• There are more stars than all of the grains of sand on earth.
• There are an estimated two trillion galaxies in the universe, each with up to a trillion stars.
• Astronomers believe that the universe contains about 0.3 atoms per cubic meter of space.
• A quasar is a million times brighter than the entire Milky Way Galaxy, and a trillion times brighter than our sun.
• As late as 1820, the universe was thought by European scientists to be 6,000 years old, because they calculated the date of its formation on religious writings.  It is now calculated to be nearly 14 billion years old based on the speed of light and the distance of the farthest reaches of what our telescopes can see.
• A very massive star has a shorter life span than a less massive star.  The more massive a star, the more tightly its gravity pulls it together, the hotter it must be to keep it from collapsing, and the more rapidly it uses up its hydrogen fuel.  The most massive stars live for only about one million years.  Our sun, which is not very massive, has an expected life span of about 10 billion years – and it’s now middle-aged.
• The star Betelgeuse, a bright star in the constellation of Orion and one of our nearest astronomical neighbors, is estimated to have a diameter of around 700 million miles.  If it were placed at the center of our solar system, it would extend beyond the orbit of Jupiter.
• The Milky Way has a radius of about 100,000 light-years, or a quintillion kilometers, or 621,371,192,237,333,890 (that’s over 621 quadrillion) miles.
• Galaxy GN-z11 is the most distant object ever observed. Right now, GN-z11 is 32 billion light-years away from Earth. Because of the speed of light, astronomers estimate we see it now as it was around 13.4 billion years ago – about 400 million years after the Big Bang when the universe was relatively brand-new.  Discovered by the Hubble Space Telescope in 2016, it is located in the constellation of Ursa Major (the Big Dipper). Until Hubble is replaced with a more powerful telescope, we probably won’t see more distant galaxies.

• On a truly dark night with no light pollution, we can see that stars are different colors: blue, white, yellow, red, and brown. The color indicates the star’s temperature. The hottest (and brightest) stars are blue-white, while cooler ones are reddish-brown.
• A black hole is a region of space in which the gravitational field is so powerful that nothing, not even light, can escape.  The black hole has a one-way surface, called an event horizon, into which objects can fall, but not escape.  It is called “black” because it absorbs all the light that hits it.
• When a star explodes, we call it a supernova. The supernova is extremely bright and causes a burst of radiation that can outshine the entire galaxy before it fades over several weeks or months.  During its short existence, a supernova can radiate as much energy as the sun will emit over its entire life span. Johannes Kepler famously observed a supernova visible from Earth in 1604. That wasn’t the last supernova in our galaxy – just the last one humans saw as it happened.
• A comet’s tail always points away from the sun.
• The most common elements in the universe are hydrogen (73.9%), helium (24%). Oxygen comes in third at 1%. All the other elements in the periodic table account for less than 0.1% of all matter in the universe. And Earth has been dealing with a shortage of helium!
• Our sun and the surrounding planets orbit around the center of the Milky Way galaxy once every 250 million years.
• A billion years ago, when photosynthesis first began in our planet’s oceans, a single day on earth lasted only 18 hours.
• The earth travels over a million and a half miles per day on its journey around the sun.
• The sun burns an estimated 600 million metric tons of hydrogen every second. What happens to that hydrogen? It becomes helium.