Written by Kelly Herbst, Astronomy Curator for the Virginia Living Museum. Updated every two weeks, more or less.

Wednesday, October 26, 2011

Something Wicked This Way Comes

Oh yes indeed.  Halloween is this coming Monday.  If you have little kids in your house, like I do, your days are filled with costume prep, costume changes, plans to meet friends and trick-or-treat the best neighborhoods (the ones where you can get the most candy!) and hiding the candy you're supposed to give out from your husband.

You might not think of Halloween as a particularly astronomical holiday...but hey, my tag line up at the top says "Connecting astronomy and space science to...well...just about everything."  So...let's look for some spacey Halloween fun.

The celebration of Halloween is often linked back to a Celtic festival held around this time of year called Samhain, which literally means "summer's end."  As the days begin to shorten and the nights lengthen thanks to the tilt of Earth as we orbit the Sun, the residents of the British Isles (and many other places around the world) would hold a final party as the harvest came to an end, and preparations for the coming long winter ended.  During the winter, travel would be difficult, if not impossible, and this last celebration before the months that many people would spend shut in the their homes against the poor weather was a special one.  So astronomy comes into play right from the beginning of this spooky holiday.

But surely there isn't anything spooky about space itself, right?  Well...think again.  Space is filled with creepy and crazy things...mostly hidden in nebulae, those enigmatic clouds of gas and dust found throughout our galaxy (and indeed, all others).  In reality, these clouds are either leftovers from the deaths of stars, or stellar nurseries, where new stars are being formed.  But sometimes, we can't help but see something else in them.  For example, can you see the cackling face in this nebula?

The Witch Head Nebula.  Courtesy NASA.

This is the Witch Head Nebula, and the resemblance is truly striking!  I certainly wouldn't want to see that laughing at me through my eyepiece...well, actually, that would be kind of cool!

Not afraid of wicked witches?  Try this one on for a scare.

The Ghost Nebula.  Courtesy NASA.

This one is called the Ghost Nebula, and those wispy tendrils truly do make it seem as if something is swooping down towards us.  An apparition worthy of a Hollywood movie...except this is the real thing, and located in the Pleiades star cluster, which will soon be gracing our winter evening skies.  Still not convinced space is spooky?  How about one more?

The DR 6 Star Forming Region.  Courtesy NASA.

Now that is one creepy face.  Bearing a striking resemblance to a human skull, this nebula has the unimaginative name of DR 6.  I think the Skull Nebula suits it far better, however.  It sometimes called the Galactic Ghoul...which is pretty darn creepy, if you ask me.

All right, you got me.  Space isn't really's our own active imaginations that see spectres and spooks in the skies.  But it certainly is fun, isn't it?  Speaking of fun, I hope you'll join us this Saturday October 29th at the Abbitt Planetarium for some fun in the planetarium as we run Fright Light, our Halloween Laser Spook-tacular.  Showtimes at 7pm, 8:30pm, and 10pm.  Come on down for some terrifyingly awesome music, wicked cool laser lights, and even some sweet treats. 

However you decide to celebrate, have a safe, fun, and spooky Halloween!
Until next time,
Carpe noctem,

Wednesday, October 12, 2011

Over the Moon

Actually, I'm kind of not.

We had an amazing night last Saturday, observing the Moon.  The NASA exhibit was awesome...I touched a piece of the Moon!  Our Moon is incredible!

And that got me thinking...what about all the other moons?  Does anybody realize how incredibly awesome they are?

We tend to focus on our own Moon.  Makes's big, bright, and plays an important role in the existence of life here on Earth.  But among the major planets there are 168 other moons...all equally fascinating worlds in their own right!  So let's explore some of the other moons out there...and kind of play a little compare and contrast with our Moon, if you will.

Earth has one moon.  That's it...just The Moon.  Most of the other planets have many more moons indeed...Jupiter takes the prize for the most (if you don't count ring particles!) at 64 known satellites.  Even Mars has 2 moons - double what we've got!  The only planets with fewer moons than Earth are Mercury and Venus - neither world has any moons at all. 

Size matters though...Mars' two moons are extraordinarily tiny.  Phobos (Fear) and Deimos (Panic), as the Martian moons are named, are most likely captured asteroids.  They are small potato-shaped bodies, barely findable in a telescope from here on Earth...and even then only when Mars makes a close approach to us.  Such jagged chunks of stuff can be found orbiting all of the gas giant planets as well...the majority of the solar system's moons are weird little lumpy leftovers from the formation of the planets.

Phobos (top) and Deimos (bottom).  Courtesy NASA.

On the other hand, our Moon is not the largest in the solar system, either.  That distinction goes to Ganymede, largest moon of Jupiter.  In fact, Ganymede is larger than the smallest major 3,280 miles across it beats Mercury's size by more than 200 miles.  This massive moon is truly a world in its own shows evidence of tectonic activity, its own magnetic field, and it might even have an atmosphere.  Talk about your colossal moon!

Ganymede from the Galileo spacecraft.  Courtesy NASA.

Speaking of atmosphere, our Moon hasn't got one.  If you plan on visiting the Moon, make sure you bring your own air.  The moon with the densest atmosphere?  Saturn's enigmatic Titan.  The moon, explored by the Huygens lander, has the distinction of being the only moon known with an atmosphere consisting of more than trace gases.  It is a dense soup of hydrocarbons, with numerous distinct layers...shrouding the moon and looking like a heavy layer of orange smog.  So impressive is this moon's atmosphere that it is believed to be, like Venus, a super-rotator - that is, the atmosphere actually rotates much faster than the moon itself does.  The Huygens probe showed us incredible details about Titan, but so much more remains to be learned.

Titan from the Cassini spacecraft.  Courtesy NASA.

The surface of Titan from the Huygens probe.  Courtesy NASA/ESA.

Keep in mind, we've limited ourselves at this point to explore the moons of the major planets.  There are more moons than that in the solar system!  Of the 5 confirmed dwarf planets, 3 have moons: Eris has Dysnomia, Haumea has Namaka and Hi'iaka, and Pluto has Charon, Hydra, Nix, and the newly discovered P4 (it's so new it doesn't have a name yet!).  Pluto is only 2/3rds the size of our Moon - and it has 4 moons of its own!  Incredible!

Pluto and its 4 moons from the Hubble Space Telescope.  Courtesy NASA.

Oh, so you think only planets, be they major or dwarf, can have moons?  Not so...the asteroid Ida has a moon, Dactyl, first discovered by the Galileo spacecraft as it passed by on its way to Jupiter.  The solar system is rich with moons!  Take some time to explore them...both by reading up on them and by checking them out through telescopes - the moons of Jupiter and Saturn can easily be seen in telescopes from Earth!

Ida and its tiny moon Dactyl from the Galileo spacecraft.  Courtesy NASA.

Have fun mooning around, and I'll see you next time!
Carpe noctem,