Download Auriga

Auriga: The Charioteer
In Case You’ve Never Seen It
Before..
An Old Constellation
•Gigir “The Chariot” - the name given it in ancient Sumeria
between 3500 & 2500BC.
•Heniochos “The Charioteer” -its classic Greek name.
•Auriga “The Charioteer” -its latin name from the Romans.
Who’s the Charioteer? Take your pick!
Hephaetus
Erichthonius
Myrtilus
Poseidon
…And What’s Up with the Goat?
•Capella, the brightest star, is old
Roman for “The She-Goat.”
•The Romans recognized Epsilon, Zeta
& Eta Aur as “The Kids”
•The Greeks only saw two Kids, Zeta &
Eta
•No mythological basis. Perhaps Mom
& the kids are best treated as own
asterism.
Constellation Facts
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•
•
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Abbreviation: Aur
Coords: RA 6 h Decl: +40°
Area: 657 sq. deg. (21st/88)
Brightest star: Capella (α
Aur) (0.8mag )
• Nearest star: QY Aur (20.0 ly)
Messier objects: 3
• Meteor showers:
Alpha Aurigids (Aug 25th- Sep 6th))
Delta Aurigids (Sept-22 to Oct 23)
• Bordered by
Camelopardalis
Perseus
Taurus
Gemini
Lynx
Where’s it at?
Finding It: Winter Hexagon
From Cheryl Haimann’s
Backyard Astronomy
www.pikerpress.com
(Used with permission)
Finding It From Orion
From Cheryl Haimann’s
Backyard Astronomy
www.pikerpress.com
(Used with permission)
Finding it (cont’d)
Use top 2 stars in Big Dipper’s bowl and head west 70
degrees. You’ll run into Capella
The Pentagon, or “Five Chariots”
•Capella (mag 0.8) “She-Goat”,
6th brightest star in the sky
•Mankalinan (mag 1.9)
“Shoulder of the Reinholder”
•Bogardus (2.62)
•AlKab( Hassaleh)(2.69)
•ElNath (1.6) “Butting One”,
technically Beta Tauri
Capella- The “She-Goat” is Twins
•Capella a & b are both G-class giants, of around 3 solar masses
each. They probably started life on the main sequence as A-class
dwarfs, but are early into their red giant phase.
•The two suns circle each other at a distance closer than our
earth-sun distance (0.73 AU). Their combined luminosity is 150
times our sun.
•Capella is circumpolar at our latitude.
The AntiCenter of our Galaxy is in
Auriga
Those Wonderful Open Clusters
M36,M37,M38
M38
M37
M36
AE Aurigae & the Flaming Star Nebula
AE Aur is a “runaway” star ejected from the star-forming region in Orion some
2.7 million years ago. It’s big, young, and bright, and illuminates its current area
of space, producing the Flaming Star Nebula (IC 405).
Variables in Auriga
•Zeta Aurigae is an eclipsing binary.
Every 2.6 years, it dims ½ magnitude for
40 days.
•Beta Aurigae (Menkalinan) is an EB too,
dimming 0.1 magnitude for 10 hours
every 4 days.
•AE Auriga (remember the flame star?)
varies between mag 5.8 & 6.1 , being
young & wild (INA).
Epsilon Aurigae:“This Strange Star”
• A Class F Supergiant
• First noted to vary in brightness in 1821.
• Observations in 1847-48, 1874-75,1901-2
showed it dimming for periods of 2 years!
• Hans Ludendorff proposed in 1904 that
Epsilon Aurigae is an Eclipsing Binary with
a period of 27.1 years.
• Last eclipse was 1982-84. Next predicted
eclipse is 2009-11.
• How can an eclipse take two years?
How Eclipsing Binaries Work
• One companion star gets in
our line of sight of the
other, blocking some part
the light we see.
• For this to work for Epsilon
Auriga, the occluding star
would have to be HUGE3000 AU!
• If it’s not a star, how about a
disk of matter?
The Eclipsing Disk Model
• A disk of matter around the star that’s not
in our line of site all of the time, but
periodically gets in the way and dims the
light we receive.
• There’s still a problem with this model if
we look at the light curves from past
eclipses…
It gets brighter in the middle of the
eclipse. We need a hole- a donut?
The Current “Orbiting Donut” Model
•Two B- class stars orbit each other,
and are surrounded by a big circumstellar disk.
•This young, messy system in turn
shares an orbit with our F0
suoergiant primary.
•In our line of sight, light can pass
through the “transparent” B stars in
the middle of the eclipse.
Watch for it !
•First Contact August 6 2009 (est)
•Midoint Aug 10 2010 (est)
•Done May 15 2011 (647 Days total)
0.1
2.8-?
3.2
3.8
2.7
Resources
• American Association of Variable Star
Observers: http://www.aavso.org
• Epsilon Aurigae Campaign Page:
http://www.hposoft.com/Astro/PEP/EpsilonAurigae.html
• IYA 2009 Epsilon Aurigae Project:
http://astronomy2009.us/citizen_science/epsilon-aurigae/
• Feb 2009 Sky & Telescope Celestial Calendar Column
That’s It!!!