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Sunday, August 2, 2015

Eridanus and Fornax

Constellation map of Eridanus and Fornax. Click to see the image's original size.
Click on the constellation map above to enlarge it in a lightbox window.

ERIDANUS the River and FORNAX the Furnace have completely different sizes - Eridanus being large and Fornax being small. In the celestial latitude system, Eridanus stretches from -5° to almost -60° while Fornax straddles the 30° mark. Both constellations share the fact that they are not truly Northern Hemisphere constellations, given that they are below the celestial equator. In the Earth's Northern Hemisphere, Eridanus' northern section can be mainly found during the winter season near the bright Orion constellation, located to the left of northern Eridanus. Caelum, Columba, Dorado, Horologium, and Lepus are other constellations to the left of Eridanus. Cetus and Phoenix are right of Eridanus and Sculptor is right of Fornax.

Countless Cosmic Wonders, Mostly Galaxies
The minuscule (or miniscule, whichever spelling you prefer!) Fornax - in regards to its official borders set by astronomers - actually has many more prominent and bright galaxies than Eridanus does. Fortunately for The River constellation, it has an amazing assortment of galaxies, many of which are not shown on the map above. First, the Fornax Cluster of galaxies in Fornax's western region is very close to Eridanus. Second, Eridanus has two main galaxy groupings called the Eridanus Group and Eridanus Cluster, both of which are north of Fornax's cluster. While these galaxies are not as bright as Fornax's, there are about 400 total galaxies in these two groups! Eridanus' NGC 1232 is a spectacular spiral galaxy in the Eridanus Cluster, while NGC 1291 south of Fornax is an interesting ring galaxy.

While someone could talk all day about the galaxies of Eridanus and Fornax, there are also planetary nebulae to talk about! Fornax has NGC 1360, a planetary nebulae nicknamed Robin's Egg Nebula. This image © Adam Block and The Planetary Society (link opens in new window) easily shows why the beautifully blue nebula has its nickname. NGC 1535 (University of Arizona Science Center image) left of Zaurak (Gamma Eridani, γ) in northern Eridanus was discovered by William Herschel.

Brightest Star: Achernar (end of the river), Alpha Eridani (α); 0.45 apparent magnitude
Binary Stars: Acamar (Theta Eridani, θ) and Tau 4 Eridani (τ^4)
Galaxies: NGC 1179, 1187, 1232, 1291, 1300, 1332, 1395, 1407, 1532, 1723, and many more
Planetary Nebula: NGC 1535

Brightest Star: Alpha Fornacis (α); 3.82 apparent magnitude
Binary Stars: Alpha Fornacis (α) and Beta Fornacis (β)
Galaxies: Fornax Dwarf Galaxy, NGC 1201, 1255, 1371, 1385, 1398, and more
          Fornax Cluster galaxies: NGC 1316, 1380, 1344, 1399, 1425, and more
Planetary Nebula: Robin's Egg Nebula (NGC 1960)

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Blog Background

The background has three Hubble Space Telescope images, which are accessible at this Hubble webpage:

— LH 95 is a star-forming region in the Large Magellanic Cloud, Dorado constellation.

— Ant Nebula (also called Menzel 3) is an aptly-named planetary nebula located in the constellation Norma.
— Egg Nebula (also called CL 2688) is a protoplanetary nebula in the constellation Cygnus.

HubbleSite Image Links: LH 95, Ant Nebula, and Egg Nebula