22. April 2011 by RC Davison.

     Interacting galaxies come in all shapes and sizes.  This pair, known as Arp 237 or UGC-1810 and UGC-1813 bear a striking resemblance to a flower - a rose as stated on the Hubble site is even more precise.

 (Link to larger images)

     The blue “icing”at the top of the image are hot blue stars that have formed in the wake of the collision.  You can also see a region of new star formation in the center of the smaller galaxy, also most likely due to the collision.

     But, there are jewels strewn all about in this image: A small blue galaxy to the left of the larger UGC-1810 and a red spiral galaxy visible between its arms to the lower right.

   This clip will show you where the galaxies are and zoom in to them.  But, if you can, download the largest image possible, zoom in and explore this beautiful image.

    It is also noteworthy that this image commemorates Hubble’s 21st anniversary of operation in space.  It’s hard to imagine that is has been that long!

     A note about housekeeping on the site.  I’ve categorized the blog posts so it will be easier if you are looking for a particular post to search by category.  The categories used are listed at the bottom of the post and you can click on them to sort the blog.  They are also listed on the right side of the web page.

• Astronomy
• Cosmology
• Galaxy
• Humans in Space
• Orbital Maneuvers
• Solar System

Hopefully this will be of use to you in the future.

Till next time,

RC Davison

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10. April 2011 by RC Davison.

     The science of astronomy is fascinating in that it involves some of the most bizarre concepts in nature.   But, it can be one of the most frustrating fields of study because we must do everything at a distance.  We can’t touch a star.  We can’t see the evolution of most events in the cosmos because the time they take far exceeds our meager lifetimes. (That is, short of an event like a supernova.) Everything we know about the cosmos has been learned by observation via the electromagnetic spectrum, historically in the visible wavelengths and today we cover the entire electromagnetic spectrum.   It is with these observations, coupled with a basic understanding of physics and chemistry learned on Earth, along with theories developed by some very intelligent people that have led to new discoveries in the cosmos.

      It has been theorized that stars that orbit a black hole, (like the ones that move around the black hole at the center of our galaxy) may eventually be pulled into the black hole.   This unfortunate star would be ripped apart by the tidal forces exerted on it from the black hole, and its remains would be pulled past the event horizon into the waiting singularity.  This star stuff would release tremendous amounts of energy as it spiraled down into the black hole, moving faster and faster and approaching relativistic speeds.  This energy would be radiated away from the black hole in high energy jets that are perpendicular to the disk of debris falling into the black hole.   This is theory.  We haven’t actually seen this happen – yet.

      An event that was documented on March 28, 2011 by the Swift gamma-ray telescope (gamma-ray burst (GRB) 110328A), followed up in the visual part of the spectrum by the Hubble telescope and finally confirmed by the Chandra X-ray telescope may have identified such an event.   The object located in a galaxy 3.8 billion lightyears (ly) from us in the constellation of Draco, visible from the northern hemisphere.   This is what Swift, Hubble and finally Chandra saw as they hunted down the source of the gamma rays:

(HubbleSite.org)

       The Swift telescope picked up on a gamma-ray flash and documented a series of flashes, which instead of getting dimmer actually got more intense.   This is not typically seen. When a star goes supernova it emits an enormous burst of energy that fades over the a period of 3-4 weeks or more as indicated in the graph below.

      What Swift saw was this:

(HubbleSite.org)

      Distinctly different.   If the theory is correct then we are seeing these bursts of energy because the orientation of the black hole relative to Earth is such that these jets point our way.

      The proposed scenario that matches up with the observation is depicted in the image below:

(HubbleSite.org )

      Frustratingly, we can’t see this!  We can only surmise from the data that this is what is happening at the core of this galaxy 3.8 billion ly away.   But, imagine what it must have looked like to see this star in its final death throws as it passed the black hole for the last time…

Till next time,

RC Davison

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5. April 2011 by RC Davison.

     There are jewels in the night sky and some of them are more fanciful than others. The spiral galaxy NGC 4921 is a case in point. Please click on the following links in the article for much higher resolution images. (Click for a larger image.)

      This beautiful barred-spiral galaxy resembles more a ghostly cosmic jelly fish than the typical spiral galaxy you may think of like the Whirlpool galaxy (M101) below:

     You’ll notice immediately that NGC 4921 is missing the well defined spiral arms seen in the Whirlpool. There is structure there, but it is much more subtle.  You do see a dark swirl of dust around the core, accented with bright blue stars that are forming along this band.  And, you can see the bar that extends across the nucleus of the galaxy as well as some spiral structure to the arms.

     To me, what is most remarkable about this galaxy is that the white gossamer cloud is not dust but stars – billions and billions of unresolved stars spread very uniformly around the galaxy.  In a well defined spiral galaxy we don’t get the same impression of the vast number of stars contained within because they are clumped together in the arms.  NGC 4921 and the Whirlpool galaxies are roughly the same size (about 200,000 lightyears verses 175,000 lightyears across), so comparing the two galaxies gives a good sense of how many stars are condensed into the arms.  It is interesting that this type of galaxy is termed an “anaemic spiral” because of the uniform distribution of stars.

      The galaxy is located about 320 million lightyears away in the galaxy cluster known as the Coma Cluster or alternatively Abell 1656 in the constellation Coma Berenices.  If you look closely at the image you will see thousands of galaxies scattered about NGC 4921 and even behind the nebulous galaxy.  Some are part of the Coma Cluster, while others extend much further beyond it.  This annotated image below (Click for a larger image.) shows highlights some of the details contained in this amazing image.

     Check out the Hubble website for more information, images and several short videos that will give you more in-depth information about this beautiful jewel of the night sky.   Enjoy the wonders of the Cosmos!

Till next time,

RC Davison

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