Starship Asterisk*

JuanAustin wrote:Just curious, how long would it take using conventional technology to travel perpendicular to the plane of our galaxy before a reasonably good view could be had to confirm that the milky way is a barred galaxy?
Conversely, if we had a starship that could erase the limitations of speed and time, how far would one have to go to confirm the same?

geckzilla wrote:'Cause they aren't crazy enough looking.

Star Geezer wrote:How do we know that these two galaxies have not already collided and are now emerging into their post collision states?

Ann wrote:Another famous double star is Mizar and Alcor in the Big Dipper.

jambo wrote:
What is the star with its apparent mirror image immediately below it, located about
halfway between the core of the lower galaxy and the right edge of the picture?

jambo wrote:What is the star with its apparent mirror image immediately below it, located about halfway between the core of the lower galaxy and the right edge of the picture?

Epsilon Lyrae.
Source: http://www.themcdonalds.net/richard/ind ... ilon_Lyrae

jmcgericault wrote:Is there any evidence of gravitational lensing in this photograph? I see lots of other background galaxies in the photo, some even directly behind Arp 271 itself. Wouldn't the gravity of these two massive galaxies in Arp 271 distort the light coming from these background galaxies?

jmcgericault wrote:
Is there any evidence of gravitational lensing in this photograph? I see lots of other background galaxies in the photo, some even directly behind Arp 271 itself. Wouldn't the gravity of these two massive galaxies in Arp 271 distort the light coming from these background galaxies?

http://en.wikipedia.org/wiki/Abell_1689 wrote:
<<Abell 1689 is a galaxy cluster in the constellation Virgo nearly 2.2 billion light years away. The lensing zone itself is 2 million light years across. It is one of the biggest and most massive galaxy clusters known and acts as a gravitational lens, distorting the images of galaxies that lie behind it. It has the largest system of gravitational arcs ever found.>>

http://en.wikipedia.org/wiki/Arp_271 wrote:
<<Arp 271 is a pair of similarly sized interacting spiral galaxies, NGC 5426 and NGC 5427. Located 90 million light-years away, the Arp 271 pair is about 130,000 light-years across. It was originally discovered in 1785 by William Herschel.>>

K1NS wrote:
Think about the billions of astronomers, on the hundreds of billions of planets orbiting stars in ARP 271. The sky they see must be beautiful, with another nearby galaxy crossing the sky behind the "milky way" of their own galaxy.

I wonder if they realize that their galaxies are passing through each other?

• Are some of them radio astronomers?

http://en.wikipedia.org/wiki/Hydrogen_line wrote:

[b][color=#CF00CF]A scan of our Milky Way galaxy at 21 cm shows that the distribution of neutral hydrogen is concentrated in the spiral arms. The Sun is marked as the yellow arrow, Galactic center is a blue dot. Notice how there is a cone of avoidance behind the Galactic center due to confusion in the HI signal.[/color][/b]

---

<<The hydrogen line, 21 centimeter line or HI line refers to the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms. This electromagnetic radiation is at the precise frequency of 1420.40575177 MHz, which is equivalent to the vacuum wavelength of 21.10611405413 cm in free space. This wavelength or frequency falls within the microwave radio region of the electromagnetic spectrum, and it is observed frequently in radio astronomy, since those radio waves can penetrate the large clouds of interstellar cosmic dust that are opaque to visible light.

During the 1930s, it was noticed that there was a radio 'hiss' that varied on a daily cycle and appeared to be extraterrestrial in origin. After initial suggestions that this was due to the Sun, it was observed that the radio waves seemed to be coming from the centre of the Galaxy. These discoveries were published in 1940 and were seen by Dutch Professor J.H. Oort who knew that significant advances could be made in astronomy if there were emission lines in the radio part of the spectrum. He referred this to Dr Hendrik van de Hulst who, in 1944, predicted that neutral hydrogen could produce radiation at a frequency of 1420.4058 MHz due to two closely spaced energy levels in the ground state of the hydrogen atom.

The 21 cm line (1420.4 MHz) was first detected in 1951 by Ewen and Purcell at Harvard University, and published after their data was corroborated by Dutch astronomers Muller and Oort, and by Christiansen and Hindman in Australia. After 1952 the first maps of the neutral hydrogen in the Galaxy were made and revealed, for the first time, the spiral structure of the Milky Way. Assuming that the hydrogen atoms are uniformly distributed throughout the galaxy, each line of sight through the galaxy will reveal a hydrogen line. The only difference between each of these lines is the Doppler shift that each of these lines has. Hence, one can calculate the relative speed of each arm of our galaxy. The rotation curve of our galaxy has also been calculated using the 21-cm hydrogen line. It is then possible to use the plot of the rotation curve and the velocity to determine the distance to a certain point within the galaxy.>>

K1NS wrote:Think about the billions of astronomers, on the hundreds of billions of planets orbiting stars in ARP 271. The sky they see must be beautiful, with another nearby galaxy crossing the sky behind the "milky way" of their own galaxy. I wonder if they realize that their galaxies are passing through each other?

Ann wrote:It is important to remember that only nearby galaxies can be blueshifted. For more distant galaxies, the expansion of the universe always makes the galaxies move away from us.

bayareajohn wrote:So... if we know the distance to a galaxy from the red shift because the universe is expanding, and the more red shift, the farther way a galaxy is.... if a galaxy is coming toward us, like Andromeda is supposed to be, would there not be a BLUE shift instead of RED, and consequently we could not estimate distance?

bayareajohn wrote:So... if we know the distance to a galaxy from the red shift because the universe is expanding, and the more red shift, the farther way a galaxy is.... if a galaxy is coming toward us, like Andromeda is supposed to be, would there not be a BLUE shift instead of RED, and consequently we could not estimate distance?