Archive for the ‘Astronomy, Science’ Category

Nova in Lupus!

September 26, 2016

ASASSN-16kt was discovered in the constellation of Lupus on September 24 by the All-Sky Automated Survey for SuperNovae with data from a 14″ telescope in Chile.

The discovery magnitude was 9.1 with nothing greater than magnitude 17.5 previously known at that location.

I made a visual estimate of the nova at magnitude 6.7 tonight (September 26) from suburban Adelaide with 7×50 binoculars. At the time of writing, only 8 observations by 6 observers had been submitted to the AAVSO International Database including three Australian amateurs: Terry Bohlsen, Rod Stubbings and myself (highlighted at right), two Argentinians (Gustavo Ballan and the near-omniscient Sebastian Otero) and one Brazillian (Alexandre Amorim).

asassn-16ktobssep26lcg

Enter a caption

Other than photometry (visual or image based), amateurs are increasingly taking the spectra of bright novae, and ASASSN-16kt is no exception, with Terry Bohlsen (New South Wales) taking an early spectrum soon after discovery.

These Stellarium screenshots show the location of the nova in Lupus as the south-west sky appeared at around 8pm tonight from Adelaide (wide and narrow field):

Lupus constellation borders.png

lupus-zoomed

The AAVSO finder chart (7.5 degrees) is shown below in a similar orientation:

x16657jv

I was interested to see a request from a researcher, Laura Chomiuk, for high-speed photometry of the nova to:

…to test a recent theoretical prediction of Ken Shen’s: that novae should show fast periodic oscillations in their optical light curves, if gravity waves help expel the envelope.

Time will tell whether the nova has peaked short of naked eye visibility. I hope to make another observation tomorrow night but the forecast does not look favourable for at least a couple of days thereafter.

At least this nova waited for the cloud-dominated winter we’ve just had to pass by.

Another Gravitational Wave detection

June 16, 2016

Another gravitational wave detection by LIGO has been announced!

See https://www.ligo.caltech.edu/news/ligo20160615

The June 15 announcement page points out that while the signal was weaker than the first detection due to the black hole masses being smaller (14 and 8 solar masses vs 36 and 29):

…when these lighter black holes merged, their signal shifted into higher frequencies bringing it into LIGO’s sensitive band earlier in the merger than we observed in the September event. This allowed us to observe more orbits than the first detection–some 27 orbits over about one second (this compares with just two tenths of a second of observation in the first detection). Combined, these two factors (smaller masses and more observed orbits) were the keys to enabling LIGO to detect a weaker signal. They also allowed us to make more precise comparisons with General Relativity. Spoiler: the signal agrees, again, perfectly with Einstein’s theory.

The news release continues:

Our next observing interval – Observing Run #2, or “O2” – will start in the Fall of 2016. With improved sensitivity, we expect to see more black hole coalescences, and possibly detect gravitational waves from other sources, like binary neutron-star mergers. We are also looking forward to the Virgo detector joining us later in the O2 run. Virgo will be enormously helpful in locating sources on the sky, collapsing that ring down to a patch, but also helping us understand the sources of gravitational waves.

Gravitational Wave astronomy does seem to have arrived!

 

LIGO Gravitational Wave detection: the work of many…

February 13, 2016
I think it’s worth noting that 3 of the authors of the LIGO Gravitational Wave detection paper are listed as deceased (two in 2015 and 1 in 2012) and humbling to realise that, especially in a field like cosmology or particle physics, a scientist could spend his or her working life on something like this and never see the sought-after result.
binary-wave
It also emphasises that Science is usually not about a single person working in isolation, but about the work of many people collaborating and competing over a long period of time.
An ABC post about David Blair’s work on this for 40 years further underscores the point.
Congratulations to the hundreds (from the author list alone!) of scientists, engineers, and support people who contributed in some way to the first direct detection of gravitational values 100 years after their prediction from general relativity by Einstein.

DSLR photometry of BL Tel

August 28, 2015

 

 

Today I submitted an August 22 DSLR observation of the long period eclipsing variable BL Tel to the AAVSO international database.

My observation (9.124  (0.031) V), is shown under the cross-hairs in the images: Visual and Johnson V together and V alone.

BLTel-2015-08-22-BDJB-V-Vis

BLTel-2015-08-22-BDJB-V

Minimum should be happening around about now (~Aug 27).

I have images from Aug 25 that I’ll process this weekend. The conditions were less than ideal, but I managed to get some data before the clouds became a persistent problem.

I hope to take some more images this weekend.

Thanks to Peter Williams for prompting me to consider making observations of BL Tel which is nicely positioned high in the evening night sky now.

Another Nova Sgr 2015 No. 2 update

March 30, 2015

I’ve made 10 observations of the nova since March 19, mostly visual, 3 DSLR, one of which has yet to be processed.

The (rather noisy) light curve is starting to show the kind of early oscillations that seem to be common in novae and certainly the last two bright novae I’ve seen. The red fit “line” helps to make this more obvious.

LC-and-20-degree-polyfit-2015-03-31

The cross-hairs are over my most recent observation early this morning.

Nova Sgr 2015 No. 2 update

March 25, 2015

I made visual and DSLR photometric observations of the nova on March 21 and 22. The image below shows the nova before sunrise on March 22.

NovaSgr2015_2_Mar22-arrowed

The light curve shows my most recent submission under the cross hairs.

LC-2015-03-25

 

It appears that the nova has peaked but these objects are unpredictable so we may see some fluctuations yet. The local weather has made observations difficult for the last 3 days.

Nova Sgr 2015: first observation

March 19, 2015

The conditions at 6am today were not ideal: lots of intermittent cloud, or more accurately, intermittent gaps.

I estimated the nova to be at magnitude 4.9. It was substantially brighter than the 53 comparison star and may even have been brighter than the 47 comparison star (AAVSO chart ID 14582KC).

NovaSgr2015-2015-03-20

I marked the observation as “uncertain” (comment code Z on WebObs) and added the comment:

7×50 binoculars;AT LEAST mag 4.9;may have actually been brighter than 47 comp;intermittent cloud

Tomorrow morning, whether permitting, a brighter comparison star may be needed assuming this thing keeps brightening. Getting up early enough to make a DSLR observation would be nice too.

 

 

Nova Sgr 2015

March 18, 2015

There’s a bright nova in Sagittarius (PNV J18365700-2855420 where PNV = possible nova candidate, its discovery designation).

Like the last bright southern nova (Nova Cen 2013), this one was also discovered by John Seach in NSW.

The nova was discovered on March 15 so it’s early days yet. There are 35 observations in the AAVSO International Database.

NovaSgr2015-2015-03-19

I tried to get out to observe it this morning but it was cloudy. When the weather clears I’ll make visual and time-permitting, DSLR observations.

First V1369 Cen estimate for several days

February 16, 2014

It’s been cloudy here for several days and before tonight, my last estimate of V1369 Centauri was on Feb 10 at magnitude 6.2.

V1369CenFeb162014

My latest visual estimate tonight (under the cross-hairs above) was magnitude 6.55, with 6.5 and 6.6 comparison stars.

V1369 Cen light curve update

February 10, 2014

Here’s an updated light curve for the nova:

V1369Cen11Feb2014

My visual estimates are in purple (click the image to enlarge it) and the cross-hairs are over my latest observation. The polynomial fit (degree 30) highlights the overall shape of the light curve. Only visual and Johnson V observations are shown.