Introduction

Recently Coil user Legomaracas published excellent posts about Comet NEOWISE providing some general information about the comet itself, her own images of the comet, and more. I can read them here: (The NEOWISE Comet), (Quick NEOWISE Update).

I’d like to take a look at the Comet NEOWISE phenomenon from a different perspective and try to find the comet with the help of computer software (Stellarium in this case).

One of the reasons is that the current situation in my city (smog) will not allow me to see even a single star. And with Stellarium I can see any object. In this post, I will give a general overview of Stellarium capabilities. In some of the next post/s we will talk about more advanced features of the software.

This situation may serve as a good example for what ScienceExchange initiative is going to be about (for more information, you can read “ScienceGlobal. Scientific ecosystem on Coil. Introduction”).

We could ask Coil community some questions (in this case – “How to find Commet NEOWISE?”), and then different users could publish their posts discussing the topic in question from various perspectives.

NEOWISE

For those who don’t know yet, NEOWISE (C/2020 F3, or Comet NEOWISE) is a comet discovered recently (March, 2020) by NEOWISE mission [1]. The latter is an acronym and stands for Near-Earth Object Wide-field Infrared Survey Explorer [2].

The WISE is a NASA infrared-wavelength astronomical space telescope set in 2009 and assigned a mission to help NASA to identify / characterize near-Earth objects (NEO) in 2013.

So, it’s a name for the comet and the mission at the same time [3].

According to NASA, comets are

> cosmic snowballs of gas and dust that make sweeping orbits around our sun.

(NASA Science Live: How to Spot Comet NEOWISE)

They should not be confused with asteroids, which are

> these rocket fragments are leftovers from the beginning of our solar system.

(NASA Science Live: How to Spot Comet NEOWISE)

The latter usually can be found in the area between Mars and Jupiter, while the comets can be found in a larger area.

What makes this comet unique is the fact that we can see it with naked eyes or a binocular. The last time people saw a comet that was this bright is when there was a Comet Hale–Bopp near the Earth.

> Comet Hale–Bopp (formally designated C/1995 O1) is a comet that was perhaps the most widely observed of the 20th century and one of the brightest seen for many decades.

(source)

The comet originates from our Solar System. We can see its orbit below:

(source – Wiki; CC BY-SA 4.0; by Phoenix7777)

You can see how the purple circle (C/2020 F3) approaching the blue circle (the Earth).

The NEOWISE phenomenon shouldn’t be ignored, as we are going to see it again in something like 6800 years and is supposed to be visible till the end of July [2, 4].

Stellarium

It’s a free open source virtual planetarium we can run on our PCs. It simulates realistic 3D-sky and comes in 3 versions: PC, web- and mobile (for Android and iOS) versions.

You can download them here:

https://stellarium.org/

https://www.stellarium-labs.com/stellarium-mobile-plus/

Stellarium simulates the skies in real-time (the data are processed within milliseconds) and comes with a catalogue of near 800,000 stars (according to https://stellarium.org/) / over 1.4 Billion stars (according to https://www.stellarium-labs.com/stellarium-mobile-plus/), a catalogue of over 3 millions nebulae / galaxies (according to https://www.stellarium-labs.com/stellarium-mobile-plus/), artistic illustrations of the constellations, and more.

It can work in 3 modes, so that you can watch them with your eyes, binoculars/cameras, or a telescope.

You can find the full list of Stellarium features here, and in this post I’m going to talk about some basic ones:

a) working with date/time and location

b) searching for an object

c) navigation

d) switching between different modes (binoculars / telescope)

e) updating Stellarium’s Solar System data

We will work with PC version.

a) working with date/time and location

Launch Stellarium, and you’ll see something like:

In order to reveal toolbars with buttons at the bottom, just hover over them with your mouse cursor. Then you can fix the toolbars by clicking little triangles (bottom left).

The toolbar along the bottom (let’s call it the 1st toolbar) provides us information about time, location, some other information, and allows us to change visibility of different objects on the sky like constellations, deep-sky objects, and even atmosphere, as well as to change the time speed (yeah, with Stellarium we can travel in time).

The toolbar along the bottom-left (let’s call it the 2nd toolbar) allows us to set location, time, search for objects, set a number of program configurations, and more.

In order to set time/location, we need the 2nd toolbar.

Just click the top button on the bar (see 4 on the image) (or F6) and you’ll be presented with “Location” window.

We can set location in the search box (1). I’ll choose Buffalo (New York). Also, you can set location by moving the “down” arrow on the map (2). The panel below shows us the location information (3).

Once done, we’ll see our location information on the 1st toolbar (5) as well.

Now, to “travel” in time, we need to click the second button (1) (or F5) on the 2nd toolbar.

According to NASA

our comet

> will become increasingly visible shortly after sunset in the northwest sky

(source)

So, I chose 22:10:47 in “Date and Time” window, and left the date (currently it’s July 27, 2020).

b) searching for an object

Clicking on the 3rd button will bring up “Search” window

Here we need to enter the name of the object we’re locking for (“Neowise” in our case). As you can see, there’re two objects showed up (C/2016 U1 (NEOWISE) and C/2020 F3 (NEOWISE); both are comets). By default, if we click “search” button or press “Enter”, Stellarium will center the first object on the screen (C/2016 U1 (NEOWISE) in this case). So, instead of searching for “Neowise”, we need to search for “c/2020…”.

Once done, you’ll see the comet we’re looking for at the centre of the screen with bouncing red “target” around it. Other objects are highlighted with other colours (stars with small rotating ‘target’ around them, and the rest of the objects with a bouncing blue ‘frame’ around them).

Also, we’ll see some astronomical data on the left like the distance from the Earth/Sun (108.785 M km / 111.164 M km accordingly), core diameter (10 km), coma diameter (388000 km), gas tail length (4.18 M km), and more.

As for the comet location, according to NASA

> Just after sunset, look below the Big Dipper in the northwest sky

(source)

(image source; Credits: NASA/JPL-Caltech)

That’s where we can see our comet on the screen.

The way Stellarium shows constellations is one of the most beautiful features of this software.

Just click the leftmost buttons on the 1st toolbar.

c) navigation

Well, navigation in our planetarium is pretty intuitive.

Just use the arrow keys on your keyboard or drag the image with your mouse/touchpad.

To zoom in/out, use “Ctrl + up/down arrow key” or your mouse wheel.

Pressing the spacebar will centre the object on the screen.

Comet nature and structure

As we saw on the gif at the beginning of the post, the comet moves around the Sun. As the comet (which is mostly just a bunch of ice (water-based ice, dry ice (solid CO2), ammonia (NH3), carbon monoxide (CO))) enters the inner Solar System (near Jupiter’s orbit), it heats up, which results in 2 effects:

1. a coma / halo

> a diffuse cloud of gas and dust surrounding the nucleus of a comet

(source – Oxford Dictionary of English, 3rd Edition, Oxford University Press 2010)

2. a tail of dust (fragments of the comet itself)

[5]

Comets have 2 tails. The first one (the main/dust tail) is curved, wide and grey/white (the same colour as the comet itself), and the second one (ion tail) is blue, narrow and goes directly away from the Sun.

(source; Sergey Prokudin-Gorsky; Юкатан / Wikimedia Commons)

The reason they go in different direction and differ in diffusion and colour is that they are made of the different materials and are experiencing gravitational and Sun’s radiation forces as the comet moves (disproportionately in the case of the dust tail (which is made of the fragments different in size), and proportionately in the case of the ion tail (made of single molecules / free electrons)).

Now we can take a look on how the tails look like in our planetarium (zoomed in).

d) switching between different modes (binoculars /camera / telescope)

You can see several icons on the top tight of the screen.

To switch to telescope, just click the leftmost button, and you’ll see something like

On the telescope panel you can play with different parameters (type of the telescope, ocular and different lenses). Also you can watch the objects in binoculars /camera mode.

e) updating Stellarium’s Solar System data

I suspect in the future scientists will discover some other comets (and other objects). And to get the data for those comets, we will need to download and import them into Stellarium. That’s where “Solar System Editor” plugin comes into play.

To get there, you need to click “Configuration window” button on the 2nd toolbar and “Plug-ins” tab. Then choose “Solar System Editor“ item in the menu on the left. Click “Configure” button, then choose “Solar System” tab in the “Minor Solar System objects” window, and click ‘Import orbital elements in MPC format’.

You’ll see the “Import data” window. Select comets in the “Select the type” section and “Gideon van Buitenen: comets” in the “Select the source” section. Then click ‘Get orbital elements’ button, choose the object you need and click ‘Add objects’ button.

Coil members will get access to a video-version for this tutorial.

All Stellarium screenshots are done by me.

References:

1. NEOWISE on Wiki

2. How to See Comet NEOWISE

3. NEOWISE on NASA

4. Comet NEOWISE Streaks Across the Sky Above Lone Pine Lake

5. Why Does Comet NEOWISE Have Two Tails?

All images (without the license specified)/videos are used under the doctrine known in USA as “Fair Use” (similar doctrines are used in other countries). For more information visit *the US Gov website*.

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