Ask an Astrophysicist - APOD's Dr. Jerry Bonnell

[bystander]

Dr. Jerry T. Bonnell, a research astrophysicist at NASA's Goddard Space Flight Center, has graciously consented to be interviewed by APODees/Asteriskians. Jerry, along with Dr. Robert J. Nemiroff (RJN), is co-editor of APOD.

If you have any questions about APOD or astronomy you would like to ask Jerry, please post them in this thread. They will be forwarded to Jerry and his answers to selected questions will be posted to the Asterisk* later this month.

[quote="Dr. Jerry T. Bonnell (JTB)"]

Thanks for all the questions … at long last, here are some answers! And thanks, bystander and owlice, for suggesting and arranging this thread. For what it’s worth, I’ve collected the short versions of the answers up front in a synopsis. The long versions are embedded with the questions below. - cheers, Jerry (Sep. 7, 2010 - GSFC).

Synopsis: GRBs,QG,TGFs,AGNs;contractor/Cosmic Dawn, New Worlds, Physics of Universe/related,yes, extrasolar planets, GRB distance, accelerated expansion, funding/no/moon landing/parent’s approval/Tighe/no/42/yes/in backpack, sensitivity, no/real soon/yes/T?/T, funding/bob, jerry/filters/ AFAIK? fair enough/tomorrow’s (probably), yes, yes, email/yes/ funny …/ yes, not pros, we have/not science, no, no/SN 1987A, NGC 1976, easily, thank you/oh?/ brown/copyrighted ones?/easy to read/sure/ 250 million yrs at sun, galactic rotation, 400,000 ly/no problem/my trilobite knows/no problem/us size 9 ½/ yes but forgot question/rotation curve?/ good deal in ir/longer answer too/light-weekend?/event horizon, general relativity, standard model wrong, quantum fluctuation, inflation first stage[/quote][/i][/color]

[owlice]

I'd like to know a couple of things:

• What is his current area of research?
• What is the deal with UMD? Is he teaching there?

[quote="JTB"]

For a few years now I’ve been working on the Fermi Gamma-ray Space Telescope Project. Fermi has been in orbit since the summer of 2008, surveying the sky at gamma-ray energies (roughly 50 million times the energy of visible light photons), so it is really intended to explore very energetic and violent astrophysical environments. Fermi science that I’ve been involved in includes Gamma-ray Bursts (GRBs) and Active Galactic Nuclei (AGN). I also confess an interest in Fermi’s recent results for Terrestrial Gamma Flashes (TGFs).

One of my favorite results related to GRBs (so far) is:

“A limit on the variation of the speed of light arising from quantum gravity effects”, 2009Natur.462..331A

As for the deal with UMD … I’m an employee of the University of Maryland under contract with Goddard Space Flight Center. That’s not an uncommon arrangement for scientists at Goddard. I don’t teach at the university …[/quote][/i][/color]

[Guest]

What area of research will be the most active over the next 10-20 years?

[quote="JTB"]

I feel confident in predicting that those areas of research that are well funded will be the most active in the next decade! Fortunately, we’ve just been told what those areas are recommended to be by a National Research Council committee in the Astro2010 Decadal Survey. That committee identified three science themes: Cosmic Dawn, New Worlds, Physics of the Universe. Cosmic Dawn encompasses searching for the first generation of stars, galaxies, and black holes. (James Web Space Telescope fits in there.) New Worlds is the search for extrasolar habitable planets. Physics of the Universe is understanding dark energy, dark matter, cosmology, and general relativity.[/quote][/i][/color]

[Ann]

I am very interested in dark energy. Is Dr. Bonnell involved in any research about that? Does he have any particular thoughts about dark energy?

Astronomy and astrophysics have made huge strides in recent years and recent decades. What breakthroughs and discoveries have been the most interesting, according to Dr. Bonnell?

If Dr. Bonnell could find the answer to one astronomical mystery or riddle, what would that be?

Ann

[quote="JTB"]

I’m not directly involved in dark energy research (like the Hi Z supernova work). That is definitely something that was not going on when I was in grad school, but I’m encouraged that the universe is still finding ways to be strange. In addition to the dark energy results, recent breakthroughs that I would identify as particularly interesting to me are the detections of extrasolar planets, and the discovery of the distance scale to gamma-ray bursts.[/quote][/i][/color]

[Guest]

Does Dr. Bonnell ever tire of producing APOD?

[quote="JTB"]

I guess the short answer is no. I still often feel energized by APOD. It gives me an excuse to explore connections between Science, Art, Life, the Universe, and Everything.[/quote][/i][/color]

[Guest]

When/how did you become interested in astronomy?

What impact has APOD had on your career?

[quote="JTB"]

I am a child of NASA’s Apollo program. If I had to point to any one thing that inspired my career in science it would be either the Apollo program or the refrigerator in my mother’s kitchen. I absorbed everything to do with the moon landings when I was a kid. I spent my paper route money on a telescope and camera, took pictures of the moon through the telescope and then took pictures of the TV showing the moon landings. I also enjoyed staying up all night. If there were no moon landings going on, my brother and I would just go outside and look for meteors. The mystery of the refrigerator was also inspirational. As far as I could tell, everything else in the house that was plugged in got hot, but the refrigerator got cold. I don’t think I really understood why until I took freshman physics in college.

Career-wise the success of APOD has generally been a good thing, generating contacts and some recognition. At this point, I can’t imagine not doing (or having done) it. Of course, it is a bit of a time sink, but if APOD hadn’t taken off something else potentially even more useless would surely have come along to distract me.[/quote][/i][/color]

[buffer]

What does the T stand for?

[quote="JTB"]

Tighe (sounds like tie)[/quote][/i][/color]

[BMAONE23]

What does the T stand for?

Tiberious?

[quote="JTB"]

nope[/quote][/i][/color]

[neufer]

What is the meaning of life?

[quote="JTB"]

42. Did you think I didn’t know?[/quote][/i][/color]

[owlice]

Art, you might as well ask him if he has his towel with him, too.

[quote="JTB"]

I actually carry a substitute towel.[/quote][/i][/color]

[bystander]

Art, you might as well ask him if he has his towel with him, too.

Hmmm, good question. To paraphrase Douglas Adams:

• ... any man who can explore the width and breadth of the universe, rough it, slum it, struggle against terrible budget cuts and new administrations, win through, and still know where his towel is is clearly a man to be reckoned with ...

Do you know where your towel is?

I read awhile back that the WISE mission would not be extended past the current cold mission. I realize that WISE is not a point and shoot type of spacecraft, but in view of the still valuable data being returned from Spitzer's warm mission, do they not think that WISE would return enough valuable data from a warm mission? It's already there, as long as it is still functioning why not use it?

[quote="JTB"]

Sorry bystander, I have not heard this about WISE and just don’t know.[/quote][/i][/color]

With all the new discoveries and information in astronomy and astrophysics, are there any plans for any more Great Debates and what are the possible subjects?

[quote="JTB"]

In 1995 Bob Nemiroff and I (re)discovered that the location of the famous 1920 Shapley-Curtis debate on the “Scale of the Universe” was an auditorium in what is now known as the National Museum of Natural History in Washington DC. That was only a few miles from our office at Goddard Space Flight Center. Actually, I’m sure historians had not lost this information but astronomers really did seem to have forgotten about it. Bob was very keen to hold another debate there, this time on the Distance Scale to Gamma-ray Bursts, a hot topic in 1990s astrophysics and one that Bob and I thought had parallels to the original debate. We did manage to pull it off, too, inviting the world’s experts and two champions of competing distance scale theories to debate. We did two other debate programs there along similar lines; “The Scale of the Universe in 1996, and “The Nature of the Universe” in 1998. You can read about them by following the “Great Debates” link above. In the end, I think organizing the debates began to require too much effort (not the debate part so much as the begging for funding part) and we eventually just got involved in other things. Bob and I have no plans for future debate programs. We hadn’t run out of topics, though. In fact, in 1999 we had started to organize a debate on “The Nature of Life in The Universe” …[/quote][/i][/color]

[Beyond]

I would like to know when you are going on vacation. You're going to need one after you get through answering all these guys questions

[quote="JTB"]

Real soon. My towel (or reasonable facsimile) is poised and ready.[/quote][/i][/color]

[neufer]

Art, you might as well ask him if he has his towel with him, too.

I thought it was a better question than: "What does the T stand for?"
(Ann could tell you it should be: "For what does the T stand.")

Our high school principal was named T. Marcus Gillespie.

Someone finally found out that the T. stood for Tiffilus.

Any guy named Tiffilus knows for sure that there is absolutely NO meaning to life.

[owlice]

(Ann could tell you it should be: "For what does the T stand.")

I could tell me (or even buffer) that, too, if I had a need to. But I don't, so I won't!

Our high school principal was named T. Marcus Gillespie.

Someone finally found out that the T. stood for Tiffilus.

Any guy named Tiffilus knows for sure that there is absolutely NO meaning to life.

Wow. My brother is a T.something; not for Tiffilus, though. He has it bad enough with his family nickname!

[Ann]

Art, you might as well ask him if he has his towel with him, too.

I thought it was a better question than: "What does the T stand for?"
(Ann could tell you it should be: "For what does the T stand.")

No, it should be, "What stand the T for?"

Like bystander, I too would love some more Great Debates.

Ann

[quote="JTB"]

At this point, maybe I could just interject that; at least T stands for something, grammar is not my strong point either as my grades in English will attest, and, yeah, the Great Debates were fun. Still, I’m reminded that the actual Nature of the Universe is not determined by who can sway the majority opinion. But funding often is …[/quote][/i][/color]

[guestimate]

Who decides which pictures to use? I would like to know 'behind the scenes' how APOD is done.

[quote="JTB"]

The behind the scenes operations of APOD originally developed while Bob and I shared an office at Goddard. In those days we could easily collaborate by pointing, shouting excitedly, and throwing things for emphasis. Often we chose pictures by surfing the NASA websites and finding ones that really grabbed us. Over the years we ended up at different institutions and I think we have evolved into a more “tag team” style approach for constructing the APOD pages for individual days. Travel schedules not withstanding, Bob usually does the first part of the week and I do the last. Collaborations are not ruled out, though. Also, many, if not most, of the images are submitted to us now and we choose from those. We do try to look ahead and coordinate enough to avoid what we have come to call “collisions”, i.e. when both Bob and I come up with the same picture for two different days.[/quote][/i][/color]

[Biogeography]

I am curious why so many of the photos of Mars and Titan taken by various oribters and lander probes are black and white. Certainly we have the technology to take color photos.

[quote="JTB"]

Yes, but our technology of making a color image is fundamentally based on making “black and white” images through different filters (e.g. red, green, and blue filters) and combining them somehow. That is certainly done with cameras used on space missions by taking separate frames through different filters. Combining them into a color image then just requires more computer processing and people often do that when they think a really nice image will be the result. But the individual filter frames that do contain the scientific information are also frequently shown in a grayscale or black and white image. Interestingly, in your point and shoot digital camera, a patterned array of color filters, called an RGB Bayer filter, covers the digital image detector so that some pixels have a red, some have a blue, and some have a green filter on top of them. That way, in a single exposure you get some information from all three filters, but it’s distributed in patches across the scene. Before your camera presents you with the final image, it interpolates and combines the information from the filters so that the picture looks like it has natural and not patchy colors to you. That’s not ideal for science data and so a Bayer filter scheme is not used in space missions.[/quote][/i][/color]

[bystander]

Edit: Four posts with questions about meteor heat and mass accumulation, along with the answers from Chris, were removed and merged with APOD: Meteors Over Quebec (2010 Aug 16) starting here and here.

(These meteor questions are probably best asked in the general questions about astronomy section. AFAIK Dr Bonnell isn't a meteoriticist.)

[quote="JTB"]

Thanks for the help here and if IK what AFAIK means then yes, Dr. Bonnell is not a meteoriticist …[/quote][/i][/color]

[Guest]

What are your favorite APODs? Do you have any of these displayed in your office/at home/on your computer? Do you give talks or presentations to schools/groups/et cetera on APOD and astronomy? If you do that, how could someone request this?

[quote="JTB"]

I have a lot of trouble picking my favorite APODs, mostly because after I pick one, I always seem to find another that I like better and just can’t seem to stop. It may just be a character flaw, but I’m told I am a sucker for big, beautiful spiral galaxies. Here’s one - APOD: 2006 November 26 - M31: The Andromeda Galaxy . Once Bob Nemiroff did force me to try to pick favorites for a year and we finally came up with this list: APOY 2007. I do have some APOD related stuff on the walls at home and have had this one as a background on my desktop machine at Goddard for a few years now - APOD: 2006 December 29 - Alnitak, Alnilam, Mintaka . Also, I certainly do give talks to groups (as does Bob) … just email to ask.[/quote][/i][/color]

[spacey]

if you were offered an opportunity to spend time on the ISS would you go?

[quote="JTB"]

In a flash.[/quote][/i][/color]

[bystander]

This question has been merged with APOD: NGC 4755: A Jewel Box of Stars (2010 Aug 17), here.

The pic of the day showing the "Jewel Box" says they are 10M years old. That seems extremely young. Did they mean 10B?

[quote="JTB"]

Incidentally, they do mean 10 million years, not 10 billion years. And that is very young for a star! Unfortunately, this also reminds me of an old astronomy joke …

A student walks into an astronomy lecture and sits down. "In 5 billion years" the professor says “ the Sun, will run out of fuel and die". The student asks, "How long did you say we had?" The professor repeats his 5 billion-year prediction and the student says, “Good! I was getting worried. I thought you said 5 million years!" (Astronomers never tire of laughing at this.)[/quote][/i][/color]

[HAL 9000]

ARe there pictures you'd like to be putting on APOD that you don't have? IOW, are there objects that don't get much attention from professional astronomers that you wish would be photographed that havent been?

[quote="JTB"]

If I had a picture of a scene just beyond the event horizon of black hole, I’d put that on APOD. (Oh, wait, I do have that here - APOD: 2002 September 8 - Too Close to a Black Hole). But actually, I don’t have a list of specific objects I would like to see imaged. I would just say I’m appreciative of the imaging professional astronomers can do beyond the visible spectrum. That often requires detector technology that is really pushing the limits and I’m amazed that imaging is even possible in some of those domains (e.g. gamma-rays).

The “amateurs” on the other hand are really enjoying a golden age of digital astronomy in the visible. Detectors and telescopes that used to require institutional resources and funding are now within the reach of individual hobbyists and can be bought off the shelf. I think the availability of computing power and that level of equipment has produced an explosion of creativity in astro-imaging (fortunately for APOD!). So even when the same object is imaged many times you tend to see new aspects emphasized in the different versions. [/quote][/i][/color]
do you publish pictures that you or Nemirof have taken? I have been looking at apod for a couple of years and don't remember seeing any pictures from you guys. or maybe you don't take pictures at all?

[quote="JTB"]

Very rarely do we use our own stuff. The link above shows work that Bob Nemiroff did, and here’s one of mine - APOD: 2005 January 27 - Shadow Set . I also do imaging with a near-infrared camera built by my colleagues in one of the labs here at Goddard. Here’s a result from that camera - APOD: 2003 March 13 - WIRO at Jupiter . But the projects that we use it for (e.g. monitoring AGN and GRB afterglows) just haven’t produced many other “pretty pictures”.[/quote][/i][/color]

[webolife]

How does Dr. Bonnell feel about the Electric Universe theory? It seems to be gaining a large following, and presents some provocative information. Has he looked into it at all, or does he have any strong case evidence against it?

[quote="JTB"]

Actually, a former colleague and friend of mine, Dr. Tom Bridgman, has put some effort into debunking this and maintains a blog discussing EU claims here:

The REAL Electric Universe[/quote][/i][/color]
Note: More from W.T. "Tom" Bridgman on debunking the Electric Universe.

[julianm3]

What supernova is closest to Earth? What stellar nursery?

Also, as one of the masters of APOD, are you able to cope with the massive fame and adoration everywhere you go?

Thanks again for all the great work.

[quote="JTB"]

I guess I would have to resort to some qualifiers to answer the supernova question. For example, in our lifetime, the closest supernova to Earth has been SN 1987A in the Large Magellanic Cloud (only about 150,000 light-years away). But in recorded history, there certainly have been closer ones, within our own galaxy, although light from those explosions has long since faded in our sky. We still see the supernova remnants, though. Given that distances to the remnants are estimates and could change, I think the closest one to Earth on the historical list could be SN 1054. We call the remnant of SN 1054 the Crab Nebula. Within the nebula is the Crab pulsar, and that’s about 6,000 light-years away. If you want to go back in time 10,000 years or so, you could have seen light from the supernova corresponding to the Vela supernova remnant only 1,000 light-years away. A gamma-ray pulsar called Geminga is the collapsed core left from supernova also about 1,000 light-years away. But Geminga is more like 300,000 years old. Of course, the closest supernova ever was likely the one thought to have triggered the collapse of the solar nebula and birth of the solar system about 5 billion years ago …

For closest stellar nursery, I would venture the Orion Nebula, about 1,500 light-years away.

And thanks for the questions julianm3. I actually don’t even recall experiencing massive fame and adoration, so I must have coped with it very well![/quote][/i][/color]

[neufer]

What supernova is closest to Earth?

Nearby (~200 parsecs) Geminga & Vela Pulsars in Gamma Ray Sky Credit : NASA/DOE/International LAT Team

---

<<Geminga is a neutron star approximately 157 parsecs away from the Sun in the constellation Gemini. Its name is both a contraction of "Gemini gamma-ray source", and gh'è minga "it's not there" in the Lombard dialect of Milan. The nature of Geminga was quite unknown for 20 years after its discovery by NASA's Second Small Astronomy Satellite (SAS-2). Finally, in March 1991 the ROSAT satellite detected a periodicity of 0.237 seconds in soft x-ray emission. Thus, it is supposed that Geminga is a sort of neutron star: the decaying core of a massive star that exploded as a supernova about 300,000 years ago. This nearby explosion may be responsible for the low density of the interstellar medium in the immediate vicinity of the Solar System. This low-density area is known as the Local Bubble. Possible evidence for this includes findings by the Arecibo Observatory that local micrometre-sized interstellar meteor particles appear to originate from its direction.>>

<<The Vela supernova remnant (SNR) is one of the closest known to us. The Geminga pulsar is closer (and also resulted from a supernova), and in 1998 another supernova remnant was discovered, RX_J0852.0-4622, which from our point of view appears to be contained in the southeastern part of the Vela remnant. One estimate of its distance puts it only 200 parsecs away (about 650 ly), closer than the Vela remnant, and surprisingly as well, it seems to have exploded much more recently (in the last thousand years or so) because it is still radiating gamma rays from the decay of titanium-44. This remnant was not seen earlier because in most wavelengths it is lost in the image of the Vela remnant.>>