Archive for the ‘Minor Planets’ Category

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.

Chasing an asteroid

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