Things that go flash in the night

It's a bird, it's a plane, its...a speck of dust?  That's right, that beautiful shooting star you were just exclaiming about was actually a tiny speck of dust meeting its fiery end as it slammed into Earth's atmosphere at around 40 kilometers per second.  Anything flying through the atmosphere at speeds that high is heated to thousands of degrees by friction with the air, causing it to glow and, in the case of small things like our dust speck, burn up.  Every now and then you might get lucky enough (or unlucky enough, depending on the circumstances) to see something larger slam into Earth's atmosphere.  Rocks the size of baseballs and basketballs produce fireballs that may last for tens of seconds as they streak across the sky.  I've been lucky enough to see a handful of these in my lifetime and every one was absolutely spectacular.

There are a number of phenomena that "go flash in the night", with shooting stars, formally known as meteors, being among the more common.  The Earth actually gets hit by some 300 tons of space rock every day.  Most of that is in the form of dust and most of that hits over the oceans (due to them covering the majority of the Earth's surface).  The good news is, the larger the space rock the less frequently they tend to hit us.  It takes a rock several tens of meters across to do any significant damage, and those only hit us about once every few hundred years.  "Armageddon" rocks are once in 100 million year events.

Another common flash in the night has origins much closer to home, namely satellites.  Watch the night sky for even 10 minutes and you're likely to observe at least one satellite.  Satellites look like stars that are steadily moving across the sky.  You can tell satellites apart from airplanes because airplanes blink and satellites don't.  A few satellites are really spectacular.  A group of satellites called Iridium communication satellites were put into orbit in the 90's to provide satellite phone service.  The antennas of the satellites are particularly reflective, and when hit with sunlight just right, will become very bright (brighter than any star in the sky).  This is called an iridium flare and can be identified by the way the satellite starts off very dim, then becomes very bright for a few seconds before dimming again.  Another very spectacular satellite is the International Space Station (ISS).  Due to it's size, the ISS is incredibly bright - unlike an iridium flare, it will maintain its brightness the entire time it is visible.  You can find out when the ISS will be visible in your location by going to http://spotthestation.nasa.gov/sightings/index.cfm#.U9RBAfldXRM.

Movies often incorrectly portray comets as flying across the sky much like fireballs.  Comets are actually much more subtle - they slowly grow brighter over the course of weeks and they slowly fade away, all the while moving across the sky at a pace that can only be observed by watching the comet for many days.  So comets really can't be described as something that "goes flash in the night"; however, they are directly related to another "flashing" phenomenon - meteor showers.

A meteor shower results when comet leaves behind a trail of dusty debris that happens to lie in Earth's path as it orbits the Sun.  When the Earth flies through the debris, the result is lots of shooting stars over a period of one or more nights - a meteor shower.  There are several meteor showers that happen at the same time each year - The Perseids are a regular August meteor shower that peaks the night of August 12 and is often one of the best showers of the year.  Unfortunately, this year that coincides with the full moon, making the sky much brighter and the meteors harder to see.  The Orionids are a good October meteor shower and the Leonids are another of the best showers of the year and peak in November.  Both of these will have little-to-no moonlight interfering.  The best time to observe a meteor shower is between midnight and dawn, and the best approach is to find a dark location with a good view of the sky and to lay back and observe as much of the sky as you can - meteors will happen all across the sky.  No instruments needed!  Actually, telescopes will hinder your ability to observe shooting stars because they only allow you to see a tiny piece of the sky.

But remember, it doesn't have to be a meteor shower to observe shooting stars and other flashy phenomena!  Get outside and start looking up!

The Observatory is open!

Tonight is the first public night of the Gunnison Valley Observatory for the 2014 season!  From tonight through September 13, the Observatory will be open every Friday and Saturday evening from dusk until around 11pm.  Starting around 8:30, a 20-30 minute lecture will be given on an astronomy topic - tonight's lecture, given by Park Ranger Ali Barnes from the Black Canyon National Park, is on Saturn; tomorrow I will give a lecture on the basics of astronomy (constellations, planets, observing tips, etc.).  Lectures are followed by viewing through the 30" telescope in the dome as well as smaller telescopes outside.  The Observatory is a family friendly facility (though perhaps not a bedtime friendly facility!)  If you're planning to visit, dress warmly (long pants, sweater or warm coat) as it does get cold!  We also ask for a donation of $5 per adult and $3 per child.  Hope to see you at the observatory!

Here's what's up in the sky right now:  First and foremost, it's a full moon, which doesn't really help observing much, but is nice to look at, and certainly makes it easier to see where you're going at night.  Fortunately in another few days, the Moon will be rising much later in the night so will only be an issue for those who do their astronomy in the AM hours.  Despite the Moon, there's still much to be seen - most notably, we have three planets in the evening sky right now.  Farthest west is Jupiter, Mars is almost overhead, and Saturn is to the east.  Other great objects in the sky right now are several globular clusters (very cool in a telescope) such as M13, the Hercules globular cluster; some very nice nebulae, such as the Ring Nebula, Dumbbell Nebula, and Lagoon Nebula; and a few billion galaxies, several of which are nice telescope objects, like the Whirlpool Galaxy (though the full moon can make these hard to see).

Happy observing!

How to buy a telescope, part 1

[This is long, so I'll break it into two parts - part 1 will focus on the basic characteristics of telescopes in general, while part 2 will look at specific telescope designs and reasons why you might choose one over the other.]

So we enjoyed a few days of spring weather before winter returned with a vengeance, so now, short of pulling your skis back out of storage, there's not much to do but browse astronomy magazines pondering which telescope would look best next to your patio furniture.  If you are indeed browsing telescopes in an astronomy magazine you're already well ahead of someone exploring the telescope aisle at "Buy'n'large" (if you don't know what I'm talking about, watch the movie Wall-E).  The fact is, you should never, ever, buy a telescope from a department store.  In a large city, you might be able to find a store (typically a camera store) that carries and is knowledgeable about quality telescope equipment, but otherwise, the internet is your best bet.

Let's consider what you should look for in a telescope.  First, some telescope basics.  In astronomy, there are two primary reasons to use a telescope:

1. Collect more light:  A telescope is essentially a "light bucket".  Most astronomical objects are fainter than the eye can see, so a telescope is used to collect more light and thereby allow us to see them.  Just as when you want to collect more water, you need a bigger bucket, when you want to collect more light you need a bigger telescope.  Telescope size is defined as the diameter of the largest mirror or lens (called the "primary" mirror or lens) in the telescope.  In the same sense as animals that need to see in dark conditions (such as squid or owls) have giant eyes, telescopes with giant lenses or mirrors will allow you to see much fainter astronomical objects like nebulas and galaxies.  Trust me, these are the things you want to see.

Andromeda galaxy viewed through a smaller telescope (a), and a bigger telescope (b).  The view through the bigger telescope allows the faint spiral arms to be seen.

2. Resolve fine details:  When you look at those amazing photos taken by the Hubble Space Telescope, one of the most awe inspiring characteristics (aside from the colors, and we'll talk about that in a bit) is the fine detail in the images.  Being able to resolve fine detail allows you to pick out individual stars in a globular cluster, see small craters on the moon, and distinguish wisps of gas in a nebula.  Having a telescope with good resolution is the difference between the cell phone camera you have today, and the one you had 10 years ago.  The resolution of a telescope, like light-collecting power, depends on the size of the telescope, and again, bigger is better.

Andromeda galaxy viewed with increasing resolution (a - d).  The view through a larger telescope (d) allows finer detail to be resolved.

There are several misconceptions about telescopes, and these are often played up by department store telescopes in an attempt to attract the unwary customer.  The first and most abused is magnification.  Many people believe telescopes behave similarly to microscopes, in that they magnify images.  There are two key differences between a telescope and a microscope - objects observed in a microscope are well illuminated, while telescope targets are faint, and objects observed in a microscope are very, very small, while telescope targets generally are not.  As a matter of fact, most of the objects we would want to observe in a telescope appear relatively large in the night sky.  A classic example is the Andromeda galaxy which is as large as the full moon in the sky, but hard to see because it's so faint.  In contrast, the smallest objects in the night sky are stars, and they're not hard to see at all!  The problem with magnification is that bigger is not always better, in fact, too much magnification can actually make an image much worse especially if you are viewing with a very small telescope - blowing up a faint, fuzzy image does not make it better!  The other thing department store telescope ads fail to mention, is that you can change the magnification of a telescope by changing the eyepiece - an accessory that can be purchased after you've found the perfect telescope for you.

A little magnification is good, but too much magnification may make your image worse.

The second misconception is that when you look through a telescope you'll see colorful images just like the Hubble pictures.  In general this will not be the case.  Our eyes have two types of light detectors in them - cones, which detect color, and rods, which are sensitive to faint light.  When viewing faint things, like objects in a telescope, only the rods are activated, allowing us to see the objects, but not their colors.  This is also why you don't see colors in a dark room.  In order to see color in astronomical objects, they must either be bright (like Jupiter or the double star Albireo) or you must take a long picture of them.  Photographs pick up color because long exposures allow them to collect more light.  And remember, the Hubble pictures are photographs too - often with much processing to enhance colors.

At this point you should have the idea that you want to buy the biggest telescope you can afford.  This is mostly true, but you also want to make sure you get a good telescope and that you get the right telescope for you.  We'll focus on the second point in part two, but I will include a list of reputable telescope brands below (note that this is not an all-inclusive list and I apologize if I leave out your favorite brand).

Generally reliable telescope brands (in no particular order, but the top 3 cater more to first-time buyers):
Meade
Celestron
Orion
Losmandy
Levenhuk
Astro-physics
Takahashi

Eclipse pics

We had excellent views of the eclipse last night here in Gunnison!

The first three pics are taken through my 4" Newtonian telescope.  I actually used my real camera (Nikon D3000) instead of my cellphone, though I don't have any means to attach it to my telescope so I was still just pointing it through the viewfinder.

The next pics were taken with just the camera alone.  Mars is the bright star to the upper right of the Moon.

Lunar Eclipse Monday night

Don't forget about the lunar eclipse that's happening Monday night!  Gunnison might currently be pulling a good imitation of winter in western Oregon, but the forecast for Monday night/Tuesday morning is looking good.  Check out the April 15th Lunar Ecplise page for more details!

April skies: Mars and a visit from the ISS

It's April - spring is in the air, and we're guaranteed at least a few more snow storms before summer finally graces us with it's ephemeral presence.  The upshot of all this is that, although the nights are getting shorter, they're becoming far more tolerable for stargazing.

This evening I stepped outside around 9pm to enjoy some beautiful skies.  Orion is now in the western sky and will be leaving us in another month or so.  To the north of Orion, Taurus and the Pleiades round out the trio of fading winter constellations.  Look for the "V" of Taurus with a bright red star - Aldebaran, the eye of the Bull - on one end.  The Pleiades are often described as looking like a faint, slightly hazy, tiny big dipper.  High in the western sky, Jupiter still reigns as king of the skies, but Mars is currently a worthy competitor.

Look to the eastern skies and you'll find two bright red stars - one is Arcturus, part of the obscure constellation Bootes, and the other is the planet Mars.  Mars is the brighter of the two and further to the south.  In my astronomy classes I teach my students to recognize Arcturus by using the phrase "Arc to Arcturus", which means to find the handle of the big dipper and draw an imaginary arc that traces the handle down to Arcturus.  Currently, if you continue the arc past Arcturus, you'll wind up in the vicinity of Mars.  The bright blue-white star below Mars is Spica.

Mars usually isn't all that spectacular, but currently Mars is unusually close to Earth, in a position called "opposition", where Earth and Mars are on the same side of the Sun.  Today marked the closest approach of Mars to Earth in two years.  The next opposition will occur in May of 2016.  Looking at Mars through my 4" telescope, I observed a small red disk.  The fact is, Mars is small - about half the size of Earth, so you need a larger telescope than I have in my back yard to see anything terribly interesting, like polar ice caps (or canals).  I would suggest checking Mars out with the Gunnison Valley Observatory's 30" telescope when they open in June - of course Mars won't be quite as close then, but it may still be worth looking at.

Relative positions of Earth and Mars around the Sun with positions and dates of opposition given.  Diameters are given in arcseconds - one arcsecond is 1/3600th of a degree.  One degree is the apparent width of your thumb at arms length, so Mars' current angular size of 13.9 arcseconds is still very, very small.

While I was outside, I had the pleasure and good timing to catch a sighting of the International Space Station as it passed overhead.  Observe the stars for any length of time and you're likely to see some satellites - they look like moving stars - they move about the speed of a high flying airplane, but they don't blink.  The ISS is quite the sight to see because it is exceptionally bright - brighter than most stars in the sky.  You don't have to rely on luck to see the ISS - just go to http://spotthestation.nasa.gov/ and look up upcoming sightings in your location.  If you're in Gunnison, the space station will be visible tomorrow, April 9th at 8:13 and 9:50 PM, as well as Thursday at 9:01 PM.  Look to the north for all of these sightings.  There are also additional opportunities to spot the ISS almost every evening for the next two weeks.

Pluto, Sedna, and hints of Planet X

Recently scientists announced  the possibility of a planet larger than Earth in the farthest reaches of the solar system (Trujillo & Sheppard, 2014, Nature, 507).  That's really cool, but before we address this fascinating possibility we must first address a far more pressing and vaguely related question: what happened to Pluto?!

The reclassification of Pluto from full-fledged planet to dwarf planet is often taken as something akin to discrimination against small solar system objects and a personal insult to Pluto-fans everywhere.  Rumor has it, Neil deGrasse Tyson was attacked by a mob of angry 4th graders after the announcement came out.  I'm all about standing up for the little guy, but I've also noticed no one every protests in favor of Eris, Sedna, Makemake, or Quaoar being upgraded to full planet status.

Wait...Quaoar?

Let's look at a little history of Pluto and friends:
Back in the early 1900's it was rumored that there might be a 9th planet beyond Neptune.  Astronomers thought Neptune's orbit was being perturbed by some more distant body - they were wrong, but it inspired them to start looking for the 9th planet - finding a planet was a sure-fire way to become a famous astronomer (or just plain famous).  One person in particular who was keen on finding the 9th planet was American astronomer Percival Lowell (founder of the Lowell observatory in Arizona and inventor of Martians - really).  Lowell devoted the latter part of his life to discovering the elusive planet, but died without achieving success.  Lowell's successor was former farm-hand turned astronomer, Clyde Tombaugh.  Tombaugh switched from farming to observatory maintenance man at an early age, and although uneducated, became a skilled astronomical observer.  After Lowell's passing, Tombaugh continued Lowell's search, and by a stroke of luck discovered Pluto in 1930.

Discovery images of Pluto - Pluto is the tiny star indicated by the arrow that moves from one night to the next.  The difficulty of discovering outer solar system objects is they appear as nothing more than tiny stars (not visible to the naked eye) that move relative to the background stars.

Much of Pluto's popularity comes from being the only "planet" to have been discovered by an American - Uranus and Neptune were discovered by a German-born Englishman, and a Frenchman respectively, while the rest were figured out by cavemen.  At the time, it seemed only natural to consider Pluto a planet because all relatively large objects orbiting the Sun were considered planets.  We also had no sense of Pluto's size.  Interestingly, when the largest asteroid Ceres was discovered back the 1800's, it too was considered a planet for several months until astronomers realized just how small it was.

Pluto was an official planet from the time of its discovery until 2006 when the International Astronomical Union (IAU) changed its designation, although astronomers were questioning its status as early as the 1970's.  To understand why the change was made, let's consider the demographics of the solar system.

Most of the solar system can be divided into about six categories: starting in the inner solar system we have the four rocky planets, just beyond these the asteroid belt, followed by the four gas giant planets in the outer solar system, beyond which is the Kuiper belt, the scattered disk, and the Oort cloud.  The inner rocky planets are relatively small and similar in composition to Earth, while the outer planets are much larger and primarily composed of hydrogen and helium.  The asteroid belt and Kuiper belt are bands of small rocks and chunks of ice, respectively that are the "leftovers" from the formation of the solar system.  The scattered disk is a widely scattered collection of objects that were ejected from Kuiper belt by collisions or close encounters, while the Oort cloud is a hypothetical collection of countless comets encircling the solar system 10,000 times farther from the Sun than Earth.

With the exception of the Oort cloud (which is spherical), and to a certain degree the Kuiper belt and scattered disk (where slightly tilted orbits are common), the solar system is quite flat with all planets and most asteroids and comets orbiting the Sun in a single plane.  The eight planets also have very circular orbits.  Pluto orbits the Sun within the Kuiper belt, and is neither rocky nor gaseous like the eight planets, but is instead primarily composed of ice like its neighbors.  Pluto also has a highly elongated and slightly tilted orbit.

With the exception of Pluto, the solar system beyond Neptune was virtually unknown prior to the late 1970's - astronomers had known that comets came from beyond Neptune as far back as the 1700's, but no object other than Pluto had ever been seen.  Discoveries of small icy objects beyond Neptune starting in the 70's confirmed the existence of the Kuiper belt.  Then, in 1992, the discovery of Eris changed everything.  Eris is a Pluto-sized object in the scattered disk and was almost considered the 10th planet.  But then within a period of less than 20 years, many more Pluto-like objects were discovered in the Kuiper belt and scattered disk, including Sedna, Makemake, and Quaoar (pronounced kwa-wahr).  Now there was a problem - based on the discoveries already made and studies of the Kuiper belt, astronomers predicted that there could be hundreds of these Pluto-sized objects beyond Neptune.  100 new planets?  "My Very Educated Mother Just Served Us Nine Pizzas" was going to turn into the longest mnemonic ever.

The real problem was not the number of objects, but that, while they shared many characteristics in common with each other, such as size, composition and orbits, they were very different from the eight rocky and gaseous planets.  Never before did we have to consider how we defined what a planet was.  It is the task of the IAU to name and define astronomical objects and they now had the undesirable task of having to come up with the definition of a planet.  (Undesirable because it was such a heated topic.)  Being a scientific organization, the definition needed a scientific basis and must be applied universally - no "grandfathering in" or arbitrary weeding out.  After much deliberation, the final definition they settled on was as follows:

A Planet must:

1. Orbit the Sun
2. Have a large enough mass to obtain hydrostatic equilibrium (be spherical)
3. Have cleared the neighborhood around its orbit

Number 1 is obvious, while number 2 rules out objects that are not round (like most asteroids) - generally any object larger than 1000 km in diameter will be spherical due to gravitational forces.  Pluto (as well as many other solar system objects, like the asteroid Ceres) meets these first two criteria.  The last rule requires that a planet be large enough to gravitationally dominate its orbit - any other objects sharing the orbit will either eventually fall into the planet or be kicked out of the orbit by gravitational encounters.  This rule eliminates all but the eight planets we know and love today.  Pluto, Eris, Ceres and the rest all share their orbits with millions of other objects and are by no means the dominant bodies in their orbits.  Any object that satisfies the first two requirements while not meeting the third is now classified as a dwarf planet.

Eight of the largest dwarf planets (a trans-Neptunian object is anything beyond Neptune), several of which have their own moons.  Sizes are shown to scale with part of Earth shown for comparison.

So what about Planet X?  First, the term "planet x" is the colloquial term used for any newly discovered, but unconfirmed or unnamed planet - as you might have guessed, it's not a term that's actually used very often, except perhaps by overeager journalists.  Astronomers are known for coming up with their own unofficial names too - for a period of a time, there was a dwarf planet known as "Easter bunny".  In this situation several dwarf planets and smaller objects, including the large dwarf planet Sedna, have been found to have very unusual orbits.  These planets orbit extremely far from the Sun in a no-man's land between the scattered disk and the Oort cloud.  They also have extremely elliptical orbits - Sedna ranges from 76 AU (an AU is an astronomical unit, or the distance between the Earth and the Sun) from the Sun at closest to more than 400 AU at its most distant.  Aside from their unusual locations and orbits, what is particularly surprising is that all of these objects orbit in basically the same plane - because scattered disk objects were flung into their current locations by random interactions with other objects, they tend to have fairly randomly oriented orbits.  One hypothesis as to both how these Sedna-like objects got to their current locations why their orbits are so similar is that they are being affected by gravitational tugs from a planet larger than Earth 250 AU from the Sun.  Naturally, it is now being referred to as Planet X.  I want to emphasize that such a planet has not been observed - in fact it may not even be possible to observe such a planet due to the extreme distance (Pluto, by comparison is a mere 40 AU from the Sun on average) - this is simply one possible explanation for the observed behavior of these objects.  Some astronomers say there may even be dozens of planet-sized objects in the Oort cloud

So at present there are still just 8 planets and a dozen or so dwarf planets.  But I still think the possibility of more planets in our solar system is totally cool.