Green Light Unveils Presence of an Old and Metal-Poor Halo in a Giant Elliptical Galaxy

by | Oct 9, 2020 | Uncategorized | 0 comments

Green Light Unveils Presence of an Old and Metal-Poor Halo in a Giant Elliptical Galaxy
Probing a glowing bubble of gas and dust encircling a dying star, the NASA/ESA Hubble Space Telescope reveals a wealth of previously unseen structures. The object, called NGC 2371, is a planetary nebula, the glowing remains of a Sun-like star. The remnant star visible at the centre of NGC 2371 is the super-hot core of the former red giant, now stripped of its outer layers. Its surface temperature is a scorching 240,000 degrees Fahrenheit. NGC 2371 lies about 4,300 light-years away in the constellation Gemini. CREDIT: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Many things in the universe are hard to see without massive telescopes. When we look at star clusters, we try to understand them by looking at the most massive and easily seen stars. 

It turns out bright stars aren’t the only tools we have to understand what’s going on. In a new study of the elliptical galaxy M105, researchers carefully mapped the population of objects – stars and planetary nebulae – and found that the planetary nebulae traced a diffuse population of metal-poor stars in the outer halo of the galaxy. While the majority of the star’s material lies within three kiloparsecs (kpc) of the galaxy center, this halo spans from 15-50 kpc. This large halo only produces about 4% of M105’s light, but its large size means the motions of these stars and planetary nebulae can be used to trace the effects of dark matter.

M105 is located in the Leo I galaxy group, which is just ten megaparsecs away and is the closest group to have all the major kinds of galaxies. This research hints at how planetary nebulae can be used as tracers of metal-poor populations in other galaxies.

More Information

Isaac Newton Group of Telescopes (ING) press release 

The Halo of M105 and Its Group Environment as Traced by Planetary Nebula Populations: I. Wide-field Photometric Survey of Planetary Nebulae in the Leo I Group,” J. Hartke et al., 2020, Astronomy & Astrophysics (preprint on


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