Category Archives: Astronomy 101

One of my main goals is to try and share a bit of knowledge and understanding about the incredible universe. I have been steadily writing and posting various articles to explain and educate the masses (that’s you, dear reader!) a bit more about some of the science behind the hobby. An urban astronomer might never see most of the things we talk about here, but it’s still good to know about them.

How long is a year on Venus?

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The planet Venus takes 224.7 Earth days to orbit the Sun. This means than a Venus year is a little more than seven months long. Interestingly, Venus’ day is slightly longer than its year, and the planet revolves around its axis backwards compared to all the other planets in the Solar System, so that Venus is very close to being tidally locked. In a few hundred million years, that process will complete as tidal forces gradually slow Venus’s rotation enough … Continue reading →

How long is a year on Mercury?

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Mercury takes 88 days to orbit around the Sun, which means that one Mercury year lasts less than three Earth months. Mercury has such a short year because it is very close to the Sun. According to Newton’s Law of gravity, this means that the Sun’s gravity is much stronger at Mercury than it is for Earth, and this requires it to move a great deal faster if it is to stay in its orbit, which is why it has … Continue reading →

What is a planetary nebula?

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Planetary nebulae are clouds of dust and gas ejected from older stars as they move on to the next stage in their evolution. When a star uses up all its hydrogen fuel, and begins to burn helium, the core heats dramatically, causing the outer layers of the star to inflate dramatically. The outer layers of the star escape its gravity, and the solar wind of high energy particles and radiation accelerates the still superheated plasma out into space where it … Continue reading →

Enceladus’s geysers caused by Saturn’s gravity

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In 2005, the Cassini spacecraft, which has been exploring the system of Saturn and its satellites since 2004, discovered enormous plumes of water spewing out into space from the satellite Enceladus.  These geysers are so powerful and pump out such enormous volumes of water that they are clearly visible from space.  But until recently, it wasn’t clear where all the water was coming from, or what force was propelling it upwards so violently.The water is expelled from a geographical feature … Continue reading →

What is a globular cluster?

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Globular clusters are clusters of stars, arranged into a sphere. They contain tens of thousands of stars, packed very closely together, so that when viewed from the Earth, their core’s appear as a single glowing mass. Globular clusters are arranged in a vast spherical halo around their parent galaxy. Our own Milky Way galaxy has a little over 150 globular clusters, but larger galaxies can have many more than that. They tend to be very old – at least as … Continue reading →