Earendel – The Most Distant Star Detected

The star Earendel is located at the point of the arrow in the image above, surrounded by the light from diffuse and distant galaxies.

The NASA Hubble space telescope has imaged the most distant star ever detected at a staggering 12.9 billion light years away. The light captured from Earendel (dubbed the ‘Morning Star’) is a snapshot from an epoch when the universe was only 1 billion years old, making it significantly older than the previous furthest star detected by Hubble in 2018. (That star was dated to 4 billion year after the big bang).

Normally stars at such immense distances would be undetectable, but its discovery was aided by the gravitational distortion from distant galaxy clusters, magnifying the star and its host galaxy in a phenomena called ‘gravitational lensing.

An example of a distant galaxy, revealed by the distortion of space (and therefore light) near a closer area of high mass, in the form of a galaxy cluster.

Gravitational lensing is analogous to the refraction of light from a glass lens, magnifying and revealing objects that would normally be occulted by closer structures by the bending of space near areas of high mass – like galaxy clusters. Sometimes duplicate images of the same object can be seen, creating copies of the object along symmetrical arcs. The image below illustrates this effect on a star cluster which appears either side of Earendel.

A closer image of Earendel with a mirrored image of a nearby star cluster created by gravitational lensing

You might wonder how immense distances like this can be calculated given the complexity and uncertainty in pin pointing the distance to relatively close stars, let alone objects billions of light years away?

The principle tool used to measure these vast distances is an object’s spectral redshift – a measure of how much its light rays have been stretched (made longer) due to the fabric of space itself being stretched the further away we observe. Larger redshifts indicate objects that are further away – a relationship first accurately established by Edwin Hubble when cataloging the spectra from many distant galaxies.

A measured spectra shifted towards the red end of the spectra, signalling longer wavelengths and higher recessional speeds.

Given the redshift of an object we can calculate its recessional speed (related to the global expansion of the universe) and from this its distance can be determined using the Hubble’s constant Ho. These calculations can be set out very simply:

V (recessional speed) = Red-shift x Speed of Light

In the case of Earendel the detected redshift from its spectra was 6.2. Therefore:

V (Earendel) = 6.2 x 300 million m/s = 1860 million m/s.

It’s important to note that this speed is faster than the speed of light! How can this be? Well this is actually a measure of the speed that space itself is expanding. Light cannot travel faster than 300 million m/s – our cosmological speed limit – but there is no limit on the rate at which the fabric of space can expand. In fact for general relativity to work space must be permitted to expand at potentially unlimited rates.

From the recessional speed we then use Hubble’s law to find the distance to the star:

D (distance) = V (recessional velocity) / H0 (Hubble’s constant)

This gives our published distance to Earendel of 12.9 billion light years! A staggering distance taking us back to the earliest period of star formation when the abundance of atomic elements in the universe was very different to today.

We believe the very first population of stars emerged around 100 to 250 million years after the big bang, so Earendel formed only a few hundred million yeas after this. The new James Webb telescope will likely continue to study Earendel in the infrared, at longer wavelengths, potentially revealing the star’s temperature and luminosity and therefore its stellar classification.

Einstein Goes To Hollywood

Join me at 7pm on Sunday the 31st January for a special live talk with Glasgow University’s Professor Martin Hendry – Professor of Gravitational Astrophysics and Cosmology.

Martin will be taking a light-hearted look at how ideas from Einstein’s theories have found their way into lots of the blockbuster movies we know and love. Plus a What’s Up guide to February skies from yours truly.

This event is brought to you by the Merkinch Nature Reserve Astronomy programme. It’s free and open to everyone but if you enjoy the session we would ask you to kindly donate using the provided links during the event stream.

The event will be broadcast live from my facebook page. Please use the following link to join the stream: https://fb.me/e/2hskXuAmx

2020 Perseids Meteor Shower

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Photo of a brilliant green meteor taken over southern India by biologist and photographer Prasenjeet Yadav.

The annual Perseids meteor shower is now underway with peak activity predicted from August 11th until August 13th.

The best times to view the shower will be after midnight when the Perseus radiant is rising higher in the East.  However, you don’t need to look at the radiant to see shooting stars as they’ll appear to come from all directions.

A waning crescent Moon will also rise during the three days of peak activity but its light shouldn’t overpower some of the brighter meteors the Perseids are known to produce.  You might also have some luck on the days after the 13th when the Moon’s influence will diminish (but overall meteor rates will be lower).

What Causes a Meteor Shower

Meteors are the fine dust and particulates left over from comets and large asteroids which stray into our solar system.  Some of these are on predictable orbits and as they whizz around the Sun they melt and shed some of this material into space.  The Earth then travels through these giant dust trails as it orbits the Sun, producing predictable meteor showers.  The Perseids are generated by Comet Swift-Tuttle, which has a 133 year orbit.

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Observing the Perseids

You don’t need any special equipment to view a meteor shower, in fact binoculars or telescopes will just narrow your field of view. Grab a deck chair or camping mat and (if it’s cold) a warm blanket, prepare a hot drink and lay out under the darkest conditions you can find. It’s an excellent activity to do alone, with family and friends, or if you have children they’ll love an excuse to get outside for some after dark play.

Put away any lights or bright mobile phone screens and simply look up and wait. Remember it takes up to 30 minutes for your eyes to fully dark adapt and any exposure to bright lights will start the process all over again. If you need a light, red LEDs or touches are best for preserving you night vision.

For optimal viewing, head out late at night or in the darkness of the pre dawn sky., when the radiant is highest in the sky.

Don’t Expect Too Much

You need to be patient with meteor showers.  Sometimes you’ll see many and other times very few or none at all.  Think of it as a great excuse to get out under the stars and breath in some fresh air.  Even if you don’t see much you probably won’t regret heading out and looking up.  Very rarely meteor showers can erupt into storms, like the Leonids in 1833 when over 100,000 shooting stars criss crossed the night sky1

Photographing the Perseids

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If your have a DSLR camera and tripod, or a suitable phone app like NightCap, you could try capturing some meteors with this rough guide.

  1. Firmly attach your camera or phone to the tripod.
  2. Disable autofocus and manually focus on some bright stars (make them as small and pin point as possible in your viewing screen)
  3. Set an ISO range somewhere between 1000-3000 depending on the capabilities of the sensor.  Mid 1000s is a good middle road.
  4. Turn off noise reduction or you’ll get big delays between each shot.
  5. Point your camera at a high and clear part of the sky.
  6. Shoot long exposures ranging from 10s to 30s, or simply use a remote shutter to take long manual exposures.  Note:  don’t go crazy with very long exposures or you’ll get amp glow from the sensor.
  7. Take lots and lots of shots and be patient!

If your camera has a time-lapse feature you can automate the shooting process and tell the camera to continually shoot 30 second exposures over a long interval.  Just watch out for dew forming on the lens if conditions are cold.  Some hand warmers stuffed into a sock wrapped around the lens will solve this particular issue.

Good luck and clear skies!

Highlands Astronomical Society Guest Talk

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An Island Universe – or ‘galaxy’ as we more commonly refer to these vast stellar structures.

I’m looking forward to delivering my guest talk on Island Universes for the Highlands Astronomical Society on Jan 7th. This is a repeat of a talk I presented at the 2019 Inverness Science Festival.

Start time is 7.15pm at the Smithton-Culloden Free Church, Murray Road, Smithton, IV2 7YU. Open to all members of the public and free entry for new visitors.

Please find full event details here.

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Geminids 2019

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Many thanks to Chris Cogan, a frequent contributor to my Facebook site, for sharing this spectacular Geminid fireball he caught up in Muie, Sutherland in the Scottish Highlands late on Saturday evening.

The facebook post created some interesting discussion, with several people claiming to have seen the same fireball as Chris.  This is very likely.  Last year when I kicked off the 2018 Star Stories programe we witnessed a similarly bright fireball flaring overhead.  By amazing coincidence Chris also photographed this one around 70 miles north of our position.  You can read about that encounter here.

This year’s Geminids appear to have been very active and despite an almost full Moon reports came in from people claiming to have sighted dozens over a reasonably short interval.  My wife I can testify to this after witnessing three in very quick succession after only 5 minutes viewing under light polluted skies.

The next meteor shower to look out for is the Quadrantids, peaking between the 3rd and 4th January 2020.

Milky Way Over Loch Morlich

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ISS cuts through the glowing band of the Milky Way, reflected in the waters of Loch Morlich in the Scottish Cairngorms

I enjoyed a pre equinox wild camp beside Loch Morlich last night. Amazing dark skies with the Milky Way bright enough to be faintly reflected on the loch’s surface.

Saturn and Jupiter shone in the early twilight before ISS made an appearance after 9pm, cutting through the bright band of the Milky Way.

Later still the Moon rose spectrally above the hills looking east, lighting up the loch like a beacon.

Happy equinox when it comes. Official time is Monday 23rd September at 8.50am.  Click below for more pictures.

 

2019 & 2020 Astronomy Programmes

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Exciting 2019/2020 astronomy programmes are coming together for Star Stories at Abriachan Forest and the Urban Astronomy evenings at the Merkinch Nature Reserve.

Both programmes kick off from 3rd and 5th October.  This year we’re aiming to invite both guest astronomers and storytellers to Abriachan, with author John Burns standing in for Clelland during a special dark sky Solstice event on the 21st December, for example.

Look out for a full list of event dates going up soon, with booking links for the first few.

First Urban Astronomy gathering:  Thursday 3rd October, Inverness

First Star Stories at Abriachan Forest:  Saturday 5th October, in collaboration with Highland Archaeology Festival.

Star Stories is in collaboration with Abriachan Forest Trust (A Dark Sky Discovery Site) with funding support from the Science and Technology Facilities Council.

The Urban Astronomy Evenings are in collaboration with Friends of Merkinch Nature Reserve.