The Owl Nebula stares at us from near the Big Dipper, in Ursa Major, the great bear. It is the death mask of a star. Nuclear reactions have ceased in the star's core, and the star's outer layers are blowing into space. The layers of gas are energized by ultraviolet radiation from the dying core, which will form a white dwarf. The contours of the surrounding gas show two relatively empty regions, which form the owl's dark "eyes." The glowing gas will continue to expand into space, eventually growing so thin that it will no longer shine. Estimates of the distance to the nebula, which is also known as Messier 97, vary widely, from about 1,000 to 3,000 light-years. [Calar Alto Observatory/Vicent Peris/José Luis Lamadrid/Jack Harvey/Steve Mazlin/Juan Fabregat/Gilles Bergond]
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An owl stares at us from the Big Dipper — the death mask of a star. It consists of several concentric “bubbles” of gas blown into space by the dying star. It’s nice and round, and seen through a large telescope or in photographs, it has two dark patches that look like the eyes of an owl.
Astronomers have been keeping an eye on the Owl Nebula since it was discovered more than two centuries ago. Yet quite a bit about the nebula is still poorly understood. That includes its distance. Estimates published in the last decade and a half range from about a thousand light-years to about three thousand. Without knowing its distance, you can’t pin down its size, either. And without knowing its size, you can’t tell just when the nebula began to form.
One of the most extensive studies of the Owl says it began forming about 8,000 years ago as seen from Earth.
Because of changes in the nuclear reactions in the star’s core, it had puffed up to gigantic proportions. As those reactions began to shut down, gas at the surface flowed out into space, forming a faint “halo.” Later, much more gas flowed outward, forming the nebula’s outer shell. And later still, a faster wind began blowing, forming the inner shell. A cavity inside that shell contains less material, so it forms the eyes — the visage of a celestial owl.
And the Owl Nebula is near the top right corner of the Big Dipper’s bowl as darkness falls right now — the beautiful death mask of a star.
Script by Damond Benningfield