Near-Perfect Einstein Ring Discovered

Fraser Cain writes "Universe Today is reporting on the discovery of a nearly perfect Einstein Ring; a gravitational lens of a nearby galaxy working as a natural telescope to focus the light from a more distant galaxy. Gravitational lenses have been seen many times before, but never so complete, with a close lensing galaxy and a distant magnified galaxy."

Comments

Get the paper here

[Anonymous Coward]

The paper.

Re:What?

[mobby_6kl]

Here's what Hawking himself writes:

The term black hole is of very recent origin. It was coined in 1969 by the American scientist John Wheeler as a graphic
description of an idea that goes back at least two hundred years, to a time when there were two theories about light:
one, which Newton favored, was that it was composed of particles; the other was that it was made of waves.
[...]
John Michell, wrote a paper in 1783 in the Philosophical Transactions of the Royal Society of London in which he pointed out that a star that was sufficiently massive and compact would have such a strong gravitational field that light could not escape: any light emitted from the surface of the star would be dragged back by the star's gravitational attraction before it could get very far.

Stephen Hawking - A Brief History of Time, Chapter 6: Black Holes.

A better ring, and references on lensing

[StupendousMan]

The summary states incorrectly:

Gravitational lenses have been seen many times before, but never so complete ...

Way back in 1989, radio astronomers found a gravitational lens near the galaxy MG1643+1346 which creates two images, one of which is a nearly complete circular ring. Take a look at this radio image from Langston et al., AJ 97, 1283 (1989):

Click to see radio image of lensed quasar.

So, this newest system is a pretty good lens, but not the "most complete" one yet found.

By the way, if you want to understand how gravitational lensing works, you can read some lectures I wrote for an introductory astronomy class:

• Basic theory of lensing
• Microlensing (lensing by a single star)

Re:Visible?

[Anonymous Coward]

It's not visible to an amateur scope; it's magnitude 22.2, and I don't think the largest amateur scopes can get past 17 or so. That translates to about 100 times too dim to be seen by them. The value I quoted is the R_c band, which is visible (around 650 nm), if I'm reading the paper correctly. You can read all this yourself in the paper; see the bottom of section 1 on page 2, and Figure 2.