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"Little Cub" gives astronomers rare chance to see galaxy demise

Last Updated on Tuesday, 04 July 2017 12:51
Published on Tuesday, 04 July 2017 10:12

A primitive galaxy that could provide clues about the early Universe has been spotted by astronomers as it begins to be consumed by a gigantic neighbouring galaxy. The Little Cub galaxy – so called because it sits in the Ursa Major or Great Bear constellation – is being stripped of the gas needed to continue forming stars by its larger companion. 

 

thumb Little-Cub-contoursA false colour image shows the grand design spiral galaxy NGC 3359, which is about 50 million light years from us. NGC 3359 appears to be devouring a much smaller gas rich dwarf galaxy, nicknamed the Little Cub, which contains 10,000 times fewer stars than its larger companion. The contours show where the gas is being stripped from the Little Cub, whose stars are located in the central blue circle. Credit: SDSS Collaboration. Click for a larger image

The find means scientists now have a rare opportunity to observe a dwarf galaxy as its gas is removed by the effects of a nearby giant galaxy to learn more about how this process happens. As the Little Cub has remained almost pristine since its formation, scientists also hope its elements will reveal more about the chemical signature of the Universe just minutes after the Big Bang.

 

The Little Cub and its larger neighbour, a grand design spiral galaxy called NGC 3359, are about 200 to 300 thousand light years apart, and approximately 50 million light years from Earth. Gas from the Little Cub is being stripped away by its interaction with NGC 3359, which has up to 10,000 times as many stars as the Little Cub and is similar to our Milky Way. By observing this cosmic feast, scientists hope to understand more about how and when gas is lost from smaller galaxies.

 

“We may be witnessing the quenching of a near-pristine galaxy as it makes its first passage about a Milky Way-like galaxy," said lead author Tiffany Hsyu, a graduate student in the Department of Astronomy & Astrophysics at UC Santa Cruz. 

 

“It is rare for such a tiny galaxy to still contain gas and be forming stars when it is in close proximity to a much larger galaxy so this is a great opportunity to see just how this process works.”

“Essentially the larger galaxy is removing the fuel that the Little Cub needs to form stars, which will eventually shut down star formation and lead to the smaller galaxy’s demise.”

 

The researchers also hope to gain an insight into the make-up of the very early Universe, by studying the hydrogen and helium atoms that are being illuminated by the small number of very bright stars within the Little Cub – which also has the less romantic name SDSS J1044+6306. Since this galaxy is so primitive, it may still preserve the hydrogen and helium atoms that were created minutes after the Big Bang.

 

Research co-author Dr Ryan Cooke, Royal Society University Research Fellow, in Durham University’s Centre for Extragalactic Astronomy, said: “We know by studying the chemistry of the Little Cub that it is one of the most primitive objects currently known in our cosmic neighbourhood.”

 

“Such galaxies, which have remained dormant for most of their lives, are believed to contain the chemical elements forged a few minutes after the Big Bang.”

“By measuring the relative number of hydrogen and helium atoms in the Little Cub we might be able to learn more about what made up the Universe in the moments after it began 13.7 billion years ago.”

 

The researchers hope further observations will find more pristine galaxies where the chemical signature of the early Universe might be found. The Little Cub was initially identified as a potentially pristine dwarf galaxy in data from the Sloan Digital Sky Survey (SDSS). Follow-up observations were conducted using the 3-metre Shane Telescope at Lick Observatory and the 10-metre telescope at the WM Keck Observatory.

 

"The Little Cub's discovery is a terrific example of using the smaller 3-metre-class Lick Observatory to scan through hundreds of candidates before focussing on the best sources with UC's 10-metre Keck telescope," said co-author J. Xavier Prochaska, Professor of Astronomy and Astrophysics at UC Santa Cruz.

 

A paper describing the discovery of Little Cub has been submitted for publication in the Astrophysical Journal Letters. The research was funded by the WM Keck Foundation, Google, The Royal Society, NASA, the Science and Technology Facilities Council and the National Science Foundation (USA).

 

The Royal Astronomical Society’s National Astronomy Meeting is taking place at the University of Hull, UK, until Thursday, 6 July, 2017.

 


Media contacts

 

NAM press office (Monday 3 – Thursday 6 July)

Tel: +44 (0)1482 467507 / (0)1482 467508

 

Robert Massey

Royal Astronomical Society

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Anita Heward

Royal Astronomical Society

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Morgan Hollis

Royal Astronomical Society

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Science contacts

 

Dr Ryan Cooke, Royal Society University Research Fellow, in Durham University’s Centre for Extragalactic Astronomy, is available for interview on Monday, 3 July, before 1pm, and Tuesday July 4, noon until 4pm, via video call or telephone.

Dr Cooke can be contacted on +44 (0)7852 738 689or This email address is being protected from spambots. You need JavaScript enabled to view it. .

Alternatively please contact Durham University Marketing and Communications Team on +44 (0)191 334 6075; This email address is being protected from spambots. You need JavaScript enabled to view it.

 

Tiffany Hsyu, graduate student in the Department of Astronomy & Astrophysics at UC Santa Cruz, USA, is also available for interview at +1 (831) 459 3259; This email address is being protected from spambots. You need JavaScript enabled to view it. .

Alternatively please contact Ilse Ungeheuer, Communications Specialist, UC Observatories, +1 (831) 459 2201 or This email address is being protected from spambots. You need JavaScript enabled to view it. .

 


Images and captions

 

A false colour image shows the grand design spiral galaxy NGC 3359, which is about 50 million light years from us. NGC 3359 appears to be devouring a much smaller gas rich dwarf galaxy, nicknamed the Little Cub, which contains 10,000 times fewer stars than its larger companion. The contours show where the gas is being stripped from the Little Cub, whose stars are located in the central blue circle. Credit: SDSS Collaboration.

 

Zoom in of the Little Cub galaxy, a star-forming dwarf galaxy that is being stripped of gas by its gigantic neighbouring galaxy. Image credit: SDSS Collaboration.

Pictures are available on request from Durham University Marketing and Communications Team on +44 (0)191 334 6075; This email address is being protected from spambots. You need JavaScript enabled to view it.

 


Further information

 

The new work appears in “The Little Cub: Discovery of an extremely metal-poor star-forming galaxy in the local universe”, T. Hsyu et al. A copy of this paper is available from Durham University Marketing and Communications Office on +44 (0)191 334 6075; This email address is being protected from spambots. You need JavaScript enabled to view it.

 

Dr Ryan Cooke staff profile: www.dur.ac.uk/research/directory/staff/?mode=staff&id=15675

 

Centre for Extragalactic Astronomy, Durham University: http://astro.dur.ac.uk/

 

Tiffany Hsyu profile: https://www.astro.ucsc.edu/faculty/profiles/singleton.php?&singleton=true&cruz_id=thsyu

 

Astronomy & Astrophysics at UC Santa Cruz: https://www.astro.ucsc.edu/index.html

 

National Astronomy Meeting 2017: https://nam2017.org/

 


Notes for editors

 

Running from 2 to 7 July, the RAS National Astronomy Meeting 2017 (NAM 2017, http://nam2017.org) takes place this year at the University of Hull. NAM 2017 will bring together around 500 space scientists and astronomers to discuss the latest research in their respective fields. The conference is principally sponsored by the Royal Astronomical Society and the Science and Technology Facilities Council.

T: http://twitter.com/rasnam2017

 

The Royal Astronomical Society (RAS, www.ras.org.uk), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organises scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 4000 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

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The Science and Technology Facilities Council (STFC, www.stfc.ac.uk) is keeping the UK at the forefront of international science and has a broad science portfolio and works with the academic and industrial communities to share its expertise in materials science, space and ground-based astronomy technologies, laser science, microelectronics, wafer scale manufacturing, particle and nuclear physics, alternative energy production, radio communications and radar.

STFC's Astronomy and Space Science programme provides support for a wide range of facilities, research groups and individuals in order to investigate some of the highest priority questions in astrophysics, cosmology and solar system science. STFC's astronomy and space science programme is delivered through grant funding for research activities, and also through support of technical activities at STFC's UK Astronomy Technology Centre and RAL Space at the Rutherford Appleton Laboratory. STFC also supports UK astronomy through the international European Southern Observatory.

T: https://twitter.com/stfc_matters

 

Durham University is a world top 100 university with a global reputation and performance in research and education (QS 2018 and THE World University Rankings 2016/17) (https://www.dur.ac.uk/about/rankings). In the Guardian University Guide 2018 and the 2017 Times and Sunday Times Good University Guide, Durham was ranked fourth in the UK, and is a member of the Russell Group of leading research-intensive UK universities. Research at Durham shapes local, national and international agendas, and directly informs the teaching of our students, and it is ranked 34 globally for the employability of its students by blue-chip companies world-wide (QS World University Rankings 2018).