Astronomers at CalTech think they might have found evidence for the existence of a planet in the far reaches of our solar system, which has been nick-named Planet Nine.
The discovery was made by looking at the how such a planet might influence the orbits of smaller dwarf planets and Kuiper belt objects.
Out beyond the orbit of Neptune lies a region of the solar system known as the Kuiper Belt. Think of it as an asteroid belt for icy things. There are a lot of lumps of ice out there, some of them so big that we consider them dwarf planets. In fact one of the largest Kuiper Belt Objects, Pluto, was originally classified as our solar system’s ninth planet when it was discovered in 1930. This status lasted until it was demoted in 2006 by astronomers keen to keep the solar system neat and tidy. Given the discovery of several other Pluto-sized “planets” in the Kuiper belt the decision was made by the International Astronomical Union in 2006 to formally define a planet, and this new definition excluded Pluto and its ilk.
In a curious twist of fate the astronomer who led the charge for Pluto’s demotion in 2006, Mike Brown, was one of the astronomers who announced today the discovery of Planet Nine.
So what is it that has led Mike Brown and his co-author Konstantin Batygin to infer the presence of Planet Nine? If you observe the orbits of six of the most distant Kuiper Belt Objects (KBOs) two similarities emerge.
The first is that they all have elliptical orbits that point in the same direction in space. According to Mike Brown “It’s almost like having six hands on a clock all moving at different rates, and when you happen to look up, they’re all in exactly the same place.” The odds of this happening for these six KBOs is around 1 in 100.
Secondly each of their orbits is inclined by the same amount – about thirty degrees below the plane of the solar system, which is also unlikely to happen by chance.
Combine these two unlikely factors and you find that the probability of these alignments happening by chance is around 0.007% which has led astronomers to speculate about what might be causing these orbital similarities.
Brown and Batygin suggest that a very large planet orbiting in an elliptical path very far from the Sun could be the culprit. The mathematics behind this speculation is all pretty solid. In order to account for what we see in the orbits of the smaller KBOs “Planet 9” would have a mass of around 10 times the size of the Earth, and orbit the Sun at an average distance of around 600 astronomical units, or 90 billion kilometers (30 times further than Neptune).
Crucially no direct observation has been made of Planet 9 so far; its presence has only been inferred, and many astronomers have suggested that if Planet 9 did exist then it would have more observable influence on the KBOs. But rest assured, calculations are being made to try and work out where Planet 9 might sit on its half-a-trillion-kilometre-long orbital path, and we’ll be straining our telescopes to try and work out whether it’s real or not.
Mike Brown is adamant though:
OK, OK, I am now willing to admit: I DO believe that the solar system has nine planets.
— Mike Brown (@plutokiller) January 20, 2016
UPDATE: Last night I came up with this new mnemonic which perfectly encapsulates this latest result:
— Steve Owens (@darkskyman) January 21, 2016
It’s taken the New Horizons spacecraft 3462 days (nine-and-a-half years) to fly the 3 billion miles to Pluto in the outer reaches of our solar system. Today at 1250 BST it will make its closest approach, zipping past Pluto at 30,000 miles per hour, gathering data as it does so.
Everything has been building towards this moment for the thousands of scientists and engineers anxiously waiting for images and information about the tiny ice world. But for now it’s all in the hands of the automatic systems aboard New Horizons. It has turned its antenna away from Earth so that it can focus its attention on Pluto and its moons (Pluto has five known moons, Charon, Styx, Kerberos, Nix, and Hydra). This means that we currently don’t have any way of communicating with or receiving data from New Horizons. It’s on its own until the pre-programmed sequence turns its antenna back towards Earth and begins transmitting back to us. We should begin to receive signals again around 0200 tomorrow (Wednesday) morning.
And what do we hope to see? It’s almost impossible to predict what new imformation this flyby will reveal, but one thing’s for certain: the images will get a whole lot better. The picture above was taken on Sunday from a distance of 2.5 million km. That’s 100 times further than today’s closest approach. The best resolution images we’ll take of Pluto today will allow us to resolve down to 100m per pixel, far better than anything we have seen so far. The above image has a resolution of several km per pixel for example.
So will we see anything at 1250 today? While we won’t start to receive the hi-res images until tomorrow, NASA has held back the final image of Pluto taken by New Horizons before its antenna swung away from us. This is a failsafe image, just in case we don’t hear from New Horizons again*. This image will be released today at the moment of flyby, so stay tuned.
Pluto: The Largest Dwarf Planet
When Pluto was discovered in 1930 it was named the ninth planet in our solar system, but then in 2005 astronomers discovered another object out beyond Pluto, which we called Eris. That name – after the Greek goddess of discord – is apt, as it threw the definition of a planet into chaos. Eris, which at the time was thought to be a little larger than Pluto, must surely be a planet too. But what happens when we discover more such objects out beyond Neptune?
This part of our solar system is known as the Kuiper Belt, and is a little like the asteroid belt only icier. There could well be hundreds of these so-called “Plutoids” or TNOs (Trans Neptunian Objects) out there. To avoid the problems of hundreds of new planets, the International Astronomy Union created a definition of a planet in 2006 that deliberately excludes Pluto and all the other Plutoids.
So Pluto went from being the smallest planet to the second largest dwarf planet (after Eris). But recent measurements made by New Horizons have allowed us to recalculate Pluto’s size and it turns out to be larger than Eris, by a whisker.
Eris is 2326km across (give or take a few km). Measuring Pluto is tricky because of its thin atmosphere, which makes the edges of the dwarf planet fuzzy. However New Horizons is close enough that it can make better measurements than we have had before, which put Pluto’s diameter at 2370km. Pluto is now the king of the dwarf planets!
* Flying through space isn’t risk-free. There are lots of tiny pieces of dust and rock floating out there. Due to its incredible speed even a small particle could wipe out New Horizons if it impacts. As we approach Pluto the number of these particles increases, but it’s still highly unlikely that we’ll experience a catastrophic impact. We’ll know for sure when New Horizons re-establishes contact at around 0200 on Wednesday 15 July
We’re currently living through a very exciting time in space exploration, with a small armada of robot space probes visiting previously unexplored corners of our solar system. Here’s just a few of the amazing discoveries we’ve made in the past few weeks.
This year sees us make close encounters with two of the largest dwarf planets, as New Horizons flies past Pluto for the first time, and Dawn continues to orbit the giant asteroid Ceres. All this as the Philae Lander continues to try to make contact with us from the surface of Comet 67P/Churyumov-Gerasimenko as its parent spacecraft Rosetta follows the comet around the Sun.
Each of these missions is very exciting in its own right, but to have all three happening at once is incredible.
Rosetta and Philae Latest
The Rosetta Orbiter arrived at Comet 67P/Churyumov-Gerasimenko in August last year, and the Philae lander descended onto the comet’s surface in November, carrying out its science mission for 60 hours before its batteries died. Rosetta has continued to produce great science since then; its latest scoop was the discovery of what appear to be sink-holes on the comet’s surface.
All this while Philae tries to make contact with us, and Comet 67P begins the outgassing that will eventually form its tail as the comet makes its closest approach to the Sun on 12 August 2015.
The Dawn spacecraft arrived at Ceres in March 2015, after having spent over a year orbiting the smaller asteroid Vesta. Ceres is the largest of the asteroids, so large in fact that it’s considered a dwarf planet, its gravity having pulled it into a spherical shape.
More and more mysteries are arising as a result of Dawn’s asteroid mission including: what are these bright patches inside craters on Ceres’ surface?
and: what’s a mountain doing on an asteroid?
New Horizons Latest
Stay tuned for even better images of Pluto as New Horizons speeds towards its 14 July flyby at close to 60000kph. For now the best images we have of Pluto and its moon Charon are from New Horizons’ Long-Range Reconnaissance Imager, which shows features on the surface of the distant Dwarf Planet, which we’ll see in better detail in the next couple of weeks.
This is on top of all of the other missions going on up in space right now: Cassini continues to send back breath-taking images and data from the ringed planet Saturn and its moons; no fewer than five spacecraft are currently in orbit around Mars – NASA’s 2001 Mars Odyssey, , Mars Reconnaissance Orbiter, and MAVEN, ESA’s Mars Express, and India’s Mangalyaan – while two intrepid rovers – Opportunity and Curiosity – explore Mars’ surface; and our own Moon is orbited by the Lunar Reconnaissance Orbiter.
We’ll add to this over the next few years, as the Juno probe reaches Jupiter in summer 2016, and as the Japanese mission Hayabusa 2 enters into orbit around an asteroid in 2018 and returns a sample to Earth on 2020.
With summer coming to an end in the British Isles we start the return to the dark skies of autumn and winter. Depending on where you are in the country you will have been without truly dark skies for many weeks, maybe even months, as summer evening twilight lasts throughout the night during the summer.
This all-night-long twilight is almost gone throughout the UK, indeed anywhere on the mainland UK can see astronomically dark skies around 1am at the moment. Only the furthest north outpost of the British Isles still doesn’t have that opportunity.
On the island of Unst, the furthest north of the Shetland islands, lies the UK’s furthest-north town, Skaw, at 60°49’N and 00°47’W. This tiny village will see astronomical darkness return at 0043 on 24 August, lasting only 46 minutes until at 0129 the sun’s light begins to creep into the sky again.
The last time that astronomical darkness was seen at Skaw was on 18 April, over four months ago! Indeed this settlement is so far north that between around 13 and 29 June each year they never get out of civil twilight, meaning that the sky’s bright all night long!
Compare this with the furthest south town in the British Isles, Saint Clement in Jersey, in the Channel Islands. Astronomical darkness returned to Saint Clement on 4 July this year, having been absent since 8 June; only four weeks without true darkness!
Such is the effect of differences in latitude that these two settlements, separated by 1299 km, have such hugely different seasonal swings between summer and winter.
Here’s a simple guide for observing the Perseids 2012 meteor shower this year, covering five basic questions:
What is the Perseids meteor shower?
The Perseids meteor shower is the most reliable of the active regular meteor showers that happen throughout the year. A meteor shower is a display of meteors (or shooting stars) where you see lots of them in the space of just a few hours. The Perseids occurs around the same time each year, in mid-August, and during the peak of the shower meteor rates increase from just a few an hour (the background rate that you’ll see on any clear, dark night) up to maybe 100 or 200 meteors every hour for observers in the perfect location. Meteorwatchers in the UK will probably see dozens per hour from dark sites, dropping to a few an hour (still worth watching for) in towns and cities.
How can I observe the meteor shower?
You don’t need any special equipment to observe a meteor shower; just your eyes. Try and get as far from city lights as possible (out into the countryside if you can, or into a local park if not), and get comfortable. You might want to bring a reclining deck chair with you, as that makes meteorwatching much more civilised! Just lie back and take in as much of the sky as possible. If you’re lucky enough to see a good display of meteors, you might see as many as one a minute, maybe more!
Where should I look?
Meteors streak across the whole sky, so you don’t need to look in any specific direction, but of course if you’ve got a tall building or tree that’s blocking the view, or a streetlight nearby that’s a bit glare-y, then put these to your back. The Perseids meteors all appear to streak from a point in the sky (called the radiant) in the constellation of Perseus (hence the name) which rises in the east about 10pm local time, climbing to its highest in the sky towards dawn.
When is it happening?
The peak of the meteor shower will probably happen some time around 1815 and 2045 UT (1915 and 2145 BST) on Monday 12 August 2013, although there are uncertainties here. The peak could happen any time between 1415 BST 12 Aug and 0215BST 13 Aug. This means that observers in the UK might catch the peak of the shower, if it happens after the sky darkens on 12 August. Even on the nights on either side we’ll still see plenty. In fact the peak of the Perseids is several days wide, so you can start meteorwatching early, and carry on well after 12 August, so that even if this weekend is cloudy you’ll almost certainly have a chance to see some Perseids. Whatever night you’re out you’ll see more the later you’re up. Starting after dusk, the meteor rate will increase each night as Perseus climbs higher in the sky towards dawn.
Why do meteor showers happen?
Meteors are tiny bits of space dust streaking through our atmosphere. These motes of dust float about in space and as the Earth orbits the Sun it hoovers them up. Sometimes the Earth passes through a particularly dense clump of dust, and we get lots of meteors, in a meteor shower. These clumps of dust are left behind by comets as the orbit the Sun, their streaking tails leaving behind a trail of tiny rock particles. The comet that left behind the space-rocks that we’ll see in the Perseids meteor shower is called Swift-Tuttle, after the two astronomers that discovered it in 1862.
In the early morning hours (UK time) of Monday 6 August, NASA’s latest Mars rover, the Mars Science Laboratory, or Curiosity to its friends, will land on the red planet after an eight month journey from Earth.
Curiosity is the largest rover ever sent to Mars – it’s about the size of a Mini – and has a huge array if scientific instruments, which will enable it to complete its science missions: to determine if Mars could ever have supported life; to study Mars’ geology; to study Mars’ climate; to plan for a human mission to Mars.
Curiosity will touch down on Mars after a not-entirely-risk-free landing procedure, which uses a heat shield, parachute, engine, and sky crane, a system by which the lander separates from the sky crane, attached by a tether. The sky crane will use its engines to slow it down to almost a dead-stop, and lower the rover gently onto the surface of Mars.
If you want to watch the landing live, NASA and others are streaming it live. Landing is scheduled for 0631 BST, so you’ll have to tune in a bit before that to watch the whole process. You can also follow Curiosity on Twitter.
And if you want to see the red planet yourself, it’s visible low in the west just after sunset, forming a beautiful triangle with Saturn and Spica, the brightest star in the constellation of Virgo. Mars is the right-hand most of the three bright points of light. You’ll only just catch a glimpse of Mars after the sky darkens enough for it to appear, and before it sets around 2245 BST.
I was delighted to hear that two groups from Glasgow were winners in last night’s UK Space Conference‘s Arthur Clarke Awards 2011.
Clyde Space, a “leading supplier of small and micro spacecraft systems”, was given the Arthur Clarke Award 2011 for Achievement in Space Commerce, while the University of Strathclyde’s Advanced Space Concepts Laboratory, which “undertakes frontier research on visionary space systems”, was given the Arthur Clarke Award 2011 for Achievement in Space Research.
Congratulations to both, and it’s exciting to me as a Scot and a resident of Glasgow that these two groups, located within 5 miles of one another, are leading the UK in space research and commerce.