Arp 194 -- two colliding galaxies, a streamer of star birth and a background galaxy -- all shown by HST. (Click to embiggen.)
HST is probably the undisputed champion imager of colliding galaxies. For 19 years it’s been showing us the view as distant things go “bump” in the night. So, it’s only natural that the folks at Space Telescope Science Institute and the European Hubble office would celebrate the telescope’s 19th year on orbit with a smashing image of galaxy collision. This one’s a doozy, folks!
This image actually shows a trio of galaxies, only two of which are doing the actual interacting. The trio is called Arp 194, At first glance, it looks like one of them has sprung a leak. The bright blue streamer is really a stretched spiral arm full of newborn blue stars. You see these a lot during the aftermath of galaxy collisions and this is easily one of the most impressive ‘star fountain’ formations I’ve ever seen.
The two nuclei of the colliding galaxies can be seen in the process of merging at the upper left — they look like a pair of owl eyes. The blue bridge looks like it connects to a third galaxy. In reality the galaxy is in the background and not connected at all — although astronomers aren’t sure yet if there is any interaction between it and the northern pair of galaxies (which are interacting). Hubble’s sharp view allows astronomers to try and visually sort out what are foreground and background objects when galaxies, superficially, appear to overlap.
This whole scene is playing out about 600 million light-years from us, in the direction of the constellation Cepheus. The region has a number of interesting galaxy interactions, so this little galactic birthday party will likely not be the last that HST sees.
I must say, this is a great birthday card for HST. The telescope’s accomplishments are many: during the past 19 years Hubble has made more than 880,000 observations and snapped over 570,000 images of 29,000 celestial objects.
When comets do a turn around the Sun, they leave behind streams of dust particles that Earth eventually intersects in its own orbit around the Sun. Most of the time we see these particles as they enter our atmosphere and burn up. It’s rare to get samples of these dusty bits, but when planetary scientists DO get them, they’ve basically gotten their hands on very old, very primitive bits of material that existed LONG before the Sun and planets did. This is because comets formed out of the materials in the protosolar nebula — essentially they’re orbiting deep-freezes of ice and dust. Scientists have long known about comets and their treasure troves of ancient stuff. In 2003, they managed to gather up good samples of Comet 26P/Grigg-Skjellerup and have been studying them since then.
Interplanetary dust particles showing pre-solar grains of silicates and organic matter that originated in interstellar space. Courtesy H. Busemann. (Click to embiggenate.)
The findings are amazing. According to Dr. Henner Busemann of the University of Manchester, who is presenting these results on Tuesday at the European Week of Astronomy and Space Science being held at University of Hertfordshire in the U.K., the dust grains have all the signs of being very ancient — predating the birth of the Sun and planets. Some of it is true stardust, floating in interstellar space after being ejected during the process of birth, life and death of other stars. “We found an extraordinary wealth of primitive chemical fingerprints,” he said, “including abundant pre-solar grains, true stardust that has formed around other earlier stars, some during supernova explosions, associated with extremely pristine organic matter that must pre-date the formation of our planets.”
You can see a sample of the dust particles here. They are extremely tiny — only a few thousands of a millimeter in diameter. Two grains appear to have materials that scientists predict match the solar system’s birth nebula. One dust particle contained four pre-solar silicate grains (meaning grains that existed well before the solar system’s birth nebula formed) with an unusual chemical composition that matches the kinds of silicate grains that might form in supernova explosions. This is pretty good evidence that our birth nebula was seeded by the death throes of older, massive stars that once existed near our part of the galaxy.
More closeups of comet dust grains from the pre-solar-system neighborhood, more than 4.5 billion years ago. (Click to embiggenate.)
One of these grains is a fragment of olivine and was found next to a hollow globule of carbon, most likely of interstellar origin. Carbon is an interesting element to find because it is intimately bound up in the structures that ultimately build life.
Organic coatings are suspected to be the shells of time capsules that protected and secured the survival of some of these fragile stellar silicate grains as they made their way through the interstellar environment and, later on, the high radiation environment of the newly forming Sun.
Detecting the Chemistry of Life
This isn’t the only big news coming from the WASS meeting. Two researchers are also presenting a paper about the detection of two of the most complex molecules yet discovered in interstellar space: ethyl formate and n-propyl cyanide. Their computational models of interstellar chemistry also indicate that yet larger organic molecules may be present — including the so-far elusive amino acids, which are essential for life. The scientists used the IRAM 30-meter telescope in Spain to look at a region of the sky near the star-forming region Sagittarius B2. The molecules were found in a hot, dense cloud of gas that also contains a newly formed star.
Large, organic molecules of many different sorts have been detected in this cloud in the past, including alcohols, aldehydes, and acids. The new molecules ethyl formate (C2H5OCHO) and n-propyl cyanide (C3H7CN) represent two different classes of molecule — esters and alkyl cyanides — and they are the most complex of their kind yet detected in interstellar space.
This is pretty cool news on both fronts. These findings by separate groups of scientists tell us that we (our planet and our star) came from some of the same processes we see happening throughout the galaxy. The precursors of life are out there floating around in interstellar space, and scientists are finding more and more of them. It’s one thing to know and suspect these facts, but quite exciting to find evidence of our origins as part of the normal evolution of the universe and its stars and galaxies.
