Monday, 24 April 2017

T is for Telescope

The Universe is full of light. Therefore, if we want to know more about the Universe, we need to sample some of that light for analysis. One of the best ways to capture that light is in a lightbucket called a telescope.

For thousands of years astronomers only had one method of capturing light--MK-1 Eyeball, aka the naked eye. Look up in the sky, what do you see?

Lots of stars, most of the major planets and a few other fuzzy objects were easily observable with the naked eye. It had its limitations, as it only detected wavelength between 390 to 700 nm. Also, it was limited in its resolution and the number of photons it could capture.

For a few thousand years humans knew that carving glass into certain shapes could bend light, focusing it, bringing more photons to the human eyeball. Then really recently, in the early 1600's, a few bright sparks put a couple of lenses in a tube, looked through and yelped, "Wow! I can see far! Tele-scope!" The first refracting telescope was born. Thomas Harriot thought it would be nifty to look at the sky through this thing. He was right. To him, the Moon looked awesome. He could see such detail!

Galileo and his refractor.
About the same time, Galileo built his own and looked upwards. To his amazement, he found four moons orbiting Jupiter. These details were not visible previously. The ability of the telescope to capture more photos and resolve very distant objects was totally amazing.

Newton's reflecting telescope.
Humans are lots of fun because they'll take an idea and run with it, seeing if they can improve on the original design. Another bright spark (some guy named Newton) wondered if a parabolic mirror could serve just as well for focusing the light. Sure enough, it worked wonders.

So lots of gentleman scientists played with this new tele-scope technology, improving it in size and quality, and peered into the heavens with it. At first, it was mostly planets they stared at, and various nebulae, as the stars were too far away to resolve to anything but points of light.

That didn't stop them from having fun with the light they captured. Prisms were notorious for breaking plain light up into pretty rainbows called spectra (singular: spectrum). When that happened, they then discovered things like absorption lines, infrared,  and ultraviolet.

You can go really big with radio telescopes,
like they did in Arecibo.
The infrared and ultraviolet discoveries really sparked some imagination. Could there really be "invisible" light beyond the visible spectrum? If so, could we capture it?


With lower frequencies such as radio waves, they discovered they could be captured with antennas. Later, radio dishes (very similar in shape to the parabolic mirrors used to capture light) helped focus radio waves onto the receiving antenna, instead of just trying to pick up any old radio wave that happened to bounce by, like the aerials on our rooftops.

X-ray telescopes, same thing. A large parabolic mirror focuses X-ray wavelengths onto an X-ray detector. Problem with X-ray telescopes is that they're rather useless on Earth, as our atmosphere blocks out most stellar X-rays. So if we wanna gather X-rays, we've got to put our light buckets into orbit.
X-ray telescopes, like the Athena X-ray Observatory, can have lots of fun capturing the emissions of X-ray sources from orbit.

By the end of the 20th Century, humankind had come up with all kinds of telescopes to observe different kinds of electromagnetism. We're very good at capturing photons of all wavelengths, studying them, and thus, through sheer observation alone, we know about our Universe.

Do you have a telescope? If not, have you had a chance to look through one? If you haven't, see if you can find a local star party. Many planetariums and astronomical clubs hold them regularly. I recommend waiting a few months for Saturn to rise, for that is one spectacular planet to look at through a telescope.

Her Grace observes through a Celestron Nexstar 130SLT 5" reflector.

Saturday, 22 April 2017

S is for Star

S is for Star, and really, you cannot talk about astronomy without mentioning stars. Impossible.

Anyone who's ever expressed the slightest interest in astronomy does so because of stars.  You look up in the sky, see the stars, and go, "Cool!" Stars are what get us interested in space.

Here's an earworm to annoy you for the rest of the day, "Twinkle Twinkle Little Star" (the astronomically correct version):

Stars are the most obvious part of the universe because they shine so brightly along all the electromagnetic spectrum. I consider them a key component of the cosmos. They are the movers and the shakers. They are responsible for all the "metals" (ie elements heavier than H and He) out there. E V E R Y T H I N G out there that's not Hydrogen/Helium, is because of stars.

As you know, hydrogen makes up a good three-quarters of the universe. When that hydrogen (usually in a nebula) gets enough gravity to collapse together, fusion starts and you get a star.

Vital Stats of Stars


Stars range in weight (measured in solar masses or M) from about approximately 0.2 M  to humongous beasts pushing 150 M. Now, that might not seem like a very big range, seeing that one solar mass (M) equals the weight of our Sun at 1.98855 × 1030 kg. But if you look at the radii of these stars, the smallest is about 20% wider than Jupiter, but the biggest is a whopping 1500 times as wide as our Sun. Frickin' huge.

Here's a size comparison:

Also, the bigger a star, the faster it burns through its hydrogen. Really, really big hypergiants have been known to live for the brief moments of a few million years. Living fast, dying young, they leave a really impressive supernova/hypernova before letting its corpse collapse into a neutron star or even a black hole.

Smaller stars last a lot longer. Our own Sun will live about 10 billion years, whereas some red dwarfs could possibly live for trillions of years.

OGLE-TR-122b is the smallest main sequence star we've discovered so far that's still fusing hydrogen. If it got any smaller, it wouldn't have enough gravity to ignite fusion. Unless you're fusing, you ain't a star.


Stars range in colour, which also correlates with temperature.

Stars are classified according to colour(temperature), with blue stars being the hottest and red stars being the coolest.

The spectra of star types. See how the spectra peak in certain colour ranges? That's why stars appear coloured.

Blue O-type stars tend to be 30-40,000 Kelvin.
Blue-white B-types are 20,000 K,
White A and F stars are about 8-10,000 K
G-type stars, like our yellow Sun, are about 6000 K
Red K and M-type stars can be as cool as 3000 K  (For reference, you are around 310 K).

Look up in the night sky and see if you can tell what colour a star is? While most of them appear "white", compare nearby stars to see if you can detect a faint bluish cast or reddish cast.  Betelgeuse in Orion is distinctively red, as is Antares in Scorpio. Rigel in Orion is rather blue.

Why aren't there any green stars?

Actually, there are. Any "white" star is actually radiating in the green part of the visible (optical) spectrum. Green happens to be right in the middle of the spectrum, so when a star is emitting green, it also emits red and blue. Combine all these together (additive colours), and they look white. Our Sun, a G2-type star is generally classified as Yellow-White. But if white is really green, that makes our Sun a yellow-green star. (Consider how much green light gets reflected by plants on Earth. That light's gotta come from somewhere.)

Birth and Death of a Star

So, a star is born from the gas of a nebula. After it gets over its initial teething phase, it settles into the Main Sequence, happily fusing its hydrogen into helium. It'll spend about 90% of its life like this.

Once it runs out of hydrogen, they move off the main sequence, do a few interesting things (like helium flashes, variable pulsing, puffing up like balloons), then die.

When it comes to the death of stars, the manner of its demise depends on its mass.  For smaller mass stars, like our Sun, it'll inflate into a red giant, then with a gentle poof, shed its outer layers, leaving the cooling cinder of a white dwarf.

But if it's a massive star, especially of the live-fast-die-young category, it starts fusing everything into onion layers of elements until it reaches iron. Once that happens, fusion stop, the pressure keeping the star puffy ceases, the star collapses in on itself, rebounds, and dies most violently B A N G!! in a  spectacular supernova.

Don't let the gentle spread of this light echo fool you. This time-lapse covers a period of four years. The light echo is about six light years across. We're talking some serious velocities here.

The energy released in this explosion is enough to start a new wave of nuclear reactions that fuses iron into the higher elements like gold and uranium and blowing them out into the universe.

Whatever is left over gets fused into neutrons and collapses down into either a neutron star or a black hole in the middle of a brand new nebula.

Meanwhile, the shockwave of a supernova can extend for several parsecs, rolling through any neighbourhood nebular clouds of hydrogen, possibly triggering some of it to collapse into new stars.

And thus, the cycle begins again.

Some people just like looking up in the skies. And that's okay. Do you have any favourite stars?  What make them your favourites?  I'm fond of Betelgeuse and Canopus.

No hardcore stuff today, unless you want to investigate more about V838 Mon which occurred in 2002.

Her Grace is sometimes content just to stare up at the stars with MK-1 eyeballs.

Friday, 21 April 2017

R is for Radio Waves

Since everything in the Universe is so terribly far away, the only way we can science it is through observation. Fortunately, we have the Electromagnetic Spectrum, which can tell us all sorts of things.

At the high end we have the powerful, ionising wavelengths of X-rays and gamma rays, and at the low end we have the more zen-like non-ionising wavelengths such as microwaves and radio waves. All these different wavelengths interact with baryonic matter in different ways. This difference gives us an advantage in astronomy. For example, Earth's atmosphere will block gamma rays but will allow radio waves through.

This makes radio waves both ideal and infernal for ground-based astronomy.

If you tune your car radio in between the official broadcasting stations and listen to the static, some of static comes from the universe. (Radio static is how they discovered the Cosmic Microwave Background, or the radio wave echo of the Big Bang.) Sounds like this:

The atmosphere isn't uniformly transparent to radio waves, because our atmosphere is a rather complex thing. Some frequencies will shoot straight through, others will bounce around. This bouncing around can cause interference, which you can detect on your car radio as static.

The closer you are to population centres, the stronger the radio will be, because we have radio broadcasters and mobile phone cell towers and all sorts of radio-bright sources.  Also, humidity in the atmosphere can block out radio waves.

So, what's an astronomer to do? The best earth-based radio astronomy sites are those away from civilisation, out where it's dry (low humidity) and "radio-quiet".  Western Australia has a Radio Quiet Zone  in the Murchison (our gratitude to the Wajarri Yamatji people, the traditional owners of this land) for the Square Kilometer Array, a large radio telescope.

Don't think that radio astronomy is out of reach for the amateur astronomers and citizen scientists. There are plenty of amateur radio astronomy clubs and organisations throughout the world.

But if you don't want to go hardcore and build your own radio telescope, you can still experience radio astronomy. If you tune your radio to the frequency of 1420 MHz (that's 1420 AM), you could listen to the hydrogen of the Universe speak to you. Sounds like this.

Spectral lines from other radio-sensitive stuff are detectable in radio astronomy:

  • 1400 - 1427 MHz: 21cm hydrogen line
  • 22.01 - 22.5 GHz: Water
  • 23.6 - 24.0 GHz: Ammonia
  • 36.43 - 36.5 GHz: Hydrogen cyanide and Hydroxil
  • 72.77 - 72.91 GHz: Formaldehyde

More about how radio astronomy works.

Here's some pictures of stuff in radio frequencies.

Galaxy M51 (Whirlpool Galaxy) in radio and optical:

The planet Jupiter is also radio-bright:

Galaxy M87 showing off a radio-bright jet from its supermassive black hole:

The Sun in optical, radio and X-ray:

Galaxy M31 (Andromeda Galaxy) in radio and visible. Radio has a way of shining through the dust that would normally block visible light. This is one of the advantages of radio astronomy.

What the Milky Way looks like at 408 MHz:

Radio astronomy, indeed astronomy in all the wavelengths provides astronomers with a different point of view.

Her Grace once observed the universe through a mate's homemade radio telescope. It looked an awful lot like a silver umbrella attached to a laptop, because it was.

Thursday, 20 April 2017

Q is for Quasar

In the middle of the 20th Century, astronomers were astounded to find a very bright radio source--stunningly bright. In fact, they were brighter than anything else previously known  (or since, really).  They called them Quasi-stellar Objects (QSOs).

But what were they? Astronomers captured their spectra and had a look. The spectra looked really odd, until they figured out that they were extremely redshifted. Redshift is a nifty astronomy tool. Here's how it works:

Original spectrum    vs   a redshifted spectrum
See the absorption lines in the rainbow spectrum on the left? This is a normal spectrum where some of the light has been absorbed by an element (say, hydrogen and its Balmer Lines).  When the light that makes this spectrum comes from very far away, the expansion of the universe stretches it out and makes the frequency drop. The result is the spectrum on the right, where the absorption lines move in a red-ward direction. This is redshift. Think Doppler Effect.

The greater the redshift, the farther away an object is. The spectrum sampled from quasars were so redshifted it took us a while to figure out just how redshifted they were.

In other words, these really bright radio sources were really, really far away. That was doubly-amazing because of the Inverse Square Law--intensity reduces with distance.

"Dude!" we cried.  What could possibly create so much energy to be so bright from so far away?

Eventually, we figured out quasars were really, really active distant galaxies and that the extreme energy output came from the accretion disks of the  supermassive black holes in the middle of those galaxies. Those suckers can really put on a shine when actively consuming some poor star.

(Is our own Milky Way a quasar? Currently no, as our Sagittarius A* is a rather quiet supermassive black hole at the moment.) Quasars are believed to be an early universe phenomenon because we observe them as coming from waaay back in time. But that doesn't mean that Sgr A* couldn't become a quasar in the future, given enough to eat.

So we figured out that quasars are:
  • really old
  • really distant
  • really bright
Once we established that, we realised they could be used as a kind of anchor point in mapping of the skies. See, the farther away something is, the less likely it is to apparently move.

Want to know more about quasars?

Her Grace prefers to study objects that are a little bit closer than z=7.085.

Wednesday, 19 April 2017

Using Singing to Create a Positive Emotional Benefit

We haven't had a TASE (Talk About Something Else) Day in a while. We're overdue.

A friend is teaching a child how to master their emotions. Like all good researchers, she asked her peers for their experiences.  I suggested singing as a quick and immediate method the child could use to get themself out of an emotional rut like frustration or anger.

I've always known singing to be a positive mood-lifter, far more effective than just listening to music. I've taught classes in using singing for optimism, and often teach my regular music students how to use music for their emotional benefit. (A bit of a selfish purpose behind this one as well, for if a child learns to love creating music, they'll be more likely to practice.)

Not everyone is a musician, but I believe everyone is capable of singing. You might be a bad singer and woefully out of tune, but you can still sing, and you will still receive the benefits I list below. Never let anyone tell you you shouldn't sing. I refuse to oppress a singer just because they might not have learned to master their pipes yet.

Anyone who's sung out loud may have noticed the centering effect music has. Really, it works, so here I go hardcore with research to explain how this works.

Singing can alter your mood through:

  • Employing deep and focused breathing. To sing, one must first draw breath, then release it in a focused and controlled manner to make sound. This deep breathing can also slow heart rate and neural activity. It also provides re-focus, as the brain must concentrate on producing music. Also, the vibrations of music has an effect on the autonomic nervous system. (Clark & Tamplin 2016)  
  • Triggering endorphin release. While merely listening to music can make us feel better, the actual performance, whether playing an instrument or singing, has the greater benefit. It requires the singer to be active and not just passive, as a listener would be. This activity stimulates greater endorphin release. (Dunbar et al 2012)(Kreutz G et al 2004) 
  • Using a different part of the brain. This disengages the "stuck" brain and engages fresh thinking, which will be less likely to get stuck in a feedback loop. Singing also engages the same part of the brain that processes emotions. Take that over, and the negative emotions are easier to deal with and get over. (Chanda et al 2013) Also helps with stuttering and emotion-related speech issues, like an inability to explain oneself when upset.
  • Familiarity. As our common rituals and favourite things soothe us all, the familiarity of a favourite song can also bring us back to ourselves when we feel out of sorts. (Ibid)

So, how does one get this singing schtick to beat off the black dogs?

  • Before you find yourself in an emotional bucket o' crap, choose a positive song or ten to be part of your emotional first-aid kit. I've got several, but one that works really well for me is "Before the Parade Passes By" from the musical "Hello Dolly".  Get in the habit of singing your first-aid kit songs now and then so you can get used to how they feel in your chest.
  • When you find yourself down or frustrated or angry, pull out the song that "feels right" for the moment, and start singing, even if you don't feel like it. If you're not really in a place you can sing out loud and can't get to one, humming is also acceptable. But if you can do some proper out-loud singing, the deep breathing will do you much good.
  • Do not let whatever harshed your original mellow steal the focus from your song. You're here to beat the grief, not let it beat you.  (3/4 or 4/4 are good beats.)  Singing won't solve your original problem, but it will resettle your brain enough for you to have more spoons with which to cope.

Barbara Streisand singing "Before the Parade Passes By".

I am interested to hear results from anyone who's willing to experiment on this method and report back.


Clark IN & Tamplin J (2016) "How Music Can Influence the Body: Perspectives From Current Research" Voices, 16, 2

Dunbar RI, Kaskatis K, MacDonald I, Barra V (2012) "Performance of music elevates pain threshold and positive affect: implications for the evolutionary function of music", Evolutionary Psychology, 10, 4

Kreutz G, Bongard S, Rohrmann S, Hodapp V, Grebe D (2004) "Effects of choir singing or listening on secretory immunoglobulin A, cortisol, and emotional state" Journal of Behavioural Medicine, 27, 6

Chanda ML & Levitiin DJ (2013) "The neurochemistry of music (A meta study)" Trends in Cognitive Science, 17, 4

Her Grace is a Coloratura Mezzo-Soprano by training, though her voice has gone a little smokier with age.

P is for Planet (It's okay, you can call Pluto a planet if you want)

In ancient times, skywatchers noticed certain stars wandered about, and didn't stay fixed like the rest of them. The ancient Greeks called them  πλανῆται (planētai, "wanderers"), and the name stuck. Indeed, if you observe them for several days or weeks, you can notice them inching along relative to the stars in their apparent proximity.

Essentially, a planet orbits a star. All other descriptions are mere refinement.

In 2006 the International Astronomical Union (IAU) issued an updated definition of what a planet is. This came along because more planets had been discovered on beyond Pluto. Once they realised they'd have dozens, potentially hundreds of new planets, they thought they'd come up with some definitions to help sort or categorise the planets. This definition is based off the gravitational interaction of a planet with its environment:

"A planet is a celestial body that:
  1. is in orbit around the Sun, 
  2. has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and 
  3. has cleared the neighbourhood around its orbit."
Based on this, we've got four Terrestrial planets (Mercury, Venus, Earth, Mars) and four Gas Giants (Jupiter, Saturn, Uranus, Neptune).

"But what about Pluto?" you cry! "They demoted it! It's no longer a planet!"

Uh, yes but no. Pluto is still a planet. Go ahead and call it one if you want. It's new classification may be "dwarf planet", but that is still a planet.

Shot this pic of Venus a month ago
with my smartphone thru my telescope.
When I was a wee junior astronomer, I always thought Ceres got a bad rap. It was classified as a planet when discovered in 1801 (yep, it was discovered before Neptune).  Everyone thought this was nifty, until lots of gentleman scientists started discovering more and more rocks. "Surely these cannot all be planets," they mused. Once they figured out just how small and numerous these rocks were, they reclassified them as "asteroids" in the 1850's, and poor Ceres got demoted.  Yeah. These things happen when you start looking and finding stuff.

So, when the 2006 definition came along, Ceres got re-promoted and classified as a planet once more, albeit in the "dwarf planet" category. I didn't mind (Okay, I was ecstatic!). But many people who weren't around for the 1850 demotion of Ceres, didn't realise the historical precedence for this sort of card-shuffling of our Solar System.

Just like in the 1850's, the 2006's brought a new definition of a classification, because lots more of whatever it was they were classifying were found.  Kuiper Belt Objects (KBOs) were being discovered all the time, and some of them were large enough they could be classified as planets. Also, planets were being discovered around other stars. Everyone went, "That's so cool!" Astronomers went, "Yeah, but we need to sort our rocks."

So the definition was born.

A dwarf planet's not just about size. The only change between the classification of a dwarf planet and a terrestrial planet is that a dwarf planet hasn't cleared the neighbourhood around its orbit. So, Ceres wanders along in the Asteroid Belt and Pluto and Eris and Sedna and company wander about in the Kuiper Belt.  (Trojans don't count, because they're gravitationally shepherded.)

Our Moon, as shot by Your Truly.
Refinement #1:  If an object meets the above criteria, but doesn't clear it's orbit, it's a dwarf planet.

I notice you didn't ask about the Moon (any of them). Couldn't the 2006 planet definition qualify them as well?

Enter Refinement #2: If an object is in orbit around another object, it's a satellite (aka a moon).

Just thought I'd mention this, as we have moons (like Ganymede) that are bigger than Mercury and Pluto. But, as Ganymede and her sisters are in orbit around Jupiter, our Luna (Moon) is in orbit around Earth, and Titan and his mates are in orbit around Saturn, we're calling them satellites.

So, what about rocks that aren't round and aren't orbiting anything else?  We call them Small Solar System Bodies (SSSBs).  These include asteroids, comets, pebbles and anything else with a gravitational connection to the Sun.

So go outside tonight and look up. Can you spot any planets?

Want to know if that bright light up in the sky is a planet or a star? Easy; stars twinkle. Planets don't. (If the light blinks regularly and is moving, it's a plane. If it grows bright then fades and is moving, it's a satellite. If it flares up really bright, enough that you could see it during the day, and lasts several weeks before fading, it's a supernova. If it's fuzzy and grows a tail, it's a naked-eye comet. If it's sudden, really really bright, and takes up your whole field of vision, it's the flashlight of a police officer who's wondering why you're laying on the ground staring up at the sky.)

So, want to know what planets are currently up?  Why, all of them, if you know where and when to look.

The early evening sky favours us with a glimpse of Mercury in Pisces. Uranus is also close by, but twilight might be too bright at the moment to spot it well. (Give it a go in about six months' time. Under the right conditions, Uranus can be spotted with the naked eye and some skill in very dark skies. But if you've got binoculars or a telescope, I recommend this for better luck.)  Mars isn't too far behind in Aries.

My wee shot of Saturn.
A couple of hours after sunset should give you bright Jupiter in Virgo, rising in the east. While easily the brightest planet in the sky right now, you'll really have a show with binocs or a telescope, because you'll be able to spot the four Galilean moons and maybe even see banding.

You'll have to stay up late, or get up early to see Saturn between Scorpio and Sagittarius. This year and next year is excellent to view Saturn through a telescope, as the rings are pretty much as full on tilted our way as they get.

Neptune is a morning star in Aquarius and Venus is close by, just before dawn.

Her Grace loves to stare up at the sky, and does so nearly every single night.

Tuesday, 18 April 2017

O is for Orion

Orion has got to be my favouritest constellation. It's so big and obvious and has so many nifty features that makes it ideal for introducing people to astronomy.

Orion sits right over our equator so it's visible to most of the Earth, making it accessible to pretty much every human. Even if you're at the North Pole or in Antarctica, you will still be able to partially view Orion.

Honestly, I don't know where to begin in sharing the awesomeness of this constellation. I'll touch on a few things, but leave the rest of the exploration of this fabulous constellation to you. Right now Orion will be sitting low in the western sky, just after sunset.

On a planisphere, it looks like this:

In the sky it looks like this:

Best viewing time: January, when it's high in the sky, but not too late at night.

The major stars are called:

  • Betelgeuse (obviously red)
  • Rigel (obviously blue)
  • Bellatrix
  • Mintaka
  • Alnilam
  • Alnitak
  • Saiph

The Orionid Meteor Shower in October is thanks to Halley's Comet.

There are lots of nebulae in Orion (known collectively as the Orion Molecular Cloud Complex), but the Orion Nebula can be seen with the naked eye. It forms the sword hanging from Orion's Belt.

The Horsehead Nebula is a dark nebula, like we talked about yesterday. Use your telescope to see this one.

Because Orion comes in upside down in Australia, the belt and sword become an asterism called The Saucepan or The Pot:

I love Orion. What's your favourite constellation and why?

Her Grace will also observe Orion in July, when it reappears in the sky in the early-morning before dawn.

Monday, 17 April 2017

N is for Nebula

A nebula (Latin for 'cloud') is a cloud of hydrogen, dust and other stuff in outer space. While the Interstellar Medium (aka the ISM, aka 'the space between stuff') tends to have a density of a few molecules per cubic centimeter, a nebula can be hundred times denser than that. (Still, compare it to the Earth's atomosphere at about 1019 molecules per cubic centimeter.)

Some nebulae are essentially cold hydrogen clouds. An H I region is a neutral atomic hydrogen cloud and an H II region is a cloud of ionised atomic hydrogen (or a bunch of floating protons. Fun, huh?).

You can also get molecular clouds, which are exactly as they sound--clouds of molecular hydrogen, which are ideal for star formation. (Apply your Jeans mass and Jeans length here.)

There's planetary nebulae, which have nothing to do with planets (blame Herschel). These brightly-glowing nebulae result from an old low-mass red giant star puffing off it's outer layers as it dies. Planetary nebulae are a good way for a star to release the products of its fusion--namely, all the elements they synthesized up to iron.

They glow not because they're still undergoing fusion, but re-emitting the light from stars--including its central star. This is why so many of them look like pretty eyes.

Ring Nebula:

Lemon Slice Nebula:

 Eye of God Nebula:

This one looks like Sauron:

Supernova remnants occur when large stars (more than 8 solar masses) end their lives by going boom, er rather, when they go B O O M!!  Becuase of this, they tend to look a bit more scatter-shot than planetary nebulae.

the famous Crab Nebula:

Puppis A:

Now, we know these nebulae are supernova remnants because for a few of them, humans actually witnessed and recorded the supernova that created them. The Crab Nebula went boom in 1054AD and Tycho's Supernova happened in 1572.

Most nebula are visible because they re-emit or reflect light, but some nebula, like dark nebula, are absorption nebulae with enough dust and density to block out any light. Unlike the light hydrogen clouds, these tend to be metallic or 'dirty', with lots of elements and molecules in them.

We know about them because they often block out light and appear as a dark splotch against a brighter background.

Coalsack Nebula, located in the Southern Cross constellation:

While they might not be as visually interesting as their emittive or reflective cousins, don't give them any side-eye, though. These nebulae are as important as their sisters for star formation.

Speaking of star formation, here's a Hubble picture of the Orion Nebula with several young stars:

In conclusion, nebulae are clouds, often left over from the death of stars, that are capable of birthing new stars.

Hardcore: Nebulae.  Have fun and knock yourself out.

Her Grace is glad she doesn't have to die and go boom in order to give birth to promising young stars.

Saturday, 15 April 2017

M is for Mars

Yep, you get a bonus post for today to celebrate half-way through A to Z. Let's talk about Mars.

We know more about Mars than any other planet, with the exception of our own homeworld of Earth. We've stared at it through telescopes, sent orbiters and landers, and are even planning manned missions. We are doing everything we can to learn as much as possible about Mars.

What intrigues us so about this little Red Planet? The possibility that humans could live there.

Once we learned how torridly hot Venus was, and how cruel she could be to our vehicles, we kind of lost interest in her and put all our focus to Mars. Don't mistake me, Mars is also contrary when it comes to Earth's metal go-seek-ems. The Mars Curse eats about half of what we send there. Still, we persist because, by gum, we're humans!

Ever since we first peered at Mars through telescopes and saw what might be seasonable variability, we can't help but turn our attention to it. At first we thought the changes might be evidence of a growing season, then we saw canali (channels), which got mis-transliterated to "canals". Imagine our disappointment when the Mariner 9 missions sent us back images of a dry, desolate, pockmarked world. Broke our hearts. We were so hoping it was host to life.

But we haven't given up yet. As we map Mars, we've discovered a vast system of river channels and possible lakes once upon a time, and we've detected water ice in the polar caps.  While the low atmospheric pressure of Mars precludes any liquid water on the surface, we believe water may have flowed there at one time, maybe even oceans (aka the Wet Mars theory). The Viking landers had an astrobiological component, and every lander since has been searching for water, a necessary chemical for life as we know it. It is still possible that extremophile life could be extant on Mars, we just have to know how to find it.

As for human occupation? Living on Mars still captures the human imagination (Mark Watney, anyone?). I know Elon Musk has a plan, there's the Mars One project and  NASA's consideriing a manned Mars mission, though you might have to wait for the next hiring window to open if you're interested in going. (Also astronauts don't make as much money as you'd hope they would.)

Until then, we'll observe it from afar and send more robots.

There's so much we could talk about on Mars, from its volcanoes to its (lack of) magentosphere, to its iron oxide redness to its thin atmosphere to its damp past and more. I favour a Wet Mars theory, though I won't dismiss a White Mars theory.

Hardcore about Mars, because why would you want it any other way:

What do you love most about Mars?
Do you think we can find extant life?
Should humans create a long-term colony on Mars?

Her Grace is happy to talk about Mars anytime. She's written several post-grad papers about it.

M is for Moon

How can you blog about astronomy and not mention the Moon?

Other than the Sun, the Moon is the most obvious celestial object in the sky. It's mentioned in every human culture since record-keeping began. We've dreamt about it, wrote songs and poetry about it, and eventually got to visit there.

The Moon is the only solar system body humans have visited. If I was an astronaut with an opportunity to walk on the surface of the Moon, I think I'd be most useless, as I'd go all fangirly and rolling in the lunar regolith. Yes, I am a prime candidate for space tourism.

We know lots about the Moon simply due to proximity. We can see it with the naked eye, which makes studying it so much easier.

Facts about the Moon

Distance from Earth: average 384,400 km (or 1.28 lightseconds)
Circumfrence: 10,921 km
Gravity: 1.63 m/s2 (one tenth of Earth's)

Facts are really boring, aren't they?

Cool Facts about the Moon

The Moon it tidally locked to Earth. That means it only shows the one side. The rotation of the Moon matches the revolution of the Moon about the earth. However, due to its elliptical orbit, it does this funny little swinging dance called libration.

The far side of the Moon is often called the dark side of the Moon, not because it's blocked from the Sun. In this case, the word "dark" means "unknown". The far side of the Moon gets its fair share of sunlight, especially during the new moon phase. Until 1959, we had no idea what the far side of the Moon looked like. (It looks like this:)
Note the dearth of maria. Unlike the near side of the Moon,
there's very few cooled lava pools. I find it ironic that the "dark" side of the moon
has a greater albedo than the near side.

Because of the US and USSR's space race to get to the Moon, in the name of peace, an Outer Space Treaty was agreed upon.  Most countries have become party to this treaty. Part of that treaty states that the Moon does not belong to any country, but is free for peaceful exploration and use. (Also: no weapons of mass destruction allowed.)  This treaty is the basis for international space law. (Space, technically, begins above the Kármán line at 100km above sea level.)

What do you love about the Moon, our nearest and dearest space neighbour?

Her Grace loves the moon when she can stare at it and hates it when she's trying to stare at other stuff. For something with incredibly low albedo, it sure can be a source of nocturnal light pollution.

Friday, 14 April 2017

L is for Lightyear

"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space."
--Douglas Adams

Space is so big, we measure it in lightyears (ly). Don't let the name fool you. It's not a measurement of time, but distance. A lightyear is the distance light can travel (in a vacuum) in a year (365.25 Earth days).

How far is that? Exactly 9,460,730,472,580,800 meters (or you can round it up to 9.461 x 1015 meters).  Yep. That's really big. (Why measure it in meters instead of, say, kilometers? Because the meter is a basic unit of Système International. Makes calculation easier and more precise, I promise.)

If that number makes your head spin, sit down, rest awhile and let your brain chemistry reset itself.

Want an easier number to handle?  An astronomical unit (AU) is the distance from the Earth to the Sun. A lightyear is 63,241 AU long.

When it comes to measuring distances, astronomical units tend to be used for stuff within our Solar System, lightyears for the local neighbourhood of stars, and parsecs for everything else. After all, space is really, really big.

A parsec is about 3.26 lightyears. Why the strange number? Because of how we measure faraway stuff.

I'm sure you've played with parallax in high school science, where you hold out your thumb, look at a distant tree with one eye closed, then switch eyes, noting how your thumb appears to move compared to the tree. That's how we measure stuff in space, only we use, the month of June as one eye and the month of Decmeber as the other eye, a nearby star as our thumb and a faraway star as the tree.

Works like this:
A parsec (pc) is the distance that one AU subends an angle of one arcsecond. An arcsecond is 1/3600 of a degree from a circle. As you know, 360 degrees make a circle. (Parsec is an abbreviation of the "parallax of one arcsecond".) If you understood all that, cool. If not, just stick with 3.26 lightyears, as you probably will never need to calculate parallax.

So, how far away from us is stuff?

  • Alpha Centauri (nearest known star): 4.6 lightyears (ly)
  • Distance to the star Bellatrix (in Orion): 244.6 ly or 75 parsecs (pc)
  • Distance from the Earth to the centre of the galaxy: about 26,000 ly or 8 kpc (kiloparsecs)
  • Milky Way Galaxy is 100,000 ly or about 30 kpc wide.
  • Distance to Andromeda Galaxy (nearest major galaxy): 778,000 parsecs (778 kpc).
  • Farthest known galaxy, GN-z11: 13.3 billion lightyears (3,985,819 kpc) 

And that's about as far as we can see. For all we know, there is more stuff out there. We honestly have no idea how big the Universe is.

No hardcore stuff today, unless you want to convert kiloparsecs to meters. I think I've given you enough to keep your head spinning for a while.

Even Her Grace likes to take a break now and then.

Thursday, 13 April 2017

K is for Kelvin, or how we measure temperature in the universe

So yesterday I inflicted math on you and suggested you choose a temperature for a cloud of hydrogen in outer space.  Day before I enforced somewhat easier math on you, but only gave you a temperature in Celsius.

And all the Americans stuck out their lower lips and whined, "But what's that in Fahrenheit?"

Nuh-uh. I am not going to give you any temperature in Fahrenheit, now or ever. Real scientists calculate in Kelvin, as it's one of the base units of Système International. (Degrees Celsius are often used when dealing with relative temperatures and kelvin are used with absolutes.) Astronomers, on the big scale, prefer to measure in Kelvin (K), because we often deal with extremely hot stuff (blue stars at 30,000 kelvin) and extremely cold stuff (hydrogen clouds at 5 kelvin).

What, you say?  Who's this Kelvin dude?

William Thomson, 1st Baron Kelvin was a 19th century scientist who got elevated to the peerage for his marvelous work in thermodynamics. He was quite famous, enjoying the kind of fame and fortune a Kardashian can only dream of. Yep, even Scottish nerds can be meritocratically famous.

He expressed a need for an absolute thermometric scale that went from absolute zero on up. Fahrenheit (imperial) and Celsius (metric) were both based on arbritrary temperatures (like the freezing point of water... but is that pure water or a 50/50 saline solution? and the temperature of the human body, and boiling water... but is that at sea level?).  He wanted a system that was free from such arbitrariness.  The only thing that would be absolute enough for him was the absolute absence of energy, or Absolute Zero.

Thus, the kelvin scale was born and named after Lord Kelvin.

The kelvin scale's good for measuring colour temperature, as there is a correlation between the colour of stars and their temperature.  (Remember a couple of days ago when you calculated your personal peak radiation, and you ended up shining brightly at about 900 nm in the infrared? That's what I'm talking about.)

The human body, at approximately 300 kelvin peaks in the infrared. Our lovely G2-type Sun peaks in the yellow-white visible light range at 5778 kelvin. It's hotter, so that's why it glows so much brighter than we do.

Bellatrix, one of the blue stars in the constellation Orion is a B2-type star glowing at about 22,000 kelvin. But if you go around claiming how hot Bellatrix is, people might wonder if you're interested in Helena Bonham Carter. Bore them with math and science instead.

Wanna go hardcore? Use Planck's law to calculate what temperature you'd have to be to start glowing visible red (about 650 nm).

Wednesday, 12 April 2017

J is for Jeans Mass and Jeans Length

Essentially, the Universe is a bunch of hydrogen floating about and occasionally clumping together.

You're like, "Dude! No way!" And I'm like, "Way!" And you're all, "Nuh-uh!" And I'm all, "Yuh-huh!" And you go, "But it can't be just hydrogen. There's clumps of stuff!" And Sir Issac Newton goes, "Why's there clumps of stuff? There shouldn't be (but there is! I see clumps of stuff!)" and James Jeans said, "Strewth, there's clumps, because science!"

And he went on to explain how the clumps came to be.

See, our buddy Issac knew just enough about science to question the issues regarding stuff (in this case, hydrogen) clumping together.

So, we've got a whole lotta hydrogen floating about out there in a giant molecular cloud of the stuff. As you know, as soon as a hydrogen atom (or molecule) gets close enough to another one, gravity draws them together.  Get a whole lotta atoms/molecules together, and gravity draws them in. Ah, but here was Newton's quandary: Get enough of them together in a dense enough clump, and the gas pressure would force them away from each other (like how a balloon gets puffy when you fill it). Yet, we've got lots of lumps of stuff. How did that happen?

Our buddy Jimmy figured that if there were clumps, there had to be a reason. He worked out that there was a certain point where, if you got enough atoms togethers, their combined gravity would be stronger than gas pressure, and clumps would happen.

When gravity is equal to or lesser than the gas pressure, nothing happens. When the gravity is stronger, then you get clumps of stuff like stars. The greater the mass of the cloud, the smaller its size, and the colder its temperature, the more unable it will be to resist gravitational collapse. (Temperature? Sure Temperature causes pressure, which is why a boiling kettle whistles while a cold one does not. If your cloud's got a fever, it's gonna need more mass to collapse.)

There was a certain point that this swapover happens. We call that the Jeans Mass (after our buddy Jimmy).

Jeans Length is the radius of a cloud where this collapse will start to happen.

And this is how baby stars are born. As we already know, stars are powered under fusion, which drives nucleosynthesis, and when the stars die and go boom (for various kinds of boom), it scatters all its soot and ash, which then clumps together into rocks and stuff through a process called accretion.

Hey nerd! Go hardcore and do the math:

Jeans Mass:

kB = Boltzmann's constant
T = temperature of the cloud (Kelvin)
r = radius of the cloud
μ = mass of your hydrogen atom
G = gravitational constant
ρ = cloud's mass density (cloud mass divided by cloud volume)

(Wanna cheat?)

Jeans Length:

Same variables as above, with k being the Boltzmann's constant and ρm being the cloud's mass density.

Does math make things easier or harder for you?

Her Grace does not like math, but she will do it all the same.