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:IF we can see them better...

[imsabbel]

Come on, insightful? For a fortune cookie slogan?

And no, they cant see us better, because the light from our direction that is visible in the target galaxy is from a time where out sun didnt exist.

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.

Re:It can't be long now that we discovered the Vor

[GotenXiao]

Uh, if you're referring to the Vogons from H2G2, see previous spelling.

Re:IF we can see them better...

[omega_cubed]

That is NOT true. Ever picked up a telescope? Just because you can see that bird 500 yards away nesting on its little twig doesn't mean that it can see you just as well.

Which telescope will you install them in?

[hpulley]

The James Webb telescope is not even on the drawing board yet and will not work in visual wavelengths so any spare HST hardware would only be useful if it were designed for IR. What space telescope are you going to launch by 2008 when the HST will fail? The JWST isn't going up until around 2015 (originally expected to launch in 2011 but now very unlikely). Do we want to go 3-7 years without a good space telescope? I know of no other plans for a telescope to go up using those HST parts. By the time you design one, build it and launch it I'm not sure it will have been worth it. Expensive or not, fixing the HST with astronauts and the space shuttle is the fastest (and probably the only real) solution to keeping a space telescope working continuously in the near future.

Fun with Google

[Anonymous Coward]

"Einstein's lens" is caused by the fact that gravity attracts light.

You can use Google to calculate how much weight each photon has.

First, we start by deciding the frequency of the light. Let's say it's red light:

500 THz

Next, we compute the energy of each photon by using the equation E=hf :

h * 500 THz

Next, we compute the mass of each photon by using the equation m=E/c^2 :

h * 500 THz / (c^2)

Finally, we compute the weight of the photon (on the Earth's surface) by using the equation F=mg, where g is 9.8 N/kg:

h * 500 THz / (c^2) * (9.8 N/kg)

Typing this into Google, we find that each photon of red light weighs 3.6*10^-35 N.

For comparison, an electron weighs

(9*10^-31 kg) * (9.8 N/kg) = 8.8*10^-30 N.

Re:Fun with Google -- Incorrect

[Baudelaire76]

Weight, which is a Newtonian concept, is not really applicable to an inherently relativistic particle such as the photon. In addition, the effect of gravity on a photon is actually about twice as large as you would expect from Newtonian gravitation. This comes from the weak-field limit of general relativity, and was one of the first tests of the theory. In 1919, Sir Arthur Eddington observed the bending of starlight around the sun during a solar eclipse, and showed that the bending was, lo and behold, about twice as large as the Newtonian prediction, and consistent with general relativity.