Weird Science

M103 - Open Cluster in Cassiopeia

Polish ver­sion is here

Mes­sier 103 (M103), also desi­gna­ted NGC 581, is an open star clu­ster loca­ted in the con­stel­la­tion Cas­sio­peia. Situ­a­ted appro­xi­ma­tely 8,000 to 9,500 light-years from Earth, it is among the most distant clu­sters listed in Mes­sier’s cata­log. Altho­ugh it may not be the most visu­ally impres­sive obse­rva­tion tar­get, M103 stands out due to its rela­ti­vely early stage of stel­lar evo­lu­tion.

The clu­ster is esti­ma­ted to be aro­und 25 mil­lion years old, pla­cing it among the youn­gest known exam­ples of its kind. Its stel­lar popu­la­tion is domi­na­ted by hot, blue B-type stars, along with seve­ral more evo­lved objects, inc­lu­ding a red super­giant with an appa­rent magni­tude of appro­xi­ma­tely 10m, loca­ted near the core. These fea­tu­res point to a sha­red ori­gin, sug­ge­sting that the stars for­med rela­ti­vely recen­tly from a sin­gle mole­cu­lar cloud com­po­sed of gas and dust.

Obse­rva­tions

Sep­tem­ber 10, 2025, about 10:00 p.m. - Kato­wice, Poland
urban con­di­tions, very high level of light pol­lu­tion

The star clu­ster fea­tu­red here lies about 1° nor­the­ast of Ruch­bah, also known as Delta Cas­sio­pe­iae (δ Cas). Its appa­rent magni­tude of 7.4m makes it rela­ti­vely easy to spot, even with a basic pair of bino­cu­lars.

Ilustracja: Fot. 1 - bez opisu

Fot. 1 - bez opisu

Ilustracja: Fot. 1 - z opisem

Fot. 1 - z opisem

One of the most distinc­tive aspects of Mes­sier 103 is its trian­gu­lar appe­a­rance. It is com­po­sed of rou­ghly 170 stars that are likely gra­vi­ta­tio­nally bound. The sys­tem stret­ches across about 15 light-years and is still par­tially enve­lo­ped in rem­nants of inter­stel­lar dust, which can influ­ence the appa­rent bri­ght­ness and color of its indi­vi­dual stars.

Thanks to spec­tro­sco­pic and pho­to­me­tric obse­rva­tions, com­bi­ned with data from the Gaia mis­sion, astro­no­mers have deter­mi­ned the pro­per motions and radial velo­ci­ties of stars in Mes­sier 103. These fin­dings con­firm that the stars ori­gi­na­ted from the same region of space. Altho­ugh M103 has not yet begun to break apart, it will even­tu­ally disperse over time, as is typi­cal for open clu­sters, pri­ma­rily due to the tidal for­ces exer­ted by the Milky Way.

While Mes­sier 103 may seem unre­mar­ka­ble com­pa­red to more visu­ally stun­ning clu­sters, it offers valu­a­ble insi­ght into early stel­lar evo­lu­tion and the inter­nal dyna­mics of young stel­lar sys­tems. For ama­teur astro­no­mers, it also pre­sents a rewar­ding tar­get, par­ti­cu­larly on clear autumn nights when Cas­sio­peia climbs high in the nor­thern sky.

Photo 1 Para­me­ters:

  • Total expo­sure time: 30 minu­tes (stack of 30 RAW fra­mes at 60s each, using an appro­priate num­ber of dark, bias, and flat fra­mes)
  • ISO: 1600
  • Mak­su­tov-Cas­se­grain tele­scope (100/1400), prime focus expo­sure
  • A fil­ter was used to reduce the effects of arti­fi­cial light pol­lu­tion and atmo­sphe­ric glow
  • Mount: equ­a­to­rial mount with trac­king, ali­gned using the drift method and con­trol­led by a custom-built sys­tem.

Fur­ther rea­dings:

Marek Ples

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