Astrobiology news: A link between terrestrial extinctions and the Milkyway galaxy?

A new paper has been published by Dr Michael Gillman (University of Lincoln, School of Life Sciences), Dr Hilary Erenler (University of Northampton, Faculty of Arts, Science and Technology) and Dr Phil Sutton (University of Lincoln, School of Mathematics and Physics) in the International Journal of Astrobiology.  The paper “Mapping the location of terrestrial impacts and extinctions onto the spiral arm structure of the Milky Way” looks at data from asteroid impacts, as well as other significant historic changes in the climate of Earth, and the location of the Solar System in the Milkyway galaxy. It was found that asteroid impacts, relating to mass extinction events on Earth, were clustered around the passages through the higher density regions of the spiral arms. As stars orbit the centre of galaxies they pass through the dense spiral arms (caused by density waves). Stars that move closer to one another can gravitationally disrupt one another’s planetary systems. Objects from the outer parts of the Solar System can then be pushed onto orbits that take them into the inner Solar System and collide with planets. In extreme cases the close passes of stars can ejected planets from the system completely. Any gas orbiting around the galaxy is compressed as it moves into the spiral arms, which accelerates star formation. Typically star formation is observed to occur more rapidly in spiral arms of galaxies. This also poses other threats to life as large stars do not live very long after formation (in astronomical terms). They actually go supernovae before they have passed out of the spiral they formed in. Nearby supernovae explosions are also thought to have a significant impact on any life.

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Above is an image of spiral galaxy NGC 3344 taken by the Hubble Space Telescope. The dense spiral arms and clearly be seen, which are similar to our Milkyway.  The red regions centred around the spiral arms are ionised hydrogen gas and areas of active star formation.

The movement of the Sun and the Solar System in the Milkyway galaxy is on very long timescales, but is it something we should be thinking about in the future?

Abstract

High-density regions within the spiral arms are expected to have profound effects on passing stars. Understanding of the potential effects on the Earth and our Solar System is dependent on a robust model of arm passage dynamics. Using a novel combination of data, we derive a model of the timings of the Solar System through the spiral arms and the relationship to arm tracers such as methanol masers. This reveals that asteroid/comet impacts are significantly clustered near the spiral arms and within specific locations of an average arm structure. The end-Permian and end-Cretaceous extinctions emerge as being located within a small star-formation region in two different arms. The start of the Solar System, greater than 4.5 Ga, occurs in the same region in a third arm. The model complements geo-chemical data in determining the relative importance of extra-Solar events in the diversification and extinction of life on Earth.

Physics of snooker on BBC radio 4

Dr Phil Sutton

Today I will be on the BBC radio 4 programme Inside Science  at 16:30, repeated also at 21:00.  We briefly discuss some aspects of the physics involved in snooker from simple newtonian mechanics to non-trivial differential equations that can only be solved by computer simulations. No matter how much we as can understand the game as scientists it unfortunately does not carry over to being a proficient player. In there are so many variables that professional players perfect their skills through practice instead of relying on the science.

The episode can also be listened to here after today.

More details about some of the physics in snooker can be found from my previous work at Loughborough University with the following link: Snooker Physics

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Inaugural physics cafe at The Kings School Grantham

Dr Phil Sutton

Today I visited The Kings School in Grantham to talk about my current and future research interests with students. This was the first of their physics cafes where lecturers are invited to talk to the students in an informal setting and current topics in physics.

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I briefly talk about Saturn’s rings and my own interests in the narrow F ring (illustrated below with the two nearby moons Prometheus and Pandora. Then we moved on to other topics like gravitational waves and how the Earth’s climate might be altered by the movement of the Sun in the Milkyway.

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We finished with some cake and the students asking questions on various areas of astrophysics from pulsars to exoplanet detection methods.

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Studying The Stars To Understand The Universe

EXPERT COMMENT: How we’re using the largest ever recorded set of galactic data to study the stars

Astrophysicist Dr Phil Sutton explains the possibilities opened up by new data from the European Space Agency’s Gaia satellite.

The Gaia satellite. After 22 months of observations, the second release of data contains the position and brightness of 1,692,919,135 stars

The Gaia mission is a space-based observational survey of over 1 billion stars in our local neighbourhood, the Milky Way (pictured above).

It will measure the precise position of stars using a technique known as astrometry.

This will give a detailed three-dimensional map of the Milky Way and is complemented by spectroscopic measurements of the same stars.

Here, along with the precise position of stars in the Milky Way, the Doppler effect is used to find relative velocities of stars by a shift in wavelength of their observed light.

The result is a detailed kinematic map of stars in our local neighbourhood, which is important, as we still do not fully understand why stars move the way they do in galaxies.

Observations dating back to the 1930’s suggested that the rotation curves of galaxies do not fit with Keplerian orbits.

For planets and asteroids in the solar system, their orbits are generally well understood and follow Keplerian laws.

However, at a galactic scale, it was found that galaxies rotated far too fast for the matter we could see.

This discovery led to the concept of dark matter, which is needed to increase the orbital velocities of stars in galaxies.

Along with the increased orbital velocities, stars are also observed to exhibit some randomness to their motion around the centre of galaxies.

Obtaining a detailed kinematic map of our own galaxy can help us refine our current understanding of complicated dynamics within galaxies.

Future results from Gaia are likely to shape the future research of many astrophysicists.

For myself, I am currently looking at how the movement of the Sun, specifically the passage through the spiral arms, can affect the Earth.

This can be through enhanced Milankovitch cycles or gravitational scattering of solar system objects caused by close encounters with other nearby stars.

Much of our understanding of the universe comes from how we observe astronomical objects move relative to us and one another.

Therefore, creating the most detailed kinematic map of the Milky Way will help us appreciate objects we cannot see and physics we currently do not understand.

I also have an interest in gravitational waves and the types of objects that act as sources and other objects that we can use to detect their presence.

The main science goal of another space telescope survey Kepler was to find new planets around other stars.

It succeeded with now thousands of planets discovered and confirmed.

 

However, secondary to the main mission it also discovered many new types of variable stars, like the heartbeat star.

Due to the nature of the Gaia mission and its measurements various other secondary science is possible.

For example, the detection of certain frequencies of gravitational waves, help constrain the cosmological constant (the rate at which the universe is known to be expanding) and even survey a large number of asteroids in the solar system.

Gravitational waves are of interest to astrophysicists as they exist over a very broad range of wavelengths.

At some of the smallest scales, compact binary systems comprised of black holes or neutron stars or neutron stars can have wavelengths on the order of km, while gravitational waves from the early universe in the form of a polarisation of the Cosmic Microwave Background can wavelengths on the order of mega light-years (1,000,000 light years).

Detecting different wavelengths allows us to probe different physics and astronomical objects and get a better understanding of the universe we reside in.

 

The above article was written as part of a press release by Loughborough University. Original press release can be found here.

Historical First Astronomy Observation At University Of Lincoln

On the evening of 15th February Students studying physics at the University of Lincoln carried out their first observations of the night sky. This was the historical first practical astronomy session with the aim of expanding our practical element for you physics students. On the roof of the Isaac Newton Building students used a 8 inch (203mm) Schmidt-Cassegrain reflecting and 4.75inch (120mm) refracting telescope to view various interesting astronomical objects. Even in the centre of Lincoln we were able to clearly observe Orion’s nebula. A deep sky object which is a cloud of gas and dust illuminated by nearby young hot blue stars that have recently formed.

The plan is to loan out some of our telescopes to allow students to make their own observations in their own time.

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