The Night Sky This Month: October 2021


Much has been written about how humans might colonize Mars, and even more has been written about the types of habitats future colonists might require to be protected from solar radiation.

Now it seems that a team of researchers has now found a workable, if not elegant solution. Shown in this image is a 3D-printed structure made from what researchers based at the University of Manchester have dubbed “AstroCrete” — which is made up of Mars-type soils, proteins from human blood, and urea derived from human urine.

While the exact “recipe” is not known, the material shown here is significantly stronger than terrestrial structural concrete. Moreover, the best part of this material is that it can be made “on-site”, meaning that the cost of transporting building material to Mars can largely be excluded from the cost of future manned missions to Mars.

The team of researchers has also calculated that during a two-year mission, a team of six astronauts/colonists could produce up to 500 kg of building material. If, however, the AstroCrete is used as mortar between sandbags or similar building blocks, each member of the team can produce sufficient AstroCrete to expand a habitat enough to house one more member. Despite its early promise, though, final tests of this novel building material will have to wait until actual Martian soil is available in meaningful quantities.

The research had been published in the journal Materials Today Bio.

The Moon Phases in October 2021

New Moon First Quarter Full Moon Third Quarter
October 6th October 12th October 20th October 28th

The Planets in October 2021

Planetary viewing is still poor during October, but below are some details of what to expect this month if you are up for the challenge of looking for some of the visible planets low on the horizon.

Mercury is preparing for its finest showing of the year since it is approaching its point of greatest western elongation from the Sun. However, the little planet will not rise to more than about two degrees above the eastern horizon at around 06:00 (BST) from the 20th to the 27th of the month. During this time, the planet will shine at about magnitude -0.4 and have an angular diameter of seven seconds of arc. Also, note that Mercury will only be visible for a few minutes before sunrise, so take great care not to use binoculars after sunrise.

Venus is now approaching its point of greatest eastern elongation from the Sun, and while it will be a full 47 degrees to the eastward of the Sun on the evening of the 29th, it will not rise to more than about 4 degrees above the western horizon at sunset. Nonetheless, for the time that the planet is visible, it will shine at magnitude -4.26 and have an angular diameter of about 19 seconds of arc. Note that Venus will only begin to reach higher altitudes at the start of December 2021.

Mars is now moving towards the Sun, and will therefore not be visible throughout the month of October.

Jupiter has gained some altitude and it will be visible in the southeast after dusk, shining at magnitude -2.71. Note that the planet’s elevation will be about 22 degrees when it crosses the meridian at 22:06 (BST), but it will culminate progressively earlier until, by month’s end, it will cross the meridian at about 19:10 (GMT). By this time, the planet’s brightness will have reduced to about magnitude 2.5.

Saturn starts the month rising just before sunset, and while it will be relatively bright at magnitude +0.47 and measure about 41 seconds of arc across its rings, the planet will only rise to about 18 degrees above the southern horizon when it crosses the meridian at 21:00 (BST).

Meteor Showers in October 2021

The month of October sees two meteor showers, these being-

– The Draconids Meteor Shower is expected to peak in the early evening on October 7th. The shower results from debris left behind by the comet 21P Giacobini-Zinner, and although there will not be any moonlight on this date, this shower typically only produces about ten or so meteors per hour during the peak. While this shower’s radiant is in the constellation Draco, meteors can appear to emanate from any point in the sky.

The Orionids Meteor Shower is expected to peak after midnight on the night of October 21st. While the Orionids originate from debris left behind by the comet Halley, Earth will not move through a particularly dense debris field, meaning that observers can expect to see no more than about 20 or so meteors per hour during the peak period. Moreover, the near-full Moon will seriously affect viewing conditions, and only the brightest meteors may be visible this year. As with all meteor showers, Orionids can appear to come from any point in the sky.

Deep Sky Objects to Look for in October 2021

Prominent constellations at this time include Perseus, Cygnus, Lyra, Aquila, and Cassiopeia, all of which contain a variety of deep sky objects that are easy targets to find and observe with modest amateur observing equipment. Below are some details of few such objects-

Messier 52 (NGC 7654)

Messier 52 (NGC 7654)
Image credit: Radan Mitroviќ (CC BY-SA 4.0)

Located about 5000 light years away in the constellation Cassiopeia, the large open cluster shown here to the left of centre is an easy target even for modest binoculars. Spanning across 19 light years, this cluster has an apparent visual magnitude of 5.0, which sets it off nicely against the Bubble Nebula, which is the reddish cloud to the right of centre.

Bubble Nebula (NGC 7635)

Bubble Nebula (NGC 7635)
Image credit:  NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

This image shows a relatively close-up view of the Bubble Nebula, which is rendered in reddish-brown in the image of Messier 52 above. Located between about 7,100 and 11,000 light years away in the constellation Cassiopeia, the Bubble Nebula is 15 arc seconds wide, and 8 arc seconds across. Look for the nebula close to the border with the constellation Cepheus.

Unlike most other planetary nebulae that are the expanding debris clouds of exploded progenitor stars, this nebula is the result of its very hot and supermassive O-type central star that began blowing its own outer layers off into space about 40,000 years ago. The central star, designated as SAO 20575 and BD+60°2522, is only about 2 million years old, which explains its very high temperature of about 37,500K.

Due to its relative brightness, this pretty nebula is visible in telescopes with apertures of 200mm and larger.

NGC 7789 (Caroline’s Rose / White Rose Cluster)

NGC 7789
Image credit:

Located about 7,600 light years away in the constellation Cassiopeia, this large cluster that spans across a full 50 light years is arguably among the most studied intermediate open clusters within the Local Universe.

With an age of around 1.6 billion years, many of the massive stars in the cluster have just begun to evolve into red giant stars, hence the overall yellow-ish tinge to the inner regions of the cluster. Note that while even small, 50mm telescopes will resolve some structure in the cluster, 160-mm and larger instruments will resolve individual stars in the outer fringes, while 200-mm and larger instruments will resolve the inner regions.

Note that the large, bright blue and orange stars in and around the cluster are not related to the cluster proper.

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