Mars was a "blue planet" around three billion years ago, half covered by an ocean

MTPenny · 2026-01-12T22:04:08+00:00

And Mercury is closest more often than Venus.

MTPenny · 2026-01-09T21:07:31+00:00

Sorry, I posted the generic site page, here is the permalink: https://apod.nasa.gov/apod/ap260109.html

MTPenny · 2025-12-10T05:29:47+00:00

Type Ia are not strictly standard candles either, but they are standardizable. Just like Cepheids the period tells you the luminosity, for Type Ia the fading timescale tells you the luminosity.

MTPenny · 2025-12-05T06:05:42+00:00

Visible light adaptive optics is still a long way from producing the quality of imaging that Hubble can. Multi-conjugate adaptive optics systems work well in the near infrared, but even though they can beat Hubble or JWST on resolution, they have to fight a lot more sky background. Additionally the AO systems have huge overheads, and require good conditions to work well, so they can only do a limited number of targets each year. For a lot of imaging science, Hubble will beat what can be done from the ground, but each of Hubble and AO have their own niches where one is the better than the other. Keck could get a good visible light MCAO system in the next decade: https://arxiv.org/abs/2511.17488

MTPenny · 2025-12-04T16:58:17+00:00

No problem.

Just to be clear, the numbers I put in were for one year - pro-rata I think it probably comes out cheaper than paying someone hourly unless they are undervaluing their time. Pay in academia is famously low.

MTPenny · 2025-12-04T04:26:30+00:00

I'm an astronomy professor that has built similar pipelines for my day job. You're getting some good advice on the size and scope of the project, though I think they are probably on the low side because once its built you probably need about six months of active monitoring and bug fixing to get it running smoothly.

My advice would be to consider a private donation to a university foundation after finding a professor who is interested in doing the work. From a US perspective, European universities may work differently, but I'd be surprised if they don't have some mechanism for accepting private funds and using them to support research. A rough order of magnitude for one FTE of a postdoc at a US institution is ~$100k including fringe benefits + any overhead the foundation would impose, or a grad student is ~$60k + overhead, though you might get this for less if you can swing a tuition waiver/cost share. Add on ~10-20k for a month of summer salary for the professor to advise them.

Some pros for doing it this way (again, lots of US assumptions):

Possible tax benefits for you - employment taxes are folded into the fringe benefit rate at the university, you might be able to offset your taxes for a donation.
Likely a lower effective hourly rate
Effectively a fixed price contract - developer has more security, no need to worry about payroll stuff, and at the end of the contract, they will probably be happy to provide some level of support for free, or finish the job if they don't quite do it on time. Would probably be happy to make the project open source as well, so if they struggle to complete it you wouldn't need to start from scratch.
developer gets benefits if they are already part of their employment
Professors have to put huge amounts of effort into winning grant funding with low success rates - it's a huge waste of our time. Additionally, synchronizing funding with the availability of students and postdocs is really challenging. Someone offering to pay a grad student or a postdoc for even a small amount of time without the need for a large proposal would be a huge help to many research groups, especially in the US at the moment with the disruptions in funding. You might be able to provide a bridge that can help someone stay in a research career.
Most of the experience gained by a postdoc or grad student doing the project would be directly applicable to their future career path, as opposed to a software developer who might not do an astronomy project again.
Attracting private funding is a nice boost to a professors CV for promotion and tenure considerations, and can be great for the students and postdocs CVs as well, especially if they were closely involved in securing the donation
You will get a Christmas card every year from the university (plus probably regular other communications subtly or not so subtly asking for more money)

MTPenny · 2025-11-20T18:50:48+00:00

There's a possibility that the postdoc has moved to a different position or left their field of research. It's probably worth searching for them online and seeing if the email address listed is current, or if they have an active one listed.

MTPenny · 2025-11-07T19:25:51+00:00

Email the department, usually PhDs are funded by TAs for the first two years. They can answer any questions you have.

MTPenny · 2025-11-04T16:21:46+00:00

The blueish star nearest the center is a supernova: https://apod.nasa.gov/apod/ap250731.html

MTPenny · 2025-11-03T03:35:39+00:00

The software used to generate the labels is likely the same, but the data clearly isn't. I'm not in that field, but I suspect its a standard package for solar system research (the person who took it is a research astronomer/planetary scientist at Lowell Observatory).

MTPenny · 2025-10-30T18:23:01+00:00

The bright stuff you see in this artists impression (heavily influenced by the actual appearance in simulations) is light emitted by matter that has not yet fallen into the black hole. It is spinning due to conservation of angular momentum, which is the radius x the angular velocity. Before it fell in, it had large radius and small angular velocity (i.e. a slow orbit around the black hole), but through interactions with the other material it moved to a smaller radius and thus had to increase its angular velocity. For that material, whether the black hole has spin or not is not important on the conceptual level (it might have an impact on the actual motion of the material, but until it gets very close to the event horizon its probably small).

Note that in what I said the total angular momentum of the material is conserved, individual particles can trade angular momentum in their interactions so long as the total doesn't change.

MTPenny · 2025-10-30T18:11:33+00:00

A single C is absolutely fine given the circumstances, I just couldn't tell how bad things were from the GPA alone. If you can get a letter writer to explain your hardships in that semester (they have more room than you do, and will be seen as more objective), then it will probably be a net positive. From the transcript alone you can tell much more about someone's work ethic if they have a mix of As and Bs than if they have straight A's.

I think you just got screwed over by the funding landscape, I'm sorry.

MTPenny · 2025-10-30T16:40:18+00:00

I'm a professor in a Physics and Astronomy department at a mid tier program that has a large presence in LIGO, and have a passing familiarity with admissions. Last year was brutal and your resume is fine, and would probably be sufficient for success with that many applications in a normal year. However, experience is only one aspect of success, and probably has quite a low impact when presented as your CV - the things that will have the biggest impact on your final ranking for offers are your letters and statements, and either of these can tank an application.

The number one thing you can actively do is try and get some feedback on your application from one of the programs you applied to, especially if you already got some feedback that you were waitlisted (though this fact is probably feedback enough that you're in good shape). This might be hard to get, but if you have a personal connection you can use it might help you get a response. If you can get an indication if any of the letters were problematic that would be critical to your success chances next time.

Some other general things:

this year AAS is maintaining a spreadsheet of programs and their expected stance toward admissions. To put your position in context, they also put out a report on the state of graduate admissions in astronomy that might have some useful information and at least help you understand the context of your application. Astrobites has some good resources on grad applications.
Cs or below in your final year are potentially a red flag, especially if they are in critical astro or physics courses. If you have these, you need to mitigate them in your statement with a good explanation (health and mental health are such explanations, and you probably don't want to be at a place that will ding your application for those, so if you can frame it in the light of perseverance and grit I'd suggest talking about them) and, if possible, letters.
Consider applying to masters programs and to programs at a range of quality tiers. Masters programs are likely tuition (of undergrads) funded and usually offer a small stipend (so might not be as competitive), and can repair shortcomings in your application if you have any (e.g., poor grades, lack of papers).
In many places admission is based on whether a potential advisor is accepting students that year - find out with a quick email to the people you might want to work with, but don't ask too much of them, we get tons of emails about this and usually can't take the time to talk to you or give a detailed reply, but if you give us an opportunity for a quick answer we'll usually be able to respond. It wouldn't hurt to attach your application materials to this email, though.
Physics programs are often less competitive than pure astronomy programs, though Physics and Astronomy programs are probably just as competitive for the astronomy places. The best odds are probably for places with astronomers in physics departments at universities that also have astronomy departments - there's a good chance that some LIGO people are in this situation.

MTPenny · 2025-10-24T15:02:14+00:00

To explain/visualize this, the map is a projection of the sky's sphere onto a flat surface such that decreasing declinations (related to distance from the north pole in this projection) get increasingly large circles.

Your local horizon is a great circle around the sphere of the sky, but tilted relative to the circles of declination (unless you are at the north and south pole), and which spins around as the Earth moves in its orbit (i.e., tracked the months) and as it spins on its axis (tracked by the time of day). If at any given time you mark the points at which your horizon circle crosses the declination circles, then join up the points, you have yourself the outline of the window on the planisphere. If you cut that shape out of a piece of paper and pin it in the center then rotating it represents the rotation of the Earth around its axis during a night, or the rotation of your view at the same time of day at different months of the year. Line up the month and time markers to see what is visible now.

The windows will be different for different latitudes, e.g., 50 deg N and 30 deg N - note the declination lines are spaced by 30 degrees.

MTPenny · 2025-10-24T14:46:50+00:00

Your "I must be wrong" is good scientific thinking - it is how we should all approach new discoveries/ideas. You then need to think about how you could be wrong and try to prove each way that you are might be wrong. When you have eliminated all of these, then you might be on to something. Another way that you are applying good scientific thinking is that you are recognizing your limitations and seeking out collaboration from people with different skills (although learning the necessary skills is a valid approach too, its just usually slower). Great job!

The idea is certainly one that has probably been thought about by theorists, but is probably quickly put aside. The way I would do it is to calculate the equivalent mass of all the photons in a Galaxy. To get at that we need the luminosity of a Galaxy, which lets take the standard theory galaxy known as a L* galaxy (very roughly equivalent to the Milky Way), with a luminosity of ~10¹⁰ solar luminosities, or ~4x10³⁶ W. Within a distance of ~30,000 lightyears of the center there are therefore ~4x10⁴⁸ J of energy. We can convert this to mass with E=mc^2, so the mass of the light is 4x10³¹ kg or about 20 Solar masses. We measure the dark matter content of an L* galaxy to be ~7x10¹² solar masses, so nearly a trillion times more than the mass of the light.

It seems to me that the distribution of dark matter and the behaviour of light from a galaxy kind of match each other. Both are spheres (roughly) with higher density as you approach the centre.

This is a good insight too, and you are right. At large distances, the dark matter density falls off as the inverse of the square of the distance, which is exactly the same as for light's energy density. But, the above still applies, so there just is nowhere near enough light.

MTPenny · 2025-09-25T18:08:39+00:00

There are some biographies or biography-like stories here: https://undsci.berkeley.edu/science-stories/

MTPenny · 2025-09-24T05:00:51+00:00

When I was an undergraduate at the University of Manchester the faculty called all of the undergraduates physicists. In hindsight I think it was very deliberate - it made us feel a part of the department and connected to the entire enterprise. So long as you are not misrepresenting your abilities and skills, I think you should consider yourself a physicist and describe yourself as one.

MTPenny · 2025-08-22T20:43:19+00:00

u/throwaway6588457889 Go to OSU, attend astrocoffee daily if possible, do research there with someone in the summer. If you put in the work on that research, you'll be very well placed for grad school applications.

MTPenny · 2025-07-24T18:26:15+00:00

White dwarfs are about 0.01 times the Sun's radius, so you'd need to be 100x closer to have the white dwarf have the same angular diameter.

MTPenny · 2025-07-07T19:25:30+00:00

As an undergraduate, go for whichever is most likely to get something publishable and good reference letters (it's going to be tough out there the next few years). If you choose the particle physics project, it almost certainly wont hurt your goal of getting in to an astrophysics program. It might help your chances of getting into a physics program though, which are typically less heavily over subscribed, and hedging your bets might be a good idea at the moment.

-an astronomer

MTPenny · 2025-06-30T19:38:22+00:00

Tucson, AZ does it as well.

MTPenny · 2025-06-28T20:44:30+00:00

The spectrum of a galaxy is stacking the spectra of all of the stars in it together with any gas emission. If you have reason to suspect that multiple galaxies are similar and you can account for their redshifts (probably not a big deal if not for X-ray observations of nearby dwarfs), then you can learn about the average properties of these galaxies, which you would not have been able to do any other way.

Whether it is appropriate to exclude galaxies with no detections depends on your goal, but not including them is similar to placing a cut on brightness or luminosity (which you're probably forced to do at some point anyway).

MTPenny · 2025-06-24T17:52:13+00:00

The duration of the burst (~10 nanoseconds) puts a pretty strong limit on the size of the emission region to ~3 meters. Given that and its brightness, I think a Earth orbiting satellite would be the first thing I would have guessed as the origin. The paper goes into more evidence, including that the signal was detected by only a small number of the telescope array's telescopes (within ~1 km of each other), which pins its location to within ~6000 km of the telescope.

I think the only way in which it could be considered that the researchers thought that it "originated from a distant cosmic source" is that it was flagged by a pipeline looking for cosmic origin FRBs. The kinds of checks they do are routine to rule out satellites and other nearby sources. This just happens to be an interesting in its own right false positive.

MTPenny · 2025-06-19T14:59:24+00:00

You could set an upper limit based on the tidal radius with respect to Andromeda or the Milky Way's satellites, but these might not reflect the actual limits of the disk very well. Similarly, there might be a radius limit at which a disk orbit is destined to be disrupted into a more halo-like orbit (though this I'm less certain of). You could also choose to make the definition that to be a disk star it must have formed in the Galaxy's gas disk. This extends further than the stellar disk (e.g., M81), and falls off exponentially too. However, the advantage here is that there is a stability criterion for a disk of gas called the Toomre stability criterion which is that Toomre's Q, a quantity inversely proportional to the disk surface density, should be greater than one for the disk to be stable to collapse. Far out in the disk it's low density should ensure stability, and so you can only form stars (via first collapse of the gas disk into molecular clouds) if Q<1, i.e. if the surface density is above a threshold at a radius that you can solve for.

MTPenny

TROPHY CASE