Articles About Planets (7)
![Astronomy Glossary - Terms & definitions Astronomy Glossary - Terms & definitions](http://webcf.waybackmachine.org/web/20210812044847im_/https://c.tadst.com/gfx/150x84/fbimage-glossary--astronomy.png?1)
Astronomical Glossary - Terms & Definitions
What do astronomers really mean when they use those technical terms?
![Illustration of altitude and azimuth in the celestial sphere.](http://webcf.waybackmachine.org/web/20210812044847im_/https://c.tadst.com/gfx/150x84/horizontal-coordinate-system.png?1)
Altitude & Azimuth: The Horizontal Coordinate System
Learn how to use altitude (elevation) and azimuth angles to locate any object in the sky, such as stars, planets, satellites, the Sun, or the Moon.
![Illustration image](http://webcf.waybackmachine.org/web/20210812044847im_/https://c.tadst.com/gfx/150x84/mercury-transit.png?1)
Mercury Transit
When Mercury transits the Sun, you can see it as a tiny black dot silhouetted against the Sun's disk. The last Mercury transit was on November 11, 2019.
![Illustration image](http://webcf.waybackmachine.org/web/20210812044847im_/https://c.tadst.com/gfx/150x84/venus-transit.jpg?1)
Transit of Venus: June 5-6, 2012
The 2012 Venus transit was the last chance to see this phenomenon for over 100 years. Mercury transits happen more often, the next one in 2032.
![Illustration image](http://webcf.waybackmachine.org/web/20210812044847im_/https://c.tadst.com/gfx/150x84/mars-venus-jupiter-27oct.png?1)
Jupiter and Venus Closest Conjunction of 2015
From time to time, some of the planets in our solar system are in conjunction and become visible together in the sky. Venus, Jupiter, Mars, and Mercury have all been visible in the early mornings of October 2015.
![An image of the solar system showing the alignment of the Earth, Jupiter, and Saturn for the Great Conjunction of 2020.](http://webcf.waybackmachine.org/web/20210812044847im_/https://c.tadst.com/gfx/150x84/great-conjunction-2020.png?1)
What Is a Conjunction?
A conjunction is when planets like Mars, Jupiter, or Saturn, or other bodies like stars or the Moon, meet in the sky. Why and when do conjunctions happen?
![Screenshot of timeanddate.com's Night Sky Map for December 21, 2020, shortly after sunset in the northern hemisphere.](http://webcf.waybackmachine.org/web/20210812044847im_/https://c.tadst.com/gfx/150x84/night-sky-map-great-conjunction.jpg?1)
Great Conjunction 2020
In December 2020, Jupiter and Saturn met in the sky in a rare Great Conjunction.