How Often Are New Stars Born in the Milky Way?

Stellar nurseries can be found in giant clouds of molecular gas and dust scattered throughout our galaxy. The Octo-mom has nothing on these stellar nurseries, as these regions can produce multiple stars at once – into the hundreds at a time. How often does this happen? On average, one new star is born somewhere in our Milky Way galaxy per year, astronomers estimate. But with the newborns arriving together in dense clusters, stars aren’t born, or created, very often in the Milky Way. Recently, astronomers took a close look in infrared at what was happening inside a giant stellar nursery called RCW 38 and saw hundreds of stars in different stages of development. What they found was significant, as this represents the first time a massive cluster other than the one in the Orion Nebula has been studied so precisely.

RCW 38 is located about six thousand light-years away, and is one of only two relatively nearby giant clusters with over 1000 stars. The other one is the Orion Nebula, which is 3.5 times closer and much easier to study, and so thus far a unique example.

The astronomers studies 317 stars in the cluster at three infrared wavelengths. About thirty percent of them were noticeably red, suggesting the presence of circumstellar, perhaps protoplanetary, disks. They also found traces of shocked gas and a few even younger protostars, all features consistent with this being an active stellar nursery.

This initial study is expected to be followed up with more in-depth looks to determine which features of a cluster are characteristic of all clusters, and which (for example the spatial distribution of the stars, the numbers of different kinds of stars, or the numbers of stars with protostellar disks) are only circumstantial.

Future studies will also tell us more about our own solar system. One line of thinking is that our sun may have formed in a cluster that later dissipated. Since ultraviolet light can evaporate dust, massive hot stars that emit such light may have played a role by inhibiting the formation of planets if they were near the young sun; likewise, if a nearby massive star exploded as a supernova during the early days of the sun, the event might explain the abundances of radioactive elements found in the solar system.

Read more about this study of RCW 38 in the team’s paper.

16 Replies to “How Often Are New Stars Born in the Milky Way?”

  1. … if a nearby massive star exploded as a supernova during the early days of the sun, the event might explain the abundances of radioactive elements found in the solar system.

    It has been postulated that the Ordovician–Silurian extinction event, 450 Ma to 440 Ma, was caused by a nearby supernova or gamma-ray burst progenitor.

  2. IVAN: I think the article is referring to an event much earlier than that. Think about all the Uranium (and other assorted element heavier than lead) in the Earth’s crust. For all those heavy elements we would be talking about a nearby supernova explosion to have occurred before the planets of the solar system fully formed, or perhaps even before the Sun did.

  3. @ Dave Finton,

    Of course, but I was just pointing out the fact that a nearby supernova could have occurred even later on in Earth’s time-line, resulting in mass extinctions, as mentioned in that Wikipedia article that I have linked to above.

  4. Funny, isn’t it? If a nearby supernovae hadn’t decided to pop off and seed the primordial solar system with Uranium all that time ago, then we’d have no natural Uranium here on Earth in any quantity worth mentioning and we’d likely not have nuclear power or nuclear weapons. Not only that, but the quirk of nuclear structure that allows Uranium to be so useful in these roles is the very same reason that it has an unusually long alpha decay half life. If it’s half-life were any shorter than it is, we’d again find ourselves with no naturally occurring Uranium!

    I think every reasonably minded person must agree that the message is clear – God wants us to have nuclear power and nuclear weapons.

    Feel free to use this argument against any anti-nuclear campaigner you may come across to smite them with. It is air-tight.

  5. I wonder if those clusters match the Initial Mass Function (IMF) we observe here. Has anyone read the paper; do the authors state anything concerning this topic?

    @ Lenard Lindstrom

    You can even make further arguments:
    No heat, no plate tectonics, no dynamo below us, no magnetic field any more, possibly the atmosphere is gone due to that (the solar wind can rip it off much easier when there is no magnetic field), radiation levels would be much higher, we could face a senario like Mars.

    Yes, the earth is quite fortunate!

    So, @ Astrofriend, it is not that god wanted us to have nuclear weapons. God wanted the earth to have human beings and they just need so long to develope. So he placed enough uranium in the Earth’s crust to keep it warm!

  6. OF course the overabundance of proof of other planetary bodies orbiting other stars and lacking uranium……… Oh hang on, we can barely detect planets around other stars. 🙂

    The only viable proof that Uranium exists elsewhere seems to be the recent results from Kayuga on the moon.

    Interestingly if the idea that supernova creates Uranium is valid, then other planets may have naturally occurring Plutonium and even heavier elements we have never seen.

    On another matter, I’m fascinated by the idea of our sol having siblings from a common nursery.

    Damian K

  7. @Damian-

    I have always thought that superheavy elements, including ones much heavier than the ones we know, could be produced in supernovas. They may not last very long, but perhaps they can be detected in the spectra of supernovas. After all, helium was discovered in the spectrum of the Sun before it was found on Earth, so why not?

  8. @ Nexus.

    The problem is that those heavy elements tend do decay SO rapidly that they should be long gone before you can even get a good spectra. All the “new” elements we creat on earth (proton numbers higher than, say, 107) are very hard to produce and even harder to detect. They really decay fast with half-life-times of, say, less than a second. There is a possibility that at special numbers of protons and neutrons you will get at least partially stable nucleii again, but it is rather unlikely that those were created in a supernova.
    But you should ask a particle physicist about that matter (haha!), they should tell you if such things are possible.

  9. Without the uranium and thorium that heats the Earth’s interior the mantle might have cooled off by now. No heat, no plate tectonics or volcanism.

    It might, seeing that these isotopes stands for 70 % of the total heat flow, but to this layman it doesn’t feel convincing without looking at a specific model. Plate tectonics acts to increase the heat flow. And Mars, at 1/10th of the mass and so roughly 1/2th of the initial heat flow unless I’m mistaken is claimed to have internal heat and had active volcanoes for a long time. (Oh boy, did it have volcanoes!)

    Mars arguably even have signs of inactive plates. Since the Earth analog Venus plate tectonics, if it ever happened, seems to have stopped, there are more important factors involved. AFAIU liquid water has been mentioned as one such factor.

  10. @DrFlimmer

    I see no real reason why supernovas can produce copious amounts of Thorium and Uranium (elements 90 and 92) but stop short of making things like element 114 and 126. Isotopes of both of these are predicted theoretically to have rather long half lives.

  11. when you people are not fighting with each other, i really enjoy reading your comments.

    thanks ivan3man for causing me to read about the O-S extinction event.

  12. @ Nexus

    I didn’t look it up, now, so I am just guessing.
    I would say that at some point the reactions would stop because of energy constraints. The reactions to build the heavy elements become more and more endothermal. So the heavier the element you build the more energy you need (and the more energy you finally lose).
    The biggest part of the energy of the supernove is in the neutrinos. The rest goes into radiation and the blast of “ordinary” matter. So there is only a limited amount of energy.
    My guess is that there just not enough energy left to creat even heavier elements than beyond, say, 100 (I don’t know where the peroidic table originally ended).
    But one should read that up somewhere…

  13. There is every reason to Suspect that Heavier elements could exist naturally. Its suggested that a lack of naturally occurring plutonium on earth is because the hypothetical supernova was only x big.

    I had read that someone had in fact discovered natural plutonium, however my memory is vague.

    I do distinctly remember reading that Uranium has been detected on the outside of the MIR space station and other orbiting satellites, It is assumed that these might have originated from high altitude nuclear tests, however this is not definitive. It may be that solar wind or cosmic rays are in fact the source.

    Also as a curiosity, as all human spaceflight in orbit dumps their (ahem) liquid waste, into space, it has been detected that all space ships / space suits are a coated in x % of urine. 🙂

    Damian K

  14. Most Uranium (U) on Earth was not produced in a single supernova just before solar system (S.S.) formation, The ratio of U isotopes tells us that most U was formed in earlier supernovae long before the S.S. formed.
    However, there is evidence of transuranic elements forming just before S.S. formation. For example, a fission decay product of Plutonium-244 (half-life ~80 million years) is found on Earth, the Moon, and in meteorites.

  15. IIRC, both the Compton Gamma-Ray Observatory (CGRO) and COS-B from time to time detected hard radiation suspected to be coming from poorly designed/shielded nuclear reactors in Soviet satellites(military & non-military). Radiation contamination from some Soviet satellites was a problem for some satellites with detectors sensitive to x-ray and gamma-ray radiation, and still is.

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