Nov 10, 2013
Illustrated Astronomy Definitions
This is my 100th
piece. For number 100, I wanted to do something special --- something
that I would really love, something that would definitely be "me" yet,
hopefully be interesting or enjoyable to others.
This piece was
inspired as I was taking my cat, Trilby Kitty, for his nightly walk. It
was a beautiful, clear night with a star-filled sky (well, as many
stars as the light pollution allows). There in the sky was the familiar
hourglass of Orion which I hadn't seen in months. It got
me contemplating the difference between asterisms and
constellations and this piece was born..........
||What a constellation ought
to be. An asterism is the part of a constellation that actually looks
like what you call it. Examples: Big Dipper (of Ursa Major),
Teapot (of Sagittarius), "W" (of Cassiopeia), Hourglass (of Orion)
Teapot asterism in Sagittarius
By Eoghanacht (Own work) [Public domain], via
the most dangerous thing in the universe. A black hole is something you
basically have to be sitting on top of (in astronomical terms) before
you can get sucked in. See "Last Stable Orbit" for more details. Also see "Gamma-ray Burst" for comparison.
The Earth would have to be quite close to a
black hole to be sucked in.
If the Sun were turned into a black hole, the Earth's orbit wouldn't
even be disturbed.
From my piece "The Black Hole that (Didn't) Devour the
||Not to be confused with blazer, an item
of clothing. A blazar is an active galaxy tilted in such a way we can
see the disk and the jet.
Blazar, showing the viewing angle
By Mrbrak () [GFDL
||A really boring word to describe a meteor
so awesome it turns into a fireball and makes a sonic boom as it blasts
through the atmosphere. A bolide is what happened in Russia in 2013.
It was also a bolide that devastated 830 square miles of Siberia in the
Calling it a
bolide is a lame term for something so powerful it can cause such
massive destruction. Now Calvin of "Calvin and Hobbes" would
come up with a name with some punch like a Super-Kablooier.
those highly specialized, technical terms astronomers
like to throw around to describe stars instead of just saying
it's stars that never set so are always in the night sky.
Heaven forbid they come up with a term like "perma-view" or something
equally intuitive to describe that characteristic. No, they use a word
you have to look up and then memorize the meaning of. Circumpolar
depends on your latitude ---- at the North or South Poles every star is
circumpolar; at the equator no star is circumpolar.
is why the time
honored instruction of how to find Polaris, the North Star, is
friggin' useless for much of the northern hemisphere. Because
the instruction starts with finding the Big
Dipper is only circumpolar (always in the night sky) if you happen to
42║ north in latitude or higher which
excludes most of the United States. So if you're ever lost
and looking for the North Star you'd better either hope
you're way up north or that the Big Dipper just happens to be
42nd latitude line
By Bazonka (Based on
Image:Blank US Map 48states.svg)
imaginary figures in the sky that our ancestors must have been
some interesting botanicals to come up with because a lot of
stars don't look a thing like the figures they're supposed to
If these were connect-the-dots drawings, you still wouldn't know
what it was supposed to be when you finished.
Constellation drawings -- Click image for full
Frederi(c)k de Wit (Koninklijke Deense Bibliotheek) [Public domain], via
|Gamma-ray Burst||Unlike black holes, you don't have to be near a gamma-ray burst to take a hit ---- these can kill from thousands
of light-years away. The most intense explosions of electromagnetic
radiation there are, these bursts travel for galaxies. Lasting from
milliseconds to a few minutes, while they do last they're the brightest
thing in the universe. The long--duration bursts (2 or more seconds)
are thought to be caused by supernovas so powerful that a term
came into use to describe them, "hypernova." The short-duration bursts
are now thought to be caused when two massive bodies like neutron stars
or black holes collide. The radiation from gamma-ray bursts is so
intense, it's speculated that one mass extinction on Earth was caused by us getting hit by a gamma-ray burst.
But I still wouldn't worry about it.........even though a gamma-ray
burst happens about once a day, almost all of them originate from so
far away (as in way out of this galaxy) that they can't do any harm when they reach us. And gamma-ray bursts are rare in the Milky Way,
so even if it did happen once in the history of Earth, my
non-statistician's estimate of you dying from one of these is about as
likely as you getting struck by lightning as you go to claim your
Powerball winnings. |
Artist’s impression of a gamma-ray burst shining through two young galaxies in the early Universe
By ESO/L. Calšada [CC-BY-3.0], via Wikimedia Commons
who's seriously doubted there's other life in the universe since we
figured out those points of lights in the sky are suns too.
Incidentally, that time period covers the 20th century
when I heard a lot of speculation about if there was life "out there"
or if Earth was the only planet in the universe with life. Idiots. (The
concept that the Sun and the stars were the same dates all the way back to 450 BC
when it was suggested by the Greek philosopher, Anaxagoras. However, it
took another 2287 years, until 1838, to finally prove it.)
The Observable Universe. We're in the Local
Superclusters (marked in red) -- Click image for full size
By Andrew Z. Colvin (Own work) [CC-BY-SA-3.0
||The favorite of 1970s
science-fiction writers ---- even had
an organization, the L5 Society, named for
it. Lagrange 4 and Lagrange 5 are spots at equal distance from the
and the Moon and, in theory, any object like a space station at L4 or
L5 would stay
in place without using any fuel. In actuality, it doesn't work quite that simply.
The five Lagrange points
calculated by the French mathematician, Lagrange, in 1772. L1, L2 and
L3 are unstable.
By Anynobody [CC-BY-SA-3.0
|Last Stable Orbit
closest distance an object can orbit a black hole without being pulled
in. In astronomical terms, pretty darn close. See "Can I safely orbit a black hole?"
A safe orbit around a black hole.
Notice how close to the event horizon it is.
NASA and STScI [Public Domain] from HubbleSite.org
||Incredibly useful and intuitive term
meaning the distance that light travels in a year. See "Parsec" for
From StarChild site at NASA/
GSFC which should make this image Public Domain.
|Three terms you have to be an
astronomy buff to distinguish.....
The rock when it's flying around in space
The same rock when it enters Earth's atmosphere. A meteor only exists
for seconds or minutes.
Whatever's left of the rock when it hits the ground.
If you really want to remember how to distinguish among the three, try
Meteors have a short lifespan and "meteor" is the shortest of the three
meteorite, it was "rite" lucky to have made it all the way to the
ground. (Hey, that's no sillier than the stalactite/stalagmite
Meteoroid to meteor to meteorite
terms that show the danger of naming something before you know what the
hell it is because a supernova isn't a really large nova.
The sudden temporary brightening of a star but
the star stays intact, caused when a white dwarf in a binary star
system sucks material off the other star and nuclear fusion happens
with this new material.
A white dwarf in the process of taking matter
from its neighboring star
By NASA/CXC/M.Weiss [Public domain], via
The explosion of a star leaving behind either
a neutron star or a black hole
A star going supernova leaving behind a type
of neutron star called a pulsar
By Simynazareth at ml.wikipedia
(http://heasarc.gsfc.nasa.gov/docs/snr.html) [Public domain], via
||The answer to the question I asked
myself way back in elementary school the first time I saw a
drawing of atoms with all that empty space, "What would happen if you
squashed the atoms so tight there wasn't any empty space?" The answer
is it would turn into a neutron star.
Under the tremendous pressure as the atoms are squeezed, the negatively
charged electrons and the positively charged protons would combine to
become uncharged neutrons.
The theorized interior of a neutron star.
A teaspoonful would weigh approximately 10 million tons.
By NASA [Public domain], via
||A theorized source of comets. Something
only astronomy buffs and fans of Anne McCaffrey's "Dragonriders of
Pern" novels had ever heard of.
The Oort cloud relative to the Solar System.
By Jedimaster (Own work) [CC-BY-SA-3.0],
useless and non-intuitive term for distance in space that astronomers
are using instead of light-year because they think it sounds cool.
Technically, "an abbreviated form of 'a distance corresponding
to a parallax of one arcsecond'" (wikipedia)......yeah,
cause everyone immediately understands what that is. One parsec
equals 3.26 light-years.
Illustration of how to calculate a parsec.
The black dot at the end of the solid red line is exactly 1 parsec from
By jd (Own work) [Public domain or Public
pulsars are neutron stars, but not all neutron stars are called pulsars
---- even though they might be. A neutron star is only called a pulsar
if we can detect the beams of electromagnetic radiation from
because they're being sent in our direction. It's the astronomer's
version of "If a tree falls in a forest and no one can hear it, does it
make a sound?"
Pulsar jet seen by Chandra Observatory
By NASA/CXC/Univ. of Toronto/M. Durant, et al. [Public domain], via
However, the Wikimedia file kept crashing this page, so I
converted the file and transferred it to YouTube.
pulsar and accretion disk
A neutron star in a binary system pulls in material from its
neighboring star, causing the neutron star to spin faster until it
becomes a pulsar with a rotational period from 1-10
milliseconds (called a millisecond pulsar).
By NASA (animator: Dana Berry) [Public domain], via
However, the Wikimedia file kept crashing this page, so I converted the
file and transferred it to YouTube.
||Not the really funny cult British TV
show, but the most common star in the Milky Way galaxy with a mass
smaller, and a temperature cooler, than the Sun.
left to right: Red Dwarf, Yellow
Dwarf, Blue Dwarf, 300 solar mass star
By ESO/M. Kornmesser (http://www.eso.org/public/images/eso1030c/) [CC-BY-3.0],
||Not the full moon after the Harvest Moon
or any of the special names given to the full moons
or that album by Enya. It's a moon that orbits near or in a planet's
ring system and whose gravity "shepherds" the ring, helping to keep its
Two shepherd moons of Uranus' rings.
[Public domain], via Wikimedia Commons
||One of the best, most descriptive terms
in astronomy. The stretching (or spaghettifying) of a body falling into
a black hole.
An unfortunate astronaut being spaghettified
while drawn into a black hole.
By Cosmocurio [CC-BY-SA-3.0], via Wikimedia Commons
from the synchronized rotation seen in pairs figure skating where two
bodies rotate at the same speed and in the same direction. This type of
synchronous rotation is the reason why we only see one side of the
Moon. The moon rotates on its axis in the same length of time it takes
to go around the Earth. Also known as tidal locking.
On the left is a demonstration of synchronous
rotation. On the right is non-synchronous rotation.
By Stigmatella aurantiaca (Own work) [CC-BY-SA-3.0],
||When you type in "terminator definition"
in Google, what comes up is going to make you think of Arnold
Schwarzenegger. But in astronomy, a terminator is the line between day
and night (light and dark).
Terminator lines on the Earth and the Moon
Image taken by Galileo at a distance of 4 million miles
By NASA [Public domain], via
||Frankly, I still think TV if someone says
"Zenith" to me. But it's the highest point that is directly
overhead of the observer.
The "Z" is zenith. "Alt" is altitude. "Az" is azimuth.
"S" is the south point on the horizon. "N" is north.
By haade (Own work) [GFDL
||Don't be fooled by the common usage.
This definition has
nothing to do with that most inane of all belief systems, astrology.
It's the constellations within 8║ of the ecliptic path through which
the Sun, the Moon and visible planets seem to move as viewed from the
The outer red ring is the ecliptic path --
Click image for full size
By Tauʻolunga (Own work) [GFDL, CC-BY-SA-3.0
more of my astronomy pieces, read "The Black Hole That (Didn't) Devour the
Galaxy" or "Star Wars, Einstein and When Lucas Got It
Right" and its addendum "Difficulty Levels of Death Star Versus
Various Astronomical Bodies." Another science piece
is on the topic of population growth,"As Dumb as Deer."
Please take a moment to look through the Archive.