# Messier Index/M82

Messier 82 (also known as NGC 3034 or the Cigar Galaxy) is the prototype nearby w:starburst galaxy about 12 million w:light-years away in the w:constellation w:Ursa Major. The starburst galaxy is five times as bright as the whole w:Milky Way and one hundred times as bright as our galaxy's center.
In 2005, the Hubble revealed 197 young massive clusters in the starburst core. The average mass of these clusters is around 2×10$^5$ M$_⊙$, hence the starburst core is a very energetic and high-density environment. Throughout the galaxy's center, young stars are being born 10 times faster than they are inside our entire Milky Way Galaxy.

## Messier 81 triggering starburst

Forming a striking pair in small w:telescopes with nearby spiral M81, M82 is being physically affected by its larger neighbor. Tidal forces caused by w:gravity have deformed this w:galaxy, a process that started about 100 million years ago. This interaction has caused star formation to increase 10 fold compared to "normal" galaxies.
Recently, M82 has undergone at least one tidal encounter with M81 resulting in a large amount of gas being funneled into the galaxy's core over the last 200 Myr. The most recent such encounter is thought to have happened around 2–5×10$^8$ years ago and resulted in a concentrated starburst together with a corresponding marked peak in the cluster age distribution. This starburst ran for up to ~50 Myr at a rate of ~10 M$_⊙$ per year. Two subsequent startbursts followed, the last (~4–6 Myr ago) of which may have formed the core clusters, both super star clusters (SSCs) and their lighter counterparts.
Ignoring any difference in their respective distances from us, the centers of M81 and M82 are visually separated by about 130,000 light-years. The actual separation is 300$^{+300}$$_{−200}$ kly.

## Starburst region

In the core of M82, the active starburst region spans a diameter of 500 pc. In optical, there are four high surface brightness regions or clumps (designated A, C, D, and E). These clumps correspond to known sources at w:X-ray, w:infrared, and radio frequencies. Consequently, they are thought to be the least obscured starburst clusters from our vantage point. M82's unique bipolar outflow (or 'superwind') appears to be concentrated on clumps A and C and fueled by the energy injected by w:supernova that occur about once every ten years.
The w:Chandra X-ray Observatory detected fluctuating w:X-ray emissions from a location approximately 600 light-years away from the center of M82. Astronomers have postulated that this fluctuating emission comes from the first known w:intermediate-mass black hole, of roughly 200 to 5000 w:solar masses. M82, like most galaxies, hosts a supermassive black hole at its center with a mass of approximately 3 x 10$^7$ solar masses as measured from stellar dynamics.

## Structure

M82 was previously believed to be an irregular galaxy. However, in w:2005, two symmetric w:spiral arms were discovered in the w:near-infrared (NIR) images of M82. The arms were detected by subtracting an w:axisymmetric exponential disk from the NIR images. These arms emanate from the ends of the NIR bar and can be followed for the length of 3 disc scales. Even though the arms were detected in the NIR images, they are bluer than the disk. Assuming that the northern part of M82 is nearer to us, which most literature assumes, the observed sense of rotation implies trailing arms. Due to M82's high disk w:surface brightness, nearly edge-on orientation (~80°) with respect to us, and the presence of a complex network of dusty filaments in optical images, the arms were not previously detected.

## External links

* M82, SEDS Messier pages
* M82 at Chandra
* SST: Galaxy on Fire!
* M82 at NASA/IPAC EXTRAGALACTIC DATABASE
* ESA/Hubble images of M82
* M82 The Cigar Galaxy

## References

* 1 2 3 4 5 6 7 "NASA/IPAC Extragalactic Database". Results for NGC 3034. Retrieved 2006-10-27.
* 1 2 Karachentsev, I. D.; Kashibadze, O. G. (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". 3 light years. 49 (1): 3–18. doi:10.1007/s10511-006-0002-6.{{cite journal}}: CS1 maint: multiple names: authors list (link)
* 1 2 3 4 5 6 7 8 9 10 11 12 13 Barker, S.; de Grijs, R.; Cerviño, M. (June 2008), "Star cluster versus field star formation in the nucleus of the prototype starburst galaxy M 82", Astronomy and Astrophysics, 484 (3): 711–720, doi:10.1051/0004-6361:200809653{{citation}}: CS1 maint: date and year (link)
* ↑ Happy Sweet Sixteen, Hubble Telescope! Newswise, Retrieved on w:July 30, w:2008.
* ↑ Declination separation of 36′.87 and Right Ascension separation of 9′.5 gives via w:Pythagorean theorem a visual separation of 38′.07; Average distance of 11.65 Mly × sin(38′.07) = 130,000 ly visual separation.
* ↑ Separation = sqrt(D$_{M81}$$^2$ + D$_{M82}$$^2$ - 2 D$_{M81}$ D$_{M82}$ Cos(38′.07)) assuming the error direction is about the same for both objects.
* ↑ Patruno, A.; Portegies Zwart, S.; Dewi, J.; Hopman, C. (2006). "The ultraluminous X-ray source in M82: an intermediate-mass black hole with a giant companion". Monthly Notices of the Royal Astronomical Society: Letters. 370 (1): L6–L9. doi:10.1111/j.1745-3933.2006.00176.x.{{cite journal}}: CS1 maint: multiple names: authors list (link)
* ↑ Gaffney, N. I., Lester, D. F., and Telesco, C. M. (1993). ""The stellar velocity dispersion in the nucleus of M82"". w:Astrophysical Journal Letters. 407: L57–L60. doi:10.1086/186805. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
* ↑ Mayya, Y. D.; Carrasco, L.; Luna, A. (2005). "The Discovery of Spiral Arms in the Starburst Galaxy M82". The Astrophysical Journal. 628 (1): L33–L36. doi:10.1086/432644.{{cite journal}}: CS1 maint: multiple names: authors list (link)