Complete Archive of the Daily (Bad) Astronomy Factoids “BAFacts”

The entire universe in blog form
Jan. 4 2013 12:42 PM

The Year in (Bad) Astronomy Facts

On Jan. 4, 2012, I started something new: posting daily astronomy facts short enough to post on Twitter (that is, in fewer than 140 characters). I’m the kind of guy who needs deadlines to get things done, so this seemed like a fun way to put together an interesting stream of facts for folks who follow me on Twitter (as well as Google+). It was quite a marathon; the first couple of hundred were pretty easy, but it became tougher than I expected to find new things to say as time went on!


Hopefully, though, they stayed fresh and interesting. I tied quite a few to events that were happening at the time, and I included links for more information. I started on Jan. 4 because that was the date (in the United States) of perihelion that year, when the Earth was closest to the Sun in its orbit. As astronomical milestones go, that’s a pretty good one. Due to the vagaries of physics and our calendar, though, perihelion in 2013 was on Jan. 2, so I decided to add a couple more just to get to a full year.


Below are all 367 BAFacts—365 for the year, plus one because it was a leap year, plus one more for Jan. 4, 2013. They appear just as they did in my tweets, with the hashtag #BAFacts before each one (hashtags are used on Twitter to categorize tweets) and a shortened link at the end for more info. NOTE: A couple of them were later corrected, which is duly noted. I also totally forgot to post one on Dec. 6, 2012, so I added one in here. Think of it as a bonus!

The BAFacts Archive



#BAFact: At 01:00 GMT tonight, the Earth is closest to the Sun for the year: 147,097,207 km.

#BAFact: There are no green stars.

#BAFact: While there aren’t green stars, there *are* green objects in space!

#BAFact: When 3 celestial bodies align, like in an eclipse, it’s called a “syzygy”. That's 23 pts in Words w/ Friends!

#BAFact: Earth has aurorae, but other planets do too. For Jupiter, its moons play a role:

#BAFact: It would take almost 9 years to walk to the Moon. If there were a road 400,000 km long.

#BAFact: There are 88 official constellations, the same number as keys on a piano. To know them all, you’d better C#.

#BAFact: There’s no real definition of how far over your head the sky starts.

#BAFact: On the surface of a neutron star, the gravity is so strong you’d weigh several *billion* tons.

#BAFact: There are hundreds of billions of planets in our galaxy. Hundreds of *BILLIONS*!

#BAFact: Four planets in the solar system have rings: Jupiter, Saturn, Uranus, and Neptune.

#BAFact: Mars is red due to the presence of large amounts of iron oxide: rust!

#BAFact: Over 500 people have flown into space - about 0.000007% of the world’s population.

#BAFact: The common definition of where “space” starts - the Kármán line - is 100 km above Earth’s surface.

#BAFact: Websites are dark today to protest SOPA. The Universe is dark because it’s not infinite.

#BAFact: The first stars in the Universe formed about 400 million years after the Big Bang.

#BAFact: The Earth is warming up.

#BAFact: Cumulatively, astronauts have spent more 77 years in space: about a human lifetime.

#BAFact: Every time a comet goes around the Sun, it dies a little bit.

#BAFact: The Earth is 3.7x the Moon’s diameter, 50x its volume, and 81x its mass.

#BAFact: A green aurora is due to electrons recombining with oxygen atoms high in the air.

#BAFact: The Moon does not cause major – or even moderate - earthquakes.

#BAFact: Brown dwarfs aren’t brown. They’re red. Really, really red.

#BAFact: If you stand on your tiptoes, the horizon is about 5 km (3 miles) away.

#BAFact: Pluto is smaller than our own Moon, yet has (at least) four moons of its own.

#BAFact: The core of the Sun is 15 million degrees Centigrade - that’s 27 million degrees F.

#BAFact: By combining three equations, you can describe the overall evolution of the Universe.

#BAFact: The Moon orbits the earth at a velocity of about 1 km/sec, roughly as fast as a rifle bullet.


#BAFact: In 1st moments after the Big Bang, only hydrogen, helium, & a dab of lithium were made. Everything else came later.

#BAFact: A complete cycle of day and night is called a nychthemeron. How about that?

#BAFact: 158 known gorgeous stellar beehives called globular clusters orbit our galaxy.

#BAFact: Dry ice evaporating on the surface of Mars in spring can trigger avalanches, and we have pictures!

#BAFact: Impacts can eject material that makes long lines of secondary impacts called crater chains.

#BAFact: Most asteroids are shaped like potatoes. Kleopatra is shaped like… a dog bone.

#BAFact: Centrifugal force is just as real as centripetal acceleration. It depends on your view.

#BAFact: Many comets have two tails: one dust, one gas. And they’re different colors!

#BAFact: Astronomers have seen a star eaten by a black hole.

#BAFact: The background glow of the Big Bang can still be seen, even after 13.73 billion years.

#BAFact: Venus may still have active volcanoes on its surface.

#BAFact: Saturn has weird moons. Iapetus is shaped like a walnut.

#BAFact: Saturn has weird moons. Hyperion is like a Styrofoam ball that’s been punched a zillion times.

#BAFact: Saturn has weird moons. Mimas is the Death Star.

#BAFact: Saturn has weird moons. Mimas looks like Kenny.

#BAFact: Saturn has weird moons. Mimas looks like Pac-Man.

#BAFact: Saturn has weird moons. Every four years, Janus and Epimetheus swap orbits!

#BAFact: Saturn has weird moons. Some of the water erupting from geysers on Enceladus falls on Saturn.

#BAFact: The fastest-rotating pulsar known, PSR J1748-2446ad, spins faster than the blades in a kitchen blender!

#BAFact: Today is the 50th anniversary of the 1st American to orbit Earth. But not the 1st human.

#BAFact: Satellites sometimes see solar eclipses too

#BAFact: From space, you can see a crescent Earth. And it’s as beautiful as you expect it to be.

#BAFact: After galaxies collide, long streamers of gas can stretch between them like cosmic tentacles.

#BAFact: Space is big. I suspect that's why they named it that. #Seriously

#BAFact: Venus is bright enough to see during broad daylight. And today is a great chance to try!

#BAFact: Sunspots are dark in visible light, but can be extremely bright in ultraviolet.

#BAFact: It’s very rare for an object in space to be a perfect sphere. But some things come close.

#BAFact: The stars may seem fixed on the sky, but if you watch *very* carefully you’ll see their motion.

#BAFact: The disk of the Milky Way is warped. In fact, many spiral galaxy disks are!


#BAFact: Much like humans, when stars are babies they blow gas out of both ends.

#BAFact: Venus is bright enough to cast shadows. So is Jupiter!

#BAFact: The rising Moon’s shape can be squished and massively distorted by Earth’s air.

#BAFact: Lightning storms have been spotted on Saturn… that last for nearly a year.

#BAFact: Red dwarf stars are dim, cool, and dinky. But sometimes they erupt with HUGE flares.

#BAFact: Most galaxies in the Universe live in clusters. The Coma Cluster has over 1000 galaxies!

#BAFact: A solar explosion called a coronal mass ejection can blast out a billion tons of subatomic particles.

#BAFact: Ice crystals in the air can project a lovely ring around the Sun or Moon, called a halo.

#BAFact: Some of the closest stars known are so faint they’re invisible to the naked eye.

#BAFact: Saturn doesn’t have one ring: it has *thousands*.

#BAFact: The structure of the Universe is foamy, and some galaxies sit on the edge of a void.

#BAFact: Tonight, Venus & Jupiter are just 3 degrees apart at sunset. They’re the 3rd & 4th brightest natural nighttime objects.

#BAFact: Why does the Moon look so huge on the horizon? It’s an illusion!

#BAFact: As the Earth orbits the Sun, the line dividing day and night – the terminator  –  changes its angle.

#BAFact: From Pluto, the Sun is fainter than it is from Earth, but still can be 450x brighter than the full Moon.

#BAFact: From Pluto, the Sun is so far away it would be a point in the sky like an incredibly bright star.

#BAFact: All the iron in your blood and all the calcium in your bones were created in exploding stars.

#BAFact: It took Apollo over 4 days to get from the Earth to the Moon. Their radio transmissions made it back in 1.3 seconds.

#BAFact: Tonight’s the spring equinox! Can you stand a broom on end? Yes, just like EVERY OTHER DAY.

#BAFact: Jupiter's moon Io is more geologically active than Earth. Volcanoes constantly erupt there!

#BAFact: As stars orbit the galaxy, they can plow through interstellar dust and create huge shock waves.

#BAFact: The Earth is hit by more cosmic debris than the Moon is, but erosion destroys the evidence here.

#BAFact: Some galaxies are cannibals. They eat other galaxies and grow huge.

#BAFact: Not all telescopes are on the ground or in space. SOFIA is inside an airplane with a hole in the side!

#BAFact: The red supergiant Betelgeuse will explode someday, but it’s too far away to hurt us.

#BAFact: Betelegeuse will explode one day. Maybe tonight, or maybe a million years from now.

#BAFact: Betelgeuse isn’t the nearest star that can go supernova. That honor goes to Spica.

#BAFact: If your eyes could see into the far-infared, Betelgeuse would look blue.

#BAFact: Our Sun has dark sunspots, but bright hot spots have been detected on Betelegeuse.

#BAFact: Betelgeuse will someday explode, but until then it’s blowing out a dense wind of gas.

#BAFact: One of the constituents of the red supergiant Betelegeuse? Sand.


#BAFact: Time travel is certainly impossible; otherwise my future self would stop me from tweeting thi

#BAFact: The Universe is expanding! And we know how fast: 74.2 ±3.6 km/sec/megaparsec.

#BAFact: A different way of measuring the Universe’s expansion gets 73.8 +/-2.4 km/sec/megaparsec.

#BAFact: Not only is the Universe expanding, the expansion is accelerating!

#BAFact: A single exploding star can be so bright it can be seen across 13.14 billion light years! Maybe.

#BAFact: The most distant object ever seen is a galaxy at an ego-crushing distance of 13.2 billion light years.

#BAFact: V445 Puppis is a binary system where the two stars will eventually coalesce and explode.

#BAFact: The least massive stars in the Universe, red dwarfs, may have lifespans of a trillion years.

#BAFact: Other planets get hurricanes too. Jupiter’s are bigger than the Earth!

#BAFact: If you miss the Transit of Venus on June 6, you won’t see another until December 2117.

#BAFact: Neptune, like Earth, is blue. But Neptune's color is from methane, which absorbs red light.

#BAFact: Geysers on Enceladus blow out 250 kg of water per second. It’ll run out in 13 billion years.

#BAFact: Sunspots grow and morph over time as the Sun’s magnetic field changes strength and shape.

#BAFact: The Earth was formed when the Universe was almost exactly 2/3 its present age. We've been around for 4.56 billion years.

#BAFact: Tonight Saturn is at opposition: as close as it gets to Earth this year, and the best time to see it.

#BAFact: All the planets in the solar system have moons except Mercury and Venus, the two closest to the Sun.

#BAFact: Space Shuttle Discovery flew 39 missions for a total of nearly 240 million kilometers.

#BAFact: Sunspots erupt in solar flares when tangled magnetic field lines explosively release their energy. Bang!

#BAFact: Some people say the Moon orbits the Sun more than it does Earth, but really, it’s *our* Moon.

#BAFact: Physicists use a unit of area called a barn, equal to 10^(-28) square meters, about the size of a uranium nucleus.

#BAFact: Jupiter's moon Io was the first body other than Earth seen to have active volcanism.

#BAFact: Pluto’s getting redder.

#BAFact: Even Hubble can’t see the Apollo landers. They’re too small.

#BAFact: Hubble Space Telescope once observed *the Sun*!

#BAFact: Telescopes are referred to by their mirror/lens diameter, so Hubble is a 2.4 meter 'scope - about 8 feet.

#BAFact: In 2008, a gamma-ray burst 7.5 billion light years away was visible to the naked eye!

#BAFact: The farthest object most people can see is the Andromeda Galaxy, about 2.5 million light years away.

#BAFact: Ripples in the fireball from the Big Bang are still visible. They tell us what it was like back then.

#BAFact: The oldest star ever found was born just 500 million years after the Universe itself!

#BAFact: The debris flying out from titanic supernova explosions can be seen to expand even as we watch.


#BAFact: Ice crystals in the air can project a lovely ring around the Sun or Moon, called a halo.

#BAFact: In 2011, a spacecraft orbiting Mars watched a Martian moon partially eclipse Jupiter!

#BAFact: In 2008, a spacecraft orbiting Mars took a picture of home.

#BAFact: The biggest galaxies in the Universe have over a *trillion* stars!

#BAFact: How far would you hold a dime from your eye to match the Moon’s size? Guess again: it’s 6 feet!

#BAFact: Material at the center of the Sun is so compressed that it’s 150 times denser than water.

#BAFact: In interstellar space, on average there's just one particle per cc (a bit smaller than a six-sided die).

#BAFact: An easy way to remember the number of seconds in a year: pi x 10 million. Accurate to better than 0.5%.

#BAFact: When galaxies collide, their mutual gravity can draw out long tendrils of gas from each other.

#BAFact: An asteroid hitting Mercury releases 60% more energy than it would on Earth. Why? Speed.

#BAFact: Sunspots are where the Sun’s magnetic field won’t let cool gas sink, like a clogged drain.

#BAFact: If you lived on Pluto, the United States wouldn't even be one year old.

#BAFact: A supernova has to be less than about 75 light years away to hurt us. No star that close can explode, so we're OK.

#BAFact: The nearest star that can go supernova is Spica - it’s 260 light years away, so we’re safe.

#BAFact: The Sun cannot go supernova. A single star needs to be about 8x the mass of the Sun to explode.

#BAFact: Low mass stars *can* go supernova… but they need the help of a companion.

#BAFact: Merging white dwarfs can form a neutron star, triggering a supernova.

#BAFact: The nearest star(s) to Earth that can go supernova is(are) IK Peg, at 150 light years away!

#BAFact: An exploding star can fling away its octillion-ton core 100s of times faster than a rifle bullet!

#BAFact: Sunspots look small, but only because the Sun is huge. Many are far larger than the entire Earth!

#BAFact: The coolest brown dwarf found is actually about room temperature!

#BAFact: The first exoplanets discovered were found in 1992, circling the ultradense cinder of a supernova.

#BAFact: The 1st confirmed planet found around a Sun-like star was 51 Peg b in 1995. Now we know of 700+!

#BAFact: There may be hundreds of billions of planets in our galaxy alone!

#BAFact: For every planet orbiting a star, there may be several rogue planets plying interstellar space.

#BAFact: Despite the huge number of possible rogue planets, the chance of one coming close to us is teeny.

#BAFact: A single big solar flare can put out 10% as much energy as the rest of the Sun combined.

#BAFact: More massive stars live shorter lives. The most massive may only live for a few million years.

#BAFact: Historically, transits of Venus across the Sun's face were used to gauge the size of the solar system.

#BAFact: A transit is like a mini-eclipse. We see the dark side of Venus, silhouetted against the bright Sun.

#BAFact: When Venus transits the Sun, it will look like a tiny dot: the Sun will appear to be 30X times wider than the planet.


#BAFact: Venus. Temperature = 460C. Air pressure = 90 X Earth. Rain = sulfuric acid. Nice place.

#BAFact: Hubble observed Venus only once, and had to break a safety rule to do it.

#BAFact: Venus’ orbit is tilted a bit with respect to Earth’s. That’s why we don’t see a transit every orbit.

#BAFact: Transits of Venus occur in pairs 8 years apart. But each pair is separated in time by >1 century!

#BAFact: If you miss today’s transit of Venus, you’ll have to wait until December 10, 2117 for the next.

#BAFact: Martian winds can create dust devils, mini-tornadoes towering hundreds of meter over the landscape.

#BAFact: IC 342 would be one of the most spectacular galaxies in our sky if it weren’t obscured by dust.

#BAFact: NASA’s budget is less than 1% of federal spending. Much less.

#BAFact: The Moon only reflects about 7% of the light that hits it. If it were icy, it would be 12 – 14 X brighter!

#BAFact: The fuzzy head of a comet can be *tens of thousands* of times the size of the solid nucleus.

#BAFact: Spiral galaxies come in many sizes. M33 is 1/10th the mass and ½ the diameter of the Milky Way.

#BAFact: The Universe started off very hot, but now has cooled to 2.725 +/- 0.0002 Kelvins. Brrrr.

#BAFact: As stars orbit in our galaxy we can see the nearer ones move. That's called proper motion.

#BAFact: Asteroids are usually pretty far apart, but they do sometimes collide. And when they do… kablam!

#BAFact: In 1843 the huge star Eta Car erupted, ejecting 2 gas bubbles with as much mass as the Sun. *Each*.

#BAFact: There’s evidence Venus may still be geologically active.

#BAFact: Brown dwarfs can be so faint that at the Sun’s distance they’d be dimmer than the Moon!

#BAFact: To scale, if the Earth/Sun distance were one inch, a light year would be exactly one mile.

#BAFact: If the Earth/Sun distance were scaled down to one cm, the Earth itself would be the size of a bacterium.

#BAFact: The summer solstice is the longest day of the year, but does NOT have the earliest sunrise/latest sunset!

#BAFact: The standard calendar year is the time it takes to go from equinox to equinox: one tropical year.

#BAFact: Earth isn’t the only planet to get hit by meteorites: they’ve been seen hitting the Moon!

#BAFact: The most common galaxies in the Universe are dwarfs, with just a few million stars each.

#BAFact: Venus undergoes phases much like the Moon does.

#BAFact: In 2008, astronomers caught the huge X-ray flash from an exploding star for the first time.

#BAFact: Think your weather’s bad? In some brown dwarf atmospheres it rains molten droplets of iron.

[UPDATE: This next fact was wrong—a new study had come out since the last time I had researched it—so I corrected it.]

#BAFact: Zodiacal light is sunlight reflecting dimly on wreckage from asteroid collisions.

#BAFact: Zodiacal light is sunlight reflecting dimly off dissolving comets near Jupiter’s orbit.

#BAFact: Think you’re a Taurus? Bull!

#BAFact: There’s an asteroid, called 2010TK7, that shares an orbit with Earth!

#BAFact: Today is the 104th anniversary of the Tunguska Event: an asteroid impact over Russia.


#BAFact: 2012 is a leap year. Today is the 183rd day: the last day of the first half of the year. Looking back, how did you do?

#BAFact: Water in a tub does *not* drain the opposite way in opposite hemispheres due to the Coriolis effect.

#BAFact: The most massive star known is >100 x the Sun’s mass. If it had any more it’d tear itself apart.

#BAFact: On July 4, 1054, the light from an exploding star reached Earth. It’s now the spectacular Crab Nebula.

#BAFact: Happy aphelion! The Earth has reached the farthest point in its orbit from the Sun: 152,092,424 km.

#BAFact: Huge amounts of dust around some stars is created when planetary collisions pulverize entire worlds.

#BAFact: Meteors don’t just happen on Earth: the Spirit rover saw one burning up over Mars!

#BAFact: Meteorites have been seen by the rovers sitting on the surface of Mars.

#BAFact: More than *2000* nuclear weapons have been detonated below, on, and above the Earth’s surface.

#BAFact: Face east just after sunset. That dark band across the horizon? The Earth's shadow on the sky.

#BAFact: The star HD10180, which is 130 light years away, may have 9 planets: a record!

#BAFact: In comics, Superman gets his power from our yellow Sun. The problem: the Sun’s not really yellow.

#BAFact: Don’t tell Vader: even the Death Star can’t really blow up a planet.

#BAFact: Blasting the Moon from Earth’s orbit would vaporize it. Sorry, Moonbase Alpha! #Space1999

#BAFact: There really could be Earth-like planets orbiting gas giants a la Prometheus.

#BAFact: In 1920, astronomers debated whether galaxies were small & close or big & far away. Answer? Far.

#BAFact: Asteroid impacts on Earth are random, so there’s no way to be “overdue” for one.

#BAFact: Exposed to the vacuum of space, you wouldn’t explode. You’d pass out and then die in other icky ways.

#BAFact: A dwarf companion to the Milky Way, the Large Magellanic Cloud, is cranking out newborn stars.

#BAFact: As Cassini orbits Saturn, it sometimes sees its moons eclipsing one another.

#BAFact: If you could stand on the surface of the Sun, you'd weigh 28 times what you do on the Earth.

#BAFact: Our air is transparent to visible light and radio waves, but absorbs most other kinds of light.

#BAFact: The diameter of the Sun is nearly twice the diameter of the Moon's orbit around the Earth.

#BAFact: Saturn is the flattest planet in the solar system: its polar diameter is only 90% of its equatorial diameter.

#BAFact: The Earth is nearly a perfect sphere: it’s 43 km “wider” than it is “tall”, a difference of 0.3%.

#BAFact: To the accuracy with which we can measure them, both Mercury and Venus are perfect spheres.

#BAFact: The Milky Way may have as many as 30,000 open clusters: groups of stars born together in one place.

#BAFact: Neptune has the fastest measured wind speeds in the solar system: 600 meters/second, or 1350 mph.

#BAFact: Spiral galaxies with patchy, puffy arms are flocculent, and they’re very pretty.

#BAFact: Astronomer fire powerful lasers into the sky to create artificial stars, aiding hi-res observations.

#BAFact: The Earth isn’t the only planet to see total solar eclipses. They happen on Saturn, too!


#BAFact: Gegenschein is a faint patch of light in very dark night skies seen directly opposite the Sun.

#BAFact: If Earth had rings, they’d look a lot different than Saturn’s. And they’d make astronomy really hard.

#BAFact: As on Earth, sand dunes on Mars move as the wind blows over them.

#BAFact: Using the physics of magnetism and plasma, scientists can make incredibly detailed models of sunspots.

#BAFact: If all goes well, Curiosity will be the fourth rover to successfully land on Mars… but 7 have been sent.

#BAFact: Humans fling robots to other planets, where other robots can take their picture as they land.

#BAFact: Mars has weather: In 2008, NASA’s Phoenix lander detected snow falling to the ground!

#BAFact: Mars used to have oceans on its surface, but they dried up long ago. No one knows why.

#BAFact: The Martian ice caps are so cold they have both frozen water and frozen carbon dioxide.

#BAFact: Meteors burn up about 100 km above the ground. But ISS astronauts look *down* to see them!

#BAFact: On average, the space station can expect a Perseid meteor impact once every 8000 years.

#BAFact: Ice just under the surface of Mars is revealed when small impacts make craters that dig it up.

#BAFact: Deep gouges on the Martian moon Phobos may be from rocks splashed up from impacts on Mars. [UPDATE: My friend Emily Lakdawalla notes ( a recent study shows this idea is probably not right. Interesting! So the grooves remain a mystery.]

#BAFact: As if it’s crying on a cosmic scale, a star sheds tears over its impending demise.

#BAFact: Red giant stars can blow off spherical winds of gas that surround them like giant haloes.

#BAFact: Saturn’s moons Rhea and Dione are so similar they can be hard to tell apart when they overlap.

#BAFact: What happens when you look for a galaxy near a really bright star? You get an NGC 404 error.

#BAFact: The Sun is more massive than 80% of the stars in the Universe. It *ain’t* average.

#BAFact: On Mercury, impacts ejected plumes of material that left “rays” which stretch across the planet.

#BAFact: Many human-made satellites are visible to your naked eye. And sometimes they flash you.

#BAFact: The red giant star Mira plows through space, its wind streaming behind it like a comet’s tail.

#BAFact: Jupiter is so big you could fit every other planet in the solar system inside it with room to spare.

#BAFact: Some people call Jupiter a failed star. But the *minimum* mass for a star is 80 times that of Jupiter!

#BAFact: A single exploding star - a supernova - can briefly outshine an entire galaxy of billions of stars.

#BAFact: Mars has a very thin atmosphere, but it can form clouds which can be seen from Earth.

#BAFact: Our Moon is the fifth largest moon in the solar system, and the 14th largest object overall.

#BAFact: The Sun is 400,000 times brighter than the full Moon in the sky.

#BAFact: The Sun is *12 trillion* times brighter than the faintest star you can see with your naked eye.

#BAFact: How much brighter is the Sun than the faintest object ever seen? About Avogadro’s number times brighter.

#BAFact: Because the Moon’s orbit is elliptical and tilted, we actually see a bit more than half its surface.

#BAFact: Gas clouds moving through space get squished as they slam into the thin material between stars.


#BAFact: Take all the Earth’s water and collect it. You’d have a drop 1400 km (860 miles) across.

#BAFact: At highway speeds, it would take 150 years to drive to the Sun.

#BAFact: Saturn’s moon Hyperion is one of the fluffiest objects in the solar system: it has half the density of ice.

#BAFact: The light that you see from the Andromeda galaxy left there when Australopithecus afarensis walked the Earth.

#BAFact: In our galaxy, stars are < 1 million km across and 40 *trillion* km apart. Collisions between them are incredibly rare.

#BAFact: To scale, the average size and separation of 2 stars in the galaxy are like 2 houseflies 400 km apart!

#BAFact: In globular clusters, stars are packed far more tightly than in our galaxy. Collisions do occur.

#BAFact: On a clear night, you can usually see 4 or 5 meteors per hour. Showers can produce hundreds per hour.

#BAFact: Mars has the tallest volcano in the solar system: Olympus Mons, over 20 km (12 miles) high!

#BAFact: Although it’s a common belief, Polaris is not the brightest star in the sky. By a long shot.

#BAFact: Jupiter's moon Ganymede and Saturn's moon Titan are both bigger than the planet Mercury.

#BAFact: Our solar system is about 6400 light years from the nearest spiral arm in our galaxy.

#BAFact: Spiral galaxy arms don’t wind up over time. That’s because they’re like stellar traffic jams.

#BAFact: You can see a total of about 6000 stars with the naked eye, but not all at once. The Earth is in the way of half of them.

#BAFact: The Earth's air traps heat. If we didn't have our atmosphere, the average temperature here would be below freezing.

#BAFact: Some asteroids have moons.

#BAFact: Some asteroids are binary! And when they hit a world, they make a double crater.

#BAFact: Zeta Oph is a runaway star, ramming the dust in space and creating a bow wave light years across.

#BAFact: Saturn has lumpy moons, and round moons. What’s the difference? Gravity.

#BAFact: An exploding star’s debris can expand so quickly telescopes can actually track its movement.

#BAFact: All our solar system planets orbit the Sun the same way. But some exoplanets go the wrong way.

#BAFact: As stars die, they blow off winds that form fantastic shapes that aren’t all that well understood.

#BAFact: It’s rare to catch a star dying in a globular cluster, but one’s green glow gave it away.

#BAFact: Asteroids come in all shapes and sizes. One, Kleopatra, is shaped like a dog bone!

#BAFact: Every big galaxy has a central supermassive black hole in its center, some billions of times the mass of the Sun.

#BAFact: Not all black holes are solo: *binary* black holes have been found in other galaxies.

#BAFact: The Earth is hit by about 100 tons of meteoric dust per day.

#BAFact: There may be millions of Tatooines – planets orbiting binary stars – in our galaxy alone.

#BAFact: Some spiral galaxies – like ours! - have rectangular cores of stars called bars.

#BAFact: The constellation of Libra used to represent the claws of Scorpius. The star names still reflect that.


#BAFact: Venus is the 3rd brightest natural object in the sky. You can see it in broad daylight!

#BAFact: The brightest events in the Universe are gamma-ray bursts, signaling the births of black holes.

#BAFact: Jupiter is 1300 times the volume of the Earth, but only 320 times as massive.

#BAFact: Those rays of light and shadow fanning out from the Sun at sunset? They‘re actually parallel!

#BAFact: Asteroid impacts can blast out huge streamers of rocks, creating long chains of secondary craters.

#BAFact: The Sun gets a wee bit hotter every day. In 3 billion years its heat will dry up Earth's oceans!

#BAFact: Galaxies sometimes collide, triggering massive, violent - and beautiful - bursts of star formation.

#BAFact: The person credited with first understanding why the sky is dark at night is …Edgar Allan Poe.

#BAFact: When massive stars are born, their UV light and fierce winds carve huge cavities in the surrounding gas.

#BAFact: You think tides on Earth are strong? Tides from galaxies can rip them apart!

#BAFact: Black holes have such intense gravity not because they’re massive, but because they’re small.

#BAFact: Based on current observations, 1/3 of all Sun-like stars may have habitable planets orbiting them.

#BAFact: Scientists classify solar flares into categories based on strength. The biggest? X-class flares.

#BAFact: There are about 30,000,000,000,000,000,000 molecules in a cubic centimeter of air at sea level. That’s 30 quintillion.

#BAFact: A cubic centimeter of air at sea level has a mass of about 1 milligram: one thirty-thousandth of an ounce.

#BAFact: The Moon has an atmosphere… kinda. It is 0.000000000000003 times as thick as the air on Earth's surface.

#BAFact: The nearest star to the Sun, Proxima Centauri, is a red dwarf, so dim and faint that it’s invisible to the naked eye.

#BAFact: Eons ago, Mars almost certainly had oceans on its surface, and they were far saltier than Earth’s.

#BAFact: Entire galaxies can be shaped and sculpted by the wind of their passage through intergalactic gas.

#BAFact: Matter falling into a black hole can create vast jets of material thousands of light years long.

#BAFact: Venus and Uranus spin backwards compared to the other planets in the solar system. No one knows why.

#BAFact: In its core, the Sun converts 5 million tons of matter into energy every second.

#BAFact: The amount of energy the Sun emits every second is the equivalent of 100 billion one-megaton nuclear weapons exploding.

#BAFact: The Earth intercepts only about one two-billionths of the total energy emitted by the Sun.

#BAFact: The actual solid part of a comet is tiny, usually less than a couple of kilometers across.

#BAFact: The nearest big cluster of galaxies is the Virgo cluster, about 50 million light years away.

#BAFact: We’ve seen Jupiter hit by an asteroid or comet at least *5 times* since 1994!

#BAFact: How big is the Sun? Roomy enough to fit 1.3 million Earths inside it.

#BAFact: Hurricanes spin because the Earth spins “faster” at the Equator than at the poles.

#BAFact: Earth's atmosphere traps heat. If we didn't have air, the average temperature on Earth would be below freezing.

#BAFact: At the center of our Milky Way galaxy is a black hole with 4 million times the Sun’s mass.


#BAFact: The Milky Way’s giant central black hole is about 24 million km (15 million miles) across: ~1/5 the size of Mercury’s orbit.

#BAFact: The black hole in the center of our Milky Way may seem huge, but it’s only .0004% the total mass of the galaxy.

#BAFact: In about 4 billion years (give or take), the Milky Way will collide with the Andromeda galaxy.

#BAFact: It would take more than 200,000 Moons to cover the entire sky.

#BAFact: Some spiral galaxies have tightly wound-up arms, and some fling them wide.

#BAFact: We’ve detected objects 96% of the way to the edge of the observable Universe.

#BAFact: The Sun is 4.56 billion years old, but has 6 billion left to go before it runs out of hydrogen fuel.

#BAFact: Coincidentally, the Sun is 400x bigger & 400x farther than the Moon, making them appear the same size.

#BAFact: Saturn's average density is less than water. Put it in a giant bathtub and it would float. But it would leave a ring. [old joke]

#BAFact: The Earth's atmosphere weighs 5 quintillion kg. That’s 5000 trillion tons!

#BAFact: The moon spins once for every time it orbits the earth. That's why we only see one side.

#BAFact: The Earth precesses (wobbles) as it spins, taking 26,000 years to make a single loop.

#BAFact: During a solar eclipse, the Moon blocks the Sun’s bright surface, allowing us to see its ethereal corona.

#BAFact: If you squished all the asteroids in the solar system together, you’d get a ball only 1/3 the Moon’s size.

#BAFact: Tides from the Moon are causing the Earth’s days to get longer.

#BAFact: Meteor showers happen when the Earth plows through debris shed by a comet.

#BAFact: Leonid meteors move rapidly across the sky because they orbit the Sun backwards. We hit them head-on.

#BAFact: Different elements vaporize off meteors at different times as they plunge through our atmosphere.

#BAFact: Your volume in cubic cm is roughly your mass in grams, because your density is about the same as water.

#BAFact: A typical storm cloud can have a mass of several billion kg – that’s millions of tons!

#BAFact: Clouds weigh millions of tons, but float due to being less dense than surrounding air, and from updrafts of warm air.

#BAFact: The atoms in a water molecule (H-O-H) form an angle of about 104.5 degrees.

#BAFact: We have direct evidence of liquid water on 2 worlds: Saturn's moon Enceladus & Earth.

#BAFact: Water is everywhere - it’s even been detected in a galaxy 11 billion light years away!

#BAFact: A cubic meter of liquid water has a mass of a metric ton. That’s 2200 pounds!

#BAFact: If you could squeeze the Earth down to about the size of a marble, it would be a black hole.

#BAFact: When the Sun becomes a red giant in 6 billion years, it'll eat Mercury & Venus. Earth’ll get scorched but may survive.

#BAFact: Despite all the legends and stories, the full Moon does not affect human behavior.

#BAFact: The volume of the Milky Way, our galaxy, is roughly 8 trillion cubic light years.

#BAFact: The hottest planet in the solar system? Venus, not Mercury! Thick atmosphere + greenhouse effect = 460C (900F).


#BAFact: Is today your birthday? You’re not a Sagittarius, you’re an Ophiuchus!

#BAFact: Earth’s gravity on an orbiting astronaut is 90% as strong as on the ground. But they're in free fall, so it feels like none.

#BAFact: Today Jupiter is directly opposite the Sun in the sky & closest to the Earth all year. It rises at sunset and is up all night!

#BAFact: Every day, as the Sun ages, it's a teeny bit brighter. In 1.1 billion years, it will be 10% brighter than it is now.

#BAFact: There is not a single red dwarf star visible to the unaided eye. They’re too faint!

Dec. 6, 2012 had no #BAFact posted due to an error on my part. So here’s a bonus one:

#BAFact: Venus is sometimes called Earth’s twin – it’s very close to the same size (95%) and mass (82%) as Earth.

#BAFact: Sunspots only look dark compared to the bright solar surface. By themselves, they’d be intensely bright.

#BAFact: If you fell into a black hole, you’d pass the event horizon (the point of no return) at the speed of light.

#BAFact: The Sun also causes tides on Earth, and are about half the strength of the Moon's.

#BAFact: Galileo saw Neptune in 1612… 234 years before it was discovered!

#BAFact: One cc of neutron star material weighs about as much as all the cars in the US combined.

#BAFact: Converting a single gram of matter into energy would explode with the yield of 22,500 tons of TNT.

#BAFact: Not all planets orbit single stars: more than a half-dozen planets have been found orbiting binary stars!

#BAFact: 40 years ago today, the last human bootprint was left on the Moon. For now.

#BAFact: Comet tails don't blow backward so much as they do outward, away from the Sun.

#BAFact: Even small quakes send out ripples over the Earth’s surface that travel for thousands of km.

#BAFact: The closer an object orbits another object, the faster it goes.

#BAFact: At any given moment, there are billions of neutrinos passing through your body.

#BAFact: Nibiru/Planet X doesn’t exist, so it can’t destroy the Earth.

#BAFact: Planetary alignments can’t destroy the Earth. On May 5, 2000 we didn’t go kablooie.

#BAFact: Today is the winter solstice, the northern hemisphere’s shortest day and longest night of the year.

#BAFact: Our Milky Way is part of a small cluster called the local group. We're one of the biggest. Go us.

#BAFact: From Mars, when Jupiter is closest, with your naked eye you would just see the giant planet as a disk.

#BAFact: The amount of energy the Sun emits in one second is enough to run the entire world for almost a million years.

#BAFact: Ironically, black holes can power the brightest sources of light in the Universe.

#BAFact: If the Earth were a basketball, the Moon would be a tennis ball 7.4 meters (24 feet) away.

#BAFact: On this date in 2004, the Earth was hit by the biggest blast of cosmic radiation in recorded history.

#BAFact: Full Moons occur 29.5 days apart, so we sometimes get 13 full Moons a year. Like this year!

#BAFact: The Sun is blazingly bright, but we’re close to it. From 60 light years away, it would be invisible to the naked eye.

#BAFact: Almost every star you see with your naked eye is <1000 light years away…and the galaxy is 100,000 light years wide.

#BAFact: Light from the edge of the Sun’s face takes over 2 seconds longer to reach us than from the middle.


#BAFact: On Jan. 1, 1801, Giuseppe Piazzi discovered Ceres, the 1st asteroid. Now we have a spaceship headed there.

#BAFact: Happy perihelion! Today the Earth is closer to the Sun than it will be all year: 147,098,161 km.

#BAFact: To scale, Saturn's rings are flatter than a sheet of paper.

#BAFact: The largest things in the Universe, galaxy superclusters, began as the tiniest: quantum blips in the Big Bang.

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  



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