Over the summer of 2020 the School of Mathematics and Physics at the University of Lincoln took delivery of its first radio telescope. The aim is to have it installed and ready to use for the 2020/2021 academic year. This allows the School to continue to provide real experiments that can be conducted remotely for our physics students.

The radio telescope is a Spider 300A and has a 3m aperture which is designed to make observations around a frequency of 1420 MHz, the 21cm emission line of neutral hydrogen.

Benefits of Radio Astronomy

Two of the key benefits of having a radio telescope is the ability to make measurements remotely and that observations can be made during the day, even if it is cloudy. The longer wavelength of radio waves means that they are not as affected by clouds, atmospheric turbulence and the Sun as waves in the visible part of the spectrum are. This means radio telescopes generally operate at their diffraction limit.

What Can We observe With a Radio Telescope?

By observing the 21cm neutral hydrogen line we are able to:

• Observe the hydrogen content in the sky and of nearby galaxies.
• Variability of radio loud objects, like quasars which are distant galaxies with active supermassive black holes.
• Changes in the Solar output in the radio part of the spectrum that relates to sunspots and Solar activity.
• Rotation curve of the Milkyway by using the Doppler shift in the 21cm emission line. Rotation curves of galaxies was one hints at the existence of dark matter due to their unexpected high rotation velocities.

Above: A map of the 21cm emission in the sky. The brightest horizontal band that can be seen is due to hydrogen in our own milky.

During the last few months the School of Mathematics and Physics Senior Technician (Vladimir Elkin) has spent many of the clear evenings imaging some of the beautiful deep sky objects visible from Lincoln.

M104: The Sombrero Galaxy. An almost edge on lenticular galaxy which is inbetween a spiral and elliptical galaxy. These types of galaxies have very little star formation and are populated by older stars.

M65 & M66: These two spiral galaxies are part of the Leo Triplet which consists of three spiral galaxies. All three galaxies are gravitationally interacting with one another which is driving an increase in star formation within them.

M27: The Dumbbell Nebula. A planetary nebula which is the formed at the later stages of giants stars when they begin to lose their outer layers. These stars have shed their outer layers which are then ionised by the extremely hot exposed cores, later to be come a white dwarf.

M10: Globular Cluster. These objects are tightly packed clusters of stars that are spherical in shape. There is little to no gas in them so there is no star formation and instead should be populated by older stars.

Best objects to view during the summer months?

Unfortunately during the summer months in the UK the amount of usable time for astronomical observations significantly reduces. During the peak of the summer the sky never reaches complete darkness and hinders the number of faint deep sky objects, like nebula, galaxies and clusters of stars, we are able to observe. However, there are still plenty of interesting objects you can view in the sky over the summer, with many only requiring a small telescope of pair of binoculars (if you can keep your hands steady).

The Solar System’s Gas Giants

Both Jupiter and Saturn are available through the summer months from early morning in June to late evening in September. The two planets are easily to recognize naked eye as both are quite bright and appear to have a larger, more extended size compared to rest of the stars in the sky. Saturn, the furthest away and dimmer of the two, shines with an obvious yellowish colour. Typically you will see them rise in the east and set in the west. Even from your own back garden you can see the Cassini Division, a gap in the ring system caused by orbital resonances with the moon Mimas, which is shown in fantastic detail by the Cassini spacecraft below.

M13: The Great Globular Cluster in Hercules

M13 is one of the best examples of a globular cluster that can be observed. Globular clusters are a densely packed cluster of stars that are gravitationally bound together. They are typically found orbiting the central bulges of galaxies in a halo with little gas content. As such they are very old with populations of mostly older red stars. The existence of young blue stars in globular clusters was puzzle for astronomers, as can be seen from the image below taken by Vladimir Elkin in the School of Mathematics and Physics.

To find M13 find the constellation of Hercules and scan your telescope (or eyes depending on how clear your skies are) between the two stars that make up the left hand side of Hercules torso. The below images shows a screenshot from Stellarium where the constellation is upside down in the early part of July. M13 is best viewed in the early summer months as it gets lower in the sky until it is too low to be viewed as you get towards September.

Alpha Herculis

Just below M13 is a fantastic double star, denoted by the white circle in the image below. The two stars are not just a double star visually but are a binary pair, completing an orbit every 3600 years. Naked eye you will see a single source of light, but look through a telescope and you will be able to resolve two individual stars. The first component is red giant towards the end of its evolution while the secondary component is yellow giant star and a yellow-white dwarf star with an orbital period just over 50 days.

Colloquium

by

Professor Donald Kurtz

Jeremiah Horrocks Institute

University of Central Lancashire, UK

Thursday, 30 January, 2020

4pm-5pm, INB3305

In 1926 in the opening paragraph of his now-classic book, The Internal Constitution of the Stars, Sir Arthur Eddington lamented, “What appliance can pierce through the outer layers of a star and test the conditions within?” While he considered theory to be the proper answer to that question, there is now an observational answer: asteroseismology. We are in a time of a significant advance in our understanding of stellar astrophysics with data from the Kepler and TESS Space Missions. These have improved our ability to see pulsations and variability in stars by 100 to 1000 times compared with ground-based telescopes, allowing us to probe stars using asteroseismology. We are seeing as never before: heartbeat stars, the new tidally enhanced pulsators, novel eclipsing stars, spots, flares and magnetic cycles as in our own Sun. Astrophysics that used to be theoretical is now also observational: internal stellar rotation from core to surface; gravitational lensing in eclipsing binary stars; Doppler boosting; multiple pulsation axes; period doubling; tidal excitation in highly eccentric binary stars. Kepler and TESS data for solar-like stars are now comparable to data for the Sun seen as a star, giving us masses, radii and ages for thousands of single stars, allowing determination of their orbiting planets’ sizes, and giving new constraints on stellar evolution theory. It is now even possible to see into the cores of red giants and observe which stars are hydrogen shell-burning and which also are helium-core burning. This talk will introduce the concepts of asteroseismology and show a selection of exciting observational results from the Kepler and TESS missions.

In its opening scenes, the immortal line, “In a galaxy far, far away”, teased the idea of new, unseen worlds in what we would come to know as the Star Wars universe.

From the cold desert moon Jedha and the forest moon Endor, to the rebel headquarters on the jungle moon Yavin 4, moons have played an important part of the Star Wars landscape.

When the first film was released in 1977 these fantastical places really did seem ‘far, far, away’ and as the latest instalment of the Disney franchise is about to hit cinemas, it’s likely that astrophysicists (the ones who happen to be into Star Wars) have debated what the reality of those types of planets being able to sustain life is.

But without access to the Millennium Falcon, the Star Wars moons are outside our reach and we’re left with our own galaxy, which aren’t as far, far away – so could we really inhabit planets or moons away from earth?

While it might sound as unfathomable as Jabba the Hutt on a treadmill, in fact, many of the worlds depicted in Star Wars could exist in our universe – particularly if we colonised the older moons which have become tidally locked to the planet they orbit, and their orbits more circular. Dynamically young moons, despite looking habitable on paper with the right atmosphere and temperature, would likely have significant tides from the much larger planets they orbit; this would cause daily volcanic activity, even before discussing what might happen to any oceans on these moons

In our own galaxy, Kepler-16b is a Saturn sized gas giant orbiting two stars with a combined mass comparable to the sun at a distance close enough for liquid water to exist, known as the habitable zone. However, the planet itself is not habitable as it is too large, but it does have the potential to support a moon; recent research suggests that an earth-sized moon could orbit this binary planet and be habitable, proving that moons orbiting planets just like Tatooine can exist.

Two relatively nearby moons that are strong candidates that could support life are Enceladus and Europa which are moons orbiting Saturn and Jupiter respectively.

Both of these moons are a long way from the Sun and have frozen surfaces which are hostile to life, but the close proximity to their host planets can cause some internal heating, which is thought to maintain the liquid water oceans located under the deep-frozen surface. Enceladus, Saturn’s icy moon can be seen to have large cracks in its surface spewing out water ice from its liquid ocean beneath, powered, at least in part, by the large tides from Saturn.

Now, though, evidence is beginning to show that exomoons – a natural satellite that orbits a planet just like Earth’s own moon, but outside of our solar system – are viable targets for the search for life.

The more work that is done on exomoons and their link to those depicted in sci-fi suggests that it is difficult to form earth-like moons around large planets close enough to their stars that they have earth-like surface properties. For example, a recent study showed that Hot Jupiter’s – large gas giants that are close to their stars – cannot form earth-sized exomoons as they move inwards to their current location close to the star.

A more likely scenario for a planet to have a sufficiently large moon that would be habitable, like those in Star Wars, is if they were smaller planets that came to close to the planet and were captured. We do know this can happen as Neptune captured a dwarf planet with an atmosphere which is now known as Triton.

Triton is in fact larger than Pluto, yet is classed as moon due to being captured by the gravitational field of Neptune. The difference here is that Neptune is a long way from the strong gravitational forces of the Sun. A Hot Jupiter would have to compete against a much closer star in order to capture a moon, making it harder to have an earth-like moon close enough to its star that we could live on the surface.

Despite the exhaustive efforts to detect exomoons none have been confirmed – recently, I was investigating the whether gaps formed in a large ring system around the exoplanet J1407b could have been formed by an unseen exomoon. I ran simulations to see if this would confirm the theory, but it actually showed the opposite.

Hopefully as we do more investigations into our vast universe, these elusive exomoons will become more common, similar to what has happened to the explosion in exoplanet discoveries in the last few decades, which now stands at just over 4,000 confirmed exoplanets.

This is an exciting possibility, and would be a genuine potential for living outside of our own Solar System, but right now we’re not at the level seen in Star Wars.