Ghostly in appearance, Abell 39 [
http://www.noao.edu…] is a remarkably simple, spherical nebula about five light-years across. Well within our own Milky Way [
http://anzwers.org/…] galaxy, the cosmic sphere [
http://math.rice.ed…] is roughly 7,000 light-years distant toward the constellation Hercules. Abell 39 is a planetary nebula [
http://antwrp.gsfc.…], formed as a once sun-like star's outer atmosphere was expelled over a period of thousands of years. Still visible, the nebula's central star is evolving into a hot white dwarf. Although faint, the nebula's simple geometry has proven to be a boon [
http://www.noao.edu…] to astronomers [
http://adsabs.harva…nph-bib_query?bibcod e=2000AAS...197.0616 J ] exploring the chemical abundances and life cycles [
http://imagine.gsfc…stars.html ] of stars. In this deep image [
http://www.mistisof…Nebulae_pk47p42v1.ht m ] recorded under dark night skies, very distant background [
http://www.noao.edu…bggalaxies.html ] galaxies can be found -- some visible right through the nebula itself.
Explanation
Ghostly in appearance, Abell 39 [
http://www.noao.edu…] is a remarkably simple, spherical nebula about five light-years across. Well within our own Milky Way [
http://anzwers.org/…] galaxy, the cosmic sphere [
http://math.rice.ed…] is roughly 7,000 light-years distant toward the constellation Hercules. Abell 39 is a planetary nebula [
http://antwrp.gsfc.…], formed as a once sun-like star's outer atmosphere was expelled over a period of thousands of years. Still visible, the nebula's central star is evolving into a hot white dwarf. Although faint, the nebula's simple geometry has proven to be a boon [
http://www.noao.edu…] to astronomers [
http://adsabs.harva…nph-bib_query?bibcod e=2000AAS...197.0616 J ] exploring the chemical abundances and life cycles [
http://imagine.gsfc…stars.html ] of stars. In this deep image [
http://www.mistisof…Nebulae_pk47p42v1.ht m ] recorded under dark night skies, very distant background [
http://www.noao.edu…bggalaxies.html ] galaxies can be found -- some visible right through the nebula itself.
Explanation
