THE WORLD ACCORDING TO SROYON
"Oh my God!—it's full of stars!"
—Dr David Bowman in 2001: A Space Odyssey
I took this photo of the Milky Way at Lone Pine, California.
If you move your cursor over the image below, colour-coded squares (see key to the right) will appear around certain celestial objects. Click on a square to see the object's name and some information about it. Move your cursor out of the image to again see the original image without the squares.
To see constellation lines and names, move your cursor to the "Show constellations" button at the top right of the image.
If it doesn't work, check that your browser has JavaScript enabled. If it still doesn't work, please let me know. Please also let me know if you spot a factual error, or if you know of an interesting celestial object in the field of view that is not currently "clickable".
Disclaimer: I only have an amateur interest in stars. Anasua and I identified most of the stars in the photo with Stellarium, an excellent free open-source virtual planetarium. Most of the content was compiled from Wikipedia and astronomy websites.
Key
| star/star system | |
| star cluster | |
| nebula | |
| black hole | |
| terrestrial rock |
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| • | Hi-res image | ||||||||
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Photo details:
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Show constellations
Night sky over Lone Pine, California (36°35'N 118°05'W)
5 June 2014, 2:38 am PDT
5 June 2014, 2:38 am PDT
A short note about Messier objects
Messier objects are a set of 110 astronomical objects – mostly "deep-sky objects" including star clusters, nebulae, stellar corpses, globular clusters and galaxies.
The list is named after the 18th century French astronomer Charles Messier who catalogued, and in some cases discovered, most of these objects. Messier was not looking for deep-sky objects. He was a comet hunter, and was frustrated by objects which resembled but were not comets, so he compiled a list of them.
There are 27 clickable Messier objects in the above image: M4, M6, M7, M8, M9, M10, M11, M12, M14, M16, M17, M18, M19, M20, M22, M23, M24, M25, M26, M28, M54, M55, M62, M69, M70, M80 and M107. Also in the frame, but not individually clickable, are the open cluster M21 (just to the upper left of M20), and the globular cluster M75 (too faint to be seen in the photo).
Messier objects are a set of 110 astronomical objects – mostly "deep-sky objects" including star clusters, nebulae, stellar corpses, globular clusters and galaxies.
The list is named after the 18th century French astronomer Charles Messier who catalogued, and in some cases discovered, most of these objects. Messier was not looking for deep-sky objects. He was a comet hunter, and was frustrated by objects which resembled but were not comets, so he compiled a list of them.
There are 27 clickable Messier objects in the above image: M4, M6, M7, M8, M9, M10, M11, M12, M14, M16, M17, M18, M19, M20, M22, M23, M24, M25, M26, M28, M54, M55, M62, M69, M70, M80 and M107. Also in the frame, but not individually clickable, are the open cluster M21 (just to the upper left of M20), and the globular cluster M75 (too faint to be seen in the photo).
Alpha Scorpii (Antares)
Other facts
Table 1: Apparent visual magnitudes (V) of certain celestial objects
Smaller numbers indicate greater brightness.
| type: | red supergiant |
| constellation: | Scorpius |
| apparent magnitude: | +0.96 (a measure of its brightness as seen from Earth; see Table 1 below) |
| B–V colour index: | +1.83 (implies it is red; see Table 2 below) |
| distance: | 550 light years |
| mass: | 12.4 M☉ (M☉ = mass of the Sun) |
| radius: | 883 R☉ (R☉ = radius of the Sun) |
| temperature: | 3,400 K |
Other facts
- Antares gets its name from the ancient Greek for "rival of Mars" due to the similarity of its reddish hue to the appearance of the planet Mars.
- It is the brightest star in the constellation Scorpius (and in my photo) and the sixteenth brightest star in the night sky.
- The Hitchhiker's Guide to the Galaxy mentions a smuggling racket involving Antarean parakeet glands, a revolting but much sought-after cocktail delicacy.
- With a radius 883 times that of the sun, Antares is massive enough to eventually explode as a brilliant supernova. The event may be a million years off, or it may occur tonight.
Table 1: Apparent visual magnitudes (V) of certain celestial objects
Smaller numbers indicate greater brightness.
| (V) | Celestial object |
|---|---|
| −26.74 | Sun as seen from Earth (about 400,000 times brighter than mean full moon) |
| −12.74 | Mean brightness of full moon |
| −5.9 | Maximum brightness of the International Space Station |
| −4.89 | Maximum brightness of Venus |
| −2.94 | Maximum brightness of Jupiter |
| −2.91 | Maximum brightness of Mars |
| −1.47 | Sirius, the brightest star (except for the Sun) at visible wavelengths |
| 3 to 4 | Faintest stars visible in an urban neighbourhood with naked eye |
| 3.44 | Andromeda Galaxy (M31) |
| 6.50 | Approximate limit of stars observed by a mean naked eye observer under very good conditions. There are about 9,500 stars visible to mag 6.5. |
| 31.50 | Faintest objects observable in visible light with Hubble Space Telescope |
Table 2
Smaller numbers indicate bluer (hotter) stars; larger numbers indicate redder (cooler) stars.
Smaller numbers indicate bluer (hotter) stars; larger numbers indicate redder (cooler) stars.
| B–V colour index | Conventional colour description |
|---|---|
| −0.33 | Blue |
| −0.17 | Blue-white |
| 0.15 | White with bluish tinge |
| 0.44 | Yellow-White |
| 0.68 | Yellow |
| 1.15 | Orange |
| 1.64 | Red |
Terrestrial rock
Possibly 82–85 million year old biotite monzogranite
Possibly 82–85 million year old biotite monzogranite
Beta Scorpii (Acrab or Graffias)
Other facts
| type: | multiple star system |
| constellation: | Scorpius |
| apparent magnitude: | +2.63 (a measure of its brightness as seen from Earth; see Table 1 below) |
| B–V colour index: | −0.08 / −0.02 (implies it is blue-white; see Table 2 below) |
| distance: | 550 light years |
Other facts
- Beta Scorpii is a system of six stars orbiting each other.
- 'Acrab' is derived from the Arabic al-'Aqrab (the Scorpion). 'Graffias' may be derived from the Greek grapsaios (crab). The ideas and words for crab and scorpion were almost interchangeable in ancient Greece, from the belief that the latter creature was generated from the former.
- It appears on the flag of Brazil, symbolising the state of Maranhão.
Delta Scorpii (Dschubba)
Other facts
| type: | blue-white subgiant |
| constellation: | Scorpius |
| apparent magnitude: | +2.31 (a measure of its brightness as seen from Earth; see Table 1 below) |
| B–V colour index: | −0.12 (implies it is blue-white; see Table 2 below) |
| distance: | 490 light years |
| mass: | 14.6-14.9 M☉ (M☉ = mass of the Sun) |
| radius: | 6.7 R☉ (R☉ = radius of the Sun) |
| temperature: | 29,500 K |
Other facts
- 'Dschubba' is derived from the Arabic al-jabhah meaning 'forehead' (of the Scorpion).
- Since 2000, the star has been observed to be much brighter than its previous constant magnitude, perhaps because it is throwing off luminous gases from its equatorial region.
Pi Scorpii
Other facts
| type: | triple star system |
| constellation: | Scorpius |
| apparent magnitude: | +2.89 (a measure of its brightness as seen from Earth; see Table 1 below) |
| B–V colour index: | −0.19 (implies it is blue; see Table 2 below) |
| distance: | 590 light years |
Other facts
- Pi Scorpii consists of a pair of binary stars orbited by a smaller, more distant companion. The binary stars orbit each other with a period of only 1.57 days, and are in synchronous rotation, i.e. they perpetually show the same "faces" to each other.
Delta Ophiuchi (Yed Prior)
Other facts
| type: | red giant |
| constellation: | Ophiuchus |
| apparent magnitude: | +2.75 (a measure of its brightness as seen from Earth; see Table 1 below) |
| B–V colour index: | +1.59 (implies it is orange; see Table 2 below) |
| distance: | 171 light years |
| mass: | 1.5 M☉ (M☉ = mass of the Sun) |
| radius: | 59 R☉ (R☉ = radius of the Sun) |
| temperature: | 3,679 K |
Other facts
- 'Yed' is derived from Arabic meaning 'the hand' (of the Ophiuchus, serpent-bearer). The star is called 'Prior' because it leads Yed Posterior, the star to its east, in the apparent east-to-west movement of the stars across the night sky.
Epsilon Ophiuchi (Yed Posterior)
Other facts
| type: | yellow giant |
| constellation: | Ophiuchus |
| apparent magnitude: | +3.22 (a measure of its brightness as seen from Earth; see Table 1 below) |
| B–V colour index: | +0.97 (implies it is yellow; see Table 2 below) |
| distance: | 106 light years |
| mass: | 1.85 M☉ (M☉ = mass of the Sun) |
| radius: | 10.39 R☉ (R☉ = radius of the Sun) |
| temperature: | 4,918 K |
Other facts
- 'Yed' is derived from Arabic meaning 'the hand' (of the Ophiuchus, serpent-bearer). The star is called 'Posterior' because it follows Yed Prior, the star to its west, in the apparent east-to-west movement of the stars across the night sky.
Zeta Ophiuchi
Other facts
| type: | blue main-sequence star |
| constellation: | Ophiuchus |
| apparent magnitude: | +2.57 (a measure of its brightness as seen from Earth; see Table 1 below) |
| B–V colour index: | +0.03 (implies it is blue-white; see Table 2 below) |
| distance: | 366 light years |
| mass: | 20 M☉ (M☉ = mass of the Sun) |
| radius: | 8.5 R☉ (R☉ = radius of the Sun) |
| temperature: | 34,000 K |
Other facts
- "O-type" stars like Zeta Oph form the hottest class of stars. They emit intense ultraviolet light, and so appear bluish white to the naked eye.
- Zeta Oph is a "runaway star": it seems to have been expelled from a binary star system when its more massive companion was destroyed in a supernova explosion. The companion was reduced to a tiny "neutron star" about the size of a small town, while the newly-single Zeta Oph was shot off like a bullet.
- Zeta Oph is rotating rapidly and may be close to the velocity at which it would begin to break up.
- On 6 April 2010, the asteroid Anastasia 824 occluded (i.e. hid) Zeta Oph causing the star to suddenly vanish and reappear a few seconds later.
Eta Ophiuchi (Sabik)
Other facts
| type: | binary star system |
| constellation: | Ophiuchus |
| apparent magnitude: | +2.43 (a measure of its brightness as seen from Earth; see Table 1 below) |
| B–V colour index: | +0.05 (implies it is blue-white; see Table 2 below) |
| distance: | 88 light years |
Other facts
- For an oberver on Uranus, Sabik would be the northern pole star.
Tau Sagittarii
Other facts
| type: | orange giant |
| constellation: | Sagittarius |
| apparent magnitude: | +3.33 (a measure of its brightness as seen from Earth; see Table 1 below) |
| B–V colour index: | +1.17 (implies it is orange; see Table 2 below) |
| distance: | 122 light years |
| mass: | 1.5–2 M☉ (M☉ = mass of the Sun) |
| radius: | 16 R☉ (R☉ = radius of the Sun) |
| temperature: | 4,860 K |
Other facts
- Tau Sagittarii is the closest visible star in the night sky to the origin of the 1977 "Wow! signal", a radio signal that could conceivably have been a sign of extraterrestrial intelligence.
Zeta Sagittarii (Ascella)
Other facts
| type: | binary star system |
| constellation: | Sagittarius |
| apparent magnitude: | +2.59 (a measure of its brightness as seen from Earth; see Table 1 below) |
| B–V colour index: | +0.08 (implies it is blue-white; see Table 2 below) |
| distance: | 88 light years |
Other facts
- 'Ascella' comes from a Late Latin word meaning 'armpit' (of Sagittarius, the archer).
Phi Sagittarii
| type: | blue-white giant/subgiant |
| constellation: | Sagittarius |
| apparent magnitude: | +3.17 (a measure of its brightness as seen from Earth; see Table 1 below) |
| B–V colour index: | −0.11 (implies it is blue-white; see Table 2 below) |
| distance: | 239 light years |
| mass: | 4–4.2 M☉ (M☉ = mass of the Sun) |
| radius: | 4.8 R☉ (R☉ = radius of the Sun) |
| temperature: | 14,990 K |
Sigma Sagittarii (Nunki)
Other facts
| type: | blue-white main sequence star |
| constellation: | Sagittarius |
| apparent magnitude: | +2.05 (a measure of its brightness as seen from Earth; see Table 1 below) |
| B–V colour index: | −0.20 (implies it is blue; see Table 2 below) |
| distance: | 228 light years |
| mass: | 7.8 M☉ (M☉ = mass of the Sun) |
| radius: | 4.5 R☉ (R☉ = radius of the Sun) |
| temperature: | 18,890 K |
Other facts
- 'Nunki' is a Babylonian name thought to represent the sacred Babylonian city of Eridu on the Euphrates, which would make it the oldest star name currently in use.
Epsilon Sagittarii (Kaus Australis)
Other facts
| type: | binary star system |
| constellation: | Sagittarius |
| apparent magnitude: | +1.85 (a measure of its brightness as seen from Earth; see Table 1 below) |
| B–V colour index: | −0.03 (implies it is blue-white; see Table 2 below) |
| distance: | 143 light years |
Other facts
- The name 'Kaus Australis' comes from Arabic qaws (bow) and Latin austrālis (southern); it is to the south of Kaus Media (middle) and Kaus Borealis (north).
- It is the brightest star in the constellation Sagittarius.
Lagoon Nebula (Messier 8)
Other facts
| type: | diffuse emission nebula |
| constellation: | Sagittarius |
| apparent magnitude: | +6.0 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 4,100 light years |
| radius: | 55 × 20 light years |
Other facts
- A nebula is an interstellar cloud of dust and gases, and is often a "stellar nursery" where new stars are being born.
- The Lagoon Nebula contains Bok globules (dark, collapsing clouds of proto-stellar material), and a tornado-like structure caused by a superhot star that emanates ultraviolet light, heating and ionizing gases on the surface of the nebula.
Image of the Lagoon Nebula, captured by the VLT Survey Telescope, Chile. Credit: ESO/VPHAS+ team
Ptolemy Cluster (Messier 7)
Other facts
| type: | open cluster |
| constellation: | Scorpius |
| apparent magnitude: | +3.3 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 980 light years |
| radius: | 25 light years |
Other facts
- An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. They are loosely bound to each other by mutual gravitational attraction.
- Messier 7 is also known as the Ptolemy Cluster after the Alexandrian astronomer Ptolemy, who first recorded in 130 AD.
- Messier 7 is the southernmost Messier object. Messier could not catalogue more southerly deep-sky objects because from his location, Paris, part of the southern celestial sphere is not visible.
- Messier 7 is the second brightest of all Messier objects (behind the Pleiades).
Image of the Ptolemy Cluster, captured by the MPG/ESO 2.2-metre telescope, Chile. Credit: ESO
Trifid Nebula (Messier 20)
Other facts
| type: | diffuse nebula; a combination of an emission nebula, a reflection nebula and a dark nebula |
| constellation: | Sagittarius |
| apparent magnitude: | +6.3 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 5,200 light years |
Other facts
- A nebula is an interstellar cloud of dust and gases, and is often a "stellar nursery" where new stars are being born.
- The Trifid Nebula is an unusual combination of an emission nebula (which emits light from ionised gas), a reflection nebula (which does not emit much visible light, but is near stars and reflects light from them) and a dark nebula (which does not emit much visible light, but may be detected as an opaque cloud blocking light from luminous objects behind it).
- Just to the upper left of the Trifid Nebula is another Messier object, open cluster M21.
Image of the Trifid Nebula, captured by the Palomar 1.5-m telescope, California. Credit: NASA
Butterfly Cluster (Messier 6)
Other facts
| type: | open cluster |
| constellation: | Scorpius |
| apparent magnitude: | +4.2 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 1,600 light years |
| radius: | 6 light years |
Other facts
- An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. They are loosely bound to each other by mutual gravitational attraction.
Image of the Butterfly Cluster, captured by the Burrell Schmidt Telescope, Arizona. Credit: N.A.Sharp, Mark Hanna, REU program/NOAO/AURA/NSF
Messier 18
Other facts
| type: | open cluster |
| constellation: | Sagittarius |
| apparent magnitude: | +7.5 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 4,900 light years |
| radius: | 9 light years |
Other facts
- An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. They are loosely bound to each other by mutual gravitational attraction.
Image of Messier 18, from the Two Micron All Sky Survey. Credit: Atlas Image courtesy of 2MASS/UMass/IPAC-Caltech/NASA/NSF
Omega Nebula (Messier 17)
Other facts
| type: | diffuse emission nebula |
| constellation: | Sagittarius |
| apparent magnitude: | +6.0 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 5,000–6,000 light years |
| radius: | 7.5 light years |
Other facts
- A nebula is an interstellar cloud of dust and gases, and is often a "stellar nursery" where new stars are being born.
- The Omega Nebula is one of the brightest and most massive star-forming regions of our galaxy.
Image of a section of the Omega Nebula, captured by the Hubble Space Telescope. Credit: NASA
Eagle Nebula (Messier 16)
Other facts
| type: | diffuse emission nebula |
| constellation: | Serpens |
| apparent magnitude: | +6.0 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 7,000 light years |
| radius: | 70×55 light years |
Other facts
- A nebula is an interstellar cloud of dust and gases, and is often a "stellar nursery" where new stars are being born.
- The "Pillars of Creation" are massive (up to four light years tall) star-forming columns of gas and dust within the Eagle Nebula. They may have been destroyed about 6,000 years ago by a supernova explosion, but the light showing us the destruction will not reach Earth for another millennium.
Image of the Pillars of Creation in the Eagle Nebula, captured by the Hubble Space Telescope. Credit: NASA
Wild Duck Cluster (Messier 11)
Other facts
| type: | open cluster |
| constellation: | Scutum |
| apparent magnitude: | +6.3 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 6,200 light years |
Other facts
- An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. They are loosely bound to each other by mutual gravitational attraction.
- The Wild Duck Cluster's name derives from the brighter stars forming a triangle which could represent a flock of ducks in flight.
Image of the Wild Duck Cluster. Credit: NASA
NGC 6441
Other facts
| type: | globular cluster |
| constellation: | Scorpius |
| apparent magnitude: | +7.15 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 12,700 light years |
Other facts
- A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Unlike open clusters, globular clusters are very tightly bound by gravity.
- NGC 6441 is only 4' east of the bright star G Scorpii, and is therefore indistinguishable from G Scorpii in the photo.
- NGC 6441 is one of only four globular clusters known to contain a planetary nebula (an expanding glowing shell of ionized gas ejected from old red giant stars late in their lives). The other three are Messier 22 (visible and marked in the photo) Messier 15 (not in the frame of the photo) and Palomar 6 (in the frame of the photo but too faint to be seen).
Image showing NGC 6441 (below) and G Scorpii (above). Credit: Mischa Schirmer
Beta Capricorni (Dabih)
Other facts
| type: | star system |
| constellation: | Capricornus |
| apparent magnitude: | +3.05 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 328 light years |
Other facts
- 'Dabih' is derived from the Arabic al-dhābiḥ (slaughterer). The name refers to the ancient Arabic ceremonial sacrifices performed annually when Capricorn first became visible in the eastern sky.
Sigma Scorpii (Al Niyat)
Other facts
| type: | star system |
| constellation: | Scorpius |
| apparent magnitude: | +2.88 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 568 light years |
Other facts
- 'Al Niyat' is derived from the Arabic an-niyāţ (arteries) and refers to both Sigma Scorpii and Tau Scorpii, the stars which flank Antares (the heart of the scorpion).
Sagittarius A*
Other facts
| type: | supermassive black hole |
| constellation: | Sagittarius |
| distance: | 25,900 light years (approx.) |
| mass: | 4,310,000 M☉ (approx.) (M☉ = mass of the Sun) |
Other facts
- Sagittarius A* (Sgr A* for short) is at the galactic centre, and is very likely to be the site of a supermassive black hole.
- Sgr A* cannot be seen in the photo – or even through astronomical instruments from Earth, at least not at visible wavelengths – because of interstellar extinction by dust and gas. We know its location because it is detectable as a source of strong radio waves.
- The name Sgr A* was coined by one of its discoverers because the radio source was "exciting" and excited states of atoms are denoted with asterisks.
- As of 2014, Sgr A* is in the process of interacting with, and possibly consuming, a giant gas cloud which is approaching the black hole. By observing this process, scientists are gaining a better understanding of how material accretes onto supermassive black holes.
Messier 4
Other facts
| type: | globular cluster |
| constellation: | Scorpius |
| apparent magnitude: | +5.9 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 7,200 light years |
| radius: | 35 light years |
Other facts
- A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Unlike open clusters, globular clusters are very tightly bound by gravity.
- Messier 4 was the first globular cluster in which individual stars were resolved.
Image of the centre of Messier 4, captured by the Hubble Space Telescope. Credit: ESA/Hubble & NASA
Messier 80
Other facts
| type: | globular cluster |
| constellation: | Scorpius |
| apparent magnitude: | +7.87 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 32,600 light years |
| radius: | 48 light years |
Other facts
- A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Unlike open clusters, globular clusters are very tightly bound by gravity.
Image of Messier 80, captured by the Hubble Space Telescope. Credit: NASA
Alpha Capricorni (Algedi)
Other facts
| type: | optical double star: α¹ Capricorni / α² Capricorni |
| constellation: | Capricornus |
| apparent magnitude: | +4.30 / +3.58 (a measure of its brightness as seen from Earth; see Table 1 below) |
| B–V colour index: | +0.60 / +0.89 (implies the stars are yellow/orange; see Table 2 below) |
| distance: | 690 / 109 light years |
| mass: | 5.3 / 2.6 M☉ (M☉ = mass of the Sun) |
| radius: | 40 / 8 R☉ (R☉ = radius of the Sun) |
Other facts
- Alpha Capricorni is an optical double star: a pair of stars (α¹ Capricorni and α² Capricorni) that lie at vastly different distances from Earth and are otherwise not associated at all, but due to a chance alignment, appear close to each other in the sky as seen from Earth. In the hi-res image the two components can be barely made out as partially superimposed stars.
- By an interesting coincidence, α¹ and α² both fall into a similar, relatively rare category: evolved, dying yellow "G-type" stars.
- In Hipparchos' time (circa 160-120 BC) α¹ and α² were only 4' apart, and it was only around the 17th century that they drifted sufficiently apart to be distinguishable by the naked eye. Their separation is increasing by 7" every 100 years.
Dark Horse Nebula
Other facts
| type: | dark nebula |
| constellation: | Ophiuchus |
Other facts
- A dark nebula is an interstellar cloud of dust and gases which does not emit much visible light, but may be detected as an opaque cloud blocking light from luminous objects behind it.
- The Dark Horse Nebula is a dark nebula in the distinct shape of a horse galloping northwards (see cropped image below).
- The ability to see the Dark Horse Nebula with the naked eye is an indication that the skies are very dark, i.e. not affected by light pollution.
Crop showing the Dark Horse Nebula
Messier 54
Other facts
| type: | globular cluster |
| constellation: | Sagittarius |
| apparent magnitude: | +8.37 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 87,400 light years |
| radius: | 153 light years |
Other facts
- A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Unlike open clusters, globular clusters are very tightly bound by gravity.
- For over two centuries after its discovery, Messier 54 was thought to belong to our galaxy, but it is now believed that it belongs to the Sagittarius Dwarf Elliptical Galaxy.
- Messier 54 will, however, become part of the Milky Way in the future because the strong gravitational pull of our galaxy is slowly engulfing the Sagittarius Dwarf Elliptical Galaxy.
Image of Messier 54, captured by the Hubble Space Telescope. Credit: ESA/Hubble & NASA
Delta Sagittarii (Kaus Media)
Other facts
| type: | double star |
| constellation: | Sagittarius |
| apparent magnitude: | +2.70 (a measure of its brightness as seen from Earth; see Table 1 below) |
| B–V colour index: | +1.38 (implies it is orange; see Table 2 below) |
| distance: | 348 light years |
Other facts
- The name 'Kaus Media' comes from Arabic qaws (bow) and Latin media (middle), because it is between Kaus Borealis (north) and Kaus Australis (south).
Lambda Sagittarii (Kaus Borealis)
Other facts
| type: | orange subgiant |
| constellation: | Sagittarius |
| apparent magnitude: | +2.82 (a measure of its brightness as seen from Earth; see Table 1 below) |
| B–V colour index: | +1.05 (implies it is orange; see Table 2 below) |
| distance: | 78 light years |
| mass: | 2.6 M☉ (M☉ = mass of the Sun) |
| radius: | 11 R☉ (R☉ = radius of the Sun) |
Other facts
- The name 'Kaus Borealis' comes from Arabic qaws (bow) and Latin boreālis (northern); it is to the north of Kaus Media (middle) and Kaus Australis (south).
Gamma Sagittarii (Alnasl)
Other facts
| type: | orange giant |
| constellation: | Sagittarius |
| apparent magnitude: | +2.98 (a measure of its brightness as seen from Earth; see Table 1 below) |
| B–V colour index: | +1.01 (implies it is orange; see Table 2 below) |
| distance: | 97 light years |
| mass: | 2 M☉ (M☉ = mass of the Sun) |
| radius: | 12 R☉ (R☉ = radius of the Sun) |
Other facts
- 'Alnasl' is derived from the Arabic al-naşl (arrowhead) because it forms the point of Sagittarius (the archer)'s arrow.
- It also forms the tip of the spout of the teapot-shaped asterism in Sagittarius. The Milky Way can be imagined as a plume of steam rising from the teapot's spout.
- The bright patch of the Milky Way above and to the right of Alnasl is the Great Sagittarius Star Cloud.
Messier 22
Other facts
| type: | globular cluster |
| constellation: | Sagittarius |
| apparent magnitude: | +5.1 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 10,600 light years |
Other facts
- A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Unlike open clusters, globular clusters are very tightly bound by gravity.
- Messier 22 is one of only four globular clusters known to contain a planetary nebula (an expanding glowing shell of ionized gas ejected from old red giant stars late in their lives). The other three are Messier 15 (not in the frame of the photo), NGC 6441 (in the frame of the photo and marked, but not distinguishable from the star G Scorpii) and Palomar 6 (in the frame of the photo but too faint to be seen).
Image of Messier 22, from the Two Micron All Sky Survey. Credit: Atlas Image courtesy of 2MASS/UMass/IPAC-Caltech/NASA/NSF
Messier 62
Other facts
| type: | globular cluster |
| constellation: | Ophiuchus |
| apparent magnitude: | +7.39 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 22,200 light years |
Other facts
- A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Unlike open clusters, globular clusters are very tightly bound by gravity.
Image of Messier 62, captured by the Hubble Space Telescope. Credit: NASA
The Sagittarius Star Cloud (Messier 24)
Other facts
| type: | pseudo-cluster of stars |
| constellation: | Sagittarius |
| apparent magnitude: | +4.6 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 10,000–16,000 light years |
Other facts
- The Sagittarius Star Cloud is not a "true" deep sky object, but a huge star cloud in the Milky Way, a pseudo-cluster of stars spread thousands of light years along the line of sight, perceived through a chance tunnel in the interstellar dust. The stars form part of a spiral arm of our galaxy.
Image of the Sagittarius Star Cloud, captured by the Burrell Schmidt Telescope, Arizona. Credit: Vanessa Harvey, REU program/NOAO/AURA/NSF
Messier 26
Other facts
| type: | open cluster |
| constellation: | Scutum |
| apparent magnitude: | +8.0 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 5,000 light years |
| radius: | 22 light years |
Other facts
- An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. They are loosely bound to each other by mutual gravitational attraction.
Image of Messier 26, captured by the Burrell Schmidt Telescope, Arizona. Credit: Hillary Mathis, Vanessa Harvey, REU program/NOAO/AURA/NSF
Messier 9
Other facts
| type: | globular cluster |
| constellation: | Ophiuchus |
| apparent magnitude: | +8.42 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 25,800 light years |
| radius: | 45 light years |
Other facts
- A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Unlike open clusters, globular clusters are very tightly bound by gravity.
- Messier 9 is one of the nearer globular clusters to the nucleus of the Milky Way. It appears slightly flattened due to the gravitational pull of the galactic core.
Image of Messier 9, captured by the Hubble Space Telescope. Credit: NASA & ESA
Messier 10
Other facts
| type: | globular cluster |
| constellation: | Ophiuchus |
| apparent magnitude: | +6.4 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 14,300 light years |
| radius: | 41.6 light years |
Other facts
- A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Unlike open clusters, globular clusters are very tightly bound by gravity.
Image of Messier 10, captured by the Hubble Space Telescope. Credit: ESA/NASA
Messier 12
Other facts
| type: | globular cluster |
| constellation: | Ophiuchus |
| apparent magnitude: | +7.68 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 15,700 light years |
| radius: | 37.2 light years |
Other facts
- A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Unlike open clusters, globular clusters are very tightly bound by gravity.
- Messier 12's orbit takes it very close to the nucleus of the Milky Way. Astronomers speculate that during its passage through the dense innermost regions of our galaxy, nearly one million low-mass stars have been ripped away from it by the gravitational pull of the galactic core. As the stellar stripping continues, in about 4.5 billion years Messier 12 is expected to dissociate completely.
Image of Messier 12, captured by the Hubble Space Telescope. Credit: ESA/Hubble & NASA
Messier 14
Other facts
| type: | globular cluster |
| constellation: | Ophiuchus |
| apparent magnitude: | +8.32 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 30,300 light years |
| radius: | 50 light years |
Other facts
- A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Unlike open clusters, globular clusters are very tightly bound by gravity.
Image of Messier 14 with by amateur telescope. Credit: Hewholooks - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons.
Messier 19
Other facts
| type: | globular cluster |
| constellation: | Ophiuchus |
| apparent magnitude: | +7.47 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 28,700 light years |
| radius: | 70 light years |
Other facts
- A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Unlike open clusters, globular clusters are very tightly bound by gravity.
Image of Messier 19, captured by the KPNO 0.9-Meter Telescope, Arizona. Credit: Doug Williams, N.A.Sharp/AURA/NOAO/NSF
Messier 107
Other facts
| type: | globular cluster |
| constellation: | Ophiuchus |
| apparent magnitude: | + 8.85 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 20,900 light years |
| radius: | 39.5 light years |
Other facts
- A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Unlike open clusters, globular clusters are very tightly bound by gravity.
- Messier 107 was not among the 103 objects catalogued by Charles Messier. Nevertheless a Messier number was assigned to it subsequently, as it was found to be mentioned in the notes of Messier's assistant, Pierre Méchain.
Image of Messier 107, captured by the Hubble Space Telescope. Credit: NASA
Messier 23
Other facts
| type: | open cluster |
| constellation: | Sagittarius |
| apparent magnitude: | +6.9 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 2,150 light years |
| radius: | 8 light years |
Other facts
- An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. They are loosely bound to each other by mutual gravitational attraction.
Image of Messier 23, from the Two Micron All Sky Survey. Credit: Atlas Image courtesy of 2MASS/UMass/IPAC-Caltech/NASA/NSF
Messier 25
Other facts
| type: | open cluster |
| constellation: | Sagittarius |
| apparent magnitude: | +4.6 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 2,000 light years |
| radius: | 10 light years |
Other facts
- An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. They are loosely bound to each other by mutual gravitational attraction.
Image of Messier 25, captured by the Burrell Schmidt Telescope, Arizona. Credit: Hillary Mathis, Vanessa Harvey, REU program/NOAO/AURA/NSF
Messier 28
Other facts
| type: | globular cluster |
| constellation: | Sagittarius |
| apparent magnitude: | +7.66 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 17,900 light years |
| radius: | 30 light years |
Other facts
- A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Unlike open clusters, globular clusters are very tightly bound by gravity.
- Among globular clusters, Messier 28 contains one of the largest known populations of millisecond pulsars. Millisecond pulsars are neutron stars that rotate over 100 times per second and emit a beam of electromagnetic radiation. Neutron stars are stellar remnants produced by the collapse of a massive star. They are the densest and tiniest stars known to exist in the universe, compressing half a million times Earth's mass into a ball no larger than a city.
Image of Messier 28, captured by the KPNO 0.9-Meter Telescope, Arizona. Credit: NOAO/AURA/NSF
Messier 55
Other facts
| type: | globular cluster |
| constellation: | Sagittarius |
| apparent magnitude: | +7.42 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 17,600 light years |
| radius: | 48 light years |
Other facts
- A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Unlike open clusters, globular clusters are very tightly bound by gravity.
- Messier 55 is also known as the Summer Rose Star.
Image of Messier 55, captured by the Hubble Space Telescope. Credit: NASA
Messier 69
Other facts
| type: | globular cluster |
| constellation: | Sagittarius |
| apparent magnitude: | +8.31 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 29,700 light years |
| radius: | 42 light years |
Other facts
- A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Unlike open clusters, globular clusters are very tightly bound by gravity.
Image of Messier 69, captured by the Hubble Space Telescope. Credit: NASA
Messier 70
Other facts
| type: | globular cluster |
| constellation: | Sagittarius |
| apparent magnitude: | +9.06 (a measure of its brightness as seen from Earth; see Table 1 below) |
| distance: | 29,400 light years |
| radius: | 34 light years |
Other facts
- A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Unlike open clusters, globular clusters are very tightly bound by gravity.
- Comet Hale–Bopp, perhaps the most widely observed comet of the 20th century, was discovered independently by Alan Hale and Thomas Bopp while they were observing Messier 70 through amateur telescopes.
Image of Messier 70, captured by the Hubble Space Telescope. Credit: NASA
