February 2020: A Fond Farewell

In the show this time, we talk to Anais Moller about machine learning to find supernovae for cosmology, Alice Humpage rounds up the latest news, and we find out what we can see in the February night sky from Ian Morison, Haritina Mogosanu and Samuel Leske.

The News

This month in the news: The Spitzer telescope reaches its final days, the National Science Foundation releases the most detailed images of the Sun ever, and SpaceX launches 60 new starlink satellites, with one “experimentally darkened” to lower the light pollution impact.

First, the Spitzer space telescope has now reached the end of its life. The infrared telescope took its final set of data on the 28th of January, and was retired 2 days later on the 30th. The space telescope was launched in 2003, its mission initially supposed to last around 5 years, when the liquid helium cooling the system ran out. Since then, because of its lowered sensitivity, it has been unable to take measurements in the far infrared, and instead has been operating at its lowest possible wavelengths. On the 30th of January, NASA put Spitzer into safe mode, where the telescope’s non-essential systems are shut down.

Next, the National Science Foundation’s Daniel K. Inouye Solar Telescope has released its first images of the Sun . These images are in a higher resolution than ever before and show lots of details of its surface. The image shows a pattern of granules which are convection cells, superheated plasma rising from within the Sun. While these granules look small, they are each about the size of Texas.

Lastly, SpaceX launched 60 new Starlink satellites this month , one of which has been experimentally darkened. Astronomers have been raising concern over the number of satellites being launched as part of the constellation, increasing light pollution and having an impact on observations, as well as increasing the amount of space debris.

There also are concerns within SpaceX about the possible effect on the performance of the telescope. It is unknown how effective the darkening will be until the satellite reaches its destination at the end of February.

Interview with Anais Moller

Dr Anais Moller (Universite Clermont-Auvergne) talks about her work in using machine learning to detect type 1a supernovae. She discusses the expansion of the universe and why type 1a supernovae are useful for measuring this, then explains her work using machine learning to find them. Anais also discusses the some of the challenges of working with large datasets in astronomy, in particular the LSST (Large Synoptic Survey Telescope), a planned optical telescope made to survey the southern sky. Finally she talks about citizen science as a way to work with large datasets.

The Night Sky

Northern Hemisphere

Ian Morison tells us what we can see in the Northern Hemisphere night sky during February 2020.

The Planets

• Jupiter As February begins, Jupiter rises more than 90 minutes before the Sun shining at magnitude of -1.9. During the month it brightens to magnitude -2.0 whilst its angular size increases slightly from 32.5 to 34.1 arc seconds. A low south-eastern horizon will be needed and our views of the giant planet and its Gallilean moons will be hindered by the depth of atmosphere through which it will be observed.
  
  
• Saturn passed directly behind the Sun on the 13th of January and, as February begins, will rise less than one hour before the Sun. Then, equipped with binoculars and a very low south-eastern horizon, it might be glimpsed at magnitude +0.58 in the pre-dawn sky - but please do not use binoculars after the Sun has risen. As February progresses, its magnitude actually reduces very slightly to +0.66 as it angular size increases from 15.1 to 15.5 arc seconds. Saturn crosses the Ecliptic (the path of the Sun across the heavens) in a southerly direction on the 13th, just 13 days before Jupiter reaches this point whilst Mars reaches it on the 1st of February. (Stellariun shows them beautifully aligned along the ecliptic this month.)
  
  
• Mercury passed in front of the Sun (superior conjunction) on the 10th of January and, on the 10th of February, comes to its greatest elongation east, some 18.2 degrees in angle from the Sun. Mercury starts the month at magnitude -1 and dims to magnitude +0.2 by the 14th and will then soon be lost in the Sun's glare. From the 1st to the 14th, its angular size increases from 5.6 to 8.1 arc seconds but its phase (the % illuminated disk) falls from 85% to just 32% - hence the fall in magnitude. On the 1st of the month, it will set about 70 minutes after the Sun and will have an elevation, low in the west-southwest, of ~9 degrees. This will increase until the 10th before it begins to fall back towards the Sun. Binoculars may well be needed, but please do not use them until after the Sun has set.
  
  
• Mars can be seen towards the southeast in the pre-dawn sky at the start of the month. It then rises some three hours before the Sun and will be best seen at around 7am having an elevation of ~8 degrees. It will have a magnitude of +1.4 and a 4.3 arc second, salmon-pink, disk. By month's end it will be seen further round towards the south before dawn and its magnitude will have increased slightly to +1.1. Its angular size will have increased to 5.5 arc seconds but no markings will be seen unless you have access to the Hubble Space Telescope. Lying along the ecliptic it is moving eastwards above the 'Teapot' of Sagittarius and will lie just above its 'lid' on the 24th.
  
  
• Venus is now dominating the south-western twilight sky and appears higher each night, climbing from ~29 degrees above the horizon to more than 38 degrees at sunset. During the month its angular size increases from 15.3 to 18.6 arc seconds but, at the same time, it phase (the percentage of the disk illuminated) decreases from 73% to 63% and so the brightness only increases slightly from -4.1 to -4.3 magnitudes.
  
  

Highlights

• February: find M31 - The Andromeda Galaxy - and perhaps M33 in Triangulum. In the evenings when the Moon is not prominent, the galaxy M31 in Andromeda will be visible high in the south. There are two ways of finding it:

  1) Find the square of Pegasus. Start at the top left star of the square - Alpha Andromedae - and move two stars to the left and up a bit. Then turn 90 degrees to the right, move up to one reasonably bright star and continue a similar distance in the same direction. You should easily spot M31 with binoculars and, if there is a dark sky, you can even see it with your unaided eye. The photons that are falling on your retina left Andromeda well over two million years ago!

  2) You can also find M31 by following the "arrow" made by the three rightmost bright stars of Cassiopeia down to the lower right.

  Around new Moon (23rd February) - and away from towns and cities - you may also be able to spot M33, the third largest galaxy after M31 and our own galaxy in our Local Group of galaxies. It is a face on spiral and its surface brightness is pretty low so a dark, transparent sky will be needed to spot it using binoculars (8x40 or, preferably, 10x50). Follow the two stars back from M31 and continue in the same direction sweeping slowly as you go. It looks like a piece of tissue paper stuck on the sky just a bit brighter than the sky background. Good Hunting!
  
  
• February 3rd - evening: the Moon between the Hyades and Pleiads Clusters. In the evening one could see the waxing Moon, moving towards full, lying to the right of the Hyades Cluster. Aldeberan is a red giant star far closer to us than the Hyades.
  
  
• February 7th - after sunset: Venus lies above Mercury. After sunset, low in the southwest, Venus will lie above Mercury. Venus will not be missed, but to spot Mercury which lies down to its lower right, a low horizon just south of west and perhaps binoculars will be needed - but please do not use them until the Sun has set.
  
  
• February 18th - before dawn: a thin crescent Moon lies just to the right of Mars. If clear around 7 am on the 18th, one will see a thin cresent Moon lying over to the right of Mars. This could be a nice photo opportunity.
  
  
• February 27th - after sunset: a very thin crescent Moon lies down to the lower left of Venus. After sunset on the 27th, and given a low horizon towards the west, you may be able to spot a very thin crescent Moon lying down to the lower left of Venus.
  
  
• February 29th - before dawn: a lineup of Saturn, Jupiter and Mars. If clear around 6:30 am on the 29th, one will see a nice lineup of, from left to right, Saturn, Jupiter and Mars. A low horizon towards the southeast will be needed to spot Saturn.
  
  
• February 1st and 14th evening: The Hyginus Rille. During these evenings the terminator lies close so making it more obvious. For some time a debate raged as to whether the craters on the Moon were caused by impacts or volcanic activity. We now know that virtually all were caused by impact, but it is thought that the Hyginus crater that lies at the centre of the Hyginus Rille may well be volcanic in origin. It is an 11 km wide rimless pit - in contast to impact craters which have raised rims - and its close association with the rille of the same name associates it with internal lunar events. It can quite easily be seen to be surrounded by dark material. It is thought that an explosive release of dust and gas created a vacant space below so that the overlying surface collapsed into it so forming the crater.
  
  

Southern Hemisphere

Haritina Mogosanu and Samuel Leske from the Carter Science Centre in New Zealand speaks about the Southern Hemisphere night sky during February 2020.

Odds and Ends

A recent paper announced the discovery of a fast radio burst, FRB191108, with the Westerbork Synthesis Radio Telescope array. They found that the FRB emission passed through the circumgalactic material of the Local Group galaxies M31 and M33. The Faraday rotation measured for FRB signal was very high, which means that its signal must have been interfered with by strong magnetic fields somewhere along its path.

Looking at the Faraday rotations of other sources within a few degrees of M31 and M33 showed that the galaxies can’t account for a large proportion of it. This must mean that the strong magnetic fields must exist somewhere close to the FRB’s host galaxy. This gives us a clue about the environment required to create FRBs.

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