Facts
The Teapot asterism is formed by some of the brightest stars in the zodiac constellation Sagittarius — Delta, Epsilon, Gamma-2, Lambda, Zeta, Phi, Tau and Sigma Sagittarii.
Sigma and Tau Sagittarii mark the handle, Delta, Epsilon, Zeta and Phi Sagittarii form the body, Lambda Sagittarii marks the lid of the teapot and Gamma-2 Sagittarii marks the top of the spout.
The asterism is prominent in the southern sky and lies next to a dense area of the Milky Way. Under exceptionally good conditions, the Milky Way appears as steam coming out of the spout of the Teapot. The best time to observe Sagittarius as a northern hemisphere observer is during the summer, when the constellation reaches its highest point above the southern horizon.
The constellation of Sagittarius is, unlike the Teapot asterism, difficult to make out. In mythology, the constellation represents a centaur – the mythical half-human, half-horse creature – holding a bow and aiming an arrow toward the celestial Scorpion. The Teapot marks different parts of the centaur figure.
There are a number of deep sky objects also located in the Teapot asterism, some of which are not part of the Sagittarius constellation.
Stars
Kaus Australis
Kaus Australis, also known as Epsilon Sagittarii is the brightest star in the constellation Sagittarius and the 36th brightest star in the night sky. It is a binary star that is a blue class B giant. It has an apparent magnitude of 1.79 and a luminosity 375 times that of the Sun. This star also has a faint 14th magnitude companion 32 arc seconds away.
Kaus Australis is located around 143 light years away from us. With stars Delta and Lambda Sagittarii, it makes up the archers bow, making the base. Its name comes from the Arabic word for “bow” (qaws) and the Latin word for “southern” (australis).
Nunki
Nunki, also known as Sigma Sagittarii, is the second brightest star in the constellation Sagittarius, with an apparent magnitude of 2.1. It is a hydrogen fusing dwarf star that belongs to the spectral type B2.5 V. Nunki is located around 228 light years away from Earth.
It has a luminosity that is around 3,300 times that of the Sun and a mass that is around 7 times that of the Sun. Nunki is a fast rotator, spinning at more than 200 kilometres per second, which is about 100 times faster than the Sun. The star also has a faint companion with a magnitude of 9.5. It is located around 5.2 arc minutes away.
Sigma Sagittarii is located close to the ecliptic and it can sometimes be occulted by the Moon and, very rarely, by planets. It is also known for being the brightest star that can be occulted by an exterior planet.
It is unknown where the name Nunki comes from, but it is thought to be of either Babylonian or Assyrian origin.
Ascella
Ascella, also known as Zeta Sagittarii, is the third brightest star in the constellation of Sagittarius. It is a binary star consists of a class A2 giant star with an apparent magnitude of 3.26 and an A4 type subgiant star with an apparent magnitude of 3.37. The two stars are separated by 13.4 astronomical units and they have a combined apparent magnitude of 2.60. There is also a dim companion 75 arc seconds away that is a 10th magnitude star.
Ascella is located around 89.1 light years from Earth. Its name means “armpit” in Latin.
Kaus Media
Kaus Media, also known as Delta Sagittarii, is a multiple star system in Sagittarius that has an apparent magnitude of 2.72. It belongs to the spectral type K3III and is located around 306 light years away.
Delta Sagittarii is around 1180 times more luminous than the Sun and has a radius that is 62 times that of the Sun and a mass that is five times that of the Sun. The primary component also has three dim companions: Delta Sagittarii B, a 14th magnitude star 26 arc seconds away, Delta Sagittarii C, a 15th magnitude star 40 arc seconds away, and Delta Sagittarii D, a 13th magnitude star 58 arc seconds away.
The name Kaus Media means “the middle bow”.
Kaus Borealis
Kaus Borealis, also known as Lambda Sagittarii, is an orange giant star, belonging to the spectral class K1+IIIb in Sagittarius. It points to the famous interstellar cloud, the Lagoon Nebula. Its name means “the northern bow”.
Lambda Sagittarii has an apparent magnitude of 2.82, making it 52 times more luminous than the Sun. It also has a radius that is 11 times that of the Sun and is around 77.3 light years away from us.
Kaus Borealis is sometimes refer to as a clump star, meaning that it is one undergoing the final stages of its existence, but is stable nevertheless and fusing helium into carbon and oxygen in its core. It also lies very close to the ecliptic, is occasionally occulted by the Moon and, more rarely, by planets.
Nanto
Nanto, also known as Phi Sagittarii, is the ninth brightest star in the constellation of Sagittarius. It is a B8 class giant with an apparent magnitude of 3.17. Nanto is around 231 light years from Earth and can be spotted without binoculars. It is 475 times more luminous than the Sun, 4.8 times larger and about 4 times more massive. It has a temperature of 14,990 K.
Hecatebolus
Hecatebolus, also known as Tau Sagittarii, is an orange giant star belonging to the spectral type K1 or K2 in Sagittarius. It has an apparent magnitude of 3.32 and a radius 16 times that of the Sun and a mass 1.5 times that of the Sun. Tau Sagittarii is located 120 light years away from Earth and has a surface temperature of 4,860 K.
It is also a suspected binary star, even though a companion has never been confirmed. Hecatebolus is the closest visible star to the origin of the Wow! signal, which was a strong narrowband radio signal received on August 15, 1977. The Wow! signal was the only possible sign of extra-terrestrial intelligence ever discovered. It appeared to have come from an area of the sky without any stars or planets, just to the northwest of the globular cluster M55, the Summer Rose Star.
Deep Sky Objects
Messier 18
Messier 18, also known as M18 or NGC 6613, an open star cluster with an apparent magnitude of 7.5 in Sagittarius constellation.
It was originally discovered by Charles Messier in 1764 and is located approximately 4,900 light years away from us, between the Sagittarius Star Cloud (Messier 24) and the Omega Nebula (Messier 17). It is a whopping nine light years in radius and is thought to be about 32 million years old.
Messier 21
Messier 21, also known as M21 or NGC 6531, is an open star cluster that was first discovered by Charles Messier in June 1764. It is located in Sagittarius constellation.
It is a relatively young cluster, only 4.6 million years old, and it contains at least 57 stars. Messier 21 has an apparent magnitude of 6.5. It is located around 4,250 light years from Earth.
Sagittarius Cluster
Sagittarius Cluster, also known as Messier 22, M22 or NGC 6656, is one of the brightest globular star clusters in the sky and has an apparent magnitude of 5.1. It is located in the constellation of Sagittarius and can be found above the Teapot asterism.
It is elliptical in shape and one of the nearest globular star clusters to Earth, around 10,600 light years away. Sagittarius Cluster is about 32 arc minutes across in size and is located near the galactic bulge, the central group of stars in the Milky Way.
Messier 22 is notable for being one of only four known globular clusters that contain a planetary nebula. It was originally discovered by the German amateur astronomer Johann Abraham Ihle in 1665, and then Messier included the cluster in his catalogue in June 1764.
Messier 23
Messier 23, also known as M23 or NGC 6494, is an open star cluster that has an apparent magnitude of 6.9 in Sagittarius constellation.
It is thought to be around 220 million years old and was first discovered in June 1764 by Charles Messier. Messier 23 is about 2,150 light years away from us and is 15-20 light years in radius. It contains around 150 stars, and the brightest one has a magnitude of 9.2.
Messier 25
Messier 25, also known as M25 or IC 4725, is an open cluster that is located around 2,000 light years from Earth in Sagittarius constellation. It lies above the Teapot asterism.
It was first discovered by Philippe Loys De Chéseaux in 1745 and then added to Messier’s catalogue in 1764. Messier 25 has an apparent magnitude of 4.6 and measures around 19 light years across. It is thought to be at leats 90 million years old.
Messier 28
Messier 28, also known as M28 or NGC 6626, is a globular cluster that has an apparent magnitude of 7.66 in Sagittarius constellation. It lies above the Teapot asterism.
It contains 18 RR Lyrae type variable stars which are pulsating stars belonging to the spectral class A (and occasionally F). The stars usually have a mass of about half the Sun’s. The Messier 28 cluster is located around 8,000 and 19,000 light years from us, near Lambda Sagittarii (Kaus Borealis).
Messier 54
Messier 54, also known as M54 or NGC 6715, is a dense globular cluster that was discovered by Charles Messier in 1778 in Sagittarius constellation. It can be found at the base of the Teapot asterism.
It is located 87,400 light years away from us, lying close to the star Zeta Sagittarii. Messier 54 also belongs to the Sagittarius Dwarf Elliptical Galaxy. M54 has an apparent magnitude of 8.37 and measures about 150 light years across.
Messier 69
Messier 69, also known as M69 or NGC 6637, is a globular cluster that was first discovered by Charles Messier on August 31, 1780. It was discovered at the same time as Messier 70.
It is located in Sagittarius constellation, at the base of the Teapot asterism. Messier 69 is only 1,800 light years away from Messier 70, located around 29,700 light years distant from Earth near the Galactic center.
Messier 69 has an apparent magnitude of 8.31 and contains very few variable stars. It has a radius that is 42 light years across.
Messier 70
Messier 70, also known as M70 or NGC 6681, is a globular cluster that was discovered by Charles Messier on August 31, 1780, as the same times as M69. This cluster is located near to the Galactic center, around 29,300 light years from Earth.
It is located in Sagittarius constellation, around the base of the Teapot asterism.
It has an apparent magnitude of 9.06 and a radius of 34 light years.
Trifid Nebula
The Trifid Nebula, also known as Messier 20, M20 or NGC 6514, is a bright, colourful emission and reflection nebula in Sagittarius constellation. The bottom part of the nebula is an emission nebula and the upper part is a reflection nebula. There is also an open cluster. It can be observed through a small telescope.
The Trifid Nebula has an apparent magnitude of 6.3 and is an H II region, containing a stellar nursery full of embryonic stars. It is located around 5,200 light years away from us and is about 28 arc minutes across in size.
Lagoon Nebula
Lagoon Nebula, also known as Messier 8, M8 or NGC 6523, is a large interstellar cloud classified as an emission nebula, with an apparent magnitude of 6.0. It is one of the H II regions in Sagittarius and one of only two nebulae that are star forming regions and can be seen by naked eye.
NGC 6523 is around 4,100 light years away from us. In the center of the Messier object, there is a structure known as the Hourglass Nebula that contains several Herbig-Haro objects, small patches of nebulosity indicating that there are newly born stars in the vicinity.
Messier 8 was first discovered by the French astronomer Guillaume Le Gentil in 1747.
Omega Nebula
The Omega Nebula, also known as Messier 17, M17, NGC 6618, Swan, Horseshoe or Lobster Nebula, is an emission nebula that is located in the H II region of the constellation of Sagittarius. It was originally discovered by the Swiss astronomer Jean-Philippe Loys De Chéseaux in 1745, but Messier included it in his catalogue in 1764.
Messier 17 has an apparent magnitude of 6.0 and contains an open cluster of 35 hot young stars which illuminate its gases. It is located between 5,000 and 6,000 light years away from us and is about 15 light years in diameter.
Sagittarius Star Cloud (Delle Caustiche)
Sagittarius Star Cloud, also known as Delle Caustiche, Messier 24, M24, NGC 6603 or IC 4715, is a star cloud in the constellation of Sagittarius. It is the densest concentration of stars that can be seen using binoculars. Around a thousand stars can be seen within a single field of view.
The Sagittarius Star Cloud was first discovered in 1764 by Charles Messier. It is part of the Sagittarius or Sagittarius-Carina spiral arms of the Milky Way. Messier 24 is about 600 light years wide and is located around 10,000 light years away from us.
The Eagle Nebula
The Eagle Nebula, also known as Messier 16, M16, NGC 6611 and sometimes even the Star Queen Nebula, is a nebula with a young open star cluster in Serpens constellation. It was discovered by the Swiss astronomer Jean-Philippe de Chéseaux in 1745. M16 is part of the diffuse emission nebula IC 4703 and roughly resembles an eagle, which is how it got its name.
Messier 16 contains the Pillars of Creation, which are a large region of star-formation. They are thought to already have been destroyed by a supernova explosion between 8,000 to 9,000 years ago, but this image will likely not reach Earth for another 1,000 years.
Other Deep Sky Objects
Other notable deep sky objects in the Teapot asterism are the Butterfly Cluster (M6) and the Ptolemy Cluster (M7) found to the right, in the constellation Scorpius, and the Cat’s Paw Nebula (NGC 6334) and the War and Peace Nebula (NGC 6357) also found in Scorpius.
The Galactic Centre
The Galactic Centre is the rotational centre of the Milky Way where it is at its densest in the sky. It is lies in the direction of Sagittarius, around 25,000 to 28,000 light years away from Earth. The galactic centre can’t be observed with regular telescopes because clouds of dust and gas block our view of the Milky Way’s core. The region can only be studied in X-ray and radio wavelengths.
Sagittarius A, which is a radio source that is located at the center of the Milky Way, consisting of the supernova remnant Sagittarius A East, the spiral structure Sagittarius A West, and a bright radio source located at the centre of the spiral, Sagittarius A*, was adopted as the true zero coordinate point of the Milky Way centre by the International Astronomical Union in 1958.
Sagittarius A* is thought to be the location of the supermassive black hole believed to be at the centre of the Milky Way Galaxy. This is because stars orbit the object at speeds greater than those of any other stars found in the Milky Way.
Image Sources:
- Photograph: European Space Agency – https://bityl.co/7FiF
- By Fabian Rodriguez Frustaglia – https://commons.wikimedia.org/w/index.php?curid=95657047
- By Rick Saunders – https://commons.wikimedia.org/w/index.php?curid=95611628
- By ESA/Hubble, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=39499950
- By Sergio Eguivar – https://commons.wikimedia.org/w/index.php?curid=95750437
- By Starhopper – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=65487989
- By Credits: NASA, ESA, STScI, R. Buonanno (Universita di Roma Tor Vergata), K. Gebhardt (University of Texas at Austin), J. Grindlay (Harvard University), and F. Ferraro (Universita di Bologna) – https://commons.wikimedia.org/w/index.php?curid=63522029
- By ESA/Hubble & NASA – https://commons.wikimedia.org/w/index.php?curid=17288442
- By en:NASA, en:STScI, en:WikiSky – en:WikiSky's snapshot tool – [1], Public Domain, https://commons.wikimedia.org/w/index.php?curid=4561389
- By en:NASA, en:STScI, en:WikiSky – en:WikiSky's snapshot tool – [1], Public Domain, https://commons.wikimedia.org/w/index.php?curid=4491049
- Public Domain, https://commons.wikimedia.org/w/index.php?curid=67560
- By ESO/VPHAS+ team – http://www.eso.org/public/images/eso1403a/, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=30759954
- By ESO/INAF-VST/OmegaCAM. Acknowledgement: OmegaCen/Astro-WISE/Kapteyn Institute – https://commons.wikimedia.org/w/index.php?curid=26367295
- By Roberto Colombari – https://commons.wikimedia.org/w/index.php?curid=94466196
- By ESO – https://commons.wikimedia.org/w/index.php?curid=7338740
- By 2MASS/G. Kopan, R. Hurt – Atlas Image [or Atlas Image mosaic] obtained as part of the Two Micron All Sky Survey (2MASS), a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. https://commons.wikimedia.org/w/index.php?curid=2166391