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. 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.

Additional Information

An orrery is a model of the solar system that shows the positions of the planets along their orbits around the Sun.

The chart above shows the Sun at the centre (the yellow ball), surrounded by the solar system's innermost planets.

Click and drag the chart to rotate the camera angle, or use your mouse wheel to zoom in and out. Alternatively, you can use the slider below the chart to adjust the zoom level. As you zoom out, the solar system's outer planets – Jupiter, Saturn, Uranus and Neptune – will come into view.

The date slider lets you move forwards or backwards by a few months to see the motion of the planets along their orbits over time.

The top panel shows where the planets appear in the night sky, as seen from the Earth. The yellow line marks the zodiac – the annual path of the Sun across the sky – and the grey lines show constellation boundaries.

The color coding of the orrery indicates the time of day when each planet is visible. This depends on the direction in which the planet lies, as seen from the Earth. If our line of sight to a planet is widely separated from our sight-line to the Sun, the planet will be easily visible for much of the night. If not, the planet will appear very close to the Sun.

Areas of the chart above which are shaded green are easily visible from the Earth; areas which are red are hidden by the Sun's glare. Areas which are dark blue are visible in the morning sky, while areas which are light blue are visible in the evening sky. This color coding can be turned off by deselecting the option 'Overlay planet visibility'.

By selecting the option 'Mark perihelion / aphelion', labels can be added which mark the closest and further points from the Sun along the orbits of each of the planets. The Earth's orbit is additionally labelled with the points it passes on the first day of each month as it makes its annual circuit around the Sun.

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

Neowise Orbit Map

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

Ian Whittaker, Senior Lecturer in Physics, Nottingham Trent University

Neowise Orbit Image

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.

Neowise Orbit Map

Related: The Greatest Comets of All Time

Comet Neowise Orbital Period

Comet Neowise Orbit

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.

How Long Is Neowise Orbit

Follow all of the Expert Voices issues and debates — and become part of the discussion — on Facebook and Twitter. The views expressed are those of the author and do not necessarily reflect the views of the publisher.