{"id":14662,"date":"2018-12-16T01:22:53","date_gmt":"2018-12-16T01:22:53","guid":{"rendered":"http:\/\/www.lifeandnews.com\/articles\/?p=14662"},"modified":"2018-12-17T01:25:25","modified_gmt":"2018-12-17T01:25:25","slug":"you-may-not-even-need-a-telescope-to-see-comet-46pwirtanen-in-the-night-sky-this-month","status":"publish","type":"post","link":"https:\/\/www.lifeandnews.com\/articles\/you-may-not-even-need-a-telescope-to-see-comet-46pwirtanen-in-the-night-sky-this-month\/","title":{"rendered":"You may not even need a telescope to see Comet 46P\/Wirtanen in the night sky this month"},"content":{"rendered":"

Shannon Schmoll<\/a>, Michigan State University<\/a><\/em><\/span><\/p>\n

As comets blaze across the night sky, they can bring wonder and excitement to those watching from Earth \u2013 or even a sense of impending doom<\/a>. In the past, people debated what comets even are \u2013 an atmospheric phenomenon, a fire in the sky, a star with a broom-like tail?<\/p>\n

You\u2019ll get a chance to see which visual description you think fits best this month: Comet 46P\/Wirtanen is expected to make an appearance in mid-December that may well be visible even to the naked eye.<\/p>\n

\n
Animation of the elliptical orbit of Halley\u2019s comet. The largest blue circle represents Neptune\u2019s orbit. Comet 46P\/Wirtanens orbit only extends to the red circle, Jupiter\u2019s orbit. nagualdesign\/Wikimedia Commons<\/a> <\/span><\/figcaption><\/figure>\n

Anatomy of a comet<\/h2>\n

Through Edmond Halley\u2019s study in the 17th century<\/a> of what became known as Halley\u2019s comet, astronomers realized comets are within our solar system. They have highly elliptical or elongated orbits<\/a> around the sun. Some have orbits that extend well beyond Pluto while some stay relatively close.<\/p>\n

\n \"\"<\/a>
\n Comet 67P\/Churyumov\u2013Gerasimenko, taken by the Rosetta Mission Sept. 19, 2014. Rosetta\u2019s original target was 46P\/Wirtanen, but NASA missed the deadline to launch in time.<\/span>
\n ESA\/Rosetta\/NAVCAM<\/a>, CC BY-SA<\/a><\/span>
\n <\/figcaption><\/figure>\n

When comets are farther out in the solar system, they\u2019re not much to look at. They\u2019re often compared to dirty snowballs. But unlike a rocky asteroid, a comet also has volatile frozen gases such as methane, carbon monoxide, carbon dioxide and ammonia<\/a> along with their nucleus of rock, ice and dust.<\/p>\n

As a comet gets closer to the sun, heat causes the comet\u2019s volatile elements to turn from solid into gas in a process called sublimation<\/a>. As water, methane, carbon dioxide, and ammonia are released, it creates the tail comets are known for, as well as a bright cloud called a coma around its nucleus.<\/p>\n

\n \"\"<\/a>
\n Comet Hale-Bopp has a blue ion tail as well as a curved dust tail.<\/span>
\n Astronomy For Beginners, Andy Roberts<\/a>, CC BY<\/a><\/span>
\n <\/figcaption><\/figure>\n

Comets actually have two distinct tails<\/a>: one a dust tail, the other an ion or gas tail. Solar wind and radiation pressure push the tails away from the sun. Ultraviolet light ionizes some of the tail material, creating a charged gas that interacts with the charged solar wind and ends up pointing directly away from the sun. The noncharged dust tail still follows the comet\u2019s orbit, resulting in a more curved tail.<\/p>\n

As a comet goes through this process, it will brighten, making for a great show for stargazers \u2013 or rather, cometgazers. Predicting how bright a comet will be is notoriously difficult<\/a> though, since it\u2019s never clear exactly how the gases will behave. Even measuring the brightness is tricky. Unlike the way a star\u2019s brightness is concentrated into a single point from our perspective on Earth, a comet\u2019s brightness is diffused<\/a> over a larger area.<\/p>\n

A visit from 46P\/Wirtanen<\/h2>\n

Astronomer Carl Wirtanen discovered<\/a> his namesake comet in 1948. He was a skilled object hunter and used photos of the night sky to spot the quickly moving object, at least astronomically speaking. <\/p>\n

Comet 46P\/Wirtanen\u2019s orbit keeps it pretty near to the sun. Its aphelion, or farthest point from the sun, is about 5.1 astronomical units (AU)<\/a>, which is just a tad bigger than Jupiter\u2019s orbit. Its perihelion, or closest approach to the sun, is about 1 AU, just about the Earth\u2019s distance from the sun. This path takes about 5.4 years<\/a> to complete, meaning it comes back into view quite frequently compared to other famous comets. <\/p>\n

Right now, it is approaching its perihelion. Its closest point to the sun will fall on Dec. 16 \u2013 which is why it will be brightest on this day.<\/p>\n

Comet 46P\/Wirtanen is a particularly active comet \u2013 called a hyperactive comet<\/a> \u2013 and tends to be brighter than other comets of a similar size. This makes it a good candidate for viewing. Predictions suggest it will be as bright as a magnitude 3<\/a>, which is a little brighter than the dimmest star in the Big Dipper, Megrez. However, there are some predictions that keep it beyond naked eye visibility<\/a> at a brightest magnitude of only 7.6. The dimmest object visible with the naked human eye is magnitude 6, under perfect observing conditions.<\/p>\n

If those magnitudes seem a little off, it\u2019s because astronomers use a backwards system. The smaller the number, the brighter the object<\/a>.<\/p>\n

To try to see this comet, get to as dark a sky as you can on Dec. 16, when it will be at its brightest. It will be between the constellation Taurus and the Pleiades star cluster<\/a>. <\/p>\n

\n \"\"<\/a>
\n The plus sign indicates where you can spot Comet 46P\/Wirtanen the evenings of Dec. 14 through 19. The plot is set for one hour after sunset for a latitude between 40-90 degrees.<\/span>
\n John French<\/span>, CC BY-ND<\/a><\/span>
\n <\/figcaption><\/figure>\n

If you cannot see Comet 46P\/Wirtanen with your naked eye, use binoculars or a small telescope to catch a glimpse. The comet is already in the sky, but requires a telescope. You can start following now using maps showing its position night by night. Its location in the sky also means it is visible for all but Earth\u2019s extreme southernmost latitudes.<\/p>\n

The comet\u2019s position near Taurus makes it ideal for spotting all night long. Taurus is just in the east after the sunset and moves toward the west throughout the night. <\/p>\n

May you have clear skies for observing. You can decide for yourself whether this comet will be an omen of good or bad luck for 2019.\"The<\/p>\n

Shannon Schmoll<\/a>, Director, Abrams Planetarium, Department of Physics and Astronomy, Michigan State University<\/a><\/em><\/span><\/p>\n

This article is republished from The Conversation<\/a> under a Creative Commons license. Read the original article<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

Shannon Schmoll, Michigan State University As comets blaze across the night sky, they can bring wonder and excitement to those watching from Earth \u2013 or even a sense of impending doom. In the past, people debated what comets even are \u2013 an atmospheric phenomenon, a fire in the sky, a star with a broom-like tail? […]<\/p>\n","protected":false},"author":44,"featured_media":14656,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[3410],"tags":[218,219,5613,5615,3936,5614,187,3938,2913],"_links":{"self":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/14662"}],"collection":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/users\/44"}],"replies":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/comments?post=14662"}],"version-history":[{"count":1,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/14662\/revisions"}],"predecessor-version":[{"id":14663,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/14662\/revisions\/14663"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/media\/14656"}],"wp:attachment":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/media?parent=14662"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/categories?post=14662"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/tags?post=14662"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}