- 4001
- STAR -
devouring a planet? The star
devouring a planet 12,000 light-years away may presage what happens to Earth
about 4 billion years from now.
-------------------------- 4001 - STAR - devouring a planet?
- Astronomers may have for the firt time
witnessed a sun-like star devouring a planet, shedding light on the fate that
will befall Earth in about four billion years when our dying sun swells to
engulf our world.
-
- By analyzing countless stars during various
stages of their evolution, astronomers have discovered that as our sun and
stars like it near the ends of their lives, they begin to exhaust their primary
source of fuel, the hydrogen near their cores.
-
- This leads their cores to contract and their
outer shells to expand and cool. During this "red giant" phase, these
stars may billow out anywhere from 100 to 1,000 times their original diameter,
swallowing closely orbiting planets.
-
- We know that this must happen to all
planets that are orbiting at distances smaller than that of the Earth. For decades, scientists have detected
evidence of stars just before and shortly after the act of consuming planets.
However, researchers had never caught a star in the act until now.
-
- Planetary engulfment has been a fundamental
prediction in our understanding of stars and planets, but their frequency have
been very uncertain. This breakthrough
came after examining a burst of radiation dubbed “ZTF SLRN-2020”, which took
place in the Milky Way's disk about 12,000 light-years away, near the
constellation Aquila. During the event, a star brightened by a factor of 100
over the course of a week.
-
- Novas are stellar explosions that can
happen when a red giant pours fuel onto a companion white dwarf star. The Zwicky Transient Facility scans the sky
for stars that rapidly change in brightness, which could be events such as
novas.
-
- Astronomers analyzed the spectrum of light
from this bright outburst. Unlike a
nova, which has hot gas around it, this source was primarily surrounded by cool
gas.
-
- Cool gas from such bursts often results
from merging stars. By looking at data
from the same star collected by the Keck Observatory in Hawaii, they found
molecules that can only exist at very cold temperatures. Cold gas can condense to form dust over time.
-
- About a year after the initial discovery,
stronomers analyzed data from the same star, this time collected using an
infrared camera at the Palomar Observatory. Infrared data can yield signals of
colder material, in contrast to bright visible light signals that often come
from novas and other powerful events.
-
- The scientists found the brief outburst of
visible light from the star was accompanied by extraordinarily bright
near-infrared light signals that slowly faded over the course of six months.
This confirmed the suspicion that this source had indeed formed a lot of dust.
-
- The final piece of the puzzle came when the
researchers examined data collected by NASA's infrared space telescope,
“NEOWISE”. This suggested the total amount of energy the star released since
its initial outburst was surprisingly small, about a thousandth the magnitude
of any stellar merger observed in the past.
-
- That means that whatever merged with the
star has to be 1,000 times smaller than any other star we've seen. And it's a happy coincidence that the mass of
Jupiter is about one-thousandth the mass of the sun. This was a planet,
crashing into its star.
-
- Based on the nature of the outburst, the
astronomers estimated the event released hydrogen equal to about 33 times the
Earth's mass, as well as about 0.33 Earth-masses of dust. This suggests the progenitor star was about
0.8 to 1.5 times the mass of our sun and the engulfed planet was about 1 to 10
times the mass of Jupiter.
-
- Earth is expected to meet a similar fate
when the sun becomes a red giant in about 5 billion years.
-
- There are many questions this discovery
raises. "Did the planet survive the plunge, or did it get annihilated into
the stellar material during the plunge?"
"Did the planet come into contact with the stellar surface because
of the star's natural expansion, or did something give it an ever-so-slight
push to go close to the star? All these questions will become clear as we get
more data on this object and find more events in the future.
-
- Now that
scientists know what planetary engulfment likely looks like, they can look for
similar events in the future, especially as infrared surveys become
increasingly common in the next decade.
-
May 14, 2023 4001
----------------------------------------------------------------------------------------
----- 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” -----------
--------------------- --- Sunday, May 14, 2023
---------------------------------
-
No comments:
Post a Comment