View source for NuSTAR

{{Short description|NASA X-ray space telescope of the Explorer program}}
{{Use American English|date=December 2021}}
{{Use dmy dates|date=January 2020}}
{{Infobox spaceflight
| name              = NuSTAR
| names_list        = Explorer 93<br/>Nuclear Spectroscopic Telescope Array<br/>SMEX-11
| image             = NuSTAR spacecraft model.png
| image_caption     = NuSTAR (Explorer 93) satellite
| image_size        = 300px

| mission_type      = [[X-ray astronomy satellite|X-ray astronomy]]
| operator          = [[NASA]]{{\}}[[JPL]]
| COSPAR_ID         = 2012-031A
| SATCAT            = 38358
| website           = {{url|http://www.nustar.caltech.edu/}}
| mission_duration  = 2 years (planned)<br/>{{time interval|13 June 2012 16:00:37|show=ymd|sep=,}} ''(in progress)''

| spacecraft        = Explorer XCIII
| spacecraft_type   = Nuclear Spectroscopic Telescope Array
| spacecraft_bus    = [[Star Bus|LEOStar-2]]
| manufacturer      = [[Orbital ATK]] (formerly [[Orbital Sciences Corporation]] and [[Alliant Techsystems|ATK Space Components]])
| launch_mass       = {{cvt|350|kg}}<ref name="NuSTARPressKit">{{cite web|url=http://www.jpl.nasa.gov/news/press_kits/NuSTARpresskit.pdf|title=Nuclear Spectroscopic Telescope Array (NuSTAR)|website=[[Jet Propulsion Laboratory]]|date=June 2012 |access-date=16 June 2012}}</ref>
| payload_mass      = {{cvt|171|kg}}
| dimensions        = {{cvt|1.2|xx|10.9|m}}
| power             = 750 [[watt]]s<ref name="eoPortal">{{cite web|url=https://directory.eoportal.org/web/eoportal/satellite-missions/n/nustar|title=NuSTAR (Nuclear Spectroscopic Telescope Array)|publisher=European Space Agency|access-date=2 July 2015}}</ref>

| launch_date       = 13 June 2012, 16:00:37 [[Coordinated Universal Time|UTC]]<ref name="SFN">{{cite web|url=http://www.spaceflightnow.com/pegasus/nustar/status.html|title=Mission Status Center |publisher=Spaceflight Now|first=Justin|last=Ray|access-date=13 June 2012}}</ref>
| launch_rocket     = [[Pegasus (rocket)|Pegasus XL]] (F41)
| launch_site       = [[Kwajalein Atoll]], ''[[Stargazer (aircraft)|Stargazer]]''
| launch_contractor = [[Orbital Sciences Corporation]]

| entered_service   = 
| deactivated       = 
| destroyed         = 
| last_contact      =

| orbit_reference   = [[Geocentric orbit]]
| orbit_regime      = [[Near-equatorial orbit]]
| orbit_periapsis   = {{cvt|596.6|km}}
| orbit_apoapsis    = {{cvt|612.6|km}}
| orbit_inclination = 6.027°
| orbit_period      = 96.8 minutes
| apsis             = gee

| telescope_type         = [[Wolter telescope|Wolter type I]]
| telescope_diameter     = 
| telescope_focal_length = {{cvt|10.15|m}}<ref name="eoPortal"/>
| telescope_area         = 9 keV: {{cvt|847|cm2}}<br/>78 keV: {{cvt|60|cm2}}
| telescope_wavelength   = 3–79 keV
| telescope_resolution   = 9.5 arcseconds
| instruments            = Dual X-ray telescope

| programme         = '''Explorer program'''
| previous_mission  = [[Interstellar Boundary Explorer|IBEX]] (Explorer 92)
| next_mission      = [[Interface Region Imaging Spectrograph|IRIS]] (Explorer 94)
}}

'''NuSTAR''' ('''Nuclear Spectroscopic Telescope Array''', also named '''Explorer 93''' and '''SMEX-11''') is a [[NASA]] space-based [[X-ray]] telescope that uses a [[Conical intersection|conical approximation]] to a [[Wolter telescope]] to focus high energy X-rays from [[astrophysics|astrophysical]] sources, especially for [[nuclear spectroscopy]], and operates in the range of 3 to 79 [[Electronvolt|keV]].<ref>{{cite web|url=https://www.nustar.caltech.edu/page/about|title=About|series=NuSTAR|publisher=Caltech|access-date=15 October 2017}}</ref>

NuSTAR is the eleventh mission of NASA's [[Small Explorer]] (SMEX-11) satellite program and the first space-based direct-imaging [[X-ray telescope]] at energies beyond those of the [[Chandra X-ray Observatory]] and [[XMM-Newton]]. It was successfully launched on 13 June 2012, having previously been delayed from 21 March 2012 due to software issues with the launch vehicle.<ref name="NuSTAR">{{cite web|url=https://www.nasa.gov/mission_pages/nustar/news/nustar20120316.html|title=Launch of NASA's NuSTAR Mission Postponed|publisher=NASA|date=16 March 2012|access-date=15 October 2017|archive-date=22 April 2019|archive-url=https://web.archive.org/web/20190422103625/https://www.nasa.gov/mission_pages/nustar/news/nustar20120316.html|url-status=dead}} {{PD-notice}}</ref><ref name="nustar-launch">{{cite press release|title=NASA Selects Explorer Mission Proposals for Feasibility Studies (03-353)|url=http://www.nasa.gov/mission_pages/nustar/news/nustar20120316.html|access-date=17 March 2012|archive-date=11 November 2020|archive-url=https://web.archive.org/web/20201111220337/http://www.nasa.gov/mission_pages/nustar/news/nustar20120316.html|url-status=dead}} {{PD-notice}}</ref>

The mission's primary scientific goals are to conduct a deep survey for [[black hole]]s a billion times more massive than the Sun, to investigate how particles are accelerated to very high energy in [[active galaxy|active galaxies]], and to understand how the elements are created in the explosions of massive stars by imaging [[supernova remnant]]s.

Having completed a two-year primary mission,<ref>{{cite news |last1=Presto |first1=Suzanne |title=Black hole bends light, space, time&nbsp;– and NASA's NuSTAR can see it all unfold |department=CNN Business |url=https://www.cnn.com/2014/08/12/tech/black-hole-nasa-nustar/index.html |access-date=28 November 2022 |work=CNN |date=13 August 2014 |language=en}}</ref> NuSTAR is in its {{age in years|13 June 2012|format=ordinal}} year of operation.

== History ==
NuSTAR's predecessor, the High Energy Focusing Telescope (HEFT), was a balloon-borne version that carried telescopes and detectors constructed using similar technologies. In February 2003, NASA issued an Explorer program Announcement of Opportunity (AoO). In response, NuSTAR was submitted to NASA in May 2003, as one of 36 mission proposals vying to be the tenth and eleventh Small Explorer missions.<ref name="NuSTAR"/> In November 2003, NASA selected NuSTAR and four other proposals for a five-month implementation feasibility study.

In January 2005, NASA selected NuSTAR for flight pending a one-year feasibility study.<ref>{{cite web|url=http://www.nasa.gov/home/hqnews/2005/jan/HQ_05026_exp_mission.html|title=NASA Selects Small Explorer Mission (05-026)|publisher=NASA|date=26 January 2005|access-date=20 July 2011}} {{PD-notice}}</ref> The program was cancelled in February 2006 as a result of cuts to science in NASA's 2007 budget. On 21 September 2007, it was announced that the program had been restarted, with an expected launch in August 2011, though this was later delayed to June 2012.<ref name="nustar-launch"/><ref>{{cite web|title=NASA Restarts Telescope Mission to Detect Black Holes (07-198)|url=http://www.nasa.gov/home/hqnews/2007/sep/HQ_07198_NuSTAR.html|publisher=NASA|date=21 September 2007|access-date=20 July 2011|archive-date=23 March 2021|archive-url=https://web.archive.org/web/20210323141731/https://www.nasa.gov/home/hqnews/2007/sep/HQ_07198_NuSTAR.html|url-status=dead}} {{PD-notice}}</ref><ref>{{cite web|title=NASA Restarts Telescope Mission to Detect Black Holes|url=http://www.nasa.gov/centers/jpl/news/nustar-20070921_prt.htm|publisher=NASA (JPL)|date=21 September 2007|access-date=20 July 2011|archive-date=13 September 2016|archive-url=https://web.archive.org/web/20160913024208/http://www.nasa.gov/centers/jpl/news/nustar-20070921_prt.htm|url-status=dead}} {{PD-notice}}</ref><ref>{{cite news|title=NASA Plans Black Hole Finder|url=http://www.space.com/scienceastronomy/070921_nustar_restart.html|publisher=Space.com|date=21 September 2007|access-date=20 July 2011}}</ref>

The principal investigator is [[Fiona A. Harrison]] of the [[California Institute of Technology]] (Caltech). Other major partners include the [[Jet Propulsion Laboratory]] (JPL), [[University of California, Berkeley]], [[Technical University of Denmark]] (DTU), [[Columbia University]], [[Goddard Space Flight Center]] (GSFC), [[Stanford University]], [[University of California, Santa Cruz]], [[Sonoma State University]], [[Lawrence Livermore National Laboratory]], and the [[Italian Space Agency]] (ASI). NuSTAR's major industrial partners include [[Orbital Sciences Corporation]] and [[Alliant Techsystems|ATK Space Components]].

== Launch ==
NASA contracted with Orbital Sciences Corporation to launch NuSTAR (mass {{cvt|350|kg}})<ref name=nasa>{{cite web |url=http://www.nasa.gov/mission_pages/nustar/main/index.html|title=NuSTAR|date=18 February 2015|publisher=NASA}} {{PD-notice}}</ref> on a [[Pegasus (rocket)|Pegasus XL]] launch vehicle on 21 March 2012.<ref name="nustar-launch"/> It had earlier been planned for 15 August 2011, 3 February 2012, 16 March 2012, and 14 March 2012.<ref>{{cite web|first=Jon|last=Nelson |url=http://www.jpl.nasa.gov/news/features.cfm?feature=2306 |title=NASA Approves X-ray Space Mission|publisher=NASA (JPL)|date=4 September 2009|access-date=20 July 2011|archive-date=6 February 2012 |archive-url=https://web.archive.org/web/20120206202117/http://www.jpl.nasa.gov/news/features.cfm?feature=2306|url-status=dead}} {{PD-notice}}</ref> After a launch meeting on 15 March 2012, the launch was pushed further back to allow time to review flight software used by the launch vehicle's flight computer.<ref>{{cite web|url=http://www.nasa.gov/mission_pages/nustar/news/nustar20120316.html|title=Launch of NASA's NuSTAR Mission Postponed|publisher=NASA|date=16 March 2012|access-date=31 May 2012|archive-date=11 November 2020|archive-url=https://web.archive.org/web/20201111220337/http://www.nasa.gov/mission_pages/nustar/news/nustar20120316.html|url-status=dead}}</ref> The launch was conducted successfully at 16:00:37 [[Coordinated Universal Time|UTC]] on 13 June 2012<ref name="SFN"/> about {{cvt|117|mi}} south of [[Kwajalein Atoll]].<ref>{{cite web |url=http://www.orbital.com/NewsInfo/release.asp?prid=685|title=NASA Selects Orbital's Pegasus Rocket to Launch NuSTAR Space Science Satellite |publisher=Orbital|date=18 February 2009|access-date=20 July 2011}}</ref> The Pegasus launch vehicle was dropped from the [[Stargazer (aircraft) |L-1011 'Stargazer' aircraft]].<ref name=nasa/><ref>{{cite web |url=http://www.nbcnews.com/id/47798276|archive-url=https://web.archive.org/web/20130410160239/http://www.nbcnews.com/id/47798276/|url-status=dead|archive-date=10 April 2013|first=Clara|last=Moskowitz |title=NASA blasts NuSTAR telescope into orbit to hunt black holes |publisher=NBC News|date=13 June 2012|access-date=15 June 2012}}</ref>

On 22 June 2012, it was confirmed that the {{cvt|10|m}} mast was fully deployed.<ref>{{cite news|url=http://www.universetoday.com/95927/nustar-successfully-deploys-huge-mast/|title=NuSTAR Successfully Deploys Huge Mast|publisher=Universe Today|date=22 June 2012}}</ref>

== Optics ==
{{multiple image |align=left |direction=horizontal |total_width=380
 |image1=NuSTAR's Russian Doll-like Mirrors (PIA15631).jpg|caption1=NuSTAR's nested X-ray mirrors
 |image2=Xray telescope lens.svg|caption2=Focusing X-rays with a Wolter Type-1 optical system
}}

Unlike visible light telescopes – which employ mirrors or lenses working with normal incidence – NuSTAR has to employ grazing incidence optics to be able to focus X-rays. For this two conical approximation [[Wolter telescope]] design optics with {{cvt|10.15|m}} focal length are held at the end of a long [[Deployable structure|deployable]] mast. A laser [[metrology]] system is used to determine the exact relative positions of the optics and the focal plane at all times, so that each detected photon can be mapped back to the correct point on the sky even if the optics and the focal plane move relative to one another during an exposure.

Each focusing optic consists of 133 concentric shells. One particular innovation enabling NuSTAR is that these shells are coated with [[depth-graded multilayer coating|depth-graded multilayers]] (alternating atomically thin layers of a high-density and low-density material); with NuSTAR's choice of Pt/SiC and W/Si multilayers, this enables reflectivity up to 79&nbsp;keV (the platinum [[K-edge]] energy).<ref>{{cite web |url=http://www.nustar.caltech.edu/about-nustar/instrumentation/optics|title=NuSTAR optics|url-status=dead|archive-url=https://web.archive.org/web/20120520174439/http://www.nustar.caltech.edu/about-nustar/instrumentation/optics|archive-date=20 May 2012}}</ref><ref name="optics-overview">{{Cite conference |editor1-last=Arnaud |editor1-first=Monique |editor2-last=Murray |editor2-first=Stephen S. |editor3-last=Takahashi |editor3-first=Tadayuki |last1=Hailey |first1=Charles J. |last2=An |first2=HongJun |last3=Blaedel |first3=Kenneth L. |last4=Brejnholt |first4=Nicolai F. |last5=Christensen |first5=Finn E. |last6=Craig |first6=William W. |last7=Decker |first7=Todd A. |last8=Doll |first8=Melanie |last9=Gum |first9=Jeff |last10=Koglin |first10=Jason E. |last11=Jensen |first11=Carsten P. |last12=Hale |first12=Layton |last13=Mori |first13=Kaya |last14=Pivovaroff |first14=Michael J. |last15=Sharpe |first15=Marton |last16=Stern |first16=Marcela |last17=Tajiri |first17=Gordon |last18=Zhang |first18=William W. |date=29 July 2010 |title=The Nuclear Spectroscopic Telescope Array (NuSTAR): optics overview and current status |url=http://www.nustar.caltech.edu/uploads/files/hailey_spie2010_7732_28.pdf |conference=Space Telescopes and Instrumentation 2010: Ultraviolet to Gamma Ray |location=San Diego, California, United States |publisher=[[SPIE]] |volume=7732 |page=77320T |bibcode=2010SPIE.7732E..0TH |doi=10.1117/12.857654 |archive-url=https://web.archive.org/web/20110719160220/http://www.nustar.caltech.edu/uploads/files/hailey_spie2010_7732_28.pdf |archive-date=19 July 2011 |display-authors=5 |s2cid=121831705 |url-status=dead }}</ref>

The optics were produced, at [[Goddard Space Flight Center]], by heating thin ({{cvt|210|µm}}) sheets of flexible glass in an oven so that they slumped over precision-polished cylindrical quartz [[mandrel]]s of the appropriate radius. The [[coating]]s were applied by a group at the [[Danish Technical University]].

The shells were then assembled, at the [[Nevis Laboratories]] of Columbia University, using graphite spacers machined to constrain the glass to the conical shape, and held together by epoxy. There are 4680 mirror segments in total (the 65 inner shells each comprise six segments and the 65 outer shells twelve; there are upper and lower segments to each shell, and there are two telescopes); there are five spacers per segment. Since the epoxy takes 24 hours to cure, one shell is assembled per day – it took four months to build up one optic.

The actual telescope consists of two separate Focal Plane Modules (FPMs) labelled FPMA and FPMB. These two FPMs are built to be similar, though they are not identical. Depending on the source and on the observation, one of the modules will usually report higher counts. This is corrected for in the science results step, usually by apply a constant multiplier during spectral fitting and light curve analysis.<ref>{{Cite web |last1=Forster |first1=Karl |last2=Grefenstette |first2=Brian |last3=Madsen |first3=Kristin |title=NuSTAR DATA ANALYSIS – Quickstart Guide |url=https://heasarc.gsfc.nasa.gov/docs/nustar/analysis/nustar_quickstart_guide.pdf |website=HEASARC |publisher=NuSTAR Science Operations Center, California Institute of Technology}}</ref>

The expected point spread function for the flight mirrors is 43 [[Minute and second of arc|arcseconds]], giving a spot size of about two millimeters at the focal plane; this is unprecedentedly good resolution for focusing hard X-ray optics, though it is about one hundred times worse than the best resolution achieved at longer wavelengths by the [[Chandra X-ray Observatory]].

== Detectors ==
[[File:NuSTAR detector.JPG|thumb|upright=1.0|left|One of NuSTAR's two detectors]]
[[File:Nustar mast deployed.jpg|thumb|upright=1.0|right|NuSTAR's mast deployed on Earth; the inset is looking down the structure]]

Each focusing optic has its own focal plane module, consisting of a solid state [[cadmium zinc telluride]] (CdZnTe) pixel detector<ref name=Harrison2010>{{cite book|last1=Harrison|first1=Fiona |title=Semiconductor radiation detection systems|publisher=CRC Press|location=Boca Raton, Florida|isbn=9781439803851|date=21 May 2010}}</ref> surrounded by a [[caesium iodide|cesium iodide]] (CsI) [[Electronic anticoincidence|anti-coincidence shield]]. One detector unit — or focal plane — comprises four (two-by-two) detectors, manufactured by [http://www.evproducts.com eV Products]. Each detector is a rectangular crystal of dimension {{cvt|20|xx|20|mm}} and thickness ~{{cvt|2|mm}} that have been gridded into {{cvt|32|xx|32|xx|0.6|mm}} [[pixel]]s (each pixel subtending 12.3 arcseconds) and provides a total of 12 arcminutes [[field of view]] (FoV) for each focal plane module.

The cadmium zinc telluride (CdZnTe) detectors are [[state of the art]] room temperature [[semiconductor]]s that are very efficient at turning [[High Energy Photon Source|high energy photons]] into [[electron]]s. The electrons are digitally recorded using custom [[application-specific integrated circuit]]s (ASICs) designed by the NuSTAR [[California Institute of Technology]] (CalTech) Focal Plane Team. Each pixel has an independent discriminator and individual X-ray interactions trigger the readout process. On-board processors, one for each telescope, identify the row and column with the largest pulse height and read out pulse height information from this pixel as well as its eight neighbors. The event time is recorded to an accuracy of 2 μs relative to the on-board clock. The event location, energy, and depth of interaction in the detector are computed from the nine-pixel signals.<ref>{{cite journal|last1=Rana|first1=Vikram|editor1-first=Oswald H.|editor1-last=Siegmund|title=Development of focal plane detectors for the Nuclear Spectroscopic Telescope Array (NuSTAR) mission|journal=Proc. SPIE|date=2009|volume=7435|page=743503|doi=10.1117/12.825418|series=UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XVI |url=https://authors.library.caltech.edu/84176/1/743503.pdf|bibcode=2009SPIE.7435E..03R|s2cid=122500874}}</ref><ref name=Kitaguchi2011>{{cite journal|last1=Kitaguchi|first1=Takao|editor1-first=Oswald H. |editor1-last=Siegmund|title=Spectral calibration and modeling of the NuSTAR CdZnTe pixel detectors|journal=Proc. SPIE|date=2011|volume=8145|page=814507|doi=10.1117/12.896972|arxiv=1109.0378|series=UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XVII|bibcode=2011SPIE.8145E..07K|s2cid=12785111}}</ref>

The focal planes are shielded by [[Caesium iodide|cesium iodide]] (CsI) crystals that surround the detector housings. The crystal shields, grown by [[Saint-Gobain]], register high energy photons and cosmic rays which cross the focal plane from directions other than the along the NuSTAR optical axis. Such events are the primary background for NuSTAR and must be properly identified and subtracted in order to identify high energy photons from cosmic sources. The NuSTAR active shielding ensures that any CZT detector event coincident with an active shield event is ignored.

== Major scientific results ==
NuSTAR has demonstrated its versatility, opening the way to many new discoveries in a wide variety of areas of astrophysical research since its launch.

=== Spin measurement of a supermassive black hole ===
In February 2013, NASA revealed that NuSTAR, along with the [[XMM-Newton]] space observatory, has measured the spin rate of the [[supermassive black hole]] at the center of the galaxy [[NGC 1365]].<ref name=":0">{{cite news|url=http://www.nasa.gov/mission_pages/nustar/news/nustar20130227.html|title=NASA's NuSTAR Helps Solve Riddle of Black Hole Spin|publisher=NASA|date=27 February 2013|access-date=3 March 2013|archive-date=3 December 2017|archive-url=https://web.archive.org/web/20171203021016/https://www.nasa.gov/mission_pages/nustar/news/nustar20130227.html|url-status=dead}} {{PD-notice}}</ref> By measuring the frequency change of X-ray light emitted from the black hole corona, NuSTAR was able to view material from the corona be drawn closer to the [[event horizon]]. This caused inner portions of the black hole's [[accretion disk]] to be illuminated with X-rays, allowing this elusive region to be studied by astronomers for spin rates.<ref name=":0" />

{{multiple image |align=center |direction=horizontal |total_width=900
|image1=Pointing X-ray Eyes at our Resident Supermassive Black Hole.jpg|caption1=NuSTAR has captured these first, focused views of the supermassive black hole at the heart of our galaxy in high-energy X-ray light.

|image2=Black Holes - Monsters in Space.jpg|caption2=Black hole with corona, an X-ray source<br/>(artist's concept)<ref name="NASA-20140812">{{cite news|url=http://www.jpl.nasa.gov/news/news.php?release=2014-273|title=NASA's NuSTAR Sees Rare Blurring of Black Hole Light|publisher=NASA (JPL)|date=12 August 2014|access-date=12 August 2014}} {{PD-notice}}</ref>

|image3=PIA18467-NuSTAR-Plot-BlackHole-BlursLight-20140812.png|caption3=Blurring of X-rays near black hole<br/>(NuSTAR; 12 August 2014)<ref name="NASA-20140812"/>
}}

=== Tracing radioactivity in a supernova remnant ===
[[File:PIA20061_-_Andromeda_in_High-Energy_X-rays,_unannotated.jpg|thumb|upright=1.0|right|Andromeda]]

One of NuSTAR's main goals is to characterize stars' explosions by mapping the radioactive material in a [[supernova remnant]]s. The NuSTAR map of [[Cassiopeia A]] shows the [[Isotopes of titanium|titanium-44]] isotope concentrated in clumps at the remnant's center and points to a possible solution to the mystery of how the star exploded. When researchers simulate supernova blasts with computers, as a massive star dies and collapses, the main shock wave often stalls and the star fails to shatter. The latest findings strongly suggest the exploding star literally sloshed around, re-energizing the stalled shock wave and allowing the star to finally blast off its outer layers.<ref name=CasANews>{{cite news|title=NASA's NuSTAR Untangles Mystery of How Stars Explode|url=http://www.jpl.nasa.gov/news/news.php?release=2014-054 |access-date=24 April 2015|publisher=JPL|date=19 February 2014}} {{PD-notice}}</ref>

=== Nearby supermassive black holes ===
In January 2017, researchers from [[Durham University]] and the [[University of Southampton]], leading a coalition of agencies using NuSTAR data, announced the discovery of supermassive black holes at the center of nearby galaxies [[NGC 1448]] and IC 3639.<ref name="nasa20170107">{{cite web|url=https://www.nasa.gov/feature/jpl/black-holes-hide-in-our-cosmic-backyard|title=Black Holes Hide in Our Cosmic Backyard|publisher=NASA|date=7 January 2017|access-date=7 January 2017}} {{PD-notice}}</ref><ref name="Annuar2017">{{cite journal|title=A New Compton-thick AGN in our Cosmic Backyard: Unveiling the Buried Nucleus in NGC 1448 with NuSTAR|journal=The Astrophysical Journal|first1=A.|last1=Annuar|first2=D. M.|last2=Alexander|first3=P.|last3=Gandhi|first4=G. B.|last4=Lansbury|first5=D.|last5=Asmus|display-authors=et al.|date=January 2017|bibcode=2017ApJ...836..165A|arxiv=1701.00497|doi=10.3847/1538-4357/836/2/165|volume=836|issue=2|page=165|s2cid=11258638 |doi-access=free }}</ref><ref name="Boorman2016">{{cite journal|title=IC 3639—a New Bona Fide Compton-Thick AGN Unveiled by NuSTAR|journal=The Astrophysical Journal|first1=Peter G.|last1=Boorman|first2=P.|last2=Gandhi|first3=D. M.|last3=Alexander|first4=A.|last4=Annuar|first5=D. R. |last5=Ballantyne|display-authors=et al.|volume=833|issue=2|at=245|date=December 2016|doi=10.3847/1538-4357/833/2/245|bibcode=2016ApJ...833..245B|arxiv=1610.08997|s2cid=36679784 |doi-access=free }}</ref>

=== Measurement of temperature variations of AGN wind ===
In March 2nd of 2017, NuSTAR published an article to Nature detailing observations of wind temperature variations around [[Active galactic nucleus|AGN]] [[IRAS 13224-3809|IRAS 13224−3809]]. By detecting periodic absences of absorption lines in the X-ray spectrum from the accretion disk winds, NuSTAR and [[XMM-Newton]] observed heating and cooling cycles of the relativistic winds leaving the [[accretion disk]].<ref>{{Cite journal |last1=Parker |first1=Michael L. |last2=Pinto |first2=Ciro |last3=Fabian |first3=Andrew C. |last4=Lohfink |first4=Anne |last5=Buisson |first5=Douglas J. K. |last6=Alston |first6=William N. |last7=Kara |first7=Erin |last8=Cackett |first8=Edward M. |last9=Chiang |first9=Chia-Ying |last10=Dauser |first10=Thomas |last11=De Marco |first11=Barbara |last12=Gallo |first12=Luigi C. |last13=Garcia |first13=Javier |last14=Harrison |first14=Fiona A. |last15=King |first15=Ashley L. |date=2017-03-02 |title=The response of relativistic outflowing gas to the inner accretion disk of a black hole |url=http://dx.doi.org/10.1038/nature21385 |journal=Nature |volume=543 |issue=7643 |pages=83–86 |doi=10.1038/nature21385 |pmid=28252065 |arxiv=1703.00071 |bibcode=2017Natur.543...83P |s2cid=4394261 |issn=0028-0836}}</ref><ref>{{Cite web |title=Temperature Swings of Black Hole Winds Measured for First Time |url=https://nustar.caltech.edu/news/nustar170301 |access-date=2023-04-24 |website=NuSTAR}}</ref>

=== Detection of light reflecting behind a black hole ===
[[File:Black hole representation.gif|alt=This representation of a black hole shows both sides of the accretion disk: in this case, gas above and below the black event horizon is from behind the black hole, while gas flowing in front is from the observers side.|thumb|This representation of a black hole shows both sides of the accretion disk: in this case, gas above and below the black event horizon is from behind the black hole, while gas flowing in front is from the observers side.]]
NuSTAR and [[XMM-Newton]] detected X-rays emitted behind the supermassive black hole within [[Seyfert galaxy|Seyfert 1 galaxy]] I Zwicky 1. Upon studying the flashes of light emitted by the corona of the black hole, researchers noticed that some detected light arrived to the detector later than the rest, with a corresponding [[Redshift|change in frequency]]. The Stanford University team of scientists that led the study concluded that this change was directly attributable to radiation from the flash reflecting off of the accretion disk on the opposing side of the black hole. The path of this reflected light was bent by the high spacetime curvature, directed to the detector after the initial flash.<ref>{{Cite web |title=NuSTAR and XMM-Newton See Light Echo from Behind a Black Hole |url=https://nustar.caltech.edu/news/129 |access-date=2023-04-24 |website=NuSTAR}}</ref><ref>{{Cite journal |last1=Wilkins |first1=D. R. |last2=Gallo |first2=L. C. |last3=Costantini |first3=E. |last4=Brandt |first4=W. N. |last5=Blandford |first5=R. D. |date=2021-07-28 |title=Light bending and X-ray echoes from behind a supermassive black hole |url=http://dx.doi.org/10.1038/s41586-021-03667-0 |journal=Nature |volume=595 |issue=7869 |pages=657–660 |doi=10.1038/s41586-021-03667-0 |pmid=34321670 |issn=0028-0836|arxiv=2107.13555 |bibcode=2021Natur.595..657W |s2cid=236493644 }}</ref>

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=== Ultra-luminous neutron star violating the Eddington limit ===
[[File:Neutron Star simulation.png|alt=A neutron star surrounded by an accretion disk. Disk material that falls on to the surface of the star will release x-rays as radiation, contributing to the observed luminosity. When this luminosity is greater than what the Eddington limit predicts from the star mass, this object is known as a Ultraluminous X-ray source (ULX).|thumb|A neutron star surrounded by an accretion disk. Disk material that falls on to the surface of the star will release x-rays as radiation, contributing to the observed luminosity. When this luminosity is greater than what the Eddington limit predicts from the star mass, this object is known as a Ultraluminous X-ray source (ULX).]]
In April 6th of 2023, the NuSTAR team confirmed that neutron star [[M82 X-2]] was emitting more radiation than was physically thought possible due to the [[Eddington luminosity|Eddington limit]], officially labeling it as an [[Ultraluminous X-ray source]] (ULX).<ref>{{Cite web |title=NASA Study Helps Explain Limit-Breaking Ultra-Luminous X-Ray Sources |url=https://nustar.caltech.edu/news/nustar230406 |access-date=2023-04-24 |website=NuSTAR}}</ref><ref>{{Cite journal |last1=Bachetti |first1=Matteo |last2=Heida |first2=Marianne |display-authors=1 |date=October 2022 |title=Orbital decay in M82 X-2 |journal=The Astrophysical Journal |volume=937 |issue=2 |pages=125 |doi=10.3847/1538-4357/ac8d67|arxiv=2112.00339 |bibcode=2022ApJ...937..125B |hdl=2299/25784 |hdl-access=free |doi-access=free }}</ref>

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== See also ==
{{Portal|Astronomy|Physics|Spaceflight}}
* [[Explorer program]]
* [[Gravity and Extreme Magnetism]], hard X-ray telescope measuring polarization (cancelled 2012)
* [[James Webb Space Telescope]], infrared telescope launched on 25 December 2021
* [[X-Ray Imaging and Spectroscopy Mission|XRISM]], joint Japanese and American X-ray telescope
* [[List of X-ray space telescopes]]

== References ==
{{Reflist|30em}}

== External links ==
{{commons category|NuSTAR}}
* [https://science.nasa.gov/mission/nustar NuSTAR website] at nasa.gov
* [http://www.nustar.caltech.edu/ NuSTAR website] at caltech.edu
* [https://www.youtube.com/watch?v=bRd7vq5HIhM Building, Launching, and Using the NuSTAR X-ray Observatory], talk by Melania Nynka of the MIT Kavli Institute for Astrophysics and Space Research

;Further reading
* {{cite journal|url=http://magazine.columbia.edu/sites/dev.magazine.columbia.edu/files/pdf/xraySpecs.pdf|title=X-Ray Specs|journal=Columbia University|first=David J.|last=Craig|pages=24–27|date=Spring 2010}}
* {{cite conference |conference=Space Telescopes and Instrumentation 2010: Ultraviolet to Gamma Ray |volume=7732|page=77320S |first1=Fiona A. |last1=Harrison |first2=Steve |last2=Boggs |first3=Finn |last3=Christensen |first4=William |last4=Craig |first5=Charles |last5=Hailey |first6=Daniel |last6=Stern |first7=William |last7=Zhang |first8=Lorella |last8=Angelini |first9=HongJun |last9=An |first10=Varun |last10=Bhalerao |first11=Nicolai |last11=Brejnholt |first12=Lynn |last12=Cominsky |first13=W. Rick |last13=Cook |first14=Melania |last14=Doll |first15=Paolo |last15=Giommi |first16=Brian |last16=Grefenstette |first17=Allan |last17=Hornstrup |first18=Vicky |last18=Kaspi |first19=Yunjin |last19=Kim |first20=Takeo |last20=Kitaguchi |first21=Jason |last21=Koglin |first22=Carl Christian |last22=Liebe |first23=Greg |last23=Madejski |first24=Kristin Kruse |last24=Madsen |first25=Peter |last25=Mao |first26=David |last26=Meier |first27=Hiromasa |last27=Miyasaka |first28=Kaya |last28=Mori |first29=Matteo |last29=Perri |first30=Michael |last30=Pivovaroff |first31=Simonetta |last31=Puccetti |first32=Vikram |last32=Rana |first33=Andreas |last33=Zoglauer |title=The Nuclear Spectroscopic Telescope Array (NuSTAR) |editor1-first=Monique |editor1-last=Arnaud |editor2-first=Stephen S. |editor2-last=Murray |editor3-first=Tadayuki |editor3-last=Takahashi |display-authors=5 |date=29 July 2010 |doi=10.1117/12.858065 |arxiv=1008.1362 |url=http://www.nustar.caltech.edu/uploads/files/harrison_spie2010_7732_27.pdf |url-status=dead |archive-url=https://web.archive.org/web/20110717131423/http://www.nustar.caltech.edu/uploads/files/harrison_spie2010_7732_27.pdf|archive-date=17 July 2011 |bibcode=2010SPIE.7732E..0SH|s2cid=121923451}}

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