You may have noticed a very bright star in the western sky these past few weeks, rising slowly and growing brighter. This is the planet Venus, Earth's near twin, and the hottest planet in the Solar System. It will continue rising until it reaches its maximum altitude (or eastern elongation) on the 20th of August. That it's bright goes without saying; its heavy cloud cover reflects most of the visible light that reaches it back into space, and therefore towards us.
Again, it is bright, and will simply grow brighter.
However, there are objects that cross the sky that can be, momentarily, as bright. These are satellites. It so happens that May is a great time to watch for them.
So, just how many satellites are up there, and how many are visible?
The number of satellites that are up there is in the thousands, ranging from a few centimeters or less to the size of locomotives, and one even larger. They look like moving stars; they can be distinguished from aircraft because they are normally just a single point of light. The light they reflect is not always constant, though. As satellites age and go dead, they frequently lose control and begin spinning. When they do this, they appear to pulsate depending upon the speed of their rotation. A few satellites flare up significantly, easily brighter than Venus.
The best time to observe satellites is just after sunset. Satellites can be seen moving either generally from the west to east or due north or south (polar orbits). By the way, be sure to wave at the ones in polar orbits, as many of those are reconnaissance or earth observation satellites, blistering with cameras!
The largest satellite currently in orbit is the International Space Station, the ISS. This orbiting platform covers the area of a football field and has enormous photovoltaic panels (solar panels). There are normally three people on board at any one time; this jumps when a space shuttle is docked.
The ISS in its current configuration. Image courtesy NASA
What does the ISS look like as it passes overhead?
It is brilliant. Its brilliance is already much brighter than Venus, as it slowly follows its arch across the sky. On the 13th of May, it will make a pass through our northern skies here in northeast Florida, rising in the northwest, though much later than most satellites; it will clear the horizon at 10:19pm. The pass will only last three minutes, rising just 15 degrees above the horizon, but if you have a clear shot north, you should be able to see what looks quite a bit like the planet Venus, moving up, growing brighter, then fading through yellow, orange and red as it vanishes into the night.
ISS pass on the 13th of May, 2010. Chart courtesy Heavens-Above.com
The following day, the 14th, space shuttle Atlantis is scheduled to go aloft to the ISS. Try to catch the ISS before the shuttle does!
However, there are objects that cross the sky that can be, momentarily, as bright. These are satellites. It so happens that May is a great time to watch for them.
So, just how many satellites are up there, and how many are visible?
The number of satellites that are up there is in the thousands, ranging from a few centimeters or less to the size of locomotives, and one even larger. They look like moving stars; they can be distinguished from aircraft because they are normally just a single point of light. The light they reflect is not always constant, though. As satellites age and go dead, they frequently lose control and begin spinning. When they do this, they appear to pulsate depending upon the speed of their rotation. A few satellites flare up significantly, easily brighter than Venus.
The best time to observe satellites is just after sunset. Satellites can be seen moving either generally from the west to east or due north or south (polar orbits). By the way, be sure to wave at the ones in polar orbits, as many of those are reconnaissance or earth observation satellites, blistering with cameras!
The largest satellite currently in orbit is the International Space Station, the ISS. This orbiting platform covers the area of a football field and has enormous photovoltaic panels (solar panels). There are normally three people on board at any one time; this jumps when a space shuttle is docked.
The ISS in its current configuration. Image courtesy NASAIt is brilliant. Its brilliance is already much brighter than Venus, as it slowly follows its arch across the sky. On the 13th of May, it will make a pass through our northern skies here in northeast Florida, rising in the northwest, though much later than most satellites; it will clear the horizon at 10:19pm. The pass will only last three minutes, rising just 15 degrees above the horizon, but if you have a clear shot north, you should be able to see what looks quite a bit like the planet Venus, moving up, growing brighter, then fading through yellow, orange and red as it vanishes into the night.
ISS pass on the 13th of May, 2010. Chart courtesy Heavens-Above.com