Z is for Zodiac

This isn't about telling your horoscope, but knowing where the Sun is at any particular time of the year. (Those born under the sign of Ophiuchus the Snake-bearer know that Astrology is not a science because nobody has been able to prove its reasoning through the scientific method.)

In Astronomy, there are thirteen constellations that reside along the ecliptic (the path the Sun takes through the sky year-round). This means as the Sun moves through the sky from month to month, it will be found within the boundaries of certain constellations.

Astrologically, the sky is divided into twelve "houses" of 30° each. In astronomy, the constellations of the astronomical zodiac is not so evenly divided, and we've thrown in one more constellation because the Sun does spend some time in one corner of it. The planets and the Moon also move within the ecliptic.

Because the Earth is tilted, the ecliptic doesn't match up with the equator except on equinoxes twice a year.

The red line is the path the Sun takes. The green line is the equator.

When it comes to measuring where stuff is in the sky, there's two axes of celestial coordinates: declination (DEC) and right ascension (RA).

Declination measures north/south in degrees: North (90°) to Equator (0°) to South (-90°).
Right ascension measures eastward from a point of origin (the vernal/spring equinox) in hours, with there being 24 hours in a full circle, due to the rotation of the Earth. This is because astronomers measure right ascension by timing when an object passes through the highest point in the sky, or the meridian. Each hour is about 15° in width.

Anything anywhere in the sky can be given a set of coordinates.

Looking at the star of Betelgeuse:  DEC +07° 24′, RA 05h 55m

This means Betelgeuse sits about seven degrees north of the equator, and on the spring equinox (21 March), it takes about five hours and fifty-five minutes before it reaches the meridian of the sky.

Let's look at the Zodiac astronomically.

Here's the actual map:

As you can see, the constellations take up different areas of real estate. Sometimes the Sun will spend as little as a few days in some constellations and several weeks in others.

Right ascension starts on the spring equinox and is also called the "First Point in Aries"... however, due to precession, the spring equinox actually lies in Pisces today!  Here's how much it's shifted over the past seven thousand years:

(A brief word about something called precession: the Earth wobbles on a long-term cycle of about 26,000 years, where her north pole points to different parts of the sky. (Polaris isn't always going to be the North Star.) Because of this, the constellations have shifted from where they were originally observed a few thousand years ago, and don't line up with the calendar we know and love today. Your astrological zodiac sign no longer corresponds with the constellation of the same name. Sorry.)

We'll start on the vernal equinox and have a look at all the Zodiac constellations.

Constellation:	Coordinates:	Sun enters/exits:	Time in constellation:
Pisces	RA: 1h DEC: 5°	12 March – 18 April	38 days
Aries	RA: 2h DEC: 15°	19 April - 13 May	25 days
Taurus	RA: 4h DEC: 15°	14 May - 19 June	37 days
Gemini	RA: 7h DEC: 20°	20 June - 20 July	31 days
Cancer	RA: 9h DEC: 20°	21 July - 9 Aug	20 days
Leo	RA: 11h DEC: 15°	10 Aug - 15 Sept	37 days
Virgo	RA:13h DEC:0°	16 Sept - 30 Oct	45 days
Libra	RA: 15h DEC: -15°	31 Oct - 22 Nov	23 days
Scorpio	RA: 17h DEC: -30°	23 Nov - 29 Nov	7 days
Ophiuchus	RA: 17h DEC:-30°	30 Nov - 17 Dec	18 days
Sagittarius	RA: 19h DEC: -25°	18 Dec - 18 Jan	32 days
Capricorn	RA: 21h DEC: -20°	19 Jan - 15 Feb	28 days
Aquarius	RA: 22h DEC: -10°	16 Feb - 11 March	24 days

Which is your favourite zodiac constellation?

What is your astrological zodiac sign, and what is your astronomical zodiac constellation (based on your birthday)?

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Her Grace is fond of Scorpius, because it really does look like a scorpion.

If you wish to explore more Astrological applications of the Zodiac, check out Chris Votey's "Madness of a Modern writer" A to Z challenge where he's been combining the Greek and Chinese Zodiacs to create character profiles.  It's been fun for me, from a writer's point of view.

Y is for Year

Happy Birthday to you, if you happen to have a birthday this year. (Sorry, Leap Year Babies. No birthday cake for you.)

Essentially, a year is the time it takes for the Earth to go around the Sun. So yes, Venus has a Venusian year (0.6a) and Mars has a Martian year (1.88a). But for the purpose of today, I'm going to talk about how the Year is a standard unit of measurement.

Astronomers need a way of measuring things. Since there's no standard galactic measuring stick for, well, everything, we've taken what's most familiar and made that our basis. For example, the mass of planets is measured by the mass of the Earth (M_⊕) and the mass of stars is measured by the mass of the Sun (M_☉). Short distances are measured by Astronomical Units (AU), which is the mean distance from the Earth to the Sun and long distances are measured by lightyears (ly) (the distance it takes for light to travel a year).

In astronomy, one measurement of time is the Julian year (symbol: a), which is exactly 86,400 seconds (as seconds are the base unit of time in SI). This equates to about 365.25 days, if that makes your brain hurt less. That's a very familiar number, with our calendar years being 365 days, except for every four years, when we add up the .25 of a day, and tack on an extra Leap day, so our days can sync up with our years. Our current Gregorian Calendar is based off this cycle.

While we've known about this extra quarter-day for a few thousand years, we didn't realise exactly how precise we'd not calculated it, so our earlier calendars had a bit of drift going on, and occasionally needed serious correction. That's why the ten days of Oct 5-15 1582 AD (CE) don't actually exist. Also why Ramadan appears to drift in relation to our civil calendars. And if you were born in Sweden in February 30, 1712, I am very, very sorry for you. Here's three hundred years' worth of birthday cake to make up for that double-leap day.

Let's put calendars aside and talk astronomy.

Julian years are used to measure duration. For example, how long would it take light to reach us from Alpha Centauri? About 4.6 years. (A Julian year is what they use to calculate a lightyear.)

How long does it take for Jupiter to go around the Sun (aka a Jovian year)?  11.8618 (Julian) years.

There's other types of years such as the sidereal, tropical and draconic years, used to measure stuff in relation to Earth but for general astronomical purposes in measuring duration in the rest of the Universe, we prefer the Julian year. Feel free to go hardcore if you wish regarding the other year types.

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Her Grace does not mind collecting years as she goes along. Old age is a privilege denied to many.

X is for X-ray

Finally, an AtoZ blog entry where I don't have to stretch to find an entry.

We've talked a bit about the electromagnetic spectrum during the A to Z--Radio, Infrared, Visible (Optical) and Ultraviolet--because light is primarily the only tool we have to explore the universe.

While other bloggers are really pushing it to find something for the letter X, here's something that comes naturally to astronomers: X-rays

We all know about X-rays for their medical uses: broken a bone or been to the dentist, chances are you had an X-ray photograph taken.

X-rays are cool because they can penetrate certain types of matter and show us other types. This is because they're highly energetic. Naturally, this is a good thing for astronomers. We like looking at high-energy things.

X-rays were discovered in 1895 by Wilhelm Röntgen. Here's his original paper: German,  English Translation

"Hand mit ringen," Will said.
His wife said, "I have seen my death!"  Drama queen.

In fact, X-rays are often called Röntgen rays. What did Wilhelm Röntgen call them?  X-rays, with X standing for "mysterious", because he really wasn't sure what they were at first. Eventually he and a few scientists figured it out.  A few early articles about Röntgen's mysterious X-rays.

And, like any other scientist that thought science stuff was nifty, he played around with it, and even freaked his wife out by using her hand as a guinea pig by taking the first X-ray photograph.

This was fascinating, as it's really the image of an X-ray shadow, as the minerals of the bones block out the X-rays. Lead is also good for blocking out X-rays.

So, what makes X-rays so useful for astronomy?

Remember how stars come in different colours, depending on how hot they are?  If you boost the temperature of an object in outer space to waaay hot (more than a million Kelvin), its peak colour goes on beyond blue all the way up into X-rays.

This makes X-rays really useful for detecting high-energy events and objects.  Neutron stars and accreting black holes emit X-rays. Supernovae emit X-rays. (Stars emit X-rays, as they emit through the whole EM spectrum, though not to the same degree the Really Powerful Stuff, like active galactic nuclei, does.) Want to know where all the moving and shaking is happening in the universe?  Look for the bright X-ray spots.

Now, X-rays are absorbed by our atmosphere (thankfully), so any X-ray observatories need to be in orbit, like the Chandra X-Ray Observatory.

Here's some cool pictures taken in X-ray:

Looks very different from the hand mit ringen, as these are not images of the shadows of X-rays, but rather the emissions of X-rays. That's why they're so bright.

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Her Grace once calculated how much X-rays she emitted. Answer: not much.

W is for Wobble

Lots of things wobble. This is due to gravitational influence by something else.

Mass has gravity, and gravity is a very social thing. Two bits of mass spy each other across the room (or the universe) and try to get closer. If they get close enough, they end up in an orbit around each other, possibly in a spiral until they collapse together, though this doesn't always happen if the escape velocity is sufficient to keep them from falling into each other.  (That's what most orbits are: falling, but failing to hit the ground.)

The centre of gravity about which these object spiral about is called the barycenter.

Looks like this:

Do-si-do.  The barycenter is the red cross in the middle.

When the objects are of a similar size, the barycenter will be somewhere in between the two objects, as is the case with Pluto and Charon:

Pluto and Charon and their barycenter, the cross in the middle.

Pluto has a small orbit around the barycenter while Charon has a larger one. So they kind of wobble like an uneven barbell.  Because the barycenter is outside of Pluto, some people would like to call Pluto/Charon a double planet, rather than a planet and a satellite. I'm cool with that.

When one object is distinctly more massive than the other, the barycenter will be located within the larger object, such as the Earth and the Moon:

This gives the Earth a little bit of a wobble, instead of a full-on do-si-do.

We noticed our Sun has a bit of a wobble, due to the gravitational influence of the planets about it. In fact, the Sun's wobbled quite a bit:

Notice how sometimes the barycenter's inside the sun and sometimes its not?

Yeah, not surprising, considering what we know about gravity. Then some clever soul thought, if our Sun wobbles due to planets pulling on it, wouldn't other stars wobble for the same reason?

Whoa! Mind blown! So we started looking at nearby stars with this Wobble Method (also called Radial Velocity or Doppler Spectroscopy Methods) to see if they had a wobble.

Ohmigosh, they did! Thus, we discovered exoplanets.  And we said, "That's so cool!!!" (Then we felt slightly stupid because we hadn't figured something so simple out until now.)

Gamma Cephei Ab was the first exoplanet detected in 1989 (confirmed in 2002), and since then, we've uncovered evidence for thousands of exoplanets.

Nice to know we're not alone.

Now, there's lots of other methods for detecting exoplanets, but it all started with noticing how gravity made things wobble.

Wobbling isn't just for detecting exoplanets. Lots of other discoveries are due to the observation of wobbliness.  Go hardcore and check out wobbliness from asteroids with moons to entire galaxy clusters.  Even browsing through the list of titles is fascinating. Never be afraid to read an abstract. Save your freaking out for the paper itself.

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Her Grace believes that love makes the world go round, but gravity rules the universe.

V is for Visible Spectrum

Until the past century, pretty much all astronomical work took place with the observance of the visible spectrum. MK-1 Eyeball (the naked eye) was how observation took place.

The visible spectrum isn't terribly big--only 390 to 700 nm--considering just how wide the electromagnetic spectrum is. Yet within that short range, we've been able to accomplish some magnificent astronomy.

Before we discovered calorific rays (infrared) or chemical rays (ultraviolet), we were playing with the visible spectrum. Spectroscopy allowed us to divide up light into its different wavelengths and observe the universe. You can tell a lot about the composition of something by the frequency and amplitude of the light it emits.

Early scientists (like Herschel), noticed that certain spectra had dark lines. These are absorption lines, when atoms (like hydrogen) absorb certain light frequency.

Johann Balmer noticed that hydrogen absorbed certain frequencies. This helped us discover just how much hydrogen was out there, and also determine the nature of the hydrogen atom itself. (Hardcore: the absorption lines happen when a hydrogen electron absorbs that photon's energy, thus causing it to jump or transition to the next electron shell.)

All elements exhibit absorption lines. While some are seen only "off-stage" (ie, in the infrared or ultrviolet or beyond, especially if red-shifted), many can be seen in the visible spectrum.

Here's the visible spectrum of the Sun. As you can see, there's plenty of dirty metals lurking within our nearest and dearest star. (Can you find sodium?  Hint: it's orange.)

Click here to embiggen.

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Her Grace is best viewed in the visible spectrum.

U is for Ultraviolet

Yesterday we talked about lightbuckets and the light we can capture in them. Today we'll talk about one of those frequencies, Ultraviolet.  Most people know about ultraviolet from sunscreen commercials, and good old Slip Slop Slap campaigns.

In 1800 Herschel discovered Infrared (he called them Caloric Rays because they felt warm). Like any good scientist, he wondered if something similar could be found on the violet end of the spectrum. Alas, when he set up his thermometer on beyond violet, he didn't detect any heat. Oh well, he said, and focused on what he knew.

Then in 1801 Johann Wilhelm Ritter refused to be daunted by the violet end of the spectrum. See, he'd read Herschel's paper, and thought that Herschel hadn't gone far enough in his investigations. As a chemist he was familiar with the photosensitivity of certain chemicals. He knew that silver chloride turned dark when exposed to sunlight, reacting stronger to blue light, rather than red.

When he exposed a piece of paper coated with silver chloride to a spectrum, he discovered the strongest reaction was in the “invisible” side of violet light. Because of the chemical reaction, he named this invisible band of light “deoxidizing rays” or “chemical rays”. Essentially, he was one of the first to create a "photo-graph", or a literal recording of light.

He'd discovered Ultraviolet.

But what he also discovered was ionising radiation.

The electromagnetic band is divided into two different kinds of radiation: non-ionising waves, like radio waves, and ionising radiation, like X-rays.

Ionising radiation is radiation that's strong enough to knock electrons off an atom or molecule. The ability to cause a reaction in a chemical such as silver chloride is due to ionisation. It's the scary stuff that can potentially damage DNA and cause cancer.

Fortunately, most of the harmful ionising radiation (from UV on up to gamma rays) gets filtered out by our atmosphere. Still, visible light and some near UV get through. These are the frequencies that start to chemically affect stuff. (This is also why you don't store your beer in sunlight.)

Non-ionising radiation like radio waves can pass through our atmosphere, but doesn't pose a threat to us. (FYI, the radio wavelengths that mobile phones use is safely in the radio waves range. Mobile Phones do not cause cancer. Feel free to carry them in your bra.)

Ah, so what's the benefit of the ultraviolet spectrum in astronomy? It's good for detecting hotter objects. UV is very good for detecting chemical composition, very old stars or very young stars, and for identifying star-forming regions, which denotes active galaxies.

This UV images of the Andromeda Galaxy (M31) shows it's active star-forming areas:

When the variable star Mira was imaged in UV by GALEX in 2006, scientists were amazed to discover it had a tail. Mira moves through space rather quickly for a star (130km/s), so fast, it even has a bit of bow shock in the interstellar medium (ISM) and a tail of matter streaming behind it for thirteen lightyears:

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Her Grace likes to think of UV as the "hot and bothered" frequency.

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?

Sure.

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.


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

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

Size

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.

Colour

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.

O B A F G K M
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.

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

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. http://skatelescope.org/

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.

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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.

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?

• Easy tricycle level (with training wheels)
• Mountain bike level (for the average science-curious layman) 
• Hardcore Harley Davidson level:
• First papers on quasars
• Subsequent papers on quasars
• More modern explorations on quasars 

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

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.

References

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





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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.

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

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:

Hardcore:  All the cool stuff happening in Orion.

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

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

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.

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