Posted on by Carolyn Collins Petersen

Dwarf Galaxies Found Without Influence From Dark Matter

Dwarf galaxy in Fornax.
The dwarf galaxy NGC1427A flies through the Fornax galaxy cluster and undergoes disturbances which would not be possible if this galaxy were surrounded by a heavy and extended dark matter halo, as required by standard cosmology. Courtesy ESO.

Ask astronomers about dark matter and one of the things they talk about is that this invisible, mysterious “stuff” permeates the universe. In particular, it exists in halos surrounding most galaxies. The mass of the halo exerts a strong gravitational influence on the galaxy itself, as well as on others in the neighborhood. That’s pretty much the standard view of dark matter and its influence on galaxies. However, there are problems with the idea of those halos. Apparently, some oddly shaped dwarf galaxies exist that look like they have no halos. How could this be? Do they represent an observationally induced challenge to the prevailing ideas about dark matter halos?

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Posted on by Tammy Plotner

The Constellation Fornax

Welcome to another edition of Constellation Friday! Today, in honor of the late and great Tammy Plotner, we take a look at “the Furnace” – the Fornax constellation. Enjoy!

In the 2nd century CE, Greek-Egyptian astronomer Claudius Ptolemaeus (aka. Ptolemy) compiled a list of the then-known 48 constellations. This treatise, known as the Almagest, would be used by medieval European and Islamic scholars for over a thousand years to come, effectively becoming astrological and astronomical canon until the early Modern Age. This list has since come to be expanded to include the 88 constellation that are recognized by the International Astronomical Union (IAU) today.

Among the updated list is the constellations Fornax, a relatively obscure constellation in the southern sky that is noted for the many bright galaxies it is associated with (the Fornax Cluster). This constellation was added French astronomer Nicolas Louis de Lacaille in the mid-18th century and is therefore part of the Lacaille family, which includes with Antlia, Caelum, Circinus, Horologium, Mensa, Microscopium, Norma, Octans, Pictor, Reticulum, Sculptor, and Telescopium.

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