How can the telescopes take photos of distant galaxies?

[Prog47]

So how can the photos of distant galaxies have no nearer stars in front of them? Or photos of nebulae?
I feel like there are so many stars.that it would be impossible to take a photo of a distant object without a star in front of the photo blocking the way. Or is it luck that there are no stars between here and the photos they took?
What about photos of the deep space? Why is there no close star that is too close and takes up the shot in front of the millions of stars in the photo?

 

[1oldman2]

The simple answer is space is really really really big compared to the matter it contains, a quick search of sites such as http://astro.physics.uiowa.edu/~www/research/interstellar_medium.html and http://www.its.caltech.edu/~kamion/Ay126/SterlLectures.pdf for example will give some perspective.

 

[Drakkith]

So how can the photos of distant galaxies have no nearer stars in front of them? Or photos of nebulae?

They often do. But individual stars are essentially impossible to see unless they are VERY large and VERY bright. Such stars only form a small percentage of the stars in the Milky Way. Nebulas are also very difficult to see unless they are very close or very large and bright.

In addition, stars are really, really small compared to the ginormous distance between them. At a distance of one light year, a star with the same diameter as the Sun is only 0.0085 degrees across. At 4 light years, just about the distance to the nearest star, it would only be 0.002 degrees across. The chances that a ray of light leaves a source and impacts a star is extremely small.

 

[Chronos]

Most observable galaxies lay outside the galactic plane where most stars in the MW reside. Intergalactic space is mostly devoid of stars.

 

[davenn]

So how can the photos of distant galaxies have no nearer stars in front of them? Or photos of nebulae?

you are working from a very poor assumption

They often do

indeed ... VERY often do ... there would be very few photos of objects internal or external to
the Milky Way that don't show foreground stars

But individual stars are essentially impossible to see unless they are VERY large and VERY bright.

sorry, have to strongly disagree with that... they will be of all sorts of sizes and luminosities eg

ALL the stars in that image ( other than a tiny few very bright stars in that "larger galaxy) are foreground stars that are within the Milky WayDave

 

[Drakkith]

sorry, have to strongly disagree with that... they will be of all sorts of sizes and luminosities eg

I'll tentatively agree and try to remember to look up more info on this.

 

[davenn]

I can post dozens of images if I was in the mood ... here's a nebula with foreground stars

and a couple of galaxies and nebulosity

etc etc

dozens of related images here ...

http://www.bing.com/images/search?q=galaxy+or+nebula+images+with+foreground+stars&FORM=HDRSC2Dave