Triangulum II

Galaxy in the constellation Triangulum

Triangulum II

Observation data (J2000 epoch)
Constellation| Triangulum
Right ascension| 02h 13m 17.4s[1]
Declination| +36° 10′ 42.4″[1]
Distance| 97.8 ± 6.5 kly (30 ± 2 kpc)[1]
Characteristics
Mass/Light ratio| 3600 (V)[1] M☉/L☉
Apparent size (V)| 3.9′[1]
Other designations
Triangulum II, Tri II, Laevens 2, Lae 2

Triangulum II (Tri II or Laevens 2) is a dwarf galaxy close to the Milky Way Galaxy. Like other dwarf spheroidal galaxies, its stellar population is very old: the galaxy was quenched before 11.5 billion years ago.[2] It contains only 1000 stars, yet is quite massive, having a solar mass to light ratio of 3600.[3] This is an unusually high mass for such a small galaxy.[4]

The distance from the centre of the Milky Way is 26 kpc (85 kly). The luminosity is 450 times that of the Sun.[3] This makes it one of the dimmest known galaxies.[3] The 2D half light radius is 34 pc (110 ly). The galaxy was discovered in images taken by Pan-STARRS by Benjamin P. M. Laevens in 2015.[1][3]

Triangulum II is a candidate for detecting WIMPs as a source of dark matter.[4]

## References[edit]

1. ^ a b c d e f Laevens, Benjamin P. M.; Martin, Nicolas F.; Ibata, Rodrigo A.; Rix, Hans-Walter; Bernard, Edouard J.; Bell, Eric F.; Sesar, Branimir; Ferguson, Annette M. N.; Schlafly, Edward F.; Slater, Colin T.; et al. (31 March 2015). "A New Faint Milky Way Satellite Discovered in the PAN-STARRS1 3π Survey" (PDF). The Astrophysical Journal. 802 (2): L18. arXiv:1503.05554. Bibcode:2015ApJ...802L..18L. doi:10.1088/2041-8205/802/2/L18. S2CID 54179272.
2. ^ Sacchi, Elena; Richstein, Hannah; Kallivayalil, Nitya; Van Der Marel, Roeland; Libralato, Mattia; Zivick, Paul; Besla, Gurtina; Brown, Thomas M.; Choi, Yumi; Deason, Alis; Fritz, Tobias; Geha, Marla; Guhathakurta, Puragra; Jeon, Myoungwon; Kirby, Evan; Majewski, Steven R.; Patel, Ekta; Simon, Joshua D.; Tony Sohn, Sangmo; Tollerud, Erik; Wetzel, Andrew (2021). "Star Formation Histories of Ultra-faint Dwarf Galaxies: Environmental Differences between Magellanic and Non-Magellanic Satellites?". The Astrophysical Journal Letters. 920 (1): L19. arXiv:2108.04271. Bibcode:2021ApJ...920L..19S. doi:10.3847/2041-8213/ac2aa3. S2CID 236965965.
3. ^ a b c d Kirby, Evan N.; Cohen, Judith G.; Simon, Joshua D.; Guhathakurta, Puragra (16 November 2015). "Triangulum II: Possibly a Very Dense Ultra-Faint Dwarf Galaxy". The Astrophysical Journal. 814 (1): L7. arXiv:1510.03856. Bibcode:2015ApJ...814L...7K. doi:10.1088/2041-8205/814/1/L7. S2CID 13600560.
4. ^ a b Dajose, Lori (18 November 2015). "Dark matter dominates in nearby dwarf galaxy". Phys.org. Retrieved 19 November 2015.; Lori Dajose (November 18, 2015). "Dark Matter Dominates in Nearby Dwarf Galaxy". Caltech. Retrieved December 16, 2015.

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Constellation of Triangulum

* List of stars in Triangulum
* Triangulum in Chinese astronomy

Stars|

| Bayer|

* α (Mothallah)
* β
* γ
* δ
* ε
* ι

|

Flamsteed|

* 1
* 5
* 7
* 10
* 11
* 12
* 13
* 14
* 15

Variable|

* R
* V
* X
* RW
* XX

HR|

* 438
* 485
* 490
* 503
* 523
* 564
* 726
* 738
* 757
* 761

HD|

* 9446
* 13189
* 13747

Other|

* M33-013406.63
* M33 X-7
* Romano's Star
* Var 2
* Var 19
* Var 83
* Var A
* Var B
* Var C
* LSPM J0207+3331

| Exoplanets|

* HAT-P-38b
* HD 9446 b
* HD 9446 c
* HD 13189 b
* Ross 19 b

|

| Nebulae|

* 588
* 595
* 604

|

Galaxies|

| NGC|

* Triangulum Galaxy
* 608
* 634
* 669
* 670
* 672
* 684
* 688
* 736
* 739
* 740
* 750
* 751
* 769
* 777
* 784
* 804
* 805
* 819
* 855
* 860
* 861
* 890
* 925
* 931
* 940
* 941
* 953
* 959
* 970
* 973
* 1060

|

Numbered|

* I
* II

Other|

* Arp 166
* RD1

Category

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Milky Way

Location|

Milky Way → Milky Way subgroup → Local Group → Local Sheet → Virgo Supercluster → Laniakea Supercluster → KBC Void → Observable universe → Universe
Each arrow (→) may be read as "within" or "part of".

The Milky Way Galaxy

Structure|

| Galactic Center|

* Sagittarius A
* Sagittarius A*
* Fermi bubbles
* Supermassive black hole

|

Disk|

* Carina–Sagittarius
* Norma–Cygnus
* Orion–Cygnus
* Perseus
* Scutum–Centaurus
* Near 3 kpc Arm
* Far 3 kpc Arm

Halo|

* Aquarius Stream
* Fimbulthul stream
* Gaia Sausage
* Helmi stream
* Magellanic Stream
* Monoceros Ring
* Palomar 5 stream
* Pisces-Eridanus stream
* Sagittarius Stream
* Virgo Stream

Satellite
galaxies|

| Magellanic Clouds|

* Large Magellanic Cloud
* Small Magellanic Cloud
* Magellanic Bridge

|

Dwarfs|

* Antlia II
* Boötes I
* Boötes II
* Boötes III
* Canes Venatici I
* Canes Venatici II
* Canis Major
* Carina
* Coma Berenices
* Crater 2
* Draco
* Eridanus II
* Fornax
* Hercules
* Leo I
* Leo II
* Leo IV
* Leo V
* Leo T
* Phoenix
* Pisces Overdensity
* Pisces II
* Reticulum II
* Sagittarius Spheroidal
* Segue 1
* Segue 2
* Sculptor
* Sextans
* Triangulum II
* Ursa Major I
* Ursa Major II
* Ursa Minor
* Virgo I
* Willman 1

Related|

* Alternate names
* Andromeda–Milky Way collision
* Baade's Window
* In mythology
* Zone of Avoidance

* Astronomy portal
* Category

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