Astrosat Picture of the Month

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Image of the Month

The AstroSat Picture of the Month for October 2017 shows us newly formed star clusters in the dwarf galaxy Wolf-Lundmark-Melotte (WLM), imaged by the Ultra Violet Imaging Telescope on board the ASTROSAT.

(Picture Credits: Annapurni Subramaniam)

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“AstroSat Picture of the Month” is an initiative of the Public Outreach and Education Committee of the Astronomical Society of India and the AstroSat Training and Outreach Team.

WLM: a dwarf galaxy, efficiently forming stars in grand isolation

Located in the constellation Cetus, 3 million light years away, is a faint dwarf galaxy,Wolf-Lundmark-Melotte, or WLM for short. It is relatively isolated, lying in the outskirts of our Local Group of Galaxies. It has a mass that is thousands of times less than the Milky Way and a metallicity that is only 13% solar. Lower metallicity implies less heavier elements, which in turn hinders forming new stars. So why did AstroSat even look at this galaxy?

WLM is a dwarf irregular galaxy with a low mass and metallicity and exists in solitude. Nevertheless, it manages to form new stars extremely efficiently. Adjusted for their respective masses, WLM forms stars at a rate that is 12 times higher than our own Milky Way! Astronomers are still not sure as to how WLM does this.

Annapurni Subramaniam and her student Chayan Mondal at the Indian Institute of Astrophysics in Bengaluru wanted to understand how this diminutive galaxy is such an efficient star factory. They decided to use the Ultra Violet Imaging Telescope on board the AstroSat to image the younger star clusters in WLM. In this image, the blue dots are the star clusters imaged in Far Ultra-Violet (130-180 nm) and the yellow dots are those imaged in Near Ultra-Violet (180-300 nm). They are currently analysing this data and will soon be able to fit one more piece into the puzzle that is WLM.


AstroSat, India's first dedicated multi-wavelength space observatory, was launched by ISRO on 28 September, 2015. It has five instruments on board – the Ultra Violet Imaging Telescope, the Soft X-ray Telescope, the Large Area X-ray Proportional Counter, the Cadmium-Zinc-Telluride Imager and the Scanning Sky Monitor.

Get answers to your common queries about ASTROSAT in English, in हिंदी, and in मराठी.


  1. Pale Blue Dot (EARTH): Look again at that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every “superstar,” every “supreme leader,” every saint and sinner in the history of our species lived there-on a mote of dust suspended in a sunbeam.

    The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds.

    Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves.

    The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.

    It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we’ve ever known.


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