FRS 103 - Modern Observations in Astronomy

CCD Observations Results.

Donald F. Collins, PhD

Here we will post the results from the CCD observations that students have assisted in recording.  These include images of deep sky objects and results from variable star observations.  The telescope used for these objects is a 20 cm diameter telescope donated by Bernard Arghiere of Asheville, NC.  The camera for most images was obtained with a grant from the American Astronomical Society.


Trifid Nebula - Also called Messier 20 or M20. 

Recorded by Elise Anderson, Gordon Jones, Erin Long, and Jenna Blakley on Sept. 5, 2007.  The telescope is a 20 cm aperture telescope on a computerized Celestron GT mount.  The camera is the Meade Deep Sky Imager (DSI-Pro).  Jenna Blakley processed the multiple images in each color (red, green, and blue) to assemble the image in full color.

The Trifid Nebula is a member of a class of nebulae called "Emission Nebulae".
Ring Nebula - Also called Messier 57

Recorded by Erin Long and Kelly Hawkins on Sept. 17-18, 2007. 

The image was recorded in three colors plus the luminance (total light value) using the cooled CCD camera (SBIG ST-7) mounted on the 20 cm diameter telescope.  However, only the luminance is shown here.  We are awaiting processing to add all the colors to the image.

The Ring Nebula is an example of a planetary nebula, although it has nothing to do with planets!

Dumbbell Nebula - Also called Messier 27.

This is a color image recorded over two sessions.  Emily Woodall on Saturday, Sept. 15, 2007 recorded the luminance value.  Alex Pearce on Sept. 19, 2007 recorded the image through 3 filters: red, green, and blue.  Emily Woodall performed the extensive color processing - aligning and co-adding many images in each of the primary colors and combining them to produce a composite color image.  Compare the resultant multi-image sum at right with a preliminary image of only one frame for each color below.

The Dumbbell Nebula is another planetary nebula.
The image at right is a preliminary color version - only one image of each color is included.
NGC 7635.  Also called the Bubble Nebula.
Photographed on Oct. 1, 2007 with the help of  Laurel Thwing, Valerie Moore, Jake Lyerly, and Gordon Jones

This is an emission/reflection nebula caused by extremely hot UV emitting young stars.  The "Bubble" is a shock wave of expanding winds from an invisible star at the center of the bubble.  The shock wave interacts with the interactinbg mater in the cloud and forms the luminiscent sphere.

M15.  A globular cluster in Pegasus.
Photographed on Oct. 1, 2007 with the help of  Laurel Thwing, Valerie Moore, Jake Lyerly, and Gordon Jones.

Globular clusters are extremely interesting.  They are massive clusters containing as many as 500,000 stars.  Globular clusters are also very old - much older than the Sun and the Solar System.  Part of the reason for the large age of globular clusters arises from the high gravitational stability of these clusters.  There are so many stars that the mutual gravitational attraction of the stars binds the cluster together.

One might ask, "Why don't the stars all collapse towards the center into one massive black hole?".  The answer comes from the fact that these clusters are dynamic - the stars are all in various orbits about the center of mass.  Spectral studies reveal the motions of the stars in the clusters.  There is definite evidence that the core of these clusters contains a very massive black hole - arising from stars colliding and dissipating their energy and eventually "condensing" into the black hole.

This photo is a color photo made up of about 10 20second exposures through each primary-colored filter plus a no-filter to capture the luminance.  The image has been digitally enhanced to reveal more discrete stars in the core of the cluster.

Monocolor image of M22 - a globular cluster.  Photographed by Jessie Read, Penye Su, Gordon Jones, and Don Collins.  This is a closer globular to Earth than M15 above, hence the larger apparent size.

M29 - An Open Cluster in Cygnus
Photographed and processed on October 15 by Chelsea Gandy.  This is a color image made by  recording 3 images - one in each primary color (red, green, and blue).  The  colors are then combined by overlapping the three images, the image from the red filter "paints" the pixels red, the green filtered image paints the pixels green, etc.

Open clusters, in contrast to globular clusters, are rather young structures.  All the stars in an open cluster are presumed to be about the same age, formed by the gravitational condensation of ancient prestellar material (mostly hydrogen).  The Trifid Nebula at the top of this page is an example of the stars currently forming from the condensation of clouds.  Astronomy classes at Warren Wilson College study the relative ages of open clusters by plotting the brightness of stars against the color (a Hertzsprung-Russell diagram).  The stars in open clusters eventually dissipate - there is not enough self gravity to hold the cluster together after a few billion years - unlike the globular clusters.

M11 - An Open Cluster in Scutum.  Also known as the "Wild Duck" cluster.
Photographed on October 8, 2007 by Jessie Read, Penye Su, and Gordon Jones.  The color was processed by Gordon Jones.  The image is constructed by three primary colored filters similar to the discussion for M29 above.

M11 is one of the densest open clusters known.  Compare the density of stars in M11 with M29 above.  However, the number of stars in M11 is still negligible compared to the half-million stars believed to lie in a typical globular cluster.

The Great Galaxy in Andromeda - Also known as M31.
Photographed by Jake Lyerly and Chloe Stuber and D. Collins.  We photographed 11 frames in different parts of this huge structure.  Taylor Sanford assembled all 11 frames into this large mosaic image.  Notice the details in the dust lanes throughout the galaxy.

The Pinwheel Galaxy, M33.  Photographed November 7, 2007 by Pengye Su, Chloe Stuber, Emily Woodall and Don Collins.  Notice the spiral structure of this galaxy.  It is about 3 million light years distant, and considerably smaller than M31.  It is a member of the Local Group of galaxies that include the Milky Way and M31.

Cataclysmic Variable V455 Andromedae light curve.  A major research effort by Dr. Donald Collins involves observing cataclysmic variables.  The star, newly designated V455 And, has recently erupted (September, 2007) and shows amazing variability with major cycles lasting about 90 minutes.  These variable stars are of major interest with the Center for Backyard Astrophysics (http://cba.phys.columbia.edu/) and the American Associan of Variable Star Observers (http://www.aavso.org/).  The light curve at right shows characteristic oscillations during outbursts called "super humps".  The sporatic data between the first and second maximum represent clouds obscuring the image.

The graph below right shows the light curve variations 2 nights later.  The axes are different, so the amplitude of the oscillations are about the same, but the shape of the "humps" is decidedly different.  This is a very dynamic system.


This is the image of V455 Andromedae in relation to other stars.  It has recently brightened by a factor of 100 times its quiescent value.  Image by WWC telescope and CCD camera.





A major interest in the study of cataclysmic variables is the period analysis.  These are very complicated systems.  The white dwarf is extremely massive and dense.  A white dwarf is about the size of the Earth but the mass of the Sun - making it about 1 Million times more dense than the average density of the Earth.  The white dwarf star and an ordinary star are in close orbit around each other.  The time for one orbit is usually between 1-3 hours.  90 minutes in the case of V455 And.  The stars are so close that the white dwarf is constantly pulling material from the ordinary star - and the material eventually lands on the white dwarf emitting UV radiation and even X-rays.  However, due to the high orbital velocity of the system, the material does not fall directly onto the white dwarf, but circulates in orbit about the white dwarf forming an accretiion disk.  The physics of the accretion disk is very complicated due to the turbulence, the differential rotation, and the tidal effects of both stars. 
All sorts of variations in brightness appear as shock waves build up and mofify the light output.  One very interesting feature is the appearance of the spinning rate of the white dwarf itself.  Analysis of the light curve above (the Sept. 19 version) shows the presence of a 67 - 68 second oscillation (immersed in many other frequencies and signals).  This signal is believed to be due to the spinning of the white dwarf itself.  Other signals vary in time from day to day, but the 67-68 second signal persists at the constant rate all through the eruptions of this system.  I refer this to the "hard core" rotation rate.

Open Cluster M39.  Photographed on October 29, 2007 by Jenna Blakley, Jake Lyerly,  and Don Collins.  This is a color photo.  Several images in each of the primary colors: red, green, and blue were made.  The images were processed by Ted Risberg.  The processing involves adding the images of each color to minimize noise, then aligning the images of the different colors and forming a composite color image where the red image illuminates the red pixels, green image illuminates green pixels, etc.

The astronomy students will study the color of the stars to determine the relative age of the cluster.  Notice that the bright stars are white and the fainter stars are red.  This indicates a fairly young cluster.  There is one fairly bright reddish star near the center of the image.




Comet Holmes.  Photographed on Oct. 29, 2007 with assistance from Jenna Blakley and Jake Lyerly using the guided telescope and the CCD camera.  This comet had been a very faint comet quite invisible to naked eye, then it suddenly erupted last week to over 1 million times its normal brightness to be visible to the un-aided eye.  To the unaided eye, it looks like a star in Perseus near the 2nd magnitude star Mirfak.

Comet Holmes on Nov. 7, 2007.   Photo by Emily Woodall, Pengye Su, and Chloe Stuber.  The comet has grown in apparent size since Oct. 29, even though the comet is receding from Earth and the Sun.  The reason for the growth is that the dust that was released by the "explosion" during the week of October 22-26 has diffused into a larger volume of space.  Our view of the comet is almost head-on.  The tail streams out directly behind the comet in the direction opposite the sun.  Notice the assymetry of the comet.  This is attributed to the tail streaming at a slight angle to our perspective.  Notice also the bright, small head of the comet slightly below the center of the cloud in both pictures.  This picture awaits color processing.  We will keep monitoring this amazing comet.  We expect that it will continue to grow brighter and more diffuse as the cloud continues to expand and become blown away by the Sun's radiation pressure.


Nov. 28, 2007.  Gordon Jones, Valarie Moore, Taylor Sanford

Dec. 6, 2007.  Jessie Read, Laurel Thwing, Kelly Hawkins. The comet is continuing to grow.  The "tail" shows a sligtly different orientation.
At right is a digital camera photograph (Don Collins) of Comet Holmes and its relation to the stars in Perseus.  The image was made on October 30, 2007.  We will examine the position of the comet in the following weeks.

M1 - The Crab Nebula.  Photographed Nov. 28 by Gordon Jones, Taylor Sanford, and Valerie Moore.  The Crab Nebula is a supernova remnant from a supernova that exploded in 1054 AD and recorded by the Chinese.  The nebula has been expanding ever since.  In the center of the Crab Nebula lies a neutron star pulsar that "flashes" about 30 times a second.  The neutron star is the collapsed core of the star that exploded.  The neutron star is only about 10 km in diameter, and,has approximately the mass of the sun.  The density is on the order of 109 gm/cm3.  The structure of the Crab Nebula is very complicated consisting of intense magnetic fields twisted and contorted in all directions.  That gives teh wispy appearance to this nebula.