NGC 3766

{{Short description|Open cluster in the constellation Centaurus}}

{{Infobox open cluster

| name = NGC 3766

| image = 300px

| caption = NGC 3766 image taken with the MPG/ESO 1.2-metre telescope at the La Silla Observatory{{cite news|title=New Kind of Variable Star Discovered|url=http://www.eso.org/public/news/eso1326/|access-date=14 June 2013|newspaper=ESO Press Release}}

| credit = ESO

| constellation = Centaurus

| epoch = J2000

| class =

| ra = 11^h 36.1^m

| dec = −61° 37{{prime}}

| dist_ly = 5.5 kly

| dist_pc =

| appmag_v = 5.3

| size_v = 12.0{{prime}}

| mass_kg =

| mass_msol =

| radius_ly = 9.6 ly

| v_hb =

| age =

| notes = Easy to view via binoculars or telescope

| names = NGC 3766, Caldwell 97, Collinder 248, Melotte 107, Dunlop 289, Lacaille III.7, C1133-613

}}

File:NGC3766map.png

NGC 3766 (also known as Caldwell 97) is an open star cluster in the southern constellation Centaurus. It is located in the vast star-forming region known as the Carina molecular cloud, and was discovered by Nicolas Louis de Lacaille during his astrometric survey in 1751–1752.{{cite journal

| title=The search for the nebulae - VI

| last=Jones | first=K. G.

| journal=Journal of the British Astronomical Association

| volume=79 | pages=213–222 | date=March 1969

| bibcode=1969JBAA...79..213J

}} At a distance of about 1745 pc,{{cite simbad | title=NGC 3766 | access-date=2013-06-13}} the cluster subtends a diameter of about 12 minutes of arc.{{cite web | title=WEBDA Astronomical Database | work = WEBDA Page for NGC 3766 | url=http://www.univie.ac.at/webda/cgi-bin/ocl_page.cgi?cluster=ngc+3766 | access-date=2013-06-13}}

There are 137 listed stars, but many are likely non-members, with only 36 having accurate photometric data.{{cite web | title=Webda Astronomical Database | work = WEBDA Page for NGC 3766a | url=http://www.univie.ac.at/webda/cgi-bin/frame_list.cgi?ngc3766 | access-date=2013-06-13}} It has a total apparent magnitude of 5.3 and integrated spectral type of B1.7. NGC 3766 is relatively young, with an estimated age of log (7.160) or 14.4 million years, and is approaching us at 14.8 km/s. This cluster contains eleven Be stars, two red supergiants and four Ap stars.

36 examples of an unusual type of variable star were discovered in the cluster. These fast-rotating pulsating B-type stars vary by only a few hundredths of a magnitude with periods less than half a day. They are main sequence stars, hotter than δ Scuti variables and cooler than slowly pulsating B stars.{{cite journal|doi=10.1093/mnras/stx346|arxiv=1702.02306|title=Period–luminosity relations of fast-rotating B-type stars in the young open cluster NGC 3766|journal=Monthly Notices of the Royal Astronomical Society|volume=467|issue=4|pages=3864|year=2017|last1=Saio|first1=H|last2=Ekström|first2=S|last3=Mowlavi|first3=N|last4=Georgy|first4=C|last5=Saesen|first5=S|last6=Eggenberger|first6=P|last7=Semaan|first7=T|last8=Salmon|first8=S. J. A. J|doi-access=free |bibcode=2017MNRAS.467.3864S}}