- 4160 - MOST DISTANT GALAXY ? Astronomers normally observe galaxies by observing light these objects emit, but some tricky galaxies require a different approach. Using the Hubble Space Telescope, a team of astronomers has used a tricky technique to discover an elusive 11-billion-year-old galaxy. Rather than observe the light this realm emits, they watched for the light it absorbs.
----------------------------- 4160 - MOST DISTANT GALAXY ?
- Just as we see a
light bulb via the light it emits, astronomers usually observe galaxies using
the light their stars emit. Galaxies put out light waves found across the
entire electromagnetic spectrum, and
different telescopes are able to observe these cosmic objects in
different wavelengths of light to form a full picture.
-
- But, when a galaxy
is located along the same line of sight as another, more distant, source of
bright light, there's another way to go about these galactic observations. As
light passes through a background galaxy toward a foreground galaxy gas and
dust in the foreground galaxy will absorb some of the background one's
wavelengths.
-
- Because chemical
elements absorb light at specific wavelengths, looking for gaps in the light
output, or spectra , from a background source can tell astronomers what that
light had passed through on its way to our telescopes. In other words, light in
those "gaps" would've been absorbed by a foreground object on the way
to our vantage point.
-
- One potentially
useful background source for this technique are quasars, which are extremely
bright galactic hearts powered by supermassive black holes blasting out jets of
radiation and matter as they feast on surrounding material.
-
- To find absorbing
galaxies, we first look for quasars that are particularly red. Because star dust tends to absorb the blue
light but not the red, if there is a dusty galaxy in the foreground, the quasar
will be reddened.
-
- Astronomers have
spotted several absorbing galaxies by parsing light from reddened quasars, but
once this is done, they are faced with a much more challenging task: hunting
for light emitted by the absorbing
galaxy itself.
-
- Looking for a firefly on a cosmic lighthouse? When situated exactly behind a galaxy,
quasars tend to disrupt our view of foreground galaxies because they are so
immensely bright. So much so that they essentially overwhelm the combined light
of every star in an entire galaxy.
-
- Unfortunately, the
scientists haven’t yet identified the light coming from their recently-uncovered, 11-billion-year-old
absorbing galaxy, but the absorption patterns this object has revealed are
remarkable. The galaxy, seen as it was when our 13.8 billion-year-old universe
was only around 3 billion years old, is absorbing more light than other
galaxies found in a similar fashion, meaning it is likely a more mature galaxy
such as the Milky Way.
-
- The features
missing in the light tell us something about the dust in the foreground
galaxy. The dust seems to resemble the
dust that we see locally in the Milky Way and one of our neighboring galaxies.
-
- Astronomers were
able to determine that the galaxy has a bright counterpart. That galaxy, which
seems to be birthing stars at an intense rate, is so close to the absorber
galaxy that the two are probably gravitationally bound. This means at some
point after they were noticed the two galaxies likely formed a galaxy group
similar to the local group in which the Milky Way sits.
-
-
September 18, 2023 MOST DISTANT
GALAXY ? 4160
------------------------------------------------------------------------------------------
-------- Comments
appreciated and Pass it on to whomever is interested. ---
--- Some reviews are
at: -------------- http://jdetrick.blogspot.com -----
-- email feedback,
corrections, request for copies or Index of all reviews
--- to: ------
jamesdetrick@comcast.net
------ “Jim Detrick” -----------
--------------------- ---
Tuesday, September 19, 2023 ---------------------------------
No comments:
Post a Comment