Celestial hemisphere:  Northern  ·  Constellation: Cetus (Cet)  ·  Contains:  IC 1613
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IC 1613 - An Irregular Dwarf Galaxy, Alex Woronow

IC 1613 - An Irregular Dwarf Galaxy

Getting plate-solving status, please wait...
IC 1613 - An Irregular Dwarf Galaxy, Alex Woronow

IC 1613 - An Irregular Dwarf Galaxy

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Description

IC 1613

OTA: RCOS (14.5” f/8)

Camera: SBIG STX16803

Observatory: Deep Sky West, NM

EXPOSURES:

Red: 16 x 900 seconds

Blue: 12 x 900

Green: 13 x 900

Lum: 8 x 900

Total exposure ~18 hours

Image Width: ~1/2 deg

Processed by Alex Woronow (2019) using PixInsight, Skylum, SWT

Our ‘Local Group’ of galaxies includes the irregular dwarf galaxy, IC 1613. IC 1613 is moving toward the Milky Way at 234km/s, from a distance of about 2.4M light-years. IC 1613 played an important role in historic developments surrounding the distance-measurement to deep-sky objects.

Measuring distances has a history worthy of study. Driving the need to measure distances, in addition to pure intellectual curiosity, was loud debate about the distances to “nebula,” a term that, in the past, usually included galaxies as well as dust clouds. Some maintained they all resided within our own galaxy (and even that the Milky Way was a unique feature in the Universe); others wanted at least some nebulae to lie beyond. Clearly, a “yardstick” was needed!

That yardstick, or one of them, was the relationship between the absolute brightness of Cepheid variables and their periods of brightness variation. It happens that these two variables are related! So, once the functional relationship became known, an astronomer could identify a Cepheid variable in a distant nebula (i.e., galaxy), measure its period, know how bright it would appear as a function of its distance, and know the nebula’s distance! However, a fly in the ointment is intervening interstellar dust. Intervening dust would make a Cepheid appear dimmer than it should appear and, therefore, appear more distant than it really is. So, those who wanted other galaxies to lie within our own, might, with some justification, claim that a measured distance was inaccurately large, and if it were corrected for intervening dust, the Cepheid-bearing nebula would, in fact, be within our galaxy!

Well, along comes IC 1613. IC 1613 has very little dust and it has some Cepheids. So, if the Cepheids in that galaxy place IC 1613 beyond the Milky Way, it is a hard task to overturn that finding. And so, here we are, just one more galaxy in a universe of billions--not all that special after all.

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    IC 1613 - An Irregular Dwarf Galaxy, Alex Woronow
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  • IC 1613 - An Irregular Dwarf Galaxy, Alex Woronow
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Description: Annotated with DSOs from the HyperLeda data base. I used an Excel spreadsheet that I wrote to extract the data from a download and to format it for PixInsight's "AnnotateImage" script. The spreadsheet is available here:
https://groups.io/g/Astro-ImagersSidebar/topic/image_annotation_from/68690699?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,68690699

(feel free to join that group too!)

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IC 1613 - An Irregular Dwarf Galaxy, Alex Woronow