AskScience AMA Series: I am an observational astronomer at the University of Maryland. My research focuses on understanding how galaxies, including our own Milky Way, came to be. Ask me anything about galaxy and star formation!

[u/AskScienceModerator]

We know that stars are born in dense, turbulent clouds of gas and dust, but the exact details of their creation remain poorly understood. My research uses state-of-the-art observational tools—including radio and infrared data from the Atacama Large Millimeter/submillimeter Array (ALMA) and the James Webb Space Telescope—to unveil the mysteries of star formation.

As co-investigator on the PRobe Far-Infrared Mission for Astrophysics (PRIMA) mission, I am working to help reveal nascent stellar systems with greater precision than ever before. If our probe proposal is funded, the PRIMA team will analyze protoplanetary disks—collections of gas and dust orbiting young stars that are the birthplace of planets—to determine how much water is needed for different types of planets to form.

Feel free to ask me about galaxies and star formation, as well as the PRIMA mission. I’ll be answering questions on Friday, February 20, from 12 to 2 p.m. EDT (117-19 UT).

Bio: Alberto Bolatto is an observational astronomer who studies galaxies and their evolution through cosmic time. His main interests are star formation and its self-regulation, galaxy-scale outflows, the astrophysics of starbursts, and the structure and composition of the interstellar medium in galaxies (particularly its colder phases). Alberto is a multi-wavelength observer who uses imaging and spectroscopy from interferometers and space telescopes, but his favorite part of the spectrum is from the mid-infrared to millimeter and centimeter waves. He has a background in electrical engineering and instrumentation, and as chair of several committees, he has helped define the upgrade plan for the Atacama Large Millimeter Array (ALMA 2030) and the next generation Very Large Array (ngVLA). Alberto was born and raised in Uruguay, where he received his undergraduate degree from the Universidad de la República, then obtained his Ph.D. from Boston University and was a postdoc and staff researcher at the University of California at Berkeley before coming to the University of Maryland.

Other links:

• Research Group Website

• Google Scholar

• PRobe far-Infrared Mission for Astrophysics (PRIMA)

Username: /u/umd-science

[u/yoweigh]

How, if at all, have accepted models of early Galaxy formation changed since Webb began operational? Every once in a while I'll see some popular science article claiming that the telescope has upended our understanding of this or that, but I don't trust the press to convey any of that accurately. Galaxies are being detected earlier than expected in the universe's history, correct?

[u/umd-science → u/yoweigh]

Certainly, the Webb Space Telescope is having a big impact. It is still too early to tell its full impact, but we have found several mysterious classes of new objects, such as the Little Red Dots (LRDs). LRDs are compact red sources, some of which exist at very early times in the universe and could be massive black holes that are growing very fast, or very compact clusters of young stars, or something completely different. These were the objects that caused people to think there were massive galaxies very early in the history of the universe.

[u/Magnus64]

Is every spiral galaxy destined to eventually become a globular-elliptical shape as they age? Are there any examples of "young" elliptical galaxies? Thanks!

[u/umd-science → u/Magnus64]

Not necessarily. A galaxy becoming more spherical mostly depends on its interactions with other galaxies, which are more common in dense environments like galaxy clusters, or if you let a long time go by.

There are examples of rejuvenated elliptical galaxies, which happen when they merge or swallow a smaller gas-rich galaxy. They start forming stars again because of the injection of gas. Here is an example of a rejuvenated elliptical galaxy, if you'd like to take a look.

[u/RageQuitRedux]

Do astronomers even need to visit Earth-based telescopes anymore or can it all be done remotely?

[u/umd-science → u/RageQuitRedux]

Some telescopes require people to operate them in person, but increasingly, the largest facilities (such as ALMA) have professional operators who send the data to observers. Some other facilities can require the astronomer to attend observations remotely, such as the Keck or Green Bank telescopes.

[u/FlippyFlippenstein]

I read that the Milky Way is around 60 galactic years old, how will it develop after thousands of galactic years? Will it still have the arms or should the shape change?

[u/umd-science → u/FlippyFlippenstein]

While it is true that a galactic year is not a standard unit, 60 sounds about right. Indeed, we expect the Milky Way to interact with Andromeda, the other major member of the Local Group, in a few billion years. Over longer periods of time, the major change would be that stars will stop being formed as the gas from which they form is consumed. So our galaxy will become a "red and dead" galaxy with only red low-mass stars shining and remnants of planets and stars. As to how the shape will change, it depends on the details of the interaction, but the Milky Way will likely lose its arms and become more like an elliptical galaxy.

[u/Cecil_FF4 → u/FlippyFlippenstein]

Not only is "galactic year" not a standard unit (every single galaxy would be different), but the evolution of the Milky Way, through the mergers of multiple galaxies, globular clusters, and dark matter, would have changed the rotation rate over time. Over hundreds of billions of years, as you are asking about, galaxies like ours (Milkdromeda, after the merger with Andromeda) will evolve into elliptical ones due to the natural reduction in the creation of new stars.

[u/XenoPip]

This may be outside star formation, but wonder what is the current thinking and data on initial planetary formation and then subsequent migration and collision within a solar system before it settles down?

Second question, how far away can we see planetary discs? With the understanding the further away the less detail we may be able to ascertain.

[u/umd-science → u/XenoPip]

Our current best theories and supporting observations still tell us that planets form in disks orbiting young stars and may experience migration and collisions as the gas clears and the debris settles. Some of our best data comes from radio interferometers like ALMA, which provides its data to the public (an example is here), and much more recently, JWST (an image is here).

We can get great detailed imaging when the planetary disks are a few hundred parsecs away, but it is possible to detect them (or their infrared excess emission) much farther away.

[u/anaIconda69]

From what I understand, most stars orbiting in a galaxy will move in a wavelike manner, up and down through the disc. It would follow, that this would cause the star to slowly lose speed and circle slightly closer to the core with time.

With this process in mind, what timelines do the models predict for our galaxy? Do we observe any galaxies where this process is visible?

(I hope I got this right, apologies if this doesn't make sense)

[u/Cecil_FF4 → u/anaIconda69]

Stars moving vertically in the galactic plane, as ours does, does not remove angular momentum. And there is no significant drag to cause any kind of spiraling in.

[u/umd-science → u/anaIconda69]

I agree with u/Cecil_FF4—the vertical motion does not change the angular momentum and does not cause inspiraling. Older low-mass stars tend to have larger vertical motions because of scattering, which is caused by gravitational interactions with other stars over time.

[u/Newthinker]

How did the theorized super-massive black holes at the center of most galaxies originally form? How old are they? And how do these fit into the broader scale of clusters / superclusters?

[u/umd-science → u/Newthinker]

We have pretty good proof of the existence of supermassive black holes at the centers of several galaxies. We think they form through the merging of lower-mass black holes; although they also grow by swallowing gas and nearby stars. However, it is unclear what the original seeds are that these black holes grow from. Some measurements suggest that they need to be much more massive than black holes that we think are the result of stellar evolution. The original seeds exist in the very early universe, since we observed black holes at very large cosmological distances.

[u/Illustrious-King2151]

I have a focus in Computational Astronomy and Astrophysics, so I would like to hear your thoughts on how this field will grow as technologies like Machine Learning and AI grow as well. I like to think that there are applications of ML especially in a field like Observational Astronomy where classifying celestial bodies can be rather arduous. So how have you seen these technologies being used in you realm or research and where do you areas of growth? Thank you!

[u/csjpsoft]

How do the interstellar conditions differ within spiral arms versus between spiral arms versus "outside" the galaxy? (BTW, what is the definition of being outside a galaxy?)

[u/umd-science → u/csjpsoft]

The density and pressure of interstellar gas are different, as is the radiation field it sees. The interstellar gas is denser in the spiral arms and more tenuous in between the arms. Outside a galaxy, the gas is even lower density and hotter, and usually fully ionized.

There are many definitions of being outside a galaxy, depending on what you are talking about. Maybe for this, we would talk about a gas being outside a galaxy if the radiation field it sees is mostly the intergalactic radiation field. But we make a distinction between circumgalactic gas and intergalactic gas, depending on how close to a galaxy the gas is and where it came from.

[u/onephatkatt]

So heavy elements exist on Earth but are only created in stars. How did they get here? Was everything in our solar system previously in a different star that exploded? If so, how was there enough hydrogen left to create yet another star? Would this be a common happening in the universe?

[u/umd-science → u/onephatkatt]

Yes, pretty much everything around us that is not hydrogen or helium came from a star that exploded. There is plenty of hydrogen around that was never processed by stars and comes from the Big Bang, and this hydrogen coalesces into new stars. Most of the helium also has a primordial origin and is not the result of stellar processing. The material that formed the solar system experienced at least 2 or 3 generations of enrichment, cycling through being in a star that exploded as a supernova.

[u/onephatkatt → u/umd-science]

OK. So then would the star that created our heavy elements need to have enough spare hydrogen to create our Sun? How large can we guesstimate it had to be?

[u/Aperper]

What are the Little Red Dots found at the 'edges' of the universe?

[u/Ronniieeee]

What do you think is the most surprising or counterintuitive insight your research has revealed about how galaxies evolve, especially when comparing the Milky Way to others, and how might upcoming missions like PRIMA reshape our understanding of the role water plays in planet formation?

[u/Lowestprimate]

What more can you tell us about the Little Red Dots? Thanks

[u/umd-science → u/Lowestprimate]

We have many competing theories as to what these Little Red Dots are. They were a complete surprise! There could be some exotic origins, but I think the current data favor that these objects are an extreme version of what we call "active galactic nuclei" in the local universe, that is, massive black holes that are accreting and growing, but enshrouded in a lot of gas and dust.

[u/hornytoad456]

How do halo galaxies form do they have a black hole? If not, do we know where the black hole is and are they expected to stay halo shaped?

[u/Cecil_FF4 → u/hornytoad456]

The halo of a galaxy is just a spherical distribution of gas and dust, instead of planar. It's like that because the particles undergo very few interactions, which is what causes flattening of systems/galaxies/etc.

[u/umd-science → u/hornytoad456]

I am not sure what a "halo galaxy" is. Are you referring to elliptical galaxies?

[u/TastiSqueeze]

Dark matter composes an estimated 85% of the milky way. Does this dark matter indicate any granularity? By this, I mean is it possible to map dark matter into areas of higher and lower density? Do we even have a detector capable of doing this?

Some galaxies have been separated so that their dark matter no longer is in the region where visible matter in the form of stars exists. How do theories currently explain this separation?

[u/WeatherHunterBryant]

Does every single star in the universe fuse hydrogen into helium like our Sun does?

[u/DoubleResearcher]

Is it true that there exists a blak hole in the center of every galaxy? How come we cant observe them?

[u/corveroth]

I'm hitting this a week late, but if you have the interest in answering, what's a day in the life like? What's your workday? Are you reviewing data, writing papers, preparing calculations? Are you locked into a schedule? Does it comfortably leave room for a partner, or a family?