I AM A Robert Nemiroff from NASA's Astronomy Picture of the Day (APOD) website and a Professor of Astrophysics at Michigan Tech. Ask Me Anything.

Is there any astronomical entity or body (not sure what word to use here) that you would love to have a photograph of, but can't for some reason?

Fake answer: Yes, but [censored] [censored] because of [censored].

Real answer: Sure, other planetary systems, moons in our Solar System, a powerful gamma-ray burst just as it is exploding, and the region right near a black hole, to name a few!

What are your main criteria for pictures of the day?

Fake answer: We use a system called Blatent Financial Favoritism, or BFF for short. Apparently, this system has become quite common around the internet recently. For example, the other day some guy used BFF to get his crappy picture of the moon on APOD. He did it right as he shows up with a dump truck full of gold bars. It took over two hours to move all of those gold bars into our secure stadium vault which is now nearly full. But then it turned out that one of the gold bars was SCRATCHED, so then we didn't even run his crappy image. It's all about standards.

Real answer: We mainly want really cool, really important, and really educational images. If I say "wow!" within the first two seconds of seeing an image -- it is likely to end up on APOD. It an image is a "classic" so as to surely end up in astronomy textbooks, for example, then it is likely to end up on APOD. If the image is a great hook to explain a key concept in astronomy or physics, it is likely to end up on APOD. Also if a current sky event like an eclipse is captured in a cool and educational fashion, it is ... yes, likely to end up on APOD.

Is it easier or harder for you to choose pictures than it was in 1995?

Fake answer: Just as easy. I just ask my kids to do it and make sure they list my name. Sometimes if my kids are in school I make my wife do it.

Real answer: It is harder because there are so many more good images! APOD now rejects about 10 images for every one accepted. Back in 1995, there was some concern that APOD would run out of images. We did not think so, though, because, for example, the Ranger missions took thousands of images of the surface of the Moon. So we could always run a fresh Ranger image with "So this is lunar crater # 1431 -- notice how the center is slightly grayer than the yesterday's lunar crater # 1672". But even then there were enough good images to have an interesting APOD just about every day.

Could you provide a link to your favorite picture?

Fake answer: No.

Real answer: Yes, I could.

PS: Please feel free to post a link to your own favorite(s). I do find those useful.

Dr. Nemiroff, thank you (and thanks also to Dr. Bonnell) for APoD.
I have been teaching high school elective Astronomy since I started teaching twelve years ago, and start every lesson with the Astronomy Picture of the Day. Please keep it up.
Question: what is the next frontier in space imaging? Space-based telescopes? Ground-based? In what spectrum?

Fake answer: [The reddit moderators have determined that these fake answers are disrespectful and are discontinuing them.]

Real answer: Of course the pending James Webb Space Telescope, currently scheduled to be launched in 2018, should be rather awesome. Conversely, the advances in digital astronomical cameras and image processing is allowing for dedicated amateurs to obtain deep and wide field space images that continue to be just one new amazing advance after the other. Last, more people have personal cameras, smartphone cameras, and dashboard cameras so there will surely be more people in the right place at the right time to catch amazing but fleeting astronomical events like last week's Russian fireball. Last^2, there are more and more cool digital movies being made, so that more APODs are videos each year than each previous year.

What is one aspect of Space/the Universe that is not commonly known that you think people should know or appreciate?

Fake answer: That we all might be a part of your imagination.

Real answer: That we really don't understand very much about our universe. We don't really know what dark energy is, what dark matter is, what happens on the smallest scales, or what the fate of the universe will be. Oh, you said one aspect. OK, delete everything after "dark energy."

Hey there, Dr. Nemiroff. Earth Science teacher here. I've been looking at the APODs since I was in college (2002-2006) and now that i'm teaching I require my students to read the APOD everyday and answer questions about them (on a classroom set of iPads). So first off, thanks! The kids really enjoy them. Since you're doing this AMA I asked my students to formulate a list of questions, SO here they are!

1) How do you decide what pictures to use? Are they sent to you from people, or do you just have a list that you go through and choose whichever ones you want? If you have a list, how far in advance do you have? For instance, do you know what the APOD for June 12, 2013 is going to be?

2) Did you offer to edit APODs or did was it part of your job to begin with?

3) 5 best photos you've edited?

4) Have you (or anyone in the scientific community) ever discovered anything new BECAUSE of the APOD?

5) What's your favorite food?

6) Would you rather fight 100 duck sized Curiosity Rovers or 1 Curiosity Rover sized duck?

I will be sharing these answers with my students tomorrow. Fake and sarcastic answers are appreciated for these questions, too. My students have a pretty good sense of humor.

6) Would you rather fight 100 duck sized Curiosity Rovers or 1 Curiosity Rover sized duck?

Fake answer: It depends on the software.

Real answer: It depends on the software.

2) Did you offer to edit APODs or did was it part of your job to begin with?

Fake answer: Well the job NASA hired me to do was to help hold the launch pad down during rocket launches. That's good honest work. But my unorthodox gripping techniques were never well appreciated so that I eventually said "forget it" which during a rocket launch sounded a bit like "to edit", so I was transferred to APOD.

Real answer: We totally made APOD up from nothing ourselves. We did ask some NASA suits in 1995 if it was OK do to this. They essentially answered that the web was something for scientists and so NASA administration should not be involved. So we kept it going. I sure wish I saved that email!

Hey Robert! Which do you like more: neutron stars or black holes?

Fake answer: I like neutron stars as friends but once you embrace a black hole, you can never go back.

Real answer: There is a little-known hypothetical object sometimes called an "ultracompact neutron star" that might or might not exist but is surely really cool to contemplate. It is a neutron star so compact that photons can do full circles around it, just like for black holes. But it also has a surface you can see. So ultracompact neutron stars have all of the strange visual distortions (called strong gravitational lensing) of black holes -- but even more since you can see the ENTIRE SURFACE of the star from any location. Also, like near a black hole, you can see images of you yourself if you know where to look. The most famous example of this is seeing the back of your own head at the photon sphere. A grad student will reply with a link to computer animated movies on the web where much of this can be seen.

Thanks, everybody! I have to go now, but I will check back later and likely answer more questions.

What is your greatest discovery?

Fake answer: That if you invert a pull tab from a cardboard orange juice box it looks almost exactly like the star ship Enterprise (tm).

Real answer: I guess the part I played in showing that gamma-ray bursts (GRBs) were consistent with being far across in the universe, not nearby like in our own Galaxy. That was one of the largest controversies in astronomy back in the mid-1990s (again). Then I was part of a group of scientists (at NASA at the time!). There is now lots of hard data showing that (most) detected GRBs are indeed far across the universe, and just like I was hoping at the time, are actually useful for understanding the nature and composition of the intervening universe.

Actually it is hard for many scientists to one's "greatest discoveries", including me. Some research papers I think will never be cited become relatively well known, while others I think will surely "show the way" seem to disappear and are essentially forgotten. I would guess that is typical, though.

Hello, Besides starship asterisk->Latest Sky Photography or sending you a mail, which other sources do you use to get the APOD?

Fake answer: Many times President Obama himself will call me up about an image. He has been overstaying his welcome here, though, and so now I just let most of his messages go to voice mail. There are several heads of state, though, that I would still like to hear from.

Real answer: APOD still gets many email submissions, and APOD is subscribed to several space press lists that announce when a new important discovery has occurred or when a new major image release is available. Also, I surf the web like many people and do and luck upon really cool images sometimes. I then either chase copyright permissions myself for such an image or ask a volunteer to chase it. Some of these make really excellent APODs. Yesterday's "Asperatus Clouds over New Zealand" was one like that.

thanks for your answer. Have you ever posted an APOD and then the same day or a few days after found a much better image of the same evet or object?

Fake answer: No. We guarantee that APOD images are the best on the internet and we will give you your money back if a better one appears.

Real answer: Actually this is a real effect. Sometimes APOD posts the best image we can find on something and then others who see this say "hey -- I've got a better image than that!" and sends it in. But then we are unlikely to post the better image because WE JUST RAN AN IMAGE JUST LIKE THAT. But the conundrum is that we might never have know of the better image if we had not posted the initial image. I don't know a way around this. After a few days, months or even a year, APOD will surely post the better image. And then sometimes be sent an even better one the next day! Another reason to keep checking APOD.

HI RJN,
First a big thank you for APOD, part of my day.
Now my question: I read that escape velocity here on earth is around 7miles/sec but to escape the sun's pull here at earth's orbit is around 15 miles/sec. Is the sun pulling harder on me right now than the earth is? THANKS!, DosBoot

Fake answer: Yes.

Real answer: No.

Brand new telescope, what is the first thing you look at?

Fake answer: The Moon.

Real answer: The lens cap. I cannot tell you how many times I have looked into a just-set-up telescope and been baffled as to why I CANNOT SEE ONE FREAKING THING. Of course once the lens cap is removed you should look at the Moon. Then of course you should curse because the Moon IS SO FREAKING BRIGHT that you can't see anything else with that eye again for the next 60 seconds. Welcome to real astronomy.

Is there any "objective" evidence that speed of light (and/or related vacuum permittivity/permeability) or gravitational constants have been constant over the age of the universe? Or could some of the dark energy/matter observations be "easily" explained if they are not constant?

Real answer: This is a controversial topic that easily raises emotions (so no jokes here). The conservative view is that Einstein's General Relativity (GR) coupled with Friedmann-Robertson Walker cosmology -- including dark matter and dark energy -- fit the astronomical data pretty well. And I agree. It is possible to invent new theories or add new parameters (some varying with cosmological time) to fit the astronomical data, but in order to knock Einstein and Friedmann off the top of hill, a new theory has to make falsifiable predictions that are different that GR-FRW and can really be checked in the near future. To the best of my knowledge, that has never been done to the satisfaction of the astrophysics community. So GR-FRW keeps its crown.

And now a word of practical caution. Please don't try to publish such a theory if you will be seeking job security in a standard academic job in the near future. Your friends, family and even close co-workers may believe you -- but it is possible -- even likely -- that the promotion committee has seen too many theories like this go sour to promote you. Please ONLY try this if astrophysics is your hobby or if you already have tenure.

If you were to be cast as a character on any science fiction television show, movie or novel(graphic included), what would you choose? What character would you be?

Fake answer: I would choose to be the alien in Dark Star. Here's a start: https://www.youtube.com/watch?v=ESQK98HbKBY

Real answer: I would choose to be "Bailey" on Star Trek. Now who is Bailey? Fasten your safety belts because we're (almost) going back in time. In the original Star Trek TV series episode called the "Corbomite Maneuver", an alien ship threatens to blow up the Enterprise (big surprise). Sulu, though, starts reading off the time until the ship explodes, perhaps initially with a bit too much glee in his voice. Bailey was a bridge officer who voiced the most concern with the impending doom. Oh good, here is a YouTube clip: https://www.youtube.com/watch?v=JPii8d8iZoM . Oh and here is a parody I wrote up years ago: http://sprite.phys.ncku.edu.tw/~htsu/humor/startrek.html .

I thought Bailey was a quite useful plot enhancer since he actually displayed and voiced emotions that many people would have in that situation, all while trying to keep a brave face. And yet hearing Bailey go off was somehow a bit humorous. I had always hoped Bailey or a Bailey-like character would return in the original Star Trek, but I don't think that happened.

First, i would just like to say that you are an awesome person as well as inspiration, and when i go to get my masters from Michigan Tech (because i will) i would love to meet you. Thank you for APOD!

Till then, a few questions

1. What do you think is the most important direction for astrophysics in the future?

2. Where do many of the "unresolved questions" of the universe remain?

2.5. How hard would it be to be a volunteer in your lab (as an undergrad)? haha

1. What do you think is the most important direction for astrophysics in the future?

Fake answer: Up!

Real answer: Another thought provoking question. I guess that depends on what one considers "important". Is exploring cosmological attributes of dark energy more important that discovering Earth-like planets? Or uncovering a higher percentage of dangerous Earth-bound space rocks? There are just so many things that are unknown, that it is hard -- for me at least -- to access which things are more important than others.

Presently, astronomy seems to involve at least three different types of interests. Defense -- like better discovering dangerous space rocks and advancing imaging techniques, engineering -- by better uncovering how the universe works so that better mousetraps can be built, and by entertainment -- by (slightly) better quenching humanity's thirst to answer fundamental questions about space, time, life, and origins. Everyone seems to want astronomy to justify itself with the first two -- and it does in my opinion -- but it seems to me that as human free time and computer power expand, the world's economy is increasingly tilting toward the third.

2.5. How hard would it be to be a volunteer in your lab (as an undergrad)?

Fake answer: It would be pretty easy unless you are killed during one of our elaborate hazing rituals, some of which involve, for example, moose polo and cheesecake.

Real answer: I almost always have a small group of graduates and undergraduates working with me. In my extremely biased opinion, we sometimes have quite a hoot. We have weekly all-hands meetings where we discuss research and APOD-related activities. I try to fit people into both research and outreach projects (typically one of each) where they feel comfortable. Last summer we even had a weekly pizza and poker game (with only pride at stake) where laughs were cheap, a video of that week's astronomy news was playing in the background, and I kept interrupting our game to make another possibly-annoying point about probability or statistics. (It is sometimes useful for a data analyst in science to have an intuitive "feel" for what different levels of "likely" or "unlikely" mean, and poker gives one such an opportunity.)

Was it a hard decision to add videos as a daily feature? When was the first video featured on apod?

Fake answer: Yes, but "hard decision" is my middle name. OK, names.

Real answer: It seems December 31, 1996, was the first "video APOD" according to the APOD archive. Here it is: http://apod.nasa.gov/apod/ap961231.html . It was a "moving GIF", the type that are becoming more popular again these days. It was really small because of the limited bandwidth most people had back then. We've struggled with different movie formats over the years, and now usually just embed YouTube of Vimeo videos, although there is some uneasiness over what happens if that content is over-commercialized or even deleted over copyright squabbles. (See, for example: http://apod.nasa.gov/apod/ap110418.html).

Why do stars only come in blue, white, yellow and red? Why don't we see green or violet stars?

Edit: Forgot yellow

Fake answer: OK look, we only have pictures of three stars around here -- blue, white, and red. Moreover, the Photoshop palette thingy has disappeared and nobody can figure out how to get it back. So when we compose all of these APOD pictures, we are presently limited to blue, white, and red stars. So please let's pretend green and violet stars don't exist for now.

Real answer: Stars usually have colors related to their temperatures. A star can have almost any temperature with hotter stars emitting more blue light than cooler stars. Also, the net star color you see is a mix of many colors. Stars can therefore appear very many colors, with white really being a nearly equal combination of all visible colors. Wikipedia has a good write-up: http://en.wikipedia.org/wiki/Black-body_radiation . But yes, even given this, most stars do appear, mostly, blue, white, or red. Well and orange, too.