The ‘Blaze Star’ Nova is Imminent

Astronomers, amateur and professional, are excitedly anticipating a ‘new star’ in the heavens sometime in the very near future, perhaps this month or next. Some 3000 light years away T Coronae Borealis (T CrB), also known as The Blaze Star, has given signs of an impending nova explosion. This binary system of two co-orbiting stars, one a large red-giant and the other a small white dwarf, can put on quite a show.

The white dwarf is the remnant of a star originally no more than eight times the mass of our Sun. With not enough mass to maintain the higher temperatures and pressures for ongoing fusion, its ‘nuclear fire’ ceased long ago. It lost its outer layers to space and its core contracted to an extremely hot dense sphere of fusion end-products. It possesses a powerful gravitational field being half the mass of the Sun but compressed to Earth-size, and lives on slowly radiating its residual heat.

The two stars move around each other every 228 days in a circular orbit. Every 80 years the white dwarf relives, albeit briefly, some of its former glory. It draws matter to its surface from the diffuse envelope of its companion red-giant star. As pressure and temperature rises to a critical level, sudden and massive nuclear fusion is triggered on its surface resulting in a powerful burst of energy and brief brightening visible from Earth. The nova event has no effect on the large reg-giant which remains locked in the small white dwarf’s gravitational embrace. While ordinarily a faint star in the constellation Coronae Borealis (the Northern Crown), it will briefly blaze as a ‘new star’. Unlike a supernova that destroys a star, the white dwarf lives on.

Max Planck Institute: Nova Explosion in a binary star system

T CrB is the brightest of ten known recurrent nova. Its last nova was observed in 1946 giving valuable data on the phenomenon. Ten years ago it brightened slightly, and one year ago it dipped a little, both being predicted pre-nova signs. If it follows its historical pattern, after going nova it will very quickly settle back to its normal state and the cycle will begin again as it accumulates more material from its companion to go nova again in another eight decades.  

Learn more at:
The Conversation - Look Up! A once-in-a-lifetime explosion is about to create a ‘new’ star in the sky
NASA – White Dwarf Stars

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Melbourne Sun times

Date	Rise	Set	Day length	Solar noon*
Thursday 1st	7:20am	5:33pm	10:12hours	12:26pm
Sunday 11th	7:09am	5:41pm	10:31hours	12:25pm
Wednesday 21st	6:57am	5:49pm	10:52hours	12:23pm
Saturday 31st	6:43am	5:58pm	11:15hours	12:20pm

^*When the sun is at its highest, crossing the meridian or local longitude.

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Moon phases

Phase	Date
New Moon	Sunday 4th
First Quarter	Tuesday 13th
Full Moon	Tuesday 20th
Third Quarter	Monday 26th

Moon distances

Lunar apogee (furthest from Earth) is on Friday 9th at 405,297 km.

Lunar perigee (closest to Earth) is on Wednesday 21st at 360,196 km.

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Planets

Mercury is not visible from Melbourne this month as it moves to inferior solar conjunction when it will pass in front of the sun.

Venus is now visible as the bright “Evening Star” in the west at dusk before setting by 7pm. 

Mars continues to be seen in the east from around 3am before it fades in the early dawn light by 6am.

Jupiter remains visible from 3am passing across the northern skis after which it too will fade in the early morning light.

Saturn is heading for opposition next month when it will be on the opposite side of the Earth from the Sun. This month it is visible from 9pm in the east after which it will move across the north and then be lost in the early morning light.

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Meteors

This month’s major meteor shower is the Perseids which peaks on the 13-14th although not strong in the southern hemisphere. They are fast, bright, can leave persistent trails, and come from a point below the north-east horizon in the northern constellation of Perseus. These meteors result from Comet Swift-Tuttle which passed near the Sun in 1991 leaving a trail of particles for the Earth to regularly pass through. 

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Stars and constellations

In the north

This month’s evening skies show Virgo and Spica (Alpha Virginis), the 15th brightest star at night and 262 light years away, have moved towards the west, while Leo has largely disappeared below the north-western horizon. However, Libra (the weighing scales) is high in the north and in the north-east is Aquila (the eagle) with its principal star Altair (Alpha Aquilae), the 12th brightest star at night and 17 light years from us.

In the east

Very high in the east after sunset and slowly moving overhead during the night as our planet rotates to the east is Scorpius with its impressive curving line of stars. The central star of the three that form the scorpion’s body is the red giant Antares (Alpha Scorpii) at 34 light years and 16th brightest star at night. Rising behind and following during the night is the centaur Sagittarius with its bow and arrow forming the famous Teapot asterism.

In the south

Standing high in the south-west is Crux, or the Southern Cross. On a moonless night, and certainly away from city lights, can be seen the dark patch known as the Coal Sack nebula, a vast region of interstellar dust that blocks our view of more distant stars. To its left are the Pointers (Alpha and Beta Centauri), the brightest and second brightest stars in the constellation of Centaurus which is the other horse-human hybrid from ancient Greek myth.

Alpha Centauri is also known as Rigel Kentaurus (‘foot of the centaur’) and is the 4th brightest star in the night sky. Until very recently it was thought to be our sun’s nearest neighbour at 4.37 light years. We see what appears to be one star but a modest telescope will reveal it is in fact two, Alpha Centauri A and Alpha Centauri B in close orbit around their barycentre or common centre of mass.

However, bound to these two stars but at a considerable distance is the faint small red-dwarf star Proxima Centauri, known also as Alpha Centauri C. Our nearest star system is therefore a triple system.

Proxima, as the name suggests, is currently the closest star to our sun at 4.24 light years and hosts planets. Announced in 2016 was Proxima Centauri b, a star slightly more massive than Earth and quickly orbiting much closer than Mercury does to our sun. it is presumed to be tidally locked with only one face turned to its star. The second planet Proxima Centauri c was discovered in 2020 and is about seven Earth masses. It lies further out in a five-year orbit and may possess a ring system. A third planet, Proxima Centauri d, was claimed in 2022 with a quarter of Earth’s mass orbiting even closer in a five-day orbit.

Low in the south-east is the 10th brightest star Achernar (in the constellation of the Eridani, the river) which sits at 144 light years from Earth, and in the south-west lies the 2nd brightest star Canopus in the constellation of Carina (the keel) at 313 light years. From our southern latitude both of these stars never disappear below the horizon.

In the west

Low in the north-west is Arcturus, the 3rd brightest star at night and 37 light years from us in the constellation of Bootes (the herder or plower).

Corvus (Latin for crow) sits squarely in the west in the evening this month. In ancient Greek mythology, however, this sacred bird is a raven that perches on the back of Hydra (the sea serpent). The serpent’s nearby head is a little higher up in the west and marks one end of a long narrow body that snakes to the horizon in the longest of the traditional 88 constellations.

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International Space Station

At a distance of about 400km the ISS completes an orbit every 90 minutes and appears as a bright object that moves slowly across the night sky. There will be many visible passes this month over Melbourne and Central Victoria. Here are two expected to be the brightest and highest in elevation;

Morning

Sunday 9th 6:05am to 6:10am South-West to North-East

Evening

Wednesday 14th 7:22pm to 7:26pm West-North-West to South-South-West

Thursday 15th 6:33pm to 6:39pm North-West to South-East

Heavens Above gives predictions for visible passes of space stations and major satellites, live sky views and 3D visualisations. Be sure to first enter your location under ‘Configuration’.

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On this day

3rd 2004, the MESSENGER (USA) mission to Mercury was launched.

4th 2007, Phoenix (USA) Mars lander was launched.

5th 1998, NASA Near Earth Object Program is created to detect and catalogue asteroids that approach Earth.

5th 1939, first person to walk on the moon, American Neil Armstrong, is born.

6th 2012, the Mars rover Curiosity lands on the red planet.

6th 1996, a meteorite from Mars discovered in Antarctica is said by NASA to contain possible microfossils of bacteria.

7th 1959, Discoverer 1 (USA) returns the first satellite images of the Earth.

10th 1675, Royal Greenwich Observatory is established east of London.

10th 1990, Magellan (USA) arrives at Venus and begins radar mapping of its surface.

12th 1877, Astronomer Asaph Hall at the US Naval Observatory discovers Mars’ tracks are clearly eviden.t 12.6km diameter moon Deimos.

13th 1898, Eros, the first near-Earth asteroid is found by Carl Gustav Witt.

17th 1970, Soviet probe Venera 7 is launched to Venus and will send first pictures from the surface of another planet after landing on December 15th.

18th 1877, Mars’ 22.5km diameter moon Phobos is discovered by Asaph Hall.

18th 1868, new element ‘helium’ is found by Pierre Janssen from analysis of the Sun’s spectrum. It is now known to be the second most abundant element in the universe after hydrogen.

19th 1960, two dogs, Belka and Strelka, are launched aboard Sputnik 5 (USSR), and successfully returned to Earth.

19th 1646, birth first Astronomer Royal John Flamsteed who catalogued 3000 starts.

20th 1975, launch of Viking 1 (USA), first probe to land on and study Mars.

20th 1977, Voyager 2 (USA) launched to the planets of the outer Solar System.

22nd 1989, Voyager 2 (USA) discovers positive evidence for Neptune’s rings.

24th 2006, first formal definition of ‘planet’ is debated and vote upon by International Astronomical Union in Prague resulting in dwarf planet status for Pluto.

25th 1609, Galileo demonstrates to the Venetian Doge and officials his improved version of the newly invented telescope.

31st 1913, birth of famous British radio-astronomer Bernard Lovell.