Possible impact of asteroid 2024 YR4 on the Moon in December 2032 Paul Wiegert 2025-06-13 | This simulation shows what could happen if asteroid 2024 YR4 hits the Moon in 2032, in particular how material lofted fast enough to escape our natural satellite's gravity could reach Earth. Asteroid 2024 YR4 is an asteroid with an estimated diameter of 60 meters that at one point was thought to pose an impact risk to the Earth. Ongoing telescopic observations have refined our knowledge of its path, and now we know it will miss our planet. But there is still (as of June 2025) a 4% chance that the asteroid will strike the Moon. In a paper submitted in June 2025 to American Astronomical Society journals, the possibility that material could be ejected from the Moon by an impact from asteroid 2024 YR4 is examined from the point of view of the risk it poses to Earth-orbiting satellites. Ejected material could reach us within a few days. There would be an unusual number of meteors (shooting stars) for a week or so, but there would be no risk to anything or anyone on the surface, as our atmosphere would protect us. There is however potential risk to satellites (which are above our atmosphere) and to any astronauts or equipment on the Moon's surface. More information at physics.uwo.ca/~pwiegert/2024YR4/index.html In the animation, the outermost red circle around the Earth is at Geosynchronous Earth Orbit (GEO), where many communication and weather satellites are placed.The innermost green circle (hard to make out but right in by Earth) is Low Earth Orbit (LEO) where most satellites orbit. The yellow circle in-between indicates Medium Earth Orbit, where Global Positioning System (GPS) satellites are.
alpha Centauri and our Sun for the last million years Paul Wiegert 2025-02-28 | Could asteroids and meteors be reaching us from alpha Centauri, a triple star system which is one of our nearest neighbours in the Galaxy? To study this, a recreation of their paths over the last million or so years was put together in this animation. Alpha Centauri is currently approaching our Solar System and will pass it at a distance of about 3.3 light years in about 28 000 years. A paper was published on the topic in 2025 (Gregg and Wiegert, A Case Study of Interstellar Material Delivery: alpha Centauri, Planetary Science Journal) also available at arxiv.org/abs/2502.03224 that showed that perhaps as many as a million asteroids from alpha Centauri are currently within the extreme boundaries of our Solar System (shown by the Oort cloud in the animation). There could also be roughly 10 meteors per year that arrive at Earth itself, though how often such particles actually make the journey depends on the details of how much material is actually escaping from alpha Centauri at the current time.
Hypothetical scenario: 10 centimeter per second velocity change to Apophis prior to 2029 Paul Wiegert 2024-09-03 | Asteroid Apophis could be deflected by a small asteroid impact, that is, by a collision with one of the same small asteroids which occasionally appear as meteors ("shooting stars" or "falling stars") in the Earth's atmosphere. Though such an event is extremely unlikely, this computer simulation shows how hypothetical impacts on asteroid Apophis could affect its close pass to Earth in 2029. In this animation, the effect of a 3 meter diameter asteroid impact, creating a 10 centimeter/second impulse on Apophis, is shown. Hundreds of hypothetical scenarios, where in each the impact occurs at a random time and from a random direction, are all shown in the animation. The 5% of cases which could result in Earth impact are identified with an orange reticle. Apophis nominal is identified in green. Though an asteroid impact that could deflect Apophis enough to be dangerous is a theoretical possibility, large enough impacts on Apophis are extremely rare, and it is computed that there is only a 1 in a billion chance of such an outcome. The complete analysis is presented in "On the sensitivity of Apophis's 2029 Earth approach to small asteroid impacts", published in the peer-reviewed Planetary Science Journal in 2024 at http://dx.doi.org/10.3847/PSJ/ad644d
Asteroid Apophis closest encounters with other known asteroids Paul Wiegert 2024-03-01 | Asteroid Apophis is most famous for its close passes to Earth, which are expected in 2029 and 2036. The asteroid will miss the Earth safely on these occasions. A research paper by Wiegert & Hyatt (2024) in the Planetary Science Journal examines the possibility of Apophis bumping into another asteroid before its next close pass in April 2029, which could change its predicted path. Fortunately no such asteroid collisions are anticipated, but the closest passes of Apophis to other known asteroids up to 2029 are illustrated here by computer animation.
Asteroid Zoozve (2002 VE68) Paul Wiegert 2024-02-08 | Asteroid Zoozve (2002 VE68) is the first known "quasi-moon" of our Solar System. Discovered in 2002 by Brian Skiff at the Lowell Observatory Near-Earth-Object Search (LONEOS); it was shown in 2004 by Mikkola, Brasser, Wiegert and Innanen to be the first "quasi-moon" of our Solar System. The asteroid was brought to fame through Radiolab's podcast episode "Zoozve" in 2024, where host Latif Nasser described its appearance on artist Alex Foster's map of the Solar System, and the strange chain of events that subsequently lead to its unusual name. This animation shows Zoozve's path within our Solar System. Zoozve orbits the Sun while at the same time it moves in a large kidney-shaped path around Venus, whose gravity holds it in this delicate and temporary (that is, lasting only thousands of years, so temporary in a cosmic sense) relationship.
The Solar System context of an unusual fireball Paul Wiegert 2022-12-12 | A comparison of the orbits of the unusual fireball reported in Vida et al 2022, Nature Astronomy and all other Type 1 fireballs. The rocky fireball reported in this paper was seen over Alberta Canada on 22 February 2021, and came to us from the very edge of our planetary system, while other fireballs of this type originate from the inner solar system. We expect the outer edge of our Solar System to contain primarily icy material, so the arrival of a rocky visitor from this icy realm is a bit of a puzzle.
Asteroid 2022 WJ1 impacts southern Ontario in Canada 19 November 2022 Paul Wiegert 2022-11-21 | Asteroid 2022 WJ1 was first spotted by the Catalina Sky Survey in Arizona, when the approaching one-meter diameter asteroid was only hours from striking Earth. Astronomers from around the globe scrambled to take more observations, pinpointing the impact location to the Great Lakes region. Once it struck the top of our atmosphere, the asteroid became a fireball, flashing across the skies of Southern Ontario at 3:26 am local time. Residents along the Lake Ontario shoreline from Grimsby to Niagara-on-the-Lake Ontario should check their yards and driveways for new black rocks, which could be meteorites. If you believe you have found a suspicious rock from this event, please contact the Royal Ontario Museum at naturalhistory@rom.on.ca
A quick tour through our Solar System circa 2022 Paul Wiegert 2022-05-25 | The orbits of planets are in white and dwarf planets in yellow in this quick voyage from the Sun to the edge of our planetary system.
Earths second Trojan asteroid 2020 XL5 Paul Wiegert 2021-11-19 | A 'Trojan' asteroid is one that shares the orbit of a planet as the both travel around the Sun. The second Trojan asteroid for the Earth was reported in Hui et al (2021), accepted for publication in the Astrophysical Journal Letters (arxiv.org/abs/2111.05058). This animation shows this newly-discovered asteroid along with the first known Earth Trojan asteroid 2010 TK7 (both in green), as well as the first known Earth co-orbital asteroid (an exotic variation on the Trojan class of orbit) 3753 Cruithne, shown in a frame which rotates along with the planet.
Hypothetical lunar co-orbital asteroids Paul Wiegert 2021-11-02 | It is possible for asteroids to share the Moon's orbit around the Earth, in the same way that Jupiter's Trojan asteroids share that planet's orbit around the Sun. This video shows the orbital motion of hypothetical lunar Trojans computed as part of a telescopic search for lunar Trojans completed by Gregg & Wiegert (2021) arxiv.org/abs/2110.14743
Asteroid Phaethon during its December 2017 approach to Earth Paul Wiegert 2021-04-09 | A simulated view of the viewing geometry of asteroid (3200) Phaethon as it passed Earth in December 2017. The asteroid turns green during the time it was being observed by the Ningbo bureau of Education and Xinjiang observatory Telescope (NEXT), a 60 cm reflector at Xingming Observatory in Mt. Nanshan, Xinjiang, China. For more details, see M. Tabeshian, P. Wiegert, Q. Ye, M.-T. Hui, X. Gao, H. Tan, (2019), Asteroid (3200) Phaethon: Colors, Phase Curve, Limits on Cometary Activity, and Fragmentation, Astronomical Journal, 158: 30-41, available at arxiv.org/abs/1905.10329
Exomoon candidates in eight exoplanet systems from the Kepler mission Paul Wiegert 2020-12-01 | Artist's conceptions of the eight exomoon candidate systems from Fox & Wiegert (2020) together with the Earth-Moon system. Exomoons are the moons of exoplanets, that is, of planets that orbit stars other than our Sun. Learn the science behind this in 20 seconds at youtu.be/Eolkwe2jiGw or for more check out http://www.astro.uwo.ca/~wiegert/Kepler-exomoonsAll systems are to the same scale and the camera is at the same distance from each to make comparison easy. Includes KOI-268, Kepler 517 (KOI-303), Kepler 809 (KOI-1302), Kepler 857 (KOI-1472), Kepler 1000 (KOI-1888), Kepler 409 (KOI-1925), Kepler 1326 (KOI-2728) and Kepler 1442 (KOI-3220). The original list of six exomoon candidates was updated to eight after additional analysis. An open-access version of the paper, now accepted for publication in the Monthly Notices of the Royal Astronomical Society, can be found at arxiv.org/pdf/2006.12997
Near-Earth asteroid ALA2xH Paul Wiegert 2020-11-23 | Asteroid ALA2xH was first spotted in images taken by Cole Gregg, a graduate student at Western University's Dept of Physics and Astronomy and the Institute for Earth and Space Exploration (IESX) in London Canada. The asteroid was detected with a remotely-operated telescope in central Spain (itelescope.net T16) on 18 Nov 2020. Estimated at 50 to 100 meters in size, the small asteroid passed roughly 30,000 km above the Earth before heading back out into space.
Comet Halleys meteor showers Paul Wiegert 2020-08-08 | Figure 11 of Egal et al. (2020) Modeling the past and future activity of the Halleyids meteor showers, submitted to Astronomy and Astrophysics. The distribution of nodal locations of meteoroids crossing the ecliptic plane as a function of their time of ejection from 1P/Halley. The regions where meteoroids have their ascending node (Orionids) and their descending node (eta-Aquariids) are shown in magnified form in the middle and right panel of the figure. The position of Earth along its orbit is represented by blue dots and dates (gray arrows indicating month and dots the day of each month) or solar longitudes (middle and right panel). Particles are color-coded as a function of the time of their ejection from Halley. Meteoroids ejected when the comet was trapped in the 1:6 resonance are highlighted with red circles. Trails ejected between 3000 BCE and 1404 BCE are presented in gray as these are associated with the time frame when 1P/Halley has a less certain ephemeris.
How exomoons affect exoplanet transit timing Paul Wiegert 2020-06-23 | Exomoons (that is, moons of planets orbiting stars other than our Sun) can cause the timing of exoplanet transits to vary in such a way as to reveal the presence of the moon, without the moon being detectable in the brightness measurements (that is, the 'light curve', shown on the right) that reveal the presence of the planet. The red upper case shows an exoplanet with an exomoon. Because the planet and moon both orbit their centre of mass (small white dot) the planet's transit starts and ends at a different time than it would if it had no moon, which is shown by the blue case. The right panel shows brightness measurements of the star as seen from telescopes on Earth, with their small inevitable uncertainties, These uncertainties can hide the presence of the dimming caused by the small moon, even though its presence can be inferred from the change in the planet's transit timing.To see what eight exoplanet systems with transit variations consistent with exomoons might look like, check out youtu.be/nh71c0F3d94 or http://www.astro.uwo.ca/~wiegert/Kepler-exomoons or find an open-access version of the paper describing this exomoon search technique, accepted for publication by the Monthly Notices of the Royal Astronomical Society, at http://arxiv.org/abs/2006.12997
Exomoon candidates - all Paul Wiegert 2020-06-23 | Artist's conceptions of the six exomoon candidate systems from Fox & Wiegert (2020) together with the Earth-Moon system. Learn the science behind this in 20 seconds at youtu.be/Eolkwe2jiGw All systems are to the same scale and the camera is at the same distance from each to make comparison easy. Includes KOI-268, Kepler 517 (KOI-303), Kepler 1000 (KOI-1888), Kepler 409 (KOI-1925), Kepler 1326 (KOI-2728) and Kepler 1442 (KOI-3220). Note added 26 Nov 2020: candidate list updated to eight candidates. To see them all, check out youtu.be/nh71c0F3d94 or find an open-access version of the paper, accepted for publication by the Monthly Notices of the Royal Astronomical Society, at http://arxiv.org/abs/2006.12997
Exomoon candidates 2 of 2 Paul Wiegert 2020-06-22 | Artist's conceptions of three of the six exomoon candidate systems from Fox & Wiegert (2020) together with the Earth-Moon system. Learn the science behind this in 20 seconds at youtu.be/Eolkwe2jiGw All systems are to the same scale and the camera is at the same distance from each to make comparison easy. Includes Kepler 409 (KOI-1925), Kepler 1326 (KOI-2728) and Kepler 1442 (KOI-3220). Note added 26 Nov 2020: candidate list updated to eight candidates. To see them all, check out youtu.be/nh71c0F3d94 or find an open-access version of the paper, accepted for publication by the Monthly Notices of the Royal Astronomical Society, at http://arxiv.org/abs/2006.12997
Exomoon candidates 1 of 2 Paul Wiegert 2020-06-22 | Artist's conceptions of three of the six exomoon candidate systems from Fox & Wiegert (2020) together with the Earth-Moon system. Learn the science behind this in 20 seconds at youtu.be/Eolkwe2jiGw All systems are to the same scale and the camera is at the same distance from each to make comparison easy. Includes KOI-268, Kepler 517 (KOI-303) and Kepler 1000 (KOI-1888). Note added 26 Nov 2020: candidate list updated to eight candidates. To see them all, check out youtu.be/nh71c0F3d94 or find an open-access version of the paper, accepted for publication by the Monthly Notices of the Royal Astronomical Society, at http://arxiv.org/abs/2006.12997
Dispersal of DART impact debris Paul Wiegert 2020-06-01 | Simulation of the debris from the DART (Double Asteroid Redirection Test) spacecraft impact. From Wiegert (2020), On the Delivery of DART-ejected Material from Asteroid (65803) Didymos to Earth, Planetary Science Journal, 1, 3.
DART impacting asteroid Didymos Paul Wiegert 2020-06-01 | Simulation of the debris from the DART (Double Asteroid Redirection Test) spacecraft impact. From Wiegert (2020), On the Delivery of DART-ejected Material from Asteroid (65803) Didymos to Earth, Planetary Science Journal, 1, 3.
Interstellar wanderers: arrival directions Paul Wiegert 2020-05-25 | The arrival directions of asteroid 1I/`Oumuamua, comet 2I/Borisov and the interstellar meteors reported in Froncisz, Brown and Weryk (2020) in the context of our local Galactic neighbourhood
Asteroid Oumuamua and Comet Borisov through our Solar System - backward in time Paul Wiegert 2020-05-22 | ...
Asteroid Oumuamua and Comet Borisov through our Solar System - forward in time Paul Wiegert 2020-05-22 | ...
Comet Borisov Final Approach to our Solar System Paul Wiegert 2020-05-22 | Gaia Data Release 2 stars are shown with colours appropriate to their effective temperatures. Stars passing within 5 parsecs of comet 2I/Borisov are called out with blue lines.
Oumuamua Final Approach to our Solar System Paul Wiegert 2020-05-22 | Gaia Data Release 2 stars are shown with colours appropriate to their effective temperatures. Stars passing within 5 parsecs of `Oumuamua are called out with blue lines.
Sungrazing and sunskirting comets Paul Wiegert 2020-05-19 | Simulation of the orbits of SOHO and STEREO comets
