Starship Asterisk*

I was wondering how much the universe has changed since we started taking photos of it? Are there any old pics of something in the night sky, and then a new pic of the same area? Or would they look the exact same?

Hello paynesmanor

Lots of questions - I'll answer this first one.

Has the sky changed since we first started taking photos of it. I suppose the short answer is yes but not by much in terms of the grand scheme of things.

Firstly there are "nearby" stars in our galaxy that are close enough that we can observe their motion by looking at images that are perhaps years or decades apart.

Secondly there are one off events galactic and extragalactic such as supernova/gamma ray bursts which leave their region of sky looking somewhat different before during and after the event.

Thirdly there are obviously very nearby solar system things such as the planets, asteroids, comets etc which are very easy to observe the motion of.

However distant galaxies and clusters of galaxies are not observed to change in morphology or content over such short time periods.

To discover the velocities of extragalactic and galactic objects we can look to shifts in their light spectra.

I hope that went someway to answering you question

cosmo

I guess I was looking for a picture of say those cool space columns taken by I think Hubble, kind of a before and after.

( I have seen the videos of the star wobble, and understand the basics of the universe, Umm, basicly... )..

I don't know if there is an easily accessible 'before' picture, but this (after) one, of a MACHO (massive compact halo object) is pretty cool!

So basicly scientists do not know for a fact that the universe is expanding?
I was kinda hoping that the "pillars" would be slightly different in a picture from when the hubble first saw them to how they are today..

If They cant prove it through change, then what leads them to assume?

Hi! Here is an event that shows some change.
http://hubblesite.org/gallery/album/sea ... nly&page=2
I don't know if that is the type of change your looking for but it is rather cool.
Orin

paynesmanor wrote:So basicly scientists do not know for a fact that the universe is expanding?
I was kinda hoping that the "pillars" would be slightly different in a picture from when the hubble first saw them to how they are today..

If They cant prove it through change, then what leads them to assume?

"Assume" is one thing that astronomers most certainly do NOT do, wrt the expansion of the universe!

The conclusion comes as a result of applying well-established, scientific theories to the universe as a whole, based on a vast amount of observational evidence.

One set of theories are those which computer manufacturers (etc) use, at some 'distance' from the source, to make the computer you use to communicate with fellow NSL users - quantum theory.

The other theory is General Relativity (GR), the results of yet another sensitive test of which were announced last week.

And we've already - briefly - discussed the observational evidence.

As to direct evidence - "pillars" having moved in the last decade perhaps - a quick calculation shows that this is not possible. An analogy might be large craters on the Moon - have you seen any new ones, since you first looked at the Moon? Have there been any reported during the lifetimes of your parents and grandparents?

How much has the Universe changed? What to look at to see a change?
Try looking at Mars moon Phobos. Decades ago scientists were reporting Phobos is/was so unusual it could only be explained if considered to be an artificial construct. This theory was substantiated, consider:

The First Mars Express Science Conference had four presentations specifically about the research done concerning Phobos. If you examine these presentations, which are in PDF format, you will see it stated that Phobos over the last observed 6 years has an “increased secular rate … MER Rovers see 11-12 km orbital advance … HRSC/SRC [ESA Mars Express] see 11-12 km orbital advance”, Thomas C. Duxbury et. al., JPL California Institute of Technology, 11_Duxbury.pdf.

“Phobos ahead of its predicted orbital position by approx. 1 radius, Bell Duxbury et al., Nature”… “Phobos estimated to be off its normal (JPL ephemeris) orbit by 6s (approx. 12 km) along-track; across-track position errors <1 km”, J. Oberst et al., and the HRSC Co-Investigation Team, 12_Phobos_Oberst.pdf.

In the PDF presentation by John Murray et al., the images of Phobos specifically the leading edge of Phobos does not show the leading edge crater chains to be larger than the trailing edge crater chains so their theory that Phobos flew through Mars debris or flew through ejecta debris is not valid or was not validated. But they did achieve to acquire some better imaging of the leading edge of Phobos.

What you might find even more interesting is the last presentation PDF by Severine Perrier et al., SPICAM Team on the Mars Express. They worked on the UV absorption or reflectance of Phobos and Deimos, the albedo of those two moons. What they found was a repetitive reading in the 220 um, “significant absorption feature around 220 um, similar to interstellar extinction feature … could be caused by the presence on Phobos of organic material … not compatible with the UV silicate signature (around 260 um) … similar to the extinction feature observed in the Interstellar Medium of 217.5 um” To quote them even more “Nature of ISM absorbing material? Possible organic material”.

The First Mars Express Science Conference Presentations, http://sci.esa.int/science-e/www/object ... ctid=36537

The Mars Express (JPL) MRSC/SRC investigative teams conclusioned that Phobos is out of predicted position but amazingly Phobos must have some organic material.

I find this subject interesting as well.

Here's an image of a Saggitarius star cloud I constructed from two photographic plates, where the blue plate was taken almost 40 years before the red plate (the data is from the STScI Digitized Sky Survey, or DSS, from 1958 and 1996). You can see that at least one star has moved perceptibly. Many stars have such "proper motion", which means they're moving measurably against the cosmic background.

Click on the image to see a high resolution version.



Supernova SN1987A is another example of our actually seeing things happen on an interplanetary scale since the star exploded in 1987. Check here:



-Noel

in "this star has moved" picture, you can see blue dot at about ~60° to the left from marked one (relative to right bottom corner), but no red one. did that star disappeared?

Good eye, makc! It's likely it was a plate defect or dirt on the plate during the scan. I just looked closely at the original blue plate data and found this apparition, which on close examination doesn't look at all like the surrounding stars. Such defects are common on these plates. I often find threads and dust motes that look a lot like this.



-Noel

you say dust, and agent Molder says "ufo sighting". now, who does one trust?