November Astronomical Highlights: Disappearing Planets and a Comet
By Kelly Kizer Whitt
Plenty is happening in the night skies this month.
The full moon takes place in the early morning hours on Nov. 4 for the eastern half of the U.S. and before midnight on Nov. 3 for the western half of the country. November's full moon is sometimes called the Beaver Moon or Frost Moon.
On Nov. 5, the star Aldebaran disappears behind the moon under the lit side before reappearing on the unlit side—a phenomenon known as occultation. Look east-northeast just after sunset as the moon is rising. The farther you are to the north and to the east in the U.S., the more of the event you can see.
November is your last chance to catch a glimpse of the planets in the evening sky before they sneak away to appear only in the morning in December and the beginning of 2018. Jupiter and Venus are already shining like bright beacons in the early a.m., but Mercury and Saturn are still visible at night.
Saturn is higher above the horizon but dimmer than Mercury. Look southwest for the ringed planet among the stars of the Milky Way. On Nov. 19, it will sit to the upper left of a slender young moon, and Mercury will sit just to the left. The trio sets soon after the sun. On the following night, Nov. 20, Saturn will be next to a marginally larger crescent moon, with Mercury just below. Mercury will rise to be nearly even with Saturn, but then both will quickly sink toward the sun.
November's best meteor shower is the Leonids, which peaks overnight Nov. 17–18. Expect about 15 meteors an hour in fast-moving streaks. These bits of dust were left behind by Comet 55P/Tempel-Tuttle.
Speaking of comets, you might have a chance to see one this month. The All-Sky Automated Survey for Supernovae discovered a comet in July, which was named 2017 O1 ASASSN. The fuzzy-headed object, visible through binoculars or a telescope, is cruising through the constellation Camelopardalis in the northeastern sky and climbing toward the North Star, Polaris, which it will reach around Christmas. Look for a blurry patch of light floating in front of a background of stars.
There are lots of other objects to check out in this region of the sky. As you scour Camelopardalis for the comet, you may run across Kemble's Cascade, a pretty chain of stars at magnitude 5. Camelopardalis is found below the W shape of Cassiopeia and above the constellation Auriga, which has a bright flickering star named Capella.
One of the most notable fall stars, Capella sits close to the horizon at this time of year, shining through a thick cross-section of atmosphere. It flickers as it passes through Earth's wavering layers of air, making it appear to flash multiple colors and sometimes be mistaken for a UFO.
Scan east with your binoculars, into Perseus and below Cassiopeia, to find a famous grouping of stars known as the Double Cluster. Sharp-eyed viewers located at a sufficiently dark site will be able to spot the pair of clusters without magnification. They are 7,400 light-years from us and 100 light-years from each other.
Next, scan east a bit farther to reach the Andromeda Galaxy. The closest large spiral to Earth, Andromeda has a wispy oval shape with a brighter center. The light that you see left its source 2.3 million years ago. To our eyes, comets and galaxies look quite similar even though the objects are hugely different in size and location to Earth. Comet hunters were the first to catalog galaxies and note that these comet-like objects in the sky did not move over time as comets do.
Kelly Kizer Whitt has been writing about our universe for more than a decade. She is the author a number of books, including the children's book Solar System Forecast and the YA dystopian novel A Different Sky. You can follow her on Twitter @Astronomommy.
Reposted with permission from our media associate SIERRA Magazine.
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By Aaron W Hunter
A chance discovery of a beautifully preserved fossil in the desert landscape of Morocco has solved one of the great mysteries of biology and paleontology: how starfish evolved their arms.
The Pompeii of palaeontology. Aaron Hunter, Author provided<h2></h2><p>Although starfish might appear very robust animals, they are typically made up of lots of hard parts attached by ligaments and soft tissue which, upon death, quickly degrade. This means we rely on places like the Fezouata formations to provide snapshots of their evolution.</p><p>The starfish fossil record is patchy, especially at the critical time when many of these animal groups first appeared. Sorting out how each of the various types of ancient starfish relate to each other is like putting a puzzle together when many of the parts are missing.</p><h2>The Oldest Starfish</h2><p><em><a href="https://www.biorxiv.org/content/10.1101/216101v1.full.pdf" target="_blank" rel="noopener noreferrer">Cantabrigiaster</a></em> is the most primitive starfish-like animal to be discovered in the fossil record. It was discovered in 2003, but it has taken over 17 years to work out its true significance.</p><p>What makes <em>Cantabrigiaster</em> unique is that it lacks almost all the characteristics we find in brittle stars and starfish.</p><p>Starfish and brittle stars belong to the family Asterozoa. Their ancestors, the Somasteroids were especially fragile - before <em>Cantabrigiaster</em> we only had a handful of specimens. The celebrated Moroccan paleontologist Mohamed <a href="https://doi.org/10.1016/j.palaeo.2016.06.041" target="_blank" rel="noopener noreferrer">Ben Moula</a> and his local team was instrumental in discovering <a href="https://www.sciencedirect.com/science/article/abs/pii/S0031018216302334?via%3Dihub" target="_blank" rel="noopener noreferrer">these amazing fossils</a> near the town of Zagora, in Morocco.</p><h2>The Breakthrough</h2><p>Our breakthrough moment came when I compared the arms of <em>Cantabrigiaster</em> with those of modern sea lilles, filter feeders with long feathery arms that tend to be attached to the sea floor by a stem or stalk.</p><p>The striking similarity between these modern filter feeders and the ancient starfish led our team from the University of Cambridge and Harvard University to create a new analysis. We applied a biological model to the features of all the current early Asterozoa fossils in existence, along with a sample of their closest relatives.</p>
Cantabrigiaster is the most primitive starfish-like animal to be discovered in the fossil record. Aaron Hunter, Author provided<p>Our results demonstrate <em>Cantabrigiaster</em> is the most primitive of all the Asterozoa, and most likely evolved from ancient animals called crinoids that lived 250 million years before dinosaurs. The five arms of starfish are a relic left over from these ancestors. In the case of <em>Cantabrigiaster</em>, and its starfish descendants, it evolved by flipping upside-down so its arms are face down on the sediment to feed.</p><p>Although we sampled a relatively small numbers of those ancestors, one of the unexpected outcomes was it provided an idea of how they could be related to each other. Paleontologists studying echinoderms are often lost in detail as all the different groups are so radically different from each other, so it is hard to tell which evolved first.</p>
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