• Neowise Comet Facts
• Comet Neowise Orbit Around The Sun

Comet C/2020 F3 NEOWISE has survived perihelion with the Sun. Because of it's orbit, this comet will visible in the morning AND evening sky for a short perio. Visualization of Comet C/2020 F3 (NEOWISE) Orbit. This 3d orbit diagram is a feature of our 3D Solar System Simulator and shows the orbit of Comet C/2020 F3 (NEOWISE) with respect of the Sun and the orbits of the major planets. The position of Comet C/2020 F3 (NEOWISE) and the planets along their orbits in this diagram accurately represents the current configuration of the objects in the Solar System.

This article was originally published at The Conversation. The publication contributed the article to Space.com's Expert Voices: Op-Ed & Insights.

Gareth Dorrian, Post Doctoral Research Fellow in Space Science, University of Birmingham

Ian Whittaker, Senior Lecturer in Physics, Nottingham Trent University

Neowise is the first bright comet to be visible with the naked eye from the northern hemisphere since the mid-1990s. Another thing that makes this comet interesting is that it has a relatively long orbital period, meaning it was only discovered a few months ago.

Halley’s comet, for example, takes about 75 years to return to the same position near Earth, meaning everybody has the opportunity to see it potentially twice during their lifetime. Neowise has an orbit of almost 6,800 years, meaning that the last generation of people to see it would have lived during the fifth millennium BC. This was a time well before the written word, when the global human population was about 40 million people.

The cause of this really long return time is the elliptical shape of Neowise’s orbit around the Sun. In the early 17th century, astronomer Johannes Kepler derived his laws of planetary motion, which apply to any object orbiting in space, including comets. These laws state that objects on highly elliptical orbits will move fast near the barycenter – the centre of mass of two or more bodies that orbit one another – of the path and much slower further away.

Related: How to see Comet NEOWISE in the evening sky right now

So comet Neowise will only be seen for a few weeks near Earth while it is near perihelion (its closest approach to the Sun). It will then spend thousands of years moving slowly near the other end of its orbit. It’s aphelion (farthest point) is estimated at 630 astronomical units (AU), with one AU being the distance between the Earth and the Sun.

To put that in perspective, the Voyager 1 spacecraft is the farthest human crafted object from Earth and it is currently at a mere 150 AU. The dwarf planet Pluto also has an elliptical orbit, which ranges from just 30 AU at perihelion to 49 AU at aphelion.

Comets often have two tails, and comet Neowise is no exception. One is made of electrically neutral material such as water ice and dust particles forming the distinct white fuzzy shape around the comet and its tail. As the Sun heats up the comet, these tiny particles are released and create a shining tail behind it.

The second tail is made from a plasma – an electrically charged cloud of gas. This shines by fluorescence, the same process that causes aurora on Earth, and is used in neon lighting. Colours can be green or blue depending on the kind of charged gas escaping from the comet. As the plasma flows away from the comet it is guided by the Sun’s magnetic field and the solar wind. This causes separation between the two tails – one being driven by the comet’s direction, and the other by the Sun’s magnetic field.

Related: Amazing photos of Comet NEOWISE from the Earth and space

How to spot Neowise

Even though Neowise is very distant from Earth, with its closest approach on July 22 being almost as far away as Mars, it is still visible in the night sky to the naked eye – hovering near the northern horizon.

The comet is estimated to currently be at magnitude 1.4 – a measure of brightness astronomers use, with smaller numbers denoting brighter objects. Venus, which is the brightest planetary object in the sky, is about -4. Comet Hale-Bopp reached a maximum magnitude of 0 in 1997 due to its exceptionally large size, while comet McNaught was visible from the southern hemisphere with a maximum magnitude of -5.5.

Neowise may get brighter over the next week, but which level of brightness it reaches will depend primarily on how much material erupts from its surface rather than the distance from the Earth. This material consists of highly reflective water ice particles from the nucleus of the comet erupting outwards, shining when they catch the sunlight.

Rich history

The history of cometary observations is extensive, making vital contributions to the development of modern astronomy, and has had quite an impact on human history. Halley’s comet, for example, was famously featured on the Bayeux Tapestry as it made an appearance in the months leading up to the Norman conquest of England in 1066 (magnitude estimated at about 1).

In the late medieval period, comets helped astronomers to fundamentally refine their understanding of the solar system. An essential component of the then standard Ptolemaic geocentric model of the solar system, which dominated astronomy for 15 centuries, mandated that the planets were fixed to a series of concentric transparent celestial spheres, with the Earth at the centre.

Even after the Copernican revolution, which put the Sun at the centre of the solar system, the celestial spheres were retained as a concept. However, in the late 1500s several astronomers, including Tycho Brahe, noted that comets with their highly elliptical orbits seemed to pass through these spheres without hindrance. These observations contributed to the eventual abandonment of the Ptolemaic system entirely, and the subsequent explanation of planetary orbits by Johannes Kepler, which is still in use today.

Important observations during the space age include the first close encounter between a comet and spacecraft. Halley’s comet was imaged from a distance of just a few hundred kilometres by the Giotto spacecraft. And in 2014 the Rosetta spacecraft became the first to orbit a comet, and deploy a lander on the surface, sending back remarkable images to Earth.

Related: The Greatest Comets of All Time

The sobering role of comets in shaping planetary evolution was also demonstrated spectacularly in 1994 when comet Shoemaker-Levy-9 collided with Jupiter

With the constant increase of light pollution in the night sky the observation of comets with the naked eye is becoming much rarer. For now, though, Neowise presents a fantastic opportunity for millions of people to see a night sky phenomenon which typically only presents itself perhaps once in a decade or more. Enjoy the view!

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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July 5, 2020JPEG

July 5, 2020MPEG

Look up toward the stars this month, and you just might spot the brightest comet to grace Northern Hemisphere skies in decades. In July 2020, comet NEOWISE (short for C/2020 F3 NEOWISE) has thrilled skywatchers in North America, in Europe, and in space. If you don’t spot the comet this time around, you won’t get another chance. It has a long, elliptical orbit, so it will be approximately 6,800 years before NEOWISE returns to the inner parts of the solar system.

The photo above and the time-lapse video below show NEOWISE as viewed from the International Space Station (ISS) on July 5, 2020. An astronaut shot more than 340 photos as the comet rose above the sunlit limb of Earth while the ISS passed over Uzbekistan and central Asia.

Neowise Comet Facts

Comet Neowise has a nucleus measuring roughly 5 kilometers (3 miles) in diameter, and its dust and ion tails stretch hundreds of thousands to millions of kilometers while pointing away from the Sun. The icy visitor was discovered on March 27, 2020, by NASA’s Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) spacecraft as the comet was headed toward the Sun. The comet made its closest approach to the Sun on July 3, and then turned back toward the outer solar system.

Comets are made of frozen leftovers from the formation of the solar system roughly 4.6 billion years ago. The masses of dust, rock, and ice heat up when approaching the Sun; as they get closer, they spew gases and dust into a glowing head and tail. Satellite data indicate the NEOWISE has a dust tail and possibly two ionized gas tails. The comet is made visible by sunlight reflecting off of its gas emissions and dust tail.

“It’s quite rare for a comet to be bright enough that we can see it with the naked eye or even just with binoculars,” said Emily Kramer, a co-investigator of the NEOWISE satellite, in a NASA Science Live webcast. “The last time we had a comet this bright was Hale-Bopp back in 1995-1996.”

July 14, 2020

The photo above shows the comet (bottom-right) on July 14, 2020, against the backdrop of a green aurora in western Manitoba, Canada. The bright streak at the top is a meteor. The purple, ribbon-like structure is an aurora-like structure called STEVE (short for Strong Thermal Emission Velocity Enhancement), a phenomenon that was recently discovered with help from citizen scientists. Donna Lach, the photographer and an avid participant in the Aurorasaurus project, observed the scene for three hours and said the comet even out-shined the brilliant aurora at times.

NEOWISE is expected to make its closest approach to Earth on July 22, passing at a harmless distance of 103 million kilometers (64 million miles). From mid-July onward, viewers can spot the comet after sunset, below the Big Dipper in the northwest sky. For best viewing, make sure to find a spot away from city lights and with a clear view of the sky. While you may be able to see it with your naked eye, you might want to bring binoculars or a small telescope.

Comet Neowise Orbit Around The Sun

Astronaut photograph ISS063-E-39888 (top) was acquired on July 5th 2020, with a Nikon D5 digital camera using an 28 millimeter lens and is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. The image was taken by a member of the Expedition 63 crew. Time-lapse animation by Sara Schmidt of the Earth Science and Remote Sensing group at NASA JSC. Aurora and comet photograph by Donna Lach, used with permission. Story by Kasha Patel.