Observe the Sun in 3D from the past hundred years up to the present day

Egor Illarionov
Jan 23, 2018 · 6 min read

Do you know how active the Sun is today? What should we expect for tomorrow? A magnetic storm or relaxed sunlight? These are just a few questions you can answer playing with the Sun’s 3D model on a new website www.observethesun.com. Learn more about features of the website in this article!

Why we observe the Sun

About 100 ground-based observatories and 20 spacecrafts conduct daily monitoring of various aspects of solar activity. Thousands of amateur observers take photos of the Sun and publish them on the internet. Starting with Galileo Galilei, this is one of the longest series of direct physical observations. What are all these people motivated by?

Amazing solar images definitely compel attention. However, this can be a dangerous beauty. Giant flows of particles and energy ejected from the Sun stream out through the interplanetary medium and impact any planet or spacecraft in its path. Earth is just the third planet from the Sun and thus gets a huge dose of that irradiation. Sometimes it results in amazing auroras only, but the effect will be dramatic if all navigation systems, telecommunication networks and electric networks will be damaged. While we are unable to prevent solar impact, we can be prepared in advance to take appropriate actions. Developing the website observethesun.com we see our mission in providing a better tool for investigating past, current and forthcoming solar activity.

Solar activity on Sun’s 3D model

We have implemented the fully interactive 3D model of the Sun to visualize any type of solar activity tracers. Plain 2D images are from the past. We have processed thousands of these images to identify the most essential information from them and to compose a 3D map of solar activity. Rotate the Sun by any angle as if you fly it around, zoom in and out to get the detailed view.

Sunspots, filaments, plages, coronal holes, prominences and solar corona have been carefully detected for each day, measured inside and out and reproduced on the Sun’s 3D model. To learn more about each type of object read the glossary, which is also available by clicking the information button on the website near the object selection menu.

Click any object to get its key parameters, e.g. area, location, intensity etc. Scientific data is touchable as never before!

For advanced use we provide information on solar rotation. In the bottom of the webpage you can find the Carrington rotation number, heliographic longitude and latitude of the central point of the solar disk, cursor coordinates as well as Wolf’s number and total sunspot area for the selected day.

Stay updated every day

The Sun varies every day and every day observethesun.com provides you with actual data. Numbers given in the object selection menu show how many objects (active regions) of each type have been detected on the current day. The timeline at the bottom of the webpage indicates how often selected types of objects have been observed during the year. For example, you can easily find spotless days or vice versa, find days with observed sunspots. To speed up the navigation to a requested day use keyboard shortcuts. Left/right arrows change day, while shift+left/right arrows change month.

Many extreme events on the Sun are accompanied by spontaneous alteration in shape and parameters of active regions. The comparison mode helps you to trace any variations. To activate this mode double-click any active regions (for the same or different days) and click the “Comparison” button. You will find all selected objects grouped by type and following one after another.

Thus a lot of work on selection and analysis of active regions is available online without need for external programs.

Explore a 100 years of solar activity

The earliest available sunspots with observethesun.com date back to 1918 (plages are available from 1907, prominences and filaments from 1919). During the 100 years, life on Earth has changed dramatically. But what happened with the Sun? Was it active? What can we learn from its history to predict its activity for tomorrow?

Solar activity varies with about 11-year period. This cyclic nature manifests itself in almost any parameter related to solar activity. Check page Indices to see variations in sunspot numbers, plage area, intensity of corona and more. You will quickly find that a new cycle of solar activity begins in 2018 (see figure below).

Beginning of a new cycle means that in the nearest future we will observe an increasing number of prominent events on the Sun. So, stay tuned!

Start your research of the Sun

There are a lot of open questions in solar physics. Observethesun.com helps you to start research today.

All the data you will find in the website can be directly downloaded in just one click. Find the button “Download data” and click it. You will obtain a file in json format that can be parsed by almost any programming languages. Let’s get some data and make a little discovery! We will use Python for programming, the whole code can be found on GitHub.

Consider a day with a large number of active regions, say May 4, 2013. Click “Download data” to get a json file with active regions (by default only sunspots are included). Now we start coding with IPython Notebook.

Import data from local file:

JSON file contains data in pairs {key: variable}. For example, we can get the date of observation, the Carrington rotation number and the Wolf’s number by corresponding keys:

The output will be 2013, 5, 4 for the first line, 2136.61 for the rotation number and 190 for the Wolf’s number.

Now let’s retrieve coordinates of center, area and id of sunspot group for each sunspot:

You can print the first 5 lines of the obtained table with df.head() command.

An interesting question is how are sunspots distributed within the sunspot group? To give insight one can fit linear regression between longitudes and latitudes of sunspot’s centers within each group (for simplicity we forget about projection effects). Let’s group sunspot by group_id value and filter out groups with less than 2 spots:

Define a function that calculates linear regression. Note that we use sunspot areas as weight parameter for regression:

Apply regression model to grouped sunspots:

Finally we can plot sunspot centers and regression line for each group.

Consider the figure we obtain. Sunspots within each group have the same color, point size reflects sunspot area, black lines are regressions within each group.

We observe a very interesting feature. Sunspot groups in both hemispheres tend to be inclined towards the solar equator. Moreover, they are inclined in such a way that leading spots (which have larger longitude) are located closer to the equator than trailing spots. It is not occasional but a systematic behaviour known as Joy’s Law. What we obtained is a bright manifestation of this law.

Where data comes from

Several sources are exploited to fill the website with data. The main contribution consist of observations performed at Kislovodsk Mountain Solar Station. This station is located in Caucasus Mountains with a direct view to Mount Elbrus, the highest mountain in Europe. Visit the station to see it!

A view from Kislovodsk Mountain Solar Station to Mount Elbrus

Additional sources are Kodaikanal Solar Observatory, Royal Greenwich Observatory, Mount Wilson Observatory, Kanzelhöhe Observatory, Solar Dynamics Observatory and Solar and Heliospheric Observatory. All data are processed by Kislovodsk Mountain Solar Station.

What’s next

We have lots of plans on an expansion of the project and the introduction of a new functionality. In the following release you will find an incredible solar wind animation and some extra features. Join our team, find us on Facebook and let’s observe the Sun together!

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