Sunday, November 10, 2013

Island universe*

NGC891 galaxy looks as we think Milky Way would look like when viewed edge-on. In fact both galaxies are considered very similar in terms of luminosity and size. The galaxy is in the constellation Andromeda and was discovered by Caroline Herschel in 1784. It is a part of NGC1023 galaxy group and also a part of Local Supercluster. Galaxy is about 27 million light years away and its apparent magnitude is 10.8, so it can be just spotted in 4 inch telescope as a light smudge. To see dust line across galaxy one needs much larger instrument, at least 12-14 inches aperture. High resolution images of this galaxy show unusual filamentary patterns in the dusty disk (barely visible in my image). Scientists presume that supernova explosions can cause the dust to be thrown out of the galactic disk to the halo.


NGC891 is not the only galaxy in this picture - there are dozens of them. In the lower left part there is Abell 347 galaxy cluster. The cluster is about 200 million light years away and seven of them are brighter than 14 mag, so they are available for visual observers that have 10" or larger scope. The Abell 347 galaxy cluster is a part of one of the largest structures in the universe - the Perseus-Pisces Supercluster

Once again comparison between my work and image from Hubble Space Telescope:
Impressive, isn't it? And the HST image is actually scaled down to 50% of original resolution.

And the full frame:
Clear skies!

* "Island universe" is a term for galaxy proposed by Edwin Hubble in year 1924 when he discovered that some of observed nebulaes are actually other galaxies like the Milky Way and contains billions of stars. 90 years ago all galaxies were known as our Milky Way nebulaes, and since that time universe grown millions times. 

Thursday, November 7, 2013

Triangulum treasures



In the constellation Triangulum not much fancy objects there are... One spectacular is the M33 spiral galaxy - also calle Triangulum Galaxy, not because of its shape, but because of its position in Triangulum constellation. M33 galaxy (also catalogued as NGC598) is the third largest member of our Local Galaxy group. Contains about 40 billion stars (our Milky Way contains 10 times more) and its mass is estimated for 50 billion Solar masses. M33 apparent size in the sky is quite large - over two times more than apparent Moon diameter, but its surface brightness is very low. However under exceptionally dark sky M33 galaxy can be spotted with naked eye. Latest estimations indicates that Triangulum Galaxy is placed about 2.7 million light years away and it makes it probably the most distant object that can be seen with unaided eye. Between M33 galaxy and M31 Andromeda Galaxy there are several streams of neutral hydrogen and separate stars (see http://astrobites.org/2013/05/15/mysterious-gas-clouds-between-m31-and-m33/ ) . It may indicate some past interaction that took place bewtween 2 and 8 billion years ago.

M33 galaxy contains many H II regions. Four of them have been discovered by William Herschel in 1784, and they are also listed in the picture below as NGC objects. The most famous of these regions is NGC604. This region is somehow similar in structure to Orion Nebula, but it is about 50 times larger. In fact, the NGC604 region would fill the whole distance between us and Orion Nebula that is placed about 1400 light years away.
In the picture below you will find marked some interesting objects placed in M33 galaxy. C27 and C39 are the largest globular clusters in this galaxy, and GR290 is LBV star that shows 1 magnitude amplitude eruptions every about 20 years, and smaller ones with scale of about 320 days. Other object are H II regions.

Another picture shows enlarged fragment of the whole frame. You can see here some faint and distant galaxies - about dozen of them. They are very remote, no exact data about actual distance, but basing on their size and brightness they may be a few hundreds or even one thousand times more distant than M33 galaxy. 

Clear skies!

Ah, the full frame of course - north is up:

And one more picture - NGC604 cut from my picture compared with Hubble Space Telescope image - guess which one is mine :)