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Nearby Black Hole Has Two Companion Stars Visible with the Naked Eye

Posted by Guy Pirro 05/14/2020 01:58AM

Nearby Black Hole Has Two Companion Stars Visible with the Naked Eye

A team of astronomers from the European Southern Observatory (ESO) and other institutes have discovered a black hole lying just 1000 lightyears from Earth. The black hole is closer to our Solar System than any other found to date and forms part of a triple system that can be seen with the naked eye. The team found evidence for the invisible object by tracking its two companion stars using a telescope at ESO’s La Silla Observatory in Chile. The astronomers say this system could just be the tip of the iceberg, as many more similar black holes could be found in the future.


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Hello Guy! At a distance of 1000 light years, am I correct to assume that the orbit of the inner star in this triple object system falls within the diffraction disk of the inner star and thus its motion would be visibly imperceptible to us? No mention was made of the orbital period of the outer star, but does anyone know the orbital period of that star? Jon H.

Jon:

Thanks for the question. I'll try to answer it.

Let's discuss each of the objects separately -- The black hole at the center, the inner orbiting star, and the outer orbiting star.

When you ask about the airy disk of the "inner star," I assume you are referring to the "inner orbiting star" since the black hole at the center (which emits no light) does not create an airy disk.

If that is the case, then an observer on Earth would see this inner orbiting star (along with its airy disk) oscillate back and forth with a period of 40 days. The instrumentation at the observatory is apparently sensitive enough to measure that oscillating motion.

Regarding the outer orbiting star, I was not able to find the its orbital period.

BTW - The HR 6819 triple system is in the constellation Telescopium, so it is not viewable from the northern hemisphere. However, the two orbiting stars in HR 6819 can be viewed from the southern hemisphere on a dark, clear night without binoculars or a telescope.

Hope this helps.

Thanks,

Guy Pirro

Well... Thanks Guy...!!!!
Frank

Welcome to Astromart Frank!

Guy Pirro