Physics Photo of the Week

Physics Photo of the Week March 20, 2026   Ice Sprouts - Photos by Henry Willis; Discussion by Donald Collins My friend, Henry Willis, sent me this photo of "ice sprouts" taken during a trek in the Great Smokies National Park earlier this winter.  Although fairly common, ice sprouts this large are quite unusual.  These sprouts are about 2 inches tall.  Ice sprouts are formed when bare ground, that has been saturated with rain water, freezes.  The amazing property of water is that the ice phase is less dense than water.  Ice cubes float on top of your drink of iced tea.  Most solid objects are more dense than their liquid counterparts.  When the muddy soil freezes, the freezing takes place on the top of the mud. The frozen surface confines the remaining water beneath the surface.  The remaining water under the top shell freezes and expands; pressure builds up and the expansion force breaks through cracks in the shell; the water is forced out a...

Physics Photo of the Week February 20, 2026   Bursting Raindrops  -  photo by Donald Collins On a winter day in December 2023 I noticed these unusual photos of frozen raindrops on our house deck near Warren Wilson College.  We had a sudden freeze overnight.  The rain had beaded up on the deck boards - probably having been staine in the early summer.  The water and the deck stain repel each other so the surface tension of the water being forced away from the deck stain caused the droplets to bead-up like small spheres with the surface tension forces in equilibrium with the gravitational forces. However when the water drops froze, the ice formed on the outside parts of the droplets, leaving unfrozen water inside.  As the water within the drops froze, the expansion of water upon freezing exerted pressure on the frozen skin of the raindrops, that the droplet burst, shooting a small jet of water that almost immediately froze.  Practically all the ...

  Physics Photo of the Week January 23, 2026   - Solstice Sunrise - Photos by Donald Collins      Within two days of the 2025 winter solstice, when the weather permitted, I snapped a photo of the Sun rising over the Swannanoa Mountains looking southeast from my home near Warren Wilson College.  I was away on the actual December 21 solstice, but this photo was taken at 8:11 AM on December 19, 2025 very close to the true solstice.  The "solstice" literally means the "standstill of the Sun".  The Sun on the on the winter solstice stops its apparent southerly fall migration of its rising point, and gradually begins its northerly migration of the rising point.  The solstice day is the day of the year with the shortest amount of daylight and marks the beginning of the calendar season of winter. After the solstice, the Sun's rising position gradually moves northward along the horizon.  The image below shows the position and time of sunrise for...

May 9, 2025 Open Star Clusters - Astrophotos by Donald Collins, College View Observatory   Throughout the Milky Way Galaxy there are thousands of open star clusters.  One of closest open star clusters is the Pleiades - or "Seven Sisters" - featured in the lower left photo.  The Pleiades cluster is the closest cluster from the Earth - 440 light years distant.  The bright stars of the cluster form a small "dipper" asterism.  Star clusters are groups of stars within the spiral arms of a galaxy and have formed from relatively recent condensations from clouds of gas and dust within the galaxy.  The Pleiades are about 100 million years old, which is fairly young for star clusters.  The stars were formed from the gravitational condensation of gas and dust clouds into several hundred stars.  The Pleiades is easily seen with naked eyes throughout late fall through mid spring.  They are visible now (late April) in the western sky about halfway between ...

Physics Photo of the Week April 4, 2025 Galaxy M106 - Photo by Donald Collins - College View Observatory Galaxy M106 - the 106th entry in Messier's famous catalog of deep sky objects - lies about 20-25 million light years from Earth.  It is about 10 times further than the Andromeda Galaxy and about twice as far away as the recently featured Galaxy M87 .     As with most galaxies, M106 contains on the order of 100 billion stars , and most likely has a supermassive black hole lurking deep in its core.  Celestial south is up in this photo. This galaxy is interesting in that there are many star-forming regions within the spiral arms.  It's also rather "clumpy".  The clouds of dust and stars are not very evenly distributed.  The clumps of new young stars are the clumps that appear brighter and "bluer" in the photo.  The clumps of stars eventually will dissipate and result in open clusters similar to the Pleiades (Seven Sisters) star cluster in our own...

  Physics Photo of the Week Total Lunar Eclipse of March 14, 2025 Moon Photos by Donald Collins The weather improved last week for an excellent viewing of the total lunar eclipse.  The Moon was totally within Earth's shadow between about 2:30 am to about 3:30 am.  The Moon takes on this reddish color when totally within Earth's shadow.  The animation below consists of three frames: 1-Near the beginning; 2-near the middle of eclipse; 3-near the end of the hour-long totality.  If you look carefully you can see two stars in the right half of the images.  The stars are stationary relative to the tracked telescope.  In the hour-long totality the Moon has moved approximately one radius relative to the stars as the Moon orbits the Earth.  The Earth's shadow also moves due to the Earth moving in its orbit around the Sun, but the Earth's shadow is much slower than the Moon's motion.  Unfortunately, I did not get any partial phases of the Earth's shado...