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

Wednesday, February 27, 2013

What's Up?

Well, hello.

It's been an eventful time in the astronomy business, thanks to a chunk of rock that decided to scare the living daylights out of a whole lot of people living in Siberia.  Amazingly, they seem to like air-bursting asteroids...once again, just like in 1908, a chunk of space rock exploded rather than impacting.  Since this one did so over a city, many people were injured when they rushed to look out their windows to see what the bright flash of light was.  Once the shock wave hit, the windows shattered, glass went flying, and many people were hurt.  But fortunately, I do not believe there were any deaths associated with the event.  But my goodness, it must have been quite scary to experience that first hand.  We talked about the 1908 event in our previous chat...when I wrote that I had no idea it would be happening again so soon!

The fireball over Siberia on February 15, 2013.

Anyway, let's turn ourselves to a calmer exploration of the sky.  It's been a while since I wrote a nice, simple post about things appearing in the skies above, so I think it's time to do that again.

The early evening skies are currently dominated by the largest planet in the solar system - Jupiter.  Shining brighter than all the visible stars, Jupiter is easily seen high in the southwest after sunset.  It's currently located in the constellation Taurus the Bull, right behind the bull's V-shaped face.  Taurus, of course, is facing off with Orion the Hunter, brightest constellation of our sky and easily visible high in the south.  So just by looking southward after sunset you should be able to quickly find the seven bright stars of Orion.  Use the belt of Orion (three stars in an almost perfect straight line) to find Taurus by following the line it makes away from Orion towards the right.  The belt will point you to the brightest star of Taurus, reddish Aldebaran.  This is the upper left point of the V of Taurus' face.  Right next to the V will be Jupiter, almost shocking in its brightness.

Following Orion's Belt to Aldebaran, the red right eye of Taurus the Bull.  In February of 2013, Jupiter is located between the V of Taurus' face and the Pleiades.

Jupiter is an incredible world.  Ten times bigger than our own planet Earth, Jupiter is a gas giant and the largest of the solar system's planets.  Even so, it is still much too small to be a star...Jupiter would have to be 10 times again as big as it is to become a star like the Sun.  The gravity of mighty Jupiter holds over 60 moons in orbit around the massive world, and even supports a tiny, thin ring system, completely invisible from Earth.  Only visiting spacecraft have the opportunity to see the rings of Jupiter, and they have fortunately sent lovely pictures back to us here on Earth.  Known from ancient times, Jupiter has long fascinated us, and it has been the target of numerous missions including the Voyager space probes and the Galileo spacecraft.  Another mission, Juno, is on its way, with a planned arrival in July of 2016.

The giant planet Jupiter.

The only other planet currently visible to us is Saturn, which graces the early morning sky before the dawn.  You'll see Saturn as a golden-yellow star-like object shining in the south before the Sun rises.  A pair of binoculars is all that is needed to reveal the lovely Saturnian rings, but you will need to hold them very steady.  A tripod will serve you well.  And be prepared to get up quite early - 5AM is the best time to see Saturn these days.  If you'd rather see it at a more convenient time...wait a few months.  Later in the year, Saturn will become an early evening object rather than an early morning one.

Saturn and its amazing ring system.

So everyone take a deep breath, relax, and enjoy the sky.  I promise, despite the events of recent days, the world is not coming to an end.  Hopefully the sky will give us a few days to catch our breath before the next potential big event - Comet PANSTARRS.  If the comet becomes something worth venturing outside to see, I'll put out a Cosmic Strings Alert to let you know.

Barring that, I'll see you in two weeks!
Carpe noctem!

Wednesday, February 13, 2013


I hope you found those to be nice, friendly letters.

At any rate, truly, there is no need to panic.  Friday will come and go, and we will NOT be destroyed by a giant rock from space.  Truly, we won't.

You've probably heard about asteroid 2012 DA 14 (yes, that's really the only name it has!), which will be making an extraordinary pass by Earth this Friday.  In fact, here's the official details:

Asteroid: 2012 DA 14
Date: Friday, February 15, 2013
Time: 2:24PM EST
Distance at closest approach: 17,200 mi from Earth
Size of asteroid: 164 ft. wide
Composition: Stone
Chance of impact: ZERO

Did you read that last bit?  There is a ZERO chance that 2012 DA 14 will hit the Earth this Friday.  Zero. Zilch.  Nada.  None.  No chance at all.  Not even if it happens to hit a satellite (which is terrifically unlikely) - it cannot possibly "bounce" off a satellite and hit the Earth.  It simply will not happen.

So, what will happen?

This asteroid will zip past our planet a bit inside the orbit of the geosynchronous satellites.  Those satellites handle things like weather and communications, among others.  The rock will go outside the GPS satellites, however.  So while it will be close to won't be that close to us. 

Some folks are hoping to be able to see this rock as it zips past.  That will be extremely difficult, for several reasons.  First of all, it will be moving a good clip...17,400 mph, in fact.  That means it will move across the sky about 1 degree per minute - tough to track, that's for sure.  And you'll need to track it, because it won't be visible to the unaided eye.  Even coming so close, the rock is so small, you'll need at least a pair of binoculars to see it at all.  And one other small'll need to be in the middle of the Indian Ocean.  Sumatra will get a nice view.  So...not much of an event here in the U.S.

But now, let's tackle the juicier question...what if the scientists are wrong? (They're not.)  What if it does hit us after all?  (It won't.)

Okay, let's consider it.  What would happen if 2012 DA 14 hit the Earth?  Lucky for us, we've got some good models for that...because they've already happened.  (insert gasp of surprise here)

2012 DA 14 is about the same size as the asteroid that impacted the U.S. some 50,000 years ago just outside of what is today Winslow Arizona.  That meteor struck the ground and blasted a hole in the Earth 4,000 feet in diameter, and 570 feet deep.  You can visit the crater today - it's called Barringer Meteor Crater.  

Barringer Meteor Crater in Arizona

Now, the meteor that created Barringer Meteor Crater was made largely of iron.  2012 DA 14 is a stony object.  So it would not impact with nearly the same amount of force.  In fact, it probably would not impact at all...the stress of enter Earth's atmosphere at a high rate of speed would likely shatter the rock before it ever made it to the ground.  We've got a model for that too.  On June 30, 1908, a meteor about the size of 2012 DA 14 exploded over the Podkamennaya Tunguska River in Siberia.  The blast leveled 830 square miles of forest, and likely measured 5.0 on the Richter scale.  The energy of the blast was about 1,000 times as much as that from the atomic bomb dropped on Hiroshima by the United States.  If a blast like this occurred over a major population center, the results would most certainly be unpleasant.  But not Earth destroying, by any means.

Trees leveled by the Tunguska explosion in 1908.
So...long story short....Friday will be a great day for scientists who study asteroids...and maybe even for a few amateurs who can get photographs of our celestial visitor...but for most of us, it will simply be another day on planet Earth.

Until the next close shave...
Carpe noctem!