Stars are a fascinating subject. They are not only beautiful but they have given us the possibility of how huge and mysterious the whole universe is. Since a very early age, they have attracted the attention of scientists, poets, philosophers and some occults.
I hope you must have heard the nursery rhyme “Twinkle twinkle little stars”. And I bet you must have started to sing it in your head.
While you finish humming the tune, let me tell you something interesting about the stars that you might have never heard before.
Hyper velocity star
They do sound cool, and once you will get to know what it is, you will realise that it justifies its name.
A high-velocity star is a star moving faster than 65 km/s to 100 km/s relative to the average motion of the stars in the Sun’s neighbourhood.
There are three basic categories of hyper velocity stars.
- Runaway stars
- Halo stars
- Hypervelocity stars
The velocity is also sometimes defined as supersonic relative to the surrounding interstellar medium.
1. Runaway Stars
Definition: These are the stars that ran away from their respective homes in search of a better life for themselves.
As the name suggests, it is a star that moves through space with an abnormally high velocity relative to the surrounding interstellar medium.
Possible causes are
- a close encounter between two binary systems may result in the disruption of both systems, with some of the stars being ejected at high velocities
- a supernova explosion in a multiple star system can result in the remaining components moving away at high speed.
Examples: AE Aurigae, 53 Arietis and Mu Columbae, all of which are moving away from each other at velocities of over 100 km/s
2. Halo stars
Definition: Halo Stars were formed before supernova explosions had scattered a large amount of heavy elements into the galaxy.
The brightest halo members are iron-poor globular star clusters, spectacular objects that can pack hundreds of thousands of old stars into a sphere just a few dozen light-years across.
I was shocked to know the Halo Stars got nothing to do with the Halo game series.
Example: Halo stars passing through the disk of the Milky Way at steep angles.
Kapteyn’s star is a popular example of Halo star and it lies near the Sun.
3. Hypervelocity stars
Definition: are stars with velocities that are substantially different from that expected for a star belonging to the normal distribution of stars in a galaxy.
Such stars may have velocities so great that they exceed the escape velocity of the galaxy.
Example: It is believed there are thousands of hypervelocity stars.
Till now, 16 Hypervelocity Stars have been believed to have been found. The nearest Hypervelocity star is 19 kpc from the Sun.