In 2014, the Hubble Space Telescope (HST) found something unusual — a galaxy resembling a massive jellyfish in space. Astronomers question how the long tentacles of this barred galaxy formed, while recent observations show stars are being born within these bizarre structures.
Galaxies like ESO 137–001 are highly unusual, as conditions within groups of galaxies make the formation of new stars difficult. Most galaxies, like our own Milky Way, are part of small gatherings of galaxies, like our Local Group. However, some galaxies, like ESO 137–001, are members of galaxy clusters, containing hundreds or thousands of these structures. The space between these family of stars is filled with hot, tenuous gas, acting as a headwind as galaxies move through it, stripping these bodies of gas and dust, in a process known as ram pressure stripping.
“We think it’s hard to strip off a molecular cloud that’s already forming stars because it should be tightly bound to the galaxy by gravity. Which means either we’re wrong, or this gas got stripped off and heated up, but then had to cool again so that it could condense and form stars. Telling these two scenarios apart is one of the things we want to get at,” said Stacey Alberts of the University of Arizona.
A Jellyfish in Space? What’s so Weird About that?
Like our own Milky Way, ESO 137–001 is a barred spiral galaxy. Unlike our home family of stars, it is leaving behind a trail of debris as it races toward the gravitational center of a cluster of galaxies known as Abell 3627, at speeds approaching 7.25 million kilometers per hour (4.25 million MPH). The intergalactic dust in which this galaxy travels may be thin, but it has a temperature of 82 million degrees Celsius (180 million degrees Fahrenheit), causing it to glow in X-ray light, which can be detected by the Chandra space telescope.
This cosmic cephalopod is found 220 million light years from Earth, seen in the constellation Triangulum Australe. The tentacles of the jellyfish stretch across 260,000 light years, more than twice the diameter of the Milky Way galaxy. Young, hot stars in the tentacles of the body are glowing in ultraviolet and blue light.
A New View
This object, ESO 137–001, is destined to be one of the prime targets for the upcoming James Webb telescope, currently due for launch in 2021. Researchers using Mid-Infrared Instrument (MIRI) aboard Webb will examine this space jellyfish at wavelengths in the mid-infrared segment of the electromagnetic spectrum. These observations will detail ESO 137–001 at a resolution 50 times greater than possible with any previous infrared observatory.
Because material at the end of the tail left the galaxy before that found closer to the body, researchers will be able to see how the process of star formation is changing over time within the structure. Astronomers will combine images taken in infrared by the James Webb telescope with previous observations recorded in visible and ultraviolet light, in an effort to better understand this bizarre object.
Leaving a Mess in its Wake
Near the center of the galaxy, dust particles push back on the body, creating a cooler, darker region on the forward face of the galaxy.
“From a star-forming perspective, ESO 137–001 really is spreading its seeds into space like a dandelion in the wind. The stripped gas is now forming stars. However, the galaxy, drained of its own star-forming fuel, will have trouble making stars in the future. Through studying this runaway spiral, and other galaxies like it, astronomers hope to gain a better understanding of how galaxies form stars and evolve over time,” researchers taking part in the Chandra X-Ray telescope mission report.
When the light we see today from ESO 137–001 left its home, it was the beginning of the Triassic Period on Earth, when all the continents were huddled together into the Pangaea supercontinent, and dinosaurs were just starting to rule the world.