Strange Quarks

An optical transient, initially designated PNV J19450648+1822422, was found in Sagitta with the NMW-TexasTech survey on August 25 as detailed in the Central Bureau for Astronomical Telegrams. Once confirmed as a nova, the designation was changed to N Sge 2026. It’s also known as V0488 Sge since it is (amazingly) the 488th variable in Sagitta.

Sagitta (Sge), the arrow, propelled by the bow of Sagittarius the archer, is a small constellation in the northern sky below Aquila, as shown in the wide-field Stellarium screenshot above. The approximate location of the nova is also shown.

The first image above results from stacking a hundred or so images, with noise removal, taken on August 27 starting at about 10:05pm with my Seestar S50. The nova is at centre and before discovery would not have been visible in this field.

The second image is a screenshot of photometry (using Tycho Tracker) carried out with a median stack of 42 of the best individual images. The small green squares in the lower left and right quadrants mark the location of the comparison stars I used for the photometry, and these stars are also visible in the first image.

The nova has so far reached a maximum visual magnitude of 6.9, up from its precursor magnitude of 21.3. At the time of writing, this is a plot of most visual observations submitted to AAVSO since discovery, with mine under the crosshairs. It is currently in decline but could very well become brighter again, and as always, we’ll see.

Sagitta fills the field of view of my 8×42 binoculars, and although I observed the location of the nova while imaging it with the Seestar, the nova and comparison star magnitudes, combined with a more than 99% illuminated Moon (effectively full) to the upper right of the field, made a visual estimate very difficult. As Luna rises later over the next few days, visual observation will be easier, but the nova may also be dimmer. The Seestar’s small field of view and sensitive imager provides an effective approach under these conditions.

An AAVSO finder chart suitable for attempting a binocular or telescopic visual observation is shown below, at least until it falls below magnitude 9.

It has been two and a half months since I first wrote about Nova Musca 2026 (V0419 Musca).

The light curve is somewhat more well developed. Visual band data are shown here.

The nine SeeStar S50 observations I made are shown in purple. Tycho Tracker was used for photometry.

Although the downward trend is clear, there’s a fair amount of up and down.

The astronomer’s telegram reported the discovery of a nova, V0419 Mus, in the constellation Musca on May 24 by K. Stanek of the All-Sky Automated Survey for Supernovae (ASAS-SN). Archival data showed the outburst started on May 10. AAVSO sent out an alert notice on May 29.

Last night was the first opportunity I’d had to attempt an observation. Although the sky conditions were far from ideal, between clouds I obtained enough data (19 cloud-free FITS files with Seestar S50) to carry out photometry.

The field containing V0419 Mus (aka Nova Mus 2026) and photometry in progress (nova in cross hairs and reference stars in green at top right) is shown above.

Another faint star in the field led to the need for careful photometry aperture sizing:

The result of photometry is shown in the plot below (under the cross hairs): a visual (Tri-Color Green) magnitude of 7.966 (with error 0.058). The visual (Johnson V) observation about 3.5 hours immediately before of 7.943 (with error 0.024) was submitted several hours after mine by an observer in Queensland, and the visual magnitude 8 (using eyeball + binoculars or telescope) was made about 4 hours later by an observer in Botswana.

There were only around 70 visual band observations as of around midday today, not surprising given the weather and the nova’s very southern declination, along with about the same number of observations in red and blue bands.

Nova light curves often appear quite non-descript and messy early on.

The following 1.2 degree finder chart needs to be rotated about 45 degrees clockwise to match the Seestar images above:

It’s a fairly sparse patch of sky.

The AAVSO Variable Star Index VSX record gives more detail about the nova including visual band magnitude range, currently 19 to 7.7. Novae often have pre-eruption magnitudes of 19 or dimmer.

We’ll see what happens next with V0419 Mus, whether it brightens again or continues to decline.

The day before discovering V1935 Cen, John Seach discovered a nova in Sagittarius, on September 21. It was also discovered independently by two observers in Japan, as described in AAVSO alert notice 907.

V7994 Sgr has so far peaked at around magnitude 6.7 with a pre-outburst magnitude of less than magnitude 23 within a couple of days!

I made a visual estimate of the nova of 6.9 just before 11:30pm last night (September 26), Adelaide time (ACST) with 15×70 binoculars, using 7.1 and 6.8 magnitude comparison stars for reference.

The images above were taken with my Seestar S50 at around 8:30pm, the first resulting from additive stacking of 59 images on the S50. The second shows the nova in cross hairs after further processing and median stacking in Tycho Tracker. Sagittarius is a busy part of the sky!

V7994 Sgr is located near the boundary of Scorpius and Sagittarius, near the “stinger” of the scorpion.

The AAVSO finder chart below must be rotated at least 90 degrees clockwise to match the field above.

So far, as of September 27, 41 observations have been submitted to AAVSO, 19 of which are visual estimates (via telescope or binoculars) shown here (black), with my observation in cross hairs. A couple of observations from imaging devices are also included (green).

John Seach discovered a nova in Centaurus on September 22 2025 (see AAVSO alert notice 906), which appears to have peaked at magnitude 6.4 and is now fading below magnitude 8. Its pre-outburst magnitude was 16.7.

The images above were taken with my Seestar S50, the first resulting from additive stacking of 39 images on the S50. The second shows the nova (V1935 Cen) in cross hairs after further processing and median stacking in Tycho Tracker.

V1935 Cen is located near Alpha Centauri (aka Rigel Kentaurus) as shown in these Stellarium images for approximately 8:30pm Adelaide time (ACST).

Photometry (with Tycho Tracker) from the S50 images gave a visual band magnitude of around 8.1 at 8:15pm on September 26.

The AAVSO finder chart below must be rotated 90 degrees clockwise to match the field above. The bright star bottom is Alpha Centauri.

As I write this (the morning of September 27), 19 observations have been submitted to AAVSO, giving this early light curve, with my observation in cross hairs. Observations are visual estimates from telescopes of binoculars (shown as black) or visual band photometry from imaging devices (e.g. DSLRs, CCDs).

The light curves of the two recent bright southern novae, V462 Lup and V572 Vel, have developed somewhat since I last wrote about them, the first peaking at magnitude 5.2, now 11.1, and the second peaking at 4.8, now 10.3.

T CrB remains quiet and foreboding, low in the early NW evening sky, taunting us with its pre-eruption ellipsoidal variations.

Writing this update reminded me of a long-standing plan to write a nova distance calculator plug-in for VStar, based upon the rate of decline of a nova.

A couple of months ago I was asked to give an update at the July 2 2025 ASSA general meeting about T CrB, the binary star system that is anticipated to reach magnitude 2 or 3 when it goes into outburst as a recurrent nova (one of only 10 known), which it has done a few times before at roughly 80 year intervals.

In the meantime, we had two bright southern hemisphere novae (around magnitude 5) in June, so my T CrB talk turned into an update about 3 novae: T CrB, V462 Lup, and V572 Vel. The second and third were the subject of my last two posts.

My update was followed by a great talk about variable star photometry with the Seestar S50 by a former colleague, Andrew Murphy. The slides for his talk (and a course project) are here, as of 20 July 2025.

Here’s the PDF for the talk I gave, with thanks to Kym Thalassoudis for allowing me to include his images of V462 Lup and V572 Vel:

Here are the Powerpoint slides as well:

We may still be waiting for T CrB, but within less than a month we’ve seen 2 bright southern hemisphere novae: V462 Lup and now PNV J10251200-5331109 (aka V572 Vel)!

Technically it’s still classed as a possible nova (PNV) before spectroscopic confirmation, although there was a positive Gamma-ray Space Telescope observation overnight while I was sleeping.

Australian John Seach (NSW) discovered this (at magnitude 5.7), and Andrew Pearce (WA) independently found it (magnitude 5.5) on June 25 .

This object has eta Carina at its upper left in this Stellarium screenshot, and below it the “false cross” which consists of stars from Carina and Vela.

This smaller field of view provides more detail with 3 stars at the upper left of the false cross asterism (if the cross was standing upright) at bottom of the picture.

The observing campaign for PNV J10251200-5331109 (aka V0572 Vel) reports the progenitor star as likely being a 22.2 blue star with large amplitude variability.

The sky conditions were not great last night, but I estimated the nova candidate at 4.8 through 15×70 binoculars, through gaps in cloud with DSLR photometry pending.

Rotate this 20 degree FOV AAVSO finder chart 90 degrees right to get the false cross asterism in the same orientation as the screenshots above.

This 8 degree FOV finder chart provides the comparison stars of interest at the moment within a binocular field or two.

As I write this there have been less than 40 observations submitted to the AAVSO International Database.

After being away for a couple of days, I read an email yesterday from Andrew Wendelborn (ASSA) before seeing the official announcements, so thanks for the early heads-up Andrew! The timing worked out well in general.

A nova, now designated V462 Lup, was discovered on June 12 by the ASAS-SN survey at magnitude 8.7 and has since risen to around magnitude 5.5. It has apparently not yet peaked. The progenitor star is thought to have been around magnitude 22, and as with all novae, the rapid brightness increase over a few days is impressive (although not as rapid as some).

Lupus, and the nova, are high in the evening sky as shown in this Stellarium screenshot:

The orientation here is at around midnight on June 21 2025 but Lupus is visible from early evening. This Stellarium screenshot shows the region around the nova corresponding to the image at top.

With the help of this AAVSO finder chart I have made a few visual estimates and there is some DSLR photometry pending. The visual light curve as of the early hours of June 21 is shown below with two of my binocular visual estimates in purple, the last one just a few hours ago:

Meanwhile, T CrB is still quiet.