New answers tagged

5

As the article you reference makes clear, the defocusing is deliberate. It spreads the light of bright stars (the main targets for CHEOPS) over more pixels and hence mitigates saturation and non-linearity problems in the detectors. The first light images look quite similar to simulated pre-flight images (e.g. Hoyer et al. 2018), so I don't think there are ...


1

To add to Steve Linton's correct answer, there is actually a specific example of observing one of the Alpha Centauri system stars as a gravitational lens. Lensing of background stars by Proxima Centauri was predicted to occur in October 2014 and February 2016 by Sahu et al. (2014). Zurlo et al. (2018) observed the astrometric shift caused by the 2016 event ...


3

Being closer to the focal point is better because it allows more relative movement. You don't have to be right on top of the focal point, but closer is better. Alpha Centauri is very far away. The focal point is decreased proportional to the mass/radius squared, so, the Sun, about 1000 times the mass of Jupiter and about 10 times the radius, it's focal ...


7

Gravitational lensing works from anywhere beyond the focus, so in that sense, we could use any star as a gravitational lens. The problem is that the field of view is tiny. We only get any useful information from alpha centauri as a gravitational lens if the target object is almost exactly behind alpha centauri from our point of view. To look in a slightly ...


2

The focal point of the Gravitational lens of Alpha Centauri is a few hundred AU from the star. But Alpha Centauri is 270000 AU from the solar system. The Sun's gravitational focus is much nearer.


4

Black holes are black. They are only observed directly by telescopes if they are accreting matter. Any radiation observed comes from the matter surrounding the black hole. Generally speaking, the smaller the black hole, the hotter the accreted material becomes. For something of planetary mass, one might expect X-rays and Gamma rays from accreting material. ...


Top 50 recent answers are included