Space

What qualifies a planet as a planet?

1. It must orbit a star

2. It must be big enough to have enough gravity to force a spherical shape

3. It must be big enough that its gravity cleared away any objects of a similar size near its orbit.

Voyager 1 & 2 (launched 1977)

• Designed to explore Jupiter & Saturn. After 35 years, it reached the edge of the solar system in 2012. They are still traveling outside our solar system in interstellar space. 

Hubble Space Telescope (HST – launched 1990)

• Primarily observed the universe in optical and ultraviolet wavelengths (with some infrared capabilities.)

• Orbits Earth. Serviced in 1993, 1997, 1999, 2002, and 2009 by space shuttle missions.

James Webb Space Telescope (JWST – launched 2021)

• Primarily looking at the universe in infrared. Due to the expansion of the universe, light from distant objects shifts to longer wavelengths at the redder end of the spectrum — known as redshift. The JWST will observe this infrared light in great detail and shed light on the oldest stars and galaxies in the universe.

• Orbits the sun. JWST will be too far away to be serviced.

 Facts

• Speed of light: 671 million mph (186,000 miles per second). (Speed of sound is 761 mph)

• Light year: 6 trillion miles.

• Fastest spacecraft: 430,000 mph (Parker solar probe). Space shuttle: 17,500 mph.

• Earth to Sun: 1AU or 93,000,000 miles.

• The next closest galaxy to the Milky Way is the Sagittarius Dwarf Elliptical Galaxy, which is about 70,000 light years away.

If you travel at the speed of light…

1.3 seconds to get to the moon

8.3 minutes to get to the sun

2,000 years to get out of the Milky Way galaxy 

If you travel at 430,000 mph...

33 minutes to get to the moon

9 days to get to the sun

39 million years to get out of the Milky Way galaxy