We are scientists and artists using the Fermi Gamma-ray Space Telescope, NASA’s largest active gamma-ray mission.

Speaking of Fermi; what's your personal favourite solution(s) to the Fermi paradox?

There is likely no one single solution to the Fermi paradox. One contributing factor that could explain a late emergence of life in the Universe is the proliferation of gamma-ray bursts in the early Universe. A large fraction of gamma-ray bursts are thought to be due to the death of supermassive stars. When these stars die as gamma-ray bursts, they release an enormous amount of gamma-ray radiation. This form of high-energy radiation can be very disruptive to biological molecules and may have hindered the emergence of early life. These types of stars were much more common in the early Universe than they are now, so it’s possible that nascent life was eventually able to take hold on their host planets once the rate of gamma-ray bursts declined over time. - DK

I just googled "fermi bubbles" and the images it returned are fascinating. Could you give us a brief overview of what's going on there?

The Fermi Bubbles are one of Fermi’s big mysteries. They are enormous structures extending from the center of our Galaxy. Each lobe is 25,000 light-years tall, and the whole structure may be only a few million years old. Within the bubbles, extremely energetic electrons are interacting with lower-energy light to create gamma-rays, but right now, no one knows the source of these electrons. The energy may have come from an intense period of star formation or maybe from an outburst from the supermassive black hole at the center of the Galaxy. - EAH

How much, if any, has Einstein@Home contributed to the mission and is distributed computing in general helpful for missions such as this?

The Einstein@Home distributed computing project has been used, successfully, to search for gamma-ray pulsars in the Fermi Large Area Telescope data. This has led to the discovery of 18 new pulsars, some seen only in gamma rays so far, using 10,000 years of volunteered CPU time. This includes the discovery of the first radio-quiet millisecond gamma-ray pulsar. These results truly demonstrate the power of distributed computing for any mission with years and years of data to search/analyze. See https://fermi.gsfc.nasa.gov/fermi10/fridays/02092018.html for some more details on discovering puslars with Fermi. --TJ

How is Fermi related to the detection of gravitational waves by LIGO?

The Fermi Gamma-ray Burst Monitor, one of Fermi’s two instruments, detected a gamma-ray burst 1.7 seconds after the detection of gravitational waves by LIGO and Virgo from the merger of two neutron stars. The gamma-ray burst provided important clues into this extreme event and kicked off one of the largest observing campaigns in modern history with telescopes all over the world and in space seeing different components of the merger. - JLR

What would cause the delay?

There was a 1.7 second delay between the merger of two neutron stars detected by LIGO and Virgo and the detection of a gamma-ray bursts by the Fermi Gamma-ray Burst Monitor and the INTEGRAL SPI-ACS. The time delay could be because it takes a little bit of time for the jet to form and break out of the ejecta. It’s also possible that before collapsing to a black hole, the merged neutron stars briefly formed a hypermassive neutron star supported by rapid rotation, delaying the creation of the jet and the resulting gamma-ray burst. We also use this time delay to test whether or not the speed of gravity is the same as the speed of light, and they seem to be or at least really really close. - JLR

Is it true that if a gamma-ray burst were to hit Earth it would destroy us all? (Or at least fry our satellites?)

Gamma-Ray Bursts (GRBs) are produced by the explosion of very massive stars, or the merging of two compact objects (neutron stars and black holes). In both cases they release a very large amount of energy, and they are potentially harmful for habited planets in their galaxy. However, the probability of a GRB happening in our galaxy is extremely low. Also, we believe that the emission from GRBs is beamed in a cone with a fairly small opening angle, so the chance of the Earth or another habited planet being in the direction of the jet is even smaller. Moreover, the impact of the radiation of our atmosphere is believed to be detectable but not lethal (see for example this paper: https://arxiv.org/abs/1510.03360). - GV

What is the most powerful GRB did the FGrST detect?

The most powerful GRB detected by Fermi in terms of intensity detected is by far GRB 130427A. It was the brightest in the last 25 years. See https://www.nasa.gov/content/goddard/nasa-sees-watershed-cosmic-blast-in-unique-detail . This GRB appeared so bright in our instruments because it was “only” 3.6 billion light years away, a lot closer than the typical GRB. However, in terms of emitted energy, the brightest GRB was actually GRB 080916C (https://www.nasa.gov/mission_pages/GLAST/news/high_grb.html), which emitted almost 100x the energy of GRB 130427A. However, it happened at a distance around 3 times larger than 130427A and therefore appeared fainter in our instruments. - GV

Thank you everyone for your questions. We're signing off now.

Before Fermi was launched, did you expect blazars to be the most abundant extragalactic gamma-ray sources?

Although gamma-ray bursts still outnumber blazars, we did expect blazars to be the most abundant persistent sources. The predecessor to Fermi, the Compton Gamma Ray Observatory, found blazars to be the most numerous class of identified sources. That was a good clue. - DJT

Is every thing on the satellite still working (sensors, controls, etc) , if not, were you able to create workarounds to fix the problem?

Overall, Fermi has been working very well. We have had one issue that caused one of our two solar panels to stop rotating. We have adjusted our observing strategy to avoid taking that solar panel too far away from the sun. We’re developing an observing strategy that will work around the constraints imposed by the failure. - Elizabeth Ferrara

When will the new Fermi LAT source catalog be ready?

The Fermi-LAT Collaboration is working actively on the new catalog of sources detected with 8 years of data. We are planning to generate this catalog using a new model for the Interstellar Emission. The plan is to have the catalog for the next Fermi Symposium in fall of this year. - MDM

How long did it take you to discover the Fermi Bubbles? Were there any false starts or mistakes before you were able to determine that they were a thing?

Were any of you involved in contest math when you were in school? :)

The Fermi bubbles were discovered by a group at Harvard using the public Fermi Large Area Telescope data, just two years after the Fermi launch. They talked to Fermi scientists to make sure the bubbles were not produced by some instrumental effects. Cross-checking unexpected results is important, and these scientists were careful to do that before they published.
Several of us participated in math contests in school (but I was not very successful at it). - DJT

What is the most exciting thing we've learned from this project so far?

That there were a lot of sources of astrophysical gamma rays we hadn’t anticipated. Fermi continues to make discoveries even after 10 years. - TJ

What kind of art has Fermi inspired? Are the artists sponsored directly by the mission?

Fermi science has also inspired edible art, especially in the medium of cake. In our spare time, a group of us Fermi scientists (and amatuer bakers) have made cakes for launch anniversaries, celebrations, new PhDs, A “science as food” competition, group meetings, and MICA art debuts. Sometimes these cakes look like Fermi, the gamma-ray sky, or other astronomical objects we detect. -JLR

Fermi has inspired a lot of art! Specifically, a lot of animations involving Fermi and Fermi’s research results can be found here: https://www.astroanimation.org/ where students from the Maryland Institute College of Art (MICA) have collaborated with NASA scientists to create work that helps demonstrate just how awesome Fermi is! This is done as part of our coursework. Some of the animations can also be seen in the planetarium at the Maryland Science Center. -SS Check out the 4th Fermi Friday of each month for more info: https://go.nasa.gov/2HEsZDp

Fermi has inspired both scientific and creative art through NASA artists and animators. NASA employs many artists who work directly with the science community to enhance their ideas and findings. https://svs.gsfc.nasa.gov/Gallery/Fermi5.html - JF

What are the most ambitious experiments running or being planned to run on the Fermi Telescope? What kind of results are expected from those experiments?

The main instrument on board the The Fermi Gamma-Ray Space Telescope (GLAST) is the Large Area Telescope (LAT), that measures gamma rays in the energy range of about 20 MeV to about 300 GeV. The second instrument is the Gamma-ray Burst Monitor (GBM) complements the LAT in its observations of transient sources and is sensitive to X-rays and gamma rays with energies between 8 keV and 40 MeV. The two experiments provided in this 10 years a great variety of results such as observations of active galactic nuclei, searches of dark matter, electromagnetic follow-up of gravitational wave events. - MdM

IMO, the most ambitious investigation that is currently ongoing is the search for dark matter. Even if we don’t detect dark matter with Fermi, that result will give us information about what dark matter isn’t, which is important for the theorists that work on this topic. - ECF

Fermi's paradox is my favorite paradox. Do you believe the FGST will offer anything in the search for life? And how is it that space is so stable that our planet can pass through with no disruptions, like turbulence, even though we are supposedly passing through dark matter?

It’s likely that Fermi will not provide any direct evidence for extraterrestrial life (unless alien life communicates via gamma-ray signals), but Fermi’s observation of gamma-ray bursts may help inform models of how they could have influenced the development of life in the early Universe, when the stars that produce gamma-ray bursts were much more common. The stability of Earth’s ecosystem, and its suitability for life, over billions of years is actually quite remarkable. This can be attributed to the stability of Earth’s orbit around the Sun, as well as the Earth’s carbon cycle (https://en.wikipedia.org/wiki/Carbon_cycle), which helps regulate the climate of the planet on timescales of hundreds of millions of years.
Fortunately, space is pretty empty, with an average interstellar density of one hydrogen atom per cubic centimeter, so there’s not a lot to run into out there. We are also lucky that whatever the nature of dark matter, it must interact very weakly with normal matter, otherwise scientists would have detected it using experiments here on Earth. - DK

What are the greatest discoveries you have made ?

You can choose, via the Fermi Science Playoffs: https://go.nasa.gov/2xUkZym - JLR

What is dark matter and dark energy? Or at least, what's known about them?

We really don’t know what dark matter and dark energy are. But we know some things about them based on our observations of the Universe. Dark matter constitutes about 85% of the matter in the universe. We have many different observations that provide evidence for its existence, such as the rotation curves of galaxies, the anisotropy of the cosmic microwave background, and clusters of galaxies. If dark matter is interpreted as a new particle, it should interact very weakly with ordinary matter making it difficult to detect. Dark energy constitutes 70% of the combined matter and energy in the Universe. Its existence has been inferred from observations of distant supernovae and from the evidence that the expansion of the Universe is accelerating. Theoretically, one possible interpretation is the cosmological constant introduced by Einstein in the Theory of General Relativity. - MDM

So I have 3 questions. 1) why study gamma rays? 2) whats the weakest, or furthest thong you've seen firmi? 3) is it like Hubble where scientists can put in applications to use firmi or is it strictly for NASA use?

1) Gamma-rays tell us about some of the most extreme conditions in the Universe with the strongest magnetic fields, strongest gravity, hottest and densest environments, including regions around black holes and neutron stars. Studying these extremes gives us insight into how these objects work and can be used to test fundamental physics. 2) The farthest object the Large Area Telescope ever detected was GRB 080916C (https://go.nasa.gov/2l0U9v8), a bright gamma-ray burst that took 12.3 billion years for the light to reach Earth. The Gamma-ray Burst Monitor detected the most distant gamma-ray burst ever detected, GRB 090423, that took 13.1 billion years for the light to reach Earth. The weakest sources ever detected by the LAT provided only a handful of photons over the last 10 years. It’s hard to tell from so little information, but they are probably from active galaxies or pulsars. 3) Similar to Hubble and many other NASA missions, scientists propose specific scientific studies to Fermi, however since Fermi observes the whole sky every few hours, everyone automatically gets their observations. In rare cases, we do change Fermi’s observing strategy for short periods of time to increase the chance of detecting transient sources. All Fermi data are public, you too can take a look: https://go.nasa.gov/2sXW73e - JLR

1. How long does it take to point the satellite where you want to take a picture?
2. How long does it take to take a picture?
3. What is the resolution of the said picture?
4. What would be the fps if you tried to take a video?
5. How did they test it when it was back on earth

Thank you nasapeople!!!

Answer1: (1) Fermi’s Large Area Telescope is a wide-field scanning instrument that sees a large portion of the sky at any given time, and usually sees the entire sky every three hours. If we want to point at a specific part of the sky, a slew can take up to 10 minutes. - ECF

Answer2: (2) The Fermi instruments detect individual gamma rays, so it is a matter of how long it takes to collect enough of these. For bright gamma-ray bursts, it can be a fraction of a second. For faint sources, it can take years to accumulate enough gamma rays to see the source. - DJT

Answer3: (3) A typical resolution for a gamma-ray image from the Fermi Large Area Telescope is something like 1 degree on the sky, but images made using a long exposure and the best localized gamma rays can reach resolutions of a fraction of a degree. -EAH

Answer4: (4) As noted for Answer 2, it depends on how bright the source is. A fast gamma-ray burst could make a video with many fps, but for a weak source, it would be frames per year. -DJT

Answer5: (5) Before launch, we tested as many of the different subsystems and commands as we could by sending them directly to the spacecraft in the test facility. Some functionality, like slewing and repointing, had to be tested against a simulator to ensure that the commands behaved the way they should. - ECF

The instruments were tested using a combination of radioactive sources, high-energy accelerators like CERN (https://home.cern), and high-energy particles (muons) whizzing through the Earth’s atmosphere. - EAH

We also put the individual instruments, and later the entire spacecraft, through environmental testing where we vibrated them (to simulate launch), put them under vacuum (to simulate space), and baked/froze them (to simulate Sun/eclipse cycles). - ECF

Thanks for doing this AMA! I have a couple of questions for you that I hope you have time to answer.

1) What is the frequency range for this telescope? Is it able to see the full gamma-ray spectrum?

2) Have the detection instruments ever gone off-scale high due to gamma ray bursts?

3) How many gamma ray bursts are visible to the telescope on a yearly basis? Do you see bursts daily?

Thanks!

Fermi has two instruments onboard and covers the frequency range from 10¹⁷ to 10²⁶ Hz. For reference, 10¹⁴ Hz is about the energy of visible light that our eyes see. There are ground-based telescopes that can go to even higher energies, but Fermi covers a large range of the gamma-ray spectrum. The Gamma-ray Burst Monitor sees a gamma-ray burst (GRB) about once every two days. Fermi-GBM has detected over 2300 GRBs during the 10-year of operation so far. The Fermi Large Area Telescope is sensitive to higher energies and detects about 15 GRBs every year. There has been some very bright GRBs seen by both instruments, breaking the record for brightest GRB and highest energy photon detected. Bright solar flares have caused saturation in both Fermi instruments, but these are rare. - MH

Now that Fermi has been up for 10 years, what comes next in terms of space-based gamma-ray telescopes?

1) Lots more Fermi! The gamma-ray sky changes all the time and we are still discovering new surprises. 2) Gamma-ray spectral lines: When there are radioactive elements in astrophysical objects, they emit gamma rays concentrated at specific energies too low for Fermi’s Large Area Telescope to detect. A telescope that can collect those gamma rays will give us unique information about supernova explosions. 3) Gamma-ray polarimetry: Some gamma rays carry information about the magnetic fields where they were generated. Detectors that can measure the polarization of the gamma rays would give us a whole new view of these sites. - EAH

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Fermi is a gamma-ray detector, so we really do not shoot gamma rays at anyone. - DJT

What about LIGO detector and Arecibo radiotelescope?

Because you need information from a lot of sources to understand the universe, Fermi scientists work closely with scientists in other disciplines. In fact, some of us are part of other collaborations. I use the Arecibo Observatory to search for new pulsars in new Fermi sources, while several others here work closely with LIGO to search for gamma-ray emission from LIGO-detected mergers. - ECF

Do you have any more updates on coincidence between GRBs and gravitational waves? Are there any more exciting results coming out of multimessenger astronomy?

GW170817 is the only known coincident detection between GRBs and gravitational waves. However, there was also a less certain detection of a faint signal coincident with a black hole - black hole merger. The association of this signal will be confirmed or disputed by the detection or non-detection of other similar events in the future. There are papers coming out almost every day dealing with the modeling and the interpretation of these events. At the moment the LIGO/Virgo observatory is undergoing upgrades that will make it much more sensitive. The next observing run, scheduled for 2019, will provide an exciting opportunity for more coincident detections. Regarding multi-messenger astronomy, we are looking forward for exciting news coming out very soon (stay tuned). The multimessenger era has just begun, with gravitational waves observatories, neutrino observatories, and instruments capable of detecting polarization of electromagnetic radiation all operating at the same time. There will surely be discoveries and surprises in the upcoming months/years. - GV

What is the coolest thing you've found in your research?

When Fermi was launched, there were only a few kinds of sources that were known to emit gamma rays. Over the last 10 years, Fermi has discovered that there are lots of different kinds of objects that make gamma rays, including stellar novae, globular clusters, millisecond pulsars, and more. -ECF

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I think one of the coolest pulsar results from Fermi is the transitional millisecond pulsars. These are sources we have observed to switch between acting like a typical pulsar and siphoning gas from a companion star. When they transition to the siphoning phase, the amount of gamma rays and x-rays that we see increases by a factor of 5 or more. It has long been thought that this ‘siphoning’ was how millisecond pulsars reached such rapid rotation rates, and these observations are an important part of understanding this process. See https://go.nasa.gov/2xZaH05 for more on these awesome sources. --TJ

Seeing gamma rays from colliding neutron stars that produced gravitational waves was definitely cool (although the resulting smash-up was definitely hot). https://go.nasa.gov/2hJV3Ky -DJT

A cool Terrestrial Gamma-ray Flash (TGF) result was that they are generated in violent natural environments, such as hurricanes and tropical storms. It is amazing that thunderstorms (nature’s most powerful producer of gamma rays on Earth) do this. More on this result can be found in this NASA press release: https://go.nasa.gov/2JtnNbc -OJR

Fermi found rapid changes in gamma rays from the Crab Nebula. The flares were so intense that we found out the Crab is a source of the highest energy electrons we can point back to. https://go.nasa.gov/2FeZuYB -EAH

the most memorable part of this mission?

The first time that we looked at the all-sky data from Fermi’s Large Area Telescope it was like somebody took the data from predecessor telescopes and turned the knob to bring it into focus. It was an amazing and immensely gratifying experience. I think about that every time I see the sky map and every time it becomes a deeper and sharper image. https://www.nasa.gov/mission_pages/GLAST/news/gammaray_best.html - EAH

The time Fermi had to duck out of the way of a speeding Russian satellite was pretty exciting! We hadn’t planned on using our thrusters for anything except de-orbiting the spacecraft at the end of the mission. But moving out of the way seemed like the best idea at the time. https://go.nasa.gov/2JuFOGe Also, launch day was pretty exciting. I didn’t get to see the launch in person, but a bunch of geeky scientists were watching from the beach in Florida. If you want to see what they saw, there’s a video on the launch post from today: https://go.nasa.gov/2HCNQH3 -ECF

Although both the GBM and LAT teams had been preparing for years to detect a gamma-ray burst in coincidence with a gravitational wave, we were still very surprised on August 17, 2017, when it happened. https://go.nasa.gov/2yrgqd8 -JLR

As far as I understood, the Fermi's extended mission is coming to an end. Is the Fermi mission going to be extended again?

Fermi has submitted successful extension proposals to NASA three times before and will submit a proposal again next year for another 3 years of great gamma-ray science. NASA reviews the operating missions every three years. - EAH

Could you explain more about how these antimatter particles were found and can matter antimatter collisions really be the future for Interstellar travel?

Matter-antimatter collisions certainly produce a lot of energy, much of which comes in the form of gamma rays. The problem with using it for interstellar travel would be producing the antimatter in the first place and then containing it (which requires magnetic fields, since the antimatter would interact with any normal matter). The needed magnetic fields would require massive structures, and that would make the whole process impractical for a spaceship. You can get some idea of the problem by reading about efforts at CERN to transport a tiny quantity of antimatter: https://home.cern/about/updates/2018/03/making-antimatter-transportable -DJT

The antimatter particles seen by Fermi’s Gamma-ray Burst Monitor (GBM) were positrons, the antiparticles of electrons. Terrestrial Gamma-ray Flashes (TGFs) are generated as a result of collisions between air molecules and relativistic electrons generated in the electric fields of thunderstorms. Sometimes, these collisions produce secondary electrons and positrons, which annihilate and follow the geomagnetic field lines that surround Earth.

Sometimes, these positrons intersect with Fermi’s orbit and we detect these as electron-beamed events in the GBM detectors, which are generally longer than your average TGF (>1 millisecond, compared to <1 millisecond TGFs). The signature that indicates electron-positron annihilation is the detection of gamma rays with a very specific energy. That signature was seen by the GBM.

More information on these antimatter beams can be found here: https://svs.gsfc.nasa.gov/10706 - OJR

can we use this gamma rays as alternative source of energy by storing it?

No, unfortunately that is not possible. The flux of gamma-rays is actually extremely low compared to other forms of light. Even the brightest steady source in the sky typical provides only a few photons per hour. - JLR

How do you think the research your team is doing with Fermi will allow us to make greater steps in trying to resolve the issues between Einstein's theories related to large space bodies and the laws of quantum mechanics?

Fermi’s instruments have already helped with this important question by confirming that the speed of light is the same at all the energies we measure, contrary to some ideas about quantum gravity. Gamma-ray bursts provide a valuable way to test such theories, so we have to wait for more of these that have the right characteristics to make progress. - DJT

Exactly how far out is this distant galaxy? Are there plans to go further? If so, how much farther is expected and what type of things are you expecting to find?

Assuming you’re asking about the binary neutron star merger detected in gravitational waves and light, it was 40 megaparsecs or 130 million light years away. This is actually quite nearby in terms of gamma-ray bursts. Fermi has detected gamma-ray bursts both nearby and out into the very distant Universe. The gravitational wave detectors, LIGO and Virgo, should be able to detect neutron star mergers approximately 3 times farther than GW170817 in the observing run next year. We hope to detect more binary neutron star mergers, and perhaps also neutron star-black hole mergers, in both gravitational waves and light. - JLR