Celestial Jewelry

The Hubble Space Telescope has taken a fascinating image of a planetary nebula known as the Necklace Nebula.

Necklace Nebula - Courtesy of the Hubble Space Telescope site

Planetary nebula are the remains of a star like our Sun as it goes through the final stages of its life expanding and blowing off its outer layers.  The bright blobs embedded in the nebula are areas of gas that are energized by ultraviolet light from the star at the center.  The blue-green color of the nebula reflects the hydrogen and oxygen present, with red indicating nitrogen.  The Necklace Nebula lies about 15,000 light years from us and is located in the constellation Sagitta.

It’s interesting to compare this planetary nebula with the remains of the supernova 1987a:

Supernova 1987a - Image courtesy of the Hubble Space Telescope

     Another piece of cosmic jewelry, but one made from a very different process and from a star that was much larger than our Sun. The supernova is the foundry that produces all the heavy metals we have today, from the iron in the hemoglobin of your red blood cells to the gold and silver in the jewelry you may be wearing right now.

     Both of these nebulae are still evolving, and as time passes they will continue to evolve into new shapes, and eventually (10s to 100s of thousands of years) they will fade from view.  But, their remains will fuel the next generation of stars and planets in the cosmos.

Till next time,

RC Davison

Unique Views of the Cosmos

Two items of interest popped up last week:

First:  The European Space Agency posted a very nice video showing the Andromeda Galaxy in light from X-rays to gamma rays.  About a third of the way into the video, one can see variable stars pulsing and other stars flashing as they go nova, thanks to the view from the XMM-Newton X-ray telescope. Check out “Andromeda’s coat of many colours“.  (Check out the post on 6, January 2011 under the galaxy category for more information about Andromeda.)

Andromeda Galaxy (M31) iImage courtesy of Tony Hallas and APOD.NASA.Gov

Second:  An image posted on the Astronomy Picture of the Day site by Juergen Michelbergershows in very unique detail how stars and planets are affected by Earth’s atmosphere.  Or, more appropriately, why stars twinkle and planets don’t.

The star Regulas (left) and Mars (right): Image by Juergen Michelberger

The star, being much further away from Earth than the planet Mars, presents an image that is much smaller in diameter than Mars.  This smaller point of light is affected by the variations of the Earth’s atmosphere due to temperature and moisture much more so than the larger source of light from the planet.  Consequently, the star’s image is randomly refracted, causing it to vary in color and brightness, while Mars shines on steadily over the ten second exposure.  The intricate image is due the camera being swung about.  Check out the link to APOD above for more information about this unique image.

Till next time,

RC Davison

Galaxies Dancing the Tango

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 siteis even more precise.

Galaxies Colliding UGC-1810 and 1813: Image Courtesy of Hubble Site

 (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.

         Blue Galaxy     Red Galaxy

   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

Star Destroyed by Black Hole?

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:

Swift, Hubble and Chandra's view of gamma-ray source.  Image courtesy of 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.

Supernova light curve - Image courtesy of NASA

      What Swift saw was this:

Light curve from gamma-ray source seen by Swiift - Image courtesy of NASA


      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:

Star being destroyed by black hole - Image courtesy of HubbleSite.org

(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

A Gossamer Galaxy – NGC 4921

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.)

NGC 4921 Image Courtesy of Hubble/ESA

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:

Whirlpool Galaxy - Image Courtesy of Adam Block, Mt. Lemmon SkyCenter, U Arizona

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.

NGC 4921 Annotated Image Courtesy of Hubble/ESA

     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

The Colors of the Universe

We are often so amazed by the colorful images we see of nebulae, galaxies and other deep space objects that we may sometimes forget that these colors are not the natural colors, or at least not the colors we would see if viewed directly by the naked eye.

Part of the reason to color these objects so dramatically is to distinguish the different components of the object. That might be different elements or molecules, densities of matter or different energy levels, say from x-rays to infrared to gamma rays.

It really all comes down to the energy of the photons that the CCDs (use to be photographic film) receive. Typically these images are in black and white and are obtained by passing the light from the object through filters, which allow only certain frequencies or energies of electromagnetic radiation to reach the detector. Below are three images of the Eagle Nebula taken (from left to right) in the green, red and deep red parts of the visible spectrum:

Eagle Nebula - Green Light

Eagle Nebula - Red Light

Eagle Nebula -  Deep Red Light



You can see some subtle differences in the structure. Interesting, but not too exciting. But, if we assign colors to these filtered images so that the green light emitted by the doubly-ionized oxygen is blue, the red light from hydrogen is green and the deep red light from ionized sulfur is red. This helps to distinguish sulfur from hydrogen, which otherwise would both look red.

Eagle Nebula - OxygenEagle Nebula - HydrogenEagle Nebula - Sulfur


This is beginning to look a bit more interesting! Now, by blending these images into one we get the final product:

Eagle Nebula

These color choices show the bluish background of hydrogen and oxygen atoms surrounding the columns of dust and gas containing sulfur. Pretty to the eye and much more informative as to the components that make up the nebula.

These images come from a NASA site “Behind the Pictures”. Check it out. It won’t take long to go through the different pages that talk about using color as a tool, filters and the shapes of the images. There are also many more examples of how this process is applied to learn more about these amazing celestial objects.

Till next time,

RC Davison

The Orion Nebula

The European Southern Observatory has delivered one of the most beautiful images of the Orion Nebula that I’ve seen.

Orion Nebula from the European Southern Observatory

Using their 2.2 meter telescope at the Silia Observatory in Chile, with a series of 5 different filters, the image is close to what one would observe with the naked eye.  But, one needs to remember that the CCDs can collect photons of light over time and build up an image that we humans would not be able to see with the physiology of our eyes.  We wouldn’t be able to see the delicate gossamer structure with the subtle color changes that the CCD can.  So enjoy this beautiful image on your computer!

Orion is riding high in the cold winter night sky and one can easily see the Orion Nebula just below the belt of Orion on the constellation’s left side, as can be seen below.

Constellation of Orion - Credit: Mouser Williams

Orion harbors many wonders, including the red supergiant Betelgeuse marking his upper right shoulder and Rigel, a blue supergiant that marks Orion’s left foot.  Betelgeuse is so large that if placed at the center of our Solar System it would extend beyond Mars and the asteroid belt!  Another jewel that lies within the constellation is the Horsehead nebula, located near the left-most star making up Orion’s belt.

Horsehead Nebula in Orion - Wikimedia Commons

Next time you’re out and about at night, check out Orion, and if you have a pair of binoculars or a telescope available, take some time to check out the jewels that lie within the Orion constellation.

Till next time,

RC Davison

Many Faces of Andromeda

The Andromeda galaxy is one of my favorite galaxies, so the latest images from the European Space Agency (ESA) are a real treat.  Using the Hershel observatory to take Andromeda’s portrait in the infrared and the XMM-Newton X-ray observatory to capture the galaxy’s image in the high energy spectrum, ESA has produced a composite image that shows the star birthing and dying regions of the galaxy in the highest resolution to date.

Multispectral views of Andromeda from ESA's Hershel and Newton

      The top right image show the galaxy in the infrared as taken by Hershel.  This shows the regions of the galaxy where there are concentrations of dust that harbor the development and birth of stars.  The image at the lower right shows the regions hot with X-rays, which is indicative of gas being heated to extremely high temperatures from the shockwaves produced when stars meet their end as novas and supernovas. X-rays can also be generated as one star pulls material from another in a binary pair.  This gas is heated to high temperatures as it is accelerated in its fall to the parasite star.

     The image also shows a high concentration of X-rays at the center of the galaxy, which is to be expected because of the high density of stars there and the resident supermassive black hole that resides at the core of the galaxy. If you look closely at the X-ray image there appears to be a bubble surrounding the core of the galaxy.  Possibly a shockwave propagating outward from the core, indicating a more active period of the galaxy’s massive black hole. Be sure to check the links to see the all the detail in these great high-resolution images.

     Take a look at ESA’s website for more information on these new images of Andromeda.

Till next time,

RC Davison

The Power of Infrared

The power of using infrared light to peer through the dust in the cosmos is clearly demonstrated in this stunning image of the Lagoon Nebula (M8) from the European Southern Observatory’s (ESO) VISTA telescope at the Paranal Observatory in Chile.

Infrared and visual images of the Lagoon nebula

The top view shows a vast field of stars, many of which are cool red stars, but it is the hot young stars that radiate prodigiously in the ultraviolet that help the Lagoon nebula glow in the visible range as seen in the bottom view.

Here is a nice video that fades from visual to infrared views of the Lagoon nebula.

Check out some larger images and more information at ESO’s website

Till next time,

RC Davison


Speaking of Galaxies…

In the last post (It’s Full of Galaxies) we saw an infrared image from the Herschel space telescope looking at a tiny piece of the cosmos revealing thousands of galaxies 10 – 12 billion light-years from us.  The image below is also an infrared image, but it is a view of millions of galaxies as taken by the 2MASS (Two Micron All Sky Survey) looking across the night sky.

2MASS View of the Night Sky

      The blue band in the image comes from the stars in our own galaxy.  Note that the distribution of galaxies is not uniform, as one might expect but there are clusters, strings and webs of galaxies.  These structures are remnants of the big bang and the gravitational attraction between matter and the mysterious dark matter.  Think about this:  All of the matter we can see and account for in the Universe only adds up to about 4-5% of the total mass of the Universe!

     The  2MASS survey was conducted using two 1.3 meter telescopes, one in Arizona and the other in Chile, imaging the sky at 3 separate frequencies in the near infrared.  Imagine what this would look like if we were able to use telescopes in space that are above the filtering effects of our atmosphere in the infrared.

      Check these links for more information and a larger image.

Till next time,

RC Davison