Ursa Minor is one of the most famous constellations in our sky. The reason for this lies in its brightest star, which is called the Polar Star. It is known for the fact that the North Pole of the world is located nearby, which means that it is easy to determine the direction to the north. But the interesting facts about the Little Bear, as this group of stars is also called, do not end there.
1. How to find Ursa Minor?
Everyone knows that the Polar Star is located at the end of the long “tail” of the constellation Ursa Minor. It is usually suggested to look for it with the help of a much more noticeable Ursa Major. The two extreme stars of its “dipper” point precisely to the star lying near the North Pole of the celestial sphere.
But if you are watching the starry sky near your home or in a familiar area where you know the directions to different sides of the world, there is no need for this — just look to the north. No matter what time of the year and no matter what hour it is, the “dipper” of Ursa Minor will be there. Unlike other stars, it does not travel across the firmament and does not hide behind the horizon, but only rotates around the North Star. The main thing is that the sky is not covered with clouds.
2. Is Alpha Ursa Minor really a Polar Star?
Alpha Ursa Minor is the brightest star in this constellation. The word “polar”, by which it is designated, directly indicates that it is located at the North Pole of the world. However, this is a proper name assigned to this particular luminary. But due to the precession of the axis of rotation, the position of the pole of the world is slowly changing all the time.
Accordingly, the star closest to it is changing. α Ursa Minor became it only in 1100, and before the beginning of our era, for 2000 years, β Ursa Major (Kochab) was the closest to the north pole of the world — the “lower” star of the two that form the front part of the “dipper” of Ursa Minor.
3. How many stars are in the “dipper” of Ursa Minor?
The brightest stars of Ursa Minor, like the Ursa Major, form a figure in which you can see a quadrangle, from where a short chain stretches to the side. This is the Little Dipper asterism. It is quite small, so it seems that the stars in it are located close to each other. Although the distances between them are very large in space.
There are seven stars in total in the Small Bucket. Their names are Polaris (Alpha Ursae Minoris), Kochab (Beta Ursae Minoris), Pherkad (Gamma Ursae Minoris), Yildun (Delta Ursae Minoris), Eps UMi (Epsilon Ursae Minoris), Akhfa al Farkadain (Zeta Ursae Minoris) and Anwar al Farkadain (Eta Ursae Minoris).
4. What is interesting about Ursa Minor for radio astronomers?
Like the rest of the constellations, Ursa Minor is not only the seven brightest stars but also all objects in a certain area of the sky. And there are many of them that emit in different parts of the electromagnetic spectrum that are not visible to the human eye. Perhaps the most interesting is the neutron star 1RXS J141256.0+79220, or Calvera. The distance to it ranges from 625 to 1000 light-years. Therefore, it is one of the closest similar objects to us.
Calvera is interesting because it is not a pulsar. It is still very young: its age is only a few million years old. But it already has periodic radio signal changes. Over time, it will cool down and turn into an ordinary object of this type.
5. Which star of Ursa Minor is the closest to us?
As in all other constellations, the stars in Ursa Minor are at different distances from the observer. However, it is not difficult to answer the question of which one is closest to us. It is not Polar at all and not one of those that form a “dipper”.
The brown dwarf WISE 1506+7027 is so dim that it is simply impossible to see it with the naked eye or even with a sufficiently powerful telescope. The distance to it is only 11 light years. But it was only discovered for the first time in 2011 thanks to the WISE infrared sky survey.
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