NGC 4038 and NGC 4039, the Antennae Galaxies!

Updated: Aug 1, 2022

Image Credit: NASA/ESA Hubble Space Telescope/ Alexandra Nachman. Image processed using FITS Liberator and Photoshop CC.

Quick Stats

Name: NGC 4038/NGC 4039/ or Caldwell 60/Caldwell 61
Nickname: Antennae Galaxies
Distance: 45-65 million light-years
Constellation: Corvus (Southern Celestial Hemisphere)

The Antennae Galaxies are a stunning example of what happens when galaxies collide! This pair of interacting galaxies are formally known as NGC 4038 and NGC 4039. They also go by the name Caldwell 60 and Caldwell 61. NGC 4038 is the galaxy on the top and NGC 4039 is the galaxy on the bottom. You can tell where each galaxy is located based on its core — the bright yellow spheres near the top and bottom of this shrimp-shaped galaxy are the cores of each galaxy. While there are two distinct cores now, when these galaxies are done merging, there will be only one core. The galaxies will most likely merge into a single elliptical galaxy, which is a galaxy that is nearly featureless and usually has an oval shape. They often look like bright, shining ovals of light!

This galaxy pair is located about 45-65 million light-years away in the constellation Corvus in the Southern Celestial Hemisphere. It is a beautiful example of merging galaxies and the wonderful new shapes they create! Merging gas-rich galaxies trigger an infusion of energy from galactic tidal forces and go through a voracious star-forming phase that will quickly eat up all the gas. This is known as a starburst phase, where new stars form faster than they would in a galaxy like our own. Thus, the galaxies have a very high rate of new stars being created. This is shown in the bright blue areas near the top of this image.

While the Hubble image above shows a beautiful picture of the galaxies, it is not the full image. Below, the reason for the nickname becomes clear. The two galaxies have long tails trailing from them that look like the antennae that bugs have! The tails of these galaxies began developing about 200-300 million years ago. That is when tidal forces began ejecting stars, gas, and more out of the galaxies and into the long, trailing tails we see today.

Image Credit: NOAO/AURA/NSF, B. Twardy, B. Twardy, and A. Block (NOAO)

These two galaxies were their own separate galaxies around 1.2 billion years ago. NGC 4038 was a barred spiral galaxy and NGC 4039 was a spiral galaxy. Then about 900 million years ago, they began approaching each other. The merger began about 500-600 million years ago. And while the word collide is often used, these galaxies aren’t actually smashing into each other. The stars in the galaxies are far enough apart that they actually pass by each other. Some might collide if they are on an unfortunate path towards each other, but it is mostly the gas and dust that will make contact. This creates the conditions needed to trigger star formation and this is where we get the rich starburst activity. In about another 400 million years, the galaxy’s nuclei will collide and they will merge into that single elliptical galaxy mentioned above.

The starburst activity in these galaxies has created thousands and thousands of new stars. These cluster together in super star clusters. While normal star clusters might house hundreds or even thousands of stars, super star clusters can have tens of thousands of stars. The Antennae Galaxies also contain quite a few globular clusters that are relatively young. Most globular clusters in our galaxy and elsewhere in the Universe are old- around 12 billion years or older- and have ancient stars formed near the beginning of the Universe. So, to see young globular clusters in the Antennae Galaxies is a bit odd. These star clusters probably formed from the collision and will not survive past the next ten million years. Some might survive to become old-age globular clusters, but the majority will disperse and just end up as normal stars floating in space. So, while astronomers think that most globular clusters formed eons ago, it looks like galactic mergers can also create new ones!

This image will always hold a special place in my heart as it is the first image that I ever processed using data from the Hubble Space Telescope. I had gotten into astrophotography at the beginning of 2019, but I didn’t learn how to actually process an astronomy image until the summer of 2020. While it wasn’t that hard to learn how to use a telescope and take a picture, it was much harder to learn how to process the picture I took. I eventually met someone who offered to teach me through Skype, and lessons began in June 2020. He taught me everything about how to process an astronomy image. I had also learned about downloading Hubble data from another amateur astronomer. I figured that Hubble data might be nice to practice on, so using their guide, I downloaded the Antennae Galaxies and went to work. This was around August 2020. It wasn’t as hard to process as I thought it would be. Having a wonderful teacher helped immensely and eventually I understood how to process this stunning data!

My very first process of these stunning galaxies! Different areas of the galaxies can be identified by different colors. The yellow core is made of older stars with reddish-brown gas and dust crisscrossing it. Pink/red areas show the glowing hydrogen gas of nebulae where more new stars are being created. The blue areas show clusters of stars that have just been born!

Image Credit: NASA/ESA Hubble Space Telescope/ Alexandra Nachman. Image processed using FITS Liberator and Photoshop CC.

Eventually, I was able to learn new techniques and gain better image processing skills as time went on! This image began a wonderful journey where I learned how to process professional astronomical data. Because Hubble is funded by the US government, the data is free to the public, since we pay for it! This image is such a stunning image and I want everyone to be able to download and use this data! Below are links to resources so you can process your own image! Questions? Email me at peculiargalexyastro@gmail.com or reach out to me here!

RESOURCES

Image Data: This image was taken on July 21, 2004 by the Hubble Space Telescope. It was an image created using three greyscale images assigned to the RGB channels in Photoshop CC. A fourth layer as a luminosity layer was also used. The image files were downloaded from the Hubble Legacy Archive.

RED: hst_10188_10_acs_wfc_f814w
GREEN: hst_10188_10_acs_wfc_f550m
BLUE: hst_10188_10_acs_wfc_f435w
HALPHA LUM: hst_10188_10_acs_wfc_f658n

Interested in learning how to process your own version of this image? Check out the tutorial here!

To watch the work that goes into creating an image like this, check out this fun YouTube video here!

These images are associated with HST proposal 10188.

The first image was processed by myself, Alexandra Nachman, on 08/18/20, using data from the Hubble Legacy Archive. Image taken by NASA/ESA/Hubble Space Telescope. The second image was processed by myself, Alexandra Nachman, on 12/26/20 using data from the Hubble Legacy Archive. Image taken by NASA/ESA/Hubble Space Telescope.

REFERENCES- ALL INFORMATION IN THIS ARTICLE WAS TAKEN FROM THE SITES BELOW

NGC 4038 and NGC 4039, the Antennae Galaxies!

Recent Posts

Comments