Solar system

The Sun

Below is Sun 9.11.2011. Sun is a star. Its diameter is 1.39 million kilometers. Distance from Earth is 150 million kilometers. Mass is 333000 times mass of the Earth. Sun makes one rotation in 28 days. Composition: 73.4% hydrogen, 24.9% helium, 0.77% oxygen, 0.29% carbon, 0.16% iron and other elements with smaller amounts. Sun has dark sunspots. There the magnetic field is so strong that it slows down the movement of gas and makes it cooler. The temperature in the surface of sun is 6000 degrees Celsius and in the sunspot it is 5000 degrees. In the core of Sun the temperature is 14 million degrees and the pressure is 225 billion atmospheres. Sun produces energy with the fusion reactions of atoms.

Development of sunspot group 3664-3668 during May 2024. Telescope Celestron 11.

Development of sunspot group AR 3780 in August 2024. Telescope Celestron 11.

Changes in Sunspots during five days, 9-13th of September 2021. NASA Solar Dynamics Observatory image on same region in X-ray range, shows the magnetic field lines.

Large sunspot groups , AR 2993 ja 2994, 19-25th of April 2022.

Partial Solar eclipse 20.3.2015. The Moon transits the Sun. Images taken in Riihimäki, Finland. Telescope was SkyWatcher 80/600 ED. Camera Canon EOS 550D

Below is Sun with NASA and JAXA space probes.

Planets

Planets of the solar system from Mercury to Pluto. In this image on the left the planets are as they can be seen through the telescope. On the right planets are imaged by NASA and ISRO space crafts. Mercury has been imaged during day time when Sun was shining on the sky. To see Uranus and Neptune you need binoculars. Pluto has been classified as dwarf planet.

Scales in the solar system. Also the largest moons of the planets and asteroid Ceres is included in this scale image.

Mercury

Mercury planet is always a difficult target to observe and photograph from Finland. It is low in horizon after sunset, so that the turbulence of the atmosphere makes the image blurry. In april 2022 images below Mercury is imaged half hour after sunset in the evening sky. Images are video stacks with Autostakkert 3. In 2012 and 2020 images Marcury has been spotted from day sky. Mercury has no atmosphere. It rotates around its axis very slowly, in 59 days. On day side temperature is +467 degrees Celsius and in night side -173 degrees.

Below Mercury is transiting the Sun 9th of May 2016. Telescope Celestron 8. Camera Canon EOS 60Da.

Venus

Venus has a thick atmosphere consisting of mainly carbon dioxide. Surface temperature is +460 degrees Celsius. The surface is covered with volcanoes and lava flows. Part of the volcanoes may be active even today. Below is Venus in spring 2020. The image 26th of May was taken in the middle of the day when Sun is shining.

Below is Venus Transiting over sun 6th of June 2012.

Venus in January - March 2025. Image 16th of March was taken from mid-day sky.

The Earth

The Earth and Mars planets are in zone of life in solar system. Average temperature on Earth is +15 degrees Celsius. Range -80..+50 degrees Celsius. When life evolved on Earth the cyanobacteria, algae and plants converted the atmosphere of the Earth to contain Oxygen. This made possible the development of Oxygen breathing animals. Earth has actively moving continental shelves. They have strong influence to conditions on Earth in millions years scale.

Mars

Mars has thin atmosphere consisting mainly carbon dioxide. Pressure is 0.6% of Earth pressure. Mars was for 2 to 3 billion years after birth of solar system a planet with oceans and thicker atmosphere. Now the surface of Mars is mostly dry and the water is mixed to the soil, both as water and as ice. The average temperature on Mars is -63 degrees Celsius. But in equator the day temperatures are +10..20 degrees Celsius. The gravity on surface of Mars is 38% of the Earth gravity. The day at Mars takes 24 hours and 40 minutes. The year on Mars is 686 days. The rotation axis of Mars has 25 degrees tilt, so there are yearly seasonal changes on Mars. Mars, the god of war, has 2 small moons: Phobos(=Fear), diameter 22 kilometers and Deimos(=Horror), diameter 12 kilometers.

Surface features of Mars during five nights in September and October 2020. The South polar cap is well visible. It is now small and has released large amounts of water vapor to atmosphere. As consequence the large dark areas cover now larger area of southern Mars.

Mars and moon Deimos in January and February 2025.

Rotation of Mars 13th of February 2025.

Mars on the sky close to Pleiades M45 , 8th of March 2021. For naked eye Mars has clearly red color.

Jupiter

Jupiter is the largest planet of the Solar system. It has a thick atmosphere consisting mainly hydrogen and helium. The atmosphere gets thicker as you go deeper. Jupiter has 4 large moons: Io, Europa, Ganymede and Callisto. Io has active volcanoes and its colors are produced by sulfur compounds. Diameter is 3642 kilometers. Europa has under ice cover a deep ocean covering the whole moon. Diameter of Europa is 3120 kilometers. Totally Jupiter has 67 moons.

Below is Jupiter with Celestron 11 telescope 12th of October and 21st of August 2024. Also Jupiter's moon Ganymede was visible as surface object. Diameter of Ganymede is 5262 kilometers.

Rotation of Jupiter 12th of September 2024. In animated gif image below we see the rotation of Jupiter in 35 minutes. The great red spot is on up left. Images taken in morning 4:11-4:46 local time.

In image below, 30th of December 2024, the Ganymede and Io moons are visible as surface objects.

Jupiter in January - March 2025.

Saturn

Saturn is also a gas planet. The rings of Saturn are just 20 meters thick and are composed of water ice. Telescope Celestron 8. Camera Canon EOS 60Da. Saturn's moon Titan has a thick atmosphere consisting nitrogen and methane. On surface there is methane lakes in -180 degrees Celsius temperature. Titan is the largest moon in the solar system. Diameter is 5152 kilometers. Titan may have liquid water underground.

Saturn 27th of July 2024, with Celestron 11 telescope. Saturn was 21 degrees above horizon.

Saturn and its 6 largest moons 16th and 18th of January 2025. Images taken with Celestron 11 telescope in Kirkkonummi. In bottom row are the moons with NASA Cassini spacecraft.

Uranus, Neptune and Pluto

Uranus and Neptune are gas planets. Diameter of Uranus is 51 118 kilometers. Diameter of Neptune is 49 572 kilometers. Dwarf planet Pluto is a system of 6 bodies. The specific blue tone colors of Uranus and Neptune are visible.

Comets

Comet Lovejoy 2015, Garradd 2011, PanStarrs 2013. Lovejoy on the left in constellation of Andromeda 8.2.2015 with 400mm tele objective. On the middle 15.3.2015 in constellation of Cassiopeia, with Celestron 8 F6 focus. Comets are 'dirty snowballs'. When they come close to sun they melt and vaporize. The water vapor makes a long tail behind the comet.

Comet Thuchinshan-ATLAS C/2023 A3, imaged in Kirkkonummi, Finland 15th of September 2024. When images were taken the distance to Earth was 73 million kilometers. The length of the tail in sky is about 15 degrees in the image. That is at least 19 million kilometers in distance of the comet.

Comet C/2025 A6 Lemmon 16th of October 2025 17:30 Universal Time. Telescope was TS Photon 200/800. This comet comes from far away, it reaches 220 AU, 33 billion kilometers, away from the Sun. One orbit takes 1150 years, so it comes back again year 3175.

Comet Atlas C/2019 Y4 in March and April year 2020.

Comet Atlas moving on the sky during 32 minutes, 29th of March 2019. With speed 34 kilometers per second, it moves here during 32 minutes 65300 kilometers, which is one sixth of the distance between Earth and Moon.

Comet C/2022 E3 (ZTF) in January and February 2023. Last time this comet visited inner solar system 50000 years ago. The distance of this comet to Earth was 51 million kilometers. In the sky it was moving about 5 angular degrees in a day and in space 118000 kilometers in hour, which is 33 km/s. Green color is caused by diatomic carbon and syanogen. This comet is closests to sun with 1.1 AU distance and when in Oort cloud, 2800 AU.

Asteroids

Asteroids orbit the Sun between orbits of Mars and Jupiter. There is thousands of asteroids. Largest of them is Ceres, diameter 1000 kilometers. Vesta is second largest, 560 km in diameter. You can see these with binoculars.