Does the Earth have another moon?

Does the Earth have another moon?

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I was just wondering what are the chances that there is a small object (say less than 1 km but more than few meters) that orbits the Earth but has remained undetected by us? Are we actually scanning the space around the Earth continuously for orbiting bodies?

Not strictly satellites/moons, but certainly companions are 2010 TK7 with a diameter of ~300 m, an Earth trojan at the L4 point, and the ~5 km 3753 Cruithne in a peculiar orbit locked to the Earth's.

One kilometer, no way! That would've been known since long ago. Most asteroids of that size have already been found, all the way out to the asteroid belt beyond Mars. Earth has no second Moon. But there are always some tiny asteroids around, which are temporarily captured by Earth's gravity. Here's a funny illustration of such an orbit, it is not what we would like to call a moon. I think that only one of them have been found, the 5 meter diameter 2006RH120. Smaller objects would not be detectable today, but there are at any moment likely many meter and submeter sized asteroids visiting the Sun-Earth Lagrange points. A paper about it.

Space is not yet being scanned, but telescopes are now being built to do that. It will be a new kind of astronomy, looking for the unexpected, and who knows what will be found out there in the blackness. Still today amateur astronomers can discover asteroids with the telescope in their backyard. I'm afraid that space telescopes like Gaia will kill their hobby and that this classic astronomical mapping of the sky will finally be finished.

The chances of what you are suggesting are almost nil. Though we might be constantly scanning our surrounding atmosphere to detect fragments of, or actual meteorites, other than the debris and artificial satellites that we ourselves have put in orbit around the earth, there is no second moon currently in orbit around us to the best of our knowledge.

There is, however, a theory that proposes the presence of another moon in the past. As per this theory, there was a planet "Theia" immediately close to earth that underwent a close collision with Earth to form two moons, which ultimately coalesced to form the single moon we see today.

Read here:

Does The Earth Have "One" Or "Three" Moons?

Many planets have a moon that orbits around it. Jupiter has the most known moons at 79, while Mercury and Venus have no moon. By definition, a moon is an astronomical object that orbits another body in the solar system, a planet or a minor planet. In the case of Earth, there is only one known moon, which is simply called “The Moon.” However, there have been speculations for at least half a century that there could be two other moons orbiting the earth as well.

Does Earth Have A Second Moon?

That moment when it seems like everything we needed to know has be learned, is there something as seemingly predictable as the moon?
NASA provides the kind of significant discovery that forces the mind of researchers and all humans to reconsider everything.

image source

If greatness is to be given or crowned by the moon count of a planet's, I think Jupiter would take glory with ease because of its 69 satellites, but Other interesting things are happening around Earth too.
Yeah as we all know, earth has got a trusty Luna who keeps our waves waving and our nights lit, but as NASA recently learned and discovered, Earth has another lunar love.

According to NASSA, a small asteroid which has been discovered in an orbit within the sun that keeps it as a constant companion of Earth, which will remain that way for centuries to come.

image source

As it orbits the sun, the new asteroid, which was designated 2016 HO3, will appear to circle around Earth as well. Because of its distance, we cannot considered it a true satellite of our planet yet, but it is known as the best and most consistent example to date of a near-Earth companion, or "quasi-satellite."

"Since 2016 HO3 loops around our planet, but never ventures very far away as we both go around the sun, we refer to it as a quasi-satellite of Earth," said Paul Chodas, manager of NASA's Center for Near-Earth Object (NEO) Studies at the Jet Propulsion Laboratory in Pasadena, California. "One other asteroid -- 2003 YN107 -- which followed a similar orbital pattern for sometime over 10 years ago, but it has departed our vicinity over some time ago. This new asteroid is much more locked. Our calculations indicate 2016 HO3 has been a stable quasi-satellite of Earth for almost about a century, and it will continue to follow this pattern as Earth's companion for centuries to come."

Complete list of recent and upcoming close approaches can be gotten from here and other data on the orbits of known NEOs.

Also for asteroid news and updates, follow AsteroidWatch on Twitter:

How many moons does Earth have?

How many moons does Earth have? It’s a question with a very simple answer, and a more complex one.

The simple answer is that Earth has only one moon, which we call “the moon”. It is the largest and brightest object in the night sky, and the only solar system body besides Earth that humans have visited in our space exploration efforts.

The more complex answer is that the number of moons has varied over time.

When Earth first formed, around 4.5 billion years ago, it had no moons, but that soon changed. Researchers believe that the proto-Earth was struck by an object the size of Mars, nicknamed Theia, blasting much of its crust into orbit. This debris eventually formed into the moon we know today.


Although the moon is our only permanent natural satellite, astronomers have discovered many other near-Earth objects that could be considered honorary ‘mini’ moons.

These fall into a few groups. First there are temporary satellites objects that have been captured by Earth’s gravity, putting them into orbit before they eventually escape again. We know of only two – a small asteroid called 2006 RH120, which orbited Earth for nine months in 2006 and 2007, and 2020 CD3, another small asteroid spotted just before it flew away from Earth in March 2020, having spent almost three years in orbit.

Then there are objects that orbit around the sun in Earth’s vicinity. Two of these, 2010 TK7 and 2020 XL5 are known as Trojans, and occupy gravitationally stable points in space known as Lagrange points, which are created by the interaction between Earth and the sun’s gravity and follow our planet’s orbital path. The Lagrange points also seem to collect large amounts of dust particles, which some astronomers have dubbed Kordylewski clouds or “ghost moons”.

Some objects known as quasi-satellites don’t follow Earth’s orbit, but take 365 days to orbit the sun just like our planet, making them appear to be in orbit despite being outside Earth’s gravitational influence.

Other close objects approaching our planet before heading in the opposite direction around the sun until meeting Earth again on the other side. These trace out the shape of a horseshoe, so are known as horseshoe orbits.

Finally, Earth is also orbited by many artificial satellites that occasionally get mistaken for potential new moons. In 2015, astronomers excitedly announced the observation of one such object, only to later realise it was actually the Gaia space telescope.

8.2 Earth’s Crust

Let us now examine our planet’s outer layers in more detail. Earth ’s crust is a dynamic place. Volcanic eruptions, erosion, and large-scale movements of the continents rework the surface of our planet constantly. Geologically, ours is the most active planet. Many of the geological processes described in this section have taken place on other planets as well, but usually in their distant pasts. Some of the moons of the giant planets also have impressive activity levels. For example, Jupiter’s moon Io has a remarkable number of active volcanoes.

Composition of the Crust

Earth’s crust is largely made up of oceanic basalt and continental granite. These are both igneous rock , the term used for any rock that has cooled from a molten state. All volcanically produced rock is igneous (Figure 8.6).

Two other kinds of rock are familiar to us on Earth, although it turns out that neither is common on other planets. Sedimentary rocks are made of fragments of igneous rock or the shells of living organisms deposited by wind or water and cemented together without melting. On Earth, these rocks include the common sandstones, shales, and limestones. Metamorphic rocks are produced when high temperature or pressure alters igneous or sedimentary rock physically or chemically (the word metamorphic means “changed in form”). Metamorphic rocks are produced on Earth because geological activity carries surface rocks down to considerable depths and then brings them back up to the surface. Without such activity, these changed rocks would not exist at the surface.

There is a fourth very important category of rock that can tell us much about the early history of the planetary system: primitive rock , which has largely escaped chemical modification by heating. Primitive rock represents the original material out of which the planetary system was made. No primitive material is left on Earth because the entire planet was heated early in its history. To find primitive rock, we must look to smaller objects such as comets, asteroids, and small planetary moons. We can sometimes see primitive rock in samples that fall to Earth from these smaller objects.

A block of quartzite on Earth is composed of materials that have gone through all four of these states. Beginning as primitive material before Earth was born, it was heated in the early Earth to form igneous rock, transformed chemically and redeposited (perhaps many times) to form sedimentary rock, and finally changed several kilometers below Earth’s surface into the hard, white metamorphic stone we see today.

Plate Tectonics

Geology is the study of Earth’s crust and the processes that have shaped its surface throughout history. (Although geo- means “related to Earth,” astronomers and planetary scientists also talk about the geology of other planets.) Heat escaping from the interior provides energy for the formation of our planet’s mountains, valleys, volcanoes, and even the continents and ocean basins themselves. But not until the middle of the twentieth century did geologists succeed in understanding just how these landforms are created.

Plate tectonics is a theory that explains how slow motions within the mantle of Earth move large segments of the crust, resulting in a gradual “drifting” of the continents as well as the formation of mountains and other large-scale geological features. Plate tectonics is a concept as basic to geology as evolution by natural selection is to biology or gravity is to understanding the orbits of planets. Looking at it from a different perspective, plate tectonics is a mechanism for Earth to transport heat efficiently from the interior, where it has accumulated, out to space. It is a cooling system for the planet. All planets develop a heat transfer process as they evolve mechanisms may differ from that on Earth as a result of chemical makeup and other constraints.

Earth’s crust and upper mantle (to a depth of about 60 kilometers) are divided into about a dozen tectonic plates that fit together like the pieces of a jigsaw puzzle (Figure 8.7). In some places, such as the Atlantic Ocean, the plates are moving apart in others, such as off the western coast of South America, they are being forced together. The power to move the plates is provided by slow convection of the mantle, a process by which heat escapes from the interior through the upward flow of warmer material and the slow sinking of cooler material. (Convection, in which energy is transported from a warm region, such as the interior of Earth, to a cooler region, such as the upper mantle, is a process we encounter often in astronomy—in stars as well as planets. It is also important in boiling water for coffee while studying for astronomy exams.)

Link to Learning

The US Geological Survey provides a map of recent earthquakes and shows the boundaries of the tectonic plates and where earthquakes occur in relation to these boundaries. You can look close-up at the United States or zoom out for a global view.

As the plates slowly move, they bump into each other and cause dramatic changes in Earth’s crust over time. Four basic kinds of interactions between crustal plates are possible at their boundaries: (1) they can pull apart, (2) one plate can burrow under another, (3) they can slide alongside each other, or (4) they can jam together. Each of these activities is important in determining the geology of Earth.

Voyagers in Astronomy

Alfred Wegener: Catching the Drift of Plate Tectonics

When studying maps or globes of Earth, many students notice that the coast of North and South America, with only minor adjustments, could fit pretty well against the coast of Europe and Africa. It seems as if these great landmasses could once have been together and then were somehow torn apart. The same idea had occurred to others (including Francis Bacon as early as 1620), but not until the twentieth century could such a proposal be more than speculation. The scientist who made the case for continental drift in 1920 was a German meteorologist and astronomer named Alfred Wegener (Figure 8.8).

Born in Berlin in 1880, Wegener was, from an early age, fascinated by Greenland, the world’s largest island, which he dreamed of exploring. He studied at the universities in Heidelberg, Innsbruck, and Berlin, receiving a doctorate in astronomy by reexamining thirteenth-century astronomical tables. But, his interests turned more and more toward Earth, particularly its weather. He carried out experiments using kites and balloons, becoming so accomplished that he and his brother set a world record in 1906 by flying for 52 hours in a balloon.

Wegener first conceived of continental drift in 1910 while examining a world map in an atlas, but it took 2 years for him to assemble sufficient data to propose the idea in public. He published the results in book form in 1915. Wegener’s evidence went far beyond the congruence in the shapes of the continents. He proposed that the similarities between fossils found only in South America and Africa indicated that these two continents were joined at one time. He also showed that resemblances among living animal species on different continents could best be explained by assuming that the continents were once connected in a supercontinent he called Pangaea (from Greek elements meaning “all land”).

Wegener’s suggestion was met with a hostile reaction from most scientists. Although he had marshaled an impressive list of arguments for his hypothesis, he was missing a mechanism. No one could explain how solid continents could drift over thousands of miles. A few scientists were sufficiently impressed by Wegener’s work to continue searching for additional evidence, but many found the notion of moving continents too revolutionary to take seriously. Developing an understanding of the mechanism (plate tectonics) would take decades of further progress in geology, oceanography, and geophysics.

Wegener was disappointed in the reception of his suggestion, but he continued his research and, in 1924, he was appointed to a special meteorology and geophysics professorship created especially for him at the University of Graz (where he was, however, ostracized by most of the geology faculty). Four years later, on his fourth expedition to his beloved Greenland, he celebrated his fiftieth birthday with colleagues and then set off on foot toward a different camp on the island. He never made it he was found a few days later, dead of an apparent heart attack.

Critics of science often point to the resistance to the continental drift hypothesis as an example of the flawed way that scientists regard new ideas. (Many people who have advanced crackpot theories have claimed that they are being ridiculed unjustly, just as Wegener was.) But we think there is a more positive light in which to view the story of Wegener’s suggestion. Scientists in his day maintained a skeptical attitude because they needed more evidence and a clear mechanism that would fit what they understood about nature. Once the evidence and the mechanism were clear, Wegener’s hypothesis quickly became the centerpiece of our view of a dynamic Earth.

Link to Learning

See how the drift of the continents has changed the appearance of our planet’s crust.

Rift and Subduction Zones

Plates pull apart from each other along rift zones , such as the Mid-Atlantic ridge, driven by upwelling currents in the mantle (Figure 8.9). A few rift zones are found on land. The best known is the central African rift—an area where the African continent is slowly breaking apart. Most rift zones, however, are in the oceans. Molten rock rises from below to fill the space between the receding plates this rock is basaltic lava, the kind of igneous rock that forms most of the ocean basins.

From a knowledge of how the seafloor is spreading, we can calculate the average age of the oceanic crust. About 60,000 kilometers of active rifts have been identified, with average separation rates of about 5 centimeters per year. The new area added to Earth each year is about 2 square kilometers, enough to renew the entire oceanic crust in a little more than 100 million years. This is a very short interval in geological time—less than 3% of the age of Earth. The present ocean basins thus turn out to be among the youngest features on our planet.

As new crust is added to Earth, the old crust must go somewhere. When two plates come together, one plate is often forced beneath another in what is called a subduction zone (Figure 8.9). In general, the thick continental masses cannot be subducted, but the thinner oceanic plates can be rather readily thrust down into the upper mantle. Often a subduction zone is marked by an ocean trench a fine example of this type of feature is the deep Japan trench along the coast of Asia. The subducted plate is forced down into regions of high pressure and temperature, eventually melting several hundred kilometers below the surface. Its material is recycled into a downward-flowing convection current, ultimately balancing the flow of material that rises along rift zones. The amount of crust destroyed at subduction zones is approximately equal to the amount formed at rift zones.

All along the subduction zone, earthquakes and volcanoes mark the death throes of the plate. Some of the most destructive earthquakes in history have taken place along subduction zones, including the 1923 Yokohama earthquake and fire that killed 100,000 people, the 2004 Sumatra earthquake and tsunami that killed more than 200,000 people, and the 2011 Tohoku earthquake that resulted in the meltdown of three nuclear power reactors in Japan.

Fault Zones and Mountain Building

Along much of their length, the crustal plates slide parallel to each other. These plate boundaries are marked by cracks or faults . Along active fault zones, the motion of one plate with respect to the other is several centimeters per year, about the same as the spreading rates along rifts.

One of the most famous faults is the San Andreas Fault in California, which lies at the boundary between the Pacific plate and the North American plate (Figure 8.10). This fault runs from the Gulf of California to the Pacific Ocean northwest of San Francisco. The Pacific plate, to the west, is moving northward, carrying Los Angeles, San Diego, and parts of the southern California coast with it. In several million years, Los Angeles may be an island off the coast of San Francisco.

Unfortunately for us, the motion along fault zones does not take place smoothly. The creeping motion of the plates against each other builds up stresses in the crust that are released in sudden, violent slippages that generate earthquakes. Because the average motion of the plates is constant, the longer the interval between earthquakes, the greater the stress and the more energy released when the surface finally moves.

For example, the part of the San Andreas Fault near the central California town of Parkfield has slipped every 25 years or so during the past century, moving an average of about 1 meter each time. In contrast, the average interval between major earthquakes in the Los Angeles region is about 150 years, and the average motion is about 7 meters. The last time the San Andreas fault slipped in this area was in 1857 tension has been building ever since, and sometime soon it is bound to be released. Sensitive instruments placed within the Los Angeles basin show that the basin is distorting and contracting in size as these tremendous pressures build up beneath the surface.

Example 8.1

Fault Zones and Plate Motion


Check Your Learning


The difference in time from 1857 to 2047 is 190 y, or 1.9 centuries. Because only half the strain is released, this is equivalent to half the annual rate of motion. The total slippage comes to
0.5 × 5 m/century × 1.9 centuries = 4.75 m.

When two continental masses are moving on a collision course, they push against each other under great pressure. Earth buckles and folds, dragging some rock deep below the surface and raising other folds to heights of many kilometers. This is the way many, but not all, of the mountain ranges on Earth were formed. The Alps, for example, are a result of the African plate bumping into the Eurasian plate. As we will see, however, quite different processes produced the mountains on other planets.

Once a mountain range is formed by upthrusting of the crust, its rocks are subject to erosion by water and ice. The sharp peaks and serrated edges have little to do with the forces that make the mountains initially. Instead, they result from the processes that tear down mountains. Ice is an especially effective sculptor of rock (Figure 8.11). In a world without moving ice or running water (such as the Moon or Mercury), mountains remain smooth and dull.


Volcanoes mark locations where lava rises to the surface. One example is mid ocean ridges, which are long undersea mountain ranges formed by lava rising from Earth’s mantle at plate boundaries. A second major kind of volcanic activity is associated with subduction zones, and volcanoes sometimes also appear in regions where continental plates are colliding. In each case, the volcanic activity gives us a way to sample some of the material from deeper within our planet.

Other volcanic activity occurs above mantle “hot spots”—areas far from plate boundaries where heat is nevertheless rising from the interior of Earth. One of the best-known hot spot is under the island of Hawaii, where it currently supplies the heat to maintain three active volcanoes, two on land and one under the ocean. The Hawaii hot spot has been active for at least 100 million years. As Earth’s plates have moved during that time, the hot spot has generated a 3500-kilometer-long chain of volcanic islands. The tallest Hawaiian volcanoes are among the largest individual mountains on Earth, more than 100 kilometers in diameter and rising 9 kilometers above the ocean floor. One of the Hawaiian volcanic mountains, the now-dormant Maunakea, has become one of the world’s great sites for doing astronomy.

Link to Learning

The US Geological Service provides an interactive map of the famous “ring of fire,” which is the chain of volcanoes surrounding the Pacific Ocean, and shows the Hawaiian “hot spot” enclosed within.

Not all volcanic eruptions produce mountains. If lava flows rapidly from long cracks, it can spread out to form lava plains. The largest known terrestrial eruptions, such as those that produced the Snake River basalts in the northwestern United States or the Deccan plains in India, are of this type. Similar lava plains are found on the Moon and the other terrestrial planets.

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    Fossil is inspired by American creativity and ingenuity. Bringing new life into the watch and leathers industry by making quality, fashionable accessories that were both fun and accessible.

    Today, we continue to focus on what makes us, us: Our optimistic attitude, our dedication to authenticity and, of course, our creative spirit. The things we make, from traditional watches to smartwatches, bags to wallets, jewelry to gifts, complement every style, and fit every lifestyle&mdashfor all the moments that make you, you.

    6 Replies to &ldquoHow Many Moons Does Earth Have?&rdquo

    New research shows we now have identified 5 moons orbiting the Earth. Witch means ‘the moon’ should only be called lunar

    In 1986 D. Waldron in Australia discovered a 5 km diameter companion to Earth a co-orbital near Earth asteroid. He named it 3753 Cruithne, pronounced Crueenya, after a Celtic tribe also known as the Picts. It has a very strange orbit about the sun which is elliptical and sweeps in passed Venus almost to mercury and then out almost to mars. One orbit takes almost exactly a year. It is choreographed so that the orbit is stable and Cruithne will never strike the earth.
    It takes one year for Cruithne to orbit the sun, as does the Earth and the Moon.

    Just as the moons orbit is transformed from a sinusoidally wiggling ellipse about the sun into a nearly circular orbit of the earth when viewed in the earth frame of reference, so to does Cruithne’s orbit present an interesting pattern when viewed from a reference frame attached to the earth. (The transformation from the sun frame to the earth frame is well shown in a movie on Paul Wiegert’s site.) When viewed from a point above the north pole of the earth the asteroid Cruithne follows a type of complex horseshoe orbit.

    Another co-orbital asteroid in a horseshoe orbit, named 2002AA29, it is only 100 m in diameter. It comes near the earth every 95 years, most recently January 8, 2003. In another 600 years it will orbit the earth once a year, then after 50 years of orbits drift away again. It is a quasi satellite of earth at a distance of 0.2 AU. It is 100 m in radius. (It last orbited earth in 572 AD.) Viewed from the earth frame it sometimes orbits over the poles, toward and away from the sun. It thus can claim to be earth’s third moon, on a part time basis.

    Supermoon of 14 November is the closest Moon to Earth since 1948

    This image approximates the look of the full Moon on 14 November 2016 with data from NASA’s Lunar Reconnaissance Orbiter. When a full Moon makes its closest pass to Earth in its orbit it appears up to 14 percent bigger and 30 percent brighter, making it a supermoon. This month’s is especially ‘super’ for two reasons: it is the only supermoon this year to be completely full, and it is the closest Moon to Earth since 1948. The Moon won’t be this super again until 2034! Image credits: NASA Goddard / Clare Skelly / NASA’s Lunar Reconnaissance Orbiter / NASA Goddard’s Scientific Visualisation Studio. The Moon is a familiar sight in our sky, brightening dark nights and reminding us of space exploration, past and present. But the upcoming supermoon &mdash on Monday, 14 November &mdash will be especially “super” because it’s the closest full Moon to Earth since 1948. We won’t see another supermoon like this until 2034.

    The Moon is closest to the Earth at 11:23 UT (11:23am GMT) on 14 November 2016 when the distance between the centres of our two worlds will be 221,525 miles (356,510 kilometres). Full Moon occurs at 13:52 UT (1:52pm GMT), so observers in the British Isles looking for the perfect astrophoto opportunity should find an unobstructed east-northeast horizon to witness moonrise in bright twilight at 4:46pm GMT as seen from the heart of the UK (4:34pm in Norwich 4:43pm in London 4:42pm in Edinburgh). The Moon’s orbit around Earth is slightly elliptical so sometimes it is closer and sometimes it’s farther away. When the Moon is full as it makes its closest pass to Earth it is known as a supermoon. At perigree &mdash the point at which the moon is closest to Earth &mdash the Moon can be as much as 14 percent closer to Earth than at apogee, when the Moon is farthest from our planet. The full Moon appears that much larger in diameter and, because it is larger, shines 30 percent more moonlight onto the Earth. Image credit: NASA. The biggest and brightest Moon for observers in the United States will be on Monday morning just before dawn. On Monday, 14 November, the Moon is at perigee at 6:23am EST and “opposite” the Sun for the full Moon at 8:52am EST (after moonset for most of the US).

    If you’re not an early riser in the US, no worries. “I’ve been telling people to go out at night on either Sunday or Monday night to see the supermoon,” said Noah Petro, deputy project scientist for NASA’s Lunar Reconnaissance Orbiter (LRO) mission. “The difference in distance from one night to the next will be very subtle, so if it’s cloudy on Sunday, go out on Monday. Any time after sunset should be fine. Since the Moon is full, it’ll rise at nearly the same time as sunset, so I’d suggest that you head outside after sunset, or once it’s dark and the Moon is a bit higher in the sky. You don’t have to stay up all night to see it, unless you really want to!”

    For Australasian astronomers, the full Moon of 12:52am ACT on 15 November in the Australian capital (which is 2:52am NZDT in New Zealand) occurs 2½ hours after the Moon reaches this nearest perigee of the year. So, if you gaze at the Moon in the north-northwest when it is full shortly before 3am local time in New Zealand on 15 November, note that it will be 33.8 arcminutes in diameter.

    This is actually the second of three supermoons in a row, so if the clouds don’t cooperate for you this weekend, you will have another chance next month to see the last supermoon of 2016 on Wednesday 14 December.

    Earth has acquired a brand new moon that's about the size of a car

    Earth might have a tiny new moon. On 19 February, astronomers at the Catalina Sky Survey in Arizona spotted a dim object moving quickly across the sky. Over the next few days, researchers at six more observatories around the world watched the object, designated 2020 CD3, and calculated its orbit, confirming that it has been gravitationally bound to Earth for about three years.

    An announcement posted by the Minor Planet Center, which monitors small bodies in space, states that “no link to a known artificial object has been found”, implying that it is most likely an asteroid caught by Earth’s gravity as it passed by.

    BIG NEWS (thread 1/3). Earth has a new temporarily captured object/Possible mini-moon called 2020 CD3. On the night of Feb. 15, my Catalina Sky Survey teammate Teddy Pruyne and I found a 20th magnitude object. Here are the discovery images.


    This is just the second asteroid known to have been captured by our planet as a mini-moon – the first, 2006 RH120, hung around between September 2006 and June 2007 before escaping.

    Our new moon is probably between 1.9 and 3.5 metres across, or roughly the size of a car, making it no match for Earth’s primary moon. It circles our planet about once every 47 days on a wide, oval-shaped orbit that mostly swoops far outside the larger moon’s path.

    Want more science news? Check out our new podcast, New Scientist Weekly

    The orbit isn’t stable, so eventually 2020 CD3 will be flung away from Earth. “It is heading away from the Earth-moon system as we speak,” says Grigori Fedorets at Queen’s University Belfast in the UK, and it looks likely it will escape in April.

    However, there are several different simulations of its trajectory and they don’t all agree – we will need more observations to accurately predict the fate of our mini-moon and even to confirm that it is definitely a temporary moon and not a piece of artificial space debris. “Our international team is continuously working to constrain a better solution,” says Fedorets.

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    'Second Earth' found, 20 light years away

    Scientists have discovered a warm and rocky "second Earth" circling a star, a find they believe dramatically boosts the prospects that we are not alone.

    The planet is the most Earth-like ever spotted and is thought to have perfect conditions for water, an essential ingredient for life. Researchers detected the planet orbiting one of Earth's nearest stars, a cool red dwarf called Gliese 581, 20 light years away in the constellation of Libra.

    Measurements of the planet's celestial path suggest it is 1½ times the size of our home planet, and orbits close to its sun, with a year of just 13 days. The planet's orbit brings it 14 times closer to its star than Earth is to the sun. But Gliese 581 burns at only 3,000C, half the temperature of our own sun, making conditions on the planet comfortable for life, with average ground temperatures estimated at 0 to 40C. Researchers claim the planet is likely to have an atmosphere. The discovery follows a three-year search for habitable planets by the European Southern Observatory at La Silla in Chile.

    "We wouldn't be surprised if there is life on this planet," said Stephane Udry, an astronomer on the project at the Geneva Observatory in Switzerland.

    Two years ago, the same team discovered a giant Neptune-sized planet orbiting Gliese 581. A closer look revealed the latest planetary discovery, along with a third, larger planet that orbits the star every 84 days. The planets have been named after their star, with the most earthlike called Gliese 581c. The team spotted the planet by searching the "habitable zone".

    Scientists Have a Crazy New Hypothesis About The Origin of The Moon

    The usual explanation for the origin of the Moon describes it as the result of a collision between Earth and something else that spun material into space.

    But a new paper suggests that our satellite could have emerged from the ring of a vapourised planet - and this could answer some inconsistencies left by the collision theory.

    Called a synestia, and still only hypothetical, the vapourised planet is a relatively new concept.

    It's a doughnut-shaped, rapidly spinning cloud of rock and dust that can constitute part of the formation of rocky planets.

    According to a paper published last year, by Harvard graduate student Simon Lock and UC Davis planetary scientist Sarah Stewart, a synestia occurs when two planet-sized objects within the protoplanetary disc collide, resulting in the torus-shaped cloud of hot dust and liquid rotating around a molten core.

    This then collapses back down under its own gravity to become a planet.

    The structure of a planet, a planet with a disk and a synestia, all of the same mass (Simon Lock and Sarah Stewart)

    According to a new paper, also led by Lock and Stewart, it was inside Earth's synestia that the Moon formed, rather than a collision with a Mars-sized body called Theia 4.5 billion years ago that threw material into Earth's orbit.

    "The new work explains features of the Moon that are hard to resolve with current ideas," Stewart said.

    "The Moon is chemically almost the same as the Earth, but with some differences. This is the first model that can match the pattern of the Moon's composition."

    The Moon and Earth are made up of similar elements, which is consistent with the broken off chunk, but there are some differences that remain puzzling.

    For instance, relative to Earth, the Moon is far less abundant in volatile elements such as copper, potassium, sodium and zinc.

    "There hasn't been a good explanation for this," Lock said.

    "People have proposed various hypotheses for how the Moon could have wound up with fewer volatiles, but no one has been able to quantitatively match the Moon's composition."

    In Lock and Stewart's theory, Theia can still exist and still collide with Earth, but rather than breaking part off the forming planet to create a ring that eventually turned into the Moon, it pulverised it, creating a synestia.

    Around 10 percent of Earth would have been vapourised, and the rest would be liquid rock, the researchers said. Within this would be the seed of the Moon, a relatively small piece of liquid rock just off the centre of the synestia.

    As the synestia started to cool and fall towards its core, some of this liquid rock 'rain' would end up falling onto the Moon seed.

    "Over time, the whole structure shrinks, and the Moon emerges from the vapour," Lock said. "Eventually, the whole synestia condenses and what's left is a ball of spinning liquid rock that eventually forms the Earth as we know it today."

    This formation model would also solve the problem of the missing volatile elements, while fitting with the isotopic similarities, since both Earth and Moon formed from the same synestia.

    But since the Moon formed surrounded by pressures of tens of atmospheres of vapour, and at temperatures between 2,200 and 3,300 degrees Celsius (4,000 and 6,000 Fahrenheit), this would have evaporated the elements in question.

    The work, however, is still very much in progress. To start with, synestias have never been observed, and still have to be proven to exist. Testing of lunar material can also help figure out how likely the scenario is.

    "This is a basic model. We've done calculations of each of the processes that go into forming the Moon and shown that the model could work, but there are various aspects of our theory that will need more interrogation," Lock said.

    "For example, when the Moon is in this vapor, what does it do to that vapor? How does it perturb it? How does the vapor flow past the Moon? These are all things we need to go back and examine in more detail."