What's Up - May 2016

What's Up for May. Two huge solar system highlights: Mercury transits the sun and Mars is closer to Earth than it has been in 11 years.

Hello and welcome. I'm Jane Houston Jones from NASA's Jet Propulsion Laboratory in Pasadena, California.

On May 9 wake up early on the west coast or step out for coffee on the east coast to see our smallest planet cross the face of the sun. The transit will also be visible from most of South America, western Africa and western Europe. A transit occurs when one astronomical body appears to move across the face of another as seen from Earth or from a spacecraft. But be safe! You'll need to view the sun and Mercury through a solar filter when looking through a telescope or when projecting the image of the solar disk onto a safe surface. Look a little south of the sun's Equator. It will take about 7 1/2 hours for the tiny planet's disk to cross the sun completely. Since Mercury is so tiny it will appear as a very small round speck, whether it's seen through a telescope or projected through a solar filter. The next Mercury transit will be Nov. 11, 2019.

Two other May highlights involve Mars. On May 22 Mars opposition occurs. That's when Mars, Earth and the sun all line up, with Earth directly in the middle. Eight days later on May 30 Mars and Earth are nearest to each other in their orbits around the sun. Mars is over half a million miles closer to Earth at closest approach than at opposition. But you won't see much change in the diameter and brightness between these two dates. As Mars comes closer to Earth in its orbit, it appears larger and larger and brighter and brighter. During this time Mars rises after the sun sets. The best time to see Mars at its brightest is when it is highest in the sky, around midnight in May and a little earlier in June. Through a telescope you can make out some of the dark features on the planet, some of the lighter features and sometimes polar ice and dust storm-obscured areas showing very little detail. After close approach, Earth sweeps past Mars quickly. So the planet appears large and bright for only a couple weeks. But don't worry if you miss 2016's close approach. 2018's will be even better, as Mars' close approach will be, well, even closer.

You can find out about NASA's #JourneytoMars missions at mars.nasa.gov . And you can learn about all of NASA's missions at http://www.nasa.gov

That's all for this month. I'm Jane Houston Jones.