Near and far

Posted: February 23, 2013 in Deepsky, Imaging, Minor Planets, Observing

I’m a little late posting this but I did manage to get a picture of asteroid 2012 DA14 during last weeks close approach.

The evening started clear but clouded over just as me and few other friends from NASTRO were arriving at Hauxley Nature Reserve.  I got polar aligned with the 80mm refractor through occasional gaps in the cloud so that when the sky did begin to clear at around 8.30pm I was able to find the asteroid fairly quickly.

A point of light drifting through the stars in the eyepiece.  It was easily discernible motion at low magnification.  I put the camera in place and took this one minute exposure:

2012DA14

The moving asteroid shows up as a line because of the long exposure.  Then the clouds returned so I felt very happy to have seen anything at all!

2012DA14 ranks as one of the closest astronomical objects I’ve taken pictures of….only spaceweather like the aurora, noctilucent clouds or ISS are closer.  Later that evening I had a go at imaging something much more distant….in fact, it’s the furthest object I’ve ever tried to take a picture of!  Here it is:

3C273

It looks like a star but is really a quasar (and that’s why these objects were initially named Quasi-Stellar Objects) but it is actually the active nucleus of a very distant galaxy.  3C-273 is a mind crushing 2.4 billion light-years away in the constellation Virgo.  That’s about 1,000 times further away than the Andromeda Galaxy.  This quasar is the brightest in the entire sky and one of the nearest to us.  Quasars were more prevalent in the early universe and are an indication how violent the processes at work in the centres of galaxies can be!  Material is falling into a supermassive blackhole and getting shredded and heated in the surrounding accretion disk.  The energy released, in the form of light and other radiation is beamed outwards and we happen to be looking down the beam. Rather like seeing a lighthouse beam sweeping past us.

Checking on my astronomy software…I noticed that another asteroid, called Hera, was also in the frame.  Hera is a foreground object – just under 200 million miles away in the asteroid belt between Mars and Jupiter.

Advertisements

Chasing an asteroid

Posted: February 14, 2013 in Minor Planets, NASTRO, Observing
Tags:

On Friday an asteroid, named 2012DA14, with a mass of about 190,000 tons will zip past the Earth.  For a brief time it will be even closer than the ring of satellites broadcasting weather images and TV signals around the globe.  NASA has great background information and simulations of the event.

2012DA14Flyby

Prior to closest approach 2012 DA14 will be best seen from the southern hemisphere.  The orbit brings the asteroid towards us from beneath the south pole of the planet.  2012 DA14 is expected to be at its closest to Earth – just 27,700 km (17,200 miles) above the surface – at 1924UT (7.26pm GMT).

There is no danger of a collision with the Earth or any satellites.  But amateur astronomers around the world will be trying to catch a glimpse of this rocky visitor near the time of its closest approach.  I’m one of those astronomers hoping for a clear sky on Friday evening so I’ve spent a bit of time preparing myself for the event.

I’m going to try to view the asteroid from Northumberland and at the moment of close approach 2012 DA14 will be below the horizon.  But it is moving very rapidly through the sky and will rise above the horizon in Northumberland at about 25 minutes later.

Here is a chart generated with SkyTools 3 showing the path of 2012 DA14 after it rises in Northumberland on the evening of Friday February 15th.  Note that the times given in the following star charts may be in error by several minutes – the orbit of the asteroid is not precisely determined enough to make timings without giving that caveat.

Asteroid_2012_DA14

To observe the asteroid I’m going to use a small telescope – an 80mm refractor – and choose a part of the sky that I know the asteroid will pass through.  I’ll start looking about 15 minutes before the asteroid is due to arrive at that spot.

The asteroid, predicted to have a brightness of around 7th magnitude at 8pm (just visible with binoculars) will be in the constellation Virgo, close to the border with Leo.  From Hauxley, it probably won’t be possible to see it until it is good altitude above the horizon.  I think I’ll be able to pick it up visually with the 80mm telescope at about 8.20pm as it cruises past the large scattering of stars in Coma Berenices called Collinder 256.  At that time, the asteroid will be tracking across the sky at 37 arcseconds per second.  In other words, it will cover a distance in the sky just smaller than the size of Jupiter every second.  Definitely detectable against the background stars.

By 8.40pm the asteroid will be passing the constellation Canes Venatici – just beneath the familiar seven stars of The Plough.  Larger telescopes will see it tumble past the Silver Needle galaxy (NGC4244) – an edgeways on spiral galaxy glowing at 10th magnitude.  At 9.04pm the asteroid passes close to another galaxy in Canes Venatici;  M106 is a spiral galaxy whose elongated glow will be visible with medium sized telescopes fairly easily.  By this time the asteroid will be shining at 9th magnitude and fading as it recedes from Earth.

After 9.15pm the asteroid is seen against the familiar backdrop of The Plough – probably the most recognisable pattern of stars in our northern sky.  The chart below shows the trajectory of asteroid during a 45 minute period when it should be easier for novice astronomers to locate.

2012da14_plough

At 9.34pm the asteroid passes between two bright stars of The Plough – Alioth and Phad.  This might be the easiest opportunity for inexperienced astronomers to find the asteroid with a telescope.  Although dimmer by a factor of 2 compared to closest approach, it will be much easier to detect with UK based telescopes because it is much higher in the eastern sky.

By 10pm the asteroid is shining at 10th magnitude and travelling across the sky just one-third as fast as it was a couple of hours earlier.    While it remains an easy target for larger telescopes it will continue to slow (relative to the background sky) and fade.  The final chart shows 2012 DA14 as it heads towards Polaris and the north celestial pole of the sky during the early hours of the 16th.

2012da14_draco

Here’s hoping for clear skies, no technical problems with the ‘scope and a hot pizza on a cold night!

Capturing a comet

Posted: January 7, 2013 in Comets, Imaging

I’ve been out of touch with astronomy for various reasons in the past few weeks.  But a brief message from a friend alerted me to a comet in the sky.  A quick check on SkyTools revealed the comet to be C/2012 K5 LINEAR – a small object passing relatively close to Earth at the moment.  Although this comet is too faint to be seen without good binoculars or a telescope I thought it would be worth trying to get some images.

The orbit of the comet around the Sun is tilted to more than 90 degrees to the plane of the Earth’s orbit.  This basically means that K5 LINEAR is moving from celestial north to south in the sky.  The following chart shows the rapid motion of the comet during the next week or so.

LINEAR_Finder

K5 LINEAR is tracking south through a busy region between the constellations Orion and Taurus.  I set up the 80mm Skywatcher refractor on the HEQ5 Pro mount without much hope of getting a great picture.  It was overcast and raining at one point so me and Malcolm had to throw a cover over the whole setup.  But the cloud was quick moving and eventually I got a clear spell lasting more than half an hour.

C2012K5Linear_050113

This image is a composite of 10 one-minute subexposures taken with the Nikon D80 at prime focus of the Skywatcher telescope.  The processing was carried out in DeepSky Stacker and GIMP.

The green colour of the comet is from jets spewing cyanogen (CN) and diatomic carbon (C2) into space.  Both have a distinctive green glow under the action of sunlight in space.

The sub-exposures actually show the rapid motion of the comet across the field of view.  Here is an animation showing the comet as it tracks across the sky at a rate of 10 arcseconds per minute.

K5 was about 0.3 astronomical units away (about 28 million miles) when the pictures were taken.  That rapid motion corresponds to an orbital speed of about 80,000 miles per hour!  (Since the comet is passing through the plane of our orbit, the radial component is almost zero).

Comet K5 LINEAR is already fading as it heads south and away from the Sun.  But 2013 looks like it will be a spectacular year for other comets!  In late February we’ll have a naked eye comet called PANSTARRS in our sky and towards the end of the year – a more dramatic visitor called ISON might give the moon a good run for it’s money.

Blue Moon

Posted: August 1, 2012 in Astrobites, Moon

It’s August 2nd and there’s a full moon in the sky!

That’s an old picture; unfortunately it’s raining so I can’t see the moon right now.  Fortunately, this month we get two full moons, instead of the usual one!

The time between two successive full moons is about 29.5 days – give or take a little.  This means that in most calendar months there can only be one full moon.  However, if a full moon falls within the first day or two of the month then it’s possible for another full moon to fall before the end of the same month.

That’s exactly what’s happening in August; there will be full moons on August 2nd and 31st.  The second full moon on the 31st is called a blue moon…

In the 19th century the Maine Farmer’s Almanac divided the year into quarters and listed the dates of the full moons.  Obviously, the full moon provided much needed illumination for farmers after sunset so they were important.  Normally there’d be three full moons in each quarter of the year, but occasionally there is an extra full moon would fall in a quarter.  Farmers always called the final moon of the quarter the “late moon” and so the third full moon was deemed to be the extra one; they called it a blue moon.  In many cultures the usual pattern of monthly full moons had names like “Grain moon” (August) or “Harvest moon” (September).  The extra full moon which infrequently appeared in the calendar was known as a “betrayer” moon or a blue moon.  The phrase “once in a blue moon”…well, perhaps it’s from this phenomenon.  They aren’t actually that rare; blue moons will occur once every two and half years on average.

One final note; the term blue moon doesn’t refer to the actual colour of the moon.  The moon usually looks white, yellow or orange-red depending on how high it is in the sky (because of how much air the moonlight has to pass through).  However, volcanic eruptions or forest fires can inject just the right size of dust particle into the atmosphere to give the moon (and Sun) a bluish cast.  These kinds of events are also comparatively rare, happening perhaps less often than a blue moon!

Here’s a brief run down of where the planets are going to be in July.  Check out my planetary elongation chart to see when conjunctions are going to happen in 2012.

The Moon

The principal phases of the moon this month are:

Full moon

Last quarter

New moon

First quarter

 July 5th  July 11th  July 19th  July 26th
The Planets

Mercury is an evening sky object and it reaches greatest elongation east of the Sun on July 1st at 26°E.  However, it sets shortly after sunset so is not likely to be seen by UK astronomers.

Venus is a brilliant object, at magnitude -4.5, in the morning sky among the stars of Taurus.  During the first week of July it lies not far from Jupiter and the Hyades star cluster.  Telescopes show Venus to be a waxing crescent and the angular diameter is decreasing as the planet recedes from Earth.

Looking northeast on July 7th at 3.10am. Aldebaran, Venus, Jupiter and the Pleiades make an almost perfect line in the sky.

Earth is at aphelion – the furthest distance from the Sun of the year – on July 5th.  The distance between our planet and the Sun will be just over 94½ million miles that day.

Mars is an evening sky object in the constellation Virgo.  The Red Planet is a fading first magnitude star and it is visible low in the western sky for a few hours after twilight has fallen.  Mars is now so distant that high magnifications on well collimated telescopes will be required to see the gibbous disk of the planet.

Jupiter is shining at magnitude -2.1 in the morning sky before dawn.  It will rise a little earlier each successive morning.  Look for Jupiter near the northeast horizon near the more brilliant Venus.  On the morning of July 15th the Moon will pass very close to Jupiter.  From the south of England the moon will graze [PDF] or completely cover the distant planet.  From Northumberland we’ll get the kind of view shown below.

Crescent moon and Jupiter at 3.10am on July 15th as seen from Northumberland.

Saturn is visible in the evening sky, in the west, for a few hours after dark.  Saturn is marginally brighter than Mars, also in the constellation Virgo.  Saturn is to be found 5 degrees north of Spica, the brightest star in Virgo and about the same magnitude as Saturn.

Uranus and Neptune are best seen in the morning sky.  Uranus shines like a star of magnitude +5.8 in the constellation Pisces.  From exceptionally dark skies Uranus is a naked eye object for keen sighted observers.  Binoculars will show it easily enough.  Neptune resides in the constellation Aquarius and telescopes are required to see this 8th magnitude planet.  The positions of both worlds are shown in the chart below:

Positions of Uranus and Neptune at 2am on July 15th 2012.

Another display of NLCs last night.  Not the best or brightest display but here is a picture taken from Mitford, near Morpeth last night.

As an experiment I took a series of images – 30 in all – covering about 6 minutes in realtime and stitched them into a short animation.  Here is the result:

I wanted to get more pictures but (a) it was a work night and (b) a strange animal kept running at me from the darkness and it seemed to be getting braver with each attempt…

Two views of the Sun

Posted: June 28, 2012 in Imaging, Sun
Tags:

What a great lightning storm in Newcastle today! And a really eventful drive home which at one point involved navigating through a small lake of drifting traffic cones, in much the same way as I used to navigate a spaceship to avoid hitting asteroids in my youth.

The last thing you’d expect on a day like this is to be setting up the telescope to grab some images.  By 8pm the Sun was beginning to peek through the clouds.  I abandoned the Italy-Germany match and got set up in the bedroom because the Sun was too low to see from the garden.

Here is the view in Hydrogen Alpha:

Image

The Sun has been almost blank in white-light in recent days – barely a sunspot to shake a stick at.  That’s all changed now as the next image shows:

Image

Now it’s getting dark and the sky is completely clear.  Now what….bed or noctilucent cloud hunting?  The night is still young and the camera battery is charged.