As humans, we have looked to the celestial skies over the millennia and wondered about the stars and the wispy hints of what looked like night clouds. For most of humanity’s existence we had little or no knowledge of galaxies and only more recently even being aware of our own Milky Way galaxy.
The Antennae is actually a set of two spiral galaxies that are dancing together in the Southern Hemisphere, interacting, and sharing their stars.
It’s thought that the interaction began around a 200-300 million years ago and that they are in a current condition where the gas clouds that are colliding are filling up with stars that have just been born.
Their official designations are NGC 4038 and NGC 4039 and they are in the Corvus Constellation in the Virgo Cluster, although some often refer to them as the “Ringtail Galaxy.”
Scientists believe that the two galaxies merged and the intense gravitational interaction caused the long gas tails to pull away from each other. The starburst activity is found in the long tails.
It will take a couple of billion years, but eventually, the two galaxies will merge to become one large galaxy that has a center with a supermassive black hole. When that happens, it will be enveloped in an elliptical galaxy that contains old stars.
NASA refers to the condition of the twin galaxies as a “state of starburst.” This is a situation where all of the gasses in the galaxies are being used up in the process of creating new stars.
- Designation: NGC4038 and NGC 4039
- Galaxy Type: Interacting Spirals Tail/Tail Distance 350,000 light-years
- Distance: 45 million light-years
- Constellation: Corvus
- Group: Virgo Cluster
- Distance to Galactic Center: 45 million light-years
The twin galaxies have hydrogen as the largest amount of their gases and it envelopes the galaxies in long wispy clouds that stream out and away from them. It’s due to these hydrogen clouds that they have been called the “Antennae Galaxy” because they stretch out to appear like an insect’s antennae.
The galaxies are involved in a deadly embrace that locks them together. Although they might have once been spiral galaxies, they have spent a few hundred million years in a violent clash. The clash has caused stars to be ripped away from the galaxies and created a streaming arc between the two galaxies.
The streamers of far flung stars have created the long tidal tails that appear like antennae.
In 1785 William Herschel, the renowned British astronomer made the discovery of these twin colliding galaxies. While he was well-known for discovering the planet Uranus and identifying it as a planet and not a star, his discovery of the Antennae galaxies happened four years after that.
Herschel constructed over 400 telescopes to help with his research, but the most memorable one was 40 ft/12 m long and was made of iron that was set atop a moveable mount on a wooden frame.
William Herschel is given credit for recording over 800 pairs of stars that seemed to appear as if they were close together and over 2,000 celestial objects that he called “nebulae.” During that time period, many believed that the nebulae existed inside the Milky Way galaxy and it wasn’t until 1926 that they realized that these were separate and independent galaxies outside of the Milky Way galaxy.
The Antennae galaxy is believed to be one of the youngest and closest examples of a set of galaxies that are colliding. Almost half of the visual objects that are in the Antenna galaxy are images of young clusters that are home to tens of thousands of stars.
Images that have been taken show the two original cores of the galaxies like “orange blobs” on the right and left hand sides. These cores are mostly made up of old stars that are intermingled with dust that appears brown colored.
The two galaxies have a sprinkling of star-forming regions that are brilliant blue in color and these are surrounded by hydrogen gas that glows in a pink color.
The more recent images of the Antennae galaxy give scientists a better view to see the difference between the areas that are stars and the super star clusters.
Astronomers have been using calculations to age-date the clusters and have found that only 10% of the newer super star clusters formed during the collision of the two galaxies will probably survive beyond the first ten million years.
A super star cluster is a group of young stars that are held together by gravity and scientists think they are the prelude to globular clusters.
A majority of the super star clusters were created during the collision and will disperse, leaving the individual stars as part of the galaxy’s background.
Even with that loss, it’s thought that around one hundred of the biggest massive clusters will remain and form globular clusters, very much like those that we find in our Milky Way galaxy.
The Chandra X-Ray Observatory was active in the early 2000s in the research of the Antennae galaxy. Chandra made note of many bring points that were super star clusters, neutrons, or possibly black holes.
When a star collapses, the core can become a neutron star. When we observe a black hole, we aren’t really seeing the black hole itself, but instead, the hot gasses from the stars that are being drawn into them.
Chandra also discovered that the Antennae galaxy is made up of large quantities of iron, magnesium, neon, and silicon. In 2004 and 2007 they have seen that the Antennae galaxy has had at least two supernova.
The Hubble Space Telescope has also given scientists a lot of information during the three filming times of 1997, 2006, and 2013. The Hubble images display the Antennae galaxy as a stormy view of gas clouds, stars, light, and dust.
- Scientists think that the collision that has created the Antennae galaxy will complete itself in the next 400 million years.
- When the collision of the Antennae galaxy is done at least 10% of the young stars will die when the galaxy finally finishes and becomes a giant elliptical galaxy with a super massive black hole.
- The newly formed elliptical galaxy that results from the completed collision of the two galaxies will contain the two cores from both of the original galaxies, and both dying and old stars.
- It’s believed that the original NGC 4038 galaxy was a barred spiral galaxy and that NGC 4039 was a larger spiral galaxy.
- Neither of the two galaxies are considered to be spiral galaxies any longer. As the two interact with each other they are in a new category called “Interacting Spirals.”
- The Antenna galaxies are 45 million light-years from Earth. This information was updated from the previous idea that they were 65 million light-years from Earth.
- The Antennae galaxies are the nearest Interacting Spiral galaxies to planet Earth.
- Both of the twin galaxies have a black hole and when the collision and merger is complete they will form a supermassive black hole.
- The diameter of the Antennae galaxies is huge and is extended out to hundreds of thousands of light-years.
- The “antennae” are also called “tidal arms” and they were created when the two galaxies first collided around 200-300 million years ago.
- Scientists are studying the tidal arms of the Antennae galaxies as a way to find out what might happen when the Andromeda and Milky Way galaxies collide billions of years from now.
- Astronomers believe that the Antenna galaxies got their odd shape due to the collision that occurred in the past.
- There have been 5 younger stars in the Antennae galaxies that have turned into supernovae:
- SN1974E, SN2007sr, SN2013dk, SN1921A and SN2004GT.
- One of the requirements for a planet such as Earth is an abundance of silicon, magnesium, and neon. A high percentage of these elements are found in the Antennae galaxies.
- The reason that 10% of the stars in the Antennae galaxy won’t survive past 10 million years is that they will become blue supergiants that eat up their fuel fast and then end in a supernova explosion.
- After the Antennae merger is completed, all of the stars that remain will end up as part of the globular clusters for the new galaxy.
Exploration and Research:
The Hubble Space Telescope has been instrumental in creating some of the most incredibly detailed images of the Antenna galaxies. Hubble released images in 1997 when it used the Wide Field and Planetary Camera 2 (WFPC2), in 2006 using the Advanced Camera for Surveys (ACS) and then in 2006 with the ACS.
Due to technological upgrades and continued sophistication of programs, each of the images has been more improved over the last.
In newer images from Hubble’s Wide Field Camera 3 of the Antennae galaxies the signs of cloud gas are viewed in reds and bright pinks. The bright blue areas are the regions where stars are forming, some of which are hidden by darker dust patches.
The Antennae galaxies are creating stars at such a pace that scientists call this a “state of starburst.” This is a time when all of the gas inside a galaxy is being used to create new stars. Hubble used both visible and near-infrared observations for the latest images.
The ALMA (Atacama Large Millimeter/submillimeter Array) Observatory in Chile has shown areas in the Antennae galaxy that can’t be seen with visible light or infrared light. ALMA detected carbon monoxide molecules in the almost invisible hydrogen clouds where the formation of stars is occurring.
Updated images from the VLP (Very Large Telescope) of the Antennae galaxy offered more details of the colliding galaxies and their distorted shapes. The VLT focus turned to the nuclei of the galaxies where a lot of the action is occurring during the merge.
If you are going to plot the constellation location for observation:
NGC 4038 – 12h 01m 53s (right ascension), -18°52’10” (declination)
NGC 4039 – 12h 01m 53.6s (right ascension), -18°53’11” (declination)
Distance: 45 million light years
Apparent magnitude: 11.2 (NGC 4038), 11.1 (NGC 4039)
Apparent dimensions: 5′.2 × 3′.1 (NGC 4038), 3′.1 × 1′.6 (NGC 4039)
Designations: Antennae Galaxies, Ringtail Galaxy, Arp 244, NGC 2038, NGC 2039, Caldwell 60, Caldwell 61, PCG 37967, PGC 37969
In May of 2008, the Hubble Space Telescope does research that changes the previous distance of the Antennae galaxy from 63 million light-years from Earth to 45 million light-years from Earth.
Facts about Antennae Galaxies for Kids:
- William Herschel’s famous 40 ft telescope wasn’t dismantled until 1839. A section that is 10 foot resides in the Greenwich Royal Observatory.
- When spiral galaxies collide and merge they will typically create an elliptical galaxy that gets rid of the spiral arms that each galaxy has.
- Scientists believe that when the Andromeda and Milky Way galaxies interact and collide that it will probably appear much like the Antennae galaxies at least at one point during the interaction.
- The two galaxies are going through each other at incredibly high speeds. Scientists have estimated that they are traveling at hundreds of kilometers per second.
- Even though the galaxies are traveling at incredible speeds, it’s due to the huge size of the galaxies that is the main cause for taking hundreds of millions of years for completion.
- The “antennae” or tidal tails that the Antennae galaxy is known for formed due to the first collision encounter around 200-300 million years ago.
- Any material that isn’t held by gravitational pull during the collision of the two galaxies will be lost into space.