APOD: Hyades for the Holidays (2012 Dec 24)

[APOD Robot]

Hyades for the Holidays

Explanation: Recognized since antiquity and depicted on the shield of Achilles according to Homer, stars of the Hyades cluster form the head of the constellation Taurus the Bull. Their general V-shape is anchored by Aldebaran, the eye of the Bull and by far the constellation's brightest star. Yellowish in appearance, red giant Aldebaran is not a Hyades cluster member, though. Modern astronomy puts the Hyades cluster 151 light-years away making it the nearest established open star cluster, while Aldebaran lies at less than half that distance, along the same line-of-sight. Along with colorful Hyades stars, this stellar holiday portrait locates Aldebaran just below center, as well as another open star cluster in Taurus, NGC 1647 at the left, some 2,000 light-years or more in the background. Just slide your cursor over the image to identify the stars. The central Hyades stars are spread out over about 15 light-years. Formed some 800 million years ago, the Hyades star cluster may share a common origin with M44 (Praesepe), a naked-eye open star cluster in Cancer, based on M44's motion through space and remarkably similar age.

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[/b]

[Ann]

Hyades for the holidays? Aldebaran for Christmas Eve?

It's a nice picture. The bright colors of the stars look very festive, and the triangular shape of the Hyades suggests a Christmas tree lying down!

However, as a diehard lover of blue stars, let me offer my own suggestion for a real Christmas star, surrounded by attendants. It's Tau Canis Majoris in cluster NGC 2362, picture by Jim Thommes. Personally I don't know of any other cluster where a superbright star sits in the middle of an almost round cluster, like a brilliant diamond, ruby of sapphire, surrounded by lesser stones.

Tau Canis Majoris is an incredible sapphire. Here you can read about this wonderful star.

Merry Christmas, everyone!

Ann

[owlice]

Ann, I'm sorry, but I'm confused... what do Tau Canis Majoris and NGC 2362 have to do with this APOD?

[bystander]

Personally, I like this image much more than the image Ann linked to.

[owlice]

I like this image, too; it really sparkles!

[Boomer12k]

I like Ann's Picture for the Big blue star. Maybe not for Christmas as it is only one color. I like the Christmas Tree Nebulas. Look them up with an image search, there are several. And SH 2-216, which I call the SANTA Nebula.

http://cs.astronomy.com/asy/m/nebulae/414612.aspx

And along with Taurus, et al, we have Jupiter zooming through the constellation, and the Moon soon to enter also.

Merry Christmas, or whatever, to you all. And to my good friend, ANN!!!!

:---[===] *

[orin stepanek]

I like today's APOD! The shape reminds me of an arrowhead!

[neufer]

Click to play embedded YouTube video.

<<Nao (pronounced now) is an autonomous, programmable humanoid robot developed by Aldebaran Robotics, a French startup company headquartered in Paris. The robot's development began with the launch of Project Nao in 2004. On 15 August 2007, Nao replaced Sony's robot dog Aibo as the robot used in the Robot Soccer World Cup (Robocup) Standard Platform League (SPL), an international robotics competition. The Nao Academics Edition is available for universities and laboratories for research and education purposes, and is projected for public distribution by 2011. In October 2010, the University of Tokyo purchased 30 Nao robots for their Nakamura Lab, with hopes of developing the robots into active lab assistants. In the summer of 2010, Nao made global headlines with a synchronized dance routine at the Shanghai Expo in China. In December 2011, Aldebaran Robotics released the Nao Next Gen, featuring enhanced software, a more powerful CPU and HD cameras.>>

[FLPhotoCatcher]

I think Ann's topic was more related to today's APOD than neufer's. Interesting info from both though.

[owlice]

I didn't understand why Ann wanted to discuss someone else's image of a completely different target on this thread. I was hoping for enlightenment. This thread should be about its topic -- today's APOD -- rather than someone else's topic. I remain confused.

Today's image is not only interesting, but very beautiful. A stellar portrait, indeed!

[Chris Peterson]

I didn't understand why Ann wanted to discuss someone else's image of a completely different target on this thread. I was hoping for enlightenment. This thread should be about its topic -- today's APOD -- rather than someone else's topic. I remain confused.

Today's image is not only interesting, but very beautiful. A stellar portrait, indeed!

I think Ann believes a star representative of Christmas should be blue.

Personally, I think blue is about the least "Christmasy" color there is!

[neufer]

<<The James Lick Telescope is an antique refracting 36 inch (91.44 cm) telescope built in 1889 that can still be viewed through today. Also called the "Great Lick Refractor" or simply "Lick Refractor", it is the third-largest refracting telescope in the world, surpassed by the Yerkes Observatory 40-inch and the 1 meter Swedish Solar Telescope. It is located at the University of California's Lick Observatory atop Mount Hamilton at an altitude of 4,209 feet (1,283 m) above sea-level. The telescope is housed inside a dome which is powered by hydraulics to raise and lower the floor, rotate the dome, and drive the clock mechanism to track the earth's rotation. The original hydraulic system still operates today, with the exception that the original wind-powered pumps to fill the reservoirs have been replaced with electric pumps. James Lick is himself entombed below the telescope's observing room's floor.

A hacksaw was sent for

<<The telescope was the largest refractor until the 1897 construction of the Yerkes telescope, and the second largest up until 2002. The fabrication of the objective lens, a two element achromat, the largest lens ever made at the time, caused years of delay. The famous large telescope maker Alvan Clark was in charge of the optical design. He gave the contract for casting the high quality optical glass blanks, of a size never before attempted, to the firm of Charles Feil in Paris. One of the huge glass disks broke during shipping, and making a replacement was delayed. Finally, after 18 failed attempts, the lens was finished, transported safely across country, and on 1888-12-31 was carefully installed in the telescope tube.

The builders had to wait for 3 days for a break in the clouds to test it. On the evening of Jan. 3 the telescope saw 'first light' - and they found that the instrument couldn't be focused. An error in the estimate of the lens' focal length caused the tube to be built too long. A hacksaw was sent for, the great tube was unceremoniously cut back to the proper length, and the star Aldebaran came into focus.>>

[neufer]

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http://apod.nasa.gov/apod/ap110103.html
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<<The Winter Hexagon or Winter Circle/Oval is an asterism appearing to be in the form of a hexagon with vertices at Rigel, Aldebaran, Capella, Pollux, Procyon, and Sirius. It is mostly upon the Northern Hemisphere's celestial sphere. On most locations on Earth (except the South Island of New Zealand and the south of Chile and Argentina and further south) this asterism is prominently in the sky from approximately December to March. In the tropics and southern hemisphere this (then called "summer hexagon") can be extended with the bright star Canopus in the south.

Smaller and more regularly shaped is the Winter Triangle (also known as the Great Southern Triangle), an approximately equilateral triangle that shares two vertices (Sirius and Procyon) with the larger asterism. The third vertex is Betelgeuse, which lies near the center of the hexagon. These three stars are three of the ten brightest objects, as viewed from Earth, outside the Solar System. Betelgeuse is also particularly easy to locate, being a shoulder of Orion, which assists stargazers in finding the triangle. Once the triangle is located, the larger hexagon may then be found. Several of the stars in the hexagon may also be found independently of one another by following various lines traced through various stars in Orion. The stars in the hexagon are parts of six constellations. Counter-clockwise around the hexagon, starting with Rigel, these are Orion, Taurus, Auriga, Gemini, Canis Minor, and Canis Major.>>

--------------------------------------------------------------
. Don Quixote Part 2 CHAPTER XLI
.
"I don't understand that way of looking at things," said Sancho;
"I only know that your ladyship will do well to bear in mind that
as we were flying by enchantment so I might have seen the whole
earth and all the men by enchantment whatever way I looked; and
if you won't believe this, no more will you believe that,
uncovering myself nearly to the eyebrows, I saw myself so close
to the sky that there was not a palm & a half between me & it.
And it so happened we came by where the seven goats are . . ."
.
. Don Quixote replied,
.

Click to play embedded YouTube video.

"we could not have reached that heaven where the seven goats
Sancho speaks of are without being burned; and as we were
not burned, either Sancho is lying or Sancho is DREAMing."
.
. "I am neither lying nor DREAMing," said Sancho;
. "only ask me the tokens of those same goats, and
you'll see by that whether I'm telling the TRUTH or not."
.
. "Tell us them then, Sancho," said the duchess.
.
. "Two of them are green, [Procyon & Capella]
. "two blood-red," [Aldebaran & BetelGuese]
. "two blue, and" [Sirius & Rigel]
"one a mixture of all colours." [Castor/Pollux]
.
"An odd sort of goat, that," said the duke; "in this earthly region
of ours we have no such colours; I mean goats of such colours."[/i]
----------------------------------------------------------

[neufer]

[b][color=#0000FF]Jupiter and the waxing gibbous moon will pair up closely on Christmas night Dec. 25. Taurus’ brightest star Aldebaran will also be nearby. This map shows the sky facing east around 6:30 p.m. CST. Created with Stellarium[/color][/b]

---

Heavenly gift awaits skywatchers Christmas night
Astrobob, December 23, 2012

<<Don’t nod off too early after your Christmas feast or you’ll miss the astronomical dessert. Jupiter and the moon will be stacked like strawberries on shortcake all night long.

You may remember their conjunction last month, but this time around the duo will make an even more compact pair. They’ll be just a half degree or one moon diameter apart when closest around 5:30 p.m. (CST). Throw on a coat, walk outside and face east during evening twilight or later to get a good look.

The two will rise together side by side in the northeast around 2:30 p.m. that afternoon only 1 degree – two full moons – apart. Just before sunset, the moon will be high enough in the sky to sight Jupiter through binoculars to its upper left. Three hours later, the moon lines up under Jupiter in conjunction and then slowly slides away from the planet overnight.>>

[bystander]

I think Ann believes a star representative of Christmas should be blue.

Personally, I think blue is about the least "Christmasy" color there is!

There are plenty of very blue stars in todays image,

[Ann]

I didn't understand why Ann wanted to discuss someone else's image of a completely different target on this thread. I was hoping for enlightenment. This thread should be about its topic -- today's APOD -- rather than someone else's topic. I remain confused.

Today's image is not only interesting, but very beautiful. A stellar portrait, indeed!

I think Ann believes a star representative of Christmas should be blue.

You got me, Chris!

Personally, I think blue is about the least "Christmasy" color there is!

Most people would agree, I'm sure.

Today's APOD is boldly colored, which gives the image a wonderfully festive quality that is just so appropriate for the season. I love it!

In reality, most of the stars in the image apart from Aldebaran are rather pale in color. The blue stars in it are bluer than the Sun but yellower than Sirius and Vega. The fact that the Hyades is about 800 million years old means that all the O- and B-class stars that once belonged to this cluster have burnt out and disappeared long ago. And O- and B-class stars are the ones that are usually thought of as blue.

There are in fact two intrinsically blue class B stars in today's APOD, however. Neither of them is a member of the Hyades, because they are simply too hot and blue and therefore too young for that. One is a small blue star about midway between the brightish blue star in the upper left corner and the orange star designated ε, or Epsilon Tauri. That small blue star is a modest star of spectral class B9, HU Tau or HD 29365. This star is blue not only because it belongs to spectral class B (if just barely), but also because it has a (small) negative color index, -0.019 ± 0.007. This makes it bluer than Sirius and Vega.

The other blue star is the brightish star in the upper left corner. It's a star of spectral class B3, so it's both brighter and bluer than its small B9 "cousin". The B-V index of the brighter star is -0.112 ± 0.003. I love the designation of this star: it's called Tau Tau!

As for Tau Canis Majoris, however, it is so much brighter and bluer than either HU Tau or Tau Tau. While Tau Tau is about as bright as 250 stars like the Sun, Tau Canis Majoris may shine 13,000 times as bright in visual light as the Sun, and then it pumps out incredible amounts of invisible ultraviolet light, too.

But as I said about today's APOD, it makes the Hyades look festive indeed. The cluster does resemble a Christmas tree decorated with colorful baubles and a brilliant orange "top star" that for some reason has fallen from the top!

Ann

[Ann]

. Don Quixote Part 2 CHAPTER XLI
.
"I don't understand that way of looking at things," said Sancho;
"I only know that your ladyship will do well to bear in mind that
as we were flying by enchantment so I might have seen the whole
earth and all the men by enchantment whatever way I looked; and
if you won't believe this, no more will you believe that,
uncovering myself nearly to the eyebrows, I saw myself so close
to the sky that there was not a palm & a half between me & it.
And it so happened we came by where the seven goats are . . ."
.
. Don Quixote replied,
.

Click to play embedded YouTube video.

"we could not have reached that heaven where the seven goats
Sancho speaks of are without being burned; and as we were
not burned, either Sancho is lying or Sancho is DREAMing."
.
. "I am neither lying nor DREAMing," said Sancho;
. "only ask me the tokens of those same goats, and
you'll see by that whether I'm telling the TRUTH or not."
.
. "Tell us them then, Sancho," said the duchess.
.
. "Two of them are green, [Procyon & Capella]
. "two blood-red," [Aldebaran & BetelGuese]
. "two blue, and" [Sirius & Rigel]
"one a mixture of all colours." [Castor/Pollux]
.
"An odd sort of goat, that," said the duke; "in this earthly region
of ours we have no such colours; I mean goats of such colours."[/i]
----------------------------------------------------------

Art, I'm amazed! That's a wonderful description of the colors of the major stars of the winter hexagon by Miguel de Cervantes! Admittedly Procyon and Capella aren't technically green, of course, but both have light curves that peak in or close to the green part of the spectrum. I had no idea that Cervantes had such an eye for the color of stars!

Photo: Jim Kaler

And as for the talk of goats: remember that Capella is known as the goat star, and epsilon, eta and zeta are her kids! In this picture, Capella is at bottom left, epsilon is at top center, zeta is at top right and eta is below zeta.



Ann

[Ann]

Boomer12K wrote:
Merry Christmas, or whatever, to you all. And to my good friend, ANN!!!!

Thanks, Boomer12K! A very Merry Christmas to you, my friend, and to everyone else here, too!

Ann

[rstevenson]

[b][color=#0000FF]Jupiter and the waxing gibbous moon will pair up closely on Christmas night Dec. 25. Taurus’ brightest star Aldebaran will also be nearby. This map shows the sky facing east around 6:30 p.m. CST. Created with Stellarium[/color][/b]

---

Heavenly gift awaits skywatchers Christmas night
Astrobob, December 23, 2012 ... >>

Okay, I'm confused. I had a look tonight, with a rare clear sky to help. Jupiter was not at all in that position. It was to the left of the Moon by almost two full Moon widths. So was the caption under the picture wrong? Did they mean Christmas Eve perhaps?

Rob

[neufer]

I had a look tonight, with a rare clear sky to help. Jupiter was not at all in that position. It was to the left of the Moon by almost two full Moon widths. So was the caption under the picture wrong? Did they mean Christmas Eve perhaps?

No. Two full Moon widths sounds about right. Sorry you were disappointed.

[Chris Peterson]

Okay, I'm confused. I had a look tonight, with a rare clear sky to help. Jupiter was not at all in that position. It was to the left of the Moon by almost two full Moon widths. So was the caption under the picture wrong? Did they mean Christmas Eve perhaps?

IMG_6524p.jpg

When did you look? At your location, shortly after moonrise, Jupiter was above and to the left of the Moon (in the east). Over the next few hours, it shifted to the right. For observers at middle and high northern latitudes, the closest the two bodies got was about a degree- two lunar widths. This is what I saw at about 5pm local (26 Dec 00:00 UT), still twilight here.

[rstevenson]

Hi Chris,

I was visiting friends for Christmas dinner last night. One of them was showing me a wide angle lens on his Canon and I took a quick snap of the Moon and Jupiter, more to see what the exposure would be like than anything else. Here's a crop from that image. The EXIF data on the original says it was taken at a few seconds before 6:05 PM, AST.

Moon.jpg

When I got home about 10:30 PM the Moon was almost directly below Jupiter, both being near the zenith.

Rob

[Anthony Barreiro]

Okay, I'm confused. I had a look tonight, with a rare clear sky to help. Jupiter was not at all in that position. It was to the left of the Moon by almost two full Moon widths. So was the caption under the picture wrong? Did they mean Christmas Eve perhaps?

IMG_6524p.jpg

When did you look? At your location, shortly after moonrise, Jupiter was above and to the left of the Moon (in the east). Over the next few hours, it shifted to the right. For observers at middle and high northern latitudes, the closest the two bodies got was about a degree- two lunar widths. This is what I saw at about 5pm local (26 Dec 00:00 UT), still twilight here.

Thanks for the lovely picture, Chris.

Because the Moon was just south of the ecliptic, the farther north you are on Earth the greater the observed angle between Jupiter and the Moon. In parts of Africa and South America, the Moon occulted Jupiter! The link goes to a picture and video taken by Paulo Cacella in Brasilia.

[Ann]

Thanks for the great Moon and Jupiter picture, Chris, showing the Lady in the Moon in all her plump splendor! The Lunar Lady makes me think of Rubens, the 17th century artist who loved to paint "full-bodied" women. The painting on the left is called "Rubens and his wife" by Fernando Botero.


Anthony, thanks for explaining why the Moon occulted Jupiter as seen from certain parts of the world, while the two "heavenly bodies" were quite widely separated as seen from other locations. That explains why Rob and I were disappointed!

Thanks for the link to the Moon occulting Jupiter! It's a great picture, but I was surprised to see that the surface brightness of the Moon appears to be higher than the surface brightness of Jupiter. Given the fact that the Moon is very dark, about as dark as asphalt, I would have expected the surface brightness of Jupiter to be higher. Does anyone know an explanation for this?

Ann

[Anthony Barreiro]

[...]

Thanks for the link to the Moon occulting Jupiter! It's a great picture, but I was surprised to see that the surface brightness of the Moon appears to be higher than the surface brightness of Jupiter. Given the fact that the Moon is very dark, about as dark as asphalt, I would have expected the surface brightness of Jupiter to be higher. Does anyone know an explanation for this?

Ann

This is just a guess -- the Moon is closer to the Sun and closer to the Earth, so she gets more light from the Sun than Jupiter does, and more of the Moon's light gets to Earth than light from Jupiter. If somebody more mathematically competent than I am would calculate the surface areas of the the relevant spheres I would be tickled pink.