Epsaur Script v10 14pt

Citizen Sky
Planetarium Show / Trailer

Version 1.0 • 10 November 2009
The stars appear changeless.
On a clear, dark night, we see the same constellations our

ancestors saw millennia ago: the Great Bear relentlessly pacing
around the North Star, the arrogant queen Cassiopeia spinning
topsy-turvy on her celestial throne.
But our observant ancestors noticed that indeed, some stars

change slightly over time. They don’t stray noticeably from their
constellation patterns, but a few change in brightness.
One such star appears in the Greek image of Perseus, the warrior
who beheaded Medusa, the serpent-haired Gorgon who threatened
Cassiopeia’s kingdom.
The star is Algol, and it marks the “evil eye” of Medusa’s severed
head… Every three days (a little less), the star dims noticeably,
as if the eye were winking at us.
If we could see what’s actually happening, Algol would reveal

itself as two stars in orbit around one another. The slightly
dimmer of the two stars passes directly between us and the
brighter star, and when it does, we see Algol drop in brightness.
In actuality, Algol lies too far away to be seen as two separate

stars, even with our most powerful modern telescopes. Instead,
astronomers pieced together this story by studying the “light
curve” of the star.
If you can imagine graphing the brightness of the two stars

combined, as it changes over time, Algol’s graph would look a little
like this…
But of course, we only know the brightness of the star when we

measure it. For Algol, this means making repeated observations
over three days—and capturing the system when the two stars are
lined up and at their dimmest—in order to see what’s happening.
Astronomers understand these types of stars well enough to have

a pretty clear idea of what’s going on with Algol. And there are
many other stars that fit a similar pattern.
But some stars provide a challenge for astronomers to interpret…
Not far in the sky from Perseus, we have another Greek character:
Auriga, the Charioteer.
The fifth brightest star in the Charioteer is called Epsilon
Aurigae. Every 27 years, it drops in brightness and mysteriously
dims for a few years.
Let’s replace our classical view of the constellation with a connect-

the-dots look.
The lines will help as we leave our earthbound perspective and

imagine traveling to this fascinating destination. We can now see
that the “dots” of the stars are actually connected in three
dimensions… Epsilon Aurigae lies some 2,000 light years from
Earth, much farther than the other bright stars in the
constellation.
As we approach the star system, we see it as astronomers think it

might look—a bright supergiant star and a dark disk of dusty
debris orbiting one another. We can imagine flying around the
system to get a good look…
Studying the light from the star tells us it’s a supergiant. With a
diameter one hundred times that of our own Sun, Epsilon Aurigae
shines 10,000 times more brightly.
Some observations suggest that the supergiant star may have a

faint ring of material around it…
Or it may not.
And the disk provides many puzzles! Astronomers can estimate

the size of the disk based on previous observations, but other
details remain a mystery It almost certainly has a central region
cleared of debris. But how big is the hole in the doughnut?
And what lies inside the disk’s central region? All that debris may
orbit a single star… Or a pair of stars could zip around one
another at the center of the disk.
Indeed, there are many things we don’t know about the Espilon
Aurigae system.
How do we answer these questions? We need more observations.
From a distance, we cannot see the details of the Epsilon Aurigae

system. Instead, it reveals itself as only a single point of light in
the starry night sky.
By making repeated observations of the star while it undergoes an

eclipse, we can measure its brightness and other attributes,
tracking these carefully over time. The process will take years!
But the opportunity exists for everyone to take part. The Citizen
Sky Project invites amateur astronomers from around the globe to
contribute their observations to the steadily growing collection of
data that will help us piece together the story of Epsilon Aurigae.
The starry sky may appear changeless… But we know better.

And we want to know more.

Epsaur Script v10 14pt

Uploaded by

Copyright:

Available Formats

Epsaur Script v10 14pt

Uploaded by

Document Information

Original Title

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

Epsaur Script v10 14pt

Uploaded by

Copyright:

Available Formats

Citizen Sky

Planetarium Show / Trailer

The stars appear changeless.

On a clear, dark night, we see the same constellations our

But our observant ancestors noticed that indeed, some stars

If we could see what’s actually happening, Algol would reveal

In actuality, Algol lies too far away to be seen as two separate

If you can imagine graphing the brightness of the two stars

But of course, we only know the brightness of the star when we

Astronomers understand these types of stars well enough to have

But some stars provide a challenge for astronomers to interpret…

Let’s replace our classical view of the constellation with a connect-

The lines will help as we leave our earthbound perspective and

As we approach the star system, we see it as astronomers think it

Some observations suggest that the supergiant star may have a

And the disk provides many puzzles! Astronomers can estimate

How do we answer these questions? We need more observations.

From a distance, we cannot see the details of the Epsilon Aurigae

By making repeated observations of the star while it undergoes an

The starry sky may appear changeless… But we know better.

You might also like