The Sky Tonight is a monthly update of the amazing things you can find when looking up from here in Western Australia. This section is written by Jacquie Milner, resident astronomer at the Scitech Planetarium.
The casual observer
On the night of Full Moon, Saturday February 11th, the Moon will occult, or pass in front of Regulus, the brightest star in Leo. This is not a rare event, but it doesn’t happen every month, so it’s worth mentioning here in case you get a good view of it. It’s the 2nd in a series of 19 occultations that started late last year and will run until April 2018, but this event and one in May are the only two that Australia will get a good look at. Only people in Darwin and far north Queensland will miss out.
Anyone south of the white line will see Regulus occulted by the Moon. The time of disappearance and the length of the occultation will vary depending on your location. For Perth, Regulus disappears about 8.39pm and won’t reappear until over an hour later at 9.50pm. In Melbourne and Sydney disappearance is around 12.28am Sunday morning, with reappearance an hour and twenty minutes later. So if you see Regulus on one side of the Moon at the start of the night, and it seems to change side later…or even not be there at all…you’ll know why!
The first eclipse season for 2017 occurs in February, but neither of the two eclipses are visible from Australia – we will have to wait until the next season in August for a partial lunar eclipse. The first eclipse in February will be a penumbral lunar eclipse with the Full Moon that will be visible over Europe, Africa and the eastern parts of the Americas, and the accompanying solar eclipse is an annular eclipse with the New Moon that is mostly over ocean, briefly crossing the far south of Chile and Argentina before sweeping across the South Atlantic to end in Angola and the D.R. of Congo. Eclipse chasing is exciting and rewarding, but you must also be courageous and intrepid! Go to Eclipsewise.com to find out more about these events.
Dates of interest
1st Feb – Moon above Venus (brightest) and Mars.
11th Feb – Full Moon will occult (pass in front of) Regulus, brightest star in Leo.
15th Feb – Moon under Jupiter, later evening sky.
21st Feb – Moon to the left of Saturn, morning sky.
1st March – Moon to the left of Mars, evening sky.
Planets to look for
It’s time to farewell Venus from the evening sky for 2017. If you have a telescope it is worth pointing it low to the west at our brilliant neighbour as it swings in between Earth and the Sun for Inferior Conjunction. As it does so it grows larger but shrinks to a slender crescent at the same time, much like the new moon appears to us in the sky. We still won’t be able to see any features on the planet, its shroud of clouds will still reflect too much light back to us but it will look very planet-like. In March it will seem to dive down into the glare of the Sun as it passes between us and the Sun to reappear in the morning sky for the colder months of the year.
Mars is still up in the evening sky as well, and will linger on, not in as much as a hurry as Venus as it is on the far side of the Sun. It looks pretty disappointing in telescopes at the moment. Sadly it’s going to a whole year to wait until we start to get good views of the red planet once again. But Jupiter is now rising mid evening, with Spica in Virgo, and by month’s end will be rising as Mars sets. It is coming up to opposition in March so it’s just starting to get good! Look out for it with the Moon on the 15th, as the Moon, Jupiter and then Spica make a nice little line-up.
Saturn is all by itself in the morning sky at the moment, rising in the early hours but well up before dawn. It’s in between the stars of Scorpius and Sagittarius at the moment, so if you’re not sure where it’s got to, look out for it to the right of the Moon on the morning of the 21st.
Mercury slips quickly out of the morning sky after the first week of February, so if you’re not up at the crack of dawn to catch it then, you’ve missed it until May. Its next evening apparition during March and April is going to be a very poor one indeed and you are unlikely to even see it until it swings back to the morning sky once more.
Constellation of the month
Orion the Hunter
Orion is one of the oldest constellations in the sky. He has always been known as a giant amongst the stars and he is visible to all people around the world, as he lies across the celestial equator. Here in Australia we see him in the evening sky during the warmer months of the year.
Betelguese, often pronounced as “beetle-juice”, is a red giant star that marks one of the shoulders of Orion. Bellatrix is the star on his other shoulder. In the middle are three bright stars in a row that are known as the Belt of Orion. On the other side of these is a bright white star called Rigel (sounds like the name Nigel), which means “Knee”. Between the Belt and Saiph (meaning ‘sword’), which is the other knee, are three fainter stars in a row which are known as the sword of Orion.
There is a pattern within Orion is often called “the Saucepan” by Australians. Don’t confuse it with the big dipper, which is part of Ursa Major, the Great Bear, which is generally too far north for most Australians to see. The Saucepan uses the belt of Orion as the base and the sword of Orion makes up part of the handle, which extends out to Saiph.
There is a meteor shower that radiates out from an area in the northern part of Orion in late October. Known as the Orionids, it is caused by the Earth intersecting the debris stream of dust that comet Halley leaves behind.
Objects for the small telescope
The Great Orion Nebula
One of the most studied regions of the sky, this nebula is so bright that people often mistake it for the middle star in the sword of Orion. But if you look more closely, even with binoculars, a green glow seems to surround this “star”. This is the Great Orion Nebula, a place where we are watching the birth of new stars and even other solar systems. It is also commonly referred to by the popular Messier catalogue name of M42.
The biggest and brightest of these new stars, a group of four stars known as the Trapezium, are powering up the hydrogen gas that makes up the nebula and making it glow bright pink. You won’t see the pink colour through the telescope though – our eyes are not sensitive enough to pick up the colour with such a faint amount of light.
Take some time to appreciate the detail both inside and around the edges of the nebula. There is something for everyone here, no matter how large or small your telescope is.
The Great Orion Nebula, M42, a huge cloud of dust and gas where new stars are being created. The four stars known as the Trapezium lie in the brightest part of the image.
Credit: Bill Schoening/NOAO/AURA/NSF
Supernovae 1987A – 30 years later
On the 24th of February 1987, astronomers in the southern hemisphere looked up and noticed a new star in the Large Magellanic Cloud. The core of a blue supergiant star had collapsed and gone supernovae. A few hours before the light became noticeable on Earth, a wave of neutrinos washed across the planet as well. This was the closest supernova to occur in modern astronomical history so there was much excitement around the discovery and it has been watched closely ever since, even though it is 168,000 light years away.
Supernovae occur in galaxies on a regular basis, and astronomers are able to observe them all over the universe. There are actually quite a few ways that stars can end their life such a spectacular fashion, but most of them involve the star running out of fuel and the core imploding on itself before rebounding out in the explosion of light we are familiar with.
More importantly, supernovae take months to occur. So ditch that movie scenario of it blinking out in an instance! Supernovae 1987A didn’t peak in brightness until May 20th, 80 days after the initial explosion, then it slowly faded away over the next year. It takes days, months, and years even, for stars to die! Not seconds!
The remnants of the supernova are still being studied. It wasn’t a typical supernova, like the one that formed the Crab Nebula in 1054 and shrank down to form a pulsar. There is something there, but it’s not what was expected, so astronomers will keep observing and studying this unique opportunity while they can.
Further reading: List of Supernovae in history
The remnantsof Supernova 1987A, taken by the Hubble Space Telescope in 2011.
Credit: NASA, ESA, and P. Challis (Harvard-Smithsonian Center for Astrophysics)