Why does the faint star Thuban, in Draco, have a name?
Very few stars as faint as Thuban are named. So, why is this faint star in the constellation Draco, the Dragon, named? The reason might surprise you. Thuban means, "Whole of Draco" as well as, "Life of Heaven." These very ancient meanings don't give us much of a clue as to why this star has a name, unless you know the most important fact—Thuban was THE North Star 4,700 years ago. Back then, Thuban was located exactly where Polaris is located today. Thuban is no longer the North Star because the Earth wobbles on its axis which is now pointing toward Polaris. In about 20,000 years, the Earth's axis will again point toward Thuban. So, the inconspicuous star Thuban was used as the North Star from about 3700 BC to 1900 BC. It was closest to the North Celestial Pole, that is, the spot in the sky that the Earth's axis points to, at 2787 BC. Around 1900 BC, Kochab, in the bowl of the Little Dipper, took over as the North Star until Polaris became closer to the North Celestial Pole. Thuban is approximately in the middle of Draco, so this was the reason that its name has the meaning, "Whole of Draco," because all of Draco circled around Thuban when it was the pole star. LOCATING THUBAN: As long as the sky is reasonably dark, Thuban is easy to find. The other two stars of the Big Dipper's bowl point to Thuban—see chart below.
Facts about Thuban
Magnitude: 3.65; Some historical evidence suggests that Thuban may have been brighter in the past, maybe shining at magnitude 2.
Distance: 310 light years or 1,823 trillion miles, that is, 1,823,000,000,000,000 miles.
Mass: Thuban has 3.4 times more matter than our Sun.
Diameter: 265 times the diameter of our Sun, so it is considered a white giant star.
|
Facts about Polaris
In the sky, Polaris shines at about magnitude 2. It is about 400 light years away and has a diameter 30 times greater than our Sun. It is considered a giant star and has a mass of about 4 times that of our Sun.
|
Brightness Comparison
If the Sun, Polaris and Thuban were placed side by side, Polaris would be about 200 times brighter than the other two but Thuban would be a little brighter than our Sun. |
Questions about the Sky or Astronomy? • • • Need Telescope Advice?
If you have a question about astronomy or
would like advice on buying a telescope or accessories,
please email me at ASTROINFO.
No charge, no obligation, no hassles.
|
AUGUST SKY
New Moon: Friday, August 1 — First Quarter: Friday, August 8
Full Moon: Saturday, August 16 — Last Quarter: Saturday, August 23
New Moon: Saturday, August 30
Location of Planets when it FIRST GETS DARK:
Jupiter is lower in the southern sky in Sagittarius. It will be the brightest "star" in the whole sky.
Practically speaking, Venus, Mars and Saturn are not visible because they are close to the Sun.
Constellations visible when it FIRST GETS DARK:
Rising in the east: Pegasus
At the southern horizon: Sagittarius
At the top of the sky: Lyra (east) & Hercules (west)
Setting in the west : Virgo
Clock position of the bowl of the Big Dipper when it first gets dark is 8:30 o'clock.
Meteor Shower: The delta AQUARIDS peak around July 29. During this shower, 20 meteors per hour can be seen. The Perseids peaks August 12 and fall at the rate of 1 a minute.
Want a really nice star chart of the night sky
that also details celestial events?
Visit SkyMaps. |
Great Astronomy Sites to Visit
Astronomy magazine
Sky & Telescope magazine
SkyNews in Canada
Space.com
NASA
Astronomy Picture of the Day
Lunar Picture of the Day
Satellite Tracking
Rainbows & other neat things in the sky
Daily Sunspot Count & other Space Weather (comets plus)
Spacecraft Mission Sites
Images from the Hubble Space Telescope that orbits Earth
Rovers on Mars • Spirit and Opportunity
Phoenix Mars Mission to analyze soil for life
Cassini spacecraft orbiting Saturn
Messenger spacecraft going to Mercury
New Horizons spacecraft going to Pluto
Questions? • • • Need Telescope Advice?
If you have a question about astronomy or
would like advice on buying a telescope or accessories,
please email me at ASTROINFO.
No charge, no obligation, no hassles.
|
SEPTEMBER SKY
First Quarter: Sunday, September 7— Full Moon: Monday, September 15
Last Quarter: Monday, September 22 — New Moon: Monday, September 29
Location of Planets when it FIRST GETS DARK:
Jupiter is lower in the southern sky in Sagittarius. It will be the brightest "star" in the whole sky.
Practically speaking, Venus, Mars and Saturn are not visible because they are close to the Sun.
Constellations visible when it FIRST GETS DARK:
Rising in the east: Pisces
At the southern horizon: Sagittarius
At the top of the sky: Lyra
Setting in the west : Bootes
Clock position of the bowl of the Big Dipper when it first gets dark is 8:00 o'clock.
Meteor Shower: Next up are the Orionids which peak around October 21. During this shower, 20 meteors per hour can be seen.
|
Astronomy Books & Star Charts
Ken Press publishes a series of popular
star charts and
beginning astronomy books
for adults and children. Click here for product info.
Click here for a
PDF brochure.
Contact Ken Press at (520) 743-3200 or email.
|
Finally, Science Fiction that has real science!
“Time-driven as it is, Moonquake is a fast-paced story
that is never boring. The author is very effective at mixing technological issues with human narratives. Fans of hard science fiction will eat this up like addictive candy.”
—Ben Nault, President, Tucson L5 Space Society, Moon Society, Tucson Outpost
Moonquake
by Dr. Alan Binder
328 pages. $7.99. Ken Press. Paperback.
Read Chapter Excerpt
Orders: (520) 743-3200.
Signed copies available.
ORDER TODAY
A SCIENCE-FICTION novel by Dr. Alan B. Binder who was the catalyst and brains behind the Lunar Prospector space mission to the Moon. He is the noted discoverer of water at the lunar poles. In this, his first science fiction novel, NASA has blown it again with another shuttle disaster. They are put on a short leash to establish the first lunar base. But, it is difficult for a moving behemoth to change direction. As might be expected, the moonbase does not meet the approval of everyone involved. Normally this might be okay but space is fraught with many unknowns and dangers so it is better to err on the side of robustness than “adequate.” Things get shaken up a bit and there is a race to avoid death.
|
Children's Star Chart
This is the chart that appears in the May 2007 issue of
Family Fun Magazine.
The David H. Levy Guide to the Stars Children's Star chart is an inexpensive way to introduce youngsters to the night sky. This quality star chart is printed in color and made of durable coated card stock paper. The back is loaded with information including Moon facts, Meteor Showers, Space History, Binocular Objects and additional instructions. Price is $4 each (shipping is $4 for 1, 2 or 3 and $7 for 4 or more). To order, Click Here for instructions.
Click on image below to enlarge.
Bargain Hunters
Ken Press has a limited number of slightly damaged books and star charts for sale.
To order, call (520) 743-3200. Prices are as follows:
What's Out Tonight (1). Retail $39.95/Two pages torn out. $12 shipped
The Next Step (2). Retail $29.95/Like New, $15 shipped
The Next Step (1). Retail $29.95/Spine slanted, $10 shipped
Touring the Universe (5) . Retail $27.95/ Look used, $14 shipped
Student's Guide to the Stars (2). Retail $4/Damaged $1
Check out our new Atlas of the Heavens. Available Fall 2008.
|
