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Free Lecture 03: Universe Scale, and Light II

The lecture video is embedded below but also available here in MP4 format.
Additionally, slides used in the lecture are embedded below but also are available here in Powerpoint format.
Questions after the lecture? Please ask them in here.

Wikipedia entries:
Black body
Spectrum
Spectral line
Bohr model
Doppler Effect

Additional Apod photos disccussed

Imagine if we lived in a binary solar system or a triple star or even an open cluster with 10-100 stars or  why not a globular cluster with 100000-1000000 stars….. But don’t we see that we live with one bright star, which is kind a bit unusual, but it rather appears that it is the greatest benefit to humanity, allowing us to have a Night.

The Bohr atom

The Doppler shift high and low

Sheldon Doppler

How to find the Winter Hexagon

Introduction

Orion is the key for
cracking the winter sky

The winter sky is an excellent place to begin exploring the constellations that make up the night sky. Orion is the key, or signpost, for locating many of the other constellations in the winter sky. There are two convenient ways to locate all of the main constellations around Orion once Orion is located. Fortunately, Orion is easy to locate and well known to most people.

The first way is to follow lines made by pairs of stars in Orion. The second way is to locate the great winter hexagon of bright star around Orion.

The Constellations of the Winter Sky

If you live in the northern latitudes and you scan the sky from the southern horizon to the region overhead, you should be able to see the following constellations on a clear winter night: Orion the Hunter, Canis Major the Great Dog, Canis Minor the Little Dog, Taurus the Bull, Auriga the Charioteer, Gemini the Twins and the Pleiades star cluster. (See the map on the next page).

 In Greek mythology, Orion was a great hunter who eventually offended the gods, especially Apollo. Apollo tricked Artemis, the Goddess of the hunt, into shooting Orion on a bet. When she discovered that she had shot Orion, she quickly lifted him to the heavens and made him immortal, where he now hunts eternally with his two dogs, Canis Major and Canis Minor. In front of him is his prey Taurus the Bull.

 The myths surrounding Auriga the Charioteer vary, but it is an ancient constellation dating back to at least to the Ancient Greeks. Some say Auriga invented the chariot and others that he trained horses for the best chariots.

 Gemini is a constellation made up of two stick figures known as the twins, Castor, who was a great horseman, and Pollux, who was a great boxer. According to one myth, Castor and Pollux (a.k.a. Polydeuces) were the sons of Zeus and Leda (from Leda and the Swan) and were hatched from an egg. Their sister was the beautiful Helen whose face launched a thousand ships to do battle in front the Trojan city of Troy.

Method 1: Using Pairs of Stars in Orion as a Guide

Finding Sirius and Canis Major

If you follow a line from the belt stars of Orion to the left and slightly down, you will come across a very bright star called Sirius, which is also known as the Dog Star. (See the arrows in the diagram to the right).

Sirius is the brightest star in the night sky so it is hard to miss. Once you’ve located Sirius you can locate the other stars in the constellation Canis Major the Great Dog.

Finding Procyon and Canis Minor

Follow the a line from the shoulder stars of Orion to the left. The first bright star that you will come close to is Procyon, which resides in Canis Minor.

From there you should be able to see the other star that us easily visible. Together, the two stars make up the constellation Canis Minor, which is also known as the Little Dog. Along with Canis Major, Canis Minor follows Orion across the heavens on an eternal hunt.

Finding Aldebaran and Taurus

Following the belt stars to the right, you will pass just below the bright star Aldebaran and through the constellation Taurus, which is also known as the Bull.

Continuing on you will run across a fuzzy blur of stars closely grouped. These are the Pleiades, or the Seven Sisters.

Finding Capella and Auriga

Follow the bottom most star on the left and the left most belt star upwards (going roughly over your head) and you will come across a very bright star called Capella. From Capella, you can follow the pentagon of brighter stars nearby that make up Auriga. Just below Capella, there is a triangle of stars known as ‘the kids’ as in goat babies.

Capella was one of the most important stars for navigation as it could be seen throughout most of the year from mid northern latitudes.

Finding the Twins Castor and Pollux

Follow a line from Rigel to Betelgeuse heading upwards and overhead. You will come to two rough sticks of stars that are headed by two brighter stars. This is the constellation Gemini, composed of the twins Pollux and Castor. Pollux is on the left and Castor is on the right.

Method 1: Using the Winter Hexagon Centered About Orion

If you look in around the sky centered on Orion, you should be able to see a rough hexagon of very bright stars. This is called the Winter Hexagon. Starting at Rigel, if you go counterclockwise by one, you end up at Aldebaran in Taurus. Go counterclockwise once more and you end up at Capella in Auriga. Go counterclockwise once more and you end up at the pair of stars Pollux and Castor in Gemini. Go counterclockwise once more and you end up at Procyon in Canis Minor. Finally, if you go counterclockwise once more you end up at Sirius in Canis Major.

Credits: http://www.science-teachers.com

The winter hexagon v/s the summer hexagon?

Credits : Winter hexagon - Felgari

The winter hexagon is not a constellation but simply an asterism. But when there’s winter in the Northern Hemisphere, its summer in the Southern Hemisphere. I find it really unfair for the world to call this set of stars as the winter hexagon. Why don’t call it the summer hexagon? Frankly speaking I feel like being discriminated on belonging from the Southern Hemisphere.

Winter Hexagon from the Tropics

I understand that development in the astronomy field knew its leap in the Northern Hemisphere, but still I am hereby campaigning for a change in the name of this asterism ( I know Asterisms are not even officially recognized names). But the “winter hexagon” It is a complete misnomer. When I first got to see this beautiful set of constellations in its entirety by the seaside, I was feeling hot. One as it was a breezeless night, hot and damp. Secondly for the utter pleasure of being able to identify the hexagon which covered almost ¼ the portion of the sky and being able to identify six constellations in one go.  It was awesome.

But Do you Know How to find the winter hexagon?

One could ask it’s already April and the spring is already here, so why talk about the winter hexagon? It’s just because the winter hexagon in a few months would not remain in our skies. During January at dusk I would have to raise up my head towards the zenith to see the Orion as it would highlight our north western skies, but now in April it’s already halfway between the horizon and the zenith towards the west at dusk. And to tell you Scorpion is already on its way. (Hope you know about the Scorpion – Orion saga) So to say in a few months Orion would be no more on the skies. (I would miss Orion a lot)

And as April is here, it would be a lovely time to appreciate the nature in its bloom and a have good time to observe the night sky. No more shivering and complaining about the chilly weather to have a look at the sky (for my friends of the Northern Hemisphere). As for us Mauritians, we have only two seasons per se. Our hot humid summer is already gone and we are slowly entering the winter phase.

So, if you feel being discriminated by pronouncing the Winter Hexagon, (or any other misnamed constellation or asterism) then campaign with me for this misnomer. Together, united we can change the name of this marvelous hexagon to a common name. Because as the saying goes “the sky has no borders, it is for everyone”. (Is it really a saying or I just made it up?). I suppose I got it from The Astronomers without borders. They have their motto as One people, One Sky.

Related Articles:

How to find the winter hexagon

My Top 20 Guideposts in the Sky

Number

Common
Name

Constellation

Apparent
Magnitude

Spectral
Type

Luminosity
(Sun = 1)

Distance
(Light Years)

Radial
Velocity
(km / sec)

1 Sirius Canis Major -1.46 A1 26 8.7 -8
2 Canopus Carina -0.72 F0 15,000 310 +21
3 Alpha
Centauri
Centaurus -0.04 G2 1.7 4.3 -22
4 Arcturus Boötis 0.00 K2 115 36 -5
5 Vega Lyra 0.03 A0 52 25 -14
6 Capella Auriga 0.08 G8 F0 90 70 43 +30
7 Rigel Orion 0.12 B8 60,000 910 +21
8 Procyon Canis Minor 0.38 F5 7 11.4 -3
9 Achernar Eridanus 0.46 B5 400 85 +19
10 Betelgeux Orion 0.0 – 0.9 M2 105,000 v 640 +21
11 Agena Centaurus 0.61 B1 10,000 460 -11
12 Altair Aquila 0.77 A7 10 16.6 -26
13 Acrux Crux Australis 0.83 B1 3,200 360 -11
14 Aldebaran Taurus 0.85 K5 120 68 +54
15 Antares Scorpius 0.96 M1 7,500 330 -3
16 Spica Virgo 0.98 B1 2,100 260 +1
17 Pollux Gemini 1.14 K0 60 36 +3
18 Fomalhaut Piscis Australis 1.16 A3 13 22 +7
19 Deneb Cygnus 1.25 A2 70,000 1,800 -5
20 Becrux Crux Australis 1.25 B0 8,200 425 +20

Explanation

Number

This is a list of the 20 brightest stars as seen from the Earth (not including the Sun). The stars are numbered from 1 to 20 in sequence.

Common Name

This is the name by which the star is commonly known. The names are Greek, Latin or Arabic. This web site is based in London: stars not visible from London are in red.

Some examples of the names: Deneb is Latin for tail (because it marks the tail of The Swan – Cygnus); Antares is Greek for rival of Mars (because of its red colour); Aldebaran is Arabic for eye of the bull (because it marks the eye of The Bull – Taurus).

Constellation

A constellation is a star group (as seen from Earth) that the star is a part of. Constellations are human inventions. The stars in them appear in the same part of the sky but are, in fact, at different distances from us and not related to each other. Different cultures use different constellations. For more, read Astronomy and Astrology.

In the West, there are 88 recognised constellations; 48 of these date from Roman times and are known as the Classical Constellations. These include the 12 Zodiac constellations through which the Sun, Moon and planets always pass through. Constellations are always known by their Latin names.

Some examples: Canis Major means The Great Dog; Orion is The Hunter; Crux Australis means The Southern Cross.

Constellations are used by astronomers for convenience. We say that Sirius is in Canis Major rather than give its celestial coordinates.

Apparent Magnitude

Apparent Magnitude tells how bright the star is as seen from the Earth. The magnitude scale was devised by the Ancient Greeks. The brightest stars were called First Magnitude, the next brightest were called Second Magnitude, etc.

In modern times, the scale has been defined mathematically. A star of magnitude 1 is about 2.5 times brighter than a star of magnitude 2 which in turn is 2.5 times brighter than a star of magnitude 3. The brighter a star, the smaller its magnitude. Many stars are brighter than first magnitude. Some stars are so bright they have negative magnitudes. On this scale, Jupiter has a magnitude (at its brightest) of -2.6, Venus is at -4.4 and the Sun -27. The faintest stars visible to the naked eye are sixth magnitude. Pluto has a magnitude of +14, far too faint to be visible without a powerful telescope.

In the table it can be seen that Betelgeux varies its magnitude – some stars are variable in brightness.

The brightness of a star as seen from Earth depends on its intrinsic luminosity and its distance from Earth. A dim star may appear bright because it is close while a luminous star may appear faint because it is far away. This is why we say Apparent Magnitude.

Spectral Type

When starlight is passed through a prism, it splits into its constituent colours, like a rainbow. This is called the star’s Spectrum. Stellar spectra are crossed by dark lines. These lines give astronomers a lot of information about the star: temperature, luminosity, radius, magnetic properties, movement. Read The Electromagnetic Spectrum for more on spectra.

The Morgan-Keenan spectral classification

The Morgan-Keenan spectral classification (Photo credit: Wikipedia)

Stellar spectra are classified into types. These types are given letters. The spectral type series is a temperature series. Moving from the hottest stars to the coolest, the series of letters runs O, B, A, F, G, K, M.

Each spectral type is subdivided into ten numbers. For example, A0, A1, A2, up to A9. A0 is hotter than A1. The table below gives more information.

Spectral
Type

Colour

Surface
Temperature
(°C)

O

Blue >30,000

B

Blue-White 20,000

A

White 10,000

F

Yellow-White 7,000

G

Yellow 6,000

K

Orange 4,500

M

Red 3,000

Our Sun is a star of Spectral Type G2 with a surface temperature of around 6,000°C.

Luminosity

This tells us how much more energy and light the star gives off compared with the Sun. This is how bright the star really is once distance has been taken into account. There is a huge variety in the luminosity of the stars. At one extreme, the star Alpha Centauri is 1.7 times more luminous than the Sun. At the other extreme, Canopus is 15,000 times more luminous than our Sun.

Luminosity can be measured indirectly by combining the apparent brightness of a star with its distance. It can also sometimes be measured directly from the spectrum.

Distance

The distance of a star is given in Light Years. This is the distance covered by a light beam in one year. Light travels at 300,000 km per second (186,000 miles per second). In one year a beam of light will travel 9.4 million million km (5.9 million million miles). This enormous distance is a Light Year.

Many stellar distances can be measured directly by trigonometry. As the Earth moves around the Sun, the star appears to shift its position against more distant stars. This effect is called parallax. It is a tiny effect but can be measured. The amount of the parallax depends on the diameter of the Earth’s orbit around the Sun (just under 300 million km or 186 million miles) and the distance to the star. A star with a paralax of 1 second of arc (written 1″) is said to be at a distace of 1 Parsec. 1 Parsec is equal to 3.26 Light Years.

Other stars can have their luminosity measured by their spectra or by other properties. When this is compared to their apparent brightness, a distance can be calculated.

For more on astronomical distances look at The Scale Of The Universe.

Radial Velocity

This the velocity of the star relative to the Sun. Negative velocities denote a star moving towards the Solar System. Positive velocities are for stars moving away from us.

Radial velocity is easily measured by looking at the star’s spectrum. The lines on the spectrum are shifted to the blue end if the star is moving towards us (the so-called blue shift) and to the red end if the star is moving away from us (red shift). The amount of this shift depends on the relative velocity between us and the star.

Credits: http://www.krysstal.com/brightest.html

(heavenswithlamps.wordpress.com)

100 Guide Posts in the Sky

 
The following list contains the 100 brightest stars as seen from the earth at night. The information on magnitudes is taken from data obtained by the Hipparcos Satellite Catalog. Distance measurements are from the Observer’s Handbook 2001, by The Royal Astronomical Society of Canada.

Common Name

Astronomical Name

Meaning

Apparent Magnitude

Absolute Magnitude

Distance (light-years)

1

Sirius Alpha Canis Majoris Greek: “scorching”

-1.44

1.45

9

2

Canopus Alpha Carinae Greek: pilot of the ship Argo

-0.62

-5.53

313

3

Arcturus Alpha Bootis Greek: “guardian of the bear”

-0.05

-0.31

37

4

Rigel Kentaurus Alpha Centauri Arabic: “foot of the centaur”

-0.01

4.34

4

5

Vega Alpha Lyrae Arabic: eagle or vulture

0.03

0.58

25

6

Capella Alpha Aurigae Latin: “little she-goat”

0.08

-0.48

42

7

Rigel Beta Orionis Arabic: “foot”

0.18

-6.69

773

8

Procyon Alpha Canis Minoris Greek: “before the dog”

0.40

2.68

11

9

Betelgeuse Alpha Orionis Arabic: “armpit of the great one”

0.45

-5.14

522

10

Achernar Alpha Eridani Arabic: “river’s end”

0.45

-2.77

144

11

Hadar (Agena) Beta Centauri Arabic: “ground” (Latin: “knee”)

0.61

-5.42

526

12

Altair Alpha Aquilae Arabic: “the eagle”

0.76

2.20

17

13

Acrux Alpha Crucis Greek: comb. of alpha crux

0.77

-4.19

321

14

Aldebaran Alpha Tauri Arabic: “the follower”

0.87

-0.63

65

15

Spica Alpha Virginis Latin: ear of wheat

0.98

-3.55

262

16

Antares Alpha Scorpii Greek: rival of Mars

1.06

-5.28

604

17

Pollux Beta Geminorum Greek: immortal Gemini twin brother

1.16

1.09

34

18

Formalhaut Alpha Piscis Austrini Arabic: “the mouth of the fish”

1.17

1.74

25

19

Deneb Alpha Cygni Arabic: “tail”

1.25

-8.73

1467

20

Mimosa Beta Crucis Latin: “actor”

1.25

-3.92

352

21

Regulus Alpha Leonis Greek: “little king”

1.36

-0.52

77

22

Adhara Epsilon Canis Majoris Arabic: “the virgins”

1.50

-4.10

431

23

Castor Alpha Geminorum Greek: mortal Gemini twin brother

1.58

0.59

52

24

Gacrux Gamma Crucis Greek: comb. of gamma and crux

1.59

-0.56

88

25

Shaula Lambda Scorpii Arabic: “stinger”

1.62

-5.05

359

26

Bellatrix Gamma Orionis Greek: an Amazon warrior

1.64

-2.72

243

27

Alnath Beta Tauri Arabic: “the butting one”

1.65

-1.37

131

28

Miaplacidus Beta Carinae Arabic/Latin: “peaceful waters”

1.67

-0.99

111

29

Alnilam Epsilon Orionis Arabic: “string of pearls”

1.69

-6.38

1342

30

Alnair Alpha Gruis Arabic: “the bright one”

1.73

-0.73

101

31

Alnitak Zeta Orionis Arabic: “the girdle”

1.74

-5.26

817

32

Regor Gamma Velorum unknown

1.75

-5.31

840

33

Alioth Epsilon Ursae Majoris Arabic: “the bull”

1.76

-0.21

81

34

Kaus Australis Epsilon Sagittarii Arabic/Latin: “southern part of the bow”

1.79

-1.44

145

35

Mirphak Alpha Persei Arabic: “elbow”

1.79

-4.50

592

36

Dubhe Alpha Ursae Majoris Arabic: “bear”

1.81

-1.08

124

37

Wezen Delta Canis Majoris Arabic: “weight”

1.83

-6.87

1791

38

Alkaid Eta Ursae Majoris Arabic: chief of the mourners

1.85

-0.60

101

39

Sargas Theta Scorpii Sumerian: “scorpion”

1.86

-2.75

272

40

Avior Epsilon Carinae unknown

1.86

-4.58

632

41

Menkalinan Beta Aurigae Arabic: “shoulder of the rein-holder”

1.90

-0.10

82

42

Atria Alpha Trianguli Australis Greek/English: combination of alpha and triangle

1.91

-3.62

415

43

Delta Velorum Delta Velorum Bayer designation*

1.93

-0.01

80

44

Alhena Gamma Geminorum Arabic: “the mark” on the right side of a camel’s neck

1.93

-0.60

105

45

Peacock Alpha Pavonis English: Peacock

1.94

-1.81

183

46

Polaris Alpha Ursae Minoris Latin: pole star

1.97

-3.64

431

47

Mirzam Beta Canis Majoris Arabic: “herald”

1.98

-3.95

499

48

Alphard Alpha Hydrae Arabic: “the solitary one”

1.99

-1.69

177

49

Algieba Gamma Leonis Arabic: “the forehead”

2.01

-0.92

126

50

Hamal Alpha Arietis Arabic: “lamb”

2.01

0.48

66

51

Deneb Kaitos Beta Ceti Arabic/Greek: “tail of the sea monster”

2.04

-0.30

96

52

Nunki Sigma Sagittarii ancient Babylonian name

2.05

-2.14

224

53

Merkent Theta Centauri Arabic: “in the shoulder of the centaur”

2.06

0.70

61

54

Saiph Kappa Orionis Arabic: “sword”

2.07

-4.65

815

55

Alpheratz Alpha Andromedae Arabic: “horse’s shoulder”

2.07

-0.30

97

56

Beta Gruis Beta Gruis Bayer designation*

2.07

-1.52

170

57

Mirach Beta Andromedae Arabic: “girdle”

2.07

-1.86

199

58

Kochab Beta Ursae Minoris Arabic: unknown meaning

2.07

-0.87

126

59

Rasalhague Alpha Ophiuchi Arabic: “head of the serpent-charmer”

2.08

1.30

47

60

Algol Beta Persei Arabic: “the demon’s head”

2.09

-0.18

93

61

Almaak Gamma Andromedae Arabic: type of small, predatory animal in Arabia

2.10

-3.08

355

62

Denebola Beta Leonis Arabic: “lion’s tail”

2.14

1.92

36

63

Cih Gamma Cassiopeiae Chinese: “whip”

2.15

-4.22

613

64

Muliphain Gamma Centauri Arabic: “oath”

2.20

-0.81

130

65

Naos Zeta Puppis Greek: “ship”

2.21

-5.95

1399

66

Tureis Iota Carinae Arabic: an ornament on a ship’s stern

2.21

-4.42

694

67

Alphecca (Gemma) Alpha Coronae Borealis Arabic: “bright one of the dish” (Latin: gem)

2.22

0.42

75

68

Suhail Lambda Velorum Arabic: an honorific title of respect

2.23

-3.99

573

69

Sadir Gamma Cygni Arabic: a birds breast

2.23

-6.12

522

70

Mizar Zeta Ursae Majoris Arabic: “groin”

2.23

0.33

78

71

Schedar Alpha Cassiopeiae Arabic: “beast”

2.24

-1.99

228

72

Eltanin Gamma Draconis Arabic: “the dragon’s head”

2.24

-1.04

148

73

Mintaka Delta Orionis Arabic: “belt”

2.25

-4.99

916

74

Caph Beta Cassiopeiae Arabic: “hand”

2.28

1.17

54

75

Dschubba Delta Scorpii Arabic: “forehead”

2.29

-3.16

522

76

Hao Epsilon Scorpii Chinese: “queen”

2.29

0.78

65

77

Epsilon Centauri Epsilon Centauri Bayer designation*

2.29

-3.02

376

78

Alpha Lupi Alpha Lupi Bayer designation*

2.30

-3.83

548

79

Eta Centauri Eta Centauri Bayer designation*

2.33

-2.55

308

80

Merak Beta Ursae Majoris Arabic: “flank”

2.34

0.41

79

81

Izar Epsilon Bootis Arabic: “girdle”

2.35

-1.69

210

82

Enif Epsilon Pegasi Arabic: “nose”

2.38

-4.19

672

83

Kappa Scorpii Kappa Scorpii Bayer designation*

2.39

-3.38

464

84

Ankaa Alpha Phoenicis Arabic: name of a legendary bird

2.40

0.52

77

85

Phecda Gamma Ursae Majoris Arabic: “thigh”

2.41

0.36

84

86

Sabik Eta Ophiuchi Arabic: unknown meaning

2.43

0.37

84

87

Scheat Beta Pegasi Arabic: “shin”

2.44

-1.49

199

88

Alderamin Alpha Cephei Arabic: “the right arm”

2.45

1.58

49

89

Aludra Eta Canis Majoris Arabic: “virginity”

2.45

-7.51

3196

90

Kappa Velorum Kappa Velorum Bayer designation*

2.47

-3.62

539

91

Gienah Epsilon Cygni Arabic: “wing”

2.48

0.76

72

92

Markab Alpha Pegasi Arabic: saddle

2.49

-0.67

140

93

Han Zeta Ophiuchi Chinese: an ancient feudal state in China

2.54

-3.20

458

94

Menkar Alpha Ceti Arabic: “nose”

2.54

-1.61

220

95

Alnair Zeta Centauri Arabic: “the bright one”

2.55

-2.81

384

96

Graffias Beta Scorpii Arabic(?): claws

2.56

-3.50

530

97

Zosma Delta Leonis Greek: “girdle”

2.56

1.32

58

98

Ma Wei Delta Centauri Chinese: “the horse’s tail”

2.58

-2.84

395

99

Arneb Alpha Leporis Arabic: “hare”

2.58

-5.40

1283

100

Gienah Ghurab Gamma Corvi Arabic: “right wing of the raven”

2.58

-0.94

165

* Bayer designation: names given to stars by astronomer Johanne Bayer in his 1603 star atlas Uranometria. The designations consist of a Greek letter followed by the genitive (possessive) form of the constellation name that the star is found in. They were generally named starting with the brightest star and continuing to the dimmest of any given constellation.

Free Lecture 02: Universe Scale, and Light 1

A lecture to study the nerdy part of the Big Universe. Do you think it’s a good way to kick-start your Sunday morning? It’s what I did. It was a mind-blowing experience. But what intrigues me is:  Why is this Universe so big?

Lecture 02: Universe Scale, and Light

The lecture video is embedded below but also available here in MP4 format.
Additionally, slides used in the lecture are embedded below but also are available here in Powerpoint format.
Questions after the lecture? Please ask them in here.

Wikipedia entries:
Earth’s atmosphere
Light
Black body
Wein’s Law
Stefan Boltzmann Law

What Interested ME in this lecture.

Web sites
Secret Worlds: The Universe Within
Atlas of the Universe
Notes:
Alpha Centauri is a system.
proxima Centauri is part of  this system.
Black Body Radiation
The hotter you are the more you radiate light. This is why we say “she’s Hot”.
Humans emit light. On the higher stratas of humanity, if you’re spiritually high you shine or radiate.
Human beings emit infra-red light. That is the reason in infrared light, people glow.
Black Body Spectra
Blue is hot than red.
White is hot than blue.
I believe Black is hotter than white. though we can’t see black light. Is Dark Matter black light. Has this been proved scientifically?
Open Cluster
I appreciated the saying Open stars are like Jewel Box
Last slide
We’ll be ending early today. WAeee!!!
Revisiting Albireo. Albireo was mentioned in Turn Left to Orion.
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