This comparison of two images shows puffing dust bubbles and an erupting
gas shell – the final acts of a monster star’s life. You can explore the detail
of the nebula surrounding the star AG Carinae by using the slider tool on the
image above.
These new views showcase the dual nature of the star AG Carinae, which was
the target of the NASA/ESA Hubble Space Telescope’s 31st anniversary image in April 2021.
This new perspective is the result of Hubble’s observations of the star in 2020
and 2014, along with others captured by the telescope’s Wide Field Planetary
Camera 2 in 1994.
The first image showcases details of ionized hydrogen and nitrogen
emissions from the expanding shell of the nebula (seen here in red). In the
second image, the color blue delineates the distribution of dust that shines in
reflected star light. Astronomers think powerful stellar winds coming off of
the star formed and shaped the dust bubbles and filaments. The nebula is about
five light-years wide, similar to the distance from here to the nearest
star beyond the Sun, Proxima Centauri.
AG Carinae is formally classified as a Luminous Blue Variable because it is
a hot (emitting blue light), brilliant star that varies in brightness. Such
stars are quite rare because few are so massive. Luminous Blue Variable stars
continuously lose mass in the final stages of life. The star is waging a tug-of-war
between gravity and radiation pressure to avoid self-destruction. As the star
begins to run out of fuel, its radiation pressure decreases, and gravity begins
to take hold. Stellar material succumbs to gravity and falls inward. It heats
up and is explosively ejected into the surrounding interstellar space. This
process continues until enough mass is lost and the star reaches a stable
state.
The spectacular nebula surrounding AG Carinae formed by material ejected
from the star during several of its past outbursts. The nebula is approximately
10,000 years old, and the observed velocity of the gas is approximately 43
miles per second. While this nebula looks like a ring, it is in fact a hollow
shell whose center was cleared of gas and dust by a powerful stellar wind
travelling roughly 124 miles per second. The gas (composed mostly of ionized
hydrogen and nitrogen) in these images appears as a thick bright red ring,
which appears doubled in places – possibly the result of several outbursts
colliding into each other. The dust, seen here in blue, formed in clumps,
bubbles, and filaments and was shaped by the stellar wind.
Scientists who observed the star and its surrounding nebula note that the
ring is not perfectly spherical. It appears to have bipolar symmetry. This
could mean the mechanism producing the outburst may be the result of a disk in
the center, or the star may have a companion (known as a binary star). An
alternative and simpler theory is that, like many massive stars, AG Carinae may
rotate very fast.
Text credit: European Space Agency (ESA)
Image credit: ESA/Hubble and NASA, A. Nota, C. Britt
Source: https://www.nasa.gov/feature/goddard/2021/hubble-takes-a-closer-look-at-its-31st-anniversary-image
No comments:
Post a Comment