FirstLight Astronomy Club

33°29.6'N / 117°06.8'W / 1190 ft.

Probing Perseus

There is a hideous monster right above our heads tonight!!! Well… maybe not a monster. More like the head of a really ugly woman. And admittedly you kinda have to use your imagination to see it. To be honest, probably the best you can make out is her eyes. Make that her eye - singular.

I guess it’s not really that frightening after all.

Well, let’s have a nice little discussion anyways on the constellation directly above our heads tonight, the array of stars referred to as Perseus.

To find it is an easy task. Go out in the early evening and face south. Look up high and find the Pleiades, that famous little cluster of stars often miscalled the Little Dipper.

Just a few degrees “above” the Pleiades – about the width of three fingers held at arm’s length – are two stars that represent the famous winged feet of Perseus.

Continue to follow that direction over your head with the line of stars that curves slightly to the right. Those stars are Perseus’ leg and torso. The bright star of the group, half a handspan up, is called Mirfak. This name comes from the Arabic “Marfik al Thurayya,” loosely translated as “Elbow Nearest the Many Little Ones.” The elbow belongs to Perseus, those “little ones” are the Pleaides.

Keep going a little further up, without wrenching your neck, to see the stars of Perseus’ head. You’ll know you’ve gone too far in one of two ways: either you will come upon the famed W of Cassiopeia or you will have fallen over backwards and bonked your head on the ground.

Many are familiar with the story of Perseus, which is a long sweeping epic to say the least. But the bottom line as far as we are concerned is that Perseus was the son of a looker named Danae. Danae was a beauty, and the god Zeus was a womanizer, which is how Danae came to bear a jovian child and name him Perseus.

Through a series of stories and adventures Perseus acquires a special sword, a shiny new shield, and some winged sneakers that would make Michael Jordan envious.

He eventually visits the Sisters Gorgon, three not-too-attractive siblings who shared one eye and one tooth between them. Really. And there he slays the one named Medusa, by lopping off her snakes-for-hair head.

He goes through some more escapades, not least of which are rescuing and marrying Andromeda, and accidentally killing his grandfather.

For all his heroism he is granted a place in the sky just overhead tonight. But I neglected to mention that he is holding in his hand his putrescent prize. Just to the right of the curved line of stars is the horrifying head of Medusa!!!

The bright star just to the “right” of the line, halfway up, is the hideous eye of the beast. This star is called Algol, from the Arabic “Al Ghul,” which means Mischief Maker.

Now this star has a pretty fascinating little tale to tell itself. It is a binary (two-star) system just 95 light years from us. The two extremely close stars revolve around each other every 69 hours.

We can’t actually see two stars there but we know they are there and going round each other because the dimmer one actually eclipses the brighter one, causing Algol to dim every 2 days 20 hours and 49 minutes. It is an eclipsing binary. It fades by a factor of about three for about 10 hours (as the dim star passes in front of the brighter) and then brightens back to original magnitude.

Why, it’s almost as if Medusa is winking at us! Ooooh… scary!

Although they have no single hero story as was handed down to us in the West, the Chinese have some great stories about this part of the sky.

The arc of stars that is Perseus’ torso is called T’ien-tchouen and Tsi-choui, which represented a boat and rising waters respectively. These were reminders of the imminent flood season.

Ta-ling were the series of stars circling around Algol. This was the great trench where many prisoners killed in mass executions in August were buried together. Tsi-chi, our Algol, is the great heap of corpses waiting for the trench. Mmhmm…

But wait! It gets even more gruesome.

Astronomers in ancient times were more astrologers than anything else. They needed to know the stars and other heavenly bodies to forewarn the king when bad times might be round the corner, or announce the perfect time for make war, or when to make the next hair appointment.

Well, apparently there were these two Chinese court astrologers, Hsi and Ho, who were too busy enjoying the “good life” of court astrologers to notice an upcoming solar eclipse. Bad move.

Usually the Chinese people were warned of such an event and got out their pots and pans and beat the heck out of them, scaring away the dragon who was eating the sun so that the great beast would burp it back up.

No warning this time and the dragon nearly got away with eating the sun and running away with it. The Emperor had their heads for that faux pas, and the melons of Messrs. Hsi and Ho were put in the sky as reminders to future astrologers not to mess up!!!

Their heads can easily be seen with binoculars as the famous and beautiful double star cluster in Perseus, near the top of the arc of stars.

I use the story of Hsi and Ho in my class as object lessons for the consequences of not doing your homework. Alas, it doesn’t work.

Until next time, clear skies!

Colors in the Skies

The holidays are over. It’s time to go back to school! And time for another pop quiz to test your knowledge of the cosmos! All right, no need for spitwads to the back of my head. This is just for fun, and to increase your knowledge account in the Bank of the Universe. Ready?

1. T/F Stars come in only one standard color; bright white.

Boy, you’d think so, looking at an unpolluted night sky with all the trimmings. It at least appears that all those dazzlingly sparkly things up there are white. But it’s not so.

Stars come in a wide variety of colors: red, orange, yellow, white, and blue. One question may come to mind now: Why have I, your humble purveyor of cosmic knowledge, not been institutionalized? Anyone can see clearly that there are no colored stars up there!!!

That’s actually near the truth. It appears there are no colors up there. But – sit down – most of the stars we see up there really are colored.

The fault, dear Brutus, is not in our stars, but in ourselves. Our eyes are not designed to see the blues and the red ends of the spectrum very well. The middle part of the visible spectrum, around the yellow part, we can see well, as the designers of all fast food restaurants know.

And the parts of our eyes that see color just aren’t too sensitive, either. They need a lot of energy to get them going, which is why we don’t see colors well in dark rooms.

To see the star color differences with our eyes we need to see colored stars next to each other. For example, there is a beautiful double star combo (a binary) called Albireo in Cygnus When seen through a backyard telescope one star bleeds blue, the other red.

And some stars by themselves show their true color. Aldebaran in Sagittarius shines up nice and red in the summer skies.

For truer colors one needs to use imaging equipment that is equally sensitive to all the wavelengths. That’s one reason why those images on Astronomy Picture of the Day are so colorfully stunning.

Answer: False

2. T/F The red stars are hot, and the blue stars are cold.

Most of our modern day appliances have blue colors to indicate something cold, and red to designate heat or fire. But the universe overall has its own color codes.

Stars give off energy in all wavelengths of light. But, to make a long story short, there are laws in nature that say that hot things give off a lot more of the wavelengths on the blue, high-energy end of the spectrum and not as much on the red, lower-energy end. Contrariwise cooler objects can’t spit out as much of the energetic blue wavelengths as they do the wimpier red ones. So the hotter stars actually appear bluer and the cooler stars redder.

Thus, although stars are spitting out all types of energy, what they spit out the most is what wins them their color prize.

Answer: False

3. T/F Well, then red Mars must be cooler than blue Neptune!

Planets, as opposed to stars, don’t give off their own visible light. They reflect it. And that makes all the difference in the worlds. Here’s what I mean.

Stick an iron poker in a fire for a while, and then take it out. If the fire is hot enough you’ll get the poker pretty hot, maybe even “white hot.” As it cools, it becomes yellow, then orangey, then reddish, then fades to black. The whole time that it had some color it was giving off its own light. Like stars do!

But things like planets and butterflies and hamsters named Larry and you and me don’t give off visible light. When the lights are off we are invisible.

When a light is on us, however, we reflect some of those wavelengths and absorb others. For example, a white light rains down on us all the wavelengths of light. The molecules that make up our body and clothing and everything else around are built such that they absorb some and reflect others.

If a molecule absorbs the red end of the spectrum, but reflects the blue end, it appears bluish. If it absorbs red and blues, it probably then reflects green.

It’s the same with those planets out there. They have a light source, too – our sun. Mars has compounds on its surface that reflect the redder end of the spectrum giving it that reddish-brown color.

Neptune has gases in its upper atmosphere that reflect blue light and absorb the red end of the spectrum. So Neptune appears strikingly blue.

But the colors of the planets, like the color of your clothes, have nothing to do with temperature, but with how the molecules they are made of absorb or reflect different wavelengths of light.

Answer: False.

Do better this time? Worry not if you didn’t. These are all common misunderstandings held by a lot of people, and now you are a little more knowledgeable about the universe than you were just minutes ago.

Until next time, clear skies!
Temecula Valley High School / Temecula, CA · Some images © Gemini Observatory/AURA Contact Me