28

Ceres, Pallas, Juno and Vesta were all discovered between 1801 and 1807. After that, astronomers looked in vain for 38 years until the 5th, Astraea was spotted on December 8, 1845 by German amateur astronomer Karl L. Hencke by accident. He stumbled on Astraea while looking for Vesta one night. So, what took so long to discover Astrea? There is a paper1 which ...


25

The whole Earth "rippled" after the Chicxulub impact. By ripple, I specifically mean surface displacement. Current models indicate that it rippled enough that most of the dinosaurs and other species with brains certainly would have felt the ripple. How much did the Earth ripple? Well, that depends on the location. Meschede et al. [2011] in their ...


18

This can be answered in two ways. At the Earth's orbit we do not necessarily sample (meteoroid intercepting Earth and surviving atmospheric entry to fall as a meteorite) all the taxonomic types (spectral classifications as presented by Bus et al., 2002, DeMeo et al., 2009, DeMeo et al., 2015) of asteroids in the form of meteorites. For example, more than ...


18

The JPL Small Body Database lists Apophis close approaches dating back 100 years before discovery. Three fairly close ones were: 1907-04-13, 0.029 au 1949-04-14, 0.028 au 1990-04-14, 0.033 au While it's possible to run a dynamical integrator arbitrarily far backward or forward in time, any given pos(t), vel(t) state is only a point in a cloud of ...


17

Your best viewing opportunity will be 99942 Apophis which will pass Earth on April 13, 2029, where it will pass about 19,600 miles from Earth; look out for that. According to Wikipedia: On that date, it will become as bright as magnitude 3.1 (visible to the naked eye from rural as well as darker suburban areas, visible with binoculars from most locations) ...


15

Some estimates which I found worth sharing: For fun, I searched for Chixculub TNT equivalent and e.g. ScienceDaily claims The energy released by the impact that blew out the Chicxulub crater was equivalent to about 100 million megatons, many orders of magnitude greater than the nuclear explosion at Hiroshima, a 15-kiloton blast. This seems to match up ...


15

There are other iridium anomalies, particularly the Devonian-Carboniferous boundary (D-C boundary), about 350 Ma ago. The K-Pg boundary is only 66 Ma old. Just because there is an iridium anomaly doesn't mean it was due to a meteorite impact. One of the differences between the K-Pg boundary and the D-C boundary is the D-C boundary lacks shocked quartz, which ...


15

Whether an asteroid survives the fall through the atmosphere depends on its size and structural integrity. Our understanding of large impacts is limited (we haven't observed any, and this is a very good thing) Howver there is a calculator that can use current knowledge to forecast what would happen. For a one mile iron asteroid, hitting the atmosphere at ...


15

I believe the answer is yes, when the asteroid after the initial pass through the earth's atmosphere no longer has escape velocity relative to the earth, but enters an elliptical orbit around the earth. The perigee of the orbit will be within the atmosphere, so on the next pass the newly-captured earth satellite will lose more energy, lowering the perigee ...


14

To have an orbit perpendicular to the ecliptic plane, it would need to have an inclination of exactly 90 degrees. Orbits with inclination less than 90 degrees are prograde, and with greater are retrograde. Asteroids with inclinations even close to perpendicular to the ecliptic are rare since: Most of the matter rotating around the Sun coalesced in the ...


13

If you visit https://ssd.jpl.nasa.gov/horizons.cgi and enter Apophis as the target body (full name "99942 Apophis (2004 MN4)"), you can go to the "Time Span" link and see "Available time span for currently selected target body: 1599-Dec-12 to 2500-Dec-30" It's possible others have calculated its position beyond this time span, ...


12

As an example, look at Earth's only confirmed Trojan By Phoenix7777 - Own work Data source: HORIZONS System, JPL, NASA, CC BY-SA 4.0, source Now, to understand what is happening here. The yellow dot is the sun. The blue dot is the Earth. Although the Earth is orbiting the sun, the "camera" is turning so that it appears that the Earth is roughly ...


12

No, at its brightest in June 2021, 2021 LD6 [MPC, JPL] was apparent magnitude 20-21, well beyond the reach of most amateur telescopes. At absolute magnitude H=27.3, it's not very large, and at 10.5 times the lunar distance, it wasn't very close. Gideon van Buitenen keeps a list of near-Earth objects (NEOs) which will appear brighter than magnitude 14 ...


12

If by "more than once" you mean "more than once in a single visit", then that would seem impossible. After the first skip, the object is moving away from the earth. Either it has sufficient energy to depart or it doesn't. If it returns, then it doesn't have enough. Further interactions with the atmosphere won't give it any additional ...


8

No, it will not. The kinetic energy released upon impact is more than sufficient to vaporise even a metal asteroid. Barringer crater was caused by a metallic object, and there's nothing left of it. See the WikiPedia article for more information on this crater.


8

I will not commit to a "yes" or "no" answer, but instead refer to examples of artificial objects that do go at least down-up-down. From Space Exploration SE: Did the Apollo Command module really "skip" within, or off of the atmosphere as a part of its reentry program? How does skipping off the atmosphere work? Mathematically, ...


7

Names are common enough for solar system bodies, but generally stars don't have names, they have identifiers from various catalogues. In the case of Pulsars. they are named by their location in the sky. Just like Earth has longitude and latitude, every point in the sky has a "right ascension" and "declination". Due to the slow movement ...


7

When NASA says 5:50PM today, what location and/or timezone are they referring to? This particular website (eyes.nasa.gov) is using your system's local time to tell you the closest approach in your timezone. So when it says 5:50 PM today, it is when your clock reads 5:50 PM. Just be warned, if you have your system set to something else or possibly if you're ...


6

The rules from the the IAU for official designations are posted neatly here. More casual names, like the Black Widow Nebula, are not standardized, as far as I know. For astronomical objects outside of our own Solar System: the designation of astronomical objects beyond the Solar System should consist of at least two parts — a leading acronym and a sequence ...


6

But little bits of asteroids fall to Earth all the time as meteorites. Why can't we just study those? Scientists do study those. Clair Cameron Patterson, for example, determined the age of the Earth between the late 1940s to mid 1950s using meteorites. However, he had to spend years addressing contamination issues before he developed his estimate of the age ...


5

Trojan asteroids are in roughly circular orbits around the Sun at roughly the same distance as Jupiter, that are in 1:1 resonance with Jupiter and stay very roughly 60 degrees away from it. Scott Manley's video below shows two classes of asteroids in resonance with Jupiter. The first one shown is confusing because it is in a 3:2 resonance and in the rotating ...


5

It's currently very hard to impossible to observe asteroids around other stars. Asteroids are bodies with a size of at least several metres to a few hundred kilometres in diameter. There's three main ways to detect bodies: by their characteristic thermal emission by obstructing the light of their central star by reflecting light of their central start to us ...


5

An asteroid resting on Earth would be a mountain. Or, for smaller asteroids, a pile of gravel. Mountains are limited in altitude by the strength of stone to resist compression: a too tall mountain would sink down as the base crumbled and spread out. The limit on Earth is about 10 km. Besides the strength issue mountains are also floating ("isostasy"...


4

Meteorites have distinct compositions and so meteorites with similar compositions can be grouped into families. There are, for example the iron meteorites, meteorites with lots of carbon and so on. One family are called HED meteorites. They don't contain chondrules and show evidence of igneous processing (the rocks have been melted). The are differentiated....


4

I think I found the answer after some search. What I have been after is the JPL Small-Body Database Browser. You can simply enter the object name to the search field and it returns a page where you will find the orbital uncertainities along with other useful data. For example, type in 'eros' and you will see the results. Of course, this can be automated in ...


4

I think it is the "boulder" discovered by Nolan et al. (2013). They used radar images from two ground-based observatories, from two different passes, to perform shape modeling: The radar observations with Arecibo and the Goldstone planetary radar systems were carried out shortly after discovery, from 21 to 25 September, 1999, and again from 16 ...


4

HST Proposal 15144, entitled "Deep Search for Satellites Around the Lucy Mission Targets", has a data page with 24 Hubble images of Polymele (you need to go to page 2 of 2 of the table). An example below: There is also a publication (Nole et al. 2020) associated with the proposal, but it focuses on Eurybates.


3

To have an asteroid belt with the mass of a planet, asteroids would have to be much more massive or be much more closer apart from each other. Either of these will likely cause the asteroid belt to become a new planet. Rocks in Saturn's rings are also very close apart, but they are not forming a new moon because of the Roche limit, and if some chunks of ...


3

A science paper from 2019 by K. Kitazato et al. shows a shape model of the surface in Fig. 2, so we now indeed know the exact size and the exact mass, even the surface temperature distribution: The quoted paper refers to S. Watanabe et al., Science, 2019 which has all the details Ryugu has an oblate body, with an equatorial radius of 502 ± 2 m and polar-...


3

If an asteroid on an inner orbit catches up with a planet on an outer orbit, and passes close enough to the planet to be strongly influenced by the planet's gravity, it can whip around the planet ahead of the planet and then move in and orbit backwards (retrograde) farther from the sun than the planet. So the asteroid might be captured by the planet if its ...


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