- 4176 - EINSTEIN CROSS - exhibits gravitational lensing? Astronomers find a rare “Einstein Cross”. Gravitational lensing is one of astronomy’s great wonders. It is a natural lens that magnifies the distant universe. Sometimes a lensing system takes the shape of a so-called “Einstein Cross”.
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4176 - EINSTEIN
CROSS - exhibits gravitational lensing?
-
- Astronomers find a
rare “Einstein Cross”. Gravitational
lensing is one of astronomy’s great wonders.
It is a natural lens that magnifies the distant universe. Sometimes a
lensing system takes the shape of a so-called “Einstein Cross”.
-
- Astronomers found a
new Einstein Cross using the Dark Energy Spectroscopic Instrument mounted on a
telescope at Kitt Peak National Observatory. This instrument is surveying the
sky and has found many instances of “gravitational lensing”.
-
- The lens system,
“DESI-253.2534+26.8843”, is actually a massive foreground elliptical galaxy
surrounded by four blue images of a background galaxy. The four images that
display consistent spectral features tell the astronomers that the source is a
single galaxy, which allowed them to confirm the lens system.
-
- The cross pattern
tells them about the mass distribution of the lens galaxy. Elongated mass
distributions result in Einstein crosses, and a spherical mass distribution
would result in an “Einstein ring.”
-
- The main galaxy
doing the lensing lies about 5.998 billion light-years away. The distant galaxy
that it’s lensing is more than 11.179 billion light-years away. The foreground
lensing galaxy is giving an amazing look at a galaxy in the early Universe.
-
- They determined
the distance to the more distant galaxy by doing a spectral analysis of the
light in each image. Based on color information contained in the DESI Legacy
Survey, the lensing galaxy is in a galaxy group. They found at least seven
other members of the same group.
-
- MUSE is a powerful
spectroscopic instrument that can cover wide areas of the sky in visible light
wavelengths. It dissects the light into its component wavelengths (creating
spectra) and each pixel in the image from the integral field unit contains a
spectrum.
-
- When a massive
galaxy sits directly “in front of” a more distant background object (such as a
galaxy or a quasar) the distribution of matter around that galaxy and its
gravitational effect can “bend” the light from the object as it passes by. That
results in lensed images (or a ring).
-
- The first
“Einstein Cross” was a surprise. Astronomer John Huchra and his team actually
discovered it in 1985. It’s called “Huchra’s Lens”. It really looked baffling
to the observers, as if there were four identical quasars around the center
(where there was a faint image of the quasar). . Eventually, the redshift of
the light from the quasar revealed that it lay 8 billion light-years away. The
lensing galaxy is only about 400 million light-years distant.
-
- Einstein Crosses
and beyond are these so rare? It turns out that gravitational lensing happens
everywhere in the universe, mostly in the form of so-called “weak lensing”.
Creating an Einstein Cross requires a precise alignment of the lensing body and
light source and astronomers refer to this as “strong gravitational lensing”.
-
- After the
discovery of Huchra’s Lens, astronomers found a few more using Hubble Space
Telescope and other instruments. Then, in 2021, the Gaia satellite found a
dozen more. And, astronomers predict that more will be found as more powerful
instruments and techniques perform surveys like Gaia’s.
-
- More lenses like
these will extend astronomy’s view to earlier epochs. They could perform as
excellent probes of the dark matter distribution in the different epochs of
cosmic time. And, there are other applications to be developed.
-
- One of our goals
is to do a targeted search for supernovae in hundreds of gravitational lens
systems, which will allow us to directly measure Hubble’s constant by observing
the time delay of supernova light curves between the lensed images of a
supernova.
-
-
October 3, 2023 EINSTEIN CROSS
- gravitational lensing?
4176
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