or - more correctly - nightly) by talented amateurs (like ngchunter and others here on ATS).

Read How do astronomers measure the distances to galaxies... and find out why this woman is one of the most important people in the history of astronomy - right up there with Hipparchus, Tycho Brahe and Edwin Hubble.



For further study, read Blind Watchers of the Sky. This fun and engaging book tells you about the history of how-we-know-what-we-know in astronomy, and how this hard-won knowledge was gained over centuries of hard work. We don't know everything, but if you think that what we do know comes from "just guessing", you are WRONG. Find out the real story!

Originally posted by AllIsOne
I.e. Hipparcos 5926 in Cassiopeia is 16,308 light-years away. One light year is 9.4607 × 10*12 km. How come we can see that star without any major flickering? Seeing a star means that the light traveled an almost unimaginable distance without being absorbed, or blocked along the way. I feel the photons should have hit something along the way, i.e. planets, gasses, suns, space debris, etc.. The universe is full of moving objects. Yet, we see that star continuously shinning at night?

Photons have no mass. You figure out the rest.

reply to post by GaryN


You are partly right and partly wrong.

Yes itnis flawed to measure a stars color to determine if it is coming or going relative to us. As just because hit is red doesn't mean it is moving away, it could just as easilymean it is simply older and reder in color, or bluer because it is newer, or moving towards us.

But to learn more we must have a standard of measure just to judge distance, the red/blue shift method thoughflawed is our best curent method, not perfect, but better than just saying ya there stuf up there.

We also have a distance measure to check these guesses, which have proved very accurate, thus we have learned to use more than one method to determine distances.

It is called a standard candle. It based on the ract right here on earth I can guess your distance quite accurately, with nothing but a light source of known power.

A type 1A supernova is this standard candle, it always explodes with the exact same strength and luminosity. So it is possible check our assumptions against a known quantity, to double check and if necessary revise our figures.

I will not comment on your other assertions, as I am not familiar with some of the material, and would prefer to study it before I make anystatements.

I will reply further after I have had a chance to further rea up on the material. Very interesting stuff though.

reply to post by AllIsOne

Yet, we see that star continuously shinning at night?

Hipparcos 5926 (V762) in Cassiopeia is 16,308 light-years away but is magnitude 5.84.

Link

V762 lies at the naked eye limit of 6th magnitude. Most of us will probably never see it from our light-polluted towns and cities.

You have never, ever, seen this star unless you are an astronomer and are studying cassiopea through a telescope.
On a mountaintop.

reply to post by AllIsOne

Every atom blinks in and out of existence too-light would be able to get through. And there isn't really that much space debris outside of most solar systems where collisions occur only after planets and moons have formed and are attracted to a gravitational pull during the forming process, or other circumstances.

But things do indeed pass in front of stars, and it IS detectable by advanced equipment. The things that pass in front are just not big enough to block the star out completely.

Think about the Earth. The Earth is 1/1000 of the size of the sun, and 93 million miles away. How much of the sun do you think we block out?

Originally posted by inverslyproportional
reply to post by Wrabbit2000

 

I was simply trying state things we do know to be facts. As we have tested and applied the knowledge in the real world ie. The probes that have passed harmlessly turough these regions, without fear of anything hitting anything.

What probes have left our Solar System to pass through any regions that aren't essentially in our own tiny backyard? Voyager I just left the sphere, as I understand it and it's the first (known) human object to ever leave our own home turf. So.....everything beyond that is still based on observation, assumption based upon what that shows, and presumption based only upon what has been observed within our own solar system, right?

* BTW .. Nothing is personal. I hope it's not seen that way. I reply to topics, not people ..even if it is a bit energetic regarding the topic at times.

Originally posted by AllIsOne

Originally posted by Parksie
Stars are massive. To block light from a star, space debris would have to be like the same size as the sun.

Really? In order to block our sun from view, your finger needs to be the size of the sun?

edit on 1-4-2013 by AllIsOne because: (no reason given)

Dude, if you block the sun with your finger does it mean the rest of the planet is in complete darkness?

Originally posted by ZeroReady
reply to post by AllIsOne

 

Because massive objects curve space and actually do bend light (or the medium through which it travels) so starlight does go around big objects.

Smaller objects, like the example a finger blocking out the sun, simply aren't large enough or stationary enough to block the starlight in a way that causes it to flicker visibly off and on.

Someone beat me to it. Star for you ZeroReady. Light bends AROUND massive objects. This is called Gravitational Lensing


Additionally, there is a lot of empty space between objects out there. Even though when you look at, for example, the Milky Way from a distance, it APPEARS that it's very crowded, that's only because you are shrinking the system down so much.