Astronomers yesterday announced the discovery of the first Earth-sized planet found in the habitable zone of its star. Revelling in the name of Kepler-186f this “twin Earth” was discovered by the Kepler telescope, adding to the 1800 or so exoplanets we’ve already detected.
The Kepler telescope surveys many stars at one time looking at whether the light we receive from those stars dims temporarily. If it does then that could mean its being blocked out by a planet passing across the face of the star. The dip in star light is tiny, a fraction of one percent of the star’s light, but nonetheless we can get a lot of information about the planet and its orbit from this dimming of its parent star.
By measuring how long the star’s light dims for we can work out how fast the planet is going, and therefore how far from the star it is. By the amount of the star’s light that is blocked out we can tell how big the planet is. In fact we can use mathematical techniques to strip out information from a complicated dimming pattern to work out these factors for a family of planets.
And indeed the parent star in this case, Kepler-186, has five planets going round it, named, from closest to furthest, Kepler-186b, -c, -d, -e, and -f. Only the last of these though is orbiting far enough from the parent star to be in the Goldilocks Zone, the region around a star where it is not too hot, not too cold, but just right for liquid water – a prerequisite for life on Earth at least – to exist. And not only that, but the amount of starlight that Kepler-186f blocks out tells us that it’s very similar in size to the Earth, which means it must be a rocky planet like our own rather than a gas planet, as gas planets are much bigger than the Earth.
The parent star Kepler-186 is much smaller than the Sun; it’s a red dwarf star with a mass of 0.48 M☉(solar masses), a radius of 0.47 R☉(solar radii), and a temperature of around 4000°C compared to the Sun’s 6000°C. This means that Kepler-186′s Goldilocks Zone (also known as the habitable zone, or HZ, green above) is much nearer the star than is the case in our solar system. In fact all five of Kepler-186′s planets orbit their star closer than Mercury orbits the Sun, with the most distant Kepler-186f orbiting at a distance of 0.356AU compared to Mercury’s 0.387AU, going round its star every 130 days.
Might there be life?
No one would have believed in the first years of the twenty-first century that this world was being watched keenly and closely by intelligences greater than man’s and yet as mortal as his own; that as men busied themselves about their various concerns they were scrutinised and studied, perhaps almost as narrowly as a man with a microscope might scrutinise the transient creatures that swarm and multiply in a drop of water. With infinite complacency men went to and fro over this globe about their little affairs, serene in their assurance of their empire over matter… Yet across the gulf of space… intellects vast and cool and unsympathetic, regarded this earth with envious eyes, and slowly and surely drew their plans against us.
- an unlikely scenario, borrowed from H.G. Wells’ War of the Worlds
As soon as this planet was discovered (yesterday!) the Search for Extra Terrestrial Intelligence (SETI) trained their Allen Telescope Array on the star in the hope of hearing a message from an intelligent civilisation. So far: nothing. However in order to be detectable to us here on Earth the Keploids would have to be transmitting at 10x the power we do when beaming signals at potential alien civilisations.
Another route to detecting life – any kind of life, not just the intelligent kind – is to use powerful telescopes to study the planet’s atmosphere. If there’s oxygen there then it must be being produced by plant life; if there are industrial pollutants there (like CFCs that don’t occur naturally) then something would have to be making them. However our scopes are not powerful enough to see the atmosphere of Kepler-186f yet, partly because it’s so far away: 490 light years from us.
E.T. Phone Kepler-186f
Even if we did find evidence of intelligent life on this twin Earth, it’s so far away that communicating with it would be terribly slow. Limited as we are in this universe to sending signals at the speed of light, this planet is 490 light years away, and so the conversation would go something like this:
US: “Hello, how are you guys?
[wait 490 years for them to get the signal]
[wait for them to translate the message]
[wait 490 years for their reply to reach us]
THEM: “Fine thanks, how are you?” [980+ years later...]
As you can imagine if it takes light that long to get there, it would take our spaceships even longer. The furthest we’ve ever sent a spacecraft out into space (Voyager 1) is 19 billion km, which sound pretty far, but is only 35 light minutes away. And Voyager 1 has been traveling for 37 years. 37 years for 35 light minutes. That means it would take Voyager 1 around 270 million years to get to Kepler-186f…
Finding Kepler-186 in the sky
Where can you find Kepler-186 in the sky? The short answer is: you can’t. It’s far too distant and faint to be seen with anything other than the most powerful of telescopes, but you can see roughly where it is by looking in the constellation of Cygnus the Swan.
Cygnus is low in the north-east as the sky darkens, rising to high in the east by dawn, and looks like a large cross, with the long leg of the cross representing the swan’s neck, the short leg of the cross being its tail, and the two arms of the cross being its wings. The bright star in the “right wing” (the higher one) is called δ Cygni and Kepler-186 is near this star, towards the tail of the swan.
The discovery if this twin Earth is very exciting, but it’s just the very start of our exploration of exoplanets (planets beyond our solar system). The star that Kepler-186f orbits is a red dwarf, a very typical star. approximately 70% of the 300 hundred billion stars in our galaxy are of this type (called M-type). If only one in a thousand of these stars has a planet like Kepler-186f that still leaves 200 million Earth twins in our galaxy, and some of them might be closer to us, making them easier to study, and perhaps to talk with…
Starting tonight and peaking next week on 22/23 April 2014 is our spring season’s best meteor shower, the Lyrids. It’s not nearly as dramatic as the Big Three meteor showers – the Perseids in mid-August, the Geminids in mid-December, and the Quadrantids in early January – but dedicated meteorwatchers will catch glimpses of plenty of shooting stars overnight around or after midnight on 21/22 or 22/23 April.
The peak rate (more correctly the Zenith Hourly Rate) of the Lyrids is around 20 meteors per hour, but that’s under ideal conditions: 100% clear skies, zero light pollution, and the radiant (the point at which the meteors appear to emerge from) at the zenith (directly overhead). In the nights leading up to the peak you can still expect to see a few but the ZHR is much lower, around 5 meteors per hour.
So how many Lyrids can we expect to see from the UK next week at the peak? To work this out we’ll have to make some assumptions, and then crunch some numbers.
Let’s assume clear skies at least. Then we’ll assume that the peak will fall either some time between dusk on 21 April and dawn on 22 April or some time between dusk on 22 April and dawn on 23 April (currently the suggestion is that it’ll be pre-dawn on 22 April, but it’s worth watching out on both nights). Finally we’ll assume that the ZHR at the peak will be around 20.
The only limiting factors then are (a) the height of the radiant above the horizon, which changes as Lyra rises in the east, climbing high in the south by dawn; and (b) the light pollution
|Time||Height of Radiant*||Hourly rate if peak occurs at this time|
|2200 21 or 22 April||18°||6|
|2300 21 or 22 April||25°||8|
|0000 21 or 22 April||32°||11|
|0100 22 or 23 April||40°||13|
|0200 22 or 23 April||49°||15|
|0300 22 or 23 April||57°||17|
|0400 22 or 23 April||65°||18**|
|0500 23 April||71°||19**|
* This is based on my observing location in Glasgow, but it’ll only be a few degrees out .
** The last quarter Moon rises around 0330 and so will create enough light pollution to significantly reduce these numbers.
|Location||Limiting Magnitude||Divide above hourly rates by…|
These graphs of previous years show the how the Lyrids activity rate increases and decreases with time centred round a peak on 22 or 23 April:
What is a meteor shower?
A meteor shower is a display of meteors (or shooting stars) during which you see lots of them in the space of just a few hours. Meteor showers occurs around the same time each year, and during the peak of the showers 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 viewing the most active showers.
How can I observe a 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. Meteors in one shower all appear to streak from the same point in the sky (called the radiant), which sits in a specific constellation (which is how meteor showers get their names). However you don’t need to be facing the radiant as the meteors can appear anywhere in the sky.
When do meteor showers happen?
There are many meteors showers every year, occurring regularly on the same days. The International Meteor Organisation (IMO) have a good calendar of the year’s showers, and you can find plenty more information just by googling “meteor showers 2014″, for example. Some of the very best meteor showers are: the Perseids (occurring in mid-August); the Geminids (occurring in mid-December); and the Quadrantids (occurring in early January). These showers can produce rates of up to 100 shooting stars per hour. One thing to bear in mind is that if the moon is in the sky and is anything other than a thin crescent its light will drown out many of the fainter meteors, so make sure you go meteor watching when the moon is as new as possible.
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. For example, 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.
There are only two International Dark Sky Islands in the world, and both of them are in the British Isles: Sark in the Channel Islands; and Coll in the Inner Hebrides.
These beautiful short films show what you’ll see on a clear night:
I’ve visited both islands several times, and they’re beautiful places, and not just at night when the stars come out. They’re very different: Sark is lush, with hedgerows and country lanes, and at 49°25′N latitude its climate is very continental. Coll on the other hand is almost entirely treeless, it’s rugged, boasts long sandy beaches, and lies at 56°38′N. Contrary to common impressions of the weather on the west of Scotland, Coll is one of the sunniest parts of Scotland and so has, like Sark, a high number of clear dark nights.
And it’s on dark nights when these islands are at their most stunning. Now that summer’s on its way though the dark nights will shorten and eventually disappear altogether until autumn, so you’ve plenty of time to plan your visit. Sark has a longer dark sky season, running from August till mid-May, as opposed to Coll’s which runs from September till mid-April, but the nights are longer on Coll than on Sark during the darkest winter months, the best time for stargazing.
Make sure that if you’re going to Sark or Coll for stargazing that you avoid the bright moon. Ideally you would be there during a new moon or thin crescent; at the very least you should avoid the week on either side of the full moon. To maximise your chances of seeing the wonderful dark skies make sure you stay for several nights!
This week the red planet Mars reached opposition, making it best placed for observing. Opposition is, as the name suggests, the point where a planet is directly opposite the Sun in our sky.
This means that Mars is up all night long at the moment, rising as the Sun sets and setting as the Sun rises, and so you should be able to spot it whatever time of night you’re out.
Mars reached opposition on 8 April, but on 14 April it will reach its closest approach to Earth, at a mere 57.4 million miles!
On that night – and on nights near that date – the planet Mars will shine very brightly at magnitude -1.5, brighter than anything else in the night sky except the Moon (which is Full on 14 April, and sits near Mars) and Jupiter.
Mars also looms larger than normal when seen through a telescope, at a whopping 15″ (15 arcseconds = 0.25 arcminutes = 1/240 of a degree!). Stargazers with a decent sized telescope, good observing skills, and good observing conditions should be able to make out the north polar cap of Mars which is tilted towards us at the moment.
Through a small scope you might catch it looking like this:
Last night, Thursday 27 February 2014, the UK was treated to one of the best displays of Northern Lights in the past twenty years. Twitter erupted with excitement, and then pictures, which my good friend @VirtualAstro and myself @darkskyman RT-ed and commented on throughout the evening.
Below is just a sample of some of the best images that came in last night, but before that let’s look at why this aurora display was so good.
Two days previously a large sunspot on the surface of the Sun erupted with a huge X-class flare, rated at X4.9, the strongest of the year so far. This flare blasted off material from the Sun’s surface in what’s known as a Coronal Mass Ejection (CME). We knew that this material wasn’t aimed straight at us, but last night, two days after the eruption, it sideswiped the Earth, getting caught in our magnetic field and funnelled to the north and south poles.
It just so happened that the angle of the impact, and the timing, was perfect for evening skywatchers across the UK, and with largely clear skies across the country reports started coming in around 7pm that we might be about to see storm level activity. In the end it was rated as G2 (moderate) but the position of the auroral oval meant that even this moderate storm produced some of the best views of aurorae in the UK that I can remember.
Don’t be downhearted if you missed it; there’s a chance (55% according to NOAA) that we might see more tonight as we move through the wake of the CME. It’s unlikely to be as good as last night’s show, but still worth a look.
I tweeted the best way to see the aurora:
Then images started coming in!
This from @garethpaxton in Central Scotland (a pic of the viewfinder of his camera):
Then this beautiful one from Jim Hunter Images in East Lothian:
From @ross1772 in Newmill, Scotland
Dave @makapala uploaded a bunch of images taken from Fife to his Flickr account:
Mark Tait @marktait78 got this amazing image from Aberdeenshire, showing the verticality of the aurora:
England also got some of the action with the aurora stretching as far south as Uttoxeter, in this image by @RichardH082:
And Whitby (from @whitbyglenn)
From Ravenscar (from @andy_exton)
And NE England (via @Astro_Matt27)
Northern Ireland got in on the action too, as this amazing image from Paul Martin shows:
But of course the best of it was in the north of Scotland, such as this stunning image from Innes Mackay in Lewis:
After the discovery recently of a supernova in the Cigar Galaxy, M82, it looks like we have another supernova candidate in a different galaxy M99.
Seen just three days ago, astronomers are still trying to work out whether this is indeed a supernova; it should be confirmed soon.
It’s been measured at magnitude +15.4 recently, much fainter than the nearby supernova in M82, which currently stands at brighter than +10 (over 100 times brighter).
You’ll catch the supernova in M82 using just a modest telescope, while the new potential supernova in M99 you’ll need a big scope to see it.
Happy supernova hunting!
UPDATE: It’s been confirmed as a supernova and has the designation SN2014L