Extrasolar planets -- 1 year later

Last October (2010) I wrote a post on extrasolar planets. At that time almost 500 planets beyond our Solar System had been discovered. In the past year, 200 new planets have been confirmed, so I decided it's time to update the chart!

There are a number of recent discoveries around 10 Earth masses (0.03 Jupiter masses) and an over abundance of planets at 0.05 AU (7 million kilometres) from their parent Sun, the well-known 'hot Jupiters'. There is another class of cooler giant planets around 1-5 AU. Several 'super Earths' discovered by micro-lensing can also be seen on the chart.

Will there be 1000 known planets when I update the chart in autumn 2012? Let's see!

Pluto's 4th moon

Recent Hubble images have revealed a new moon orbiting Pluto, the fourth so far discovered around the icy dwarf planet. P4 as the moon is currently known, is the smallest so far discovered at 15 to 30km across, and lies between Nix and Hydra, two small moons discovered in 2005.

Moon	Mean distance (km)	Period (d)	Year of discovery
Charon	17,540	6.387	1978
Nix	48,710	24.856	2005
S/2011 P1	~59,000	32.1	2011
Hydra	64,750	38.206	2005

The moon was unexpectedly found during an observing campaign to find rings around Pluto, which remain undiscovered. The new moon was first seen in an image taken on the 28th June and will be further studied during NASA's New Horizons mission, scheduled to fly through the Pluto system in 2015.

Links

• Astronomy Now news story
  
• Hubble Space Telescope press release
  

A foray into Spectroscopy

In January I acquired a `Star Analyser 100 spectroscope', a diffraction grating which screws into a 1.25-inch eyepiece just like a colour filter. Well, here are my first results captured with an Imaging Source DFK21 camera and processed with Valerie Desnoux's Visual Spec software which is excellent (and free!).



I used Sirius (spectral type A0V) to calibrate the image which has a resolution of 10.5 Angstroms per pixel. The final spectrum (green) is shown between 4000 and 7000 Angstroms (note my response curve has sadly missed the Halpha line at 6563 Angstroms) based on 17 seconds of raw video. The black curve shows a reference red supergiant spectrum of class M2.

Also shown for interest are the Balmer series of H lines (red) and Ti lines (blue).

Links

• Valerie Desnoux's Visual Spec page.
  
• Robin Leadbetter'sspectroscopy links.
  
• More spectroscopy links
  

AstroFest 2011

For 2 days each year at the start of February, the UK astronomy magazine "Astronomy Now" organises a national festival celebrating recent news in astronomy and bringing amateurs together to hone their skills. This year I was lucky to visit the conference on both Friday and Saturday and there were some excellent talks on Phobos and Deimos (Emily Baldwin), epsilon Aurigae (Nathalie Thureau), Uranus & Neptune (Chris Arridge) and the Moon (Chuck Wood) amongst several others. Sadly I missed the principal galactic astronomy talk by Gerry Gilmore of Cambridge University because session 4 (Saturday afternoon) was already sold out.

I also enjoyed the trade stalls in particular those of the BAA and Ian King Imaging/Shelyak Instruments, the latter a French company specialising in spectroscopes for amateur astronomers. I would love to buy their LISA instrument but the Star Analyser is more realistic for my budget/telescope!

Ian Ridpath during the Friday afternoon session interval

Nathalie Thureau describes the CHARA infra-red interferometer

"It's not Rocket Science", a very amusing space-themed comedy show by Helen Keen (Radio 4 in March/April)

Links

• AstroFest 2011 blog
  
• epsilon Aurigae press release at the University of St Andrews
  
• Uranus Pathfinder
  
• Helen Keen, writer & comedian