Potentially hazardous object
{{Short description|Hazardous near-Earth asteroid or comet}}
Image:Toutatis.jpg is listed as a potentially hazardous near-Earth asteroid, yet poses no immediate threat to Earth. (Radar image taken by GDSCC in 1996.)]]
A potentially hazardous object (PHO) is a near-Earth object – either an asteroid or a comet – with an orbit that can make close approaches to the Earth and which is large enough to cause significant regional damage in the event of impact. They are conventionally defined as having a minimum orbit intersection distance with Earth of less than {{convert|0.05|AU|LD|lk=on|sigfig=3|abbr=off}} and an absolute magnitude of 22 or brighter, the latter of which roughly corresponds to a size larger than 140 meters. More than 99% of the known potentially hazardous objects are no impact threat over the next 100 years. {{As of|2025|02}}, just 21 of the known potentially hazardous objects listed on the Sentry Risk Table could not be excluded as potential threats over the next hundred years. Over hundreds if not thousands of years though, the orbits of some "potentially hazardous" asteroids can evolve to live up to their namesake.
Most of these objects are potentially hazardous asteroids (PHAs), and a few are comets. {{As of|2022|11}} there are 2,304 known PHAs (about 8% of the total near-Earth population), of which 153 are estimated to be larger than one kilometer in diameter (see list of largest PHAs below).{{efn|name=note-diameter-estimates}} Most of the discovered PHAs are Apollo asteroids (1,965) and fewer belong to the group of Aten asteroids (185).
A potentially hazardous object can be known not to be a threat to Earth for the next 100 years or more, if its orbit is reasonably well determined. Potentially hazardous asteroids with some threat of impacting Earth in the next 100 years are listed on the Sentry Risk Table. {{As of|2022|09}}, only 17 potentially hazardous asteroids are listed on the Sentry Risk Table. Most potentially hazardous asteroids are ruled out as hazardous to at least several hundreds of years when their competing best orbit models are sufficiently constrained, but recent discoveries whose orbital constraints are little-known have divergent or incomplete mechanical models until observation yields further data. After several astronomical surveys, the number of known PHAs has increased tenfold since the end of the 1990s (see bar charts below). The Minor Planet Center's website List of the Potentially Hazardous Asteroids also publishes detailed information for these objects.
In May 2021, NASA astronomers reported that 5 to 10 years of preparation may be needed to avoid a potential impactor, as most recently based on a simulated exercise conducted by the 2021 Planetary Defense Conference.{{cite news |last1=McFall-Johnsen |first1=Morgan |last2=Woodward |first2=Aylin |title=A NASA simulation revealed that 6 months' warning isn't enough to stop an asteroid from hitting Earth. We'd need 5 to 10 years.|url=https://www.businessinsider.com/nasa-asteroid-simulation-reveals-need-years-of-warning-2021-5 |date=12 May 2021 |work=Business Insider |accessdate=14 May 2021 }}{{cite news |last=Bartels |first=Meghan |title=How did you spend your week? NASA pretended to crash an asteroid into Earth. |url=https://www.space.com/planetary-defense-asteroid-impact-scenario-exercise-2021 |date=1 May 2021 |work=Space.com |accessdate=14 May 2021 }}{{cite news |last1=Chodas |first1=Paul |last2=Khudikyan |first2=Shakeh |last3=Chamberlin |first3=Alan |title=Planetary Defense Conference Exercise – 2021 Planetary Defense Conference (virtually) in Vienna, Austria, April 26–April 30, 2021. |url=https://cneos.jpl.nasa.gov/pd/cs/pdc21/ |date=30 April 2021 |work=NASA |accessdate=14 May 2021 }}
Overview
Image:Potentially Hazardous Asteroids 2013.png as of early 2013.]]
An object is considered a PHO if its minimum orbit intersection distance (MOID) with respect to Earth is less than {{convert|0.05|AU|km mi|abbr=on|lk=on}} – approximately 19.5 lunar distances – and its absolute magnitude is brighter than 22, approximately corresponding to a diameter above {{convert|140|m|ft|sp=us}}. This is big enough to cause regional devastation to human settlements unprecedented in human history in the case of a land impact, or a major tsunami in the case of an ocean impact. Such impact events occur on average around once per 10,000 years. NEOWISE data estimates that there are 4,700 ± 1,500 potentially hazardous asteroids with a diameter greater than 100 meters.
= Levels of hazard =
{{main|Torino scale|Palermo scale}}
The two main scales used to categorize the impact hazards of asteroids are the Palermo scale and the Torino scale.
= Potentially hazardous comet =
{{Unreferenced section|date=May 2022|find=Potentially hazardous comets}}
A potentially hazardous comet (PHC) is a short-period comet which currently has an Earth-MOID less than 0.05 AU. Known PHCs include: 109P/Swift-Tuttle, 55P/Tempel–Tuttle, 15P/Finlay, 289P/Blanpain, 255P/Levy, 206P/Barnard–Boattini, 21P/Giacobini–Zinner, and 73P/Schwassmann–Wachmann. Halley's Comet fit the criteria before AD 837, when it passed the earth at a distance of 0.033 AU. It now has an MOID of 0.075 AU.
= Numbers =
File:NEA by survey.pngs by various projects. The broader class of NEAs includes all PHAs as a subset.
| style="width: 100%; margin-bottom: 8px 0 6px; background-color:white;" |
| valign=top width=50% |
{{legend2|#0000FF|border=1px solid #0000B3|LINEAR}} {{legend2|#FFA500|border=1px solid #B37400|NEAT}} {{legend2|#FF0000|border=1px solid #800000|Spacewatch}} {{legend2|#FFFF00|border=1px solid #B3B300|LONEOS}} {{legend2|#008B00|border=1px solid #003D00|CSS}} | valign=top | {{legend2|#9400D3|border=1px solid #390052|Pan-STARRS}} {{legend2|#00CCCC|border=1px solid #333|NEOWISE}} {{legend2|#FFE4C4|border=1px solid #333|ATLAS}} {{legend2|#993300|border=1px solid #333|Others}} |
In 2012 NASA estimated 20 to 30 percent of these objects have been found. During an asteroid's close approaches to another planet it will be subject to gravitational perturbation, modifying its orbit, and potentially changing a previously non-threatening asteroid into a PHA or vice versa. This is a reflection of the dynamic character of the Solar System.
Several astronomical survey projects such as Lincoln Near-Earth Asteroid Research, Catalina Sky Survey and Pan-STARRS continue to search for more PHOs. Each one found is studied by various means, including optical, radar, and infrared to determine its characteristics, such as size, composition, rotation state, and to more accurately determine its orbit. Both professional and amateur astronomers participate in such observation and tracking.
= Size =
Asteroids larger than approximately 35 meters across can pose a threat to a town or city. However the diameter of most small asteroids is not well determined, as it is usually only estimated based on their brightness and distance, rather than directly measured, e.g. from radar observations. For this reason NASA and the Jet Propulsion Laboratory use the more practical measure of absolute magnitude (H). Any asteroid with an absolute magnitude of 22.0 or brighter is assumed to be of the required size.
Only a coarse estimation of size can be found from the object's magnitude because an assumption must be made for its albedo which is also not usually known for certain. The NASA near-Earth object program uses an assumed albedo of 0.14 for this purpose. In May 2016, the asteroid size estimates arising from the Wide-field Infrared Survey Explorer and NEOWISE missions have been questioned.{{cite news |last=Chang |first=Kenneth |title=How Big Are Those Killer Asteroids? A Critic Says NASA Doesn't Know. |url=https://www.nytimes.com/2016/05/24/science/asteroids-nathan-myhrvold-nasa.html |date=23 May 2016 |work=The New York Times |access-date=24 May 2016 }}{{cite arXiv|last=Myhrvold |first=Nathan |title=Asteroid thermal modeling in the presence of reflected sunlight with an application to WISE/NEOWISE observational data |date=23 May 2016 |eprint=1605.06490v2|class=astro-ph.EP }}{{cite web |last=Billings |first=Lee |title=For Asteroid-Hunting Astronomers, Nathan Myhrvold Says the Sky Is Falling |url=http://www.scientificamerican.com/article/for-asteroid-hunting-astronomers-nathan-myhrvold-says-the-sky-is-falling1/ |date=27 May 2016 |work=Scientific American |access-date=28 May 2016 }} Although the early original criticism had not undergone peer review,{{cite news |author=NASA Administrator |title=NASA Response to Recent Paper on NEOWISE Asteroid Size Results |url=https://www.nasa.gov/feature/nasa-response-to-recent-paper-on-neowise-asteroid-size-results |date=25 May 2016 |work=NASA |access-date=29 May 2016 }} a more recent peer-reviewed study was subsequently published.{{cite journal |last=Myhrvold |first=Nathan |author-link=Nathan Myhrvold |title=An empirical examination of WISE/NEOWISE asteroid analysis and results |journal=Icarus |volume=314 |pages=64–97 |doi=10.1016/j.icarus.2018.05.004 |bibcode=2018Icar..314...64M |year=2018 |doi-access=free }}{{cite news |last=Chang |first=Kenneth |title=Asteroids and Adversaries: Challenging What NASA Knows About Space Rocks – Two years ago, NASA dismissed and mocked an amateur's criticisms of its asteroids database. Now Nathan Myhrvold is back, and his papers have passed peer review. |url=https://www.nytimes.com/2018/06/14/science/asteroids-nasa-nathan-myhrvold.html |date=14 June 2018 |work=The New York Times |access-date=14 June 2018 }}
Largest PHAs
With a mean diameter of approximately 7 kilometers, Apollo asteroid {{mpl|(53319) 1999 JM|8}} is likely the largest known potentially hazardous object, despite its fainter absolute magnitude of 15.2, compared to other listed objects in the table below (note: calculated mean-diameters in table are inferred from the object's brightness and its (assumed) albedo. They are only an approximation.).
{{sort under}}
| class="wikitable sortable sort-under-center"
|+ Brightest Potentially Hazardous Asteroids ! width= 140 rowspan=2 | Designation !! colspan=3 | Discovery !! rowspan=2 | (H) | |||||||||
| width=45 | Year | Place | width=115 | Discoverer | Class | a {{small|(AU)}} | e | i {{small|(°)}} | q {{small|(AU)}} | Q {{small|(AU)}} | MOID {{small|(AU)}} |
|---|---|---|---|---|---|---|---|---|---|
| data-sort-value="4953" | {{mpl|(4953) 1990 MU}}
| 1990 | 413 | R. H. McNaught | 14.1 | 3 | APO | 1.621 | 0.658 | 24.4 | 0.555 | 2.687 | 0.02640 | — |{{MPC|4953}}{{·}}{{JPL|4953}}{{·}}{{LoMP|4953|catalog}} | |||||||||
| data-sort-value="3122" | 3122 Florence
| 1981 | 413 | S. J. Bus | 14.1 | 5 | AMO | 1.769 | 0.423 | 22.2 | 1.020 | 2.518 | 0.04430 | — |{{MPC|3122}}{{·}}{{JPL|3122}}{{·}}{{LoMP|3122|catalog}} | |||||||||
| data-sort-value="16960" | {{mpl|(16960) 1998 QS|52}}
| 1998 | 704 | LINEAR | 14.3 | 4 | APO | 2.203 | 0.858 | 17.5 | 0.313 | 4.093 | 0.01443 | — |{{MPC|16960}}{{·}}{{JPL|16960}}{{·}}{{LoMP|16960|catalog}} | |||||||||
| data-sort-value="4183" | 4183 Cuno
| 1959 | 074 | C. Hoffmeister | 14.4 | 4 | APO | 1.982 | 0.634 | 6.7 | 0.725 | 3.240 | 0.02825 | — |{{MPC|4183}}{{·}}{{JPL|4183}}{{·}}{{LoMP|4183|catalog}} | |||||||||
| data-sort-value="3200" | 3200 Phaethon
| 1983 | 500 | IRAS | 14.6 | 5.8 | APO | 1.271 | 0.890 | 22.3 | 0.140 | 2.402 | 0.01945 | — |{{MPC|3200}}{{·}}{{JPL|3200}}{{·}}{{LoMP|3200|catalog}} | |||||||||
| data-sort-value="242450" | {{mpl|(242450) 2004 QY|2}}
| 2004 | E12 | Siding Spring Survey | 14.7 | 3 | APO | 1.084 | 0.477 | 37.0 | 0.567 | 1.601 | 0.04686 | — |{{MPC|242450}}{{·}}{{JPL|242450}}{{·}}{{LoMP|242450|catalog}} | |||||||||
| data-sort-value="89830" | {{mpl|(89830) 2002 CE}}
| 2002 | 704 | LINEAR | 14.9 | 3.1 | AMO | 2.077 | 0.507 | 43.7 | 1.023 | 3.131 | 0.02767 | — |{{MPC|89830}}{{·}}{{JPL|89830}}{{·}}{{LoMP|89830|catalog}} | |||||||||
| data-sort-value="137427" | {{mpl|(137427) 1999 TF|211}}
| 1999 | 704 | LINEAR | 15.1 | 2.9 | APO | 2.448 | 0.610 | 39.2 | 0.955 | 3.942 | 0.01787 | — |{{MPC|137427}}{{·}}{{JPL|137427}}{{·}}{{LoMP|137427|catalog}} | |||||||||
| data-sort-value="111253" | {{mpl|(111253) 2001 XU|10}}
| 2001 | 704 | LINEAR | 15.2 | 3 | APO | 1.754 | 0.439 | 42.0 | 0.983 | 2.524 | 0.02934 | — |{{MPC|111253}}{{·}}{{JPL|111253}}{{·}}{{LoMP|111253|catalog}} | |||||||||
| data-sort-value="53319" | {{mpl|(53319) 1999 JM|8}}
| 1999 | 704 | LINEAR | 15.2 | 7 | APO | 2.726 | 0.641 | 13.8 | 0.978 | 4.474 | 0.02346 | Likely largest PHO |{{MPC|53319}}{{·}}{{JPL|53319}}{{·}}{{LoMP|53319|catalog}} | |||||||||
| data-sort-value="1981" | 1981 Midas
| 1973 | 675 | C. T. Kowal | 15.2 | 2 | APO | 1.776 | 0.650 | 39.8 | 0.621 | 2.931 | 0.00449 | — |{{MPC|1981}}{{·}}{{JPL|1981}}{{·}}{{LoMP|1981|catalog}} | |||||||||
| data-sort-value="2201" | 2201 Oljato
| 1947 | 690 | H. L. Giclas | 15.25 | 2.1 | APO | 2.175 | 0.713 | 2.5 | 0.624 | 3.726 | 0.00305 | — |{{MPC|2201}}{{·}}{{JPL|2201}}{{·}}{{LoMP|2201|catalog}} | |||||||||
| data-sort-value="90075" | {{mpl|(90075) 2002 VU|94}}
| 2002 | 644 | NEAT | 15.3 | 2.2 | APO | 2.134 | 0.576 | 8.9 | 0.904 | 3.363 | 0.03010 | — |{{MPC|90075}}{{·}}{{JPL|90075}}{{·}}{{LoMP|90075|catalog}} | |||||||||
| data-sort-value="4179" | 4179 Toutatis
| 1989 | 010 | C. Pollas | 15.30 | 2.5 | APO | 2.536 | 0.629 | 0.4 | 0.940 | 4.132 | 0.00615 | — |{{MPC|4179}}{{·}}{{JPL|4179}}{{·}}{{LoMP|4179|catalog}} | |||||||||
| data-sort-value="159857" | {{mpl|(159857) 2004 LJ|1}}
| 2004 | 704 | LINEAR | 15.4 | 3 | APO | 2.264 | 0.593 | 23.1 | 0.920 | 3.607 | 0.01682 | — |{{MPC|159857}}{{·}}{{JPL|159857}}{{·}}{{LoMP|159857|catalog}} | |||||||||
| data-sort-value="85713" | {{mpl|(85713) 1998 SS|49}}
| 1998 | 704 | LINEAR | 15.6 | 3.5 | APO | 1.924 | 0.639 | 10.8 | 0.694 | 3.154 | 0.00234 | — |{{MPC|85713}}{{·}}{{JPL|85713}}{{·}}{{LoMP|85713|catalog}} | |||||||||
| data-sort-value="4486" | 4486 Mithra
| 1987 | 071 | E. W. Elst | 15.6 | 2 | APO | 2.200 | 0.663 | 3.0 | 0.742 | 3.658 | 0.04626 | — |{{MPC|4486}}{{·}}{{JPL|4486}}{{·}}{{LoMP|4486|catalog}} | |||||||||
| data-sort-value="1620" | 1620 Geographos
| 1951 | 675 | A. G. Wilson | 15.60 | 2.5 | APO | 1.245 | 0.335 | 13.3 | 0.828 | 1.663 | 0.03007 | — |{{MPC|1620}}{{·}}{{JPL|1620}}{{·}}{{LoMP|1620|catalog}} | |||||||||
| data-sort-value="415029" | {{mpl|(415029) 2011 UL|21}}
| 2011 | 703 | CSS | 15.7 | 2.5 | APO | 2.122 | 0.653 | 34.9 | 0.736 | 3.509 | 0.01925 | — |{{MPC|415029}}{{·}}{{JPL|415029}}{{·}}{{LoMP|415029|catalog}} | |||||||||
| data-sort-value="242216" | {{mpl|(242216) 2003 RN|10}}
| 2003 | 699 | LONEOS | 15.7 | 2.5 | AMO | 2.231 | 0.541 | 39.6 | 1.024 | 3.438 | 0.00956 | — |{{MPC|242216}}{{·}}{{JPL|242216}}{{·}}{{LoMP|242216|catalog}} | |||||||||
| data-sort-value="12923" | 12923 Zephyr
| 1999 | 699 | LONEOS | 15.8 | 2 | APO | 1.962 | 0.492 | 5.3 | 0.996 | 2.927 | 0.02115 | — |{{MPC|12923}}{{·}}{{JPL|12923}}{{·}}{{LoMP|12923|catalog}} | |||||||||
| data-sort-value="12923" | {{mpl|(52768) 1998 OR|2}}
| 1998 | 566 | NEAT | 15.8 | 2 | APO | 2.380 | 0.573 | 5.9 | 1.017 | 3.743 | 0.01573 | — |{{MPC|52768}}{{·}}{{JPL|52768}}{{·}}{{LoMP|52768|catalog}} |
= Statistics =
Below is a list of the largest PHAs (based on absolute magnitude H) discovered in a given year. Historical data of the cumulative number of discovered PHA since 1999 are displayed in the bar charts—one for the total number and the other for objects larger than one kilometer. PHAs brighter than absolute magnitude 17.75 are likely larger than 1 km in size.
| class="wikitable floatleft sortable"
|+ Brightest PHA discoveries of each calendar year since 1989 ! data-sort-type="number" | Number ! width=85 | Name ! width=35 | Year ! width=35 | (H) ! Refs |
| align=right | 4179
| Toutatis | 1989 | 15.3 | {{MPC|4179}}{{·}}{{JPL|4179}}{{·}}{{LoMP|4179|catalog}} |
| align=right | 4953
| {{mpl-|4953|1990 MU}} | 1990 | 14.9 | {{MPC|4953}}{{·}}{{JPL|4953}}{{·}}{{LoMP|4953|catalog}} |
| align=right | 7341
| {{mpl|1991 VH}} | 1991 | 17.0 | {{MPC|35107}}{{·}}{{JPL|35107}}{{·}}{{LoMP|35107|catalog}} |
| align=right | 10115
| {{mpl|1992 SK}} | 1992 | 17.2 | {{MPC|10115}}{{·}}{{JPL|10115}}{{·}}{{LoMP|10115|catalog}} |
| align=right | 39572
| {{mpl-|39572|1993 DQ|1}} | 1993 | 16.6 | {{MPC|39572}}{{·}}{{JPL|39572}}{{·}}{{LoMP|39572|catalog}} |
| align=right | 7482
| {{mpl-|7482|1994 PC|1}} | 1994 | 16.7 | {{MPC|7482}}{{·}}{{JPL|7482}}{{·}}{{LoMP|7482|catalog}} |
| align=right | 243566
| {{mpl-|243566|1995 SA}} | 1995 | 17.4 | {{MPC|243566}}{{·}}{{JPL|243566}}{{·}}{{LoMP|243566|catalog}} |
| align=right | 8566
| {{mpl-|8566|1996 EN}} | 1996 | 16.3 | {{MPC|8566}}{{·}}{{JPL|8566}}{{·}}{{LoMP|8566|catalog}} |
| align=right | 35396
| {{mpl|1997 XF|11}} | 1997 | 17.0 | {{MPC|35396}}{{·}}{{JPL|35396}}{{·}}{{LoMP|35396|catalog}} |
| align=right | 16960
| {{mpl-|16960|1998 QS|52}} | 1998 | 14.4 | {{MPC|16960}}{{·}}{{JPL|16960}}{{·}}{{LoMP|16960|catalog}} |
| align=right | 137427
| {{mpl-|137427|1999 TF|211}} | 1999 | 15.3 | {{MPC|137427}}{{·}}{{JPL|137427}}{{·}}{{LoMP|137427|catalog}} |
| align=right | 138095
| {{mpl-|138095|2000 DK|79}} | 2000 | 16.0 | {{MPC|138095}}{{·}}{{JPL|138095}}{{·}}{{LoMP|138095|catalog}} |
| align=right | 111253
| {{mpl-|111253|2001 XU|10}} | 2001 | 15.3 | {{MPC|111253}}{{·}}{{JPL|111253}}{{·}}{{LoMP|111253|catalog}} |
| align=right | 89830
| {{mpl-|89830|2002 CE}} | 2002 | 15.0 | {{MPC|89830}}{{·}}{{JPL|89830}}{{·}}{{LoMP|89830|catalog}} |
| align=right | 242216
| {{mpl-|242216|2003 RN|10}} | 2003 | 15.7 | {{MPC|242216}}{{·}}{{JPL|242216}}{{·}}{{LoMP|242216|catalog}} |
| align=right | 242450
| {{mpl-|242450|2004 QY|2}} | 2004 | 14.6 | {{MPC|242450}}{{·}}{{JPL|242450}}{{·}}{{LoMP|242450|catalog}} |
| align=right | 308242
| {{mpl-|308242|2005 GO|21}} | 2005 | 16.3 | {{MPC|308242}}{{·}}{{JPL|308242}}{{·}}{{LoMP|308242|catalog}} |
| align=right | 374851
| {{mpl-|374851|2006 VV|2}} | 2006 | 16.7 | {{MPC|374851}}{{·}}{{JPL|374851}}{{·}}{{LoMP|374851|catalog}} |
| align=right | 214869
| {{mpl-|214869|2007 PA|8}} | 2007 | 16.5 | {{MPC|214869}}{{·}}{{JPL|214869}}{{·}}{{LoMP|214869|catalog}} |
| align=right | 294739
| {{mpl-|294739|2008 CM}} | 2008 | 17.1 | {{MPC|294739}}{{·}}{{JPL|294739}}{{·}}{{LoMP|294739|catalog}} |
| align=right | 523630
| {{mpl-|523630|2009 OG}} | 2009 | 16.2 | {{MPC|523630}}{{·}}{{JPL|523630}}{{·}}{{LoMP|523630|catalog}} |
| align=right | 458122
| {{mpl-|381906|2010 EW|45}} | 2010 | 17.6 | {{MPC|458122}}{{·}}{{JPL|458122}}{{·}}{{LoMP|458122|catalog}} |
| align=right | 415029
| {{mpl-|415029|2011 UL|21}} | 2011 | 15.9 | {{MPC|415029}}{{·}}{{JPL|415029}}{{·}}{{LoMP|415029|catalog}} |
| align=right | 746849
| {{mpl|2012 HJ|1}} | 2012 | 17.9 | {{MPC|2012+HJ1}}{{·}}{{JPL|2012+HJ1}}{{·}}{{LoMP|746849|catalog}} |
| align=right | 507716
| {{mpl-|507716|2013 UP|8}} | 2013 | 16.4 | {{MPC|507716}}{{·}}{{JPL|507716}}{{·}}{{LoMP|507716|catalog}} |
| align=right | 533671
| {{mpl|2014 LJ|21}} | 2014 | 16.1 | {{MPC|533671}}{{·}}{{JPL|533671}}{{·}}{{LoMP|533671|catalog}} |
| align=right | –
| {{mpl|2015 HY|116}} | 2015 | 17.6 | {{MPC|2015+HY116}}{{·}}{{JPL|2015+HY116}}{{·}} — |
| align=right | 620095
| {{mpl|2016 CB|194}} | 2016 | 17.6 | {{MPC|620095}}{{·}}{{JPL|620095}}{{·}}{{LoMP|620095|catalog}} |
| align=right | –
| {{mpl|2017 CH|1}} | 2017 | 17.9 | {{MPC|2017+CH1}}{{·}}{{JPL|2017+CH1}}{{·}} — |
| align=right | 756316
| {{mpl|2018 XV|5}} | 2018 | 17.7 | {{MPC|2018+XV5}}{{·}}{{JPL|2018+XV5}}{{·}}{{LoMP|756316|catalog}} |
| align=right | –
| {{mpl|2019 RU|3}} | 2019 | 18.1 | {{MPC|2019+RU3}}{{·}}{{JPL|2019+RU3}}{{·}} — |
| align=right | –
| {{mpl|2020 SL|1}} | 2020 | 17.7 | {{MPC|2020+SL1}}{{·}}{{JPL|2020+SL1}}{{·}} — |
| align=right | –
| {{mpl|2021 HK|12}} | 2021 | 17.7 | {{MPC|2021+HK12}}{{·}}{{JPL|2021+HK12}}{{·}} — |
| align=right | –
| {{mpl|2022 AP|7}} | 2022 | 17.3 | {{MPC|2022+AP7}}{{·}}{{JPL|2022+AP7}}{{·}} — |
| align=right | –
| {{mpl|2023 QF|5}} | 2023 | 18.3 | {{MPC|2023+QF5}}{{·}}{{JPL|2023+QF5}}{{·}} — |
| id=2024
| align=right | – | {{mpl|2024 YU|4}} | 2024 | 19.0 | {{MPC|2024+YU4}}{{·}}{{JPL|2024+YU4}}{{·}} — |
{{Image frame
|width = 500
|align=right
|pos=bottom
|content=
| width = 500
| height = 300
| group 1 =50 : 59 : 71 : 83 : 98 : 105 : 121 : 130 : 134 : 138 : 142 : 145 : 146 : 150 : 150 : 152 : 153 : 155 : 156 : 156 : 156 : 157 : 157
| colors = #FF3366
| group names =
| units suffix = _PHA-KM discovered
| x legends = prev. : 1999 : : 2001: : 2003 : : 2005: : 2007 : : 2009 : : 2011 : : 2013 : : 2015 : : 2017 : : 2019 :
}}
|caption =Cumulative number of discovered potentially hazardous asteroids larger than 1 kilometer by end of year (first of December). As of September 2020, there are 157 known PHAs larger than one kilometer.
|max-width=}}
{{Image frame
|width = 500
|align=right
|pos=bottom
|content=
| width = 500
| height = 300
| group 1=162 : 209 : 286 : 360 : 466 : 536 : 636 : 729 : 819 : 897 : 993 : 1078 : 1158 : 1265 : 1344 : 1436 : 1524 : 1629 : 1736 : 1857 : 1944 : 2036 : 2115
| colors = #003DF5
| group names =
| units suffix = _PHA discovered
| x legends = prev. : 1999 : : 2001: : 2003 : : 2005: : 2007 : : 2009 : : 2011 : : 2013 : : 2015 : : 2017 : : 2019 :
}}
|caption = Cumulative number of all discovered PHA by end of year (first of December). As of September 2020, there are 2115 PHAs.
|max-width=}}
{{clear}}
Gallery
File:2005YU55-20111107.jpg|Radar image of the 350-meter PHO {{mpl|(308635) 2005 YU|55}}
See also
{{div col}}
- Asteroid impact avoidance
- Earth-grazing fireball
- Global catastrophic risk
- List of asteroid close approaches to Earth
- {{annotated link|Scout (NASA program)}}; short term warnings
- {{annotated link|Sentry (monitoring system)}}
- {{annotated link|Spaceguard}}
{{div col end}}
Notes
{{notelist|refs=
{{efn|name=note-diameter-estimates|1=An object's calculated mean-diameter is only a rough estimate. It is inferred from the object's varying brightness—observed and measured at various times—and the assumed, yet often unknown reflectivity of its surface. NASA's [https://cneos.jpl.nasa.gov/tools/ast_size_est.html Asteroid Size Estimator] is a tool for a generic absolute magnitude-to-diameter conversion for an assumed geometric albedo.}}
}}
References
{{reflist|refs=
|title = List of the Potentially Hazardous Asteroids (PHAs)
|publisher = Minor Planet Center
|url = https://www.minorplanetcenter.net/iau/lists/t_phas.html
|access-date = 16 January 2018}}
|title = Report of the Task Force on potentially hazardous Near Earth Objects
|author = Task Force on potentially hazardous Near Earth Objects
|date = September 2000
|url = http://www.nss.org/resources/library/planetarydefense/2000-ReportOfTheTaskForceOnPotentiallyHazardousNearEarthObjects-UK.pdf
|access-date = 22 January 2018
|archive-url = https://web.archive.org/web/20161210142717/http://nss.org/resources/library/planetarydefense/2000-ReportOfTheTaskForceOnPotentiallyHazardousNearEarthObjects-UK.pdf
|archive-date = 10 December 2016
|url-status = dead
}}
|title = NEO Basics – Potentially Hazardous Asteroids (PHAs)
|publisher = CNEOS NASA/JPL
|url = https://cneos.jpl.nasa.gov/about/neo_groups.html
|access-date = 16 January 2020}}
|title = Unusual Minor Planets – Overview
|publisher = Minor Planet Center
|url = https://minorplanetcenter.net/iau/lists/Unusual.html
|access-date = 16 January 2020}}
|title = Discovery Statistics – Cumulative Totals
|publisher = CNEOS NASA/JPL
|date = 7 January 2020
|url = https://cneos.jpl.nasa.gov/stats/totals.html
|access-date = 16 January 2020}}
|title = NASA news – NASA Survey Counts Potentially Hazardous Asteroids
|date = 16 May 2012
|publisher = NASA/JPL
|url = https://www.jpl.nasa.gov/news/news.php?release=2012-138
|access-date = 22 January 2018}}
|title = Asteroid Hunter Gives an Update on the Threat of Near-Earth Objects
|date = 22 January 2013
|magazine = Scientific American
|author = Will Ferguson
|url = https://blogs.scientificamerican.com/observations/asteroid-hunter-gives-an-update-on-the-threat-of-near-earth-objects/
|access-date=2013-01-23}}
|title = JPL Small-Body Database Search Engine: PHAs and orbital class (APO)
|publisher = JPL Solar System Dynamics
|url = https://ssd.jpl.nasa.gov/sbdb_query.cgi?obj_group=pha;obj_kind=all;obj_numbered=all;ast_orbit_class=APO;OBJ_field=0;ORB_field=0;table_format=HTML;max_rows=100;format_option=comp;c_fields=AcBhBgBjBiBnBsCjCpAi;.cgifields=format_option;.cgifields=obj_kind;.cgifields=obj_group;.cgifields=obj_numbered;.cgifields=ast_orbit_class;.cgifields=table_format;.cgifields=com_orbit_class&query=1&c_sort=AcA
|access-date = 16 January 2020}}
|title = JPL Small-Body Database Search Engine: PHAs and orbital class (ATE)
|publisher = JPL Solar System Dynamics
|url = https://ssd.jpl.nasa.gov/sbdb_query.cgi?obj_group=pha;obj_kind=all;obj_numbered=all;ast_orbit_class=ATE;OBJ_field=0;ORB_field=0;table_format=HTML;max_rows=100;format_option=comp;c_fields=AcBhBgBjBiBnBsCjCpAi;.cgifields=format_option;.cgifields=obj_kind;.cgifields=obj_group;.cgifields=obj_numbered;.cgifields=ast_orbit_class;.cgifields=table_format;.cgifields=com_orbit_class&query=1&c_sort=AcA
|access-date = 16 January 2020}}
|title=Sentry Risk Table
|url=https://cneos.jpl.nasa.gov/sentry/
|access-date=2022-09-29}} (Click "Use Unconstrained Settings" and select "H<=22" for list of PHAs)
(17 Sentry "risk-listed" PHAs / [https://cneos.jpl.nasa.gov/stats/totals.html 2289 known PHAs]) ≈ 0.74%
}}
External links
- [https://cneos.jpl.nasa.gov/sentry/ Sentry: Earth Impact Monitoring (current)] (NASA NEO Program)
- [http://andrew-lowe.ca/ALL-PHAS.HTM#Earth Very Close Approaches (<0.01 AU) of PHAs to Earth 1900-2200]
- [http://www.brera.mi.astro.it/sormano/teca.html TECA Table of Asteroids Next Closest Approaches to the Earth], Sormano Astronomical Observatory
- [http://www.brera.mi.astro.it/sormano/mbpl.html MBPL – Minor Body Priority List (PHA Asteroids)], Sormano Astronomical Observatory
- [http://swfound.org/media/16114/iac-10.e3.1b.4.pdf Responding to the Threat of Potentially-Hazardous Near Earth Objects] (PDF)
- [https://www.theguardian.com/science/2015/dec/23/risk-of-comet-hitting-earth-as-bad-as-asteroids-or-worse-say-researchers Risk of comet hitting Earth is greater than previously thought, say researchers], The Guardian, 22 December 2015
- [https://www.minorplanetcenter.net/iau/lists/Sizes Conversion of Absolute Magnitude to Diameter], Minor Planet Center
=== Minor Planet Center ===
- [http://www.minorplanetcenter.net/iau/lists/t_phas.html List of the Potentially Hazardous Asteroids (PHAs)]
- {{YouTube|id=Ar_h-zAccsY|title=Asteroid Hazards, Part 2: The Challenge of Detection}} {{small|(min. 7:14)}}
- {{YouTube|id=8M_27st1ZCI|title=Asteroid Hazards, Part 3: Finding the Path}} {{small|(min. 5:38)}}
{{Natural disasters}}
{{Small Solar System bodies}}
{{Solar System}}
{{Modern impact events}}
{{Impact cratering on Earth}}
{{Planetary defense}}
{{Doomsday}}
{{Portal bar|Stars|Spaceflight|Outer space|Science}}