Why Pluto is No Longer a Planet

Why is Pluto Not a Planet?
Why is Pluto Not a Planet?

This article was originally written in 2008, but we created a cool video to go along with it yesterday

Let’s find out why Pluto is no longer considered a planet.

Pluto was first discovered in 1930 by Clyde W. Tombaugh at the Lowell Observatory in Flagstaff Arizona. Astronomers had long predicted that there would be a ninth planet in the Solar System, which they called Planet X. Only 22 at the time, Tombaugh was given the laborious task of comparing photographic plates. These were two images of a region of the sky, taken two weeks apart. Any moving object, like an asteroid, comet or planet, would appear to jump from one photograph to the next.

After a year of observations, Tombaugh finally discovered an object in the right orbit, and declared that he had discovered Planet X. Because they had discovered it, the Lowell team were allowed to name it. They settled on Pluto, a name suggested by an 11-year old school girl in Oxford, England (no, it wasn’t named after the Disney character, but the Roman god of the underworld).

The Solar System now had 9 planets.

Astronomers weren’t sure about Pluto’s mass until the discovery of its largest Moon, Charon, in 1978. And by knowing its mass (0.0021 Earths), they could more accurately gauge its size. The most accurate measurement currently gives the size of Pluto at 2,400 km (1,500 miles) across. Although this is small, Mercury is only 4,880 km (3,032 miles) across. Pluto is tiny, but it was considered larger than anything else past the orbit of Neptune.

Over the last few decades, powerful new ground and space-based observatories have completely changed previous understanding of the outer Solar System. Instead of being the only planet in its region, like the rest of the Solar System, Pluto and its moons are now known to be just a large example of a collection of objects called the Kuiper Belt. This region extends from the orbit of Neptune out to 55 astronomical units (55 times the distance of the Earth to the Sun).

Astronomers estimate that there are at least 70,000 icy objects, with the same composition as Pluto, that measure 100 km across or more in the Kuiper Belt. And according to the new rules, Pluto is not a planet. It’s just another Kuiper Belt object.

Here’s the problem. Astronomers had been turning up larger and larger objects in the Kuiper Belt. 2005 FY9, discovered by Caltech astronomer Mike Brown and his team is only a little smaller than Pluto. And there are several other Kuiper Belt objects in that same classification.

Astronomers realized that it was only a matter of time before an object larger than Pluto was discovered in the Kuiper Belt.

And in 2005, Mike Brown and his team dropped the bombshell. They had discovered an object, further out than the orbit of Pluto that was probably the same size, or even larger. Officially named 2003 UB313, the object was later designated as Eris. Since its discovery, astronomers have determined that Eris’ size is approximately 2,600 km (1,600 miles) across. It also has approximately 25% more mass than Pluto.

With Eris being larger, made of the same ice/rock mixture, and more massive than Pluto, the concept that we have nine planets in the Solar System began to fall apart. What is Eris, planet or Kuiper Belt Object; what is Pluto, for that matter? Astronomers decided they would make a final decision about the definition of a planet at the XXVIth General Assembly of the International Astronomical Union, which was held from August 14 to August 25, 2006 in Prague, Czech Republic.

Astronomers from the association were given the opportunity to vote on the definition of planets. One version of the definition would have actually boosted the number of planets to 12; Pluto was still a planet, and so were Eris and even Ceres, which had been thought of as the largest asteroid. A different proposal kept the total at 9, defining the planets as just the familiar ones we know without any scientific rationale, and a third would drop the number of planets down to 8, and Pluto would be out of the planet club. But, then… what is Pluto?

In the end, astronomers voted for the controversial decision of demoting Pluto (and Eris) down to the newly created classification of “dwarf planet”.

Is Pluto a planet? Does it qualify? For an object to be a planet, it needs to meet these three requirements defined by the IAU:

  • It needs to be in orbit around the Sun – Yes, so maybe Pluto is a planet.
  • It needs to have enough gravity to pull itself into a spherical shape – Pluto…check
  • It needs to have “cleared the neighborhood” of its orbit – Uh oh. Here’s the rule breaker. According to this, Pluto is not a planet.

What does “cleared its neighborhood” mean? As planets form, they become the dominant gravitational body in their orbit in the Solar System. As they interact with other, smaller objects, they either consume them, or sling them away with their gravity. Pluto is only 0.07 times the mass of the other objects in its orbit. The Earth, in comparison, has 1.7 million times the mass of the other objects in its orbit.

Any object that doesn’t meet this 3rd criteria is considered a dwarf planet. And so, Pluto is a dwarf planet. There are still many objects with similar size and mass to Pluto jostling around in its orbit. And until Pluto crashes into many of them and gains mass, it will remain a dwarf planet. Eris suffers from the same problem.

It’s not impossible to imagine a future, though, where astronomers discover a large enough object in the distant Solar System that could qualify for planethood status. Then our Solar System would have 9 planets again.

Even though Pluto is a dwarf planet, and no longer officially a planet, it’ll still be a fascinating target for study. And that’s why NASA has sent their New Horizons spacecraft off to visit it. New Horizons will reach Pluto in July 2015, and capture the first close-up images of the (dwarf) planet’s surface.

Space enthusiasts will marvel at the beauty and remoteness of Pluto, and the painful deplaneting memories will fade. We’ll just be able to appreciate it as Pluto, and not worry how to categorize it. At least now you know why Pluto was demoted.

If you’d like more information about Pluto, we did two podcasts on this topic at Astronomy Cast. The first discusses the IAU’s decision, and the second is about Pluto and the Icy Outer Solar System. Check them out.

Here is much more info about Pluto, including pictures of Pluto.

References:
NASA Solar System Exploration Guide
Caltech

More “Hollowed Ground” on Mercury

MESSENGER captures image of curious "hollows" around a crater peak

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The latest featured image from NASA’s MESSENGER spacecraft, soon to complete its first year in orbit around Mercury, shows the central peak of the 78-mile (138-km) – wide crater Eminescu surrounded by more of those brightly-colored surface features dubbed “hollows”. Actually tinted a light blue color, hollows may be signs of an erosion process unique to Mercury because of its composition and close proximity to the Sun.

First noted in September of last year, hollows have now been identified in many areas across Mercury. They showed up in previous images as only bright spots, but once MESSENGER established orbit in March of 2011 and began high-resolution imaging of Mercury’s surface it became clear that these features were something totally new.

The lack of craters within hollows seems to indicate that they are relatively young features. In fact, they may be part of a process that continues even now.

“Analysis of the images and estimates of the rate at which the hollows may be growing led to the conclusion that they could be actively forming today,” said David Blewett of the Johns Hopkins University Applied Physics Laboratory (APL).

One hypothesis is that the hollows are formed by the sublimation of subsurface material exposed during the creation of craters, around which they are most commonly seen. Being so close to the Sun (29 million miles/46 million km at closest) and lacking a protective atmosphere like Earth’s, Mercury is constantly being scoured by the powerful solar wind. This relentless stream of charged particles may literally be “sandblasting” exposed volatile materials off the planet’s surface!

The image above shows an area approximately 41 miles (66 km) across. It has been rotated to enhance perspective; see the original image and caption here.

Image: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Storms And Lakes On Titan Revealed By Computer Modeling

An artist's imagination of hydrocarbon pools, icy and rocky terrain on the surface of Saturn's largest moon Titan. Image credit: Steven Hobbs (Brisbane, Queensland, Australia).

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Thanks to the Cassini mission and the Huygens probe, we’ve glimpsed a wet world when science took a look at Saturn’s moon, Titan. Its atmosphere is rich in methane and its average temperature is about -300 degrees Fahrenheit (about 90 kelvins). Although the chemical composition is different than ours, Titan still has similar features such as clouds, fog, rain and even lakes. However, the origin of these features haven’t really been well explained until now.

Researchers at the California Institute of Technology (Caltech) have been hard at work creating a computer program based on observations made by Cassini imaging and radar that could help explain Titan’s weather patterns and liquid surface deposits. One major oddity was discovered in 2009 when Oded Aharonson, Caltech professor of planetary science, and his team confirmed Titan’s lakes appeared to be gathered around its poles – more predominately in the northern hemisphere than compared to the south – yet that’s not the only curiosity. The areas around the equator were suspected to be dry, but the Huygens probe revealed areas of run-off and four years later researchers observed a storm system delivering moisture. Need more? Then check out the clouds observed by ground-based telescopes… They gather around southern middle and high latitudes during Titan’s southern hemisphere summer season.

“We can watch for years and see almost nothing happen. This is bad news for people trying to understand Titan’s meteorological cycle, as not only do things happen infrequently, but we tend to miss them when they DO happen, because nobody wants to waste time on big telescopes—which you need to study where the clouds are and what is happening to them—looking at things that don’t happen,” explains Mike Brown of the California Institute of Technology (Caltech).

Sure. The researchers have worked hard at creating models that could explain these exotic weather features, but such explanations involve way out theories, such as cryogenic volcanoes that blast out methane vapor to cause clouds. However, the latest computer renderings are much more basic – the principles of atmospheric circulation. “We have a unified explanation for many of the observed features,” says Tapio Schneider, the Frank J. Gilloon Professor of Environmental Science and Engineering. “It doesn’t require cryovolcanoes or anything esoteric.” Schneider, along with Caltech graduate student Sonja Graves, former Caltech graduate student Emily Schaller (PhD ’08), and Mike Brown, the Richard and Barbara Rosenberg Professor and professor of planetary astronomy, have published their findings in the January 5 issue of the journal Nature.

Why is this data set different than its predecessors? According the Schneider, these new simulations were able to reproduce cloud patterns which match factual observations – right down to the distribution of lakes. “Methane tends to collect in lakes around the poles because the sunlight there is weaker on average,” he explains. “Energy from the sun normally evaporates liquid methane on the surface, but since there’s generally less sunlight at the poles, it’s easier for liquid methane there to accumulate into lakes.” Because Titan has an elongated orbit, it’s a bit further away during the northern hemisphere summer allowing for a longer rainy season and thus a stronger accumulation of lakes.

So what about storms? Near the equator, Titan isn’t very exciting – or is it? Originally it was theorized the area was almost desert-like. That’s why when the Huygens probe discovered evidence of run-off, it became apparent that existing models could be wrong. Imagine the surprise when Schaller, Brown, Schneider, and then-postdoctoral scholar Henry Roe discovered storms in this supposedly arid region in 2009! No one could figure it out and the programs did little more than predict a drizzle. With the new model, heavy rains became a possibility. “It rains very rarely at low latitudes,” Schneider says. “But when it rains, it pours.”

So what else makes the new Titan weather computer model even more unique? This time it runs for 135 Titan years and links the methane lakes – and how methane is distributed – to its atmosphere. According to the research, this matches current Titan weather observations and will help to predict what could be seen in coming years. Making testable predictions is “a rare and beautiful opportunity in the planetary sciences,” Schneider says. “In a few years, we’ll know how right or wrong they are.”

“This is just the beginning,” he adds. “We now have a tool to do new science with, and there’s a lot we can do and will do.”

Original Story Source: California Institute of Technology News Release. For Further Reading: Caltech Scientists Discover Storms in the Tropics of Titan.

‘Impossible’ Crystals May Have Come From Space

Credit: Paul Steinhardt, Princeton University

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A unique type of crystal appears to have its origins in meteorites, according to a new study. Quasicrystals are an unusual type of crystalline structure that were initially thought to have only occurred in artificial conditions in labs, and impossible in nature, until they were found by geologists in the Koryak mountains in Russia in 2009. Their origin was unknown, but now new evidence indicates that they most likely came from space in meteorites, dating back to the early stages of the formation of the solar system.

Regular crystals, such as diamonds, snowflakes and salt, are symmetrical, ordered and repeating geometrical arrangements of atoms that extend in all three spatial dimensions (at both microscopic and macroscopic scales); they are commonly found in different types of rock. Quasicrystals are different however, with variations from the standard structure and composition.

When the newly found quasicrystals were studied, they were found to be composed primarily of copper and aluminum, similar to carbonaceous meteorites. The clincher came when the isotope measurements (ratios of oxygen atoms) indicated an extraterrestrial origin.

From the paper:

“Our evidence indicates that quasicrystals can form naturally under astrophysical conditions and remain stable over cosmic timescales.”

“The rock sample was first identified for study as a result of a decade-long systematic search for a natural quasicrystal (4). Quasicrystals are solids whose atomic arrangement exhibits quasi-periodic rather than periodic translational order and rotational symmetries that are impossible for ordinary crystals (5) such as fivefold symmetry in two-dimensions and icosahedral symmetry in three-dimensions. Until recently, the only known examples were synthetic materials produced by melting precise ratios of selected elemental components and quenching under controlled conditions (6–8). The search consisted of applying a set of metrics for recognizing quasicrystals to a database of powder diffraction data (4) and examining minerals outside the database with elemental compositions related to those of known synthetic quasicrystals.”

“What is clear, however, is that this meteoritic fragment is not ordinary. Resolving the remarkable puzzles posed by this sample will not only further clarify the origin of the quasicrystal phase but also shed light on previously unobserved early solar system processes. Fitting all these clues together in a consistent theory of formation and evolution of the meteorite is the subject of an ongoing investigation.”

The report has been published in the January 2 issue of Proceedings of the National Academy of Science. The article (PDF) is here. More detailed information about quasicrystals is also available here and here.

Space Station Crew Anticipating SpaceX Dragon’s Arrival

As part of the COTS 3 objectives Dragon approaches the ISS, so astronauts can reach it with the robotic arm. Illustration: NASA / SpaceX.

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In a media chat on Wednesday three crew members from the International Space Station said they are anticipating the historic arrival of SpaceX’s Dragon cargo ship to the ISS next month. “For all of us, we’re very excited about it,” said ISS Commander Dan Burbank. “Number one, for the sake of the Space Station, that is critical capability — to resupply the station and be able to return critical hardware, or payloads… And down the road it also affords capability to actually deliver crew to the station. I think that is very exciting.”

Burbank called the first arrival of a commercial vehicle “the start of new era.”

SpaceX released this image on January 4, 2012 showing the Dragon spacecraft in final processing, getting ready to head to the ISS. Credit: SpaceX

February 7, 2012 is the target date for the launch of the Dragon capsule. It will arrive at the ISS one to three days later and once there, Dragon will begin the demonstrations related to the Commercial Orbital Transportation Services Phase 2 agreements (COTS 2) to show proper performance and control in the vicinity of the ISS, while remaining outside the Station’s safe zone. Then, if all goes well, Dragon will receive approval to begin the COTS 3 activities, where it will gradually approach within a few meters of the ISS, allowing astronauts to reach out and grapple Dragon with the Station’s robotic arm and then maneuver it carefully into one of the docking ports.

Burbank said Dragon’s non-autonomous docking will put the astronauts at the center of activities for the vehicle’s arrival. “Anytime we have a visiting vehicle, those are exciting, dynamic events that from the operational standpoint,” he said.

But vehicles that come to the Station that need to be captured with the robotic arm offer an exceptional challenge for the crew. “From the standpoint of a pilot it is a fun, interesting, very dynamic activity and we are very much looking forward to it,” Burbank said. “It is the start of a new era, having commercial vehicles that come to Station.”

The Dragon will stay docked to the ISS for about a week while astronauts unload cargo and then re-load it with Earth-bound cargo. It will undock and return to Earth with a splashdown in the Pacific Ocean near the California coast.

NASA announced in December that the COTS 2 and 3 activities could be combined in one flight.

“This will be the first of many ‘wagon train’ wagons to bring us supplies,” said Flight Engineer Don Pettit. “One of the neat things about the SpaceX vehicle is that it will allow us to take significant payloads down, which is a real important thing since we no longer fly shuttles, we can’t take anything sizable back down from Space Station without it burning up. SpaceX will be our way to get…things back to the ground.”

In talking with the media, Burbank also spoke about his opportunity to capture stunning images of Comet Lovejoy from space,(see his images here) and encouraged the next generation of astronauts that now is the time to join the astronaut corps.

Pettit and ESA astronaut Andre Kuipers discussed science research currently being done on the ISS, such as human medical experiments. Kuipers was covered with monitoring systems to determine his cardiac response while doing different activities in space. There are also human life studies and engineering research, which Pettit described as “mundane things like how to make a toilet that works and to take the urine and process it and make it back into water… Now you can go into the toilet and the machines will whir and grind and then you can go and make yourself a bag of coffee. We‘ll need these kinds of things if we are going to go far from Earth for long periods of time.”

Watch the video of the entire conversation below.

The Sun Blows Off a Little Steam

A close-up look at the Sun on the last day of 2011, showing impressive multiple prominences with sunspots AR1389 at the eastern limb. Credit: Efrain Morales Rivera, Jaicoa Observatory

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This is an awesome image of the Sun captured by Efrain Morales Rivera from the Jaicoa Observatory in Aguadilla, Puerto Rico, on December 31, 2011. It shows multiple steam-like prominences on the eastern limb of the Sun. Rivera compared them to a group of trees, and said the now-active Sun is definitely something to watch in the coming new year. Of course, the Solar Dynamics Observatory is keeping a close watch on our star, and captured a huge eruption on the western limb of the Sun on January 2, 2012, with lots of solar material ejected into space; however, it was not Earth-directed. See the video below:

Nebula of Many Names Revealed in Beautiful New Image

This image of the Omega Nebula (Messier 17), captured by ESO's Very Large Telescope (VLT), is one of the sharpest of this object ever taken from the ground. It shows the dusty, rosy central parts of the famous star-forming region in fine detail. Credit: ESO

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The Omega Nebula goes by many names, depending on who observed it when and what they thought they saw. So, what do you see in this new image from the Very Large Telescope? This is one of the sharpest images of this nebula ever taken from the ground, and it reveals incredible detail in the smoky-pink gas clouds and dark dust, highlighted with brilliant newborn stars.

Astronomers from the European Southern Observatory said the “seeing” — a term astronomers use to measure the distorting effects of Earth’s atmosphere — on the night of the observations this image was taken was very good, thus this incredibly vivid image.

A common measure for seeing is the apparent diameter of a star when seen through a telescope. In this case, the measure of seeing was an extremely favorable 0.45 arcseconds, meaning little blurring and twinkling occurred while the VLT stared at this nebula.

The other names given to the Omega Nebula include the Swan Nebula, the Horseshoe Nebula and the Lobster Nebula. It also has the official catalog names of Messier 17 (M17) and NGC 6618. The nebula is located about 6,500 light-years away in the constellation of Sagittarius. It is a popular target of astronomers, and is one of the youngest and most active stellar nurseries for massive stars in the Milky Way.

The gas and dust visible in the Omega Nebula provides the raw materials for creating the next generation of stars. The newborn stars shine brightly in blue-white light, illuminating the entire nebula. , The gas appears in pink hues, as the hydrogen gas glows from the intense ultraviolet rays from the hot young stars.

The image was taken with the FORS (FOcal Reducer and Spectrograph) instrument on Antu, one of the four Unit Telescopes of the VLT.

Source: ESO

Beam Me Up, Obama: Conspiracy Theory Claims President Teleported to Mars

Was the 44th President of the United States a time-traveling teenage Mars explorer?

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Forget 2012 prophecies, Mayan calendars and lurking planets that go only by the name “X”… there’s an even kookier conspiracy theory in town, and it has to do with our nation’s fearless leader and his teenage teleportation adventures on Mars.

Yes, you read that right.

It seems that two government employees and self-professed time-travelers – er, “chrononauts” – Andrew D. Basiago and William Stillings have come forth and named President Obama as one of their own, along with the current head of DARPA, Regina Dugan.

(DARPA, if you don’t know, is the agency responsible for keeping U.S. defense up-t0-date with advancements in technology. Begun as a response to the Sputnik program in the late 50s, DARPA finds ways to integrate cutting-edge tech developments into stuff the military might want.)

Basiago, a Washington state lawyer, says that he was part of a time travel program developed by DARPA in the 1970s code-named Project Pegasus. He and Stillings claim that both Obama and Dugan were in their “Mars training class” at California’s College of the Siskiyous in 1980, part of a group of 10 young adults chosen to travel to Mars via a top-secret teleportation “jump room”.

They also claim that the then-19-year-old Barack Obama went by the name “Barry Soetero”.

But wait, there’s more.

"I'll beam ya down Mister President but I'll have to see your birth certificate first." (Photo via startrek.com)

The two former chrononauts also said that they encountered the future president at secret U.S. bases on Mars, which he is said to have visited twice between the years 1981 and 1983. On one instance Basiago said he even exchanged words with Ob – uh, Soetero – en route to the “jump room” while on Mars.

“We’re here,” Basiago claims the young president-to-be said to him.

And the supposed reason for the secret teen task force’s Red Planet expedition? To “acclimate Martian humanoids and animals to their presence,” according to Basiago.

You know, to make good with the locals so there’d be no trouble when setting up camp.

White House officials have denied all allegations of the President’s Martian travels, or the existence of a Mars training class. But, of course, they would. 

And you thought the whole birther thing was a bit extreme? Wake up sheeple, this is some real crazy here. Chrononaut style.

Read more on Wired.com’s “Danger Room”.

 

Top image assembled by J. Major from NASA and Hubble images and a campaign photo of President Obama. Star Trek image from www.startrek.com. © 2010 CBS Studios Inc., All Rights Reserved.

Announcing Our Weekly Live Video Space Hangouts

Weekly Space Roundup

Thanks to the power of Google+ Hangouts on Air, we’re now able broadcast live video hangouts with a worldwide audience.

We’re planning to run these Hangouts on a regular schedule, live on Google+. We’ll post a link when the Hangout is about to begin, but if you want to get notified, make sure you circle Fraser Cain on Google+ – then you’ll see the Hangout in your stream when it has begun.

You don’t need to be a member of Google+ to watch them, we’ll post a public link when we’re getting started here, on Google+, Twitter and Facebook. We’ll post the completed videos to Youtube after the fact.

I’ve put a countdown timer over on the right-hand side of Universe Today, so you can see time until the next video hangout.

We currently have two weekly “shows” planned, with more to come:

Weekly Space Roundup – Thursdays at 10:00am PST

Once a week, we’ll pull together the combined space reporting power of Universe Today, Bad Astronomy, MSNBC, Planetary Society, Discovery.com and other space news outlets to give you an overview of what’s going on… out there.

Join a random collection of space journalists, including Nancy Atkinson, Alan Boyle, Fraser Cain, Pamela Gay, Nicole Gugliucci, Emily Lakdawalla, Ian O’Neill, Phil Plait (and other bonus guests) for a weekly roundup of space news.

We’ll update you on the week’s big space news stories and provide our expert analysis. Since this is live, you’ll be able to participate in the conversation, asking questions to our team.

Astronomy Cast Live – Time to be determined

Watch Fraser Cain and Dr. Pamela Gay record Astronomy Cast as a live Google+ Hangout. Then join us after the show for an actual hangout. We’ll chat with fans about the topic we discussed and answer general space and astronomy questions.

NASA Provides Live All-Sky Video Feed for Quadrantid Meteor Shower

False-color image of a rare early Quadrantid, captured by a NASA meteor camera in 2010. (NASA/MEO/B. Cooke)

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If you are hoping to see some meteors from the Quadrantid meteor shower but are being foiled by cloudy weather or if it’s just too cold outside to get up off your couch, NASA has come to the rescue. The Marshall Space Flight Center has set up a live all-sky camera feed of the skies over Huntsville, Alabama in the US. You can find the Ustream page with the feed here. Reports from Marshall say the weather looks very clear for tonight (Jan. 3) in Huntsville. Tonight is really your best shot to see this meteor shower this year.

If you plan to be a little more actively involved in watching this shower, join in on Meteorwatch, where you can share the experience via Twitter.


Of course, you will have to wait until it is dark in Huntsville to watch the video feed; during the daytime, the feed will just show a dark gray box. The camera is light-activated and will turn on at dusk each evening.

This shower will peak in the early morning hours of Jan. 4. The Quadrantids have a maximum rate of about 100 per hour, varying between 60-200. The waxing gibbous Moon will set around 3 a.m. local time, leaving about two hours of excellent meteor observing before dawn.

Here’s a map of who should be able to see the Quadrantid meteors:

A map of worldwide Quadrantid visibility. Credit: NASA

Red areas will see no Quads, yellow just a few, and green should see a decent shower if they are in dark sky conditions.

Marshall Space Flight Center suggests that to view tonight’s Quadrantids, you should have an area with dark skies well away from city or street lights. Dress warmly and go out just after Moonset around 3 a.m. local time. Lie flat on your back on a blanket, lawn chair, or sleeping bag and look up, taking in as much of the sky as possible. After about 30 minutes in the dark, your eyes will adapt and you will begin to see meteors. Be patient — the show will last until dawn, so you have plenty of time to catch a meteor.

For more info see the our preview article on the Quadrantid meteor shower, or Marshall Space Flight Center’s Quadrantid info page.