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Comment by mangix | Hacker News Reader

Article says finds black hole.

There has never been direct observational evidence for one.

Hmmmmm...

If you want to be pedantic, you cannot observe direct evidence of anything. After all, when you look at your hand you don't see the hand itself, just the photons that happened to interact with it a short moment ago. Actually you don't see those photons, you only perceive how those photons interact with the cells in your eyes.

Evidence for black holes has been shown in the way they bend light from distant galaxies and cause stars to orbit around them. There's not much stronger evidence needed to prove their existence.

That’s...an interesting way of looking at it.

A black hole is made up of an infinitely dense point-mass singularity and an event horizon. Nobody has every found either. So nobody has found a black hole.

What's your alternative theory for this object?

This is astronomy, we have only photons or the lack thereof and our interpretations of these photons and their lack. We haven't even sent a probe yet to the surface of the Sun (we have gotten eleven million miles away). So, by "direct observation" standards, we don't even know the Sun exists.

For your standard, we would need to send ships to each star, including the event horizon of a black hole. These aren't standards we can do anything with.

They're already playing definition games at the second reply. Don't feed the troll.

Yes, that's what the article says. The research paper says:

"Several dozen optical echelle spectra demonstrate that HR 6819 is a hierarchical triple. A classical Be star is in a wide orbit with an unconstrained period around an inner 40 d binary consisting of a B3 III star and an unseen companion in a circular orbit. The radial-velocity semi-amplitude of 61.3 km/s of the inner star and its minimum (probable) mass of 5.0 M (6.3 ± 0.7 M ) imply a mass of the unseen object of ≥ 4.2 M (≥ 5.0 ± 0.4 M ), that is, a black hole (BH)."

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