(June, July schedule)
Scorpius constellation is summer constellation and it is in best position for evening observing in July when it is low on the southern sky. We will observe it in June when it is low on the southern sky and in July when it is in best position for evening observing and it is low on the southern sky.
Double and multiple stars
Beta Scorpii - It has several names, some of them are Acrab and Elacrab. The combined apparent visual magnitude of this star on the sky is 2.5. It is about 400 light years away from the Earth.
The first component has visual magnitude 2.6 and in fact consists of three stars. One star is spectroscopic binary system with period of several days and the other is separated about 4 arc seconds from the first one on the sky, and makes one orbit around their combined center of mass in 600 years.
The second component has visual magnitude 4.9 on the sky and also consists of three stars. One of the star is in fact spectroscopic binary and they have orbital period of about 10 days and at some distance away of them orbits around them third star with orbital period of around 40 years. Even in a telescope still these three stars appear like one.
The separation between the first and the second component on the sky is 14 arc seconds. Most of these six stars are hot and massive stars, only several millions years old.
Nu Scorpii - Its name is Jabbah. It is multiple star system which we see on the sky as one star with total apparent visual magnitude 4.0. It is about 440 light years away from the Earth.
The first component is multiple star system and consists of two stars with visual magnitudes 4.4 and 6.3 separated on the sky 1.3 arc seconds. In a telescope this component will appear like egg-shaped because the telescope can not completely split the stars. The 4.4 star by itself is spectroscopic binary star which can not be resolved at all in a telescope. If you can imagine the previously mentioned two stars how will appear like one egg-shaped star in a telescope, then this spectroscopic binary consists of two components which are 5,000 times closer. That is why they can not be resolved even with the most powerful optical telescope. The stars which make up the first components are hot and massive subgiant stars.
The second component is separated on the sky 41 arc seconds from the first component. It consists of two stars with visual magnitudes on the sky 6.5 and 7.2 separated 2.4 arc seconds. Separation of 2.4 arc seconds is bigger than 1.3 arc seconds, thus the telescope should be able to split these two stars completely. these two stars are also hot and massive stars, but they are still on the main sequence.
Alpha Scorpii - Its name is Antares. It is the brightest star in the constellation Scorpius. Its apparent visual magnitude on the sky is 1.0. It is about 520 light years away from the Earth. It is massive star with mass about 15 solar masses and diameter 900 times bigger than the diameter of our Sun. It is young star, about 12 million years old, but because of its large mass it evolved quickly, spent its core hydrogen and start expanding. It left the main sequence and now is supergiant star on its evolution stage. Its surface temperature is around 3,400 K and that temperature gives the star orange color which can be noticed even with naked eye. Because of its large mass, astronomers think that in the next million years will explode as a supernova. If that happen, it will be visible even daytime for several months, the same as the supernova which exploded in 1054.
The companion has apparent visual magnitude on the sky 5.4 and is separated by 2.5 arc seconds from Antares. It is bright enough to be seen even with naked eye, but in fact it is hard to find it even with a telescope. That is because it is too close on the sky to Antares and it is hidden in its glare. The companion is hot and massive main sequence star with mass and diameter several times bigger than our Sun and surface temperature about 19,000 K.
Xi Scorpii - Its combined visual magnitude on the sky is 4.2. The brightest component consists of two stars which are hard to resolve with a telescope. They have visual magnitudes on the sky 4.9 and 5.1 and orbital period about 50 years. They are subgiant and main sequence star, slightly more massive and larger than our Sun. The dimmer component is separated by 8 arc second from the brighter component and have visual magnitude on the sky 7.3. This binary star system is about 80 light years away from the Earth.
While we look at Xi Scorpii in a telescope, in the same field of view we can also see the double star Struve 1999 which is separated about 280 arc seconds on the sky from Xi Scorpii. The components of Struve 1999 have visual magnitudes 7.5 and 8.1 and are separated from each other 12 arc seconds on the sky. Probably the components are smaller and cooler than our Sun, and should have yellow-orange color if they are bright enough in a telescope so our vision to be able to detect any colors. If not, we will see them white.
Deep sky objects
(will be observed only from dark location outside of the city)