NGC 7635 is an emission nebula in the constellation Cassiopeia, discovered by the British-German astronomer William Herschel on November 3, 1787. It is also called the Bubble Nebula, because of its round shape. It looks like a planetary nebula with an 8th magnitude star right in front of it. However, the central star of the nebula is built quite eccentrically. It is possible that the object is not a typical planetary nebula, but that the stellar wind of the central star has "blown" it into the surrounding environment filled with ionized hydrogen. This ionized cloud of matter is designated Sh 152. The nebula has a size of about 3.3' by 3 and a brightness of about 8.5 mag, but this figure also includes its ionizing star, which lies in the brightest (northern) part of the nebula. Therefore, it can only be observed in medium-sized and large telescopes. =x193iq5w xeuugli x13faqbe x1vvkbs x1xmvt09 x1lliihq x1s928wv xhkezso x1gmr53x x1cpjm7i x1fgarty x1943h6x xudqn12 x3x7a5m x6prxxf xvq8zen xo1l8bm xzsf02u x1yc453hMessier 52 or M 52 or NGC 7654 is an open star cluster located in the western part of the constellation Cassiopeia. The cluster was discovered by the French astronomer Charles Messier on September 7, 1774 while searching for comets. In the following century, William Parsons estimated the number of stars in it at 200. In 1959, Ake Wallenquist discovered that 193 stars physically belong to the cluster. According to more recent measurements, there are about 130 stars up to the 14th magnitude. In 1998, the presence of a variable star of the Delta Scuti type was confirmed in it.=x193iq5w xeuugli x13faqbe x1vvkbs x1xmvt09 x1lliihq x1s928wv xhkezso x1gmr53x x1cpjm7i x1fgarty x1943h6x xudqn12 x3x7a5m x6prxxf xvq8zen xo1l8bm xzsf02u x1yc453hNGC 7538, near the more famous Bubble Nebula, is located in the constellation Cepheus. It is located about 9,100 light-years from Earth. It is home to the biggest yet discovered protostar which is about 300 times the size of the Solar System. It is located in the Perseus Arm of the Milky Way and is probably part of the Cassiopeia OB2 complex. It is a region of active star formation including several luminous near-IR and far-IR sources. Stars in NGC 7538 are mainly low-mass pre-main-sequence stars.