Astrophoto Friday - A Marvel in the Darkness

Antonin Mrkos discovered seven comets. These photos of his brightest comet (1957 D) were taken in August 1957 with Palomar Observatory's 48-inch Schmidt Telescope (now called the Samuel Oschin Telescope) by Charles Kearns, George O. Abell and Byron Hill.


Be sure to click on the image to make it larger to see the wonderfully detailed structure of the comet's tail.

Asteroid 596 Scheila Becomes a Comet

Over the weekend it was reported that main-belt asteroid 596 Scheila was experiencing a comet-like outburst. Solar system astronomers Michael Hicks and Kenneth Lawrence from the Jet Propulsion Laboratory happened to have observing time on Palomar’s 200-inch Hale Telescope last Saturday night and early Sunday morning they captured this image of "asteroid" 596 Scheila looking very much like a comet:


The two main ideas behind Scheila’s cometary outburst are that it is either a rare comet with an orbit inside the asteroid belt that started out gassing or that it has recently suffered a collision like the one in 2009 that befell an asteroid known as P/2010 A2.

Stay tuned.

Thanks to Mike & Ken for being kind enough to share this raw image of the event so soon after it was acquired!

For a related post see also, The Asteroid that Became a Comet and the Comet that Became an Asteroid.

Astrophoto Friday: Comet Arend Roland

Comet Arend-Roland photographed April 26, 1957 with the 48-inch Palomar Schmidt telescope (now called the Samuel Oschin Telescope).


For part of its passage around the Sun this comet offered up a spectacular anti-tail - a spike of dust sometimes seen as a comet passes through the orbital plain of the Earth.

The Asteroid that Became a Comet and the Comet that Became an Asteroid

Once in a while an asteroid comes along that changes things.

On January 6, 2010 the Lincoln Near Earth Asteroid Research team discovered a main-belt asteroid that was experiencing an outburst making it look like a comet. Comets aren't normally found in the asteroid belt and early indications suggested that this was an asteroid that had suffered a collision, which produced it's comet-like outburst and tail. A photo released yesterday (below) taken by the Hubble Space Telescope reveals that the object's tail does not resemble that of a normal comet and that the bright star-like nucleus is strangely offset from the tail itself. All of this tends to support the idea that this display is the result of the collision of two asteroids - an event never before witnessed.


Seeing an asteroid have a comet-like outburst reminds me of the case of a comet that apparently converted into an asteroid. Back in November 1949 Albert Wilson and Robert G. Harrington were using the 48-inch Schmidt (now called the Samuel Oschin Telescope) taking photos for first Palomar Sky Survey when they discovered a comet. Comet 107P/Wilson-Harrington was photographed by the duo over three nights but there was great uncertainty in the orbit and it was eventually lost.

Thirty years later, in November 1979, Eleanor Helin was observing at Palomar when she discovered a new asteroid temporarily dubbed 1979 VA. You can see it as the streak in the center of the image below.


In the early 1990s it was determined that Comet Wilson-Harrington and asteroid 1979 VA were the same object. The asteroid is now known as 4015 Wilson-Harrington and is thought to be a comet that lost all of its icy volatiles, or in essence a "burned out" comet. For more on the discovery of Wilson-Harrington have a look at this page over at Cometography.

Why do astronomers think that Wilson-Harrington is a dead comet and not an asteroid that had a collision back in 1949? It's orbit.

Orbit diagram from the JPL Small-Body Database.

Notice that Wilson-Harrington's orbit is elliptical like a typical comet. At its farthest point from the Sun it is out in the asteroid belt, but at its closest point it comes in a little closer to the Sun than Earth is. Just like a typical comet, this one had its 1949 outburst when it was close to the Sun and its heating.

By the way, as of a few days ago the count of the total number of asteroids discovered at Palomar Observatory stood at 23,366.

Remembering Apollo, a Comet Crash & Eugene Shoemaker

Yesterday, July 16th was the 40th anniversary of the liftoff of the Apollo 11 Mission. NPR had a wonderful story on the role of the USGS's astrogeology team in the training of the Apollo astronauts. Click on over to see and hear One Small Town's Big Role In The Apollo Missions.

Some of the time in the story is devoted to Eugene Shoemaker, the father of astrogeology. Gene was an astronaut hopeful, but a medical condition kept him grounded, but without his hard work and guidence the Apollo missions would not have been as scientifically productive as they were. If you visit the NPR page, in addition to listening to or reading the story, be sure to watch the USGS film on rocketpacks. It is fantastic.

Running the story on July 16th, not only marked the Apollo 11 anniversary, but also the anniversary of the first impact of the fragments of Comet Shoemaker-Levy 9 with Jupiter back in 1994. Comet Shoemaker-Levy 9 was discovered at Palomar in 1993 with the 18-inch Schmidt.


The impact of the cometary fragments with Jupiter was one of more important astronomical events of the 20th Century. This animation gives a rapid look at the comet crashes which lasted from July 16 - 22, 1994. The animation does indeed give a proper sense of the affects of the impacts that resulted in Jupiter's atmosphere. Many of the dark clouds that appeared from the impacts were larger than Earth.



If you want to learn more about the amazing life of Eugene Shoemaker, I highly recommend David H. Levy's book Shoemaker By Levy. It is a wonderful, personal look at Gene and his scientific career.

Palomar Transient Factory

Unique Sky Survey Brings New Objects into Focus

Partnership involves Caltech's Palomar Observatory and other world leaders in astronomy

San Diego, Calif.–An innovative sky survey has begun returning images that will be used to detect unprecedented numbers of powerful cosmic explosions–called supernovae–in distant galaxies, and variable brightness stars in our own Milky Way. The survey also may soon reveal new classes of astronomical objects.

All of these discoveries will stem from the Palomar Transient Factory (PTF) survey, which combines, in a new way, the power of a wide-field telescope, a high-resolution camera, and high-performance networking and computing, with rapid follow-up by telescopes around the globe, to open windows of discovery for astronomers. The survey has already found 40 supernovae and is gearing up to switch to a robotic mode of operation that will allow objects to be discovered nightly without the need for human intervention.

The Palomar Transient Factory is a collaboration of scientists and engineers from institutions around the world, including the California Institute of Technology (Caltech); the University of California, Berkeley, and the Lawrence Berkeley National Laboratory (LBNL); Columbia University; Las Cumbres Observatory; the Weizmann Institute of Science in Israel; and Oxford University.

During the PTF process, the automated wide-angle 48-inch Samuel Oschin Telescope at Caltech's Palomar Observatory scans the skies using a 100-megapixel camera. The flood of images, more than 100 gigabytes every night, is then beamed off of the mountain via the High Performance Wireless Research and Education Network­–a high-speed microwave data connection to the Internet–and then to the LBNL's National Energy Scientific Computing Center. There, computers analyze the data and compare it to images previously obtained at Palomar. More computers using a type of artificial intelligence software sift through the results to identify the most interesting "transient" sources–those that vary in brightness or position.

Within minutes of a candidate transient's discovery, the system sends its coordinates and instructions for follow-up observations using the Palomar 60-inch telescope and other instruments.

Soon all of the steps in the process will be completely automated, including decisions about which transients merit a second look. When follow-up observations indicate that candidate transient detections show promise, a prioritized list of candidates is brought to the attention of astronomers from the PTF member institutions. Finally, an astronomer becomes personally involved, by performing detailed observations using telescopes such as Palomar's 200-inch Hale Telescope, a Keck Telescope in Hawaii, or other partner telescopes around the world.

The PTF is designed to search for a wide variety of transient sources with characteristic timescales ranging from minutes to months, giving astronomers one of their deepest and most comprehensive explorations of the universe in the time domain.

"By looking at the sky in a new way, we are ushering in a new era of astronomical discovery," says PTF principal investigator Shrinivas Kulkarni, MacArthur Professor of Astronomy and Planetary Science at Caltech and director of the Caltech Optical Observatories. "Nimble automated telescopes and impressive computing power make this possible."

"No one has looked on these timescales with this sensitivity before. It's entirely possible that we will find new astronomical objects never before seen by humans," says Nicholas Law of Caltech, the project scientist for PTF.

Because it looks for anything changing in the sky, the PTF survey covers a vast variety of different astronomical targets. The wide range of the survey extends across the entire universe. Astronomers expect to discover everything from stars exploding millions of light-years away to near-Earth asteroids that could someday impact our planet.

Much of the survey's time is spent searching for so-called Type Ia supernovae. These supernovae, formed from the explosion of a class of dead star known as a white dwarf, are very useful to astronomers because they can help determine the distance to galaxies located across the universe. Those distances allow astronomers to probe the origin, structure, and even the ultimate fate of the universe.

By operating more rapidly than previous surveys, PTF will also detect objects of a completely different nature, such as pulsating stars, different types of stellar explosions, and possibly planets around other stars.

PTF's innovative survey techniques also have raised astronomers' expectations of finding new, unexpected, astronomical objects.

The PTF already has found many new cosmic explosions, including 32 Type Ia supernovae, eight Type II supernovae, and four cataclysmic variable stars. Intriguingly, PTF also has found several objects with characteristics that do not exactly match any other objects that have been seen before. PTF astronomers are eagerly watching these objects to see how they change, and to determine what they might be.

The quantity and quality of incoming data have astonished astronomers working in the field. On one recent night, PTF patrolled a section of the sky about five times the size of the Big Dipper–and found 11 new objects. "Today I found five new supernovae before breakfast," says Caltech's Robert Quimby, a postdoctoral scholar and leader of the PTF software team. "In the previous survey I worked on, I found 30 in two years."

Images and more information on the PTF survey are available on the PTF website at http://www.astro.caltech.edu/ptf

One of the most intriguing PTF discoveries, the object known as "PTF09dh" (above, right)appeared in a blank patch of sky and brightened as PTF watched from Palomar Observatory. The PTF collaboration is packed with supernova experts, but this discovery already has the team stumped--and excited. "For a cosmic explorer like me, the stream of curve balls served up by the universe makes for good job security. I take this as a sign there is plenty more waiting to be discovered.", said Robert Quimby, PTF's Software Lead.

Credit: PTF Collaboration

Comet 65P (Comet Gunn) as seen by PTF. The moving, and well known, comet was detected as a changing object by PTF on several nights, and was one of the first system verification images.

Credit: PTF Collaboration

Shoemaker-Levy 9 Anniversary

Fourteen years ago today began perhaps the biggest week of astronomy ever as the fragments of Comet Shoemaker-Levy 9 began to slam into Jupiter.

The comet was discovered at Palomar by Eugene M. Shoemaker, Carolyn S. Shoemaker and David H. Levy using the 18-inch Schmidt on March, 1993.

From July 16 - 22, 1994 the astronomical world was captivated as at least 21 fragments of the comet collided with Jupiter. This was the first time that anyone was able to witness the collision of an comet or asteroid with a planet. The results were spectacular as Earth-sized clouds were produced in Jupiter's atmosphere that could easily be seen in small, amateur-sized telescopes.

The 200-inch Hale at Palomar was one of the many telescopes observing the event.

Image caption:

An infrared image of Jupiter at a wavelength of 2.3 microns, constructed in a computer from 5 individual images taken from Palomar Mountain on July 23rd and 24th, 1994, showing the scars left by the multiple impacts of Comet Shoemaker-Levy 9. The picture shows the planet as it would appear to an observer located above 45 S, 60 W. The prominent impact sites E, H, Q, G, and L (from left to right) are visible at 44 S, surrounding the bright South Polar Hood. The smaller spot between the Q and G impact sites is due to the R impact, which was observed directly from Palomar. The Polar Hood and the impact sites both appear bright in this image because they are composed of particulate clouds that are high above an opaque layer of gaseous methane, which obscures the underlying cloud deck at this wavelength. The fainter feature at 20 S, near the western limb of the planet, is the famous Great Red Spot.

JPL has an amazing archive of images from the event captured by telescopes on Earth and in space. Be sure to check it out as a part of your SL9 celebration.

Shattered Comet

Two years ago this week Caltech astronomers were using the 200-inch Hale Telescope to observe the fractured Comet 73P/Schwassmann-Wachmann 3 as it came relatively close to Earth.

The comet was discovered by Arnold Schwassmann and Arno Arthur Wachmann in 1930. In 1995 the comet was found to have broken up into four fragments in 1995. By its 2006 passage it had further split into dozens, if not hundreds, of pieces.

The animated gif above shows a sequence of 15 looped images showing the in the foreground against distant stars and galaxies which appear to streak across the frame. Because the comet was moving at a different rate across the sky than the stellar background, the telescope was tracking the comet's motion and not that of the stars. Many fragments of the comet are visible as nearly stationary objects in the movie. In all, 16 new fragments were discovered as a part of the Palomar observations.

Targeting a Comet

On this day in 2004 NASA's Stardust mission encountered Comet Wild 2, taking detailed images. Before the mission's closest approach, the comet moved from the daytime sky into the nighttime sky and could just barely be observed with telescopes. Tilted close to the horizon, critical observations of the comet's location and brightness were made using the 200-inch Hale Telescope just two weeks prior to the flyby. These observations helped to target the spacecraft to its successful encounter.

The nucleus of comet Wild 2 as photographed by the Stardust spacecraft.